Extended Remediation of Sleep Deprived-Induced Working Memory Deficits Using fMRI-Guided Transcranial Magnetic Stimulation

STUDY OBJECTIVES: We attempted to prevent the development of working memory (WM) impairments caused by sleep deprivation using fMRI-guided repetitive transcranial magnetic stimulation (rTMS). Novel aspects of our fMRI-guided rTMS paradigm included the use of sophisticated covariance methods to identify functional networks in imaging data, and the use of fMRI-targeted rTMS concurrent with task performance to modulate plasticity effects over a longer term. DESIGN: Between-groups mixed model. SETTING: TMS, MRI, and sleep laboratory study. PARTICIPANTS: 27 subjects (13 receiving Active rTMS, and 14 Sham) completed the sleep deprivation protocol, with another 21 (10 Active, 11 Sham) non-sleep deprived subjects run in a second experiment. INTERVENTIONS: Our previous covariance analysis had identified a network, including occipital cortex, which demonstrated individual differences in resilience to the deleterious effects of sleep deprivation on WM performance. Five Hz rTMS was applied to left lateral occipital cortex while subjects performed a WM task during 4 sessions over the course of 2 days of total sleep deprivation. MEASUREMENTS AND RESULTS: At the end of the sleep deprivation period, Sham sleep deprived subjects exhibited degraded performance in the WM task. In contrast, those receiving Active rTMS did not show the slowing and lapsing typical in sleep deprivation, and instead performed similarly to non- sleep deprived subjects. Importantly, the Active sleep deprivation group showed rTMS-induced facilitation of WM performance a full 18 hours after the last rTMS session. CONCLUSIONS: Over the course of sleep deprivation, these results indicate that rTMS applied concurrently with WM task performance affected neural circuitry involved in WM to prevent its full impact

Different Brain Networks Mediate Task Performance in Normal Aging and AD: Defining Compensation

Objective: To determine whether the pathologic mechanisms of AD alter the brain networks subserving performance of a verbal recognition task. Background: Functional imaging studies comparing task-related activation in AD patients and controls generally have not used network analysis and have not controlled for task difficulty. Methods: H215O PET was used to measure regional cerebral blood flow in 14 patients and 11 healthy elders during the performance of a serial verbal recognition task under two conditions: low demand, with study list size (SLS) equal to one; and titrated demand, with SLS adjusted so that each subject recognized words at 75% accuracy. The Scaled Subprofile Model was used to identify networks of regionally covarying activity across these task conditions. Results: In the elders, higher SLS was associated with the recruitment of a network of brain areas involving left anterior cingulate and anterior insula (R2 = 0.94; p < 0.0001). Three patients also expressed this network. In the remaining patients, higher SLS was associated with the recruitment of an alternate network consisting of left posterior temporal cortex, calcarine cortex, posterior cingulate, and the vermis (R2 = 0.81, p < 0.001). Expression of this network was unrelated to SLS in the elders and more intact AD patients. Conclusions: The patients’ use of the alternate network may indicate compensation for processing deficits. The transition from the normal to the alternate network may indicate a point where brain disease has irreversibly altered brain function and thus may have important implications for therapeutic intervention

Training in the practice of noninvasive brain stimulation: Recommendations from an IFCN committee

© 2020 As the field of noninvasive brain stimulation (NIBS) expands, there is a growing need for comprehensive guidelines on training practitioners in the safe and effective administration of NIBS techniques in their various research and clinical applications. This article provides recommendations on the structure and content of this training. Three different types of practitioners are considered (Technicians, Clinicians, and Scientists), to attempt to cover the range of education and responsibilities of practitioners in NIBS from the laboratory to the clinic. Basic or core competencies and more advanced knowledge and skills are discussed, and recommendations offered regarding didactic and practical curricular components. We encourage individual licensing and governing bodies to implement these guidelines

