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What Can Tracking Fluctuations in Dozens of Sensory Neurons Tell about Selective Attention?

Murray JD, Ardid S - Front Syst Neurosci (2011)

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, Yale University New Haven, CT, USA.

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The brain possesses limited resources and utilizes selective attention as the mechanism to manage the massive influx of sensory information into the cortex... For instance, in visual discrimination or detection tasks, proper allocation of attention improves performance and shortens response times... At the neural level, there are many different effects of attention on the response of sensory neurons: receptive field shrinkages, modulation of neural synchronization and mean activity, variability reduction, interneuronal decorrelations, and more (Reynolds and Chelazzi, )... Yet few experiments have attempted to determine how attentional correlates subserve behavioral benefits (Womelsdorf et al., )... Answering the question “How does attentional correlate ‘X’ subserve behavioral benefits?” requires reliable measurement of the attentional correlate on the timescale of behavioral changes... Instead, they suggested that attention can be flexibly distributed across both hemifields and instantiated by separate neural populations with independent fluctuations... However, this conclusion does not necessarily follow from observing uncorrelated attentional fluctuations in V4... The strength of this signal reflects the neural activity pattern in the source area of attention (Figure 1)... Assuming that the source of attention is described by Figure 1A, no significant correlations in the source area could be found if the separation of the neurons encoding the locations of both stimuli were larger than the footprint of recurrent synaptic inputs... However, even if that anticorrelation exists in the source area, it would not be measurable downstream in the activity of V4 neurons because attentional modulations are negligible... As pointed out in Chakravarthi and Cavanagh, the bilateral advantage might be due to suppressive surrounds around the attentional focus in visual sensory areas... This suppressive effect may operate locally through the recruitment of inhibitory circuits, which does not affect areas in the opposite hemisphere... Manipulating the separation of stimuli near the hemifield boundary could also probe the attentional source circuits, as interneuronal correlations between V4 hemispheres at small stimulus separation could reflect interactions within the attentional circuit and the spread of spatial attention across the hemifield boundary... For this, it would be necessary to interleave a third attentional condition in the task design that would not modulate the activity of the recorded V4 neurons, e.g., attention to a different stimulus feature in a location equidistant and far apart from the other two.

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Alternative distributions of spatial attention in the two hemifields. By task design, the measure of attention in Cohen and Maunsell (2010) is intrinsically relative (e.g., more attention to the left versus right hemifield). Thus, it is not possible to distinguish whether attention within the source areas is split across hemifields (A), or instead there is a single spotlight of attention (B).
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Figure 1: Alternative distributions of spatial attention in the two hemifields. By task design, the measure of attention in Cohen and Maunsell (2010) is intrinsically relative (e.g., more attention to the left versus right hemifield). Thus, it is not possible to distinguish whether attention within the source areas is split across hemifields (A), or instead there is a single spotlight of attention (B).

Mentions: However, this conclusion does not necessarily follow from observing uncorrelated attentional fluctuations in V4. For concreteness, we present two alternative scenarios based on a single source of attention. Critically, the viability of each alternative depends on the magnitude of attentional modulation in the less-attended hemisphere, which the authors could not measure by task design. Since only the difference in attention between the two locations could be measured, it is not known whether the strength of the top-down attentional signal to the less-attended hemisphere was moderate but significant or minimal. The strength of this signal reflects the neural activity pattern in the source area of attention (Figure 1). Assuming that the source of attention is described by Figure 1A, no significant correlations in the source area could be found if the separation of the neurons encoding the locations of both stimuli were larger than the footprint of recurrent synaptic inputs. Note that importantly, correlations could arise once the separation fell within these footprints. Assuming that the source of attention is described by Figure 1B, the activity of neurons encoding the less-attended location in the source area is very low. Suppression from the neurons encoding the attended location may exist, e.g., as a result of global inhibition. However, even if that anticorrelation exists in the source area, it would not be measurable downstream in the activity of V4 neurons because attentional modulations are negligible.


What Can Tracking Fluctuations in Dozens of Sensory Neurons Tell about Selective Attention?

