Unmasking motion-processing activity in human brain area V5/MT+ mediated by pathways that bypass primary visual cortex.

Published

Journal Article

Most models of the human visual system argue that higher-order motion-processing cortical regions receive their inputs only via the primary visual cortex (striate cortex), rather than also via direct projections from the thalamus that bypass primary visual cortex. However, recent evidence in non-human primates, along with some evidence in humans with damaged primary visual cortex (e.g., "blindsight" for motion in the blind visual hemifield), have argued for the existence of a direct thalamic-to-extrastriate projection for motion processing. This evidence remains controversial. Here we tested the idea that direct thalamic input to extrastriate motion processing areas exists in humans but might be masked in scalp recordings by activity from early visual areas. To do this, we employed stimuli that induced strong refractory effects in primary visual cortex--thereby creating a brief "reversable lesion" in primary visual cortex--immediately before the presentation of a motion stimulus. Under these conditions, we then assessed whether motion areas of cortex were still able to process the motion stimuli by recording event-related potentials (ERPs) and event-related magnetic fields (ERFs/MEG). We found robust motion-related activity in extrastriate motion processing areas in the ERP and MEG signals even when primary visual cortex was heavily suppressed by our manipulation. This finding provides evidence for a direct thalamic functional pathway to extrastriate visual cortical motion processing areas in the human that bypasses primary visual cortex.

Full Text

Duke Authors

Cited Authors

  • Schoenfeld, MA; Heinze, H-J; Woldorff, MG

Published Date

  • October 2002

Published In

Volume / Issue

  • 17 / 2

Start / End Page

  • 769 - 779

PubMed ID

  • 12377152

Pubmed Central ID

  • 12377152

International Standard Serial Number (ISSN)

  • 1053-8119

Language

  • eng

Conference Location

  • United States