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Andrew Heinz, Jeffery Johnson; Alpha-Band Power and the Maintenance of Information in Visual Short-Term Memory.. Journal of Vision 2016;16(12):712. doi: 10.1167/16.12.712.
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© ARVO (1962-2015); The Authors (2016-present)
Studies exploring the role of neural oscillations in cognition have revealed sustained increases in alpha-band power (ABP) during the delay period of verbal and visual short-term memory (STM) tasks. There have been various proposals regarding the functional significance of such increases, including the inhibition of task-irrelevant cortical areas, and the active retention of information in STM. The present study attempts to delineate between these two alternatives. In pursuit of this aim we recorded EEG while participants performed a delayed recall STM task. In this task, participants were required to maintain the orientation of a single Gabor patch across a brief delay. On each trial, a second, task-irrelevant Gabor, varying in terms of similarity to the remembered target, was presented mid-way through the delay. To examine the functional relevance of patterns of ABP, we used a forward encoding model of orientation tuning to calculate orientation-specific channel tuning functions (CTFs) across each delay (both before and after the distractor). We reasoned that, if the pattern of delay-period ABP observed at occipital-parietal electrode sites reflects the mnemonic information used to support performance in the recall task, item identity should be decodable from this distributed pattern both prior to and following presentation of the distractor. Contrary to this possibility, we found that although the CTF derived from the delay period prior to the distractor was selective for target identity, the CTF derived from the second, post-distractor, delay was not. Additional analyses revealed that the amplitude of the distractor-evoked response (d-ER) differed as a function of CTF amplitude and dispersion: higher amplitude d-ERs were associated with higher dispersion and lower amplitude CTFs. These findings suggest that delay-period ABP supports STM by selectively inhibiting task-irrelevant features during maintenance. Ongoing analyses are focused on teasing apart interactions between target-distractor similarity, estimated CTFs and behavior.
Meeting abstract presented at VSS 2016
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