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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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Effects of stimulus speed.This cell is the same as Fig. 5. Time courses of spike response of the cell for S1 at one RF diameter away from S2 (A) and two RF diameters away (B) conditions. Shown in each panel are mean spike density traces for S1–S2 sequence with SOA of 50 ms (blue) and 100 ms (red). Mean spike density for the S2-alone condition is also shown for comparison (black) with its 95% confidence interval (mean±2 SEM, gray shade). All these stimulus conditions, including other SOA conditions, were randomized within the same block during data collection. Note that the peak spike response to S1a–S2 sequence with SOA of 50 ms (blue trace in A) was reduced by half compared to response to S2 alone (black). Also note that the magnitude of this response is quite different from that for S1b–S2 sequence with SOA of 100 ms (red trace in B), although the apparent motion speed of these two conditions is roughly the same.
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pone-0047543-g010: Effects of stimulus speed.This cell is the same as Fig. 5. Time courses of spike response of the cell for S1 at one RF diameter away from S2 (A) and two RF diameters away (B) conditions. Shown in each panel are mean spike density traces for S1–S2 sequence with SOA of 50 ms (blue) and 100 ms (red). Mean spike density for the S2-alone condition is also shown for comparison (black) with its 95% confidence interval (mean±2 SEM, gray shade). All these stimulus conditions, including other SOA conditions, were randomized within the same block during data collection. Note that the peak spike response to S1a–S2 sequence with SOA of 50 ms (blue trace in A) was reduced by half compared to response to S2 alone (black). Also note that the magnitude of this response is quite different from that for S1b–S2 sequence with SOA of 100 ms (red trace in B), although the apparent motion speed of these two conditions is roughly the same.

Mentions: Spatiotemporally close stimulus sequences cause apparent motion, in which the temporal interval between spatially-displaced sequential targets and perceived motion speed are closely related to each other. The response to sequential stimuli inside and outside the RF has been implicated for motion processing, and a corresponding model has been proposed [40]. Thus, varying SOA means changing motion speed as well. However, it appears that SOA-dependency is not simply related to speed tuning for the following reasons. If the magnitude of the neural response to a stimulus sequence is related to motion speed as in other areas [46], the SOA associated with the peak neural response may vary proportionally to the distance between S1 and the RF, because for a given speed, a doubling of the spatial interval must be accompanied by a doubling of the temporal interval. However, it appears that this was not the case (Fig. 10). Also, the SOA-dependency, which often shows modulation of neural response at multiple SOAs appears to be not compatible with the idea of facilitation or suppression linked to linearly-scaled underestimation or overestimation of motion speed.


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

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

Effects of stimulus speed.This cell is the same as Fig. 5. Time courses of spike response of the cell for S1 at one RF diameter away from S2 (A) and two RF diameters away (B) conditions. Shown in each panel are mean spike density traces for S1–S2 sequence with SOA of 50 ms (blue) and 100 ms (red). Mean spike density for the S2-alone condition is also shown for comparison (black) with its 95% confidence interval (mean±2 SEM, gray shade). All these stimulus conditions, including other SOA conditions, were randomized within the same block during data collection. Note that the peak spike response to S1a–S2 sequence with SOA of 50 ms (blue trace in A) was reduced by half compared to response to S2 alone (black). Also note that the magnitude of this response is quite different from that for S1b–S2 sequence with SOA of 100 ms (red trace in B), although the apparent motion speed of these two conditions is roughly the same.
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Related In: Results  -  Collection

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

pone-0047543-g010: Effects of stimulus speed.This cell is the same as Fig. 5. Time courses of spike response of the cell for S1 at one RF diameter away from S2 (A) and two RF diameters away (B) conditions. Shown in each panel are mean spike density traces for S1–S2 sequence with SOA of 50 ms (blue) and 100 ms (red). Mean spike density for the S2-alone condition is also shown for comparison (black) with its 95% confidence interval (mean±2 SEM, gray shade). All these stimulus conditions, including other SOA conditions, were randomized within the same block during data collection. Note that the peak spike response to S1a–S2 sequence with SOA of 50 ms (blue trace in A) was reduced by half compared to response to S2 alone (black). Also note that the magnitude of this response is quite different from that for S1b–S2 sequence with SOA of 100 ms (red trace in B), although the apparent motion speed of these two conditions is roughly the same.
Mentions: Spatiotemporally close stimulus sequences cause apparent motion, in which the temporal interval between spatially-displaced sequential targets and perceived motion speed are closely related to each other. The response to sequential stimuli inside and outside the RF has been implicated for motion processing, and a corresponding model has been proposed [40]. Thus, varying SOA means changing motion speed as well. However, it appears that SOA-dependency is not simply related to speed tuning for the following reasons. If the magnitude of the neural response to a stimulus sequence is related to motion speed as in other areas [46], the SOA associated with the peak neural response may vary proportionally to the distance between S1 and the RF, because for a given speed, a doubling of the spatial interval must be accompanied by a doubling of the temporal interval. However, it appears that this was not the case (Fig. 10). Also, the SOA-dependency, which often shows modulation of neural response at multiple SOAs appears to be not compatible with the idea of facilitation or suppression linked to linearly-scaled underestimation or overestimation of motion speed.

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