Attention Narrows Position Tuning of Population Responses in V1

Abstract

When attention is directed to a region of space, visual resolution at that location flexibly adapts, becoming sharper to resolve fine-scale details or coarser to reflect large-scale texture and surface properties. By what mechanism does attention improve spatial resolution? An improved signal-to-noise ratio (SNR) at the attended location contributes, because of retinotopically specific signal gain. Additionally, attention could sharpen position tuning at the neural population level, so that adjacent objects activate more distinct regions of the visual cortex. A dual mechanism involving both signal gain and sharpened position tuning would be highly efficient at improving visual resolution, but there is no direct evidence that attention can narrow the position tuning of population responses. Here, we compared the spatial spread of the fMRI BOLD response for attended versus ignored stimuli. The activity produced by adjacent stimuli overlapped less when subjects were attending at their locations versus attending elsewhere, despite a stronger peak response with attention. Our results show that even as early as primary visual cortex (V1), spatially directed attention narrows the tuning of population-coded position representations.

State-dependent attention modulation of human primary visual cortex: A high density ERP study

“…Moreover, previous results showed that attention allocation not only caused signal enhancement in the calcarine cortex (Desimone and Duncan, 1995;, but also tuned receptive fields of neurons in V1, eventually leading to a sharpening of the spatial coding of attended visual stimuli (Fischer and Whitney, 2009). In light of these findings, our new ERP results for the C1 suggest that the primary feature or process that may be affected concurrently by load and affect is the actual perceptual encoding of the spatial position of the distractor stimulus shown in the upper visual field.…”

Negative affective state mimics effects of perceptual load on spatial perception.

“…In this framework, under LL (hence when some attentional capacity is left over), the peripheral stimuli might elicit stronger activations in early visual cortex, including in V1 (Rauss et al, 2009;Rees et al, 1997;Rossi & Pourtois, 2012;Schwartz et al, 2005). In this area, attention had been previously shown to boost signal strength and sharpen position tuning (Fischer & Whitney, 2009), eventually enhancing spatial resolution (Carrasco & Yeshurun, 2009;Yeshurun & Carrasco, 1998). By comparison, under HL, given that the residual attentional capacity is reliably reduced (Lavie, 2005), early visual responses are also significantly decreased (see Rauss et al, 2009;Schwartz et al, 2005 for converging evidence of an early modulation of V1 using a similar task), and spatial resolution eventually decreased.…”

Spatiotopic coding and remapping in humans

“…Directing attention to the fovea boosts the response to stimuli near the attended target, while suppressing that to irrelevant stimuli distant from the attended location. The effect of attention can even reshape and shift the receptive fields (RFs) of single cells in monkey's MT [37] and in human V1 [38]. Is attention also instrumental in building spatiotopic selectivity?…”