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Modulation of V1 spike response by temporal interval of spatiotemporal stimulus sequence.

Kim T, Kim HR, Kim K, Lee C - PLoS ONE (2012)

Bottom Line: The spike activity of single neurons of the primary visual cortex (V1) becomes more selective and reliable in response to wide-field natural scenes compared to smaller stimuli confined to the classical receptive field (RF).This stimulus configuration enabled us to examine the spatiotemporal selectivity of response modulation from a focal surround region.These results suggest that V1 neurons participate in processing spatiotemporal sequences of oriented stimuli extending outside the RF.

View Article: PubMed Central - PubMed

Affiliation: Department of Psychology, Seoul National University, Kwanak, Seoul, Korea.

ABSTRACT
The spike activity of single neurons of the primary visual cortex (V1) becomes more selective and reliable in response to wide-field natural scenes compared to smaller stimuli confined to the classical receptive field (RF). However, it is largely unknown what aspects of natural scenes increase the selectivity of V1 neurons. One hypothesis is that modulation by surround interaction is highly sensitive to small changes in spatiotemporal aspects of RF surround. Such a fine-tuned modulation would enable single neurons to hold information about spatiotemporal sequences of oriented stimuli, which extends the role of V1 neurons as a simple spatiotemporal filter confined to the RF. In the current study, we examined the hypothesis in the V1 of awake behaving monkeys, by testing whether the spike response of single V1 neurons is modulated by temporal interval of spatiotemporal stimulus sequence encompassing inside and outside the RF. We used two identical Gabor stimuli that were sequentially presented with a variable stimulus onset asynchrony (SOA): the preceding one (S1) outside the RF and the following one (S2) in the RF. This stimulus configuration enabled us to examine the spatiotemporal selectivity of response modulation from a focal surround region. Although S1 alone did not evoke spike responses, visual response to S2 was modulated for SOA in the range of tens of milliseconds. These results suggest that V1 neurons participate in processing spatiotemporal sequences of oriented stimuli extending outside the RF.

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Frequency histograms of response index for each SOA condition from 208 collinear (A), 52 parallel (B).The mean indices were 91.23±18.40 and 96.28±15.24, respectively. These means are significantly less than 100% (Wilcoxon signed-rank test, all p<10−7). The proportions of significant suppression and facilitation (black bars) were 21.24 and 3.72% (A), and 9.44 and 5.07% (B), respectively. Note that suppression was more frequent than facilitation, for both collinear and parallel configurations, but this difference was larger for collinear condition.
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pone-0047543-g007: Frequency histograms of response index for each SOA condition from 208 collinear (A), 52 parallel (B).The mean indices were 91.23±18.40 and 96.28±15.24, respectively. These means are significantly less than 100% (Wilcoxon signed-rank test, all p<10−7). The proportions of significant suppression and facilitation (black bars) were 21.24 and 3.72% (A), and 9.44 and 5.07% (B), respectively. Note that suppression was more frequent than facilitation, for both collinear and parallel configurations, but this difference was larger for collinear condition.

Mentions: The effect of S1 was quantified with a response index. For each S1, 11 SOA (0 to 100 by 10 ms) conditions were tested, and for each SOA condition, the magnitude of neural response to the S1–S2 sequence stimuli relative to the response to S2 alone was taken as the response index. Fig. 7 illustrates the overall distribution of response index for parallel (as in Fig. 3) and collinear (as in Fig. 5) S1 conditions separately. Overall, the mean response index was 91.23% for collinear and 96.28% for parallel configurations. Both of these measures are significantly less than 100% (Wilcoxon signed-rank test, p<10−7) indicating suppression in both configurations. The difference in response index between the two configurations was statistically significant (Mann-Whitney U-test, p<10−8), indicating that collinear S1 suppressed activity on average more than parallel S1. In addition, significant modulation differed with stimulus configuration; the ratio of significant suppression to facilitation was 5.71 (21.24% for suppression vs. 3.72% for facilitation) for collinear, and 1.86 (9.44% for suppression vs. 5.07% for facilitation) for parallel configurations, indicating that suppressive modulation was dominant with collinear S1. These results are consistent with previous studies that reported a strong suppression by collinear stimulus at the RF ends [10].


