Architettonica e connessioni della corteccia prefrontale ventrolaterale caudale della scimmia macaca

La corteccia prefrontale ventrolaterale (VLPF) caudale del macaco è delimitata posteriormente dal solco arcuato inferiore, dorsalmente dal solco principale e rostralmente dalla fossetta frontale inferiore ed è costituita da almeno 3 differenti domini funzionali: uno localizzato in corrispondenza del banco anteriore del solco arcuato, i Frontal Eye Fields -FEF-, ed implicato in funzioni di tipo oculomotorio, uno localizzato in corrispondenza del solco principale, implicato nella programmazione di compiti visuospaziali ed infine uno localizzato nella regione della convessità inferiore prefrontale ed implicato nella processazione di informazioni non spaziali in termini cognitivamente complessi. Il nostro interesse si è focalizzato nei confronti della porzione caudale della corteccia prefrontale ventrolaterale, alla luce di recenti studi di risonanza magnetica funzionale, condotti sulla scimmia, che hanno evidenziato la presenza di foci di attivazione, in corrispondenza della porzione più ventrale del solco arcuato inferiore e della regione della convessità localizzata rostralmente rispetto ad esso, durante la visione di azioni biologiche e di stimoli visivi complessi. La VLPF del macaco è stata oggetto in passato di molteplici studi anatomici il cui risultato sono state suddivisioni architettoniche non completamente concordi tra loro che hanno conseguentemente generato conflitti interpretativi riguardanti la localizzazione dei dati funzionali ed odologici e la loro attribuzione alle differenti aree corticali così anatomicamente definite. Recentemente inoltre Petrides e Pandya hanno proposto una parcellazione della VLPF nella quale identificano un'area che ipotizzano, in virtù di analogie morfologiche ed anatomiche, possa essere omologa e precursore dell'area di Broca dell'uomo. L'area è ulteriormente suddivisa dai due autori in due porzioni distinte: una localizzata nella porzione ventrale del banco anteriore del solco arcuato inferiore, denominata 45B, ed una localizzata rostralmente in corrispondenza dell'adiacente convessità , e denominata 45A. I due autori enfatizzano inoltre, allo scopo di avvalorare l'eventuale omologia con la corrispondente area dell'uomo, connessioni che quest'area, considerata come un unicum, mostra con le cortecce uditive del giro temporale superiore in cui sono processate informazioni acustiche di tipo complesso. Alla luce di questi recenti studi di Petrides e Pandya nel nostro lavoro ci siamo focalizzati nel definire se i due settori 45A e 45B dell'area 45 potessero essere considerati distinti architettonicamente ed odologicamente, sia l'uno rispetto all'altro che rispetto alle altre aree della VLPF caudale, ed in secondo luogo nel definire se l'area 45, o esclusivamente una delle sue suddivisioni, potesse corrispondere alla regione della convessità target di proiezioni da regioni uditive di tipo complesso, nella quale sono stati registrati neuroni che rispondono a stimoli communicativi e per la quale è stata proposta un'omologia con la corrispondete area dell'uomo

Action observation and execution network : an extended view

The mirror mechanism is a basic mechanism that transforms sensory representations of others' behaviours into one's own motor or visceromotor representations concerning that behaviour. In this review, we examine the different functions of the mirror mechanism according to its location in the brain, with particular emphasis on recent data concerning the prefrontal cortex and the emotional centres.peer-reviewe

the neural bases of vitality forms

Abstract Unlike emotions, which are short-lasting events accompanied by viscero-motor responses, vitality forms are continuous internal states that modulate the motor behaviors of individuals and are devoid of the autonomic modifications that characterize real emotions. Despite the importance of vitality forms in social life, only recently have neurophysiological studies been devoted to this issue. The first part of this review describes fMRI experiments, showing that the dorso-central insula is activated during the execution, the perception and the imagination of arm actions endowed with different vitality forms as well as during the hearing and the production of speech conveying vitality forms. In the second part, we address the means by which the dorso-central insula modulates the networks for controlling action execution and how the sensory and interoceptive information is conveyed to this insular sector. Finally, we present behavioral data showing the importance of vitality forms in social interactions

Neuronal Encoding of Self and Others' Head Rotation in the Macaque Dorsal Prefrontal Cortex.

