Chloe A. Huston

Non-invasive brain stimulation (NIBS) techniques are designed to precisely and selectively target specific brain regions, thus enabling focused modulation of neural activity. Among NIBS technologies, low-intensity transcranial focused ultrasound (tFUS) has emerged as a promising new modality. The application of tFUS can safely and non-invasively stimulate deep brain structures with millimetric precision, offering distinct advantages in terms of accessibility to non-cortical regions over other NIBS methods. However, to date, several tFUS aspects still need to be characterized; furthermore, there are only a handful of studies that have utilized tFUS in psychiatric populations. This narrative review provides an up-to-date overview of key aspects of this NIBS technique, including the main components of a tFUS system, the neuronavigational tools used to precisely target deep brain regions, the simulations utilized to optimize the stimulation parameters and delivery of tFUS, and the experimental protocols employed to evaluate the efficacy of tFUS in psychiatric disorders. The main findings from studies in psychiatric populations are presented and discussed, and future directions are highlighted.

N-acetylaspartate (NAA) and choline (Cho) are two brain metabolites implicated in several key neuronal functions. Abnormalities in these metabolites have been reported in both early course and chronic patients with schizophrenia (SCZ). It is, however, unclear whether NAA and Cho’s alterations occur even before the onset of the disorder. Clinical high risk (CHR) individuals are a population uniquely enriched for psychosis and SCZ. In this exploratory study, we utilized 7-Tesla magnetic resonance spectroscopic imaging (MRSI) to examine differences in total NAA (tNAA; NAA + N-acetylaspartylglutamate [NAAG]) and major choline-containing compounds, including glycerophosphorylcholine and phosphorylcholine [tCho], over the creatine (Cre) levels between 26 CHR and 32 healthy control (HC) subjects in the subcortical and cortical regions. While no tCho/Cre differences were found between groups in any of the regions of interest (ROIs), we found that CHR had significantly reduced tNAA/Cre in the right dorsal lateral prefrontal cortex (DLPFC) compared to HC, and that the right DLPFC tNAA/Cre reduction in CHR was negatively associated with their positive symptoms scores. No tNAA/Cre differences were found between CHR and HC in other ROIs. In conclusion, reduced tNAA/Cre in CHR vs. HC may represent a putative molecular biomarker for risk of psychosis and SCZ that is associated with symptom severity.

The study describes the validation of a computerized adaptation of the novel Tri-Choice Naming and Response Bias Measure (N-Tri) developed to detect untruthful responding while being less susceptible to coaching than existing measures. We hypothesized that the N-Tri would have comparable sensitivity and specificity to traditional tests but would have improved accuracy for detecting coached simulators. Four-hundred volunteers were randomly assigned to one of three groups: uncoached simulators' group (n = 118), coached simulators' group (n = 136), or control group (n = 146). Both simulator groups were asked to feign concussion symptoms, but the coached group received a test-taking strategy and a description of concussion symptoms. The participants were administered the computerized version of the new measure in conjunction with computerized adaptations of two well-validated response bias tests commonly used to detect cognitive malingering, the Reliable Digit Span (RDS) and Portland Digit Recognition Test (PDRT). Our data show the new measure correlated highly with other established measures. However, the classification accuracy did not significantly increase when compared to the traditional tests. Our findings support that the N-Tri performs at a comparable level to existing forced choice measures of response bias. Nevertheless, the N-Tri could potentially improve the detection of response bias as existing tests become more recognizable by the public.