Theta rhythm, attention and transcranial stimulation method

Abstract

Noninvasive methods of transcranial stimulation in clinical and research activity have become widely applied for the last few years. Due to the high spatial and temporal resolution, these methods allow to explore oscillatory processes that underlie important cognitive functions on a new level. In particular, researchers got an opportunity to influence rhythmic processes, which provide function of attention by these methods. By the way, stimulation of different brain zones with theta-rhythm frequency appears to be interesting, as far as oscillations of attention on this frequency reveal itself both in external activity of subject and in oscillatory activity of neurons and neural ensembles. Aim – analysis and summarize of domestic and foreign researches with usage of transcranial stimulation method to identify role of theta-rhythm in attention processes. Analysis of modern data concerning significance of theta-rhythm in organization of attention processes was performed analyzed. Different modes of transcranial stimulation methods, that allow to discover fundamental role of theta-rhythm in oscillatory activity of neural assembles, which are the base for attention mechanisms were considered. The review noted that the method of transcranial magnetic stimulation (TMS), which is based on the principle of electromagnetic induction with potential excellent temporal and sufficiently decent spatial resolution, is extensively widely used. Usually, TMS is performed with usage single-pulse, paired-pulse, or repetitive rhythmic stimulation. In current review special attention is salaried to the theta burst stimulation protocol. It was suggested that current protocol hypothesizes to influence brain plasticity and simulates the effect of theta-gamma coupling, which is to change the amplitude of the potentials at the frequency of the gamma rhythm depending on the theta wave phase. During the applying of the TMS different variants, several research methodological approaches were applied. Thus, usage of TMS may disrupt functioning in certain cortex areas , also it is possible to increase the oscillatory activity of a particular region at a particular frequency and to enhance or decrease the synchronization of remote cortical areas in a certain frequency range. These approaches may be used directly during the execution of the test task by the subjects or in the period prior the test performing. Many researches show that transcranial stimulation of some zones of cortex contributes to the achievement of better results of examinee in tests on memory and attention. This effect is most often observed while usage of stimulation with theta-rhythm frequency. Improvement of memory and attention functions has high practical meaning for wide range of activity. Understanding of regularities and mechanisms of stimulation with theta-rhythm frequency would allow to create systems and protocols of stimulation, which would effectively improve these functions for the long period.