# Impact of 1-h memory tasks with different cognitive loads on ET-derived indices of neurotransmitter-system involvement in university athletes

## TL;DR

This study shows how different memory tasks affect brain function in athletes, with moderate tasks causing more cognitive fatigue and changes in a brain signal linked to serotonin.

## Contribution

The study introduces a novel application of Encephalofluctuogram Technology (ET) to explore cognitive fatigue mechanisms in athletes using memory tasks of varying difficulty.

## Key findings

- Moderate-difficulty memory tasks caused significant declines in accuracy and a reaction time pattern of slow-fast changes.
- The ET-derived S4 index, linked to serotonin, increased significantly during moderate tasks.
- S11 showed a smaller non-specific time effect, but no other ET indices were robust after correction.

## Abstract

To investigate the effects of memory tasks of different difficulty levels on the brain functional state of collegiate athletes and to explore the underlying neurophysiological mechanisms related to cognitive fatigue.

Forty-five collegiate athletes (national second-level or above) were randomly assigned to a moderate-difficulty task group, a low-difficulty task group, or a control group (n = 15 each). A three-group pre–post design was used, with ET recorded at baseline and immediately after a 1-h intervention period. Accuracy and reaction time were continuously recorded. Neurophysiological outcomes were ET-derived S-spectrum indices (S1, S2, S4, S5, S6, S7, S11, S13) obtained using Encephalofluctuogram Technology (ET). Following prior ET reports, these indices were treated as indirect, model-derived proxy measures of neurotransmitter-system involvement rather than direct neurotransmitter measurements. Data were analyzed with repeated-measures ANOVA with Group (3) × Time (2).

The moderate-difficulty task led to a significant decline in accuracy and a block-wise slow–fast pattern in reaction time (p < 0.05), whereas no significant behavioral changes were found in the low-difficulty group. The ET-derived S4 index (previously proposed to reflect serotonergic-system involvement in ET studies) showed significant within-group, between-group, and interaction effects (all p < 0.01). No other ET indices showed robust changes after multiplicity correction.

A 1-h moderate-difficulty memory task caused a progressive decline in accuracy with reaction times initially slowing and then accelerating, and was accompanied by an increase in the ET-derived S4 index alongside a smaller non-specific time effect in S11. These ET findings should be interpreted as indirect indices and are hypothesis-generating with respect to neurotransmitter mechanisms.