Induced and Evoked Human Electrophysiological Correlates of Visual Working Memory Set-Size Effects at Encoding

The ability to encode, store, and retrieve visually presented objects is referred to as visual working memory (VWM). Although crucial for many cognitive processes, previous research reveals that VWM strictly capacity limited. This capacity limitation is behaviorally observable in the set size effect: the ability to successfully report items in VWM asymptotes at a small number of items. Research into the neural correlates of set size effects and VWM capacity limits in general largely focus on the maintenance period of VWM. However, we previously reported that neural resources allocated to individual items during VWM encoding correspond to successful VWM performance. Here we expand on those findings by investigating neural correlates of set size during VWM encoding. We hypothesized that neural signatures of encoding-related VWM capacity limitations should be differentiable as a function of set size. We tested our hypothesis using High Density Electroencephalography (HD-EEG) to analyze frequency components evoked by flickering target items in VWM displays of set size 2 or 4. We found that set size modulated the amplitude of the 1st and 2nd harmonic frequencies evoked during successful VWM encoding across frontal and occipital-parietal electrodes. Frontal sites exhibited the most robust effects for the 2nd harmonic (set size 2 > set size 4). Additionally, we found a set-size effect on the induced power of delta-band (1-4 Hz) activity (set size 2 > set size 4). These results are consistent with a capacity limited VWM resource at encoding that is distributed across to-be-remembered items in a VWM display. This resource may work in conjunction with a task-specific selection process that determines which items are to be encoded and which are to be ignored. These neural set size effects support the view that VWM capacity limitations begin with encoding related processes

Cognitive rehabilitation in normal aging and individuals with subjective cognitive decline

Item does not contain fulltextAging-related changes include declines in especially episodic memory, working memory, processing speed, and executive functions. Cognitive rehabilitation programs for healthy older adults with subjective cognitive decline consist of brain training, strategy training, and multimodal interventions. In general, these interventions show small improvements within the trained domain (near-transfer effects), but limited benefits on untrained cognitive domains or everyday functioning (far-transfer effects). Multimodal approaches might be more effective to enhance multiple cognitive domains and everyday functioning. However, the current lack of clear efficacy of cognitive rehabilitation techniques in healthy older adults might be explained by methodological shortcomings of previous studies and the notion that aging-related cognitive decline is not considered to reflect impairments. Future interventions with longer follow-up duration should therefore focus more on psychoeducation on normal cognitive aging and target self-efficacy and worrying to diminish subjective cognitive complaints