TRIPHASIC TEMPORAL IMPULSE RESPONSES AND MACH BANDS IN TIME

The effect of inducing stimuli on the luminance of a brief test stimul us (2.5'-wide line) required to match the brightness of a comparison s timulus was measured at various stimulus onset asynchronies (SOAs), As suming that the test brightness is determined by the peak response to the test stimulus, the difference in the test brightness in the absenc e and in the presence of an inducing stimulus as a function of the SOA was employed as a measure of the temporal response to the inducing st imulus, The temporal responses to brief decremental inducing stimuli ( a 2.5'-wide line and a 30'-wide bar) consisted of three oscillations, the middle one being the largest. The triphasic form of the temporal i mpulse responses was confirmed by measuring the temporal step response s to these stimuli, The step responses consisted of alternating positi ve and negative phases which might be regarded as a temporal analogue of the Mach bands in space, The data obtained were described by a mode l of the weighting function which was assumed to be a spatiotemporal G abor-like function. (C) 1998 Elsevier Science Ltd. All rights reserved .