Theta:gamma phase coupling and evoked gamma activity reflect the fidelity of mental templates during memory matching in visual perception

Abstract

Top-down predictions of future events shaped by prior experience are an important control mechanism to allocate limited attentional resources more efficiently and are thought to be implemented as mental templates stored in memory. Increased evoked gamma activity and theta:gamma phase-phase coupling over parieto-occipital areas have previously been observed when mental templates meet matching visual stimuli. Here, we investigated how these signatures evolve during the formation of new mental templates and how they relate to the fidelity of such. Based on single-trial feedback, participants learned to classify target shapes as matching or mismatching with preceding cue sequences. In the end of the experiment, they were asked to freely reproduce targets as means of template fidelity. We observed fidelity-dependent increments of matching-related gamma phase locking and theta:gamma phase coupling in early visual areas around 100–200-ms poststimulus over time. Theta:gamma phase synchronization and evoked gamma activity might serve as complementary signatures of memory matching in visual perception; theta:gamma phase synchronization seemingly most important in early phases of learning and evoked gamma activity being essential for transition of mental templates into long-term memory.

Cortical and white matter substrates supporting visuospatial working memory

“…Converging evidence for the involvement of these brain regions in visuospatial working memory has been provided by functional MRI (fMRI) (LaBar et al, 1999;Pochon et al, 2001;Kwon et al, 2002;Krasnow et al, 2003;Croizé et al, 2004 (Ferreira et al, 1998;Hillary et al, 2006;Olson et al, 2006;Chase et al, 2008;Kas et al, 2011;Jeneson et al, 2012;Bowren et al, 2020). The initial processing of visuospatial information is carried out by lowerand higher-order visual areas in the occipital and temporal lobes within 200 ms after stimulus onset (Vogel and Machizawa, 2004;Agam and Sekuler, 2007;Reinhart and Nguyen, 2019;Peylo et al, 2022). Investigators have further highlighted the causal role of the medial temporal lobe in visuospatial working memory encoding and maintenance, in addition to the formation and retrieval of long-term memory (Olson et al, 2006;Axmacher et al, 2008;Jeneson et al, 2012;Suthana et al, 2015;Wu and Buckley, 2022).…”

“…We tested the following hypotheses. First, we expected that brain regions supporting memory encoding and maintenance would exhibit high-gamma amplitude enhancement as memory load increased: speci cally the visual cortex, medial temporal region, dorsolateral prefrontal cortices, and pIFG (Olson et al, 2006;Agam and Sekuler, 2007;Jeneson et al, 2012;Reinhart and Nguyen, 2019;Peylo et al, 2022;Wu and Buckley, 2022). Second, we predicted that speci c brain regions, such as the dorsolateral prefrontal cortices or pIFG, would exhibit high-gamma enhancement as task familiarity increased from trial to trial (Ferreira et al, 1998;Hillary et al, 2006;Chase et al, 2008).…”