Single-Participant STS-fMRI Brain Activation in the Cerebral Cortices during Passive and Active Listening: A Technical Note
A functional magnetic resonance imaging (fMRI) was conducted on a healthy male participant to investigate brain activations during passive and active listening. The fMRI scans were carried out to test the hypothesis that there is no significant difference in brain activation between active and baseline conditions. The participant was subjected to two types of scan which were the anatomical and functional scans in order to produce the Tl and T2* weighted images respectively. A sparse temporal sampling (STS) was used in order to eliminate the effects of sound generated by the scanner on the functional images. Two different experimental conditions were separately executed. The first condition requires the participant to mindfully listen to a simple arithmetic instruction (e.g. one-plus-two-plus-three plus-four) – known as passive listening. In the second condition, the participant was given the same series of arithmetic instruction and was required to listen and perform the calculation – known as active listening. The data were analysed using statistical parametric mapping (SPM2). The results indicate differences in brain activation between passive and active listening. The activated cortical regions during passive listening, as obtained from the first condition are symmetrical in the left and right temporal and parietal lobes covering the cortical auditory areas. For the second condition, which was listening together with performing simple arithmetic calculation, brain activations were symmetrically observed in the left and right frontal lobes, limbic lobe as well as in the left and right parietal and temporal lobes. The point of maximum signal intensity during passive listening has been shifted to a new coordinates during active listening. It was also observed that the number of activated voxels (NOV) in the second condition (1736 voxels) have been reduced as compared to that of the first condition (2342 voxels). The results obtained strongly suggest the existence of functional specialisation of human brain; which means the designation of a specific brain region for a specific function. More activation clusters in the second condition also indicate different networks for the two conditions. These networks clearly suggest the existence of functional connectivity between activation areas during passive and active listening while performing a simple arithmetic task. The STS-fMRI acquisition and SPM analysis were successful allowing brain activation due to verbal and cognitive stimulation to be interpreted based on current knowledge of brain function.
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