Speakers respond automatically and rapidly to compensate for brief perturbations of pitch in their auditory feedback. The specific adjustments in vocal output require integration of brain regions involved in speech-motor-control in order to detect the sensory-feedback-error and implement the motor-correction. Cortical regions involved in the pitch-reflex phenomenon are highly vulnerable targets of network disruption in Alzheimer's disease (AD). We examined the pitch-reflex in AD patients (n=19) compared to an age-matched control group (n=16). We measured the degree of behavioral compensation (peak-compensation) and the extent of the adaptive response (pitch-response-persistence). Healthy-controls reached a peak-compensation of 18.7±0.8 cents, and demonstrated a sustained compensation at 8.9±0.69 cents. AD patients, in contrast, demonstrated a significantly elevated peak-compensation (22.4±1.2 cents, P<0.05), and a reduced sustained response (pitch-response-persistence, 4.5±0.88 cents, P<0.001). The degree of increased peak-compensation predicted executive dysfunction, while the degree of impaired pitch-response-persistence predicted memory dysfunction, in AD patients. The current study demonstrates pitch-reflex as a sensitive behavioral index of impaired prefrontal modulation of sensorimotor integration, and compromised plasticity mechanisms of memory, in AD.
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