Misura e decodifica dell'attività neurale durante compiti motori guidati dalla memoria visiva

Several experimental evidences show that the neurons in a specific area of the parietal cortex (area V6A of the monkey) are active when the arm moves inside the peripersonal space to execute movements guided by visual stimuli. Lesions restricted to this area provoke misreaching when the subject tries to reach a visual target with the hand (syndrome of optic ataxia). These and others observations support the hypothesis that neural activity in area V6A could integrate the information regarding visual stimuli to command the execution of a motor task. In particular, this area could operate the transformation which convert information from the retina in space-motor coordinates, useful to direct arm movements during visual guided movements in the peripersonal space. The verification of the validity of this hypothesis is an essential condition for the development of functional prosthesis of the superior limb controlled by signals of neural activity derived from the parietal cortex. To demonstrate the consistence of the above-stated hypothesis, the present research project intend to verify the possibility to extract from extra-cellular recordings of neural activity in area V6A of a non-human primate: i) information in relation to visual stimuli which determine the execution of a visual-memory guided movement task; ii) information in relation to types of movement execution. For this verification, in the present research project one animal (Macaca fascicularis) will be used and will be trained to move the arm guided by visual stimuli. In particular, the animal will be trained to look at a lightened fixation point projected on a screen. During the fixation period, a visual stimulus will appear on the screen for some seconds, indicating to the animal the position which must be reached (target). A following visual stimulus will indicate to the animal to execute a movement to reach the target with hand. After animal training, during the execution of the visuo-motor task, it will be recorded: single neurons activity in area V6A recorded by microelectrodes inserted in the posterior parietal cortex, eyes movements recorded by an infrared oculometer, and arm movements of the animal (position and velocity of the segments and joint angles) measured with a system developed specifically during the present project. The data recorded in the experiments will be analysed with mathematical models of activity which codes and elaborates visuo-motor information. The most innovative part of this project is represented by the development of theoretical models which are able to correlate the recorded neural activity of single trials with the visual stimuli determining the execution of the task and with the types of motor act execution. Combining the theoretical with the experimental approach, there will be a comparison of the observed responses in the different periods of the experiment in the way to determine in which measure and in base on which type the investigated cortical area codes for different informations (ocular, visual, preparation of the movement, etc.). In particular, it will be tried to value in which measure: a) the significance of the stimulus (fixation point, target, movement execution, etc.) conditions the neural activity; b) the single neurons partecipate in different time intervals at neural circuits which code for different informations; c) the target position is memorized indipendently from the direction of gaze; d) cognitive functions, which could condition the task execution, as expectation or attention, condition the neural activity.