Functional MRI of sensory motor cortex: comparison between finger-to-thumb and hand squeeze tasks

An important imaging technique that has advanced decision-making for noninvasive preoperative evaluation is functional magnetic resonance imaging (fMRI). Preoperative fMRI imaging based on blood oxygenation level dependent (BOLD) fMRI is routinely used to map a variety of eloquent cortex brain functions such as language, visual, and sensory-motor regions.

The purpose of this study was to evaluate the regional volumes of sensory and motor cortex (SMC) activation by two widely used fMRI motor tasks: a simple hand squeeze (HS) versus a more complex finger-to-thumb (FTT) opposition.

Ten right-handed (five males; five females) subjects were studied using a block design BOLD fMRI technique at 1.5T. A region of interest analysis was performed in the right and left SMC following a HS and FTT task with the dominant right hand.

Results show the total volume of motor and sensory activation for ipsilateral and contralateral areas for the FTT task was statistically larger than the HS task (P= .02).

Due to the greater degree of activation of the SMC with the FTT task, we suggest use of this task over the HS task if a patient can adequately perform the more complex FTT task. The greater SMC activation using FTT task compared to the HS task was primarily due to an increase in activation in the post-central sensory cortex. There was less lateralization, and therefore a greater degree of bilateral SMC activation, in the FTT task compared to the HS task. These results show the importance of optimization and fMRI task selection for presurgical SMC mapping.