Pattern evoked potentials from the cat's retina

We have studied electroretinograms (ERG) in the cat using phase-reversed sinusoidal gratings as a stimulus. Our purpose was to characterize response properties of this type of ERG. One basic question we addressed was whether the response to a grating stimulus is actually pattern specific. For the purpose of comparison, we used the same stimulus to investigate mass potentials from the lateral geniculate nucleus (LGN) and the visual cortex. The pattern ERG consists mainly of a vitreous negative after potential peaking shortly (120-200 ms) after reversal of the pattern. There is a notable absence in the pattern ERG of a b-wave that, however, can be elicited by a step increase of luminance over a uniform field. Pattern ERG amplitudes decrease monotonicaly with increasing spatial frequency and show no low-frequency attenuation when the pattern is phase reversed in square-wave fashion. This is markedly different than evoked potentials from the LGN and visual cortex that show band-pass characteristics. On the other hand, sinusoidal phase reversal reveals a clear attenuation of the pattern ERG amplitude at low spatial frequencies, whereas this type of stimulation produces very poor responses from LGN and visual cortex. The low spatial-frequency attenuation in the pattern ERG shows that the generating mechanism involves lateral interactions. There is thus a clear pattern-specific component in the pattern ERG. The pattern ERG has a surprisingly high contrast threshold relative to those estimated from cortical and LGN evoked potentials. Above threshold, pattern ERG response amplitude increases rapidly with contrast, but it often shows saturation at high contrast levels. These saturation points are generally high when contrast thresholds are high so that the rising portion of the contrast-response functions have fairly uniform slopes. Contrast-response curves from the LGN and cortical potentials are quite different from those for the retina in that amplitudes increase approximately linearly with log contrast over a 2-log-unit range (1 to 100%).

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Differential contributions of magnocellular and parvocellular pathways to the contrast response of neurons in bush baby primary visual cortex (V1)

Visual Neuroscience ◽

10.1017/s095252380017107x ◽

2000 ◽

Vol 17 (1) ◽

pp. 71-76 ◽

Cited By ~ 22

Author(s):

JOHN D. ALLISON ◽

PETER MELZER ◽

YUCHUAN DING ◽

A.B. BONDS ◽

VIVIEN A. CASAGRANDE

Keyword(s):

Visual Cortex ◽

Primary Visual Cortex ◽

Response Amplitude ◽

Contrast Threshold ◽

Peak Response ◽

V1 Neurons ◽

Bush Baby ◽

High Stimulus ◽

Average Contrast ◽

Contrast Response

How neurons in the primary visual cortex (V1) of primates process parallel inputs from the magnocellular (M) and parvocellular (P) layers of the lateral geniculate nucleus (LGN) is not completely understood. To investigate whether signals from the two pathways are integrated in the cortex, we recorded contrast-response functions (CRFs) from 20 bush baby V1 neurons before, during, and after pharmacologically inactivating neural activity in either the contralateral LGN M or P layers. Inactivating the M layer reduced the responses of V1 neurons (n = 10) to all stimulus contrasts and significantly elevated (t = 8.15, P < 0.01) their average contrast threshold from 8.04 (± 4.1)% contrast to 22.46 (± 6.28)% contrast. M layer inactivation also significantly reduced (t = 4.06, P < 0.01) the average peak response amplitude. Inactivating the P layer did not elevate the average contrast threshold of V1 neurons (n = 10), but significantly reduced (t = 4.34, P < 0.01) their average peak response amplitude. These data demonstrate that input from the M pathway can account for the responses of V1 neurons to low stimulus contrasts and also contributes to responses to high stimulus contrasts. The P pathway appears to influence mainly the responses of V1 neurons to high stimulus contrasts. None of the cells in our sample, which included cells in all output layers of V1, appeared to receive input from only one pathway. These findings support the view that many V1 neurons integrate information about stimulus contrast carried by the LGN M and P pathways.

