Frontoparietal anodal tDCS reduces ketamine-induced oscillopathies

Caroline Lahogue; Didier Pinault

doi:10.1515/tnsci-2020-0157

Frontoparietal anodal tDCS reduces ketamine-induced oscillopathies

Transl Neurosci. 2021 Jun 28;12(1):282-296. doi: 10.1515/tnsci-2020-0157. eCollection 2021 Jan 1.

Authors

Caroline Lahogue^{1

2

3}, Didier Pinault^{1

2

3}

Affiliations

¹ Université de Strasbourg, Strasbourg, France.
² INSERM U1114, Neuropsychologie Cognitive et Physiopathologie de la Schizophrénie, Strasbourg, France.
³ Fédération de Médecine Translationnelle de Strasbourg (FMTS), Centre de Recherche en Biomédecine de Strasbourg (CRBS), Faculté de médecine, Strasbourg, France.

Abstract

During the prodromal phase of schizophrenia with its complex and insidious clinical picture, electroencephalographic recordings detect widespread oscillation disturbances (or oscillopathies) during the wake-sleep cycle. Neural oscillations are electrobiomarkers of the connectivity state within systems. A single-systemic administration of ketamine, a non-competitive NMDA glutamate receptor antagonist, transiently reproduces the oscillopathies with a clinical picture reminiscent of the psychosis prodrome. This acute pharmacological model may help the research and development of innovative treatments against psychotic transition. Transcranial electrical stimulation is recognized as an appropriate non-invasive therapeutic modality since it can increase cognitive performance and modulate neural oscillations with little or no side effects. Therefore, our objective was to set up, in the sedated adult rat, a stimulation method that is able to normalize ketamine-induced increase in gamma-frequency (30-80 Hz) oscillations and decrease in sigma-frequency (10-17 Hz) oscillations. Unilateral and bipolar frontoparietal (FP), transcranial anodal stimulation by direct current (<+1 mA) was applied in ketamine-treated rats. A concomitant bilateral electroencephalographic recording of the parietal cortex measured the stimulation effects on its spontaneously occurring oscillations. A 5 min FP anodal tDCS immediately and quickly reduced, significantly with an intensity-effect relationship, the ketamine-induced gamma hyperactivity, and sigma hypoactivity at least in the bilateral parietal cortex. A duration effect was also recorded. The tDCS also tended to diminish the ketamine-induced delta hypoactivity. These preliminary neurophysiological findings are promising for developing a therapeutic proof-of-concept against neuropsychiatric disorders.

Keywords: NMDA receptors; delta oscillations; gamma oscillations; non-REM sleep; pentobarbital; psychosis transition; quantitative EEG; spindles; thalamus; transcranial electrical stimulation.