Page 299 - MEGIN Book Of Abstracts - 2023

rant synaptic modulation associated with deficits in MEG data showed that local synaptic connections
GABAergic inhibition, excitation-inhibition balance were reduced in SZ and local inhibition correlated
and disturbances of high-frequency oscillations. Using negatively with the severity of negative symptoms. The
a computational model combined with a graded- effective connectivity between inhibitory interneurons
difficulty visual orientation discrimination paradigm, and superficial pyramidal cells predicted orientation
we demonstrate that, in SZ, perceptual performance discrimination performance within the SZ group;
is determined by the balance of excitation-inhibition consistent with graded, behaviorally relevant, disease-
in superficial cortical layers. Twenty-eight individu- related changes in local GABAergic connections. Oc-
als with a DSM-IV diagnosis of SZ, and 30 age- and cipital GABA levels were significantly reduced in SZ but
gender-matched healthy controls participated in a did not predict behavioral performance or oscillatory
psychophysics orientation discrimination task, a visual measures. These findings endorse the importance, and
grating magnetoencephalography (MEG) recording, behavioral relevance, of GABAergic synaptic discon-
and a magnetic resonance spectroscopy (MRS) scan for nection in schizophrenia that underwrites excitation-
GABA. Using a neurophysiologically informed model, inhibition balance.
we quantified group differences in GABA, gamma mea-
sures, and the predictive validity of model parameters Keywords: GABA, behavioral, dysconnection, inhibition,
for orientation discrimination in the SZ group. MEG oscillatory, schizophrenia
visual gamma frequency was reduced in SZ, with lower
peak frequency associated with more severe negative Schizophrenia bulletin (2020), Vol. 46, No. 2 (31219602) (24
symptoms. Orientation discrimination performance citations)
was impaired in SZ. Dynamic causal modeling of the

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