Eye-centered encoding of visual space in scene-selective regions.
We used functional magnetic resonance imaging (fMRI) to investigate the reference frames used to encode visual information in scene-responsive cortical regions. At early levels of the cortical visual hierarchy, neurons possess spatially selective receptive fields (RFs) that are yoked to specific locations on the retina. In lieu of this eye-centered organization, we speculated that visual areas implicated in scene processing, such as the parahippocampal place area (PPA), the retrosplenial complex (RSC), and transverse occipital sulcus (TOS) might instead possess RFs defined in head-, body-, or world-centered reference frames. To test this, we scanned subjects while they viewed objects and scenes presented at four screen locations while they maintained fixation at one of three possible gaze positions. We then examined response profiles as a function of either fixation-referenced or screen-referenced position. Contrary to our prediction, the PPA and TOS exhibited position-response curves that moved with the fixation point rather than being anchored to the screen, a pattern indicative of eye-centered encoding. RSC, on the other hand, did not exhibit a position-response curve in either reference frame. By showing an important commonality between the PPA/TOS and other visually responsive regions, the results emphasize the critical involvement of these regions in the visual analysis of scenes.
Department of Psychology and Center for Cognitive Neuroscience, University of Pennsylvania, PA, USA. emily.ward@yale.edu
Emily J
EJ
Ward
Sean P
SP
MacEvoy
Russell A
RA
Epstein
D000328:Adult; D005145:Face; D005260:Female; D005403:Fixation, Ocular / Q000502:physiology; D005556:Form Perception / Q000502:physiology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009778:Occipital Lobe / Q000502:physiology; D020534:Parahippocampal Gyrus / Q000502:physiology*; D010775:Photic Stimulation / Q000379:methods; D013028:Space Perception / Q000502:physiology*; D014794:Visual Fields / Q000502:physiology*; D055815:Young Adult