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Cristina LUCCHETTI

Ricercatore Universitario
Dipartimento di Scienze Biomediche, Metaboliche e Neuroscienze sede ex-Sc. Biomediche

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Pubblicazioni

2023 - Long and short whiskers differently guide snout/pellet interaction in rat oral grasping [Articolo su rivista]
Parmiani, P.; Lucchetti, C.; Viaro, R.; Franchi, G.
abstract

We studied the role of rat whisker/snout tactile sense during oral grasping, comparing control data with those obtained, respectively, 1-3 and 5-7 days after bilateral long or short whisker trimming and 3-5 and 8-10 days after bilateral infraorbital nerve (ION) severing. Two behavioural phases were identified: whisker-snout contact by nose-N or lip-L and snout-tongue contact. The second phase involved either: snout passing over stationary pellet (Still pellet); pellet rolling as the snout passed over it (Rolling pellet); pellet being pushed forward by the snout (Pushed pellet); or pellet being hit and pushed away (Hit/Lost pellet). In controls, success was 100%, with N-contact prevailing over L-contact in the first phase and Still pellet in the second. In long whisker-trimmed versus controls, success was still 100%, but L-contact increased in frequency, Pushed pellet prevailed and the second phase duration increased. In short whisker-trimmed versus controls, success remained 100%, with increased L-contact frequency; the first phase duration did not change, but the second phase increased since in pushed trials, the pellet rolled around the snout. In ION-severed versus controls, both phases changed drastically: L-contact frequency increased, Pushed pellet prevailed and contact was persistently maintained; Hit/Lost pellet emerged, Still and Rolling pellets disappeared and the oral-grasping sequence was not triggered. These results suggest that long and short whiskers, respectively, optimize the first and second phases of snout-pellet interaction and that whisker/snout sense is necessary to trigger oral grasping. Kinematic trajectory analysis supports the conclusion that movement from whisker to snout contact is an orientation response.

2021 - Changes in reach-to-grasp behaviour over the course of training in rats [Articolo su rivista]
Parmiani, P.; Lucchetti, C.; Franchi, G.
abstract

One complex task involving sequence of movements and movement refinement in the rat is the single-pellet reaching task, comprising orientation, transport and withdrawal in sequence. In turn, orientation comprises front wall detection, slot localization and nose poke until reach start. Video recordings of a rat in the reaching box highlighted three stages of temporal training: start of training (ST), forepaw dominance appearance (D) and fully trained (T). Regarding orientation, ST versus D and T presented a significant smaller frequency of approach to the front wall and a significant higher number of whisker cycles and nose touches during slot localization, involving a significant longer Orientation. At the ST stage, 44% of the trials were interrupted after nose poke, and poke took place at significant higher level from the shelf. The shelf was identified only when short whiskers contacted it, but the tongue and both forepaws were used without distinction to reach and grasp the pellet until a forepaw emerged as dominant at D stage. Regarding the temporal features of transport and withdrawal, comparing the D versus T stage revealed a significant longer duration. Finally, successes were significantly higher in T respect to D, meaning that after dominance emergence, more training was still necessary to improve reaching/grasping performance. This study provides evidence that, during training, the rats develop a strategy to obtain the pellets and then refine their movement pattern.

2021 - The effects of olfactory bulb removal on single-pellet skilled reaching task in rats [Articolo su rivista]
Parmiani, P.; Lucchetti, C.; Franchi, G.
abstract

We focused on how the rat uses olfactory cues in a single-pellet reaching task, which is composed of three successive learned responses, Orient, Transport, and Withdrawal. Orient comprised: front wall detection, slot localisation, and nose poke until reach start. High-speed video-recording enabled us to describe the temporal features of this sequence in controls vs. 3–5 and 12–14 days after bilateral bulbectomy in trials with (P trial) vs. without (no-P trial) pellet. In controls, the full sequence was complete in P trials, while it was interrupted after Orient in no P-trials. After bulbectomy, the full sequence was seen in both P and no-P trials at days 3–5 and 12–14 and there was an increase in Orient duration due to the increased time in slot/shelf localisation. Unlike in controls, in anosmic rats, the first nose contact with the front wall took place below the slot/shelf level, and the number of nose touches together with the number of whisker cycles was significantly higher at 3–5 but not at 12–14 days. The relationship between nose touches and whisker cycles was linear in all experimental conditions. Bulbectomy resulted in no changes in the Transport duration or the time the paw spent out of the slot. These findings suggest that olfaction allows the animal to orient itself in pellet localisation, and offers insight into the contribution of olfaction during different stages of natural behaviour in skilled reaching task.

2019 - A kinematic study of skilled reaching movement in rat [Articolo su rivista]
Parmiani, Pierantonio; Lucchetti, Cristina; Bonifazzi, Claudio; Franchi, Gianfranco
abstract

Abstract BACKGROUND: In the rat, the single-pellet reaching task includes orienting, reaching, grasping and retracting movements. It has previously been described by notation techniques, high-speed video and cineradiographic recordings. Recently, high-definition cameras have been used to track paw and digit movements with DeepLabCut, a machine-learning algorithm for markerless estimation of paw position. NEW METHOD: Our new approach consists of positioning three high-speed infrared digital cameras to track the full motion of markers on the rat's body. This provided a previously unavailable 3D recording of skilled reaching kinematics in the rat moving freely in the reaching box, which were analysed by Qualisys Track Manager software and MATLAB. RESULTS: This method enabled description of kinematic parameters unobtainable without motion tracking and provided insight into the spatiotemporal metrics of movements used to perform skilled reaching. It revealed that orientation features three steps and reaching has two bimodal start-point distributions, one along the horizontal axis and one along the vertical axis. At the end of reaching, the wrist/paw occupies the same position as the nose at the end of orienting. In grasping, averaging trajectories confirmed the marker lowering and target approaching. COMPARISON WITH EXISTING METHODS: Our method required significantly reduced time to label data and obviates the need for off-line manual marking of videos. It provides an efficient means of capturing volumes containing the entire range of marker movements. CONCLUSIONS: This study validated a new and efficient approach for quantifying rat movement kinematics, useful for comparing preclinical and clinical conditions.

