Parametric analysis of rate-dependent hemodynamic response functions of cortical and subcortical brain structures during auditorily cued finger tapping: a fMRI study.
A multitude of functional imaging studies revealed a mass activation effect at the level of the sensorimotor cortex during repetitive finger-tapping or finger-to-thumb opposition tasks in terms of either a stepwise or a monotonic relationship between movement rate and hemodynamic response. With respect to subcortical structures of the centralmotor system, there is, by contrast, some preliminary evidence for nonlinear rate/response functions within basal ganglia and cerebellum. To further specify these hemodynamic mechanisms, functional magnetic resonance imaging (fMRI) was performed during a finger-tapping task in response to acoustic stimuli (six different frequencies: 2.0, 2.5, 3.0, 4.0, 5.0 and 6.0 Hz; applied via headphones). Passive listening to the same auditory stimuli served as a control condition. Statistical evaluation of the obtained data considered two approaches: categorical and parametric analysis. As expected, the magnitude of the elicited hemodynamic response within left sensorimotor cortex (plateau phase at frequencies above 4 Hz) and mesiofrontal cortex paralleled movement rate. The observed bipartite mesial response pattern, most presumably, reflects functional compartmentalization of supplementary motor area (SMA) in a rostral component (pre-SMA) and in a caudal (SMA proper) component. At the level of the cerebellum, two significant hemodynamic responses within the hemisphere ipsilateral to the hand engaged into finger tapping (anterior/posterior quadrangular lobule and posterior quadrangular lobule) could be observed. Both activation foci exhibited a stepwise rate/response function. In accordance with clinical data, these data indicate different cerebellar contributions to motor control at frequencies below or above about 3 Hz, respectively. Caudate nucleus, putamen, and external pallidum of the left hemisphere displayed, by contrast, a negative linear rate/response relationship. The physiological significance of these latter findings remains to be clarified.
Riecker
Axel
A
Department of Neurology, University of Tuebingen, Hoppe-Seyler-Strasse 3, D-72076, Tuebingen, Germany. axel.riecker@med.uni-tuebingen.de
Wildgruber
Dirk
D
Mathiak
Klaus
K
Grodd
Wolfgang
W
Ackermann
Hermann
H
D000328:Adult; D001288:Attention / Q000502:physiology*; D001479:Basal Ganglia / Q000098:blood supply* / Q000502:physiology; D001931:Brain Mapping; D002531:Cerebellum / Q000098:blood supply* / Q000502:physiology; D002540:Cerebral Cortex / Q000098:blood supply* / Q000502:physiology; D003463:Cues; D005260:Female; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D010101:Oxygen Consumption / Q000502:physiology; D010898:Pitch Perception / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology