Abstract
Surround suppression (SS) is a phenomenon that a neuron's response to visual stimuli within the classical receptive field (cRF) is suppressed by a concurrent stimulation in the surrounding receptive field (sRF) beyond the cRF. Studies show that SS affects neuronal response contrast sensitivity in the primary visual cortex (V1). However, the underlying mechanisms remain unclear. Here, we examined SS effect on the contrast sensitivity of cats' V1 neurons with different preferred SFs using external noise-masked visual stimuli and perceptual template model (PTM) analysis at the system level. The contrast sensitivity was evaluated by the inverted threshold contrast of neurons in response to circular gratings of different contrasts in the cRF with or without an annular grating in the sRF. Our results showed that SS significantly reduced the contrast sensitivity of cats' V1 neurons. The SS-induced reduction of contrast sensitivity was not correlated with SS strength but was dependent on neuron's preferred SF, with a larger reduction for neurons with low preferred SFs than those with high preferred SFs. PTM analysis of threshold versus external noise contrast (TvC) functions indicated that SS decreased contrast sensitivity by increasing both the internal additive noise and impact of external noise for neurons with low preferred SFs, but improving only internal additive noise for neurons with high preferred SFs. Furthermore, the SS effect on the contrast-response function of low- and high-SF neurons also exhibited different mechanisms in contrast gain and response gain. Collectively, these results suggest that the mechanisms of SS effect on neuronal contrast sensitivity may depend on neuronal populations with different SFs.
Highlights
The response of a neuron to visual stimulation in the classical receptive field is generally suppressed by a costimulation in the surrounding receptive field beyond the cRF [1, 2]
To explore if the surround suppression effect on neuronal contrast sensitivity (CS) depended on the strength of the surround suppression, we examined the correlation between the CS alterations and the surround suppression index (SI) of SS neurons
We examined this possibility in the current study by comparing the SS effects on the contrast sensitivity between V1 neurons with different preferred spatial frequencies (SFs) and found that SS had a larger effect on neurons with lower SF domain than those with higher one
Summary
The response of a neuron to visual stimulation in the classical receptive field (cRF) is generally suppressed by a costimulation in the surrounding receptive field (sRF) beyond the cRF [1, 2] This phenomenon, called surround suppression (SS), is widely reported at various levels along the visual pathway in many species [3] and commonly regarded as a fundamental property of visual neurons for efficient information processing [4, 5]. A recent report showed that SS strength has a positive correlation with the preferred SFs of V1 neurons [33] These results lead to a hypothesis that the effect of SS on neuronal contrast sensitivity may depend on neuronal SFs. One goal of this study is to examine this possibility
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