2018 - Whisker and Nose Tactile Sense Guide Rat Behavior in a Skilled Reaching Task. [Articolo su rivista]
Parmiani, P; Lucchetti, C; Franchi, G.
abstract

Skilled reaching is a complex movement in which a forelimb is extended to grasp food for eating. Video-recordings analysis of control rats enables us to distinguish several components of skilled reaching: Orient, approaching the front wall of the reaching box and poking the nose into the slot to locate the food pellet; Transport, advancing the forelimb through the slot to reach-grasp the pellet; and Withdrawal of the grasped food to eat. Although food location and skilled reaching is guided by olfaction, the importance of whisker/nose tactile sense in rats suggests that this too could play a role in reaching behavior. To test this hypothesis, we studied skilled reaching in rats trained in a single-pellet reaching task before and after bilateral whisker trimming and bilateral infraorbital nerve (ION) severing. During the task, bilaterally trimmed rats showed impaired Orient with respect to controls. Specifically, they detected the presence of the wall by hitting it with their nose (rather than their whiskers), and then located the slot through repetitive nose touches. The number of nose touches preceding poking was significantly higher in comparison to controls. On the other hand, macrovibrissae trimming resulted in no change in reaching/grasping or withdrawal components of skilled reaching. Bilaterally ION-severed rats, displayed a marked change in the structure of their skilled reaching. With respect to controls, in ION-severed rats: (a) approaches to the front wall were significantly reduced at 3-5 and 6-8 days; (b) nose pokes were significantly reduced at 3-5 days, and the slot was only located after many repetitive nose touches; (c) the reaching-grasping-retracting movement never appeared at 3-5 days; (d) explorative paw movements, equal to zero in controls, reached significance at 9-11 days; and (e) the restored reaching-grasping-retracting sequence was globally slower than in controls, but the success rate was the same. These findings strongly indicate that whisker trimming affected Orient, but not the reaching-grasping movement, while ION severing impaired both Orient (persistently) and reaching-grasping-retracting (transiently, for 1-2 weeks) components of skilled reaching in rats.

2017 - Neuronal Encoding of Self and Others' Head Rotation in the Macaque Dorsal Prefrontal Cortex. [Articolo su rivista]
Lanzilotto, Marco; Gerbella, Marzio; Perciavalle, Vincenzo; Lucchetti, Cristina
abstract

Following gaze is a crucial skill, in primates, for understanding where and at what others are looking, and often requires head rotation. The neural basis underlying head rotation are deemed to overlap with the parieto-frontal attention/gaze-shift network. Here, we show that a set of neurons in monkey's Brodmann area 9/46dr (BA 9/46dr), which is involved in orienting processes and joint attention, becomes active during self head rotation and that the activity of these neurons cannot be accounted for by saccade-related activity (head-rotation neurons). Another set of BA 9/46dr neurons encodes head rotation performed by an observed agent facing the monkey (visually triggered neurons). Among these latter neurons, almost half exhibit the intriguing property of encoding both execution and observation of head rotation (mirror-like neurons). Finally, by means of neuronal tracing techniques, we showed that BA 9/46dr takes part into two distinct networks: a dorso/mesial network, playing a role in spatial head/gaze orientation, and a ventrolateral network, likely involved in processing social stimuli and mirroring others' head. The overall results of this study provide a new, comprehensive picture of the role of BA 9/46dr in encoding self and others' head rotation, likely playing a role in head-following behaviors.

2015 - Evidence for a functional subdivision of Premotor Ear-Eye Field (Aera 8B) [Articolo su rivista]
Lanzilotto, Marco; Perciavalle, Vincenzo; Lucchetti, Cristina
abstract

The Supplementary EyeField (SEF) and the Frontal Eye Field (FEF) have been described as participating in gaze shift control. Recent evidence suggests, however, that other areas of the dorso medial prefrontal cortex also influence gaze shift. Herein, we haveinvestigated electrically evoked ear-and eye movements from the PremotorEar-Eye Field, or PEEF (area8B) of macaque monkeys. We stimulated PEEF during spontaneous condition (outside the task performance) and during the execution of a visual fixation task(VFT). In the first case, we functionally identified two regions within the PEEF: a core and a belt. In the core region, stimulation elicited forward ear movements; regarding the evoked eye movements, in some penetrations, stimulation elicited contraversive fixed-vectors with a mean amplitude of 5.14◦; while in other penetrations, we observed prevalently contralateral goal-directed eye movements having end-points that fell within15◦ inrespect to the primary eye position. On the contrary, in the belt region,stimulation elicited backward ear movements; regarding the eye movements, in some penetrations stimulation elicited prevalently contralateral goal-directed eye movements having end-points that fell within 15◦ in respect to the primary eye position, while in the lateral edge of the investigated region, stimulation elicited contralateral goal-directedey emovements having end-points that fell beyond 15◦in respect to the primary eye position. Stimulation during VFT either did not elicit eye movements or evoked saccades of only a few degrees. Finally, even though no head rotation movements were observed during the stimulation period, we viewed a relationship between the duration of stimulation and the neck forces exerted by the monkey’shead. We propose an updated vision of the PEEF composed of two functional regions, core and belt, which may beinvolved in integrating auditory and visual information important to the programming of gaze orienting movements.

2015 - Orienting movements in area 9 identified by long-train ICMS [Articolo su rivista]
Lanzilotto, Marco; Perciavalle, V; Lucchetti, Cristina
abstract

The effect of intracortical microstimulation has been studied in several cortical areas from motor to sensory areas. The frontal pole has received particular attention, and several microstimulation studies have been conducted in the frontal eye field, supplementary eye field, and the premotor ear-eye field, but no microstimulation studies concerning area 9 are currently available in the literature. In the present study, to fill up this gap, electrical microstimulation was applied to area 9 in two macaque monkeys using long-train pulses of 500-700-800 and 1,000 ms, during two different experimental conditions: a spontaneous condition, while the animals were not actively fixating on a visual target, and during a visual fixation task. In these experiments, we identified backward ear movements, goal-directed eye movements, and the development of head forces. Kinematic parameters for ear and eye movements overlapped in the spontaneous condition, but they were different during the visual fixation task. In this condition, ear and eye kinematics have an opposite behavior: movement amplitude, duration, and maximal and mean velocities increase during a visual fixation task for the ear, while they decrease for the eye. Therefore, a top-down visual attention engagement could modify the kinematic parameters for these two effectors. Stimulation with the longest train durations, i.e., 800/1,000 ms, evokes not only the highest eye amplitude, but also a significant development of head forces. In this research article, we propose a new vision of the frontal oculomotor fields, speculating a role for area 9 in the control of goal-directed orienting behaviors and gaze shift control.

2013 - A new field in monkey's frontal cortex: premotor ear-eye field (PEEF) [Articolo su rivista]
Lanzilotto, Marco; Perciavalle, V; Lucchetti, Cristina
abstract

In macaque monkey, area 8B is cytoarchitectonically considered a transitional area between the granular Brodmann area 9, rostrally, and the rostral part of the dorsal agranular Brodmann area 6, caudally. As for electrophysiological data, microstimulation of area 8B evokes ear and/or eye movements; unit activity recording shows neurons encoding different auditory environmental stimuli and ear and/or eye movements. Moreover, visual attentive fixation modulates the discharge of auditory environmental neurons and auditory-motor neurons. As for anatomical data, area 8B is connected with auditory cortical areas, superior colliculus and cerebellum. Current functional and anatomical evidences support that area 8B is a specific Premotor Ear-Eye Field (PEEF) involved in auditory stimuli recognition and in orienting processes. In conclusion, we suggest that PEEF could play an important role in engaging the auditory spatial attention for the purpose of orienting eye and ear towards the sound source.

