Association between tDCS computational modeling and clinical outcomes in depression: data from the ELECT-TDCS trial

European Archives of Psychiatry and Clinical Neuroscience - Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation intervention investigated for the treatment of...     

Clinical Factors Underlying the Inter-individual Variability of the Resting Motor Threshold in Navigated Transcranial Magnetic Stimulation Motor Mapping

Correctly determining individual’s resting motor threshold (rMT) is crucial for accurate and reliable mapping by navigated transcranial magnetic stimulation (nTMS), which is especially true for preoperative motor mapping in brain tumor patients. However, systematic data analysis on clinical factors underlying inter-individual rMT variability in neurosurgical motor mapping is sparse. The present study examined 14 preselected clinical factors that may underlie inter-individual rMT variability by performing multiple regression analysis (backward, followed by forward model comparisons) on the nTMS motor mapping data of 100 brain tumor patients. Data were collected from preoperative motor mapping of abductor pollicis brevis (APB), abductor digiti minimi (ADM), and flexor carpi radialis (FCR) muscle representations among these patients. While edema and age at exam in the ADM model only jointly reduced the unexplained variance significantly, the other factors kept in the ADM model (gender, antiepileptic drug intake, and motor deficit) and each of the factors kept in the APB and FCR models independently significantly reduced the unexplained variance. Hence, several clinical parameters contribute to inter-individual rMT variability and should be taken into account during initial and follow-up motor mappings. Thus, the present study adds basic evidence on inter-individual rMT variability, whereby some of the parameters are specific to brain tumor patients.     

Reorganization of Motor Representations in Patients with Brain Lesions: A Navigated Transcranial Magnetic Stimulation Study

This is an explorative study applying presurgical navigated transcranial magnetic stimulation (nTMS) to investigate the spatial distributions of motor sites to reveal tumor-induced brain plasticity in patients with brain tumors. We analyzed nTMS-based motor maps derived from presurgical mapping of 100 patients with motor eloquently located brain tumors (tumors in the frontal lobe, the precentral gyrus [PrG], the postcentral gyrus [PoG], the remaining parietal lobe, or the temporal lobe). Based on these motor maps, we systematically investigated changes in motor evoked potential (MEP) counts among 4 gyri (PrG, PoG, medial frontal gyrus, and superior frontal gyrus) between subgroups of patients according to the tumor location in order to depict the tumor’s influence on reorganization. When comparing patients with different tumor locations, high MEP counts were elicited less frequently by stimulating the PrG in patients with tumors directly affecting the PrG (p?<?0.05). Still, in more than 50% of these patients, the MEP counts elicited by stimulating the PrG were higher than average, indicating robust motor representations within the primary motor cortex. In contrast, patients with PoG and parietal tumors primarily showed high MEP counts when stimulating the PoG (p?<?0.10). The functional reorganization is not likely to induce a shift of motor function from the PrG to adjacent regions but rather leads to a reorganization within anatomical constraints, such as of the PoG. Thus, presurgical nTMS-based motor mapping sensitively depicted the tumor-induced plasticity of the motor cortex.     

Effects of bifrontal transcranial direct current stimulation on brain glutamate levels and resting state connectivity: multimodal MRI data for the cathodal stimulation site

European Archives of Psychiatry and Clinical Neuroscience - Transcranial direct current stimulation (tDCS) over prefrontal cortex (PFC) regions is currently proposed as therapeutic intervention for...     

MEG imaging of recurrent gliomas reveals functional plasticity of hemispheric language specialization

In patients with gliomas, changes in hemispheric specialization for language determined by magnetoencephalography (MEG) were analyzed to elucidate the impact of treatment and tumor recurrence on language networks. Demonstration of reorganization of language networks in these patients has significant implications on the prevention of postoperative functional loss and recovery. Whole‐brain activity during an auditory verb generation task was estimated from MEG recordings in a group of 73 patients with recurrent gliomas. Hemisphere of language dominance was estimated using the language laterality index (LI), a measure derived from the task. The initial scan was performed prior to resection; patients subsequently underwent surgery and adjuvant treatment. A second scan was performed upon recurrence prior to repeat resection. The relationship between the shift in LI between scans and demographics, anatomic location, pathology, and adjuvant treatment was analyzed. Laterality shifts were observed between scans; the median percent change was 29.1% across all patients. Laterality shift magnitude and relative direction were associated with the initial position of language dominance; patients with increased lateralization experienced greater shifts than those presenting more bilateral representation. A change in LI from left or right to bilateral (or vice versa) occurred in 23.3% of patients; complete switch occurred in 5.5% of patients. Patients with tumors within the language‐dominant hemisphere experienced significantly greater shifts than those with contralateral tumors. The majority of patients with glioma experience shifts in language network organization over time which correlate with the relative position of language lateralization and tumor location.     

Prefrontal resting-state connectivity and antidepressant response: no associations in the ELECT-TDCS trial

European Archives of Psychiatry and Clinical Neuroscience - Functional and structural MRI of prefrontal cortex (PFC) may provide putative biomarkers for predicting the treatment response to...