Predictors of remission after repetitive transcranial magnetic stimulation for the treatment of late-life depression.

Repetitive transcranial magnetic stimulation (rTMS) is an effective treatment in patients with depression, yet treatment response remains variable. While previous work has identified predictors of remission in younger adults, relatively little data exists in late-life depression (LLD). To address this gap, data from 164 participants with LLD from a randomized non-inferiority treatment trial comparing standard bilateral rTMS to bilateral theta burst stimulation (TBS) (ClinicalTrials.gov identifier: NCT02998580) were analyzed using binary logistic regression and conditional inference tree (CIT) modeling. Lower baseline depression symptom severity, fewer prior antidepressant treatment failures, and higher global cognition predicted remission following rTMS treatment. The CIT predicted a higher likelihood of achieving remission for patients with a total score of 19 or lower on the Montgomery-Åsberg Depression Rating Scale, 1 or fewer prior antidepressant treatment failures, and a total score of 23 or higher on the Montreal Cognitive Assessment. Our results indicate that older adults with lower severity of depression, fewer antidepressant treatment failures, and higher global cognition benefit more from current forms of rTMS. The results suggest that there is potentially higher value in using rTMS earlier in the treatment pathway for depression in older adults.

Neural alpha oscillations index context-driven perception of ambiguous vowel sequences.

Perception of bistable stimuli is influenced by prior context. In some cases, the interpretation matches with how the preceding stimulus was perceived; in others, it tends to be the opposite of the previous stimulus percept. We measured high-density electroencephalography (EEG) while participants were presented with a sequence of vowels that varied in formant transition, promoting the perception of one or two auditory streams followed by an ambiguous bistable sequence. For the bistable sequence, participants were more likely to report hearing the opposite percept of the one heard immediately before. This auditory contrast effect coincided with changes in alpha power localized in the left angular gyrus and left sensorimotor and right sensorimotor/supramarginal areas. The latter correlated with participants' perception. These results suggest that the contrast effect for a bistable sequence of vowels may be related to neural adaptation in posterior auditory areas, which influences participants' perceptual construal level of ambiguous stimuli.

Evidence of Neuroplastic Changes after Transcranial Magnetic, Electric, and Deep Brain Stimulation.

Electric and magnetic stimulation of the human brain can be used to excite or inhibit neurons. Numerous methods have been designed over the years for this purpose with various advantages and disadvantages that are the topic of this review. Deep brain stimulation (DBS) is the most direct and focal application of electric impulses to brain tissue. Electrodes are placed in the brain in order to modulate neural activity and to correct parameters of pathological oscillation in brain circuits such as their amplitude or frequency. Transcranial magnetic stimulation (TMS) is a non-invasive alternative with the stimulator generating a magnetic field in a coil over the scalp that induces an electric field in the brain which, in turn, interacts with ongoing brain activity. Depending upon stimulation parameters, excitation and inhibition can be achieved. Transcranial electric stimulation (tES) applies electric fields to the scalp that spread along the skull in order to reach the brain, thus, limiting current strength to avoid skin sensations and cranial muscle pain. Therefore, tES can only modulate brain activity and is considered subthreshold, i.e., it does not directly elicit neuronal action potentials. In this review, we collect hints for neuroplastic changes such as modulation of behavior, the electric activity of the brain, or the evolution of clinical signs and symptoms in response to stimulation. Possible mechanisms are discussed, and future paradigms are suggested.