2013 - Auditory and visual systems organization in Brodmann Area 8 for gaze-shift control: where we do not see, we can hear [Articolo su rivista]
Lanzilotto, Marco; Perciavalle, Vincenzo; Lucchetti, Cristina
abstract

Hearing is especially important for most primate species as they live in habitats of dense vegetation that limits vision. Stebbins (1980) summed up the evolution of the auditory system by assuming that earliest mammals exploited nocturnal niches since they were relatively free of many of the large, diurnal, predacious reptiles. Therefore, hearing and smell were more useful at night than vision. Our vision is limited not only in the dark but also outside the visual field. In fact, if we observe the behavior of a predator like a feline, oriented toward its prey, and at the same time a sound occurs behind, we might note three principal different behaviors: the predator could maintain its gaze and ears on the prey neglecting the sound source; the predator could maintain its gaze on the prey rotating ears and then shifting its auditory attention toward the sound source; finally the predator could break its attention and orient gaze and ears toward the sound source. A similar behavior is seen in human beings during social interaction with two or more interlocutors. In humans, orienting movements are carried out by the eyes, head, and/or body operating alone or in various combinations depending on the behavioral situation. However, in non-human primates, such as macaque monkeys, head orienting movements and, more generally, gaze-shift are accompanied by ear orienting movements, which allow the shifting of auditory attention toward a sound of interest (Bon and Lucchetti, 1994, 2006; Lucchetti et al., 2008; Lanzilotto et al., 2013; Yin, 2013). Considering all these assumptions, the auditory system could have an important role to detect information even from regions of the space that the visual system cannot explore without orienting movements. In other words, where we cannot see, we can hear. Through this opinion article, we argue that Brodmann Area 8 receives information from both auditory and visual systems and organizes a transformation of these sensory signals into gaze-shift motor commands. Our hypothesis is that this sensory-motor transformation is spatially organized, from both anatomical and functional points of view. Anatomical and functional properties of the Brodmann Area 8 (consisting in Area 8A plus Area 8B) support a medio-lateral organization for both auditory and visual systems. In particular, the lateral portion, corresponding to Area 8A or Frontal Eye Field (FEF), could play a role in receiving visual and auditory information from a central part of the visual field and then in organizing gaze-shift motor commands toward it. Otherwise, the medial portion, corresponding to Area 8B or Premotor Ear-Eye Field (PEEF), could play a role in receiving principally auditory information from a peripheral region of the space and then in organizing gaze-shift motor commands toward it.

2012 - Neuronal activity reflecting progression of trials in the pre-supplementary motor area of Macaque monkey: an expression of neuronal flexibility. [Articolo su rivista]
Lucchetti, Cristina; Lanzilotto, Marco; V., Perciavalle; L., Bon
abstract

AbstractWe studied the activity of single neurons in the pre-supplementary motor area(pre-SMA) of macaque monkeys as they performed two visuomotor tasks, called thevisual fixation task and the visual fixation-blink task. Both tasks involved asequence of three visual stimuli, red followed by yellow and green. The tasksdiffered in that the latter one had a gap within the period of the red stimulus,called a "blink". The tasks were performed in two modes, one of which includedmovements of both the arm and eye and the other of which involved only eyemovements. In the arm-eye mode, the monkeys had to press a bar and fixate the redstimulus that appeared after bar press. To receive a reward, both the bar press andvisual fixation had to be maintained until the green stimulus triggered bar release.In the eye mode, bar press and bar release were eliminated from the task. Of the 42neurons active during the visual fixation task, 15 showed task-related activity inboth arm-eye and eye modes, and our analysis focused on these cells. We found thatthe introduction of the blink in visual fixation-blink task abolished thetask-related activity of these cells over the course of 2-4 trials. This findingsuggests a role for the pre-SMA in reflecting progression of trials as an updatingof motor instruction.

2012 - The neural correlates of social communication: role of PEEF in auditory orienting. [Poster]
Lanzilotto, Marco; Bon, Leopoldo; V., Perciavalle; Lucchetti, Cristina
abstract

Hypothesis as for auditory system hierarchical organization suggest the same organization of visual system. Anatomical and physiological data propose auditory system consisting of two streams, dorsal and ventral, which project together to the frontal lobe. The dorsal one brings auditory spatial information while the ventral one brings information as for the sound recognition. Considering both anatomical and electrophysiological evidence we propose that in dorsolateral frontal cortex there is an integration of both auditory streams. In fact, previous electrophysiological investigations support the anatomical data showing how in PEEF (area 8B) there are different kind of auditory or auditory motor neurons: neurons firing for the integration of auditory complex stimuli and eye and/or ear movements, pure auditory neurons firing for experimenters' voice, pure auditory neurons firing for sound's spatial direction. Here, we present preliminary data supporting the hypothesis that PEEF plays an important role as link between the auditory and motor system. We show a population of neurons firing for animals' and species-specific vocalizations and for head motor control. We propose PEEF as an important node for gaze and attentional shift toward auditory stimuli.

2009 - NEGLECT SINDROME FOR AVERSIVE AND PLEASANT STIMULI IN A MACAQUE MONKEY WITH PEEF LESION. [Abstract in Rivista]
G., Croazzo; Lanzilotto, Marco; Bon, Leopoldo; V., Perciavalle; V., Terlizzi; Lucchetti, Cristina
abstract

Aim: The Premotor Ear-Eye Field (PEEF), rostral to dorsal premotor cortex is involved in auditory perception and in ear-eye attentional orienting processes. In this work we describe the attentional deficits provoked by an electrolytic lesion in the PEEF.Methods: A macaque monkey was previously trained for three oculomotor tasks: Fixation task, Saccade task, Peripheral attention task. After unit activity recording, we made an electrolytic lesion using direct corrent (15 mA for 20 s), accidentally provoking an epileptic attack. During the epileptic attack, we observed rapid movements of both pinnae and a rhythmic contralateral tilting of the head, trunk and arm.Results: The animal was able to execute the oculomotor tasks as well as before the epileptic attack. Moreover we observed that the animal showed a neglect only for aversive stimuli with the head free. When the head was fixed this neglect desappered. In addition, the extinction phenomenon appeared for both aversive and pleasant stimuli and in both experimental conditions: free head and fixed head.Conclusion: These data firstly confirm that the PEEF is involved in attentional processes and secondly suggest that attentional behaviour is influenced by head condition. In addition, this last point suggests an additional role of PEEF in head movement control and also it is in favour of the double control system one for the head and one for the eye.

