Neurophysiological Subtypes of Depressive Disorders

Background: the clinical polymorphism of depressive disorders, together with the available data on the different responses of patients to treatment, motivate modern neuroscience to search for models that can explain such heterogeneity.Objective: to identify neurophysiological subtypes of depressive disorders.Patients and methods: 189 patients with moderate depression in the structure of a depressive episode (n = 42), recurrent depressive (n = 102) and bipolar affective disorders (n = 45); 56 healthy subjects. Clinical-psychopathological, psychometric, neurophysiological and statistical research methods were used in the work.The results: with the help of coherent EEG analysis, it is possible to identify at least 6 subtypes of the disorder, which characterize various branches of the pathogenesis of affective pathology, which go beyond the currently accepted nomenclature. The selected subtypes were determined by the profi les of dysfunctional interaction of various cortical zones in the alpha, beta and gamma ranges of the EEG. Subtype 1 was characterized by a decrease relative to the norm of imaginary alpha-coherence between the right parietal and left central, right parietal and left anterior temporal, as well as the right parietal and right anterior temporal EEG leads (P4-C3, P4-F7, P4-F8) and explained part of depressions, in the pathogenesis of which the leading role was played by violations of the promotion of positive and suppression of negative affect. Subtype 2 — an increase in beta-2-imaginary-coherence between the frontal leads of the left and right hemispheres, between the left frontal and right central cortex (F3-F4; F3-C4) and its decrease between the central cortical zones (C4-C3), in clinical terms this subtype was characterized by a persistent hedonic response and was associated with the clinical picture of atypical depression. Subtype 3 — an increase in imaginary alpha-coherence between the frontal (F4-F3) and its decrease between the central leads of the left and right hemisphere (C4-C3), correlated with the severity of depressive rumination. Subtype 4 — a decrease in imaginary alpha-coherence between the anterior temporal and frontal, as well as the anterior temporal and central cortex of the right hemisphere (F8-F4 and F8-C4), explained part of the depressions that developed against the background of avoidance personality disorder. Subtype 5 — a decrease in imaginary gamma coherence between the frontal and parietal, as well as the central and occipital cortical zones of the left hemisphere (F3-P3 and C3-O1), was associated with an outwardly oriented utilitarian style of thinking (alexithymia). Subtype 6 — a decrease in imaginary beta-1 coherence between the left central and right anterior temporal cortex (C3-F8), explained part of the depression with phobic and hypochondriacal disorders in the structure of recurrent depressive disorder. Such a clinical and biological typology seems new and promising in terms of searching for specifi c neurophysiological disorders in different types of depression and, accordingly, reaching differentiated therapeutic recommendations.

Contribution of the basal forebrain to corticocortical network interactions

Basal forebrain (BF) cholinergic neurons provide the cerebral cortex with acetylcholine. Despite the long-established involvement of these cells in sensory processing, attention, and memory, the mechanisms by which cholinergic signaling regulates cognitive processes remain elusive. In this study, we recorded spiking and local field potential data simultaneously from several locations in the BF, and sites in the orbitofrontal and visual cortex in transgenic ChAT-Cre rats performing a visual discrimination task. We observed distinct differences in the fine spatial distributions of gamma coherence values between specific basalo-cortical and cortico-cortical sites that shifted across task phases. Additionally, cholinergic firing induced spatial changes in cortical gamma power, and optogenetic activation of BF increased coherence between specific cortico-cortical sites, suggesting that the cholinergic system contributes to selective modulation of cortico-cortical circuits. Furthermore, the results suggest that cells in specific BF locations are dynamically recruited across behavioral epochs to coordinate interregional cortical processes underlying cognition.

Cannabis Vapour Exposure Alters Neural Circuit Oscillatory Activity In A Neurodevelopmental Model Of Schizophrenia: Exploring The Differential Impact Of Cannabis Constituents

Cannabis use is highly prevalent in patients with schizophrenia and worsens the course of the disorder. To understand the causal impacts of cannabis on schizophrenia-related oscillatory disruptions, we herein investigated the impact of exposure to cannabis vapour (containing delta-9-tetrahydrocannabinol [THC] or balanced THC and cannabidiol [CBD]) on oscillatory activity in the neonatal ventral hippocampal lesion (NVHL) rat model of schizophrenia. Male Sprague Dawley rats underwent NVHL or sham surgeries on postnatal day 7. In adulthood, electrodes were implanted targeting the cingulate cortex (Cg), the prefrontal cortex (PFC), the dorsal hippocampus (HIP), and the nucleus accumbens (NAc). Local field potential recordings were obtained following exposure to two strains of vapourized cannabis flower (with ~10% THC or ~10% balanced THC:CBD) in a cross-over design with a two-week wash-out period between exposures. Compared to controls, NVHL rats had reduced baseline gamma power in the Cg, dHIP, and NAc, and reduced high-gamma coherence between the dHIP-Cg. THC-only vapour broadly suppressed oscillatory power and coherence, even beyond the baseline suppressions observed in NHVL rats. Balanced THC:CBD vapour appeared to ameliorate the THC-induced impacts on power and coherence in both sham and NVHL rats. For NVHL rats, THC-only vapour also normalized the baseline dHIP-Cg high-gamma coherence deficits. NHVL rats also demonstrated a 20ms delay in dHIP theta to high-gamma phase coupling, which was ameliorated by both exposures in the PFC and NAc. In conclusion, THC-only cannabis vapour suppressed oscillatory activity in NVHL and sham rats, while balanced THC:CBD vapour may ameliorate some of these effects.

