Frontostriatal Functional Connectivity Research Articles

Frontostriatal functional connectivity in major depressive disorder

BackgroundAbnormalities of the striatum and frontal cortex have been reported consistently in studies of neural structure and function in major depressive disorder (MDD). Despite speculation that compromised connectivity between these regions may underlie symptoms of MDD, little work has investigated the integrity of frontostriatal circuits in this disorder.MethodsFunctional magnetic resonance images were acquired from 21 currently depressed and 19 never-disordered women during wakeful rest. Using four predefined striatal regions-of-interest, seed-to-whole brain correlations were computed and compared between groups.ResultsCompared to controls, depressed participants exhibited attenuated functional connectivity between the ventral striatum and both ventromedial prefrontal cortex and subgenual anterior cingulate cortex. Depressed participants also exhibited stronger connectivity between the dorsal caudate and dorsal prefrontal cortex, which was positively correlated with severity of the disorder.ConclusionsDepressed individuals are characterized by aberrant connectivity in frontostriatal circuits that are posited to support affective and cognitive processing. Further research is required to examine more explicitly the link between patterns of disrupted connectivity and specific symptoms of depression, and the extent to which these patterns precede the onset of depression and normalize with recovery from depressive illness.

Dopamine and frontostriatal networks in cognitive aging

Recent studies have linked dopamine to differences in behavior and brain activity in normal individuals. We explored these relationships in older and younger adults by investigating how functional connectivity between the striatum and prefrontal cortex is related to caudate dopamine and verbal working memory task performance. We studied 12 young and 18 older participants with functional magnetic resonance imaging (fMRI) during this task, and used positron emission tomography with the tracer 6-[18F]-fluoro-L-m-tyrosine (FMT) to assess dopamine synthesis capacity. Younger adults had a greater extent of frontal caudate functional connectivity during the load-dependent delay period of the working memory task than the older participants. Across all subjects, the extent of this functional connectivity was negatively correlated with dopamine synthesis capacity, such that participants with the greatest connectivity had the lowest caudate 6-[18F]-fluoro-L-m-tyrosine (FMT) signal. Additionally, the extent of functional connectivity was positively correlated with working memory performance. Overall these data suggest interdependencies exist between frontostriatal functional connectivity, dopamine, and working memory performance and that this system is functioning suboptimally in normal aging.

Enhanced cue reactivity and fronto-striatal functional connectivity in cocaine use disorders

Chronic cocaine use is associated with enhanced cue reactivity to drug stimuli. However, it may also alter functional connectivity (fcMRI) in regions involved in processing drug stimuli. Our aims were to evaluate the neural regions involved in subjective craving and how fcMRI may be altered in chronic cocaine users. Fourteen patients with a confirmed diagnosis of cocaine abuse or dependence (CCA) and 16 gender, age, and education-matched healthy controls (HC) completed a cue reactivity task and a resting state scan while undergoing functional magnetic resonance imaging. CCA showed increased activation compared to HC in left dorsolateral prefrontal and bilateral occipital cortex in response to cocaine cues but not to appetitive control stimuli. Moreover, CCA also showed increased activation within the orbital frontal cortex (OFC) for cocaine cues relative to the appetitive stimuli during a hierarchical regression analysis. A negative association between subjective craving and activity in medial posterior cingulate gyrus (PCC) was also observed for CCA. CCA exhibited increased resting state correlation (positive) between cue-processing seed regions (OFC and ventral striatum), and negative connectivity between cue-processing regions and PCC/precuneus. These alterations in fcMRI may partially explain the neural basis of increased drug cue salience in CCA.

The Dopamine Agonist Bromocriptine Differentially Affects Fronto-Striatal Functional Connectivity During Working Memory

We investigated the effect of bromocriptine, a dopamine agonist, on individual differences in behavior as well as frontal–striatal connectivity during a working memory task. After dopaminergic augmentation, frontal–striatal connectivity in low working memory capacity individuals increases, corresponding with behavioral improvement whereas decreases in connectivity in high working memory capacity individuals are associated with poorer behavioral performance. These findings corroborate an inverted U-shape response of dopamine function in behavioral performance and provide insight on the corresponding neural mechanisms.

Dopamine Depletion Impairs Frontostriatal Functional Connectivity during a Set-Shifting Task

We investigated the effect of transient dopamine depletion on functional connectivity during performance of the Wisconsin Card Sorting Task. Functional magnetic resonance imaging data were analyzed as a psychophysiological interaction, a statistical method used to identify functional connectivity during experimental manipulations. Nineteen healthy subjects were scanned, double blind, on 2 separate days: once after drinking an amino acid mixture deficient in the dopamine precursors tyrosine and phenylalanine, and once after drinking a nutritionally balanced mixture. In the balanced drink session, statistically significant connectivity between the frontal lobes and striatum was observed during set shifting, and the greater the prefrontostriatal connectivity, the faster the response time after a shift. Neither of these associations were observed after dopamine depletion. Moreover, dopamine depletion also reduced the degree of deactivation in areas normally suppressed during attention-demanding tasks, including the medial prefrontal cortex, posterior cingulate cortex, and hippocampus. Together, these results suggest that functional connectivity between the frontal lobes and basal ganglia during set shifting contributes to more efficient performance and that dopamine modulates this corticostriatal connectivity.