Quantitative EEG reveals frontal and central activity during calm memory retrieval in schizophrenia

In a finding that may reshape how clinicians think about the neural signature of calm in serious mental illness, researchers in Thailand have shown that people with schizophrenia display their strongest theta-band brain activity not while performing a demanding memory task, but while resting in a guided, internally focused state of calm. The study, published in Discover Mental Health by S. Khemthong, M. Rueankam, and W. Chatthong of the Division of Occupational Therapy at Mahidol University’s Faculty of Physical Therapy, used quantitative electroencephalography, or QEEG, to track oscillatory brain activity across three carefully controlled conditions. The results suggest that the rhythm most often associated with relaxed internal attention in the healthy brain behaves in a strikingly condition-dependent way in schizophrenia, peaking when the mind is settled and receding when executive demand rises.

Theta oscillations, neural rhythms oscillating roughly between four and eight hertz, have long interested cognitive neuroscientists because they appear reliably over frontal and central scalp regions during working memory operations, internal attention, and meditative or relaxed cognitive states. In schizophrenia, altered neural oscillations across multiple frequency bands are considered a hallmark of the cognitive and emotional dysregulation that defines the disorder, affecting everything from a patient’s ability to hold information in mind to their capacity to regulate emotional responses. Yet most previous work has examined theta dynamics during isolated tasks, such as n-back working memory paradigms or attentional control tests, leaving open the question of what happens to these rhythms when memory retrieval is embedded within a calm, internally directed state rather than a high-pressure cognitive challenge.

To address this gap, the Mahidol team recruited thirty individuals with schizophrenia and had them complete a structured memory recall task embedded within the Brain Mapping Performance protocol, an occupation-integrated framework designed to assess cognition within ecologically meaningful, therapeutically framed activities. Each participant was recorded under three distinct conditions. In the calm condition, participants kept their eyes closed while receiving guidance toward internal focus, creating a state of relaxed, inward attention. In the resting condition, participants sat with eyes open in a passive baseline. In the active memory task condition, they performed the memory recall task itself, retrieving previously learned material while their brain activity was continuously recorded.

EEG signals were captured from twelve scalp sites, but the analysis concentrated on six electrodes spanning the regions of greatest theoretical interest: the frontopolar site Fp1, the frontal-midline site Fz, the right frontal site F4, the left frontal site F7, the central-midline site Cz, and the left temporal site T3. Two quantitative measures anchored the study. The first was theta relative power, which expresses theta activity as a proportion of total EEG power at each site, providing a normalized index of how dominant the theta rhythm is relative to all other frequency bands. The second was the theta/beta ratio, a measure that compares slower theta activity against faster beta activity and has been used widely in neuropsychiatric research as an index of the balance between internally directed and externally engaged cognitive states.

The statistical results were unambiguous. A repeated-measures analysis of variance revealed that theta relative power was highest during the calm condition and decreased significantly during both the resting and memory task conditions, with the difference reaching a p-value below .001, indicating an effect unlikely to have arisen by chance. The effect was most prominent at the frontal-midline site Fz and the central site Cz, the very regions where frontal-midline theta is typically recorded during internal attention and working memory operations in healthy populations. In parallel, behavioral measures told a complementary story: the memory task condition was associated with lower accuracy and longer completion time, both reaching statistical significance at p less than .05, confirming that the active retrieval condition genuinely taxed participants’ cognitive resources. The theta/beta ratio followed the same descriptive pattern, rising during calm states and falling during active task engagement, reinforcing the interpretation that participants’ brains shifted between an internally focused mode and an externally demanding one.

The exploratory correlation analyses added a further layer of intrigue, indicating statistically meaningful associations between the EEG measures and behavioral performance, though the authors frame these analyses cautiously given the modest sample size and exploratory design. What emerges from the combined picture is a model in which frontal and central theta activity reflects a dynamic modulation between internally directed calm states and active executive processing. During calm, internally focused conditions, theta dominance rises, potentially representing a state of neural readiness in which the brain consolidates internal representations without the interference of external demands. When the memory task begins, theta dominance falls as executive networks recruit faster oscillatory activity to meet the increased cognitive load, a shift mirrored by the behavioral cost of reduced accuracy and slower performance.

For the authors, the clinical implications are the most exciting part of the story. They argue that the highest theta activity observed during calm conditions suggests that internally focused states may actually support neural readiness rather than representing mere inactivity or disengagement. If calm, internally directed attention strengthens the very oscillatory rhythms associated with memory and self-regulation in schizophrenia, then therapeutic approaches that deliberately cultivate such states, whether through guided relaxation, mindfulness-informed occupational therapy, or structured calm-memory integration protocols like the BMP, could offer a physiologically grounded pathway to improving cognitive and emotional regulation in psychiatric rehabilitation. The study’s framing within the Brain Mapping Performance protocol is particularly notable because it situates the EEG measurement not in an artificial laboratory abstraction but within an occupation-integrated paradigm that mirrors how rehabilitation is actually delivered.

The methodological rigor of the study deserves attention as well. The research received ethical approval from both the Mahidol University Central Institutional Review Board, under approval number MU-CIRB 2020/103.0708, and the Department of Mental Health Institutional Review Board, under DMH.IRB.COA 041/2563, and was conducted in accordance with the Declaration of Helsinki and its later amendments. All participants provided written informed consent before taking part. The work was supported by the Electricity Generating Authority of Thailand in 2020, and the authors declare no conflicts of interest. As a peer-reviewed, open-access publication, the article is available in full to clinicians, researchers, and the public, with an early-release version shared to provide faster access to the peer-reviewed, accepted findings ahead of the final version of record.

It is worth emphasizing what the study does and does not claim. The findings do not establish that calm states causally improve memory in schizophrenia, nor do they demonstrate that theta enhancement itself is therapeutic. With thirty participants and a within-subjects design comparing three conditions, the study is best understood as a carefully controlled characterization of theta dynamics across cognitive states in this population, providing a foundation upon which interventional studies can be built. The theta/beta ratio findings, while descriptively consistent with the theta power results, are framed as following a similar pattern rather than independently confirmed at the same statistical threshold. Nonetheless, the internal consistency between the neurophysiological and behavioral data, and the specificity of the effects to frontal and central midline sites, lend the core conclusion considerable weight.

As QEEG technology becomes more accessible and rehabilitation psychiatry increasingly seeks objective biomarkers to guide personalized intervention, studies of this kind point toward a future in which a clinician might monitor a patient’s theta dynamics in real time and adjust therapeutic activities to keep the brain in its most receptive state. The Mahidol team’s demonstration that theta power peaks precisely when patients are calm and internally focused, and declines predictably under executive load, offers both a measurable target and a compelling hypothesis: that in schizophrenia, the path to better cognitive function may run through the quiet spaces between the tasks, not just through the tasks themselves. The findings were received by the journal in February 2026, accepted at the end of July, and published on 1 August 2026, with correspondence directed to W. Chatthong at Mahidol University.