From vision to action: Hand representations in macaque grasping areas AIP, F5, and M1

by Stefan Schaffelhofer
Doctoral thesis
Date of Examination:2014-07-29
Date of issue:2014-12-19
Advisor:Prof. Hansjörg Scherberger
Referee:Prof. Hansjörg Scherberger
Referee:Prof. Dr. Stefan Treue
Persistent Address: http://dx.doi.org/10.53846/goediss-4841

 

 

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Abstract

English

Grasping and manipulating objects of different shapes is a fundamental feature of the primate hand. This skill requires the transformation of visual object information into corresponding hand actions. In the primate brain these processes are linked to area AIP (anterior intraparietal cortex), F5 (ventral premotor cortex) and M1 (primary motor cortex). Although these areas demonstrate selective responses when hand movements are planned or executed, it is up to now unclear how visual and motor information is encoded on the neuronal population level. To address this question, two rhesus monkeys were trained to grasp up to 50 different objects in a delayed reach-to-hold task. In this, the kinematic of the hand was measured with an instrumented glove developed for this purpose together with spiking activity recorded from up to 300 neurons using microelectrode arrays. The high variation of visual stimuli and motor responses elicited from this task allowed us separating visual attributes of objects from motor features of the hand.  Canonical discriminant- and hierarchical cluster analysis demonstrated a dominant visual role of AIP during both planning and execution epochs. The neural population separated the objects primarily on their shape and secondarily on their size. Furthermore, we found indicators for the processing of object affordances that are relevant for grasping. In contrast to AIP, we could identify a distinct motor role in F5 that encoded the objects in motor terms. However, the highest similarity to the recorded hand kinematics could be observed at the level of M1. We could visualize and prove that the population of M1 is precisely reflecting the multi-joint space of hand and arm. These findings significantly improved our understanding of how visuomotor transformations are processed in the brain.    
Keywords: grasping; hand; macaque; cortex
 
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