Unilateral/Bilateral Hand Motion

Lubdha M. Shah, MD

Key Facts

Imaging Anatomy

Unilateral sequential finger tapping results in robust activity within cortex surrounding superior lateral central sulcus in expected somatotopic location for finger/hand
- Center of “hand knob” in precentral gyrus has been identified as landmark for hand area of primary motor cortex
Supplementary motor area and premotor activation may also be seen

Design

4-minute block design with visual stimulus presentation and “stop”/“go” commands
Different variations of paradigm
- Repetitive finger tapping or hand squeezing results in robust premotor and primary sensorimotor activation
- Tapping of thumb to each finger in sequential manner at self-paced rate on “go” command until “stop” command

Applications

Presurgical motor mapping for lesions in sensorimotor cortex
Patients with neurological cortical or spinal deficits may not be able to carry out finger-tapping tasks
- Passive sensory stimulus may be used in subjects unable to perform hand movement
Subjects with abnormal evoked cerebral blood oxygenation changes due to arteriovenous malformation, stroke, or tumor may have false-negative activations (i.e., marked reductions of activation volumes) in BOLD imaging

(Left) Axial fMRI in a neurologic format shows activation in the right sensorimotor region

due to a left-thumb flexion task. There is also activation in the supplementary motor area (SMA)

. Unilateral sequential finger tapping results in robust activity within the cortex surrounding the superior lateral central sulcus in the expected somatotopic location for the finger/hand. (Right) 3D surface-rendered image shows overlay of activation in the right sensorimotor region

due to the left-thumb flexion task.

(Left) Axial fMRI in a neurologic format shows activation in the left sensorimotor region

due to a right-thumb flexion task. There is also activation in the SMA

. (Right) 3D surface-rendered image shows an overlay of activation in the left sensorimotor region

due to the right-thumb flexion task. Many studies have found high correlations between intraoperative cortical stimulation mapping with preoperative motor fMRI.