Jason Ng1, Gerald Westheimer. 1. Division of Neurobiology, University of California, Berkeley 94720-3200, USA.
Abstract
PURPOSE: Further evidence is presented that Landolt C acuity has an integration time extending over several hundred milliseconds, well beyond the Bunsen-Roscoe-Bloch critical duration within which the intensity-time reciprocity for visual thresholds holds. METHODS: To test whether all segments of a longer exposure contribute equally to the uptake of acuity information, the acuity impairment caused by short-duration masking stimuli was measured for a range of onset asynchronies. RESULTS: A 50-ms mask impairs resolution most when it is presented 50 to 100 ms after the onset of the target, and it no longer influences acuity when shown 50 ms after its extinction. CONCLUSION: Allowing for the well-established optimally-effective test-mask asynchrony of 50 ms or so, the results permit the conclusion that whereas acuity information is assimilated during the whole exposure of a target, the first 50 ms are more effective, and this fits with the initial peaking of impulse activity of neurons in the primate visual cortex to flashed visual stimuli.
PURPOSE: Further evidence is presented that Landolt C acuity has an integration time extending over several hundred milliseconds, well beyond the Bunsen-Roscoe-Bloch critical duration within which the intensity-time reciprocity for visual thresholds holds. METHODS: To test whether all segments of a longer exposure contribute equally to the uptake of acuity information, the acuity impairment caused by short-duration masking stimuli was measured for a range of onset asynchronies. RESULTS: A 50-ms mask impairs resolution most when it is presented 50 to 100 ms after the onset of the target, and it no longer influences acuity when shown 50 ms after its extinction. CONCLUSION: Allowing for the well-established optimally-effective test-mask asynchrony of 50 ms or so, the results permit the conclusion that whereas acuity information is assimilated during the whole exposure of a target, the first 50 ms are more effective, and this fits with the initial peaking of impulse activity of neurons in the primate visual cortex to flashed visual stimuli.