Associations between vicarious racism and psychoactive substance use depend on strength of ethnic identity.

Racism is a pervasive threat to health with differential impact based on race and ethnicity. Considering the continued perpetration and visibility of racism online and in the news, vicarious racism, or "secondhand" racism when hearing about or witnessing racism being committed against members of one's ethnic or racial group, is a particularly urgent threat in the context of such disparities and their subsequent health consequences. The current study examines if frequency of exposure to vicarious racism and the emotional impact of those experiences are linked to psychoactive substance use, and explores the role of ethnic identity in moderating these relationships. In a cross-sectional survey, 504 adult participants aged 18-78 (M age = 30.15, SD = 11.52, 52.6% female) identifying as Black/African American or Latine reported on their experiences with vicarious racism and alcohol, marijuana, and tobacco use over the past 30 days. Logistic regression was utilized to test hypotheses. Primary findings indicate that greater emotional impact of vicarious racism was associated with a 50% increase in odds of alcohol consumption and that ethnic identity moderated the association between vicarious racism and marijuana use. Greater emotional impact of vicarious racism was related to more marijuana use for those lower on ethnic identity, whereas there was no association for those higher on ethnic identity. Vicarious racism was not related to tobacco use. Results suggest that ethnic identity might be protective in the association of vicarious racism on substance use. Further research on this topic is needed as vicarious racism becomes an increasingly common experience among marginalized populations.

Outlier detection in multimodal MRI identifies rare individual phenotypes among more than 15,000 brains.

Outliers in neuroimaging represent spurious data or the data of unusual phenotypes that deserve special attention such as clinical follow-up. Outliers have usually been detected in a supervised or semi-supervised manner for labeled neuroimaging cohorts. There has been much less work using unsupervised outlier detection on large unlabeled cohorts like the UK Biobank brain imaging dataset. Given its large sample size, rare imaging phenotypes within this unique cohort are of interest, as they are often clinically relevant and could be informative for discovering new processes. Here, we developed a two-level outlier detection and screening methodology to characterize individual outliers from the multimodal MRI dataset of more than 15,000 UK Biobank subjects. In primary screening, using brain ventricles, white matter, cortical thickness, and functional connectivity-based imaging phenotypes, every subject was parameterized with an outlier score per imaging phenotype. Outlier scores of these imaging phenotypes had good-to-excellent test-retest reliability, with the exception of resting-state functional connectivity (RSFC). Due to the low reliability of RSFC outlier scores, RSFC outliers were excluded from further individual-level outlier screening. In secondary screening, the extreme outliers (1,026 subjects) were examined individually, and those arising from data collection/processing errors were eliminated. A representative subgroup of 120 subjects from the remaining non-artifactual outliers were radiologically reviewed, and radiological findings were identified in 97.5% of them. This study establishes an unsupervised framework for investigating rare individual imaging phenotypes within a large neuroimaging cohort.

Circuit-Specific Plasticity of Callosal Inputs Underlies Cortical Takeover.

Injury induces synaptic, circuit, and systems reorganization. After unilateral amputation or stroke, this functional loss disrupts the interhemispheric interaction between intact and deprived somatomotor cortices to recruit deprived cortex in response to intact limb stimulation. This recruitment has been implicated in enhanced intact sensory function. In other patients, maladaptive consequences such as phantom limb pain can occur. We used unilateral whisker denervation in male and female mice to detect circuitry alterations underlying interhemispheric cortical reorganization. Enhanced synaptic strength from the intact cortex via the corpus callosum (CC) onto deep neurons in deprived primary somatosensory barrel cortex (S1BC) has previously been detected. It was hypothesized that specificity in this plasticity may depend on to which area these neurons projected. Increased connectivity to somatomotor areas such as contralateral S1BC, primary motor cortex (M1) and secondary somatosensory cortex (S2) may underlie beneficial adaptations, while increased connectivity to pain areas like anterior cingulate cortex (ACC) might underlie maladaptive pain phenotypes. Neurons from the deprived S1BC that project to intact S1BC were hyperexcitable, had stronger responses and reduced inhibitory input to CC stimulation. M1-projecting neurons also showed increases in excitability and CC input strength that was offset with enhanced inhibition. S2 and ACC-projecting neurons showed no changes in excitability or CC input. These results demonstrate that subgroups of output neurons undergo dramatic and specific plasticity after peripheral injury. The changes in S1BC-projecting neurons likely underlie enhanced reciprocal connectivity of S1BC after unilateral deprivation consistent with the model that interhemispheric takeover supports intact whisker processing.SIGNIFICANCE STATEMENT Amputation, peripheral injury, and stroke patients experience widespread alterations in neural activity after sensory loss. A hallmark of this reorganization is the recruitment of deprived cortical space which likely aids processing and thus enhances performance on intact sensory systems. Conversely, this recruitment of deprived cortical space has been hypothesized to underlie phenotypes like phantom limb pain and hinder recovery. A mouse model of unilateral denervation detected remarkable specificity in alterations in the somatomotor circuit. These changes underlie increased reciprocal connectivity between intact and deprived cortical hemispheres. This increased connectivity may help explain the enhanced intact sensory processing detected in humans.