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to be associated with an imbalance of excitatory (E) (MIRECC), VA Pittsburgh Healthcare System, Pittsburgh, PA,
and inhibitory (I) neuronal activities, may underlie a USA; Western Psychiatric Hospital, Department of Psychiatry,
core pathophysiological mechanism in patients with University of Pittsburgh School of Medicine, Pittsburgh, PA,
schizophrenia. The auditory steady-state response USA. Electronic address: [email protected]
(ASSR) examined by electroencephalography (EEG) and
magnetoencephalography (MEG) has been proposed INTRODUCTION Aberrant network connectivity is a
as a potential biomarker for evaluating altered neu- core deficit in schizophrenia and may underlie many of
ral synchronization in schizophrenia. For this review, its associated cognitive deficits. Previous work in first-
we performed a comprehensive literature search for episode schizophrenia spectrum illness (FESz) suggests
papers published between 1999 and 2021 examin- preservation of working memory network function
ing ASSRs in patients with schizophrenia. Almost all during low-load conditions with dysfunction emerging
EEG-ASSR studies reported gamma-band ASSR reduc- as task complexity increases. This study assessed visual
tions, especially to 40-Hz stimuli both in power and/ network connectivity and its contribution to load-
or phase synchronization in chronic and first-episode dependent working memory impairments.
schizophrenia. In addition, similar to EEG-ASSR findings,
MEG-ASSR deficits to 80-Hz stimuli (high gamma) have METHODS Magnetoencephalography was recorded
been reported in patients with schizophrenia. More- from 35 FESz and 28 matched controls (HC) during
over, the 40-Hz ASSR is likely to be a predictor of the a lateralized change detection task. Impaired alpha
onset of schizophrenia. Notably, increased spontane- desynchronization was previously identified within bi-
ous (or ongoing) broadband (30-100 Hz) gamma power lateral dorsal occipital (Occ) regions. Here, whole-brain
has been reported during ASSR tasks, which resembles alpha-band connectivity was examined using phase-
the increased spontaneous gamma activity reported locking (PLV) and bilateral Occ as connectivity seeds.
in animal models of E/I imbalance. Further research on Load effects on connectivity were assessed across
ASSRs and evoked and spontaneous gamma oscilla- participants, and PLV modulation within networks was
tions is expected to elucidate the pathophysiology of compared between groups.
schizophrenia with translational implications.
RESULTS Occ exhibited significant load modulated
Keywords: E/I imbalance, EEG/MEG, auditory steady-state connectivity with six regions (FDR-corrected). HC ex-
response, biomarker, gamma oscillations, schizophrenia hibited PLV enhancement with load in all connections.
FESz failed to show PLV modulation between right Occ
Psychiatry and clinical neurosciences (2022), Vol. 76, No. and left inferior frontal gyrus, lateral occipito-temporal
12 (36069299) (4 citations) sulcus, and anterior intermediate parietal sulcus.
Smaller PLVs in all three network connections during
both memory load conditions were associated with
Load-dependent functional connectivity deficits increased reality distortion in FESz (FDR-corrected.)
during visual working memory in first-episode CONCLUSION: Examination of functional connectiv-
psychosis (2022) ity across the visual working memory network in
FESz revealed an inability to enhance communication
Sklar, Alfredo L; Coffman, Brian A; Longenecker, Julia M; between perceptual and executive networks in re-
Curtis, Mark; Salisbury, Dean F sponse to increasing cognitive demands. Furthermore,
the degree of network communication impairment
Western Psychiatric Hospital, Department of Psychiatry, Uni- was associated with positive symptoms. These findings
versity of Pittsburgh School of Medicine, Pittsburgh, PA, USA; provide insights into the nature of brain dysconnectiv-
Western Psychiatric Hospital, Department of Psychiatry, Uni- ity and its contribution to symptoms in early psychosis
versity of Pittsburgh School of Medicine, Pittsburgh, PA, USA; and identify potential targets for future interventions.
VISN 4 Mental Illness Research Education and Clinical Center

 ontents  Index 262
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