2009 - PEEF: Premotor Ear-Eye Field. A New Vista of Area 8B [Capitolo/Saggio]
Bon, Leopoldo; Lanzilotto, Marco; Lucchetti, Cristina
abstract

In macaque monkeys, area 8B may be considered cytoarchitectonically as atransitional area between the granular area 9, rostrally, and the rostral part of the dorsalagranular area 6 (FC or F7), caudally. This area is anatomically connected with auditorycortical areas, cerebellum and superior colliculus. Microstimulation of area 8B evokesear movements or eye movements in some sites; in other sites, it evokes both ear and eyemovements by varying the intensity of electric stimulation. Unit activity recording showsthat neurons in area 8B have a role in encoding different auditory environmental stimuliand movements of the ear and eye. In addition, fixation of a visual stimulus, whenattention is engaged, modulates the discharge of auditory environmental neurons, andsensory-motor neurons.Current functional and anatomical evidences strongly support the proposal that area8B is a specific Premotor Ear-Eye Field (PEEF) involved in the recognition of auditorystimuli and in orienting processes. Moreover, activation by specific environmentalauditory stimuli, suggests that PEEF is an important node in the hierarchical organisationof the auditory network. The inhibitory effects on neural discharge of auditory andauditory-motor cells might be a consequence of the engagement of attention duringvisual fixation. This phenomenon may be the expression of a combination of a covertorienting of attention relative to eye effectors, and an overt orienting of attention relativeto ear effectors. It seems that attention may affect more than one channel at the same timeduring a conditioned task or during natural behaviour. Then the PEEF, based on itsconnections and functional characteristics may be involved in three circuits: 1) anauditory circuit, 2) an oculomotor circuit, 3) and a fronto-cerebellar circuit.

2008 - Auditory-motor and cognitive aspects in area 8B of macaque monkey's frontal cortex: a premotor ear-eye field (PEEF) [Articolo su rivista]
Lucchetti, Cristina; M., Lanzilotto; Bon, Leopoldo
abstract

In previous reports, we showed the involvement of area 8B neurons in both spontaneous ear and eye movement and in auditory information processing. Audition-related cells responded to complex environmental stimuli, but not to pure tones, and their activity changed during visual fixation as a possible inhibitory expression of the engagement of attention. We observed auditory, auditory-motor and motor cells for both eye and ear movements. This finding suggests that area 8B may be involved in the integration of auditory input with ear and eye motor output. In this paper, we extended these previous studies by examining area 8B activity in relation to auditive orienting behaviour, as well as the ocular orientation (i.e., visual fixation) studied previously. Visual fixation led to inhibition of activity in auditory and auditory-motor cells, which suggests that attention may be involved in both, maintaining the eye position and reducing the response of these cell types. Accordingly, during a given task or natural behaviour, spatial attention seems to affect more than one sensorimotor channel simultaneously. These data add to our understanding of how the neural network, through a two-channel attentive process, accomplishes to switch between two effectors, namely eyes and ears. Considering the functional, anatomical and cytoarchitectonic differences among the frontal eye field (FEF), the supplementary eye field (SEF) and area 8B, we propose to consider area 8B as a separate premotor ear-eye field (PEEF).

2008 - MAY THE WARNING AUDITORY-VISUAL NEURONS HELP THE MONKEY TO PLAY THE PIANO? [Abstract in Rivista]
Lanzilotto, Marco; Oliveti, D; Bon, Leopoldo; Lucchetti, Cristina
abstract

Aim: In previous reports, we showed the involvement of PEEF (area 8B) neurons in auditory information processing and in ear and eye orienting behaviour. For what concerns auditory cells, we observed, by unit activity recording, that their activity was related to complex environmental auditory stimuli but not to pure tones. Our question was: if we train intensively a monkey, much more than previous animals, to receive the reward only after having listened to a particular note, may the monkey's neurons discriminate different notes?Methods: For this aim, we trained intensively a Macaque monkey to receive some drops of fruit juice only after having listened to a particular note (FA), while it did not receive the reward after the presentation of a different note (DO). Moreover, during the experiments also the note SOL was presented without reward. The animal was also trained for a classic visual fixation task.Results: We recorded two types of cells: a) classic auditory environmental neurons and b) neurons that discharged for FA and SOL notes but not for DO note. The discharge was brisk for the FA note, it was less intensive with a rapid adaptation for the SOL note and very weak for the DO note. In addition the discharge was scarce for the clik of the pump, and active during visual fixation task before the clik of the pump.Conclusion: Present data confirm the role of the PEEF in auditory-visual integration and expand the vision of this field. The presence of cross modal neurons (auditory-visual) and the ability to discriminate between different notes suggest to speculate that this field may be involved in music learning.

2007 - Conceptual mirror neurons in monkey’s pre-supplementary motor area [Abstract in Rivista]
Lanzilotto, Marco; Bon, Leopoldo; Lucchetti, Cristina
abstract

Aim: mirror neurons are present in many areas of human and monkey brain. They are considered as the common substrate for action and perception. These neurons seem also to predict the goal of the observed action as if they had an internal representation of what is going on. To verify if a conditioned visuo-motor task my create in monkey's brain a mental representation, we recorded premotor neurons of a macaque monkey' frontal cortex.

2007 - Sensory-motor and cognitive aspects of the prefrontal cortex as part of cerebellar network [Abstract in Rivista]
Bon, Leopoldo; Lanzilotto, Marco; Lucchetti, Cristina
abstract

Aim: anatomical investigation showed connections between prefrontal cortex area 9 and cerebellum. The caudal part of area 9 is also called area 8B. Area 9 and area 8B are connected also with auditory-association cortex. previous unit activity recording and microstimulation experiments showed that area 8B is involved in ear-eye motor control. The aim of the present invastigation was to show, by unit activity recording, the role of area 8B in auditory motor integration and the role of the engagement of attention during visual fixation in auditory-motor processes.

2006 - Auditory environmental cells and visual fixation effect in area 8B of macaque monkey [Articolo su rivista]
Bon, Leopoldo; Lucchetti, Cristina
abstract

Area 8B may be treated as part of either the prefrontal cortex or the premotor cortex. Previous investigations showed an involvement of area 8B in both eye and ear motor control and in auditory perception. In this report, we Studied 139 neurons in three macaque monkeys of these., 32 neurons showed an activity related to environmental auditory stimuli. Fifteen cells with auditory characteristics (15/32) presented a firing discharge inhibited during the execution Of Visual fixation. The remaining 107 units presented complex or indefinable behaviour. The presence of auditory environmental cells which activity is related prevalently to the voice of persons (researchers) suggests that area 8B may be an area involved in auditory cross-modal association, in natural behaviour. The inhibitory effects during Visual fixation suggest that area 8B is part of the inhibitory network preventing the gaze shift in relation to ail auditory Stimulus. This may be the consequence of the engagement of attention during fixation that may affect the auditory perception. Both aspects indicate that area 8B is involved in high cognitive processes in auditory and orienting processes.

