# The neurophysiological basis of interindividual variability (IIV) in ADHD

> **NIH NIH R01** · UNIVERSITY OF CALIFORNIA LOS ANGELES · 2023 · $285,082

## Abstract

PROJECT SUMMARY
Increased intraindividual variability (IIV) in task performance is a robust symptom of attention deficit/hyperactivity
disorder (ADHD). However, while theoretical frameworks suggest inefficient neural processing as a potential
cause of IIV, evidence is limited because IIV is typically measured using summary statistics of behavioral
outcomes, such as response time variability (RTV). Not only are such measures limited by sparse temporal
sampling, but they also aggregate time, ignoring underlying dynamics, and limiting the specificity and thus the
translational value of IIV in ADHD. In this project, we propose that neurophysiological measures of neural
processing efficiency can be continuously derived from the oscillatory and signal properties of EEG, to track the
contribution of top-down signals (low-frequency power), network efficiency (low-frequency oscillatory small-world
index) and network interaction stability (signal complexity). These measures can be used as a continuous, within-
subject neurophysiological index of neural processing efficiency, and one that bridges summary statistics derived
from reaction times and underlying network dynamics.
To test this idea, we revisit three existing datasets (n=514) that include children and adults, with and without
ADHD, and that contain EEG and concurrent EEG and fMRI, collected during sustained attention tasks. In each
dataset, we compute continuous measures of neural efficiency based on EEG signals to, in Aim 1, differentiate
between alternate neurophysiological profiles and mechanisms of IIV in ADHD and test if these predict
performance outcomes and individual differences in symptoms. In Aim 2, we additionally test if neural
efficiency measures predict, within-subject, aberrant interactions between core attention networks and
those previously associated with ADHD – namely fronto-parietal, default-mode, ventral/dorsal attention, visual
and fronto-striatal. The goal of the present work is to establish the neurophysiological basis of IIV in ADHD, and
thus speak to putative clinical targets of IIV, differentiate between current theories of IIV, as well as to validate
EEG-based neural efficiency as an effective intermediate indicator of underlying network dynamics.

## Key facts

- **NIH application ID:** 10660737
- **Project number:** 1R01MH130731-01A1
- **Recipient organization:** UNIVERSITY OF CALIFORNIA LOS ANGELES
- **Principal Investigator:** Agatha Lenartowicz
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2023
- **Award amount:** $285,082
- **Award type:** 1
- **Project period:** 2023-06-15 → 2026-04-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10660737

## Citation

> US National Institutes of Health, RePORTER application 10660737, The neurophysiological basis of interindividual variability (IIV) in ADHD (1R01MH130731-01A1). Retrieved via AI Analytics 2026-05-25 from https://api.ai-analytics.org/grant/nih/10660737. Licensed CC0.

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