Il ruolo della Corteccia Parietale Posteriore nelle Funzioni Esecutive: uno studio di registrazione elettrofisiologica nella scimmia sveglia.

Intelligent, adaptive, task-oriented behavior allows individuals to pursue goals consistent with their internal needs and appropriate for the given external circumstances. Such complex form of action control is very useful because it is versatile and flexible, but it requires sophisticated brain architectures. For this reason it is thought to be an exquisite prerogative of humans and other primates. These species can engage in articulated behaviors primarily because they possess executive control mechanisms, which coordinate the different cognitive functions needed for every choice and course of action. A full understanding of executive control processes, both at the functional and neurobiological level, is therefore a major scientific and social challenge. To date scientific research in this realm has mainly focused on the frontal regions of the cerebral cortex. However, recent functional brain imaging data and few electrophysiological studies seem to also implicate the posterior parietal cortex (PPC) in these functions, above and beyond its traditional role in space processing. Inspired by these findings from the literature, we have developed a research project aimed at exploring the contribution of the PPC to executive control by means of an electrophysiological approach. In particular, we trained two Macaca mulatta monkeys to perform a task-switching paradigm. The monkeys were instructed by a visual cue to perform either an orientation-discrimination or a color-discrimination task on a set of bivalent stimuli (colored-oriented bars). Among the different scientific questions which can be addressed with our experimental design, we focused initially on looking for evidence bearing on a role of the PPC in encoding behavioral abstract rules and contexts, suggesting a contribution of the PPC in flexible monitoring and adjusting actions in order to pursue a selected goal. Detailed analysis of the behavioral performance, in terms of error rate, reaction times and inverse efficiency score demonstrates that, despite the high complexity of the paradigm, the animals have learned to master the task with a high degree of proficiency. Moreover, the pattern of performance of the animals, although with some discrepancies, is highly consistent. Importantly, the pattern of performance shows a number of the critical features of task-switching, in particular substantial behavioral costs, paralleling human performance in analogous tasks. Electrophysiological data analysis focused on the variations of neuronal spiking activity during the task. The activity of PPC neurons reflects the use of cognitive resources during the task. Our results confirm a contribution of this area to the instantiation and suitable reconfiguration of cognitive set.