Biomedical subjects

V Gallese

Publications and source records attributed to V Gallese.

30 records · Page 2Linked to original sources

PubMed1996

Action recognition in the premotor cortex.

We recorded electrical activity from 532 neurons in the rostral part of inferior area 6 (area F5) of two macaque monkeys. Previous data had shown that neurons of this area discharge during goal-directed hand and mouth movements. We describe here the properties of a newly discovered set of F5 neurons ("mirror neurons', n = 92) all of which became active both when the monkey performed a given action and when it observed a similar action performed by the experimenter. Mirror neurons, in order to be visually triggered, required an interaction between the agent of the action and the object of it. The sight of the agent alone or of the object alone (three-dimensional objects, food) were ineffective. Hand and the mouth were by far the most effective agents. The actions most represented among those activating mirror neurons were grasping, manipulating and placing. In most mirror neurons (92%) there was a clear relation between the visual action they responded to and the motor response they coded. In approximately 30% of mirror neurons the congruence was very strict and the effective observed and executed actions corresponded both in terms of general action (e.g. grasping) and in terms of the way in which that action was executed (e.g. precision grip). We conclude by proposing that mirror neurons form a system for matching observation and execution of motor actions. We discuss the possible role of this system in action recognition and, given the proposed homology between F5 and human Brocca's region, we posit that a matching system, similar to that of mirror neurons exists in humans and could be involved in recognition of actions as well as phonetic gestures.

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PubMed1996

Parietal neurons related to memory-guided hand manipulation.

1. We recorded activity of the hand-manipulation-task-related neurons in the posterolateral bank of the anterior intraparietal sulcus (area AIP) of the monkey parietal cortex during a delayed hand manipulation task. 2. We examined mainly the object-type visual-dominant and visual-and-motor neurons that responded to the sight of objects for manipulation. The majority of these neurons (32 of 48) showed sustained activity during the delay period in the dark before manipulation of preferred objects. 3. Six visual-and-motor neurons showed set-related activity before the hand manipulation in the dark, so that their delay period activity was likely to be related to motor preparation. 4. The delay period activity of 18 visual-dominant and visual-and-motor neurons without set-related activity was likely to represent spatial features of objects, because the majority of the neurons showed the same selectivity in the shape and/or orientation during object fixation and the delay period. 5. Of these 18 neurons, 10 showed sustained activity in the dark after brief illumination of objects during a light-interrupted fixation task, suggesting that they store the short-term memory of objects without the intention to remember. 6. The results suggest that the visual memory of three-dimensional features of objects is likely to be incorporated in area AIP and to be used for the guidance of hand manipulation.

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PubMed1996

Coding of peripersonal space in inferior premotor cortex (area F4).

1. We studied the functional properties of neurons in the caudal part of inferior area 6 (area F4) in awake monkeys. In agreement with previous reports, we found that the large majority (87%) of neurons responded to sensory stimuli. The responsive neurons fell into three categories: somatosensory neurons (30%); visual neurons (14%); and bimodal, visual and somatosensory neurons (56%). Both somatosensory and bimodal neurons typically responded to light touch of the skin. Their RFs were located on the face, neck, trunk, and arms. Approaching objects were the most effective visual stimuli. Visual RFs were mostly located in the space near the monkey (peripersonal space). Typically they extended in the space adjacent to the tactile RFs. 2. The coordinate system in which visual RFs were coded was studied in 110 neurons. In 94 neurons the RF location was independent of eye position, remaining in the same position in the peripersonal space regardless of eye deviation. The RF location with respect to the monkey was not modified by changing monkey position in the recording room. In 10 neurons the RF's location followed the eye movements, remaining in the same retinal position (retinocentric RFs). For the remaining six neurons the RF organization was not clear. We will refer to F4 neurons with RF independent of eye position as somatocentered neurons. 3. In most somatocentered neurons (43 of 60 neurons) the background level of activity and the response to visual stimuli were not modified by changes in eye position, whereas they were modulated in the remaining 17. It is important to note that eye deviations were constantly accompanied by a synergic increase of the activity of the ipsilateral neck muscles. It is not clear, therefore, whether the modulation of neuron discharge depended on eye position or was a consequence of changes in neck muscle activity. 4. The effect of stimulus velocity (20-80 cm/s) on neuron response intensity and RF extent in depth was studied in 34 somatocentered neurons. The results showed that in most neurons the increase of stimulus velocity produced an expansion in depth of the RF. 5. We conclude that space is coded differently in areas that control somatic and eye movements. We suggest that space coding in different cortical areas depends on the computational necessity of the effectors they control.

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PubMed1994

Deficit of hand preshaping after muscimol injection in monkey parietal cortex.

In order to assess the functional role of the parietal hand movement region, the anterior part of the lateral bank of the intraparietal sulcus (IPS), area AIP, in the visual guidance of hand grasping, we reversibly inactivated several parts of this area with microinjections of Muscimol in a monkey trained to grasp objects of different shapes, sizes and orientations. During the local inactivation, some of the skilled patterns of finger movements were disrupted in the contralateral hand, due to the lack of preshaping to adjust the finger posture to the object; however, no major deficits in visual reaching were observed. The results suggest that area AIP plays a crucial role in the visual guidance of goal-directed hand movements.

