Chuck Larson 1 , Donald Robin 2 , Jack Lancaster 2 , Peter Fox 2

1 Northwestern University, Communication Sciences and Disorders, Evanston

2 University of Texas Health Science Center, Research Imaging Center, San Antonio

Question:
The goal of the present study was to test the hypothesis that the laryngeal motor cortex is involved in generating vocal responses to perturbations in auditory feedback. It is well established that vocalizing subjects respond to pitch-shifted voice auditory feedback with a compensatory change in voice fundamental frequency (F0).  A previous study showed that a pitch-shift stimulus elicits a cricothyroid muscle and voice F0 response in 50 and 80 ms respectively. Based on these timing constraints, it was predicted that the cortex should become active in less than 50 ms following a pitch-shift stimulus. 

Methods:
In the present study, the laryngeal area of motor cortex was first identified from a sparse-sampling fMRI scanning protocol as subjects vocalized and received pitch-shifted voice feedback. A structural image of the brain was also created using fMRI techniques.  The coordinates of laryngeal motor cortex were then fed to a robotically controlled TMS system. The TMS stimulator coil was then positioned over laryngeal motor cortex, the position of which was verified by recording EMG potentials from the cricothyroid muscle with latencies of 10 – 12 ms following cortical TMS. Subjects then sustained vowel phonations while receiving short duration (200 ms) increases in pitch-shifted voice feedback in real time. Increases in pitch-shifted voice feedback generally cause a decrease in cricothyroid EMG and voice F0. Single TMS pulses timed to occur at specific intervals following pitch-shifted voice feedback (0, 10, 20, 30, 40, 50, 60 ms), caused an initial increase in voice F0 followed by a decrease. For each pitch-shift --- TMS interval condition, the average magnitude of the initial increase in the F0 was measured.

Results:
Reductions in the magnitude of the F0 response occurred with pitch-shift --- TMS intervals of 30 – 40 ms.  The reduction is thought to result from an interaction between the TMS pulse and the decrease in neural activity elicited by the upward pitch-shift stimulus.

Conclusions:
This interval coincides with the predicted time of laryngeal motor cortex excitation necessary to produce an increase in voice F0 following a pitch-shift stimulus. These results confirm the hypothesis that the pitch-shift reflex involves the cerebral cortex. 

Ken Roßlau 1 , Sibylle Herholz 2 , Arne Knief 1 , Christian Dobel 2 , Christo Pantev 2 , Antoinette am Zehnhoff-Dinnesen 1

1 Department of phoniatrics and pediatric audiology, university hospital, Münster

2 Institute of Biomagnetism and Biosingalanalysis, university hospital, Münster

Katrin Neumann 1 , Christian Kell 2 , Philippe Dejonckere 2,3

1 University of Frankfurt, Dept. of Phoniatrics and Pediatric Audiology, Frankfurt am Main

2 University of Frankfurt, Dept. of Neurology, Frankfurt am Main

3 University Medical Center Utrecht, Institute of Phoniatrics, Utrecht

Matthias Echternach 1 , Nadja Räss 2 , Johan Sundberg 3 , Bernhard Richter 4

1 Institut of Musicians Medicine, Freiburg University Medical Center, Freiburg

2 Jodellehrerin, , Einsiedeln

3 Department of Speech, Music and Hearing, KTH, Stockholm

4 Institue of Musicians Medicine, Freiburg University Medical Center, Freiburg