Date: Friday 6th May
Time: 14:00-16:00
Room: Town Hall Committee Room 2
Dr. Ed Awh (University of Chicago)
"Rhythmic brain activity tracks the content and timing of online spatial representations"
Abstract:A substantial body of evidence suggests that neural activity in
the alpha frequency band (8-12 Hz) covaries with the locus of covert spatial
attention, such that attention to one visual field yields a sustained decline
in alpha power at contralateral electrode sites. In our work, we have exploited
this covariation by using an inverted encoding model to reconstruct spatial
response profiles (termed channel tuning functions, or CTFs) based on the
topography of alpha activity on the human scalp. Thus, in a task that required
the storage of locations in working memory, we observed a graded profile of
activity across spatial channels that peaked at the stored location during both
the encoding and delay periods of the task. These spatial CTFs provide an
opportunity to quantify the basic tuning properties of online spatial memories
to examine how the precision of neural representations changes with
manipulations of the probability of storage or the number of items stored. In
addition, I'll show that the same method can be used to track the locus and
timing of covert attention following the presentation of symbolic orienting
cues and during active visual search. Moreover, we demonstrate that dynamic changes
in the selectivity of spatial CTFs provide a sensitive measure of the latency
of covert orienting during visual search. These findings demonstrate the
integral role that alpha band activity plays in the online representation of
space, and provide a powerful new approach for tracking these representations
during online storage and covert orienting.Biography: Ed Awh is a professor in the Department of Psychology, The Institute for Mind and Biology, and the Grossman Institute for Neuroscience, Quantitative Biology and Human Behavior. His laboratory focuses on behavioral and neural studies of memory and attention. Dr. Awh’s lab employs psychophysics, EEG, and functional MRI to learn about the neural mechanisms underlying these basic cognitive processes and the relationship between these processes and other cognitive functions. Recent work has focused on the use of neural decoding techniques to track the contents of online memories and the locus of covert attention.
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