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Primary Visual Cortex as a Saliency Map: A Parameter-Free Prediction and Its Test by Behavioral Data.

Zhaoping L, Zhe L - PLoS Comput. Biol. (2015)

Bottom Line: This hypothesis has so far provided only qualitative predictions and their confirmations.A requirement for this successful prediction is a data-motivated assumption that V1 lacks neurons tuned simultaneously to color, orientation, and motion direction of visual inputs.Since evidence suggests that extrastriate cortices do have such neurons, we discuss the possibility that the extrastriate cortices play no role in guiding exogenous attention so that they can be devoted to other functions like visual decoding and endogenous attention.

View Article: PubMed Central - PubMed

Affiliation: University College London, London, United Kingdom.

ABSTRACT
It has been hypothesized that neural activities in the primary visual cortex (V1) represent a saliency map of the visual field to exogenously guide attention. This hypothesis has so far provided only qualitative predictions and their confirmations. We report this hypothesis' first quantitative prediction, derived without free parameters, and its confirmation by human behavioral data. The hypothesis provides a direct link between V1 neural responses to a visual location and the saliency of that location to guide attention exogenously. In a visual input containing many bars, one of them saliently different from all the other bars which are identical to each other, saliency at the singleton's location can be measured by the shortness of the reaction time in a visual search for singletons. The hypothesis predicts quantitatively the whole distribution of the reaction times to find a singleton unique in color, orientation, and motion direction from the reaction times to find other types of singletons. The prediction matches human reaction time data. A requirement for this successful prediction is a data-motivated assumption that V1 lacks neurons tuned simultaneously to color, orientation, and motion direction of visual inputs. Since evidence suggests that extrastriate cortices do have such neurons, we discuss the possibility that the extrastriate cortices play no role in guiding exogenous attention so that they can be devoted to other functions like visual decoding and endogenous attention.

No MeSH data available.


Schematics of the seven kinds of feature singleton scenes.Each bar is colored green or purple (of the same luminance in the behavioral experiment), tilted to the left or right from vertical by the same absolute tilt angle, moving to the left or right (indicated by an arrow pointing to left or right) by the same motion speed. Under each schematic, the non-trivial neural responses (e.g., these responses are expected to be substantially higher than the responses to the background bars) evoked by the singleton are listed. Each singleton scene here is called a purple scene (in this paper) to denote that the color of the background bars are purple. Swapping between the green and purple colors changes a purple scene into a green scene. All purple scenes are assumed to share an invariant background response distribution, so are all the green scenes. The behavioral experiment [29] randomly interleaved purple and green scenes between trials.
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pcbi.1004375.g004: Schematics of the seven kinds of feature singleton scenes.Each bar is colored green or purple (of the same luminance in the behavioral experiment), tilted to the left or right from vertical by the same absolute tilt angle, moving to the left or right (indicated by an arrow pointing to left or right) by the same motion speed. Under each schematic, the non-trivial neural responses (e.g., these responses are expected to be substantially higher than the responses to the background bars) evoked by the singleton are listed. Each singleton scene here is called a purple scene (in this paper) to denote that the color of the background bars are purple. Swapping between the green and purple colors changes a purple scene into a green scene. All purple scenes are assumed to share an invariant background response distribution, so are all the green scenes. The behavioral experiment [29] randomly interleaved purple and green scenes between trials.

Mentions: With motion direction as another feature dimension, a feature singleton in motion direction, an M singleton, is the analogy of a C or O singleton. Analogous to a CO singleton, a double-feature singleton CM or MO is unique in both color and motion direction, or in both motion direction and orientation, respectively. A triple-feature CMO singleton is unique in all the three feature dimensions. Fig 4 shows the schematics of all the seven types of singletons. Let the reaction times to find singletons M, CM, MO, and CMO be RTM, RTCM, RTMO, and RTCMO, respectively. Then the spurious equality has the following generalizations:RTCM=Pmin(RTC,RTM),(11)RTMO=Pmin(RTM,RTO),and(12)RTCMO=Pmin(RTC,RTM,RTO).(13)Each equality above holds when V1 is assumed to have no neurons, i.e., the CM, MO, CO, or CMO neurons, which are tuned to more than one feature dimension and can respond more vigorously to the corresponding double-feature (or triple-feature) singleton than it does to the corresponding singleton-feature singletons. Each equality predicts the distribution of the reaction times for a double- or triple-feature singleton from the observed reaction times for the corresponding single-feature singletons. Using data from the same observer as that in Fig 3, Fig 5 shows that other than RTCM, the predictions disagree with the behavioral observations.


