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Preeti Verghese, Yee-Joon Kim, Alexander Wade; Attention selects informative neural populations. Journal of Vision 2011;11(11):221. doi: https://doi.org/10.1167/11.11.221.
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© ARVO (1962-2015); The Authors (2016-present)
Motivation: For a discrimination task, the most informative neural population has the steepest tuning curve in the region of the attribute to be discriminated. For orientation discrimination, the most informative population is tilted away from the target orientation whereas for contrast discrimination, information is highest at the target orientation although the tuning is broad. Here we used psychophysics and source-imaged EEG to determine which neural population underlies contrast and orientation discrimination.
Methods: Psychophysics: Observers performed contrast or orientation discrimination on two vertical targets, located 5° to the left and right of fixation, after adapting to a full-field grating at different orientations. Source-imaged EEG: The same static targets were presented along with a cue that indicated task type (contrast or orientation) and location of the change (left or right). Attention modulation was estimated by the response to frequency-tagged gratings within annuli that surrounded the target. To determine which neural population was selectively modulated by the task we used three different grating orientations: 0, 20 and 45°. We obtained high-density EEG data from 13 observers and estimated frequency-tagged cortical activity using a minimum norm inverse procedure combined with realistic MR-derived head models and retinotopically-mapped visual areas. Results: In the source-imaged EEG studies, attention to a spatial location clearly increased the amplitude of the response to the annulus surrounding that location. More importantly, the pattern of modulation depended on the task. For orientation discrimination, area V1 showed a sharp peak in attentional modulation in the 20° population, whereas for contrast discrimination the orientation tuning of the enhancement was more broadly tuned. Similar tuning functions for orientation and contrast discrimination, respectively, were obtained from the psychophysical adaptation studies. These findings indicate that humans attend selectively to the most informative neural population and that these populations change depending on the nature of the task.
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