2006 - The involvement of area 8B in a switching system to control eye and ear orienting processes in Macaca monkey [Abstract in Rivista]
Lucchetti, Cristina; Lanzilotto, Marco; Oliveti, D; Bon, Leopoldo
abstract

Aim: the purpose of this study was to investigate unit activity of area 8B, rostral to the dorsal premotor cortex, in relation to different environmental acoustic stimuli and the effect of the engagement of attention during visual fixation.

2005 - Dorsal premotor areas of nonhuman primate: functional flexibility in time domain [Articolo su rivista]
Lucchetti, Cristina; Ulrici, Alessandro; Bon, Leopoldo
abstract

A voluntary motor act requires recognition of the informational content of an instruction. An instruction may contain spatial and temporal information. The recently proved role of the monkey frontal cortex in time computation, as well as in motor preparation and motor learning, suggested that we investigate the relationship between premotor neuron discharges and the temporal feature of the visual instructions. To this purpose, we manipulated the duration of an instructional cue in a visuomotor task while recording unit activity. We found two types of premotor neurons characterised by a discharge varying in relation to the duration of the cue: (1) "motor-linked" neurons, with a specific premotor activity constantly bounded to the motor act; (2) "short-term encoders" neurons, with a premotor activity depending on the cue duration. The cue duration was the critical factor in determining the behaviour of the short-term encoders cells: when the cue ranged from 0.5 s to I s, they presented a preparatory activity: when the cue was longer, up to 2 s, they lost cells anticipated their discharge. The activity changed in few trials. These data confirm and highlight the role of frontal cortex in encoding specific cues with a temporal flexibility, which may be the expression of temporal learning and represent an extended aspect of cortical plasticity in time domain.

2002 - MUPRO: A multipurpose robot [Articolo su rivista]
Bon, Leopoldo; Lucchetti, Cristina; Portolan, Flavio; Pagan, Mauro
abstract

The aim of this article was to describe an apparatus, called multipurpose neck robot (MUPRO), designed to record both the forces exerted at head level and the head rotations in the horizontal plane in the behaving monkey. It consists of a mechanical device, comprising a cardan joint, a potentiometer, an electromagnetic brake, and four flexion load cells, plus an oleodynamic system allowing head rotation in the horizontal plane between +/-20degrees. There components are assembled on a column bolted to the primate's chair. An electrical device provides DC power for the potentiometer and the brake. The apparatus enables us to measure both the force fields and the head movements during training sessions and electrophysiological investigations.

2001 - Time-modulated neuronal activity in the premotor cortex of macaque monkeys [Articolo su rivista]
Lucchetti, Cristina; Bon, Leopoldo
abstract

A voluntary motor act, executed in response to a stimulus, requires both spatial and temporal computation. Even though electrophysiological and positron emission tomography (PET) investigations on humans suggest that SMA, medial prefrontal cortex and primary motor cortex play a role in temporal mechanisms, we have few data about neuronal time computation in the premotor cortex. The involvement of monkey premotor area (PM) in motor learning and cognitive processes, and the presence of buildup neurons, whose activity is closely related to the motor action, prompted us to investigate the involvement of these set-related neurons in the time domain. To this end we manipulated the duration of a pre-cue in a visuomotor task while recording unit activity. We found that, when the duration of the pre-cue was predictable and long (5 s), delay of the onset of cell activity in consecutive trials gradually increased. On the other hand, when the duration was unpredictable or predictable and short ( 1 s), this phenomenon could not be detected. The inconsistent discharge correlations with expected reward and attentional processes, and the specific discharge relationship to the time instruction, suggest that these buildup neurons reflect a learning process in the time domain.

1998 - Neglect syndrome for aversive stimuli in a Macaque monkey with dorsomedial frontal cortex lesion [Articolo su rivista]
Lucchetti, Cristina; Lui, Fausta; Bon, Leopoldo
abstract

After a session of unit activity recording, one of our monkeys presented an epileptic attack, which provoked contralateral tilting movements. The following days, the animal performed saccades and fixation tasks correctly in all directions, while contralateral arm reaching movements were severely impaired. To establish if the neurological lesion had changed the orienting performance we considered two types of stimuli, pleasant and aversive. Pleasant stimuli, presented in the ipsilateral or contralateral hemifield, readily drew the attention of the animal. If the same stimuli were presented simultaneously in both hemifields, the monkey oriented itself only toward the ipsilateral one. Aversive stimuli evoked an aggressive reaction only when the stimulus was localized in the ipsilateral hemifield. The animal clearly neglected the aversive stimulus presented in the contralateral hemifield. The animal recovered completely in 30 days. The postmortem examination revealed a lesion in the dorsomedial frontal cortex. The combined attentional and motor deficits suggest that this area may be involved in the preparation and execution of movements triggered by the affective meaning of the stimulus. (C) 1998 Elsevier Science Ltd. All rights reserved.

1997 - Activity of neurons related to eye movements during drowsiness in the frontal cortex of the Macaca monkey [Articolo su rivista]
Bon, Leopoldo; Lucchetti, Cristina
abstract

During our extensive study of the supplementary eye held (SEF) in relation to eye and arm movements, we had the opportunity to record the activity of 25 out of 315 cells during both saccade task and drowsiness states. All 25 cells showed a phasic, spatially selective postsaccadic activity that was not related to fixation. During drowsiness, the discharge was time locked with the onset of the slow movement, had increased duration, and was not spatially selective. These preliminary data suggest that saccade neurons present in SEF are also involved in the motor processes of slow eye movements during drowsiness.

