The effect of spatial configuration on surround suppression of contrast sensitivity

Yury Petrov; Suzanne P. McKee

doi:10.1167/6.3.4

Surround suppression of contrast sensitivity with natural scene stimuli

Journal of Vision ◽

10.1167/12.9.848 ◽

2012 ◽

Vol 12 (9) ◽

pp. 848-848

Author(s):

B. Hansen ◽

B. Richard ◽

A. Johnson ◽

D. Ellemberg

Keyword(s):

Contrast Sensitivity ◽

Natural Scene ◽

Surround Suppression

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Two expressions of “surround suppression” in V1 that arise independent of cortical mechanisms of suppression

Visual Neuroscience ◽

10.1017/s0952523807070022 ◽

2007 ◽

Vol 24 (1) ◽

pp. 99-109 ◽

Cited By ~ 26

Author(s):

CHRIS TAILBY ◽

SAMUEL G. SOLOMON ◽

JONATHAN W. PEIRCE ◽

ANDREW B. METHA

Keyword(s):

Receptive Field ◽

Spatial Configuration ◽

Ganglion Cells ◽

Single Cells ◽

Spatial Summation ◽

High Contrast ◽

Surround Suppression ◽

Stimulus Contrast ◽

Low Contrast ◽

Spatial Frequencies

The preferred stimulus size of a V1 neuron decreases with increases in stimulus contrast. It has been supposed that stimulus contrast is the primary determinant of such spatial summation in V1 cells, though the extent to which it depends on other stimulus attributes such as orientation and spatial frequency remains untested. We investigated this by recording from single cells in V1 of anaesthetized cats and monkeys, measuring size-tuning curves for high-contrast drifting gratings of optimal spatial configuration, and comparing these curves with those obtained at lower contrast or at sub-optimal orientations or spatial frequencies. For drifting gratings of optimal spatial configuration, lower contrasts produced less surround suppression resulting in increases in preferred size. High contrast gratings of sub-optimal spatial configuration produced more surround suppression than optimal low-contrast gratings, and as much or more surround suppression than optimal high-contrast gratings. For sub-optimal spatial frequencies, preferred size was similar to that for the optimal high-contrast stimulus, whereas for sub-optimal orientations, preferred size was smaller than that for the optimal high-contrast stimulus. These results indicate that, while contrast is an important determinant of spatial summation in V1, it is not the only determinant. Simulation of these experiments on a cortical receptive field modeled as a Gabor revealed that the small preferred sizes observed for non-preferred stimuli could result simply from linear filtering by the classical receptive field. Further simulations show that surround suppression in retinal ganglion cells and LGN cells can be propagated to neurons in V1, though certain properties of the surround seen in cortex indicate that it is not solely inherited from earlier stages of processing.

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Contrast sensitivity of MT receptive field centers and surrounds

Journal of Neurophysiology ◽

10.1152/jn.00165.2011 ◽

2011 ◽

Vol 106 (4) ◽

pp. 1888-1900 ◽

Cited By ~ 23

Author(s):

James M. G. Tsui ◽

Christopher C. Pack

Keyword(s):

Visual Cortex ◽

Contrast Sensitivity ◽

Receptive Fields ◽

Extrastriate Cortex ◽

Model Parameters ◽

Surround Suppression ◽

Neuronal Responses ◽

Stimulus Contrast ◽

Area Mt ◽

Complex Center

Neurons throughout the visual system have receptive fields with both excitatory and suppressive components. The latter are responsible for a phenomenon known as surround suppression, in which responses decrease as a stimulus is extended beyond a certain size. Previous work has shown that surround suppression in the primary visual cortex depends strongly on stimulus contrast. Such complex center-surround interactions are thought to relate to a variety of functions, although little is known about how they affect responses in the extrastriate visual cortex. We have therefore examined the interaction of center and surround in the middle temporal (MT) area of the macaque ( Macaca mulatta) extrastriate cortex by recording neuronal responses to stimuli of different sizes and contrasts. Our findings indicate that surround suppression in MT is highly contrast dependent, with the strongest suppression emerging unexpectedly at intermediate stimulus contrasts. These results can be explained by a simple model that takes into account the nonlinear contrast sensitivity of the neurons that provide input to MT. The model also provides a qualitative link to previous reports of a topographic organization of area MT based on clusters of neurons with differing surround suppression strength. We show that this organization can be detected in the gamma-band local field potentials (LFPs) and that the model parameters can predict the contrast sensitivity of these LFP responses. Overall our results show that surround suppression in area MT is far more common than previously suspected, highlighting the potential functional importance of the accumulation of nonlinearities along the dorsal visual pathway.

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The Effect of Nonlinear Amplitude Growth on the Speech Perception Benefits Provided by a Single-Sided Vocoder

Journal of Speech Language and Hearing Research ◽

10.1044/2018_jslhr-h-18-0001 ◽

2019 ◽

Vol 62 (3) ◽

pp. 745-757 ◽

Cited By ~ 2

Author(s):

Jessica M. Wess ◽

Joshua G. W. Bernstein

Keyword(s):

Transfer Functions ◽

Spatial Configuration ◽

Free Field ◽

Spatial Separation ◽

Compression And Expansion ◽

Interaural Difference ◽

Interaural Differences ◽

Single Sided Deafness ◽

Perceptual Separation ◽

Loudness Growth

PurposeFor listeners with single-sided deafness, a cochlear implant (CI) can improve speech understanding by giving the listener access to the ear with the better target-to-masker ratio (TMR; head shadow) or by providing interaural difference cues to facilitate the perceptual separation of concurrent talkers (squelch). CI simulations presented to listeners with normal hearing examined how these benefits could be affected by interaural differences in loudness growth in a speech-on-speech masking task.MethodExperiment 1 examined a target–masker spatial configuration where the vocoded ear had a poorer TMR than the nonvocoded ear. Experiment 2 examined the reverse configuration. Generic head-related transfer functions simulated free-field listening. Compression or expansion was applied independently to each vocoder channel (power-law exponents: 0.25, 0.5, 1, 1.5, or 2).ResultsCompression reduced the benefit provided by the vocoder ear in both experiments. There was some evidence that expansion increased squelch in Experiment 1 but reduced the benefit in Experiment 2 where the vocoder ear provided a combination of head-shadow and squelch benefits.ConclusionsThe effects of compression and expansion are interpreted in terms of envelope distortion and changes in the vocoded-ear TMR (for head shadow) or changes in perceived target–masker spatial separation (for squelch). The compression parameter is a candidate for clinical optimization to improve single-sided deafness CI outcomes.

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