Cerebral Cortex Advance Access originally published online on August 18, 2006
Cerebral Cortex 2007 17(6):1350-1363; doi:10.1093/cercor/bhl046
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Temporal Evolution and Strength of Neural Activity in Parietal Cortex during Eye and Hand Movements
Dipartimento di Fisiologia umana e Farmacologia, Università di Roma "La Sapienza", 00185 Rome, Italy
Address correspondence to Prof Alexandra Battaglia-Mayer, Dipartimento di Fisiologia umana e Farmacologia, Università di Roma "La Sapienza," Piazzale Aldo Moro 5, 00185 Rome, Italy. Email: alexandra.battagliamayer{at}uniroma1.it.
The role of area 7a in eye–hand movement was studied by recording from individual neurons while monkeys performed 7 different tasks, aimed at assessing the relative influence of retinal, eye, and hand information on neural activity. Parietal cell activity was modulated by visuospatial signals about target location, as well as by information concerning eye and/or hand movement, and position. The highest activity was elicited when the hand moved to the fixation point. The population activities across different memory tasks showed common temporal peaks when aligned to the visual instruction (visuospatial peak) or Go signal (motor peak) for eye, hand, and coordinated eye–hand movement. The motor peak was higher for coordinated eye–hand movement, and it was absent in a No-Go task. Two activation maxima were also observed during visual reaching. They had the same latency of the visuospatial and motor peaks seen in the memory tasks. Therefore, area 7a seems to operate through a common neural mechanism underlying eye, hand, or combined eye–hand movement. This mechanism is revealed by invariant temporal activity profiles and is independent from the effector selected and from the presence or absence of a visible target during movement. For comparative purposes, we have studied the temporal evolution of the population activity in the superior parietal lobule (SPL) during the same reaching tasks and during a saccade task. In SPL, the population activity was characterized by a single peak, time locked to the Go signal for eye, hand, or combined eye–hand movement. As in IPL, the time of occurrence of this peak was effector independent. The population activity remained unchanged when the position of the eye changed, suggesting that SPL is mostly devoted to the hand motor behavior.
Key Words: eye–hand coordination • eye–hand temporal coupling • inferior parietal lobule • onset time of neural activity • reaching • superior parietal lobule
Funding to pay the Open Access publication charges for this article was provided by the Ministry of the University and Scientific Research (MIUR) of Italy.
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