EEG Patterns and Performance When Facing the Cardinal Directions

1) Background and Objectives: Position in space and passage of time are encoded in the firing of thalamic, hippocampal and entorhinal cortices in rodents. Head direction cells have been reported in freely moving monkeys, and differential brain patterns have been observed in humans while playing a navigation video game and in response to changes in electromagnetic fields. The sensitivity of organisms to environmental and electromagnetic cues could explain recommendations from a traditional system of architecture, Vastu architecture, which recommends aligning homes to the cardinal directions. 2) Hypothesis: Vastu architecture predicts that facing east and north are more advantageous than facing west and south. If facing east and north are more advantageous, then subjects should show distinct EEG patterns and improved performance when facing east and north compared to west or south. 3) Materials and Methods: EEG coherence patterns from 32-channel EEG and time-to-complete jigsaw puzzles were compared while subjects faced the four cardinal directions. 4) Results: When facing east and north, subjects’ frontal beta2 and gamma EEG coherence were significantly higher, and they assembled jigsaw puzzles significantly faster than when facing west or south. 5) Discussion: The brain findings fit the performance data. Better focus, which would reasonably be related with faster performance, is associated with higher levels of beta2 and gamma coherence. 6) Conclusion: These data support the possibility that the human brain may be sensitive to cardinal directions. This highlights how intimately we are connected to the environment and suggests a factor that may be important in orienting work spaces and designing class rooms.

Gamma coherence mediates interhemispheric integration during multiple object tracking

Using a multiple object tracking paradigm, we were able to manipulate the need for interhemispheric integration on a per-trial basis, while also having an objective measure of integration efficacy (i.e., tracking performance). We show that tracking performance reflects a cost of integration, which correlates with individual differences in interhemispheric EEG coherence. Gamma coherence appears to uniquely benefit between-hemifield tracking, predicting performance both across participants and across trials.

Cerebellar modulation of prefrontal-hippocampal gamma coherence during spatial working memory decisions

ABSTRACTThe medial prefrontal cortex (mPFC) and dorsal hippocampal CA1 region (dCA1) in rodents show increased coherence of neuronal oscillations during decisions in learned spatial working memory (SWM) tasks and the coherence changes reflect decision outcome. However, how coherence is controlled is unknown. We found in mice that decision related gamma coherence modulation between the mPFC and dCA1 and normal SWM performance required an intact cerebellum. Optogenetic activation of the cerebellar lobulus simplex impaired decision-related mPFC-dCA1 coherence modulation and SWM performance. Our findings reveal a role for the cerebellum in the task-specific modulation of coherence between cerebral cortical areas as possible mechanism of cerebellar cognitive function.

Dynamics of coherent activity between cortical areas defines a two-stage process of selective attention

ABSTRACTAnalysing a visual scene requires the brain to briefly keep in memory potentially relevant parts and then direct attention to their locations for detailed processing. To reveal the neuronal basis of the underlying working memory and top-down attention processes, we trained macaques to match two patterns presented with a delay between them. As the above processes are likely to require communication between brain regions, and the parietal cortex is involved in spatial attention, we simultaneously recorded neuronal activities from the interconnected parietal and middle temporal areas. We found that mnemonic information about the first pattern was retained in coherent oscillating activity between the areas in high-frequency bands, followed by coherent activity in low-frequency bands that mediate top-down attention on the relevant location.ONE SENTENCE SUMMARYGamma coherence allows retaining object features in a saliency map while lower frequency coherence facilitates attention.

Gamma coherence mediates interhemispheric integration during multiple object tracking

ABSTRACTOur ability to track the paths of multiple visual objects moving between the hemifields requires effective integration of information between the two cerebral hemispheres. Coherent neural oscillations in the gamma band (35–70 Hz) are hypothesised to drive this information transfer. Here we manipulated the need for interhemispheric integration using a novel multiple object tracking (MOT) task in which stimuli either moved between the two visual hemifields—requiring interhemispheric integration—or moved within separate visual hemifields. We used electroencephalography (EEG) to measure interhemispheric coherence during the task. Human observers (21 female; 20 male) were poorer at tracking objects between-versus within-hemifields, reflecting a cost of interhemispheric integration. Critically, gamma coherence was greater in trials requiring interhemispheric integration, particularly between sensors over parieto-occipital areas. In approximately half of the participants, the observed cost of integration was associated with a failure of the cerebral hemispheres to become coherent in the gamma band. Moreover, individual differences in this integration cost correlated with endogenous gamma coherence at these same sensors, though with generally opposing relationships for the real and imaginary part of coherence. The real part (capturing synchronisation with a near-zero phase-lag) benefited between-hemifield tracking; imaginary coherence was detrimental. Finally, instantaneous phase-coherence over the tracking period uniquely predicted between-hemifield tracking performance, suggesting that effective integration benefits from sustained interhemispheric synchronisation. Our results show that gamma coherence mediates interhemispheric integration during MOT, and add to a growing body of work demonstrating that coherence drives communication across cortically distributed neural networks.