Last year we became concerned that during transcranial magnetic stimulation with the cadwell cortical coil, many responses could be due to concurrent stimulation of the periperal nerves with early ipsilateral responses being due to stimulation of the ipsilateral recurrent laryngeal nerve and later R1 responses due to stimulation of afferents contained in the superior laryngeal nerve. A peripheral nerve magnetic stimulation study with the same coil demonstrated that similar responses to those seen during cortical stimulation could be explained by peripheral nerve stimulation of the laryngeal nerves. by converting to a smaller coil, the figure eight coil, we were able to demonstrate that cortical responses could be elicited without stimulating the peripheral nerves. In fact, this smaller coil was not capable of eliciting nerve responses even when stimulating at the neck perhaps because the magnetic field does not penetrate deep enough into the neck tissues. Studies have demonstrated that different coils should be used for cortical and peripheral nerve studies when assessing the neural control of the larynx. Studies aimed at examining brain activation patterns in normal volunteers during speech and voice activities using Positron Emission Tomography have been initiated.
Our aim i s to determine the degree to which different speech and voice tasks are dominant in the left hemisphere in normal speakers. The H2150 technique is being used to estimate blood flow over very brief periods of time, approximately 40 seconds. Eight very short studies are being conducted in one session with a subject, comparing activation patterns across tasks. Normal controls brain activation patterns are being compared across different speech and voice tasks, and stutterers brain activation patterns are being compared during fluent and non-fluent speech.
