Cortical end-stopped perceptive fields: evidence from dichoptic and amblyopic studies.

Psychophysical length and width spatial interactions associated with a line target were measured in normal observers dichoptically and in observers with naturally acquired amblyopia to investigate the neural locus of end-stopped perceptive fields. Results show (1) interocular transfer of psychophysical end-stopping, flank-inhibition, and length and width summation; and (2) severe, but significantly different, loss of end-stopping and flank-inhibition in the central visual fields of amblyopic eyes. Together, these results suggest a cortical basis for end-stopped perceptive fields, and that psychophysical end-stopping and flank-inhibition are a consequence of distinct cortical inhibition. The damaging effects of amblyopia on end-stopping and flank-inhibition are weaker and less different from each other under transient conditions. Our results provide further evidence supporting the suggestion that end-stopped perceptive fields are the psychophysical analogs of cortical end-stopped receptive fields.