E. D. Petrovskii

Dynamic Mapping of the Brain in Substance-Dependent Individuals: Functional Magnetic Resonance Imaging

Functional magnetic resonance imaging can be used to study numerous brain dysfunctions, including disorders of the self, in substance-dependent individuals. The self as the sum of human concepts about oneself is regulated by the brain system close to the default mode network: the medial prefrontal cortex, posterior cingulated gyrus, and some parietal regions. However, the composition and activity of this system in mental disease, specifically, in substance addiction, are virtually not described. Our study showed that self-appraisal task in addicts activates the superior frontal cortex, cuneus, precuneus, angular gyrus, and posterior cingulated cortex. The involvement of the parietal (postcentral and supramarginal gyri) and temporal (superior temporal and Heschl’s gyri) sensory areas is diminished. Hence, published data on the involvement of the cingulate cortex and prefrontal cortex in functional regulation of the self are confirmed. Activation-deactivation patterns in the parietal and temporal regions differ significantly from the previous descriptions.

Synergetic fMRI-EEG Brain Mapping in Alpha-Rhythm Voluntary Control Mode

For the first time in neurobiology-related issues, the synergistic spatial dynamics of EEG and fMRI (BOLD phenomenon) was studied during cognitive alpha biofeedback training in the operant conditioning mode (acoustic reinforcement of alpha-rhythm development and stability). Significant changes in alpha-rhythm intensity were found in T6 electrode area (Brodmann area 37). Brodmann areas related to solving alpha-training tasks and maximally involved in the formation of new neuronal network were middle and superior temporal gyri (areas 21, 22, and 37), fusiform gyrus, inferior frontal gyrus (areas 4, 6, and 46), anterior cingulate gyrus (areas 23 and 24), cuneus, and precuneus (area 7). Wide involvement of Brodmann areas is determined by psychological architecture of alpha-rhythm generating system control that includes complex cognitive activities: decision making, retrieval of long-term memory, evaluation of the reward and control efficiency during alpha-EEG biofeedback.

EEG-fMRI Study of Alpha-Stimulation Neurobiofeedback Training Course

fMRI-EEG dynamics of brain activity in volunteers was studied during the course of EEG alpha-stimulation training (20 sessions). Twenty-three healthy men (20-35 years) were subjected to 3-fold mapping in a feedback loop (EEG alpha-rhythm biofeedback with acoustic reinforcement). This procedure was performed at the beginning, middle, and end of the course. During the first neurofeedback training session, deactivation (p<0.001) was found in the right angular gyrus, supramarginal, and superior temporal gyri, Brodmann area 39, and cerebellum. Activation (p<0.001) was observed in the medial frontal and cingulate gyri, motor areas of both hemispheres, and Brodmann area 32. During final (third) neurofeedback training session, we observed strong deactivation (p<0.05 with FDR) of zones responsible for spatial thinking and motor functions: left medial frontal and left medial temporal gyri; right postcentral, lingual, and superior frontal gyri; insula and right side of the cerebellum; and precuneus and cuneus (Brodmann areas 6, 9, 7, 31, 8, 13, and 22). Changes in the alpha wave power were most pronounced in the primary and secondary somatosensory cortex of the left hemisphere (Brodmann areas 2L and 5L).

fMRI Responses in Healthy Individuals and in Patients with Mild Depression to Presentation of Pleasant and Unpleasant Images

Patients with mild depression and apparently healthy individuals were presented images and asked to sort them into “pleasant” and “unpleasant” subsets. In both groups, the main differences between brain activation patterns during presentation of pleasant and unpleasant images were localized in the motor regions (precentral and postcentral gyrus) and in the cerebellum (p<0.05 with FWE correction). Most likely, these clusters are associated with motion (pressing a button in accordance with the instruction). According to the data of intergroup contrasts, patients with depression had less pronounced activation of frontal structures (middle frontal gyrus and other areas, including the white matter) in response to both positive and negative images (p<0.001). In healthy subjects, the response of the temporo-occipital areas (lingual and fusiform gyrus) to unpleasant stimuli was more intensive than in patients (p<0.001). This can be due to differences in the semantic image processing. Thus, in case of mild depression, the response of the amygdaloid complex, the key structure in the development in affective disorder, was not always observed. At the same time, the response of frontal and temporo-occipital regions has a certain potential as a biomarker of mild depression, although the reliability of the obtained data requires additional confirmation.

Spontaneous Changes in Functional Connectivity of Independent Components of fMRI Signal in Healthy Volunteers at Rest and in Subjects with Mild Depression

Depression is associated with changes in the pattern of interaction of cerebral networks, which can reflect both existing symptoms and compensatory processes. The study is based on analysis of resting state fMRI data from 15 patients with mild depression and 19 conventionally healthy individuals. From fMRI signal recorded at rest for 4 min, the independent components were reconstructed. The intergroup differences and dynamics of functional connectivity from the first to the second recording were analyzed. Initially, depressive patients demonstrated weaker connectivity between cerebellar declive network (CN) and left central executive network (CEN) and also sensorimotor network (SMN); left CEN and primary visual network (PVN). During the second recording, the patients demonstrated more intensive reciprocal connection of the dorsal domain of default mode network (DMN) and auditory network (AN). In healthy subjects, positive correlations of the dorsal DMN and left CEN, right CEN and CN, and negative correlation of dorsal DMN and visuospatial network weakened from the first to second record. In the depression group, the interaction of AN with PVN, the right CEN with the anterior salience network and with ventral DMN weakened. At the same time, the connectivity between SMN and CN were strengthened. The results can be interpreted as spontaneous normalization of brain activity, but no direct evidence for their relation to the improvement of depression symptoms was found.

