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Chih-Yang Chen, Alla Ignashchenkova, Ziad Hafed; Neuronal signatures of covert visual attention prior to microsaccades. Journal of Vision 2015;15(12):19. doi: 10.1167/15.12.19.
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© ARVO (1962-2015); The Authors (2016-present)
Neuronal modulations such as response gain enhancement and reductions in response variability are classically thought to reflect the allocation of covert visual attention to behaviorally relevant stimuli. Here we show that these neuronal signatures of attention can occur without any attentional task. In six different monkeys and two different brain areas classically implicated in covert visual attention, we found that classic neuronal signatures of attention occur if stimuli simply appear before microsaccades. We recorded 113 superior colliculus (SC) neurons of two monkeys performing simple fixation, while we presented vertical sine-wave gratings (2.2 cpd; 5-80% contrast) in the neurons’ peripheral response fields (RF’s). We analyzed mean visual activity 50-150 ms after grating onset and separated trials based on whether such onset happened without (baseline) or < 100 ms before microsaccades. We also analyzed 37 SC neurons from two more monkeys, and 36 frontal eye field (FEF) neurons from yet two more monkeys. For the latter four monkeys, the RF stimulus was a small spot as part of a subsequent discrimination task. In all six monkeys, we found robust pre-microsaccadic enhancement of response gain. Moreover, in the first two monkeys, we analyzed contrast sensitivity, fano factor (to assess neuronal variability), and ROC discriminability (between baseline and microsaccade trials). All analyses revealed modulations that are classic signatures of covert visual attention (e.g. reductions in fano factor and increases in ROC discriminability), but without attentional task requirements. Moreover, neurons with sustained visual responses exhibited sustained elevations in response gain and sustained reductions in fano factor, simply when stimuli appeared before microsaccades, and again without any attentional task. Our results suggest that there is an obligatory link between pre-motor processes and neuronal or behavioral (Hafed, Neuron, 2013) signatures of selective visual processing, even when such pre-motor processes are associated with seemingly “irrelevant” microsaccades.
Meeting abstract presented at VSS 2015
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