Spatiotemporal impulse response and cortical magnification

According to a model of the spatiotemporal weighting function (Manahilov, V. Spatiotemporal visual response at suprathreshold stimuli. Vision Research, 1995, 35, 227-237; and Triphasic temporal impulse responses and Mach bands in time. Vision Research, 38, 447-458) the waveform of the temporal-impulse response and the cortical spread of the spatial-impulse response should not depend on the retinal site of stimulation. To verify these model predictions, the spatiotemporal responses to brief near-threshold lines presented in the fovea and the near retinal periphery were studied. The effect of an inducing stimulus on the threshold for pattern detection of a test stimulus was measured, assuming that the pattern-detection threshold was determined by the test peak response. The spatial spread of the line response expressed in visual-field units was increased with eccentricity. The temporal-impulse responses to foveal and peripheral stimuli were similar. The model of the weighting function was used to evaluate the relative magnification factor for the retinal location tested. The calculated cortical spatial-impulse responses did not depend on the stimulation site. The data obtained are in line with the cortical magnification theory of peripheral vision.