The role of alpha rhythm in sensory input control during selective attention
Final Report Abstract
The ultimate goal of the present project was to investigate the neural systems that control selective attention, in particular the temporal dynamics of the interaction between EEG alpha oscillations, early visual processing and post-stimulus processing in higher cortical areas. To this end, we dissected these mechanisms by looking at the interactions between alpha EEG modulation, sensory gain control, and event-related potentials in the visual pathways. During the tenure of the grant, we ran experiments with a classical Posner type spatial attention design and found no correlation between alpha oscillations and steady state visual evoked potentials (SSVEPs), a marker of early visual processing. Interestingly, alpha modulations in the motor cortex were a much better predictor for reaction times compared to SSVEP and visual alpha band modulations. With a classical finger tapping experiment we found that, although visual alpha was modulated through the motor response, this had no influence on early visual processing. Further, we conducted studies that used a typical visual search design in which we found the to-be-expected alpha desynchronization and increase of SSVEP amplitudes along with an N2pc for target stimuli. Interestingly, although distractor stimuli elicited a Pd, a marker for proactive stimulus suppression, alpha exhibited greater desynchronization at electrodes contralateral to the distractor, and SSVEP amplitudes either increased or showed no difference relative to a pre-stimulus baseline. Manipulating chroma of the stimuli resulted in higher SSVEP amplitudes and bigger alpha desynchronization compared to low chroma stimuli. Another experiment looked into alpha band modulations in feature-based attention. Again, we found no correlations between SSVEP amplitude and alpha band modulations. In final experiment, we adopted a classical oddball paradigm to investigate the relation between P300, SSVEP and alpha amplitudes. Results showed that infrequent targets elicited a bigger P300, along with higher SSVEP amplitudes and more alpha desynchronization, compared to frequent targets. These findings, together with other recent findings, question the role of alpha as a neural mechanism for active (top-down) stimulus suppression and the inhibition of to-be-ignored locations or facilitation of to-be-attended stimuli/locations. Results suggest that alpha band oscillations represent a marker of general neural excitability in cortical areas that are related to the processing of a particular stimulus. We are convinced that our results of this highly successful research project will contribute significantly to a better understanding of the neural systems that underlie visual selective attention and might call into question some of the established models of the role of alpha oscillations in attention.
Publications
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Spatial Attentional Selection Modulates Early Visual Stimulus Processing Independently of Visual Alpha Modulations. Cerebral Cortex, 30(6), 3686-3703.
Gundlach, C.; Moratti, S.; Forschack, N. & Müller, M. M.
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Suppression of Unattended Features Is Independent of Task Relevance. Cerebral Cortex, 32(11), 2437-2446.
Gundlach, Christopher; Forschack, Norman & Müller, Matthias M.
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Attentional capture is modulated by stimulus saliency in visual search as evidenced by event-related potentials and alpha oscillations. Attention, Perception, & Psychophysics, 85(3), 685-704.
Forschack, Norman; Gundlach, Christopher; Hillyard, Steven & Müller, Matthias M.
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Dynamics of attentional allocation to targets and distractors during visual search. NeuroImage, 264, 119759.
Forschack, Norman; Gundlach, Christopher; Hillyard, Steven & Müller, Matthias M.
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Electrophysiological evidence for target facilitation without distractor suppression in two-stimulus search displays. Cerebral Cortex, 32(17), 3816-3828.
Forschack, Norman; Gundlach, Christopher; Hillyard, Steven & Müller, Matthias M.
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Early sensory gain control is dominated by obligatory and global feature-based attention in top-down shifts of combined spatial and feature-based attention. Cerebral Cortex, 33(19), 10286-10302.
Gundlach, Christopher; Wehle, Sebastian & Müller, Matthias M.
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Global attentional selection of visual features is not associated with selective modulation of posterior alpha‐band activity. Psychophysiology, 60(7).
Gundlach, Christopher; Forschack, Norman & Müller, Matthias M.
