Auditory evoked responses were recorded in 16 normally hearing subjects in order to investigate the mechanisms underlying the generation of the 40 Hz steady-state response (SSR). In the first part of our study, auditory potentials were evoked by 0.1 ms clicks presented at 105 dB p.e. SPL with repetition rates of 7.9 (to obtain middle latency response, MLR), 20, 30, 40, 50, 60 Hz. In each subject predictions of the responses recorded at stimulus repetition rates of 30, 40, 50, 60 Hz were synthesized by superimposing MLRs at suitable time intervals. The calculated mean amplitude/rate and phase/rate functions behaved similarly for the recorded and predicted curves, showing the highest amplitude at 40 Hz and a linear increase of phase values when increasing the stimulus rate. Nevertheless the synthetic curves closely predicted amplitude and phase values of the recorded responses only at 40 Hz. At frequencies below 40 Hz, the mean amplitude of the predicted curve was lower than that of the recorded one while at frequencies above 40 Hz the mean amplitude was higher. Predicted phase values were found lagging at 30 Hz, and leading at 50 Hz and 60 Hz in comparison to phase values calculated on the recorded responses. Our findings suggest that a model based on the linear addition of transient MLRs is not able to adequately predict steady-state responses at stimulus rates other than at 40 Hz. Other mechanisms related to the recovery cycle of the activated system come into play in the steady-state response generation causing a decrease in amplitude and an increase in phase lag when increasing the stimulus repetition rate.

Previous studies have investigated the relationship between muscular tension, body posture, and voice quality. The aim of this paper is to study the postural pattern during voice production in healthy subjects compared with patients affected by voice disorders and in the same patients before and after vocal treatment by means of static posturography. Classic posturographic variables and spectral frequency analysis of body sway have been measured. Posturographic values in patients before vocal treatment and controls were within normal ranges but not homogeneous. Body sway significantly decreased during voice production in patients after voice training. Spectral frequency analysis of body sway showed a significantly decreased body sway at middle frequencies on the anteroposterior (y) plane during voice production after voice training. Our results would suggest that in patients affected by voice disorders rehabilitative treatment may cause an improvement of the body proprioceptive scheme and this improvement might be useful to evaluate the proper (ongoing) treatment.

No abstract

No abstract

A total of 39 patients with bilateral post-thyroidectomy vocal cord paralysis in adduction underwent CO 2 laser subtotal arytenoidectomies with removal of the posterior third of the false and true vocal cords. Total airway resistance (R tot ) evaluated before and 4-10 months after surgery showed marked preoperative impairment before and significant improvement after surgery (P < 0.05). In five patients revision surgery was performed due to a progressive impairment of respiratory function. A variable degree of voice breathiness was observed after surgery; the maximum phonation time mean values were lower than normal and peak sound pressure levels 63 ± 5 dB. In three cases aspiration was present in the first postoperative days, but swallowing dysfunctions disappeared within 1 week. Subtotal arytenoidectomy with removal of the posterior third of the true and false vocal folds was found to be a satisfactory surgical treatment for bilateral vocal cord paralysis in adduction. However, further research is still needed to define the surgical procedure able to balance respiratory, phonatory and sphincteric functions optimally.