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PubMed1994

The fronto-parietal cortex of the prosimian Galago: patterns of cytochrome oxidase activity and motor maps.

We mapped the motor areas of the prosimian Galago crassicaudatus using intracortical electrical microstimulation and morphological and histochemical (cytochrome oxidase) techniques. Stimulation data showed that on the brain convexity there is an area (area Frontalis posterior, F post.) from which movements could be evoked at low threshold (< 10 microA). This area is somatotopically organized, with the leg represented medially, the arm centrally and the face and mouth laterally. Proximal and distal movements are not segregated. Most of the evoked movements, even at threshold, consist of movements involving two or more joints. F post. is characterized by a three-band cytochrome oxidase activity pattern. It has an agranular structure, but it lacks pyramidal cells that are larger than those observed in other areas. In front of F post. there is an area histochemically similar to it, Frontalis intermedialis (F int.). This area consists of two cytoarchitectonic divisions: an agranular division (F int. pars caudalis) and a disgranular division (F int. pars rostralis). The excitability threshold of F int. is relatively high (10 to 30 microA). Eye, ear and neck movements are elicited from its lateral part, whereas trunk movements associated with limb movements are elicited from its medial part. Caudal to F post., there is another region from which movements can be evoked with currents between 10 to 30 microA. This region has the same medio-lateral somatotopic arrangement of F post. Typically, single joint movements are elicited from it. Proximal and distal movements are not segregated. In spite of its homogeneity in terms of motor response, the posterior excitable region is formed by two anatomically separate areas: anterior somatic area (S ant.) and posterior somatic area (S post.). S ant. has a typical koniocortex structure, whereas S post, resembles the parakoniocortex as defined by Sanides (J. Hirnforsch., 9 (1967) 225-252). Histochemically both areas are made up of four longitudinal stripes differing for enzymatic activity. The three superficial stripes tend to merge together and are sharply separated from a deeply located, light stripe. This stripe is homogeneous in S ant., whilst its central part shows an increase in activity in S post. The possible homologies between the motor and somatic areas of the galago and monkey as well as their role in movement control are discussed.

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PubMed1992

Space coding by premotor cortex.

Many neurons in inferior area 6, a cortical premotor area, respond to visual stimuli presented in the space around the animal. We were interested to learn whether the receptive fields of these neurons are coded in retinotopic or in body-centered coordinates. To this purpose we recorded single neurons from inferior area 6 (F4 sector) in a monkey trained to fixate a light and detect its dimming. During fixation visual stimuli were moved towards the monkey both within and outside the neuron's receptive field. The fixation point was then moved and the neuron retested with the monkey's gaze deviated to the new location. The results showed that most inferior area 6 visual neurons code the stimulus position in spatial and not in retinal coordinates. It is proposed that these visual neurons are involved in generating the stable body-centered frame of reference necessary for programming visually guided movements.

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PubMed1992

Understanding motor events: a neurophysiological study.

Neurons of the rostral part of inferior premotor cortex of the monkey discharge during goal-directed hand movements such as grasping, holding, and tearing. We report here that many of these neurons become active also when the monkey observes specific, meaningful hand movements performed by the experimenters. The effective experimenters' movements include among others placing or retrieving a piece of food from a table, grasping food from another experimenter's hand, and manipulating objects. There is always a clear link between the effective observed movement and that executed by the monkey and, often, only movements of the experimenter identical to those controlled by a given neuron are able to activate it. These findings indicate that premotor neurons can retrieve movements not only on the basis of stimulus characteristics, as previously described, but also on the basis of the meaning of the observed actions.

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PubMed1992

Prehension movements directed to approaching objects: influence of stimulus velocity on the transport and the grasp components.

In this investigation we studied the influence of object velocity on the transport and on the grasp components of prehension movements directed to approaching objects. Three experiments were carried out. In the first experiment six subjects were required to reach and grasp a sphere that approached them with a constant velocity. The effects of four velocities were studied. The results showed that the end point of the arm movement changed with object velocity: nearer the body with higher than with lower object velocities. Transport velocity increased with movement amplitude and the deceleration phase decreased in duration with higher object velocities. On the contrary the grasp component was not affected by object velocity. The second experiment was a control experiment carried out in order to verify whether a possible influence of object velocity on the grasp could be revealed in an experimental condition in which grasp planning relies without doubt on visual computation of all object features. In this experiment object velocity and object size were randomly varied. The results showed that the grasp was not influenced by object velocity, whereas it was sensitive to changes of object size. The third experiment had the two-fold aim of establishing (1) whether transport velocity was influenced by object velocity once the location in space at which the object had to be grasped was fixed and (2) whether the grasp kinematics differed for prehension movements directed respectively to stationary or to moving objects. Results showed that the first part of the transport is affected only by distance, whereas the deceleration phase decreased with increasing object velocity. This last result suggests that subjects minimized object displacements in order to grasp the sphere correctly. The grasp component differed between the conditions of stationary and moving stimuli only in the relative timing between finger aperture and closure phases. The closure phase decreased in the condition of moving stimuli. The results of the three experiments indicate the dependence of transport parameters on object velocity, whereas grasp parameters appear to be unaffected.

