Auditory evoked potentials in adolescents with autism: An investigation of brain development, intellectual impairment, and neural encoding.

Limited research has evaluated neural encoding of sounds from a developmental perspective in individuals with autism (ASD), especially among those with intellectual disability. We compared auditory evoked potentials (AEPs) in autistic adolescents with a wide range of intellectual abilities (n = 40, NVIQ 30-160) to both age-matched cognitively able neurotypical adolescent controls (NT-A, n = 37) and younger neurotypical children (NT-C, n = 27) to assess potential developmental delays. In addition to a classic measure of peak amplitude, we calculated a continuous measure of intra-class correlation (ICC) between each adolescent participant's AEP and the age-normative, average AEP waveforms calculated from NT-C and NT-A to study differences in signal morphology. We found that peak amplitudes of neural responses were significantly smaller in autistic adolescents compared to NT-A. We also found that the AEP morphology of autistic adolescents looked more like NT-A peers than NT-C but was still significantly different from NT-A AEP waveforms. Results suggest that AEPs of autistic adolescents present differently from NTs, regardless of age, and differences cannot be accounted for by developmental delay. Nonverbal intelligence significantly predicted how closely each adolescent's AEP resembled the age-normed waveform. These results support an evolving theory that the degree of disruption in early neural responses to low-level inputs is reflected in the severity of intellectual impairments in autism.

Brain volumetric correlates of electroconvulsive therapy versus transcranial magnetic stimulation for treatment-resistant depression.

BACKGROUND: Electroconvulsive therapy (ECT) and repetitive transcranial magnetic stimulation (rTMS) are effective neuromodulation therapies for treatment-resistant depression (TRD). While ECT is generally considered the most effective antidepressant, rTMS is less invasive, better tolerated and leads to more durable therapeutic benefits. Both interventions are established device antidepressants, but it remains unknown if they share a common mechanism of action. Here we aimed to compare the brain volumetric changes in patients with TRD after right unilateral (RUL) ECT versus left dorsolateral prefrontal cortex (lDLPFC) rTMS. METHODS: We assessed 32 patients with TRD before the first treatment session and after treatment completion using structural magnetic resonance imaging. Fifteen patients were treated with RUL ECT and seventeen patients received lDLPFC rTMS. RESULTS: Patients receiving RUL ECT, in comparison with patients treated with lDLPFC rTMS, showed a greater volumetric increase in the right striatum, pallidum, medial temporal lobe, anterior insular cortex, anterior midbrain, and subgenual anterior cingulate cortex. However, ECT- or rTMS-induced brain volumetric changes were not associated with the clinical improvement. LIMITATIONS: We evaluated a modest sample size with concurrent pharmacological treatment and without neuromodulation therapies randomization. CONCLUSIONS: Our findings suggest that despite comparable clinical outcomes, only RUL ECT is associated with structural change, while rTMS is not. We hypothesize that structural neuroplasticity and/or neuroinflammation may explain the larger structural changes observed after ECT, whereas neurophysiological plasticity may underlie the rTMS effects. More broadly, our results support the notion that there are multiple therapeutic strategies to move patients from depression to euthymia.

Extension of transcranial magnetic stimulation treatment for depression in non-responders: Results of a naturalistic study.

BACKGROUND: Repetitive Transcranial Magnetic Stimulation (rTMS) shows efficacy in the treatment of major depressive disorder using a standard course of 20-36 treatment sessions. However, research efforts are being made to improve overall response and remission rates. Evidence from open-label extension studies of randomized control trials suggests that extending the rTMS treatment course beyond 36 treatments may improve outcomes, however, little has been published on the benefit of extended TMS treatment courses in clinical practice. OBJECTIVE: In this retrospective naturalistic observational study, we studied response rates on continuation of rTMS following failure of the first round of 36 treatments. METHODS: From 142 patients who received conventional rTMS and 29 who underwent theta-burst stimulation (TBS) at Massachusetts General Hospital TMS clinical service, 28 non-responders (23 to rTMS and 5 to TBS) opted to continue their treatment beyond session 36. The treatment protocol allowed personalization in target, TMS protocol, as well as number of pulses and sessions as clinically indicated. Sustained response and remission using Hamilton Rating Scale for Depression, 17-items (HAMD-17) was the primary outcome. RESULTS: The average number of overall treatment sessions was 70.54 ± 16.73 for the sample. Overall, there was a 53.57% response rate and a 32.14% remission rate. Response and remission rates rose as the number of sessions increased and there did not appear to be a plateau in response over time. CONCLUSION: Our results support the idea that subpopulation of TMS patients are late responders. Continuation of TMS up to 72 treatments among those patients who do not meet response criteria by session 36 may improve overall response rates. While the number of subjects and study design limit generalization, given the fact that these patients were medication refractory and had failed initial course of TMS, the result of this study is encouraging.