Optimized Activation of the Primary Sensorimotor Cortex for Clinical Functional MR Imaging
Karsten Papke
,a,
Peter Reimera,
Bernhard Rengera,
Gerhard Schuierera,
Stefan Knechta,
Matthias Schulza and
Walter Heindela
a From the Departments of Clinical Radiology (K.P., P.R., B.R., G.S., S.S., W.H.) and Neurology (S.K.), University of Münster, Germany.
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FIG 1. Correlation coefficient maps of a representative subject show the activation patterns elicited by the four different paradigms.
A and B, In paradigms 1 (A) and 2 (B), unilateral finger tapping is compared with rest (right hand versus rest and left hand versus rest, respectively). Maximal activation is located contralateral to the side of motion in the left (paradigm 1) and right (paradigm 2) hemisphere, respectively. However, ipsilateral activation is also in the PMA (small arrowheads) and SMA (large arrowhead) (the SMA is only marginally met in the selected slice).
C, In paradigm 3 (both hands versus rest), activity is distributed nearly symmetrically between the two hemispheres. Primary as well as nonprimary motor areas are activated, making the precise identification of the central sulcus difficult.
D, In paradigm 4, right-handed motion is compared with left-handed motion (red indicates positive correlation of the voxels' signal time course with the task-derived reference function; blue, negative correlation). Functional activity is focused on the primary sensorimotor cortex around the central sulcus near the motor knob (arrowheads), reflecting the primary motor hand area (20).
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FIG 2. Distribution of activated voxels among the different areas of interest, expressed as a percentage in relation to the total number of activated voxels in the examined brain volume, averaged across subjects.
A, Paradigm 1 (right hand versus rest).
B, Paradigm 2 (left hand versus rest).
C, Paradigm 3 (both hands versus rest).
D, Paradigm 4 (right versus left hand).
Whereas in paradigms 1 through 3, 12% to 25% of activated voxels are located outside the central region, the amount of extracentral activation is lowest in paradigm 4 (<5%). In contrast, paradigm 4 yields the highest proportion of activated voxels in the primary sensorimotor cortex along the central sulcus, facilitating its reliable identification.
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FIG 3. A–C, Signal time courses of the left primary sensorimotor cortex around the central sulcus (A), the PMA (B), and the SMA (C), averaged across subjects. Task-related signal changes along the central sulcus are highly specific to contralateral hand motion (A), whereas the nonprimary motor areas are activated by ipsilateral and contralateral hand motion alike. This holds particularly true for the SMA, in which there was no significant difference between the signal changes induced by unilateral or bilateral hand motion. As a result, no task-related signal changes can be observed in paradigm 4 (right versus left-handed finger tapping), apart from small signal peaks associated with changing the side of hand motion
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AJNR - American Journal of Neuroradiology