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PubMed1991

Multiple representations of body movements in mesial area 6 and the adjacent cingulate cortex: an intracortical microstimulation study in the macaque monkey.

The mesial agranular frontal cortex that lies rostral to area 4 (F1) is formed by two distinct cytoarchitectonic areas: F3, located caudally, and F6, located rostrally. In the present experiments we investigated the organization of F3 and F6 by observing the motor responses evoked by their intracortical electrical microstimulation. Our main purpose was to find out whether the cytoarchitectonic subdivision of the mesial agranular frontal cortex into two areas has a physiological counterpart. The result showed that F3 (the caudal area) contains a complete motor representation with hindlimb movements located caudally, forelimb movements located centrally, and orofacial movements located rostrally. The great majority of limb movements involved proximal joints. With respect to F1, F3 showed the following functional characteristics: (1) lack of segregation between proximal and distal movements, (2) larger percentage of complex movements, and (3) higher excitability threshold. Movements were more difficult to elicit from F6 (the rostral area) than from F3. However, by using a longer stimulus train duration (100 ms) 39.3% of tested sites produced body movements. This percentage increased (50.5%) when the electrical stimulation was applied during monkey natural movements instead of when the monkey was still in its chair. Most of the evoked movements concerned the forelimb. More rarely, neck and upper face movements were observed. Unlike F1 and F3 where most movements were fast, slow movements were frequently observed with stimulation of F6. Many of them mimicked natural movements of the animal. Eye movements were evoked from F7 (superior area 6) but not from F6. An additional motor representation was found in the dorsocaudal part of area 24 (24d). This area is topographically organized with a forelimb representation located caudally and ventrally and a hindlimb representation located rostrally and dorsally. The excitability threshold of area 24d is higher than that of F1 and F3. Evoked movements were occasionally observed also after stimulation of area 24c. In conclusion, on the mesial cortical wall rostral to F1, there are at least three independent motor representations. On the basis of somatotopic organization and excitability properties, we propose that the term supplementary motor area (SMA-proper) should be reserved to F3.

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PubMed1991

[Kinematic study of reaching-grasping movements in the monkey].

Kinematics of reaching-grasping movement towards stimuli of three different sizes located at two different distances were studied in one monkey (Macaca nemestrina). Transport and manipulation components were analyzed using the ELITE system. Transport time, peak velocity and deceleration phase of velocity were influenced by stimulus size, whilst acceleration phase remained unmodified. Peak velocity clearly increased with distance, while transport time remained constant (isochrony ). The main parameters of manipulation component were all influenced by stimulus size but they did not vary with distance. A comparison with kinematic data obtained from human subjects was made.

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PubMed1990

Neurons related to reaching-grasping arm movements in the rostral part of area 6 (area 6a beta).

Single neurons were recorded from the rostral part of the agranular frontal cortex (area 6a beta) in awake, partially restrained macaque monkeys. In the medialmost and mesial sectors of this area, rostral to the supplementary motor area, neurons were found which were activated during arm reaching-grasping movements. These neurons ("reaching-grasping neurons") did not appear to be influenced by how the objects were grasped nor, with some exceptions, by where they were located. Their activity changed largely prior to the arm movement and continued until the end of it. The premovement modulation (excitatory or inhibitory) could start with stimulus presentation, with the saccade triggered by the stimulus or after stimulus fixation. The distance of the stimulus from the monkey was an important variable for activating many neurons. About half of the recorded neurons showed a modulation of the same sign during movement and premovement period. The other half showed an increase/decrease in activity which was of the opposite sign during movement and premovement period or part of it. In this last case the discharge changes were of the same sign when the stimulus was close to the monkey and when the monkey moved its arm to reach the objects, whereas they were of opposite sign when the stimulus was outside the animal's reach. Microstimulation of area 6a beta and the reconstruction of the locations of eye movement and arm movement related cells showed that the arm field was located more medially (and mesially) than the eye field described by Schlag and Schlag-Rey (1987). It is suggested that, unlike inferior area 6, which is mostly involved in selection of effectors on the basis of the physical properties of the objects and their spatial location (Rizzolatti and Gentilucci 1988), area 6a beta plays a role in the preparation of reaching-grasping arm movements and in their release when the appropriate conditions are set.

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PubMed1984

[Neurological deficit following a lesion in the parietal area 7b in the monkey].

The effect of unilateral surgical ablations of lateral part of inferior parietal lobule (area 7b) has been studied in the macaque monkey. The following neurological deficits were found: 1) A hemi-inattention for tactile stimuli applied to the hemiface and hand contralateral to the lesion; 2) A hemi-inattention for visual stimuli in the contralateral peripersonal space; 3) A reluctance to use the contralateral arm; 4) A mild and transient deficit in mouth grasping movements towards stimuli contralaterally presented; 5) Postural abnormalities of the hand contralateral to the lesion. It is proposed that area 7b is involved in the perception of the peripersonal space and in the organization of movements towards stimuli presented in that space.

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