Activity of laryngeal afferents during respiration, evoked vocalization, and paralysis I. Internal superior laryngeal nerve afferent activity during respiration and evoked vocalization in cats

The purpose of this project was to identify and categorize patterns of acti vity of the internal branch of the superior laryngeal nerve during vocaliza tion evoked by midbrain stimulation in cats anesthetized with alpha -chlora lose. Unit activity was isolated from the cut distal end of the internal br anch of the superior laryngeal nerve by means of floating bipolar electrode s that retained their contact with nerve fibers despite movement due to voc alization. The phases of respiration and vocalization were determined with a diaphragm electromyogram, a photoglottogram, and a microphone recording. Five groups of discrete afferent activities were defined according to relat ionships between the spike activity and the phases of vocalization. Group 1 cell activity peaked just before phonation. during expiratory airflow (n = 26). Group 2 cells (n = 19) followed a vocal fold vibratory pattern during phonation. Group 3 cell activity (n = 6) peaked during phonation. but did not follow; vocal fold vibration. Group 4 cells in = 3) were active during inspiration between phonations. Group 5 cells (n = 4) showed both inspirato ry and expiratory modulation. These results indicate that laryngeal afferen t activity responds to phonation-specific events during vocalization. This stereotyped afferent information might be used by the central nervous syste m to modulate vocalization.