Changes in EEG Rhythms and Spike Activity of Brainstem Dopaminergic Neurons Induced by Neurofeedback Sessions in Cats

Abstract

We examined the dynamics of the ratios of spectral power densities (SPDs) of the alpha vs theta rhythms (α/θ ratio)  of EEG and of the spiking frequency of supposedly dopaminergic (DA) neurons of the ventral tegmentum in the course of neurofeedback sessions directed toward changes in the EEG characteristics. Trainings were performed using techniques analogous to that used in neurofeedback sessions in humans. The level of the noise acoustic signal presented to the animal decreased with increase in the α/θ ratio in the occipital leads. In the control realizations, there were no dependences between the intensity of the acoustic signal and modulation of the current EEG. It was found that the animals learned, in a conditioned-reflex mode, to correlate changes in the intensity of the sound signal and power of the EEG rhythms and to control the latter; a high sound intensity was probably considered a factor of discomfort. The α/θ ratio in the course of neurofeedback sessions changed due to some increase in the SPD of the alpha EEG component and a noticeable drop in the SPD of theta oscillations. In a parallel manner with such modifications, augmentation of the spike activity of DA neurons was observed. Probable mechanisms of the involvement of the cerebral DA system in the formation of the effects of neurofeedback sessions are discussed.

Modulation of EEG Rhythms and Changes in Spike Activity of Noradrenergic Neurons of the Locus Coeruleus Related to Feedback Sessions by EEG Characteristics

“…Therefore, our experiments demonstrated that EEG-FB sessions are accompanied by moderate but rather clearly expressed intensification of the spike activity of LC NA neurons. These modifications differed from transformations of the activity of DA cells observed in the same experimental situation [5]. Statistically significant changes in the frequency of spiking of LC NA neurons was manifested at the 1st min of the action of the feedback signal, i.e., noticeably earlier (by about 1 min).…”

“…Thus, not only activation of DA neurons in the ventral tegmentum [5], but also creation of a relatively increased NA level in sufficiently extensive cerebral regions, is one of the crucial factors determining the efficacy of EEG-FB sessions. These events lead to simultaneous modification of the state of great neuronal populations related to the formation of the EEG α rhythm.…”

“…Sites of recording of neuronal activity were controlled on brain slices prepared using a routine technique. The experimental technique was described in more detail earlier [5].…”

“…As was found, an increase in the frequency of discharges generated by more than 50% of the supposedly noradrenergic (NA) neurons of the locus coeruleus (LC) was accompanied by intensification of the α rhythm in the EEG composition. In experiments on animals using the EEG-FB technique, it was found that the observed modifications of the EEG frequency composition correlated with changes in the frequency of spiking of dopaminergic (DA) brainstem neurons [5]. Analysis of the peculiarities of changes in the EEG rhythms in the course of EEG-FB sessions allowed us to postulate that the DA system is not the only system involved in the formation of the EEG-FB effects; other cerebral mediator systems modulating the activity of cortical cells and that of DA neurons in the ventral tegmentum participate intensely in this process.…”