VOCAL TREMORS AND STUTTERING: AN HYPOTHESIS
Netsell (1990) presented the hypothesis that some vocal tremors are caused by an increased activity of the autonomic nervous system (ANS). In the figure below, ANS activity increases above a threshold that induces an amplitude increase in an inherent neural oscillation (OSC). In turn, the increased OSC amplitude results in a vocal tremor at the same frequency (~5Hz). A similar phenomenon may be operating in some people who stutter.