Self-Enhancement Processing in the Default Network: A Single-Pulse TMS Study

Abstract Much research has been done on positive selfevaluation and its relationship to mental health. However, little is known about its neural underpinnings. Imaging studies have suggested that the brain\u27s default network is involved with self-related processing and that one portion of the default network, medial prefrontal cortex (MPFC), is particularly involved with self-evaluation. Here, we used transcranial magnetic stimulation (TMS) to causally demonstrate that this network, and particularly MPFC, is involved with self-evaluative processing. In a first experiment, 27 healthy volunteers judged whether adjectives, evenly divided between desirable and undesirable traits, described themselves or their best friends, and a robust self-enhancement bias effect was found. In a second experiment, single-pulse TMS was applied targeting three locations (MPFC and left and right parietal cortex) in a different group of healthy volunteers while they performed the adjective task. In each trial, TMS was applied at one of five different times relative to onset of the adjective ranging from 0 to 480 ms. TMS affected self-enhancement bias in a site- and latency-specific manner: at MPFC, the self-enhancement bias actually reversed at 160 ms, with subjects favoring their best friend over themselves. TMS may thus be of use in investigating areas of mental illness in which self-evaluation is abnormal, potentially as a diagnostic tool. In addition, the present study, combined with our previous reports (Lou et al., Proc Natl Acad Sci USA 101(17):6827-6832, 2004, Exp Brain Res 207:27-38, 2010), causally demonstrates two kinds of self-related processing within the default network, one centered in parietal cortex and concerned with retrieval of self-related associations, and the other MPFC-centered and involved in self-evaluative processing

Enhancing activation in the right temporoparietal junction using theta-burst stimulation: Disambiguating between two hypotheses of top-down control of behavioral mimicry.

Whereas previous research has focused on the role of the rTPJ when consciously inhibiting mimicry, we test the role of the rTPJ on mimicry within a social interaction, during which mimicking occurs nonconsciously. We wanted to determine whether higher rTPJ activation always inhibits the tendency to imitate (regardless of the context) or whether it facilitates mimicry during social interactions (when mimicking is an adaptive response). Participants received either active or sham intermittent theta-burst stimulation (iTBS: a type of stimulation that increases cortical activation) to the rTPJ. Next, we measured how much participants mimicked the hair and face touching of another person. Participants in the active stimulation condition engaged in significantly less mimicry than those in the sham stimulation condition. This finding suggests that even in a context in which mimicking is adaptive, rTPJ inhibits mimicry rather than facilitating it, supporting the hypothesis that rTPJ enhances representations of self over other regardless of the goals within a given context

Direct injection of noise to the visual cortex decreases accuracy but increases decision confidence

The relationship between accuracy and confidence in psychophysical tasks traditionally has been assumed to be mainly positive, i.e., the two typically increase or decrease together. However, recent studies have reported examples of exceptions, where confidence and accuracy dissociate from each other. Explanations for such dissociations often involve dual-channel models, in which a cortical channel contributes to both accuracy and confidence, whereas a subcortical channel only contributes to accuracy. Here, we show that a single-channel model derived from signal detection theory (SDT) can also account for such dissociations. We applied transcranial magnetic stimulation (TMS) to the occipital cortex to disrupt the internal representation of a visual stimulus. The results showed that consistent with previous research, occipital TMS decreased accuracy. However, counterintuitively, it also led to an increase in confidence ratings. The data were predicted well by a single-channel SDT model, which posits that occipital TMS increased the variance of the internal stimulus distributions. A formal model comparison analysis that used information theoretic methods confirmed that this model was preferred over single-channel models, in which occipital TMS changed the signal strength or dual-channel models, which assume two different processing routes. Thus our results show that dissociations between accuracy and confidence can, at least in some cases, be accounted for by a single-channel model. © 2012 the American Physiological Society.Link_to_subscribed_fulltex

Safety and feasibility of magnetic seizure therapy (MST) in major depression: Randomized withinsubject comparison with electroconvulsive therapy. Neuropsychopharmacology

Magnetic seizure therapy (MST) is a novel means of performing convulsive therapy using rapidly alternating strong magnetic fields. MST offers greater control of intracerebral current intensity than is possible with electroconvulsive therapy (ECT). These features may result in a superior cognitive side effect profile for MST, while possibly retaining the efficacy of ECT. The objective of this study was to determine whether MST and ECT differ in seizure characteristics, and acute objective and subjective cognitive side effects. A total of 10 inpatients in a major depressive episode referred for ECT were enrolled in this randomized, within-subject, double-masked trial. Seizure threshold was determined with MST and ECT in the first two sessions of a course of convulsive therapy, with order randomized. The remaining two sessions consisted of suprathreshold stimulation with MST and ECT. A neuropsychological battery and side effect rating scale were administered by a masked rater before and after each session. Tonic-clonic seizures were elicited with MST in all patients. Compared to ECT, MST seizures had shorter duration, lower ictal EEG amplitude, and less postictal suppression. Patients had fewer subjective side effects and recovered orientation more quickly with MST than ECT. MST was also superior to ECT on measures of attention, retrograde amnesia, and category fluency. Magnetic seizure induction in patients with depression is feasible, and appears to have a superior acut