Abstract
Electrophysiological recordings of brain activity show both oscillatory dynamics that typically are analyzed in the time-frequency domain to describe brain oscillatory phenomena and scale-free arrhythmic activity defined as neural noise. Recent studies consider this arrhythmic fractal dynamics of neural noise as a sensitive biomarker of a number of cognitive processes, activity of neurotransmitter systems, changes that accompany neurodegenerative and psychiatric disorders including alcohol use disorder. We tested the changes in neural noise induced by acute alcohol intoxication in the lateral septum for the entire spectrum (1–200 Hz) of local field potential signal and for frequency specific ranges (delta, theta, beta, gamma and epsilon bands). Five male Wistar rats were implanted with intracranial electrodes and local field potential signal was measured for baseline activity and activity induced by acute ethanol intoxication (2 g/kg). Change in neural noise dynamics was assessed as a change in the slope of linear regression fit of power spectral density curves in double logarithmic scale. In our study alcohol resulted in lower incline of scale-free activity in the lateral septum for high frequency range and for the whole spectrum, which is interpreted generally as increase in neural noise and change in neuronal processing in a more stochastic way initiated by the acute alcohol intoxication. At the same time, we observed decrease in neural noise for low frequency range. The observed changes may be related to the shift of the excitatory-inhibitory balance towards inhibition and changes in neurotransmission mostly in the GABAergic system. Scale-free activity was sensitive in the conditions of acute alcohol intoxication, therefore to understand its role in alcohol use disorder we need more data and studies on the underlying processes. Future studies should include simultaneous recordings and analysis of arrhythmic dynamics with the oscillatory and multiunit spiking activity in the lateral septum. It can reveal the contribution of different-scale processes in changes driven by acute alcohol intoxication and clarify the specific electrophysiological mechanisms.
Highlights
Alcohol use disorder (AUD) is a chronic relapsing disorder characterized by non-controlled alcohol consumption with periods of abstinence and relapses
Scale-free arrhythmic activity or neural noise are considered to represent different aspects of underlying processes in the brain, such as natural variability responses of neurons to stimuli (Dinstein et al, 2015), balance of excitation-inhibition, activity of specific neurotransmitter systems (Pertermann et al, 2019), adaptive gating mechanism to stabilize the response to stimuli (Daunizeau et al, 2012)
The previously prevalent point of view where increase in noise leads to decrease in quality of communication, as claimed by Shannon (1948), was expanded by several modelling studies supported by the experimental data suggesting that neural noise is beneficial for non-linear systems and can facilitate processing of information by complex neuronal networks (Kosko & Mitaim, 2003; Miller & Katz, 2010; McDonnell & Ward, 2011)
Summary
Alcohol use disorder (AUD) is a chronic relapsing disorder characterized by non-controlled alcohol consumption with periods of abstinence and relapses. AUD imposes a heavy economic burden and is limited to therapy possibilities. Despite the fact that many studies covered many aspects of alcohol dependence, there is still a gap in the integral understanding of the disease. This complexity of AUD is associated with involvement of multiple brain areas, neuronal circuits and neurotransmitter systems, which contribute to the disease at the different stages to various degrees. The key problem in the search of therapy for AUD is determining and unifying the potential targets for treatment
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