Neural correlates for task-relevant facilitation of visual inputs during visually-guided hand movements Nicolas Lebar a , Pierre-Michel Bernier b , Alain Guillaume a , Laurence Mouchnino a , Jean Blouin a, ⁎ a Laboratory of Cognitive Neuroscience, FR 3C 3512, CNRS and Aix-Marseille University, Marseille, France b Department of Kinanthropology, University of Sherbrooke, Sherbrooke, Quebec, Canada abstract article info Article history: Received 4 February 2015 Accepted 12 July 2015 Available online 17 July 2015 Vision is a powerful source of information for controlling movements, especially fine actions produced by the hand that require a great deal of accuracy. However, the neural processes that enable vision to enhance move- ment accuracy are not well understood. In the present study, we tested the hypothesis that the cortical sensitivity to visual inputs increases during a spatially-constrained hand movement compared to a situation where visual information is irrelevant to the task. Specifically, we compared the cortical visual-evoked potentials (VEPs) in re- sponse to flashes (right visual hemifield) recorded while participants followed the outline of an irregular polygon with a pen (i.e., tracing), with VEPs recorded when participants simply kept the pen still. This tracing task was chosen specifically because it requires many different visual processes (e.g., detection of line orientation, motion perception, visuomotor transformation) to be completed successfully. The tracing and resting tasks were per- formed with normal vision and also with mirror-reversed vision, thereby increasing task difficulty when tracing. We predicted that the sensitivity to visual inputs would be enhanced (i.e. greater VEPs) during tracing and that this increase in response sensitivity would be greater when tracing was performed with mirror-reversed vision. In addition, in order to investigate the existence of a link between the sensitivity to visual inputs and the accuracy with which participants traced the shape, we assigned participants to high performer (HP) or low performer (LP) groups according to their tracing performance in the condition with mirror-reversed visual feedback. Source analyses revealed that, for both groups, the sensitivity to visual inputs of the left occipital and MT/MST regions increased when participants traced the shape as compared to when they were resting. Also, for both groups of participants, the mirror-reversed vision did not affect the amplitude of the cortical response to visual inputs but increased the latencies of the responses in the occipital, temporal, and parietal regions. However, the HP group showed cortical responses that largely differed from those displayed by the LP group. Specifically, the HP group demonstrated movement-related increases of visual sensitivity in regions of the visual cortex that were not observed in the LP group. These increased responses to visual inputs were evidenced in the posterior inferior parietal, temporal–occipital, and inferior-temporal regions. Overall, our results are in line with the asser- tion that increasing the sensitivity to visual inputs serves to promote relevant visual information for the different processes involved during visually-guided hand movements. Our results also suggest that maintaining accurate hand tracing movements in the presence of discrepant visual and somatosensory feedback requires additional perceptual and spatial information processing that is tightly linked to visual inputs. © 2015 Elsevier Inc. All rights reserved. Introduction There is accumulating evidence that the brain dynamically increases the weight of somatosensory inputs during the preparation and execu- tion of movements whose control largely depends on proprioceptive or cutaneous feedback (Blouin et al., 2014; Cybulska-Klosowicz et al., 2011; Knecht et al., 1993; Staines et al., 2002; Saradjian et al., 2013). Surprisingly, despite the fact that vision has long been recognized as a dominant source of information for controlling one's movements (e.g., Woodworth, 1899), electrophysiological evidence of the increased weight of visual inputs during visually-guided motor actions has not been reported. Nevertheless, several lines of evidence from behavioral research suggest that motor planning processes do increase the weight of visual inputs. For instance, hand visual feedback has been found to have a greater impact on movement accuracy when subjects prepare their movements with prior knowledge that vision will be available dur- ing their reaches (Zelaznik et al., 1983; Elliott and Allard, 1985). Motor preparation is also known to facilitate the processing of visual informa- tion related to the target of the movement. For instance, Wykowska et al. (2009) reported that the detection of the size of the target was NeuroImage 121 (2015) 39–50 ⁎ Corresponding author at: Laboratory of Cognitive Neuroscience, CNRS and Aix- Marseille University, 3 Place Victor Hugo, Marseille 13001, France. Fax: +33 413 550 956. E-mail address: jean.blouin@univ-amu.fr (J. Blouin). http://dx.doi.org/10.1016/j.neuroimage.2015.07.033 1053-8119/© 2015 Elsevier Inc. All rights reserved. Contents lists available at ScienceDirect NeuroImage journal homepage: www.elsevier.com/locate/ynimg