The Dynamic Properties of a Brain Network During Spatial Working Memory Tasks in College Students With ADHD Traits

Abstract

This study investigated deficits of spatial working memory in college students with attention-deficit/hyperactivity disorder (ADHD) traits using event-related potentials (ERPs) and the spatial 2-back task. We also computed sensory-level activity using EEG data and investigated theta and alpha neural oscillations, phase-locking values (PLV), and brain networks. Based on the scores from the Adult ADHD Self-Report Scale (ASRS) and Conners' Adult ADHD Rating Scales (CAARS), an ADHD-trait group (n = 40) and a normal control group (n = 41) were selected. Participants were required to respond to whether the presented stimulus was at the same location as that presented two trials earlier. The ADHD-trait group showed significantly slower response times than the control group in the spatial 2-back task. In terms of spectrum, the ADHD-trait group showed significantly reduced theta power than the control group. In contrast, the ADHD-trait group exhibited an increased alpha power compared to the control group with the 250-1000 ms interval after stimulus onset. In terms of the PLV, the ADHD-trait group showed significantly weaker theta phase synchrony and fewer connection numbers in frontal-occipital areas than the control group. In terms of the theta brain network, the ADHD-trait group showed a significantly lower clustering coefficient and longer characteristic path length than the control group for the theta band. The present results indicate that college students with ADHD traits have deficits in spatial working memory and that these abnormal activities in neural oscillation, functional connectivity, and the network may contribute to spatial working memory deficits.

Keywords: attention deficit disorders with hyperactivity; brain oscillation; functional connectivity; graph theory; working memory.

FIGURE 1

The spatial 2-back task consists of a congruent condition, incongruent condition (left), and the stimulus presented for 500 ms (right).

FIGURE 2

Comparison of mean absolute power for theta (4–7 Hz) (A), alpha (8–12 Hz) (B) bands between the control group (red bar) and ADHD-trait group (blue bar). The ADHD-trait group exhibited a significantly lower theta power (results of the main effects of group) and higher alpha power (250–1000 ms intervals, results of a time interval × AOI × group interaction) than the control group (error bar: standard error, *p < 0.05).

FIGURE 3

Spatiotemporal pattern of TPLVs (A) and APLVs (B). Red: the control group has a significantly higher connectivity strength than the ADHD-trait group; blue: the ADHD-trait group has a significantly higher connectivity strength compared with the control group (left panels) (p < 0.05). The right panels show the time courses of the mean number of significant connections between the two groups (error bar: standard error, **p < 0.01).

FIGURE 4

Network parameters of the theta (A) and alpha (B) bands between the control (red bar) and ADHD-trait group (blue bar). (a) Clustering coefficient, (b) Characteristic path length, (c) small-world network index (error bar: standard error, **p < 0.01).