1997 - Attention-related neurons in the supplementary eye field of the macaque monkey [Articolo su rivista]
Bon, Leopoldo; Lucchetti, Cristina
abstract

This study investigated whether the neuronal activity of a cortical area involved in the control of eye fixation is affected by the covert orienting of attention. We recorded single-unit activity from the supplementary eye field (SEF) of two macaque monkeys performing fixation and peripheral-attention tasks. Ninety-nine out of four hundred and fifteen cells were related to eye movements. The other neurons showed relationship with postural adjustments, and arm and ear movements. Fifty-five neurons were active during fixation (fixation cells) and 44 discharged in relation to saccades. The experiments reported here primarily concern the fixation cells. The activity of 64% (35/55) of fixation cells started with the onset of visual stimulus, before the visual input reached the fovea, and continued during active fixation. The activity of 27% (15/55) of fixation cells started with the onset of fixation. The activity of 9% (5/55) of fixation cells modified their timing trial by trial. Sixty-four percent of the fixation cells (35/55) were position-dependent, showing a selective spatial field of activity, 36% (20/55) were position-independent and characterized by a full spatial field. None of the 55 cells showed a visual receptive field. We tested both types of fixation cells by means of a peripheral attention task. When attention was oriented peripherally toward a target located in the selective spatial field, the cells discharged as if the gaze was held toward it. When attention was oriented peripherally toward a target, lying outside the selective spatial field, the cells were inactive as if gaze was held in that position. These results suggest that the supplementary eye field neurons may code for oriented attention in space and might be involved in the preparation of motor action.

1997 - Motor programs of spontaneous and visually guided saccades in macaque monkey: An electrophysiological approach [Articolo su rivista]
Lucchetti, Cristina; Bon, Leopoldo
abstract

The discharge activity of 37 burst neurons in the paramedian pontine reticular formation and the saccades performed in the dark (spontaneous saccades) and between visual targets (attentive visually guided) were recorded in two macaque monkeys. Forty-five % of spontaneous saccades showed more than one maximum of velocity (irregular velocity profiles), while visually guided saccades were always characterized by a single maximum of velocity (regular velocity profiles). The discharge pattern of each burst neuron (short lead neuron) was different according to the saccade velocity profile. We observed a clear inhibition within the burst neuron discharge for irregular velocity profiles, thus giving rise to multiple maxima of discharge frequency, and to a clearly interrupted saccade. The same neuron showed only one maximum of discharge frequency for regular saccades. Then the hypothesis of two different neural networks generating the different motor programs of spontaneous and attentive visual guided saccades is put forward and discussed.

1997 - The spatio-temporal pattern of rapid eye movements in paradoxical sleep in the infant monkey [Articolo su rivista]
Lucchetti, Cristina
abstract

1994 - Ear eye representation in the frontal cortex,area 8B, of the macaque monkey: an electrophysiological study. [Articolo su rivista]
Bon, Leopoldo; Lucchetti, Cristina
abstract

We evoked both ear and eye movements in area 8b, the rostral area of frontal cortex, in two monkeys. In some sites it was possible to evoke only ear movements or only eye movements; in other locations we evoked both ear and eye movements by varying the intensity of electrical stimulation. The electrically evoked ear movements were forward, or backward, or oblique (upward-forward; upward-backward). In two penetrations the ear movements were bilateral, in the other penetrations they were contralateral. Ipsilateral ear movements were not observed. The evoked eye movements were mainly fixed-vector saccades, contralateral and with an upward orientation of about 45 degrees. If we considered only the sites where the threshold was equal to or lower than 50 microA, the stimulation of this area evoked mainly ear movements. In addition we recorded the electrical activity of 195 neurons. Of these neurons: 74% (145/195) discharged before ear movements (ear cells); 20% (40/195) discharged before ear and eye movements (ear-eye cells); 5% (10/195) discharged only before eye movements (eye cells). Ninety-one percent (132/145) of ear cells presented a preferred direction; 90% (36/40) of ear-eye cells presented a preferred direction for ear movements, and 15% (6/40) presented a preferred direction for eye movements. Eighty-five percent (34/40) of cells did not present a preferred direction for visually guided saccades and were active when the monkey made saccades toward the unlit targets (checking saccades). Our results show that a field of area 8b is related to ear movements and to eye-ear movements. The findings that it is possible to obtain both ear and eye movements with low-intensity currents and that there are cells firing for the two types of movements suggest that area 8b may be involved in the orientation and coordination of both ear and eye. This area might be considered a rostral extension of supplementary eye field (SEF) or a different region. However, based on its distinct functional characteristics and connectivity, it is probably better regarded as a separate field. Regardless, the combination of 8b and SEF may constitute a cortical center for orienting processes.

1992 - Controllo corticale dei movimenti saccadici. Il lobo frontale. [Capitolo/Saggio]
Bon, Leopoldo; Lucchetti, Cristina
abstract

In questo capitolo di libro si tratta delle aree corticali del lobo frontale coinvolte nella genesi dei movimenti oculari di tipo saccadico, considerando prevalentemente i risultati sperimentali ottenuti da studi elettrofisiologici condotti su primati non umani. Il lobo frontale comprende la corteccia prefrontale, granulare, e la corteccia frontale, agranulare. La trattazione riguarda in particolare l'Area prefrontale Oculomotoria (o "Frontal Eye Field", FEF) e l'area periprincipale oculomoria, site entrambe nella corteccia prefrontale, e l'Area supplementare oculomotoria (o "Supplementary Eye Field", SEF), sita nella corteccia frontale.

1992 - THE DORSOMEDIAL FRONTAL CORTEX OF THE MACACA MONKEY: FIXATION AND SACCADE-RELATED ACTIVITY [Articolo su rivista]
Lucchetti, Cristina; Bon, Leopoldo
abstract

The activity of 249 neurons in the dorsomedial frontal cortex was studied in two macaque monkeys. The animals were trained to release a bar when a visual stimulus changed color in order to receive reward. An acoustic cue signaled the start of a series of trials to the animal, which was then free to begin each trial at will. The monkeys tended to fixate the visual stimuli and to make saccades when the stimuli moved. The monkeys were neither rewarded for making proper eye movements nor punished for making extraneous ones. We found neurons whose discharge was related to various movements including those of the eye, neck, and arm. In this report, we describe the properties of neurons that showed activity related to visual fixation and saccadic eye movement. Fixation neurons discharged during active fixation with the eye in a given position in the orbit, but did not discharge when the eye occupied the same orbital positions during nonactive fixation. These neurons showed neither a classic nor a complex visual receptive field, nor a foveal receptive visual field. Electrical stimulation at the site of the fixation neurons often drove the eye to the orbital position associated with maximal activity of the cell. Several different kinds of neurons were found to discharge before saccades: 1) checking-saccade neurons, which discharged when the monkeys made self-generated saccades to extinguish LED's; 2) novelty-detection saccade neurons, which discharged before the first saccade made to a new visual target but whose activity waned with successive presentations of the same target. These results suggest that the dorsomedial frontal cortex is involved in attentive fixation. We hypothesize that the fixation neurons may be involved in codifying the saccade toward a target. We propose that their involvement in arm-eye-head motor-planning rests primarily in targeting the goal of the movement. The fact that saccade-related neurons discharge when the saccades are self initiated, implies that this area of the cortex may share the control of voluntary saccades with the frontal eye fields and that the activation is involved in intentional motor processes.

