TY - JOUR T1 - Cortical merging in S1 as a substrate for tactile input grouping JF - eneuro JO - eNeuro DO - 10.1523/ENEURO.0342-17.2017 SP - ENEURO.0342-17.2017 AU - Julien Corbo AU - Yoh’I Zennou-Azogui AU - Christian Xerri AU - Nicolas Catz Y1 - 2018/01/04 UR - http://www.eneuro.org/content/early/2018/01/04/ENEURO.0342-17.2017.abstract N2 - Perception is a reconstruction process guided by rules based on knowledge about the world. Little is known about the neural implementation of the rules of object formation in the tactile sensory system. When two close tactile stimuli are delivered simultaneously on the skin, subjects feel a unique sensation, spatially centered between the two stimuli. Voltage sensitive dye imaging (VSDi) and electrophysiological recordings (local field potentials -LFPs- and single units) were used to extract the cortical representation of two-point tactile stimuli in the primary somatosensory cortex of anesthetized Long Evans rats. While layer-4 LFP responses to brief costimulation of the distal region of two digits resembled the sum of individual responses, about one third of single units demonstrated merging-compatible changes. In contrast to previous intrinsic optical imaging studies, VSD activations reflecting layer 2/3 activity were centered between the representations of the digits stimulated alone. This merging was found for every tested distance between the stimulated digits. We discuss this laminar difference as an evidence that merging occurs through a build-up stream and depends on the superposition of inputs which increases with successive stages of sensory processing. These findings show that layers 2/3 are involved in the grouping of sensory inputs. This process that could be inscribed in the cortical computing routine and network organization, is likely to promote object formation and implement perception rules.Significance Statement When two close tactile stimuli are delivered simultaneously on the skin, subjects feel a unique sensation, spatially centered between the two stimuli. to understand the mechanism underlying this sensory merging, we investigated the S1 cortical representation of coincidental two-point stimuli. We demonstrated the phenomenon of cortical merging by which two distinct sensory inputs are represented by a unique and centered cortical activation. Our results, obtained with technical approaches capturing different stages of cortical processing, suggest that this merging is build up as the sensory peripheral information travels along the S1 cortical network. By performing such merging, a fundamental role of S1 could be the grouping of distinct sensory stimuli into relevant perceptual objects. ER -