V1 neurons respond to luminance changes faster than contrast changes (original) (raw)
Related papers
Temporal coding of contrast in primary visual cortex: when, what, and why
Journal of neurophysiology, 2001
How do neurons in the primary visual cortex (V1) encode the contrast of a visual stimulus? In this paper, the information that V1 responses convey about the contrast of static visual stimuli is explicitly calculated. These responses often contain several easily distinguished temporal components, which will be called latency, transient, tonic, and off. Calculating the information about contrast conveyed in each component and in groups of components makes it possible to delineate aspects of the temporal structure that may be relevant for contrast encoding. The results indicate that as much or more contrast-related information is encoded into the temporal structure of spike train responses as into the firing rate and that the temporally coded information is manifested most strongly in the latency to response onset. Transient, tonic, and off responses contribute relatively little. The results also reveal that temporal coding is important for distinguishing subtle contrast differences, w...
PLoS ONE, 2011
Background: When we are viewing natural scenes, every saccade abruptly changes both the mean luminance and the contrast structure falling on any given retinal location. Thus it would be useful if the two were independently encoded by the visual system, even when they change simultaneously. Recordings from single neurons in the cat visual system have suggested that contrast information may be quite independently represented in neural responses to simultaneous changes in contrast and luminance. Here we test to what extent this is true in human perception.
Robust temporal coding of contrast by V1 neurons for transient but not for steady-state stimuli
The Journal of neuroscience : the official journal of the Society for Neuroscience, 1998
We show that spike timing adds to the information content of spike trains for transiently presented stimuli but not for comparable steady-state stimuli, even if the latter elicit transient responses. Contrast responses of 22 single neurons in macaque V1 to periodic presentation of steady-state stimuli (drifting sinusoidal gratings) and transient stimuli (drifting edges) of optimal spatiotemporal parameters were recorded extracellularly. The responses were analyzed for contrast-dependent clustering in spaces determined by metrics sensitive to the temporal structure of spike trains. Two types of metrics, cost-based spike time metrics and metrics based on Fourier harmonics of the response, were used. With both families of metrics, temporal coding of contrast is lacking in responses to drifting sinusoidal gratings of most (simple and complex) V1 neurons. However, two-thirds of all neurons, mostly complex cells, displayed significant temporal coding of contrast for edge stimuli. The Four...
Cortical visual processing is temporally dispersed by luminance in human subjects
Neuroscience Letters, 1999
Increasing the intensity of a stimulus such as luminance results in faster processing of the signal and therefore decreases simple motor reaction time (RT). We studied the latencies of visual evoked potentials (VEPs, N80, P100, N130) and RTs in eight subjects to flashing spots of light while varying the luminance of the spots from 1 to 1000 cd/m 2 . The data show that processing time as a function of intensity is modified not only at the retina but also at later processing sites. This indicates a temporal dispersion of the visual signal over the whole processing stream from visual input all the way to motor output.
The Journal of neuroscience : the official journal of the Society for Neuroscience, 2016
Differences between visual pathways representing darks and lights have been shown to affect spatial resolution and detection timing. Both psychophysical and physiological studies suggest an underlying retinal origin with amplification in primary visual cortex (V1). Here we show that temporal asymmetries in the processing of darks and lights create motion in terms of propagating activity across V1. Exploiting the high spatiotemporal resolution of voltage-sensitive dye imaging, we captured population responses to abrupt local changes of luminance in cat V1. For stimulation we used two neighboring small squares presented on either bright or dark backgrounds. When a single square changed from dark to bright or vice versa, we found coherent population activity emerging at the respective retinal input locations. However, faster rising and decay times were obtained for the bright to dark than the dark to bright changes. When the two squares changed luminance simultaneously in opposite pola...
Spatial Frequency-Specific Contrast Adaptation Originates in the Primary Visual Cortex
Journal of Neurophysiology, 2007
tation to a high-contrast grating stimulus causes reduced sensitivity to subsequent presentation of a visual stimulus with similar spatial characteristics. This behavioral finding has been attributed by neurophysiological studies to processes within the visual cortex. However, some evidence indicates that contrast adaptation phenomena are also found in early visual pathways. Adaptation effects have been reported in retina and lateral geniculation nucleus (LGN). It is possible that these early pathways could be the physiological origin of the cortical adaptation effect. To study this, we recorded from single neurons in the cat's LGN. We find that contrast adaptation in the LGN, unlike that in the visual cortex, is not spatial frequency specific, i.e., adaptation effects apply to a broad range of spatial frequencies. In addition, aside from the amplitude attenuation, the shape of spatial frequency tuning curves of LGN cells is not affected by contrast adaptation. Again, these findings are unlike those found for cells in the visual cortex. Together, these results demonstrate that pattern specific contrast adaptation is a cortical process.
Vision research, 1997
Temporal interactions between spatially separated visual stimuli were investigated in human observers. Subjects had to judge whether briefly presented targets consisted of a single or a double flash. Simultaneous presentation of unattended single or double flash distractors impaired performance if target and distractor followed different time courses, confirming previous findings. This interference occurred only when targets had high luminance contrast or were isoluminant and when distractors had high or low luminance contrast, but not when targets had low luminance contrast or when distractors were isoluminant. Low luminance contrast distractors strongly influenced high luminance contrast targets but not vice versa. These results suggest that (i) information about the precise temporal structure of stimuli is conveyed preferentially by the luminance-sensitive magnocellular system; and (ii) that this information influences judgements on the temporal patterning of signals transmitted ...
Biological Cybernetics, 2006
Reaction time (RT) and error rate that depend on stimulus duration were measured in a luminance-discrimination reaction time task. Two patches of light with different luminance were presented to participants for 'short' (150 ms) or 'long' (1 s) period on each trial. When the stimulus duration was 'short', the participants responded more rapidly with poorer discrimination performance than they did in the longer duration. The results suggested that different sensory responses in the visual cortices were responsible for the dependence of response speed and accuracy on the stimulus duration during the luminance-discrimination reaction time task. It was shown that the simple winner-take-all-type neural network model receiving transient and sustained stimulus information from the primary visual cortex successfully reproduced RT distributions for correct responses and error rates. Moreover, temporal spike sequences obtained from the model network closely resembled to the neural activity in the monkey prefrontal or parietal area during other visual decision tasks such as motion discrimination and oddball detection tasks.
Temporal properties of the visual responses to luminance and contrast modulated noise
Vision is sensitive to first-order luminance modulations and second-order modulations of carrier contrast. Our knowledge of the temporal properties of second-order vision is insufficient and contradictory. Using temporal summation and reaction time paradigms, we found that the type of visual noise (static or dynamic) determines the temporal properties of the responses to luminance and contrast modulations. In the presence of static noise, the temporal responses to both types of modulation of low and higher spatial frequencies were transient. When dynamic noise was used, the temporal responses to luminance and contrast modulations of higher spatial frequencies were sustained. At low spatial frequency, however, luminance modulations elicited transient responses, while contrast modulated dynamic noise produced sustained responses. The reaction times to near-threshold contrast modulations of low spatial frequency were slower than those to first-order patterns and they did not significantly differ at modulations of higher spatial frequency. The results suggest that the temporal characteristics of first-stage linear filters which feed the second-order pathway may determine the temporal responses to contrast modulated noise.