1992 - THE EFFECTS OF MATURATION ON SPONTANEOUS EYE-MOVEMENTS IN THE MACAQUE MONKEY [Articolo su rivista]
Lucchetti, Cristina; Cevolani, D.
abstract

The spontaneous eye movements of infant and adult monkeys were studied both in the dark and in the laboratory light by a magnetic search-coil technique and analysed comparatively. The spatio-temporal organization of the infant monkey's eye movements is predominantly vertical; by contrast it is predominantly horizontal in adults. Moreover, the infant monkey's eye movements have smaller amplitudes and slower velocities than adult's in both visual conditions. The linear relationships between amplitude and maximum velocity suggest that rapid eye movements of the infant monkey are saccades but with a lower rate of velocity increase than the adult's. We conclude that the eye movements in the infant and in the adult monkeys differ in many aspects and that maturation acts on both the static and dynamic characteristics of ocular motility.

1991 - Behavioral and motor mechanisms of dorsomedial frontal cortex in Macaca monkey [Articolo su rivista]
Bon, Leopoldo; Lucchetti, Cristina
abstract

The activity of 249 neurons in the dorsomedial frontal cortex was recorded in two macaca monkeys. The animals had been trained for saccades and fixation tasks in an unrestrained condition. We found 51 burst neurons that showed a double-firing discharge. We observed two different patterns of discharge. In one case the first burst occurred before the arm movement, the second before the related eye movement. In the second case, the first discharge took place before a neck contraction followed by a second burst before eye movement. Some cells showed two discharges, one that preceded the bar-press and the other the saccade. With other cells the discharges preceded the bar-release and then saccade. Still other cells discharged three times: first before the bar-press, second before release and third before the orienting saccade. Some cells were active for the bar-press and for the first orienting saccades. These cells were active also for a large range of movement tested at the presentation of natural stimuli. Electrical stimulation failed to evoke either arm or eye movement. Neck-eye cells are related to movement of the eye and to an increase of EMG activity independent of eye position. The electrical stimulation evoked eye movements and EMG increases at low threshold. The activity of arm-eye cells related to purposeful movement with the ineffectiveness of electrical stimulation may be ascribed to a motor reactivation or an ordering signal. The neck-eye cells may be considered trigger commands for neck-eye coordination

1991 - The dorsomedial frontal cortex (DMFC): a cortical area involved in attentive fixation. [Abstract in Rivista]
Lucchetti, Cristina; Bon, Leopoldo
abstract

The activity of dorsomedial frontal cortex has been studied in two macaca monkeys. The animals were trained for saccade and fixation task. We recorded many cells that discharged after saccades and continued for the entire period of fixation. These are fixation and not position units since the neurons are silent during relaxed scanning for the same positions. Each of these cells were tested by classic visual stimuli and by complex and motivational stimuli. None of the cells presented a visual receptive field. These neurons presented different fixation field prevalently contralateral, non only excitatory but also inhibitory. The electrical stimulation of the fixation cells evoked eye movements directed toward the fixation field. We propose that these fields are attentional motor fields because they are not expression of a motor code and the visual afferences are not directly involved. This hypothesis is corroborated by studies of cortical lesions: humans with a frontal lesion cannot avoid making saccades to a stimulus when il appears.

1990 - DOES ATTENTION AFFECT THE MOTOR PROGRAMS OF PHARMACOLOGICALLY INDUCED EYE-MOVEMENTS [Articolo su rivista]
Bon, Leopoldo; Lucchetti, Cristina
abstract

Attention plays an important role in oculomotor function. We studied the effect of attentional stimuli on eye movements induced by ketamine. The experiments were carried out on three monkeys. Ketamine injected intramuscularly induced nystagmus. When we switched on a new stimulus these eye movements stopped and the animal made a saccade toward it. This may be due to a new motor program, triggered by a visual stimulus, that among its characteristics is able to engage the animal's attention. The program of evoked saccade is overwritten on induced oculomotor activity. Our results suggest that attentional processes modify the dynamic characteristics and induce in particular behavioral condition a new motor program.

1990 - Neurons signalling the maintenance of attentive fixation in frontal area 6aB of macaque monkey [Articolo su rivista]
Bon, Leopoldo; Lucchetti, Cristina
abstract

Twelve out of 140 neurons recorded in a restricted region of the frontal agranular cortex (area 6a beta) of trained macaque monkeys, discharged only during attentive fixation of a target in the straight ahead position. These cells, lacking a visual receptive field, were silent when the animal's eye was in the same position during spontaneous oculomotor behaviour. Our preliminary results suggest that this area is involved in the codification of attentive fixation.

1989 - Attentional fixation neurons in frontal agranular cortex: area 6 aB [Abstract in Rivista]
Bon, Leopoldo; Lucchetti, Cristina
abstract

Mountcastle and his colleagues described the influence of attentive fixation and the angle of fixation upon the excitability of the light-sensitivity neurons in posterior cortex of rhesus monkey (area 7).We found cells in an area of agranular frontal cortex that code attentional processes, although they lacked receptive fields. Preliminary experiments were carried out on one monkey (Macaca nemestrina) trained to press a bar for fixation and saccade tasks. We recorded from 64 cells in a restricted zone of area 6aB, 12 of which responded only when the animal fixated central target actively during fixation or saccade task. None had receptive fields. This discharge might be the expression of motor fields or propioception or an efferent copy signal. Alternatively it may be an expression of attention. To decide between these two alternatives we studied the fixation between trials and during spontaneous behaviour. In relaxed conditions the discharge of the cells was very poor or completely absent when the animal was fixating centrally. These observations suggest that activity of these cells is independent of pure motor processes (motor field, propioception, efferent copy). Therefore, these neural discharges of cells lacking a visual field, may be considered to be an expression of attention, spatially coded in primary position.

1988 - Attentional processes and motor programs of eye movements. [Abstract in Rivista]
Bon, Leopoldo; Lucchetti, Cristina
abstract

The eye movements is the final result of many processes of sensory-motor integration. The motor programs of saccades may be modified by behavioral states and by drugs.We found in monkey that attentional processes may change the velocity profiles of saccades. As a matter of fact the spontaneous saccades in the dark or in laboratory light very frequently show a velocity profile with two or more maximum velocities or inflection points. When the animal makes saccdes between targets, and if it does this correctly it will receive a reward (some drops of water), the velocity pprofiles show only one maximum velocity. We defined the profiles irregular, in the former case, and regular in the latter one.Since the wakefulness is constant, a passive attentional stimulus evokes an unrewarded saccde of regular type anfd the irregular saccades are present before and after a trial, our hipothesis is that the different way to program the velocity may be due to attention. Particularly, attentional processes may change the discharge of premotor cells in the brainstem.(Supported by MPI-CNR).

