Evidence for Context - sensitivity of Grasp Representations in Human Parietal and Premotor 1 Cortices

248 words 14 Running Head: Context-specificity of grasp representations 15 16 17 18 19 20 21 Articles in PresS. J Neurophysiol (March 2, 2011). doi:10.1152/jn.00796.2010 Copyright © 2011 by the American Physiological Society. Context-specificity of grasp representations 2 Abstract 22 Grasp-related responses in neurons of the macaque rostral inferior parietal lobule (PF/PFG and the 23 anterior intraparietal area (AIP)) are modulated by task context. Event-related fMRI was used to 24 ask whether this is true in putative homologues of the human cortex, the human rostral inferior 25 parietal lobule (rIPL) and the anterior intraparietal sulcus (aIPS). Fifteen healthy, right-handed, 26 adults were required to select prospectively the most comfortable way to grasp a horizontally27 oriented handle using the cued hand (left or right). In the NO ROTATION condition, the task was 28 simply to grasp the handle, while in the ROTATION condition the goal was to plan to grasp and 29 rotate it into a vertical orientation with the cued end (medial or lateral) pointing downward. In both 30 conditions, participants remained still and indicated their grip preferences by pressing foot pedals. 31 As in overt grasping, participants’ grip preferences were significantly influenced by anticipation of 32 the demands associated with handle rotation. Activity within the aIPS and rIPL increased 33 bilaterally in both the ROTATION and NO ROTATION conditions. Importantly, these responses 34 were significantly greater in the ROTATION vs. NO ROTATION condition. Similar context 35 effects were detected in the pre-supplementary motor area (pre-SMA), caudal intraparietal sulcus 36 (cIPS)/superior parietal lobule (SPL), bilateral dorsal (dPMC) and left ventral (vPMC) premotor 37 cortices. Grasp representations within the rIPL and aIPS are sensitive to predicted task demands and 38 play a role in context-sensitive grip selection. Moreover, the findings provide additional evidence 39 that areas involved in the sensorimotor control of grasp also contribute to feedforward planning. 40 41