Murray JD, Ardid S - Front Syst Neurosci (2011)

Alternative distributions of spatial attention in the two hemifields. By task design, the measure of attention in Cohen and Maunsell (2010) is intrinsically relative (e.g., more attention to the left versus right hemifield). Thus, it is not possible to distinguish whether attention within the source areas is split across hemifields (A), or instead there is a single spotlight of attention (B).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3105251&req=5

Figure 1: Alternative distributions of spatial attention in the two hemifields. By task design, the measure of attention in Cohen and Maunsell (2010) is intrinsically relative (e.g., more attention to the left versus right hemifield). Thus, it is not possible to distinguish whether attention within the source areas is split across hemifields (A), or instead there is a single spotlight of attention (B).
Mentions: However, this conclusion does not necessarily follow from observing uncorrelated attentional fluctuations in V4. For concreteness, we present two alternative scenarios based on a single source of attention. Critically, the viability of each alternative depends on the magnitude of attentional modulation in the less-attended hemisphere, which the authors could not measure by task design. Since only the difference in attention between the two locations could be measured, it is not known whether the strength of the top-down attentional signal to the less-attended hemisphere was moderate but significant or minimal. The strength of this signal reflects the neural activity pattern in the source area of attention (Figure 1). Assuming that the source of attention is described by Figure 1A, no significant correlations in the source area could be found if the separation of the neurons encoding the locations of both stimuli were larger than the footprint of recurrent synaptic inputs. Note that importantly, correlations could arise once the separation fell within these footprints. Assuming that the source of attention is described by Figure 1B, the activity of neurons encoding the less-attended location in the source area is very low. Suppression from the neurons encoding the attended location may exist, e.g., as a result of global inhibition. However, even if that anticorrelation exists in the source area, it would not be measurable downstream in the activity of V4 neurons because attentional modulations are negligible.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, Yale University New Haven, CT, USA.

AUTOMATICALLY GENERATED EXCERPT
Please rate it.

The brain possesses limited resources and utilizes selective attention as the mechanism to manage the massive influx of sensory information into the cortex... For instance, in visual discrimination or detection tasks, proper allocation of attention improves performance and shortens response times... At the neural level, there are many different effects of attention on the response of sensory neurons: receptive field shrinkages, modulation of neural synchronization and mean activity, variability reduction, interneuronal decorrelations, and more (Reynolds and Chelazzi, )... Yet few experiments have attempted to determine how attentional correlates subserve behavioral benefits (Womelsdorf et al., )... Answering the question “How does attentional correlate ‘X’ subserve behavioral benefits?” requires reliable measurement of the attentional correlate on the timescale of behavioral changes... Instead, they suggested that attention can be flexibly distributed across both hemifields and instantiated by separate neural populations with independent fluctuations... However, this conclusion does not necessarily follow from observing uncorrelated attentional fluctuations in V4... The strength of this signal reflects the neural activity pattern in the source area of attention (Figure 1)... Assuming that the source of attention is described by Figure 1A, no significant correlations in the source area could be found if the separation of the neurons encoding the locations of both stimuli were larger than the footprint of recurrent synaptic inputs... However, even if that anticorrelation exists in the source area, it would not be measurable downstream in the activity of V4 neurons because attentional modulations are negligible... As pointed out in Chakravarthi and Cavanagh, the bilateral advantage might be due to suppressive surrounds around the attentional focus in visual sensory areas... This suppressive effect may operate locally through the recruitment of inhibitory circuits, which does not affect areas in the opposite hemisphere... Manipulating the separation of stimuli near the hemifield boundary could also probe the attentional source circuits, as interneuronal correlations between V4 hemispheres at small stimulus separation could reflect interactions within the attentional circuit and the spread of spatial attention across the hemifield boundary... For this, it would be necessary to interleave a third attentional condition in the task design that would not modulate the activity of the recorded V4 neurons, e.g., attention to a different stimulus feature in a location equidistant and far apart from the other two.

No MeSH data available.