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Neural and functional states of working memory

PhD ceremony:G. (Güven) Kandemir, MSc
When:February 01, 2024
Supervisors:prof. dr. E.G. (Elkan) Akyürek, prof. dr. M.M. (Monicque) Lorist
Where:Academy building RUG
Faculty:Behavioural and Social Sciences
Neural and functional states of working memory

Working memory is akin to holding onto a phone-number until it’s dialled. But not all digits have the same functional role here as each digit is individually dialled while others are retained for later. Our research investigated how the shifting functional roles of memories influence our brain states, by using a unique method to study low- or activity-silent brain states. In Chapter 2, we probed memory when only one of the two memorized colours would be reported. Surprisingly, both colours, including the unnecessary one, were detectable in brain signals. Crucially, the brain states of these two colours differed, reflecting functional differences. With a similar set-up in Chapter 3 we studied memory for orientations. Importantly we asked participants to rotate the cued orientation and use only the rotation-product to judge a probe. Surprisingly, brain signals represented both the cued and the rotated memory, but not the non-rotated one. These results suggest that memories can persist in low-/activity-silent brain states even after they lose functional significance. In Chapter 4, pre-learned orientations were used to judge the tilt of a probe. Orientations were either visually shown or were cued by an auditory tone. In both cases the brain states were similar, although neural connectivity differed, as evidence indicated connections between visual and auditory regions when a tone was presented. Overall, brain states seem to change when functional roles change, but the states do more than just ‘actively guiding behaviour’ and ‘passively holding’. Different response strategies of the participants may also contribute to this.