Cognitive Control Signals in Visual Cortex: Flashes Meet Spotlights

  • Frédéric Joliot

Abstract

Across several species, primary visual cortex (V1) is arguably the most heavily studied and best understood brain area. The investigation of its functional response properties was heralded by the seminal work of Hubel and Wiesel who were first in eliciting reliable and selective responses of single neurons to sensory stimuli. These stimulus-related response properties included retinotopic receptive fields and orientation selectivity and have appeared in every neuroscience textbook. Along these lines, V1 is still often thought of as a camera-like device that provides a somewhat distorted and fractured but fairly veridical representation of the retinal image. Yet its neurons seem to be involved in functions going beyond mere image representation. This insight comes as no surprise if one considers the anatomical connectivity of V1 and realizes that retinogeniculo-cortical afferents provide only a fraction of its input (Casagrande and Kaas, 1994). Despite these anatomical clues, it has proven more difficult to evoke V1 responses by mechanisms other than sensory stimulation, as for instance by visual imagery or spatial attention, cognitive processes that are associated with strong activity changes elsewhere in the brain. Following initial sparse electrophysiological reports of attentional V1 activity modulation, significant progress came from functional magnetic resonance imaging (fMRI) studies that mapped activations during covert spatial attention to corresponding retinotopic representations of the attended visual field locations (reviewed in Posner and Gilbert, 1999). Given the number and quality of studies at the crossroads of V1 function and spatial attention, one would have believed this gold mine to be fully exploited, but the study by Jack et al. (2006) in this issue of Neuron comes up with a novel neuroscience nugget: they report transient V1 activations that are neither associated with stimulus processing nor with spatial attention. Separation in time (between stimulus presentation and behavioral reporting) and space (within retinotopic cortical maps) allow them not only to reproduce previous findings on spatial attention but also to distinguish from these signals a novel endogenously generated V1 response. Spatial attention (orienting) induces signal increases that are maximal at the time of stimulus presentation and at the cortical representation of stimulus location. Across retinotopic areas, these signals grow in size

Cite this paper

@inproceedings{JoliotCognitiveCS, title={Cognitive Control Signals in Visual Cortex: Flashes Meet Spotlights}, author={Fr{\'e}d{\'e}ric Joliot} }