The role of mirror neurons in the interpretation of actions and intentions

Abstract

The study of mirror neuron functions is an important problem of modern neurophysiology. According to the currently popular hypothesis, mirror neurons can serve as the neural basis for interpreting actions, mimicking the learning process, and imitating other people’s behavior. However, not all researchers share this view point. The aim of this study was to investigate the role of mirror neurons in interpreting the actions and intentions. The aim of the research was to study the activity of “motor” and “communicative” mirror neurons, as well as cortical interactions at the frequency of the mu rhythm in men and women when observing and reproducing the rhythm, as well as when observing and pronouncing words. Depression of mu rhythm EEG cortical interactions at the frequency on the mu-rhythm band and the results fMRT brain scanning were used as mirror neuron activity markers. The electroencephalographic study involved volunteers, practically healthy men (31) and women (34), students aged 18 to 23 years. During the preliminary examination, we used the Annett questionnaires to identify the leading hand. In the first series, the subject observed the operator’s hand and at the start memorized a five-second rhythm, then with the middle and forefinger of the dominant hand reproduced this rhythm, periodically pressing the space bar. The period of the rhythm was set by a visual stimulus (a white square with a side of 2 cm, periodically appearing for 200 ms in the center of the black screen). In the second and third series, the subject at the start memorized a fivesecond rhythm, after which he reproduced this rhythm with the fingers of his left hand, and then with the right hand. In the fourth series, the subject watched the operator who silently uttered the word “RAZ” with his lips only when the stopwatch hand on the monitor screen crossed divisions 0, 5, 10, etc. seconds. In total, the stopwatch hand made 5 revolutions. In the fifth series, the subject himself silently pronounced the word “RAZ” at the indicated times. Before performing the proposed activity and during its implementation, EEG was recorded monopolar in the frontal (F3, F4, Fz, F7, F8), central (C3, C4, Cz), temporal (T3, T4, T5, T6), parietal (P3, P4, Pz) and occipital (O1, O2) leads according to the “10-20%” system. When processing the obtained data, the maximum values of the cross-correlation functions were calculated and the spectral power was estimated for short (1.5 s), free of artifacts EEG recording segments before 3 s (“Background”) and 1.5 s (“Preparation”) until the moment of transitive action (pressing a key) or speech action and immediately after the specified event 1.5 s (“Performing an action”). In a part of the experiments in the series, observation and reproduction of the rhythm and observation and pronunciation of words allowed us to study the activity of the brain using the fMRI method. These studies involved volunteers: 20 men and 20 women, aged 19 to 27 years, university students. During the preliminary examination, using the Annett questionnaire, the leading hand was identified. The fMRI results were obtained on a SIEMENS Magnetom Verio 3 Tesla tomography. All fMRI data were pre-processed using the SPM8 package. Within each of the paradigms, pairwise comparisons were performed based on Student’s t-test and individual and group maps were obtained with a significance level of P < 0.001. All obtained statistical maps were plotted on a template T-1 image and anatomical binding of the “active” voxels to the CONN atlas was made. Our studies have shown that cognitive activity associated with the observation and reproduction of the rhythm, with the observation and pronunciation of words (See Fig. 2, 3, 5 and 6), is accompanied by depression of the mu rhythm at certain frequencies and, most often, an increase in the levels of cortical connections at the frequency of this rhythm between the central and other zones of the cortex. The nature of these changes significantly depends on gender differences, the frequency of the mu rhythm, as well as the type and stage of the performed activity (See Fig. 1 and Fig. 4). The results of fMRI scanning of the brain showed that the observation of transitive actions associated with the reproduction of a five-second rhythm and speech actions associated with the pronunciation of words is accompanied by the activation not only of those areas of the cortex where the corresponding “motor” or “communicative” mirror neurons are located, but also other zones of the associative, sensory and motor cortex, as well as the basal ganglia (See Fig. 2 and Fig. 5). The obtained data indicate that mirror neurons by themselves do not provide an understanding of actions and intentions, although they take part in these processes. It is assumed that mirror neurons are involved in mediating interactions between the prefrontal cortex, sensory and motor cortical regions, as well as storage sites of motor programs in the brain. The interaction of these structures appears to result in an understanding of actions and intentions of other people. This «mediating” function of mirror neurons allows us to understand their involvement and activity in observing, performing and mental reproducing of actions. The paper contains 6 Figures and 26 References.