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The physics of visual perception

Philosophical Transactions of the Royal Society of London Series B Biological Sciences ◽

10.1098/rstb.1980.0078 ◽

1980 ◽

Vol 290 (1038) ◽

pp. 5-9 ◽

Cited By ~ 22

Keyword(s):

Visual Perception ◽

Spatial Frequency ◽

Visual System ◽

Contrast Threshold ◽

High Contrast ◽

Spatial Frequencies ◽

Band Pass ◽

High Contrast Grating ◽

Orientational Tuning

By measuring the contrast threshold for gratings of different waveform and spatial frequency, Campbell & Robson suggested in 1968 that there may be ‘channels’ tuned to different spatial frequencies. By using the technique of adapting to a high contrast grating, it was possible to measure the band-pass characteristics of these channels. Similar techniques were used to establish the orientational tuning of the channels. Reasons are put forward why it is advantageous to organize the visual system in this manner.

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Contrast and Temporal Frequency-Related Adaptation in the Pretectal Nucleus of the Optic Tract

Journal of Neurophysiology ◽

10.1152/jn.00980.2004 ◽

2005 ◽

Vol 94 (1) ◽

pp. 136-146 ◽

Cited By ~ 13

Author(s):

M. R. Ibbotson

Keyword(s):

Visual Cortex ◽

Optic Tract ◽

Gain Control ◽

Response Functions ◽

High Contrast ◽

Motion Adaptation ◽

Contrast Gain ◽

Contrast Gain Control ◽

Contrast Adaptation ◽

Contrast Response

In mammals, many cells in the retino-geniculate-cortical pathway adapt during stimulation with high contrast gratings. In the visual cortex, adaptation to high contrast images reduces sensitivity at low contrasts while only moderately affecting sensitivity at high contrasts, thus generating rightward shifts in the contrast response functions (contrast gain control). Similarly, motion adaptation at particular temporal frequencies (TFs) alters the temporal tuning properties of cortical cells. For the first time in any species, this paper investigates the influence of motion adaptation on both the contrast and TF responses of neurons in the retino-pretectal pathway by recording from direction-selective neurons in the nucleus of the optic tract (NOT) of the marsupial wallaby, Macropus eugenii. This species is of interest because its NOT receives almost all input directly from the retina, with virtually none from the visual cortex (unlike cats and primates). All NOT cells show changes in their contrast response functions after adaptation, many revealing contrast gain control. Contrast adaptation is direction-dependent, preferred directions producing the largest changes. The lack of cortical input suggests that contrast adaptation is generated independently from the cortex in the NOT or retina. Motion adaptation also produces direction-selective effects on the TF tuning of NOT neurons by shifting the location of the optimum TF. Cells that show strong adaptation to contrast also tend to show large changes in TF tuning, suggesting similar intracellular mechanisms. The data are discussed in terms of the generality of contrast adaptation across mammalian species and across unconnected brain regions within the same species.

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The Perceived Spatial Frequency, Contrast, and Orientation of Illusory Gratings

Perception ◽

10.1068/p090695 ◽

1980 ◽

Vol 9 (6) ◽

pp. 695-712 ◽

Cited By ~ 25

Author(s):

Mark A Georgeson

Keyword(s):

Spatial Frequency ◽

Temporal Frequency ◽

Interocular Transfer ◽

Contrast Threshold ◽

Supporting Evidence ◽

Uniform Field ◽

Apparent Contrast ◽

Spatial Frequencies ◽

The Matrix ◽

Matching Techniques

Illusory vertical gratings (V) and diagonal gratings (D) can be seen on a uniform field after inspection of a vertical grating. When using simultaneous and successive matching techniques the spatial frequencies of the V effect were found to be about 2 octaves below and 1–2 octaves above the adapting spatial frequency, but to be invariant with temporal frequency. At high adapting frequencies the D effect dominated, and was about 0·8 octave below the adapting spatial frequency, oriented about ±35° from vertical. The apparent contrast of V was about twice the value of the contrast threshold at its apparent spatial frequency. D effects seen during adaptation were about 60° from vertical and 3 octaves below the adapting frequency. The results are interpreted in terms of inhibition and disinhibition in an organized matrix of tuned channels, and the dominant pattern of inhibition in the matrix is inferred. Supporting evidence from neurophysiology, neuroanatomy, and psychophysics is briefly reviewed. An appendix deals with the question of interocular transfer of the aftereffect.

