Delay-period activity in frontal, parietal, and occipital cortex tracks different attractor dynamics in visual working memory

Abstract

26One important neural hallmark of working memory is persistent elevated delay-period 27 activity in frontal and parietal cortex. In human fMRI, delay-period BOLD activity in frontal and 28 parietal cortex increases monotonically with memory load and asymptotes at an individual's 29 capacity. Previous work has demonstrated that frontal and parietal delay-period activity 30 correlates with the decline in behavioral memory precision observed with increasing memory 31 load. However, because memory precision can be influenced by a variety of factors, it remains 32 unclear what cognitive processes underlie persistent activity in frontal and parietal cortex. Recent 33 psychophysical work has shown that attractor dynamics bias memory representations toward a 34 few stable representations and reduce the effects of internal noise. From this perspective, 35 imprecision in memory results from both drift towards stable attractor states and random 36 diffusion. Here we asked whether delay-period BOLD activity in frontal and parietal cortex 37 might be explained, in part, by these attractor dynamics. We analyzed data from an existing 38 experiment in which subjects performed delayed recall for line orientation, at different loads, 39 during fMRI scanning. We modeled subjects' behavior using a discrete attractor model, and 40 calculated within-subject correlation between frontal and parietal delay-period activity and 41 estimated sources of memory error (drift and diffusion). We found that although increases in 42 frontal and parietal activity were associated with increases in both diffusion and drift, diffusion 43 explained the most variance in frontal and parietal delay-period activity. In comparison, a 44 subsequent whole-brain regression analysis showed that drift rather than diffusion explained the 45 most variance in delay-period activity in lateral occipital cortex. These results provide a new 46 interpretation for the function of frontal, parietal, and occipital delay-period activity in working 47

Neurodynamic correlates for the cross-frequency coupled transcranial alternating current stimulation during working memory performance

“…Consistently, as frontal theta networks coordinate inter-regional communication (Voytek et al, 2015), tACS might engage in network communications for better working memory performance. As shown in Figure 6, the frontal-parietal-occipital connection of the tACS group was notably strengthened, and this result is consistent with previous studies on distributed frontoparieto-occipital processing stages during working memory (Halgren et al, 2002;Yu and Shim, 2017;Yu et al, 2020) and the parieto-frontal integration theory (P-FIT) (Jung and Haier, 2007), in which human intelligence is interpreted in terms of interactions within the frontal and parietal cortical regions. For example, the central executive function of working memory is involved in the frontal area, whereas the working memory Topographical distributions of the differences in nodal efficiency between pre-and post-treatment in the delta, theta, and alpha bands.…”