Impact of 1-h memory tasks with different cognitive loads on ET-derived indices of neurotransmitter-system...

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.