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Task difficulty modulates the activity of specific neuronal populations in primary visual cortex

Abstract

Spatial attention enhances our ability to detect stimuli at restricted regions of the visual field. This enhancement is thought to depend on the difficulty of the task being performed, but the underlying neuronal mechanisms for this dependency remain largely unknown. We found that task difficulty modulates neuronal firing rate at the earliest stages of cortical visual processing (area V1) in monkey (Macaca mulatta). These modulations were spatially specific: increasing task difficulty enhanced V1 neuronal firing rate at the focus of attention and suppressed it in regions surrounding the focus. Moreover, we found that response enhancement and suppression are mediated by distinct populations of neurons that differ in direction selectivity, spike width, interspike-interval distribution and contrast sensitivity. Our results provide strong support for center-surround models of spatial attention and suggest that task difficulty modulates the activity of specific populations of neurons in the primary visual cortex.

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Figure 1: Behavioral task and attentional response ratios measured in V1 single cells during hard and easy tasks.
Figure 2: Examples of two V1 cells whose responses were modulated by task difficulty and spatial attention.
Figure 3: Spatial attention and task difficulty modulations of V1 visual responses.
Figure 4: Modulation by task difficulty in V1 cells.
Figure 5: Response modulations to spatial attention and task difficulty are correlated with the direction selectivity, spike width, interspike interval and contrast sensitivity of the cell.
Figure 6: Response properties that distinguish V1 cells classified as difficulty suppressed (summed difficulty ratio < 0), difficulty enhanced (summed difficulty ratio > 0) and nonmodulated (no significant modulation by spatial attention as defined in Fig. 1c).
Figure 7: The magnitude of the visual responses was correlated with the level of task difficulty.

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Acknowledgements

The research was supported by NIH EY14345 (J.-M.A.), MH-64024 (H.A.S.), The Research Foundation at the SUNY College of Optometry (J.-M.A.), The Barrow Neurological Foundation (S.M.-C. and S.L.M.), NSF 0643306 (S.M.-C.), the Science Foundation Arizona (S.L.M.) and Arizona Biomedical Research Commission 07-102 (S.M.-C.) and 06-083 (S.L.M.).

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Correspondence to Jose-Manuel Alonso.

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Chen, Y., Martinez-Conde, S., Macknik, S. et al. Task difficulty modulates the activity of specific neuronal populations in primary visual cortex. Nat Neurosci 11, 974–982 (2008). https://doi.org/10.1038/nn.2147

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