Limits...
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.

Show MeSH

Related in: MedlinePlus

Scatter plot of selectivity index and cortical distance.Each dot represents selectivity index (SI) for each stimulus condition and anatomical distance between the centers of S1 and S2 for that condition. Mariginal histograms are also shown. The cortical distance was estimated from the cortical magnification factor [31]. Data are combined single and multiple unit data obtained from 227 stimulus conditions (i.e., S1 positions) for 105 recording sites in 2 monkeys. Black dots and bars indicate significant SIs (69 of 227 cases, 30.40%, p<0.05), as evaluated with a bootstrapping method. The proportion was also consistent for single units alone (23 of 92 stimulus conditions, 25%) and multiple unit activitiy (46 of 135 stimulus conditions, 34.07%).The proportion of significant SI decreased with the cortical distance between S1 and S2.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC3472985&req=5

pone-0047543-g009: Scatter plot of selectivity index and cortical distance.Each dot represents selectivity index (SI) for each stimulus condition and anatomical distance between the centers of S1 and S2 for that condition. Mariginal histograms are also shown. The cortical distance was estimated from the cortical magnification factor [31]. Data are combined single and multiple unit data obtained from 227 stimulus conditions (i.e., S1 positions) for 105 recording sites in 2 monkeys. Black dots and bars indicate significant SIs (69 of 227 cases, 30.40%, p<0.05), as evaluated with a bootstrapping method. The proportion was also consistent for single units alone (23 of 92 stimulus conditions, 25%) and multiple unit activitiy (46 of 135 stimulus conditions, 34.07%).The proportion of significant SI decreased with the cortical distance between S1 and S2.

Mentions: The degree of dependence of response modulation on SOA for each S1 was quantified with SI, a numerical index of selectivity of facilitation or suppression for SOA. Overall, SI ranged from 0.002 to 0.058 (Fig. 9, right marginal histogram). To give an idea of the meaning of this index, if neural response was reduced by 30% by the S1–S2 sequence stimuli in one of 11 SOA conditions, SI would be 0.009, and if it was reduced by 30% equally in 3 of 11 SOA conditions, SI would be 0.023. Note that some cells showed near zero SI, indicating a lack of interaction with the tested S1. This is not unexpected because we used a focal surround stimulus and previous studies showed that surround interactions originate from specific regions of the surround [11], [35], and because surround interactions are evident only for a subset of V1 cells [36]. SI was computed based on the mean firing rate during an analysis time window that was chosen to include strong transient activity centered at about 100 ms after S2 onset, and its significance was judged by a bootstrapping method (see Materials and Methods). When SI was computed over moving temporal epochs of 100 ms with a step of 50 ms from −150 ms to 450 ms with respect to S2 onset, the frequency of significant SI remained low before S2 onset, began to grow, reached maximal at about 100 ms from S2 onset, and then decreased to baseline level. Thus, the time course of the frequency of significant SI resembled the time course of spiking activity evoked by S2.


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

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

Scatter plot of selectivity index and cortical distance.Each dot represents selectivity index (SI) for each stimulus condition and anatomical distance between the centers of S1 and S2 for that condition. Mariginal histograms are also shown. The cortical distance was estimated from the cortical magnification factor [31]. Data are combined single and multiple unit data obtained from 227 stimulus conditions (i.e., S1 positions) for 105 recording sites in 2 monkeys. Black dots and bars indicate significant SIs (69 of 227 cases, 30.40%, p<0.05), as evaluated with a bootstrapping method. The proportion was also consistent for single units alone (23 of 92 stimulus conditions, 25%) and multiple unit activitiy (46 of 135 stimulus conditions, 34.07%).The proportion of significant SI decreased with the cortical distance between S1 and S2.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3472985&req=5

pone-0047543-g009: Scatter plot of selectivity index and cortical distance.Each dot represents selectivity index (SI) for each stimulus condition and anatomical distance between the centers of S1 and S2 for that condition. Mariginal histograms are also shown. The cortical distance was estimated from the cortical magnification factor [31]. Data are combined single and multiple unit data obtained from 227 stimulus conditions (i.e., S1 positions) for 105 recording sites in 2 monkeys. Black dots and bars indicate significant SIs (69 of 227 cases, 30.40%, p<0.05), as evaluated with a bootstrapping method. The proportion was also consistent for single units alone (23 of 92 stimulus conditions, 25%) and multiple unit activitiy (46 of 135 stimulus conditions, 34.07%).The proportion of significant SI decreased with the cortical distance between S1 and S2.
Mentions: The degree of dependence of response modulation on SOA for each S1 was quantified with SI, a numerical index of selectivity of facilitation or suppression for SOA. Overall, SI ranged from 0.002 to 0.058 (Fig. 9, right marginal histogram). To give an idea of the meaning of this index, if neural response was reduced by 30% by the S1–S2 sequence stimuli in one of 11 SOA conditions, SI would be 0.009, and if it was reduced by 30% equally in 3 of 11 SOA conditions, SI would be 0.023. Note that some cells showed near zero SI, indicating a lack of interaction with the tested S1. This is not unexpected because we used a focal surround stimulus and previous studies showed that surround interactions originate from specific regions of the surround [11], [35], and because surround interactions are evident only for a subset of V1 cells [36]. SI was computed based on the mean firing rate during an analysis time window that was chosen to include strong transient activity centered at about 100 ms after S2 onset, and its significance was judged by a bootstrapping method (see Materials and Methods). When SI was computed over moving temporal epochs of 100 ms with a step of 50 ms from −150 ms to 450 ms with respect to S2 onset, the frequency of significant SI remained low before S2 onset, began to grow, reached maximal at about 100 ms from S2 onset, and then decreased to baseline level. Thus, the time course of the frequency of significant SI resembled the time course of spiking activity evoked by S2.

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