title: The effect of task difficulty on motor performance and frontal-striatal connectivity in cocaine users.
abstract: There is growing recognition that chronic cocaine users have alterations in sensorimotor control that are positively related to low frontal-striatal connectivity within the motor system. These frontal-striatal motor circuits however, are modulated by circuits governing attention, which are also disrupted in cocaine users. This study's aim was to determine if sensorimotor control deficits are positively related to the difficulty of a motor task or exist independent of the increasing cognitive demand.
  
  
  
  Functional MRI data was collected from 40 individuals (20 non-treatment seeking chronic cocaine users, 20 age and gender matched non-drug using controls) as they mimicked an unpredictable finger-tapping sequence at various speeds. Dependent measures included task accuracy, percent BOLD signal change in sensorimotor regions of interest (ROIs), and functional connectivity (temporal correlations) between ROIs.
  
  
  
  In both groups, as speed increased, the BOLD signal change increased in the primary motor cortex, supplementary motor area (SMA), cerebellum, and anterior cingulate cortex. Compared to controls, cocaine user SMA-Caudate and ACC-Putamen connectivity was lower at all speeds in the contralateral hemisphere. Furthermore, as speed increased there was a decrease in connectivity between additional ROI pairs among users.
  
  
  
  These data support previous observations of sensorimotor performance deficits and dorsal frontal-striatal connectivity impairments among cocaine users. While previous studies demonstrate these deficits when performing a finger-tapping task at a single speed, we show that these same impairments exist at multiple levels of task difficulty. These data suggest that previously observed frontal-striatal connectivity in cocaine users during sensorimotor task performance are stable and not directly related to cognitive demands of the task.
authors.affiliation: Department of Psychiatry and Behavioral Sciences, Medical University of South Carolina, Charleston, SC, 29425, USA.
authors.forename: Daniel H
authors.initials: DH
authors.lastname: Lench
authors.affiliation: Department of Psychiatry and Behavioral Sciences, Medical University of South Carolina, Charleston, SC, 29425, USA.
authors.forename: William
authors.initials: W
authors.lastname: DeVries
authors.affiliation: Department of Psychiatry and Behavioral Sciences, Medical University of South Carolina, Charleston, SC, 29425, USA. Electronic address: hanlon@musc.edu.
authors.forename: Colleen A
authors.initials: CA
authors.lastname: Hanlon
mesh_terms: D000328:Adult; D001288:Attention / Q000187:drug effects* / Q000502:physiology*; D002531:Cerebellum / Q000187:drug effects / Q000503:physiopathology; D003042:Cocaine / Q000633:toxicity*; D019970:Cocaine-Related Disorders / Q000503:physiopathology* / Q000523:psychology; D003342:Corpus Striatum / Q000187:drug effects* / Q000503:physiopathology*; D005260:Female; D005625:Frontal Lobe / Q000187:drug effects* / Q000503:physiopathology*; D006179:Gyrus Cinguli / Q000187:drug effects / Q000503:physiopathology; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000503:physiopathology; D009415:Nerve Net / Q000187:drug effects* / Q000503:physiopathology*; D011597:Psychomotor Performance / Q000187:drug effects* / Q000502:physiology*; D011699:Putamen / Q000187:drug effects / Q000503:physiopathology; D055815:Young Adult
chemical_list: D003042:Cocaine
keywords: Addiction; Cognitive; Connectivity; Neural networks; Neuroimaging; Sensorimotor