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Visual evoked potentials and magnocellular and parvocellular segregation

Visual Neuroscience ◽

10.1017/s0952523800174085 ◽

2000 ◽

Vol 17 (4) ◽

pp. 579-590 ◽

Cited By ~ 20

Author(s):

INGER RUDVIN ◽

ARNE VALBERG ◽

BJØRG ELISABETH KILAVIK

Keyword(s):

Evoked Potentials ◽

Visual Evoked Potentials ◽

Single Cells ◽

High Gain ◽

High Contrast ◽

Low Contrast ◽

Contrast Gain ◽

Time To Peak ◽

Contrast Response ◽

Visual Evoked

We have measured visual evoked potentials (VEPs) to luminance-modulated, square-wave alternating, 3-deg homogeneous disks for stimulus frequencies ranging from 1 Hz to 16.7 Hz. The aim of the study was to determine the range of frequencies at which we could reproduce the two-branched contrast-response (C-R) curves we had seen at 1 Hz (Valberg & Rudvin, 1997) and which we interpreted as magnocellular (MC) and parvocellular (PC) segregation. Low-contrast stimuli elicited relatively simple responses to luminance increments resulting in waveforms that may be the signatures of inputs from magnocellular channels to the visual cortex. At all frequencies, the C-R curves of the main waveforms were characterized by a steep slope at low contrasts and a leveling off at 10%–20% Michelson contrast. This was typically followed by an abrupt increase in slope at higher contrasts, giving a distinctive two-branched C-R curve. On the assumption that the low-contrast, high-gain branch reflects the responsivity of magnocellular-pathway inputs to the cortex, the high-contrast branch may be attributed to additional parvocellular activation. While a two-branched curve was maintained for frequencies up to 8 Hz, the high-contrast response was significantly compromised at 16.7 Hz, revealing a differential low-pass filtering. A model decomposing the measured VEP response into two separate C-R curves yielded a difference in sensitivity of the putative MC- and PC-mediated response that, when plotted as a function of frequency, followed a trend similar to that found for single cells. Due to temporal overlap of responses, the MC and PC contributions to the waveforms were hard to distinguish in the transient VEP. However, curves of time-to-peak (delay) as a function of contrast often went through a minimum before the high-contrast gain increase of the corresponding C-R curve, supporting the notion of a recruitment of new cell ensembles in the transition from low to high contrasts.

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Spatial attention modulates steady state visually-evoked potentials in human visual cortex by multiplicative gain function.

NeuroImage ◽

10.1016/s1053-8119(09)70360-x ◽

2009 ◽

Vol 47 ◽

pp. S66

Author(s):

T.Z. Lauritzen ◽

A.R. Wade

Keyword(s):

Visual Cortex ◽

Steady State ◽

Evoked Potentials ◽

Spatial Attention ◽

Visually Evoked Potentials ◽

Gain Function ◽

Human Visual Cortex

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Adaptive Integration in the Visual Cortex by Depressing Recurrent Cortical Circuits

Neural Computation ◽

10.1162/neco.2008.06-07-546 ◽

2008 ◽

Vol 20 (7) ◽

pp. 1847-1872 ◽

Cited By ~ 24

Author(s):

Mark C. W. van Rossum ◽

Matthijs A. A. van der Meer ◽

Dengke Xiao ◽

Mike W. Oram

Keyword(s):

Visual Cortex ◽

Physiological Data ◽

High Contrast ◽

Cortical Circuits ◽

Response Latencies ◽

Low Contrast ◽

Visual Areas ◽

Higher Visual Areas ◽

Recurrent Connections

Neurons in the visual cortex receive a large amount of input from recurrent connections, yet the functional role of these connections remains unclear. Here we explore networks with strong recurrence in a computational model and show that short-term depression of the synapses in the recurrent loops implements an adaptive filter. This allows the visual system to respond reliably to deteriorated stimuli yet quickly to high-quality stimuli. For low-contrast stimuli, the model predicts long response latencies, whereas latencies are short for high-contrast stimuli. This is consistent with physiological data showing that in higher visual areas, latencies can increase more than 100 ms at low contrast compared to high contrast. Moreover, when presented with briefly flashed stimuli, the model predicts stereotypical responses that outlast the stimulus, again consistent with physiological findings. The adaptive properties of the model suggest that the abundant recurrent connections found in visual cortex serve to adapt the network's time constant in accordance with the stimulus and normalizes neuronal signals such that processing is as fast as possible while maintaining reliability.

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