RESUMO
This single participant functional magnetic resonance imaging (fMRI) study investigates the effects of tapping force and speed on the activation characteristics in motor-related cortices during bilateral self-paced tapping of hand fi ngers. The participant performed four types of self-paced hand fi nger tapping which are soft-slow (SS), soft-fast (SF), hard-slow (HS) and hard-fast (HF) in an fMRI scan. A general linear model (GLM) was implemented in generating brain activation. Statistical inferences were then made about the brain activations using Gaussian random fi eld theory (RFT) at corrected signifi cant level (α = 0.05), given that there is no activation. The results indicate that the brain coordinates bilateral selfpaced tapping of hand fi ngers with the involvement of motor-related cortices which are bilateral precentral gyrus (PCG), bilateral cerebellum and supplementary motor area (SMA). The increase in tapping force accentuate signifi cant activation (p < 0.05 corrected) in bilateral PCG (Brodmann Area (BA) 6) in accordance with its function in triggering motor action such as controlling the tapping force. The increase in tapping speed causes a signifi cant (p < 0.05 corrected) increase in brain activation only in somatosensory associated region in the right superior parietal lobule (SPL) or right BA7. This suggests that SPL plays important roles in coordinating purposeful, skilled movements
RESUMO
Optic ataxia is characterized by an impaired visual control of the direction of arm reaching to a visual target, accompanied by defective hand orientation and grip formation. In humans, optic ataxia is associated with lesions of the superior parietal lobule, which also affect visually guided saccades and other forms of eye-hand coordination. A 67-year-old woman presented with sudden, unilateral, direct optic ataxia in the right homonymous half field and saccadic abnormalities which consisted of prolonged latency, undershoot dysmetria, and decreased velocity. Brain MRI showed a left parieto-occipital watershed infarction. It is suggested that lesions of the superior parietal lobule and the adjacent parietal eye field are responsible for optic ataxia and saccadic abnormalities, respectively.