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The Journal of Neuroscience, February 11, 2009, 29(6):1928-1936; doi:10.1523/JNEUROSCI.4998-08.2009

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Behavioral/Systems/Cognitive
Hand Orientation during Reach-to-Grasp Movements Modulates Neuronal Activity in the Medial Posterior Parietal Area V6A

Patrizia Fattori, Rossella Breveglieri, Nicoletta Marzocchi, Daniela Filippini, Annalisa Bosco, and Claudio Galletti

Dipartimento di Fisiologia Umana e Generale, Università di Bologna, I-40126 Bologna, Italy

Correspondence should be addressed to Dr. Claudio Galletti, Dipartimento di Fisiologia Umana e Generale, Università di Bologna, I-40126 Bologna, Italy. Email: claudio.galletti{at}unibo.it

Reach-to-grasp actions involve several components of forelimb movements needed to direct the hand toward the object to be grasped, and to orient and preshape the hand according to the object axis and shape. Area V6A, which represents a node of the dorsomedial frontoparietal circuits, has so far been implicated only in directing the arm toward different spatial locations. The present results confirm this finding and demonstrate, for the first time, that during reach-to-grasp, V6A neurons are also modulated by the orientation of the hand. In the present work the object to be grasped was a handle that could have different orientations. Reach-to-grasp movements were executed in complete darkness while gazing at a small fixation point. The majority of the tested cells (76/142; 54%) turned out to be sensitive to the orientation of the handle. Neurons could be modulated during preparation or execution of reach-to-grasp movements. The most represented cells were those modulated by hand orientation both during preparatory and movement periods. These data show that reaching and grasping are processed by the same population of neurons, providing evidence that the coordination of reaching and grasping takes place much earlier than previously thought, i.e., in the parieto-occipital cortex. The data here reported are in agreement with results of lesions to the medial posterior parietal cortex in both monkeys and humans, and with recent imaging data in humans, all of them indicating a functional coupling in the control of reaching and grasping by the medial parietofrontal circuit.

Key words: neurophysiology; dorsal visual stream; grasping; hand–object interaction; monkey; superior parietal lobule; optic ataxia

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Received Oct. 16, 2008; revised Dec. 4, 2008; accepted Jan. 12, 2009.

Correspondence should be addressed to Dr. Claudio Galletti, Dipartimento di Fisiologia Umana e Generale, Università di Bologna, I-40126 Bologna, Italy. Email: claudio.galletti{at}unibo.it

This article has been cited by other articles:

				J. P. Gallivan and D. K. Wood Simultaneous Encoding of Potential Grasping Movements in Macaque Anterior Intraparietal Area J. Neurosci., September 30, 2009; 29(39): 12031 - 12032. [Full Text] [PDF]

				S. Ferraina, E. Brunamonti, M. A. Giusti, S. Costa, A. Genovesio, and R. Caminiti Reaching in Depth: Hand Position Dominates over Binocular Eye Position in the Rostral Superior Parietal Lobule J. Neurosci., September 16, 2009; 29(37): 11461 - 11470. [Abstract] [Full Text] [PDF]

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