Modulation of V1 spike response by temporal interval of spatiotemporal stimulus sequence.

Kim T, Kim HR, Kim K, Lee C - PLoS ONE (2012)

Frequency histograms of response index for each SOA condition from 208 collinear (A), 52 parallel (B).The mean indices were 91.23±18.40 and 96.28±15.24, respectively. These means are significantly less than 100% (Wilcoxon signed-rank test, all p<10−7). The proportions of significant suppression and facilitation (black bars) were 21.24 and 3.72% (A), and 9.44 and 5.07% (B), respectively. Note that suppression was more frequent than facilitation, for both collinear and parallel configurations, but this difference was larger for collinear condition.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3472985&req=5

pone-0047543-g007: Frequency histograms of response index for each SOA condition from 208 collinear (A), 52 parallel (B).The mean indices were 91.23±18.40 and 96.28±15.24, respectively. These means are significantly less than 100% (Wilcoxon signed-rank test, all p<10−7). The proportions of significant suppression and facilitation (black bars) were 21.24 and 3.72% (A), and 9.44 and 5.07% (B), respectively. Note that suppression was more frequent than facilitation, for both collinear and parallel configurations, but this difference was larger for collinear condition.
Mentions: The effect of S1 was quantified with a response index. For each S1, 11 SOA (0 to 100 by 10 ms) conditions were tested, and for each SOA condition, the magnitude of neural response to the S1–S2 sequence stimuli relative to the response to S2 alone was taken as the response index. Fig. 7 illustrates the overall distribution of response index for parallel (as in Fig. 3) and collinear (as in Fig. 5) S1 conditions separately. Overall, the mean response index was 91.23% for collinear and 96.28% for parallel configurations. Both of these measures are significantly less than 100% (Wilcoxon signed-rank test, p<10−7) indicating suppression in both configurations. The difference in response index between the two configurations was statistically significant (Mann-Whitney U-test, p<10−8), indicating that collinear S1 suppressed activity on average more than parallel S1. In addition, significant modulation differed with stimulus configuration; the ratio of significant suppression to facilitation was 5.71 (21.24% for suppression vs. 3.72% for facilitation) for collinear, and 1.86 (9.44% for suppression vs. 5.07% for facilitation) for parallel configurations, indicating that suppressive modulation was dominant with collinear S1. These results are consistent with previous studies that reported a strong suppression by collinear stimulus at the RF ends [10].

Bottom Line: The spike activity of single neurons of the primary visual cortex (V1) becomes more selective and reliable in response to wide-field natural scenes compared to smaller stimuli confined to the classical receptive field (RF).This stimulus configuration enabled us to examine the spatiotemporal selectivity of response modulation from a focal surround region.These results suggest that V1 neurons participate in processing spatiotemporal sequences of oriented stimuli extending outside the RF.

View Article: PubMed Central - PubMed

Affiliation: Department of Psychology, Seoul National University, Kwanak, Seoul, Korea.

ABSTRACT
The spike activity of single neurons of the primary visual cortex (V1) becomes more selective and reliable in response to wide-field natural scenes compared to smaller stimuli confined to the classical receptive field (RF). However, it is largely unknown what aspects of natural scenes increase the selectivity of V1 neurons. One hypothesis is that modulation by surround interaction is highly sensitive to small changes in spatiotemporal aspects of RF surround. Such a fine-tuned modulation would enable single neurons to hold information about spatiotemporal sequences of oriented stimuli, which extends the role of V1 neurons as a simple spatiotemporal filter confined to the RF. In the current study, we examined the hypothesis in the V1 of awake behaving monkeys, by testing whether the spike response of single V1 neurons is modulated by temporal interval of spatiotemporal stimulus sequence encompassing inside and outside the RF. We used two identical Gabor stimuli that were sequentially presented with a variable stimulus onset asynchrony (SOA): the preceding one (S1) outside the RF and the following one (S2) in the RF. This stimulus configuration enabled us to examine the spatiotemporal selectivity of response modulation from a focal surround region. Although S1 alone did not evoke spike responses, visual response to S2 was modulated for SOA in the range of tens of milliseconds. These results suggest that V1 neurons participate in processing spatiotemporal sequences of oriented stimuli extending outside the RF.

Show MeSH
Related in: MedlinePlus