- Email: [email protected]
Basal ganglia function in a sequential movement task
ABSTRACTS
Basal Ganglia Function in a Sequential M o v e m e n t Task
P. J. Jenningsl, 2, C. E. Stern 3, K. K. Kwong 3, J. J. Locascio 2, S. Corkin 2, B. R. Rosen 3 and R. G. Gonz~ilez 3 1 The Bunting Institute of Radcliffe College, Cambridge, MA, U.S.A. 2 Department of Brain and Cognitive Sciences and the Clinical Research Center, Massachusetts Institute of Technology, Cambridge, MA, U.SA. 3 Massachusetts General Hospital - NMR Center, Charlestown, MA, U.S.A. The ability to produce smooth and rapid sequential movements relies on intact basal ganglia function. One of the hallmark symptoms of Parkinson's disease is bradykinesia, or slow movement. Sequential movement consists of programming an ordered set of muscle commands, and executing those muscle commands. It has been proposed that the basal ganglia execute highly learned motor programs [1], switch among motor programs [2], and coordinate the programming of upcoming responses while executing a sequence [3]. This study examined basal ganglia function during a reaction time (RT) task with sequential keypress responses [3]. It tested specifically whether basal ganglia structures are (a) active during a sequential task, and (b) more active during response selection and programming (choice RT) than during response execution (simple RT).
Methods Five healthy subjects (age range [19 - 23], 2 males) performed a RT task with sequential keypress responses [3] under four conditions presented in 1-minute blocks during a 6-minute scan: choicebaseline, choice RT, simple baseline, simple RT, choiceRT, choice baseline. Stimuli were generated by computer and projected to a transluscent screen mounted in front of a tilted mirror above the subject's eyes. Subjects made responses using a microswitch keypad that had four unmarked horizontally aligned keys. Keypress accuracy and latency relative to stimulus onset were recorded. In the baseline conditions, subjects viewed stimuli but made no motor responses. Conventional and echo-planar MR images were collected using a 1.5-T scanner (GE Signa, ANMR), a receive-only RF quadrature head volume coil, and an asymmetric spin-echo sequence. Ten contiguous 7 mm axial slices (voxel size 3 mm x 3 mm x 7 mm) were selected with the inferior slices located through basal ganglia structures. T1weighted echo-planar images with the same orientation, slice thickness, and field of view as the functional scans were collected. Differences between the distributions of signal intensity values collected during choiceRT and choice baseline conditions were assessed using the KS statistic. The KS map and the high-resolution anatomical images were used to select a ROI through basal ganglia structures. The time series of mean image intensity values for the ROI were analyzed using autoregressive-integrated-moving average time series techniques to identify and remove autoregressive, linear, and polynomial effects, and to test the significance of contrasts between conditions.
Results and Conclusions Four of the 5 subjects showed significantly greater activation in basal ganglia structures during the choice RT condition than during the choice baseline condition (Figure 1). There was moderate intersubject variability in the precise location, but each subject showed activation in caudate, putamen, or globus pallidus. Basal ganglia structures were equally active in the simple RT and choiceRT conditions. These results suggest that the basal ganglia are important for the execution of sequential movements, and that the additional demands of selection and programming do not increase basal ganglia activation. The RT task with sequential responses may be a reliable way to use fMRI to examine task-related activation of basal ganglia structures in subjects with basal ganglia disease.
9
T Figure 1. Four of 5 subjects show basal ganglia activation in choice RT task (KS p < .000001 indicated in white).
References 1. Marsden, CD. Neurol. 1982, 32: 514-539. 2. Robertson, C., Flowers, KA. J. Neurol. Neurosurg. Psych. 1990, 53: 583-592. 3. Jennings, PJ. J. Motor Behavior. 1995, 27:310-324
$385
Basal Ganglia Function in a Sequential M o v e m e n t Task
P. J. Jenningsl, 2, C. E. Stern 3, K. K. Kwong 3, J. J. Locascio 2, S. Corkin 2, B. R. Rosen 3 and R. G. Gonz~ilez 3 1 The Bunting Institute of Radcliffe College, Cambridge, MA, U.S.A. 2 Department of Brain and Cognitive Sciences and the Clinical Research Center, Massachusetts Institute of Technology, Cambridge, MA, U.SA. 3 Massachusetts General Hospital - NMR Center, Charlestown, MA, U.S.A. The ability to produce smooth and rapid sequential movements relies on intact basal ganglia function. One of the hallmark symptoms of Parkinson's disease is bradykinesia, or slow movement. Sequential movement consists of programming an ordered set of muscle commands, and executing those muscle commands. It has been proposed that the basal ganglia execute highly learned motor programs [1], switch among motor programs [2], and coordinate the programming of upcoming responses while executing a sequence [3]. This study examined basal ganglia function during a reaction time (RT) task with sequential keypress responses [3]. It tested specifically whether basal ganglia structures are (a) active during a sequential task, and (b) more active during response selection and programming (choice RT) than during response execution (simple RT).
Methods Five healthy subjects (age range [19 - 23], 2 males) performed a RT task with sequential keypress responses [3] under four conditions presented in 1-minute blocks during a 6-minute scan: choicebaseline, choice RT, simple baseline, simple RT, choiceRT, choice baseline. Stimuli were generated by computer and projected to a transluscent screen mounted in front of a tilted mirror above the subject's eyes. Subjects made responses using a microswitch keypad that had four unmarked horizontally aligned keys. Keypress accuracy and latency relative to stimulus onset were recorded. In the baseline conditions, subjects viewed stimuli but made no motor responses. Conventional and echo-planar MR images were collected using a 1.5-T scanner (GE Signa, ANMR), a receive-only RF quadrature head volume coil, and an asymmetric spin-echo sequence. Ten contiguous 7 mm axial slices (voxel size 3 mm x 3 mm x 7 mm) were selected with the inferior slices located through basal ganglia structures. T1weighted echo-planar images with the same orientation, slice thickness, and field of view as the functional scans were collected. Differences between the distributions of signal intensity values collected during choiceRT and choice baseline conditions were assessed using the KS statistic. The KS map and the high-resolution anatomical images were used to select a ROI through basal ganglia structures. The time series of mean image intensity values for the ROI were analyzed using autoregressive-integrated-moving average time series techniques to identify and remove autoregressive, linear, and polynomial effects, and to test the significance of contrasts between conditions.
Results and Conclusions Four of the 5 subjects showed significantly greater activation in basal ganglia structures during the choice RT condition than during the choice baseline condition (Figure 1). There was moderate intersubject variability in the precise location, but each subject showed activation in caudate, putamen, or globus pallidus. Basal ganglia structures were equally active in the simple RT and choiceRT conditions. These results suggest that the basal ganglia are important for the execution of sequential movements, and that the additional demands of selection and programming do not increase basal ganglia activation. The RT task with sequential responses may be a reliable way to use fMRI to examine task-related activation of basal ganglia structures in subjects with basal ganglia disease.
9
T Figure 1. Four of 5 subjects show basal ganglia activation in choice RT task (KS p < .000001 indicated in white).
References 1. Marsden, CD. Neurol. 1982, 32: 514-539. 2. Robertson, C., Flowers, KA. J. Neurol. Neurosurg. Psych. 1990, 53: 583-592. 3. Jennings, PJ. J. Motor Behavior. 1995, 27:310-324
$385