The association between frontal-striatal connectivity and sensorimotor control in cocaine users

Abstract

Background: In addition to cognitive and emotional processing dysfunction, chronic cocaine users are also impaired at simple sensorimotor tasks. Many diseases characterized by compulsive movements, repetitive actions, impaired attention and planning are associated with dysfunction in frontal-striatal circuits. The aim of this study was to determine whether cocaine users had impaired frontal-striatal connectivity during a simple movement task and whether this was associated with sensorimotor impairment.

Methods: Functional MRI data were collected from 14 non-treatment seeking cocaine users and 15 healthy controls as they performed a finger-tapping task. Functional coupling was quantified by correlating the timecourses of each pair of anatomically connected regions of interest. Behavioral performance was correlated with all functional coupling coefficients.

Results: In controls there was a significant relationship between the primary motor cortex and the supplementary motor area (SMA), as well as the SMA and the dorsal striatum during ongoing movement. Cocaine users exhibited weaker fronto-striatal coupling than controls, while the cortical-cortical coupling was intact. Coupling strength between the SMA and the caudate was negatively correlated with reaction time in the users.

Conclusions: The observation that cocaine users have impaired cortical-striatal connectivity during simple motor performance, suggests that these individuals may have a fundamental deficit in information processing that influences more complex cognitive processes.

Figure 1

Functional coupling in motor related regions during ongoing finger-tapping. Controls and non-treatment seeking cocaine users performed a sequential finger tapping task with their dominant right hand. The timecourse of the BOLD signal was extracted from seven regions of interest that are modulated by the task (M1-primary motor cortex, SMA-supplementary motor area, ACC- anterior cingulate cortex, C-caudate, P-putamen, T-thalamus, Cb-cerebellum). Cross correlation of the time courses in each of these anatomically connected regions revealed significant relationships between several of the pairs in the controls (A, green lines, p<0.05) and cocaine users (B, green lines, p<0.05). Between group comparisons revealed a significantly lower correlation between the frontal-striatal regions in the cocaine users (B, red lines, p<0.05).

Figure 2

Relationship between SMA-caudate coupling and reaction time in cocaine users. The line of best fit is shown (r = −0.51, p<0.05).