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

Laminar Origin of Corticostriatal Projections to the Motor Putamen in the Macaque Brain

In the macaque brain, projections from distant, interconnected cortical areas converge in specific zones of the striatum. For example, specific zones of the motor putamen are targets of projections from frontal motor, inferior parietal, and ventrolateral prefrontal hand-related areas and thus are integral part of the so-called "lateral grasping network." In the present study, we analyzed the laminar distribution of corticostriatal neurons projecting to different parts of the motor putamen. Retrograde neural tracers were injected in different parts of the putamen in 3 Macaca mulatta (one male) and the laminar distribution of the labeled corticostriatal neurons was analyzed quantitatively. In frontal motor areas and frontal operculum, where most labeled cells were located, almost everywhere the proportion of corticostriatal labeled neurons in layers III and/or VI was comparable or even stronger than in layer V. Furthermore, within these regions, the laminar distribution pattern of corticostriatal labeled neurons largely varied independently from their density and from the projecting area/sector, but likely according to the target striatal zone. Accordingly, the present data show that cortical areas may project in different ways to different striatal zones, which can be targets of specific combinations of signals originating from the various cortical layers of the areas of a given network. These observations extend current models of corticostriatal interactions, suggesting more complex modes of information processing in the basal ganglia for different motor and nonmotor functions and opening new questions on the architecture of the corticostriatal circuitry

Anterior Intraparietal Area: a Hub in the Observed Manipulative Action Network.

Current knowledge regarding the processing of observed manipulative actions (OMAs) (e.g., grasping, dragging, or dropping) is limited to grasping and underlying neural circuitry remains controversial. Here, we addressed these issues by combining chronic neuronal recordings along the anteroposterior extent of monkeys\u2019 anterior intraparietal (AIP) area with tracer injections into the recorded sites. We found robust neural selectivity for 7 distinct OMAs, particularly in the posterior part of AIP (pAIP), where it was associated with motor coding of grip type and own-hand visual feedback. This cluster of functional properties appears to be specifically grounded in stronger direct connections of pAIP with the temporal regions of the ventral visual stream and the prefrontal cortex, as connections with skeletomotor related areas and regions of the dorsal visual stream exhibited opposite or no rostrocaudal gradients. Temporal and prefrontal areas may provide visual and contextual information relevant for manipulative action processing. These results revise existing models of the action observation network, suggesting that pAIP constitutes a parietal hub for routing information about OMA identity to the other nodes of the network

The extended object-grasping network

Grasping is the most important skilled motor act of primates. It is based on a series of sensorimotor transformations through which the affordances of the objects to be grasped are transformed into appropriate hand movements. It is generally accepted that a circuit formed by inferior parietal areas AIP and PFG and ventral premotor area F5 represents the core circuit for sensorimotor transformations for grasping. However, selection and control of appropriate grip should also depend on higher-order information, such as the meaning of the object to be grasped, and the overarching goal of the action in which grasping is embedded. In this review, we describe recent findings showing that specific sectors of the ventrolateral prefrontal cortex are instrumental in controlling higher-order aspects of grasping. We show that these prefrontal sectors control the premotor cortex through two main gateways: the anterior subdivision of ventral area F5-sub-area F5a-, and the pre-supplementary area (area F6). We then review functional studies showing that both F5a and F6, besides being relay stations of prefrontal information, also play specific roles in grasping. Namely, sub-area F5a is involved in stereoscopic analysis of 3D objects, and in planning cue-dependent grasping activity. As for area F6, this area appears to play a crucial role in determining when to execute the motor program encoded in the parieto-premotor circuit. The recent discovery that area F6 contains a set of neurons encoding specific grip types suggests that this area, besides controlling â\u80\u9cwhen to goâ\u80\u9d, also may control the grip type, i.e., â\u80\u9chow to goâ\u80\u9d. We conclude by discussing clinical syndromes affecting grasping actions and their possible mechanisms