Biology subjects

Reichert Plaska, C.

Publications and source records attributed to Reichert Plaska, C..

4 recordsLinked to original sources

bioRxiv2021

Interhemispheric Connectivity Supports Load-Dependent Working Memory Maintenance for Complex Visual Stimuli

A critical manipulation used to study the neural basis of working memory (WM) is to vary the information load at encoding followed by measurements of activity and connectivity during maintenance in the subsequent delay period. The hallmark finding is that delay period activity and connectivity increases between frontal and parietal brain regions as load is increased. Most WM studies, however, employ simple stimuli (e.g., simple shapes or letters) during encoding and utilize unfilled intervals (e.g., a blank screen or fixation cross) during the delays. In the present study, we asked how delay period activity and connectivity change during low and high load maintenance of complex stimuli. Twenty-two participants completed a modified Sternberg WM task with two or five naturalistic scenes as stimuli while scalp EEG was recorded. In each trial, the delay interval was filled with phase scrambled scenes to provide a visual perceptual control with color and spatial frequency similar to the non-scrambled scenes presented during encoding. The results showed that theta and alpha delay activity amplitude was reduced during high compared to low WM load across frontal, central, and parietal sources. Functional connectivity during the delay was assessed by phase-locking value (PLV) and revealed a network with higher connectivity during low WM load consisting of increased PLV between 1) left frontal and right posterior temporal sources in the theta and alpha bands, 2) right anterior temporal and left central sources in the alpha and lower beta bands, and 3) left anterior temporal and posterior temporal sources in the theta, alpha, and lower beta bands. These findings demonstrate a role for interhemispheric connectivity during WM maintenance of complex stimuli. We discuss significance with respect to allocation of limited attentional resources and the filtering of interference.

neuroscience↗

bioRxiv2021

Spontaneous Eye Blink Rate during the Working Memory Delay Period Predicts Task Performance

Spontaneous eye blink rate (sEBR) has been linked to attention and memory, specifically working memory (WM). sEBR is also related to striatal dopamine (DA) activity with schizophrenia and Parkinsons disease showing increases and decreases respectively in sEBR. A weakness of past studies of sEBR and WM is that correlations have been reported using blink rates taken at baseline either before or after performance of the tasks used to assess WM. The goal of the present study was to understand how fluctuations in sEBR during different phases of a visual WM task predict task accuracy. In two experiments, with recordings of sEBR collected inside and outside of a magnetic resonance imaging bore, we observed sEBR to be positively correlated with WM task accuracy during the WM delay period. We also found task-related modulation of sEBR, including higher sEBR during the delay period compared to rest, and lower sEBR during task phases (e.g., stimulus encoding) that place demands on visual attention. These results provide further evidence that sEBR could be an important predictor of WM task performance with the changes during the delay period suggesting a role in WM maintenance. The relationship of sEBR to DA activity and WM maintenance is discussed.

neuroscience↗

bioRxiv2020

A Simultaneous EEG-fMRI Study of Thalamic Load-Dependent Working Memory Delay Period Activity

Working memory (WM) is an essential component of executive functions which depend on maintaining task-related information online for brief periods in both the presence and absence of interfering stimuli. Active maintenance occurs during the WM delay period, the time between stimulus encoding and subsequent retrieval. Previous studies have extensively documented prefrontal (PFC) and posterior parietal (PPC) cortex activity during the WM delay period, but the role of subcortical structures including the thalamus remains to be fully elucidated, especially in humans. Using simultaneous EEG-fMRI, we investigated the role of the thalamus during the WM delay period following low and high memory load encoding. During the delay, participants passively viewed scrambled images containing similar color and spatial frequency to serve as a perceptual baseline. Using individual fMRI-weighted source analyses centered around delay period onset, the effects of increased and decreased memory load on maintenance were observed bilaterally in thalamus with higher source activity evoked during low compared to high load maintenance. The main finding that thalamic activation was attenuated during high compared to low load maintenance suggesting a sensory filtering role for thalamus during consolidation of stimuli in WM where the highest evoked activity occurs when fewer stimuli need to be maintained in the presence of interfering perceptual stimuli during the delay. The results support the idea that the thalamus plays a role in short-term memory maintenance by regulating processing of interfering stimuli.

neuroscience↗

bioRxiv2019

Does rehearsal benefit visual memory? The role of semantic associations in the maintenance of intact and phase scrambled scenes.

Rehearsal during working memory (WM) maintenance facilitates retrieval. Less is known about how rehearsal modulates WM delay activity. In the present study, 44 participants completed a Sternberg Task with either intact novel scenes or phase-scrambled scenes, which had similar color and spatial frequency but lacked semantic content. During each condition participants generated a descriptive label and covertly rehearsed or suppressed (repeated "the") during the delay. This was easy in the former but more difficult in the later condition where scenes lacked semantic content. Behavioral performance and EEG delay activity was analyzed as a function of maintenance strategy. Performance during WM revealed a benefit of rehearsal for phase-scrambled but not intact scenes. Examination of the absolute amplitude revealed three underlying sources of activity for rehearsal, including the left anterior temporal (TAL), left and midline parietal regions. Increases in alpha and theta activity in TAL were correlated with improvement in performance on WM with rehearsal only when labeling was not automatic (i.e. phase-scrambled scenes), which may reflect differences in labeling and rehearsal (i.e. semantic associations vs. shallow labels). We conclude that rehearsal only benefits memory for visual stimuli that lack semantic information, and that this is correlated with changes in alpha and theta rhythms.

neuroscience↗