1988 - Is vision important for the maturation of ocular movement? [Articolo su rivista]
Bon, L.; Lucchetti, C.
abstract

1988 - Retinal projections in monkey's pretectum and superior colliculus. [Abstract in Rivista]
Bon, Leopoldo; Benassi, Carlo; P., Biral; Ferrari, Renata; Lucchetti, Cristina
abstract

The pretectal area and superior colliculus play a role in oculomotion.This anatomical approach is preliminary in order to investigate, by electrophysiological and metabolic techniques, particular aspects of motor organization of pretectal area of Macaca fascicularis. We used the valina C14 injected in the eye globe to define the retinal projections on superior colliculus and particularly on pretectum. The radiographs showed clear projections to: nucleus tractus opticus (NTO), nucleus pretectalis posterior (NPP) and nucleus pretectalis olivaris (NPOL). Nucleus pretectalis anterior (Pars compacta and pars reticularis) and anterior pretectal area were not labeled. Accessory optic system appeared labeled, particularly DNT and LTN. Nucleus terminalis medialis did not appear labeled in our radiographs. Moreover, the superior colliculus showed a surprising projection like patches.Supported by Ministero della Pubblica Istruzione (40%).

1988 - Spontaneous saccades in young awake monkey. [Abstract in Rivista]
Lucchetti, Cristina; D., Cevolani
abstract

The aim of this study is to compare the static and dynamic characteristics of young monkey's saccades with adult monkey's. The experiments were carried out on one young monkey of 80-90 days of life and on three adult monkeys. The eye movements were detected by magnetic field technique, in the dark and in the light. A soft cup was used for painless fixation of young animal's head. The analysis of eye movements was done by a PDP 11/73. The results show that the spatio-temporal pattern of eye movements is prevalently vertical or slightly oblique in young monkey, contrary it is prevalently horizontal or slightly oblique in the adult: besides the amplitudes are smaller and the velocities are slower in the adult. From these preliminary results we may think that maturation modifies the static and dynamic characteristics of eye movements.

1988 - The motor programs of monkey's saccades: an attentional hypothesis [Articolo su rivista]
Bon, Leopoldo; Lucchetti, Cristina
abstract

We analyzed the dynamics of saccadic eye movements performed by monkeys in three different conditions: as a part of an ocular motor task, spontaneously when the monkey was alert but not performing a task in ordinary room illumination, and spontaneously when the monkey was alert but not performing a task in total darkness. We found three general classes of saccades: 1) regular-symmetric, in which the rise time of the velocity profile was equal to the falling time; 2) regular-asymmetric, in which the rise time was less than the falling time; 3) irregular, in which there were multiple velocity maxima or inflection points. The monkeys made irregular saccades half the time in the two spontaneous saccade conditions, and almost never during the task. In order to see if the regularity of saccades was an artifact of reward, we then evoked saccades by presenting the monkeys with novel visual and acoustic stimuli to which they made saccades. Such guided saccades to novel stimuli had regular velocity profiles. We suggest that saccades made as a part of attentive behavior differ in their motor programming from saccades made spontaneously in darkness, or saccades made in the light without a purpose relevant to visual behavior.

1988 - The saccadic eye movements in infant monkey. [Abstract in Rivista]
Lucchetti, Cristina; D., Cevolani
abstract

Previous studies showed that the static and dynamic characteristics of eye movements between cat and kitten are different. The aim of this research is to study the effects of maturation, if there are any effects, on spatio-temporal characteristics of eye movements in the monkey. The experiments were carried out on one infant monkey (aged 80-90 days) and three adult monkey (Macaca nemestrina). Eye movements were detected by means of a magnetic field technique, in the dark and in the light. For painless fixation of the head Evart's technique was employed in adult monkeys while in the infant monkey a soft cup fixed to a suitable chair was used. The behavioural state was monitored by EEG and EMG. Eye movements were analised off-line by a PDP 11/73. Preliminary results show that the spatio-temporal pattern is prevalently vertical or slightly oblique in the infant monkey; on the contrary it is prevalently horizontal or oblique in the adults. Furthermore, the amplitudes of the saccades are smaller and the peak velocities are slower in the infant than in the adults. We may then argue that maturative processes act on ocular motility.

1987 - A new technical approach to monkey visual training. [Articolo su rivista]
Bon, Leopoldo; Chiarelli, F; Lucchetti, Cristina
abstract

To train the monkey for visual task we use the microcomputer and a bicoloured LED. This system is very advantageous in respect of its low cost and the ease of use.

1987 - Effect of visual input in motor programs of saccades [Capitolo/Saggio]
Bon, Leopoldo; Lucchetti, Cristina
abstract

The aim of this research is to verify whether motor programs of eye movements are modified by visual input. The experiments were carried out on one monkey (Macaca nemestrina) trained to track targets. The eye movements were recorded in darkness, under laboratory lighting and between targets. Three types of velocity patterns were identified: symmetrical, asymmetrical and irregular. From the statistical analysis, no substantial differences in distribution are present between darkness (no visual stimuli) and laboratory light (visual stimuli). In the target situation, the irregular pattern is totally absent. This suggest that visual input modifies motor programs, but probably only if it has an attentional meaning for the animal.

1986 - The motor programs of monkey's saccades. [Abstract in Rivista]
Lucchetti, Cristina; Bon, Leopoldo
abstract

In this report we studied if the visual input by itself or a visual input with an attentional meaning may modify the velocity profiles of saccades. One monkey (Macaca nemestrina) was trained to perform visual fixation and make saccades to visual targets. We analized the velocity profiles of spontaneous saccades in dark and in laboratory light, and of visually guided saccades. We found three different velocity profiles: symmetrical, asymmetrical and irregular. The normalized frequency distribution of the three different velocity patterns displayed no difference between the two rest conditions, contrary, in the work condition, the irregular profiles were absent. These results may suggest that only a visual input with an attentional meaning may modify substantially the motor program of saccades

1985 - THE SPONTANEOUS EYE-MOVEMENTS IN THE AWAKE KITTEN [Articolo su rivista]
Bon, Leopoldo; Lucchetti, Cristina
abstract

The spontaneous eye movements were analysed comparatively in the kitten and in the cat. The eye movements were recorded in the dark by a magnetic search coil technique. The spatio-temporal organization of eye movements in the kitten has a prevailing vertical orientation and differs completely from that of the cat. In the kitten the amplitude of eye movements is smaller than in the cat and only a few movements are followed by fixation. It results, by correlating amplitude-peak velocity, that rapid eye movements in the awake kitten are saccades. From our results we conclude that the eye movements in the kitten and in the cat differ in many aspects and that the visual system is responsible for the development of the correct oculomotor behaviour.