Functional Connectivity Of Dorsal Striatum Research Articles

Sex differences in attention deficit hyperactivity symptom severity and functional connectivity of the dorsal striatum in young adults

Attention deficit hyperactivity disorder (ADHD) occurs more frequently and manifests with greater symptom severity in men than in women. Although studies have implicated basal ganglia dysfunction, the functional connectivity (FC) of the dorsal striatum (DS), particularly in terms of sex differences, has not been fully investigated in ADHD. Here, using resting state fMRI data of a large sample of adults (n = 744; 395 women; 22–36 years) curated from the Human Connectome Project, we performed seed-based correlations for caudate and lentiform nucleus (LN) FC. ADHD symptom severity was quantified with the Achenbach Adult Self-Report ADHD total score as well as inattention and hyperactivity subscores. Imaging data were processed with published routines and evaluated at a corrected threshold. Men showed significantly higher ADHD total score than women. In men, inattention was negatively associated with LN FC with the right superior frontal gyrus. In women, inattention was negatively associated with caudate FC with the right inferior parietal gyrus and positively with LN FC with the left inferior frontal gyrus, and hyperactivity was positively associated with LN FC with a cluster in the dorsal anterior cingulate cortex and supplementary motor area. Sex differences in most of these connectivity patterns were confirmed by slope tests. Further, k-means clustering of FC's identified 3 groups each in men and in women. In men, group 1 showed higher inattention and hyperactivity than both group 2 and 3, and group 2 showed higher inattention than group 3. In women, group 1 showed higher inattention and hyperactivity than group 3 and higher inattention than group 2, and group 2 showed higher hyperactivity than group 3. These findings together suggest sex differences in DS FC as neural markers of ADHD and potentially of ADHD subtypes, with men and women each showing altered FC predominantly in the executive control and ventral attention/saliency networks.

Remodeling of Sensorimotor Brain Connectivity in Gpr88-Deficient Mice.

Recent studies have demonstrated that orchestrated gene activity and expression support synchronous activity of brain networks. However, there is a paucity of information on the consequences of single gene function on overall brain functional organization and connectivity and how this translates at the behavioral level. In this study, we combined mouse mutagenesis with functional and structural magnetic resonance imaging (MRI) to determine whether targeted inactivation of a single gene would modify whole-brain connectivity in live animals. The targeted gene encodes GPR88 (G protein-coupled receptor 88), an orphan G protein-coupled receptor enriched in the striatum and previously linked to behavioral traits relevant to neuropsychiatric disorders. Connectivity analysis of Gpr88-deficient mice revealed extensive remodeling of intracortical and cortico-subcortical networks. Most prominent modifications were observed at the level of retrosplenial cortex connectivity, central to the default mode network (DMN) whose alteration is considered a hallmark of many psychiatric conditions. Next, somatosensory and motor cortical networks were most affected. These modifications directly relate to sensorimotor gating deficiency reported in mutant animals and also likely underlie their hyperactivity phenotype. Finally, we identified alterations within hippocampal and dorsal striatum functional connectivity, most relevant to a specific learning deficit that we previously reported in Gpr88-/- animals. In addition, amygdala connectivity with cortex and striatum was weakened, perhaps underlying the risk-taking behavior of these animals. This is the first evidence demonstrating that GPR88 activity shapes the mouse brain functional and structural connectome. The concordance between connectivity alterations and behavior deficits observed in Gpr88-deficient mice suggests a role for GPR88 in brain communication.

The Effects of Pharmacological Opioid Blockade on Neural Measures of Drug Cue-Reactivity in Humans.

Interactions between dopaminergic and opioidergic systems have been implicated in the reinforcing properties of drugs of abuse. The present study investigated the effects of opioid blockade, via naltrexone, on functional magnetic resonance imaging (fMRI) measures during methamphetamine cue-reactivity to elucidate the role of endogenous opioids in the neural systems underlying drug craving. To investigate this question, non-treatment seeking individuals with methamphetamine use disorder (N=23; 74% male, mean age=34.70 (SD=8.95)) were recruited for a randomized, placebo controlled, within-subject design and underwent a visual methamphetamine cue-reactivity task during two blood-oxygen-level dependent (BOLD) fMRI sessions following 3 days of naltrexone (50 mg) and matched time for placebo. fMRI analyses tested naltrexone-induced differences in BOLD activation and functional connectivity during cue processing. The results showed that naltrexone administration reduced cue-reactivity in sensorimotor regions and related to altered functional connectivity of dorsal striatum, ventral tegmental area, and precuneus with frontal, visual, sensory, and motor-related regions. Naltrexone also weakened the associations between subjective craving and precuneus functional connectivity with sensorimotor regions and strengthened the associations between subjective craving and dorsal striatum and precuneus connectivity with frontal regions. In conclusion, this study provides the first evidence that opioidergic blockade alters neural responses to drug cues in humans with methamphetamine addiction and suggests that naltrexone may be reducing drug cue salience by decreasing the involvement of sensorimotor regions and by engaging greater frontal regulation over salience attribution.

Initial Evidence that OPRM1 Genotype Moderates Ventral and Dorsal Striatum Functional Connectivity During Alcohol Cues

Endogenous opioids and striatal dopamine have been implicated in cue-induced alcohol craving and have been hypothesized to play a role in goal-directed, as opposed to habitual, alcohol use. This initial study examines dorsal and ventral striatal functional connectivity during alcohol-cue processing as a function of the A118G single-nucleotide polymorphism of the mu-opioid receptor (OPRM1) gene. Seventeen individuals with alcohol dependence (6 females; 90% Caucasian; mean age = 29.4) underwent blood oxygen level-dependent functional magnetic resonance imaging, while performing an alcohol taste-cues task. Psychophysiological interaction analyses investigated associations of the OPRM1 genotype with ventral and dorsal striatum functional connectivity, using the ventral striatum and the caudate as the seed region, respectively. Compared to A-allele homozygotes, G-allele carriers of the OPRM1 gene showed (i) greater activation of the insula and orbitofrontal cortex and (ii) stronger negative fronto-striatal functional connectivity for both ventral and dorsal striatal seed regions during processing of alcohol versus water cues. These preliminary findings suggest that, relative to A-allele homozygotes, G-allele carriers show unstable frontal regulation over reward and/or habit-driven inputs from the striatum resulting from greater reward sensitivity combined with limited self-control resources.