Prof. N. Busch - Lateralized α oscillations in perception, attention, & short-term memory

Talk at the Leibniz Research Centre for Working Environment and Human Factors given by Prof. Niko Busch (Universität Münster) on February 27, 2024.
Abstract: The alpha-rhythm is the most prominent brain rhythm in human EEG, with
a frequency of approximately 10 Hz. States of strong alpha power are thought to
reflect a state of physiological inhibition, as indicated by reduced firing rates. This can
occur either spontaneously or in response to a task that requires selective inhibition
of task-irrelevant or distracting information, corresponding to the spotlight of
attention. I will present a series of experiments investigating the role of alpha band
lateralization, that is, the relative distribution of inhibition and excitability between
the two cortical hemispheres. Specifically, we found that spontaneous alpha
lateralization biases perception, such that the subjective contrast of Gabor patches is
amplified in the more excitable hemisphere. Furthermore, we found that alpha
lateralization can be evoked by exogenous cues. Interestingly, alpha lateralization
reflected only early, short-lived attentional capture at the cued location but not the
subsequent, long-lasting attentional reorienting towards non-cued locations
(inhibition of return). Finally, we studied alpha lateralization and contralateral delay
activity in visual short-term memory. When the eyes move during memory
maintenance, do these lateralized signals primarily reflect the retinotopic location of
the memoranda before the saccade, or their spatiotopic location? We found that
contralateral delay activity (CDA) reflects memory representations coded in
retinotopic coordinates, whereas alpha lateralization reflects a memory-unspecific
screen center bias. Overall, these studies confirmed the link between alpha
lateralization and excitability but also showed that the direction of lateralization can
be decoupled from the locus of attention.