http://hopf.cns.nyu.edu/~tony/vns/readings/devalois-albrecht-thorell-1982.pdf

Spatial frequency selectivity of cells in macaque visual cortex

The effect of temporal discontinuity on visual search was assessed by presenting a display in which one item had an abrupt onset, while other items were introduced by gradually removing line segments that camouflaged them. We hypothesized that an abrupt onset in a visual display would capture visual attention, giving this item a processing advantage over items lacking an abrupt leading edge. This prediction was confirmed in Experiment 1. We designed a second experiment to ensure that this finding was due to attentional factors rather than to sensory or perceptual ones. Experiment 3 replicated Experiment 1 and demonstrated that the procedure used to avoid abrupt onset--camouflage removal--did not require a gradual waveform. Implications of these findings for theories of attention are discussed.

Abrupt visual onsets and selective attention: Evidence from visual search.

Two-dimensional spectral analysis of cortical receptive field profiles.

On the basis of measured receptive field profiles and spatial frequency tuning characteristics of simple cortical cells, it can be concluded that the representation of an image in the visual cortex must involve both spatial and spatial frequency variables. In a scheme due to Gabor, an image is represented in terms of localized symmetrical and antisymmetrical elementary signals. Both measured receptive fields and measured spatial frequency tuning curves conform closely to the functional form of Gabor elementary signals. It is argued that the visual cortex representation corresponds closely to the Gabor scheme owing to its advantages in treating the subsequent problem of pattern recognition.

Mathematical description of the responses of simple cortical cells.

We examined how attention affected the orientation tuning of 262 isolated neurons in extrastriate area V4 and 135 neurons in area V1 of two rhesus monkeys. The animals were trained to perform a delayed match-to-sample task in which oriented stimuli were presented in the receptive field of the neuron being recorded. On some trials the animals were instructed to pay attention to those stimuli, and on other trials they were instructed to pay attention to other stimuli outside the receptive field. In this way, orientation-tuning curves could be constructed from neuronal responses collected in two behavioral states: one in which those stimuli were attended by the animal and one in which those stimuli were ignored by the animal. We fit Gaussians to the neuronal responses to twelve different orientations for each behavioral state. Although attention enhanced the responses of V4 neurons (median 26% increase) and V1 neurons (median 8% increase), selectivity, as measured by the width of its orientation-tuning curve, was not systematically altered by attention. The effects of attention were consistent with a multiplicative scaling of the driven response to all orientations. We also found that attention did not cause systematic changes in the undriven activity of the neurons.

https://www.jneurosci.org/content/jneuro/19/1/431.full.pdf

Effects of Attention on Orientation-Tuning Functions of Single Neurons in Macaque Cortical Area V4

1. Post-stimulus histograms were obtained from ;sustained' and ;transient' retinal ganglion cells for receptive field plots using a light spot with square-wave modulation of intensity, and of variable intensity and area. Fundamental differences in their receptive field organization in time and space were revealed.2. In ;sustained' cells, excitation consists of ;transient' and ;sustained' components and the ratio of transient/sustained components remains constant at a given retinal locus for a wide range of intensities. The transient component becomes proportionally larger towards the periphery of the receptive field. This rule is also applicable for the inhibitory and disinhibitory surround. In ;transient' cells, however, there is no true ;sustained' component, but some cells produce a double peaked transient post-stimulus histogram at the R.F. centre when high flux stimuli are used, while others show a single peak transient response. The magnitude and shape of transient responses changes with intensity as well as with location in the receptive field.3. The sensitivity gradients of ;sustained' and ;transient' cells show consistent differences in shape. The mean slope of the sensitivity gradients of a sample of ;sustained' cells was 10 times that of a sample of ;transient' cells. The sensitivity gradient of ;sustained' cells shows a distinct surround region where the inhibitory mechanism is more sensitive, while that of ;transient' cells usually does not, owing to an extensive ;tail' on the sensitivity gradient of the centre mechanism, which overlaps the surround.4. Ricco's Law also holds for the centre mechanism of ;transient' cells. Non-linear summation occurs at supra-threshold levels, and when the surround mechanisms are involved.5. Supra-optimal stimuli give a saturation of the response in both ;transient and ;sustained' cells. This saturation is associated with a decrease of latency in ;transient' cells, but not in ;sustained' cells.6. The latency of retinal ganglion cells is determined by both stimulus and background flux. The effect of the background is negligible except at low values of stimulus flux, where its effect may be analysed primarily in terms of its effect on the incremental threshold.7. The latency to stimulation with a standard small spot (25-27') at the receptive field centre is shorter for ;sustained' cells than for ;transient' cells; this latency difference being related to the greater sensitivity of the ;sustained' cells to stimuli of this size. Differences in conduction time along ;transient' and ;sustained' pathways to the lateral geniculate nucleus (LGN) and cortex were estimated, and it is concluded that despite the latency difference noted above, a response to a stimulus which is optimal for a ;transient' cell reaches the cortex faster than the response to a stimulus which is optimal for a ;sustained' cell.8. The above results together with previous evidence available suggest that for most stimuli, centre and surround mechanisms are activated simultaneously and algebraically summed by a single linear stage in ;sustained' cells. In ;transient' cells, although the centre excitation and surround inhibition pools are also spatially co-extensive, they summate and interact in time and space with a greater complexity.9. Differences in the receptive field organization of ;sustained' and ;transient' cells may reflect their different functional roles in vision: (1) analysis of spatial contrast and form recognition (;sustained' cells), and (2) fast detection of objects entering visual space to cause orientation responses (;transient' cells).

Receptive field organization of `sustained' and `transient' retinal ganglion cells which subserve different functional roles

Receptive field properties of cells in area 17 of the visual cortex in the cat have been studied by quantitative methods The cortical cells were classified as ‘sustained’ or ‘transient’ according to their response to a stationary, optimal bar at the receptive field centre, this being analogous to the classification of retinal ganglion cells according to their response to a stationary, optimal spot Evidence is presented that the ‘sustained/transient’ classification is independent of the ‘simple/complex’ classification ‘Sustained’ cells of both ‘simple’ and ‘complex’ types had spatial frequency tuning curves with a sharp low-frequency cut, whereas ‘transient’ cells, both ‘simple’ and ‘complex’, had tuning curves with a shallow low-frequency cut, and on average were tuned to lower spatial frequencies than ‘sustained’ cells ‘Sustained’ cells of both ‘simple’ and ‘complex’ types, had temporal frequency tuning curves with a shallow low-frequency cut, whereas ‘transient’ cells had curves with a sharp low-frequency cut, and on average were tuned to higher temporal frequencies than ‘sustained’ cells The results indicate that ‘sustained’ and ‘transient’ cortical cells retain the spatial and temporal properties of ‘sustained’ and ‘transient’ retinal ganglion cells, respectively, and thus the two groups of neurones are organised in parallel throughout the visual system, the ‘sustained’ channel providing high spatial resolution and the ‘transient’ channel, high temporal resolution

Hisako Ikeda

Papers

Receptive field organization of `sustained' and `transient' retinal ganglion cells which subserve different functional roles

Spatial and temporal properties of ‘sustained’ and ‘transient’ neurones in area 17 of the cat's visual cortex

Functional organization of the periphery effect in retinal ganglion cells.

Anatomical, electrophysiological and pigmentary aspects of vision in the bush baby: An interpretative study

Differential effects of refractive errors and receptive field organization of central and peripheral ganglion cells.