The role of ipsilateral primary motor cortex (M1) in hand motor control during complex task performance remains controversial. Bilateral M1 activation is inconsistently observed in functional (f)MRI studies of unilateral hand performance. Two factors limit the interpretation of these data. As the motor tasks differ qualitatively in these studies, it is conceivable that M1 contributions differ with the demand on skillfulness. Second, most studies lack the verification of a strictly unilateral execution of the motor task during the acquisition of imaging data. Here, we use fMRI to determine whether ipsilateral M1 activity depends on the demand for precision in a pointing task where precision varied quantitatively while movement trajectories remained equal. Thirteen healthy participants used an MRI-compatible joystick to point to targets of four different sizes in a block design. A clustered acquisition technique allowed simultaneous fMRI/EMG data collection and confirmed that movements were strictly unilateral. Accuracy of performance increased with target size. Overall, the pointing task revealed activation in contralateral and ipsilateral M1, extending into contralateral somatosensory and parietal areas. Target size-dependent activation differences were found in ipsilateral M1 extending into the temporal/parietal junction, where activation increased with increasing demand on accuracy. The results suggest that ipsilateral M1 is active during the execution of a unilateral motor task and that its activity is modulated by the demand on precision.
Twenty-six children and adolescents who were unable to produce /r/ correctly were administered a listening task. They were asked to listen to a tape of 200 words containing /r/ in a variety of contexts. Half of the words had been produced by the subjects themselves and half by another speaker who produced /r/ incorrectly. In addition, half of the words from each speaker contained an /r/ that was incorrect whereas the other half contained an /r/ that was edited so that it sounded correct. Subjects made judgments for each word regarding the correctness of the /r/ and the identity of the speaker. Subjects performed significantly more poorly in judging their own incorrect utterances than on any other category of utterance. When judging their own "corrected" utterances, they were more successful at deciding whether the /r/ was correct than in identifying the identity of the speaker. The results provide support for a relationship between speech perception and production in some individuals with a phonological disorder.
Biofeedback in the form of the visual display from the monitor of a real-time spectrograph was presented to a 10-year-old boy and a 14-year-old girl who had been unable to attain correct production of /r/ despite years of treatment. Both perceptual ratings and acoustic measures were made of the clients' productions of /r/ before and after treatment with the spectrograph. The results indicated that children and adolescents can use this type feedback to attain correct production of /r/ when other methods have failed. Potential reasons for the success of this approach are discussed.
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