Codifica della risposta neuronale nella corteccia premotoria ventrale del macaco durante l'esecuzione di azioni di afferramento in condizioni di freely-moving: studio neurofisiologico e comportamentale

In the last decades, classical neurophysiological studies of non-human primates have required the use of tethered recording systems and the performance of experiments under restrained conditions, in which animals had to be trained to perform stereotyped and well-controlled behaviors while seated in a primate-chair. These studies allowed the development of a deep knowledge of brain functions, but we should note the limitations of these experimental paradigms: the restrained conditions do not allow the investigation of many of the complex behaviors that animals can display in the wild, leaving much of natural behaviors unexplored. In recent years, many researchers have become interested in the possibility of recording the neuronal activity under unconstrained conditions, and have developed wireless recording systems. Wireless technologies allow to study the relationship between the brain and complex behaviors performed in naturalistic conditions, to pursue more ecologically relevant questions, and to pave the way for the field of neuroethology, which aims to discover the correlations between brain and behavior in order to establish the evolutionary history based on homologies and analogies of brain structures and functions in different animal species. However, wireless recording systems have presented some limitations: the large variability that characterizes spontaneous behavior complicates the possibility of deeply understanding the specific information encoded by the neurons of a given brain region. This study aims to find a novel and reliable method to investigate the neural activity recorded during free movement, focusing on grasping action, a relevant motor behavior for wild monkeys that spend much of their time foraging in the environment, climbing trees, or grooming conspecifics. The experiment involved two males rhesus macaques and was carried out in a spacious enclosure, called NeuroEthoRoom, equipped with various objects that allowed the monkeys to perform several manipulative actions. We collected neural data from the brain region involved in the control of the grasping actions, i.e. the ventral premotor cortex, and matched these data with video recordings of the behavior. By applying a non-linear dimensionality reduction technique (UMAP) to the neural dataset, and creating an appropriate ethogram based on the previous literature about the information encoded by the premotor cortex, we found the behaviorally relevant clusters at the neural population level. We found that clustering factors were determined by the type of grip, the direction of movement and the objects grasped (food or items). These findings were confirmed at the individual unit level, as we found some PMv neurons significantly modulated when the monkey grasped an object and others when the monkey climbed up. Thus, using a top-down approach (which first examines the neuronal population and then the single-units activity) we obtained an accurate description of the functional properties of PMv neurons, demonstrating the reliability of this approach to manage and disentangle the neuronal signal gathered in freely-moving condition. In summary, by overcoming the large variability characteristic of naturalistic behaviors, we can deeply understand the relationship between brain and behavior by relying on wireless recording systems and improve animal welfare by avoiding training and restrained conditions.