One way to study the neural correlates of visual consciousness is to localize the cortical areas whose stimulation generates subjective visual sensations, called phosphenes. While there is support for the view that the stimulation of several different visual areas in the occipital lobe may produce phosphenes, it is not clear what the contribution of each area is. Here, we studied the roles of the primary visual cortex (V1) and the adjacent area V2 in eliciting phosphenes by using functional magnetic resonance imaging-guided transcranial magnetic stimulation (TMS) combined with spherical modeling of the TMS-induced electric field. Reports of the subjective visual features of phosphenes were systematically collected and analyzed. We found that selective stimulation of V1 and V2 are equally capable of generating phosphenes, as demonstrated by comparable phosphene thresholds and similar characteristics of phosphene shape, color, and texture. However, the phosphenes induced by V1 stimulation were systematically perceived as brighter than the phosphenes induced by the stimulation of V2. Thus, these results suggest that V1 and V2 have a similar capability to produce conscious percepts. Nevertheless, V1 and V2 contribute differently to brightness: neural activation originating in V1 generates a more intense sensation of brightness than similar activation originating in V2.

Repetitive transcranial magnetic stimulation (rTMS) is a popular and effective treatment for drug resistant depression. However, there is considerable variability in clinical outcomes, in previous studies and between patients. Because of high requirements for the use of fMRI based neuronavigation, many practitioners of rTMS still choose to use a standard 5 cm rule for rTMS coil placement which leads to large variations in which brain regions are being stimulated. We decided to test the possibilities of a MNI based MR-less neuronavigation system in rTMS depression treatment, by comparing the physiological effects and clinical outcomes of 3 distinct stimulation targets. Forty-six patients (thirty-three female, thirteen male) from the Republican Vilnius psychiatric hospital, all with drug resistant depressive disorder, participated in the study. All patients received high frequency (10 Hz) stimulation for 10 to 15 daily rTMS sessions. However, before the treatment they were randomly sorted into 3 groups according to stimulation target in MNI map: Group 1 received rTMS at point-40; 48; 35; Group 2 received rTMS at point-46; 45; 38; Group 3 received rTMS at point-38; 44; 26. Electroencephalography (EEG) recordings and clinical tests were obtained the day before the rTMS course and after the last session. There were some notable differences in physiological changes between the groups, with the largest EEG band spectral power increases found in Group 1 patients and the lowest in Group 2 patients. There was a significantly larger decrease of the Hamilton Depression Rating Scale (HAM-D) scores in the Group 3 (66.94%) compared to Group 1 (57.52%) and Group 2 (56.02%). This suggests it is possible to achieve higher clinical efficacy and less physiological impact on the brain when using different targets in a neuronavigated MNI based MR-less rTMS system.

Resistance to pharmacological treatment poses a notable challenge for psychiatry. Such cases are usually treated with brain stimulation techniques, including repetitive transcranial magnetic stimulation (rTMS) and electroconvulsive therapy (ECT). Empirical evidence links treatment resistance to insufficient brain plasticity and chronic inflammation. Therefore, this study encompasses analysis of neurotrophic and inflammatory factors in psychiatric patients undergoing rTMS and ECT in order to refine the selection of patients and predict clinical outcomes. This study enrolled 25 drug‐resistant depressive patients undergoing rTMS and 31 drug‐resistant schizophrenia patients undergoing ECT. Clinical efficacy of brain stimulation therapies was gauged using MADRS and HAM‐D scales in the depression group and PANSS scale in the schizophrenia group. Blood‐derived BDNF, VEGF, and TNFα were analysed during the treatment course. For reference, 19 healthy control subjects were also enrolled. After statistical analysis, no significant differences were detected in BDNF, VEGF, and TNFα concentrations among healthy, depressive, and schizophrenic subject groups before the treatment. However, depressive patient treatment with rTMS has increased BDNF concentration, while schizophrenic patient treatment with ECT has lowered the concentration of TNFα. Our findings suggest that a lower initial TNFα concentration could be a marker for treatment success in depressed patients undergoing rTMS, whereas in schizophrenic patient group treated with ECT, a higher concentration of VEGF correlates to milder symptoms post‐treatment, especially in the negative scale.

AimThe objective of this work was to demonstrate the usefulness of a novel statistical method to study the impact of transcranial magnetic stimulation (TMS) on brain connectivity in patients with depression using different stimulation protocols, i.e., 1 Hz repetitive TMS over the right dorsolateral prefrontal cortex (DLPFC) (protocol G1), 10 Hz repetitive TMS over the left DLPFC (G2), and intermittent theta burst stimulation (iTBS) consisting of three 50 Hz burst bundle repeated at 5 Hz frequency (G3).MethodsElectroencephalography (EEG) connectivity analysis was performed using Directed Transfer Function (DTF) and a set of 21 indices based on graph theory. The statistical analysis of graph-theoretic indices consisted of a combination of the k-NN rule, the leave-one-out method, and a statistical test using a 2 × 2 contingency table.ResultsOur new statistical approach allowed for selection of the best set of graph-based indices derived from DTF, and for differentiation between conditions (i.e., before and after TMS) and between TMS protocols. The effects of TMS was found to differ based on frequency band.ConclusionA set of four brain asymmetry measures were particularly useful to study protocol- and frequency-dependent effects of TMS on brain connectivity.SignificanceThe new approach would allow for better evaluation of the therapeutic effects of TMS and choice of the most appropriate stimulation protocol.

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