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Poster B67, Wednesday, November 8, 3:00 – 4:15 pm, Harborview and Loch Raven Ballrooms

The ATL causally mediates the expansion of working memory capacity for famous faces

Rocco Chiou1, Matthew A. Lambon Ralph1;1University of Manchester, United Kingdom

Visual working memory (WM) is the mnemonic buffer that keeps visual information in an active state, making it accessible for high-level cognitive systems to operate on. It has been long known that WM is restrained by a capacity limit (typically at a maximum of 3 to 4 items for most individuals). In the present study, we demonstrate that (1) such capacity constraints do not hold for human faces, a type of visual stimuli crucial for social interaction and bestowing survival advantage, particularly for famous faces and (2) the right anterior temporal lobe causally mediates the facilitatory effect of famous faces on WM. In the first psychophysical experiment, participants performed a delayed-match-to-sample task, a well-established paradigm that probes WM capacity. We found that the number of colour patches remembered plateaued with less than 250-ms encoding time, replicating previous estimates of capacity limit. By contrast, the number of faces remembered continued to accumulate with more encoding time, and the rate of accumulation was more effective for famous than unknown faces. In the second transcranial magnetic stimulation experiment, we used theta-burst stimulation to investigate the neural locus that underpins the advantage of famous faces. Our stimulation target included the middle frontal gyrus (MFG), an executive region known for its role in generating top-down signal to bias WM, and the anterior temporal lobe (ATL), a semantic region known for representing face identity, as well as the vertex (control site). Results showed that ATL stimulation significantly disrupts the facilitatory effect of famous faces, whereas MFG and vertex stimulation left the effect unaffected. Our data adds crucial evidence to the understanding of the neural architecture of WM, demonstrating that this fundamental cognitive faculty depends on existing semantic knowledge about people and engages the ATL, which causally expands the WM buffer when visual information carries semantic information.

Topic Area: Meaning: Prosody, Social and Emotional Processes

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