Primary Visual Cortex as a Saliency Map: A Parameter-Free Prediction and Its Test by Behavioral Data.

Zhaoping L, Zhe L - PLoS Comput. Biol. (2015)

Schematics of the seven kinds of feature singleton scenes.Each bar is colored green or purple (of the same luminance in the behavioral experiment), tilted to the left or right from vertical by the same absolute tilt angle, moving to the left or right (indicated by an arrow pointing to left or right) by the same motion speed. Under each schematic, the non-trivial neural responses (e.g., these responses are expected to be substantially higher than the responses to the background bars) evoked by the singleton are listed. Each singleton scene here is called a purple scene (in this paper) to denote that the color of the background bars are purple. Swapping between the green and purple colors changes a purple scene into a green scene. All purple scenes are assumed to share an invariant background response distribution, so are all the green scenes. The behavioral experiment [29] randomly interleaved purple and green scenes between trials.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4595278&req=5

pcbi.1004375.g004: Schematics of the seven kinds of feature singleton scenes.Each bar is colored green or purple (of the same luminance in the behavioral experiment), tilted to the left or right from vertical by the same absolute tilt angle, moving to the left or right (indicated by an arrow pointing to left or right) by the same motion speed. Under each schematic, the non-trivial neural responses (e.g., these responses are expected to be substantially higher than the responses to the background bars) evoked by the singleton are listed. Each singleton scene here is called a purple scene (in this paper) to denote that the color of the background bars are purple. Swapping between the green and purple colors changes a purple scene into a green scene. All purple scenes are assumed to share an invariant background response distribution, so are all the green scenes. The behavioral experiment [29] randomly interleaved purple and green scenes between trials.
Mentions: With motion direction as another feature dimension, a feature singleton in motion direction, an M singleton, is the analogy of a C or O singleton. Analogous to a CO singleton, a double-feature singleton CM or MO is unique in both color and motion direction, or in both motion direction and orientation, respectively. A triple-feature CMO singleton is unique in all the three feature dimensions. Fig 4 shows the schematics of all the seven types of singletons. Let the reaction times to find singletons M, CM, MO, and CMO be RTM, RTCM, RTMO, and RTCMO, respectively. Then the spurious equality has the following generalizations:RTCM=Pmin(RTC,RTM),(11)RTMO=Pmin(RTM,RTO),and(12)RTCMO=Pmin(RTC,RTM,RTO).(13)Each equality above holds when V1 is assumed to have no neurons, i.e., the CM, MO, CO, or CMO neurons, which are tuned to more than one feature dimension and can respond more vigorously to the corresponding double-feature (or triple-feature) singleton than it does to the corresponding singleton-feature singletons. Each equality predicts the distribution of the reaction times for a double- or triple-feature singleton from the observed reaction times for the corresponding single-feature singletons. Using data from the same observer as that in Fig 3, Fig 5 shows that other than RTCM, the predictions disagree with the behavioral observations.

Bottom Line: This hypothesis has so far provided only qualitative predictions and their confirmations.A requirement for this successful prediction is a data-motivated assumption that V1 lacks neurons tuned simultaneously to color, orientation, and motion direction of visual inputs.Since evidence suggests that extrastriate cortices do have such neurons, we discuss the possibility that the extrastriate cortices play no role in guiding exogenous attention so that they can be devoted to other functions like visual decoding and endogenous attention.

View Article: PubMed Central - PubMed

Affiliation: University College London, London, United Kingdom.

ABSTRACT
It has been hypothesized that neural activities in the primary visual cortex (V1) represent a saliency map of the visual field to exogenously guide attention. This hypothesis has so far provided only qualitative predictions and their confirmations. We report this hypothesis' first quantitative prediction, derived without free parameters, and its confirmation by human behavioral data. The hypothesis provides a direct link between V1 neural responses to a visual location and the saliency of that location to guide attention exogenously. In a visual input containing many bars, one of them saliently different from all the other bars which are identical to each other, saliency at the singleton's location can be measured by the shortness of the reaction time in a visual search for singletons. The hypothesis predicts quantitatively the whole distribution of the reaction times to find a singleton unique in color, orientation, and motion direction from the reaction times to find other types of singletons. The prediction matches human reaction time data. A requirement for this successful prediction is a data-motivated assumption that V1 lacks neurons tuned simultaneously to color, orientation, and motion direction of visual inputs. Since evidence suggests that extrastriate cortices do have such neurons, we discuss the possibility that the extrastriate cortices play no role in guiding exogenous attention so that they can be devoted to other functions like visual decoding and endogenous attention.

No MeSH data available.