Experience in Continuous Neurobiocontrol Using fMRI Signals from the Primary Motor Cortex Using a 1.5-T MR Tomograph

Biocontrol based on fMRI signals from the motor area of the cortex is a potential approach to restoring motor functions in poststroke states and Parkinson’s disease. The region of interest in most studies is in the secondary motor areas and the strength of the magnetic field is 3 T. We report here our studies on biocontrol using the fMRI signal from an area of the primary motor cortex associated with the operation of the right hand obtained using a 1.5-T tomograph and settings optimal for obtaining optimal images at this magnetic field strength. Subjects were 16 healthy subjects who took part in 30-min fMRI recording including 1) individual localization of the region of interest (rhythmic fist clenching test) and attempts to control its activity using 2) imaginary movements and 3) any cognitive strategy of the participant’s choice. Attempts to carry out self-control in both cases led to activation of the precentral, anterior cingulate, superior frontal, and inferior parietal gyri and Brodmann zone 6. fMRI signal maps for these tasks did not show any statistically significant differences and the activation zones showed little if any overlap with the region of interest, evidencing lack of success of sessions. The limitations of the experiments are discussed, as are factors with adverse influences on the effectiveness of biocontrol.

fMRI Response of Parietal Brain Areas to Sad Facial Stimuli in Mild Depression

fMRI markers of mild depression were revealed using standard emotional test. Patients with mild depression and healthy volunteers were asked to determine gender of subjects in photographs with different emotional expressions (neutral, surprise, disgust, confusion, anger, sadness, fear, and joy). The pattern of response to different emotions was universal in both groups and included the largest clusters in the occipital region, as well as a certain volume in the parietal lobes and posterior lateral frontal cortex. In depression group, a lack of activation in the middle cingulate gyrus (bilaterally) and in the postcentral and inferior parietal gyrus (left) in response to presentation of sad faces. For other emotion, no large clusters of intergroup contrasts significant at p<0.05 with FWE correction were revealed. The response of the middle cingulate gyrus and the left inferior parietal lobe can be considered as a potential diagnostic marker of depressive disorders and as the target for neurofeedback.

Functional Connectivity of Brain Regions According to Resting State fMRI: Differences between Healthy and Depressed Subjects and Variability of the Results

In depressed patients, changes in spontaneous brain activity, in particular, the strength of functional connectivity between different regions are observed. The data on changes in the synchrony of different regions of interest in the brain can serve as markers of depressive symptoms and as the targets for the corresponding therapy. The study involved 21 patients with mild depression and 21 healthy volunteers; by the time of second fMRI scanning, 15 and 19 subjects, respectively). The subjects underwent two 4-min sessions of resting state fMRI with 2-4 months interval between the recordings; on the basis of these data, functional connectivity between regions of interest was assessed. During the first session, depressed patients demonstrated more pronounced connection between the right frontal eye field and cerebellar area III. When the sample was restricted to subjects who underwent both fMRI sessions, depressed patients demonstrated closer relations of the right parietal operculum and cerebellar vermis area VIII. During the second recording, healthy subjects showed stronger connectivity between more than 20 frontal, temporal, and subcortical regions of interest and cerebellum area II. In healthy participants, brainstem functional interactions increased from the first to the second fMRI-recording. In depressed subjects a number of cortical areas split from left intraparietal sulcus, but the left temporal cortex became more intra-connected. The results confirm the differences in functional connectivity between depressed and healthy subjects. At the same time, attention should be paid to the variability of the data obtained.

Estimation of the Composition of the Resting State fMRI Networks in Subjects with Mild Depression and Healthy Volunteers

Depressive disorders can be associated with changes in not only interaction between neural networks, but also in their composition. Resting state fMRI scanning was performed for 4 min twice for each subject and the results of patients with mild depression (N=15) and healthy subjects (N=19) were analyzed. The fMRI signal was reduced into the independent components and the contrasts between the groups and between the first and second records were constructed for each component. During the first scanning, the auditory network of individuals with depression involved greater volume in the left insular region and lower volume in the right hemisphere. In record 2, depression patients were characterized by expansion of the executive network in the left hemisphere in the region of the middle and inferior frontal cortex. In healthy people, from record 1 to record 2, representation of the dorsal default mode network (DMN) increased in the left medial prefrontal area, the precuneus network expanded in the left hemisphere, and presentation of the ventral DMN in the right precuneus decreased. In the depression group, the auditory network lost some part of the left temporo-insular cortex; the sensorimotor network expanded in the left hemisphere to the cerebellum or to the central parietal region depending on the evaluation method, and the visuospatial network included or excluded a cluster in the left parietal lobe (in different points). Our findings indicate that connection of the auditory network with the left insular cortex could be a possible depression marker and also demonstrate a possibility of evaluating the composition of cerebral networks in intergroup comparisons and in dynamics without interventions.

Dynamics of Interaction of Neural Networks in the Course of EEG Alpha Biofeedback

Brain EEG-fMRI activity was studied in subjects, who had successfully completed the EEG alpha stimulating training course (20 sessions): for 14 healthy men (20-35 years) three records were obtained in the feedback loop (biofeedback with EEG alpha rhythm with sound reinforcement): in the beginning, middle and at the end of the course. During alpha training, increased functional connectivity was revealed between precuneus network and anterior salience network, left executive control network, default mode network, primary visual network; anterior salience network and executive control network, visual-spatial network. The most prominent changes were found for precuneus network and anterior salience network, which could be due to their key role in the biofeedback phenomenon. Significant changes in functional connectivity were recorded for anterior salience network and precuneus network (synchronicity increased from the first to the third trial) and right and left executive control networks (weakening from the first to the second session.