Common cortical loci are activated during visuospatial interpolation and orientation discrimination judgements.
There is a wealth of literature on the role of short-range interactions between low-level orientation-tuned filters in the perception of discontinuous contours. However, little is known about how spatial information is integrated across more distant regions of the visual field in the absence of explicit local orientation cues, a process referred to here as visuospatial interpolation (VSI). To examine the neural correlates of VSI high field functional magnetic resonance imaging was used to study brain activity while observers either judged the alignment of three Gabor patches by a process of interpolation or discriminated the local orientation of the individual patches. Relative to a fixation baseline the two tasks activated a largely over-lapping network of regions within the occipito-temporal, occipito-parietal and frontal cortices. Activated clusters specific to the orientation task (orientation>interpolation) included the caudal intraparietal sulcus, an area whose role in orientation encoding per se has been hotly disputed. Surprisingly, there were few task-specific activations associated with visuospatial interpolation (VSI>orientation) suggesting that largely common cortical loci were activated by the two experimental tasks. These data are consistent with previous studies that suggest higher level grouping processes -putatively involved in VSI- are automatically engaged when the spatial properties of a stimulus (e.g. size, orientation or relative position) are used to make a judgement.
Tibber
Marc S
MS
Department of Optometry and Visual Science, City University, London, United Kingdom. mtibber@yahoo.com
Anderson
Elaine J
EJ
Melmoth
Dean R
DR
Rees
Geraint
G
Morgan
Michael J
MJ
D001931:Brain Mapping; D002540:Cerebral Cortex / Q000502:physiology*; D005625:Frontal Lobe / Q000502:physiology; D006801:Humans; D008279:Magnetic Resonance Imaging; D009415:Nerve Net; D010296:Parietal Lobe / Q000502:physiology; D013028:Space Perception / Q000502:physiology*; D014794:Visual Fields / Q000502:physiology