Biology subjects

Kotyusov, A. I.

Publications and source records attributed to Kotyusov, A. I..

4 recordsLinked to original sources

bioRxiv2026

One digit too many: brain rhythms and autonomic responses at the limits of working memory capacity

Physiological measures vary with working memory load, but whether they identify when demands exceed a person's working memory capacity remains unclear. We assessed neural and autonomic responses to exceeding digit span by one digit. During an adaptive digit span task, we recorded EEG, pupillometry, and photoplethysmography from 123 participants. We compared each participant's digit span (approximately 70% correct full-sequence recall) with sequences one digit longer (span+1), operationally defined as overload. Full-sequence accuracy decreased from 74.1% to 51.5%, and subjective mental demand increased. Baseline-normalized pulse wave amplitude (PWA) was lower in span+1 from the first digit through terminal retention period. PWA was lower on correctly recalled than erroneous span+1 trials. Phasic pupil responses increased across serial positions but were smaller in span+1 at late span-matched positions; responses did not differ between conditions at their final digits. Non-baseline-corrected pupil diameter was larger in span+1 before sequence onset and during terminal retention, whereas non-baseline-corrected PWA did not differ. Frontal midline theta increased with serial position and was greater during terminal retention in span+1. Alpha and beta power decreased with serial position, and differed between conditions only at late positions. Terminal beta suppression was greater on correctly recalled span+1 trials. Thus, exceeding calibrated span impaired recall without producing a common physiological breakpoint. The findings suggest that reaching this limit does not immediately lead to resource exhaustion or disengagement. Physiological responses showed shifts in timing consistent with adjustments in preparation for recall of the longer sequence, along with increased effort before and during longer sequences.

neuroscience↗

bioRxiv2025

Alpha activity during verbal working memory retention depends on the stimulus presentation mode

Previous studies of verbal working memory (WM) have reported inconsistent changes in alpha power during retention, with both increases and decreases observed. We asked whether these discrepancies arise from how stimuli are presented. Thirty adults memorized seven digits presented in four modes: Simultaneous (all digits for 2800 ms) or sequential presentations at Fast (400 ms per digit), Slow (1000 ms per digit), and Fast+delay (400 ms per digit plus a 600 ms free time in between). We analyzed EEG during encoding and a 6 s retention period in theta (4-7 Hz), alpha (8-13 Hz), and beta (18-24 Hz) frequency bands. Encoding produced parametric load-related theta increase and beta decrease, possibly reflecting growing executive control demands and motor program formation, respectively. Alpha power did not scale with load during encoding. Single trial models linked stronger encoding theta and deeper alpha suppression to better recall, whereas retention power did not predict accuracy. During retention, theta and beta were unaffected by presentation mode. Alpha power did not differ significantly when all sequential modes were grouped together compared to the simultaneous mode. However, the Fast+delay mode uniquely showed below-baseline alpha in the first half of the retention. Our findings suggest that alpha dynamics are sensitive to the temporal structure of encoding and retention periods, particularly the presence or absence of free intervals between stimulus presentations. We propose that alpha modulation during WM retention may reflect processes beyond the simple gating of irrelevant sensory information.

neuroscience↗

bioRxiv2023

Task-evoked pulse wave amplitude tracks cognitive load

Cognitive load is a crucial factor in mentally demanding activities and holds significance across various research fields. This study aimed to investigate the effectiveness of pulse wave amplitude (PWA) as a measure for tracking cognitive load and associated mental effort in comparison to heart rate (HR) during a digit span task. The data from 78 participants were included in the analyses. Participants performed a memory task in which they were asked to memorize sequences of 5, 9, or 13 digits, and a control task where they passively listened to the sequences. PWA and HR were quantified from photoplethysmography (PPG) and electrocardiography (ECG), respectively. Pupil dilation was also assessed as a measure of cognitive load. We found that PWA showed a strong suppression with increasing memory load, indicating sensitivity to cognitive load. In contrast, HR did not show significant changes with task difficulty. Moreover, when memory load exceeded the capacity of working memory, a reversal of the PWA pattern was observed, indicating cognitive overload. In this respect, changes in PWA in response to cognitive load correlated with the dynamics of pupil dilation, suggesting a potential shared underlying mechanism. Additionally, both HR and PWA demonstrated a relationship with behavioral performance, with higher task-evoked HR and lower PWA associated with better memory performance. Our findings suggest that PWA is a more sensitive measure than HR for tracking cognitive load and overload. PWA, measured through PPG, holds significant potential for practical applications in assessing cognitive load due to its ease of use and sensitivity to cognitive overload. The findings contribute to the understanding of psychophysiological indicators of cognitive load and offer insights into the use of PWA as a non-invasive measure in various contexts.

neuroscience↗

bioRxiv2022

EEG and pupillometric signatures of working memory overload

Understanding the physiological correlates of cognitive overload has implications for gauging the limits of human cognition, for developing novel methods to define cognitive overload, and for mitigating the negative outcomes associated with overload. Most previous psychophysiological studies manipulated verbal working memory load in a narrow range (an average load of 5 items). It is unclear, however, how the nervous system responds to working memory load exceeding typical capacity limits. The objective of the current study was to characterize the central and autonomic nervous system changes associated with memory overload, by means of combined recording of EEG and pupillometry. Eighty-six participants were presented with a digit span task involving the serial auditory presentation of items. Each trial consisted of sequences of either 5, 9, or 13 digits, each separated by 2 seconds. Both theta activity and pupil size, after the initial rise, expressed a pattern of a short plateau and a decrease with reaching the state of memory overload, indicating that pupil size and theta possibly have similar neural mechanisms. Based on the described above triphasic pattern of pupil size temporal dynamics, we concluded that cognitive overload causes physiological systems to reset, and to release effort. Although memory capacity limits were exceeded and effort was released (as indicated by pupil dilation), alpha continued to decrease with increasing memory load. These results suggest that associating alpha with the focus of attention and distractor suppression is not warranted.

neuroscience↗