The constructive nature of vision: direct evidence from functional magnetic resonance imaging studies of apparent motion and motion imagery

TLDR

Echoplanar fMRI was used to monitor activation changes while subjects viewed apparent motion stimuli and engaged in motion imagery. Apparent motion activates dorsal stream areas MT/V5 and MST first, with illusory contours further engaging V2 and MT/MST, while motion imagery elicits a graded dorsal and prefrontal response that increases with distance from V1 and selectively activates MT/MST, illustrating a complex network driven by both bottom‑up and top‑down processes.

Abstract

Abstract Echoplanar functional magnetic resonance imaging was used to monitor activation changes of brain areas while subjects viewed apparent motion stimuli and while they were engaged in motion imagery. Human cortical areas MT (V5) and MST were the first areas of the ‘dorsal’ processing stream which responded with a clear increase in signal intensity to apparent motion stimuli as compared with flickering control conditions. Apparent motion of figures defined by illusory contours evoked greater activation in V2 and MT/MST than appropriate control conditions. Several areas of the dorsal pathway (V3A, MT/MST, areas in the inferior and superior parietal lobule) as well as prefrontal areas including FEF and BA 9/46 responded strongly when subjects merely imagined moving stimuli which they had seen several seconds before. The activation during motion imagery increased with the synaptic distance of an area from V1 along the dorsal processing stream. Area MT/MST was selectively activated during motion imagery but not during a static imagery control condition. The comparison between the results obtained with objective motion, apparent motion and imagined motion provides further insights into a complex cortical network of motion‐sensitive areas driven by bottom‐up and top‐down neural processes.