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Date of Graduation
Doctor of Philosophy (PhD)
Department of Communication Sciences and Disorders
Erin G. Piker
Christopher G. Clinard
With the aging population on the rise, the need for effective assessment tools to identify risk factors for falls among the elderly is paramount. One independent risk factor for falls is vestibular impairment, but the available vestibular diagnostic tests have limitations. A promising new methodology: amplitude-modulated tones to elicit a vestibular-evoked myogenic potential (AMcVEMP), offers a more detailed examination of vestibular (sacculo-collic reflex) functions. This method assesses non-linearities, synchrony, and magnitude, providing a more thorough evaluation compared to the conventional transient cVEMP. So far, AMcVEMP has only been utilized in young adults.
The current study aimed to investigate the impact of age on the AMcVEMP temporal modulation transfer function (TMTF), determine the shape and limit of the AMcVEMP TMTF, and assess non-linearity across a range of modulation frequencies. The study included 49 healthy participants, categorized into three age groups. AMcVEMP responses were elicited using a carrier-frequency of 500 Hz and 10 modulation frequencies. An FFT-based approach was employed to analyze the responses, focusing on amplitude, signal-to-noise ratio (SNR), phase coherence (PC), and non-linearity. To measure non-linearity, harmonics of the modulation frequencies were analyzed.
The AMcVEMP responses exhibited characteristics consistent with saccular rectification. The AMcVEMP amplitude, SNR, and PC reduced with increasing age. The effects of age were less pronounced for PC, showing 100% response rates among older adults. Further, AMcVEMP TMTF range reduced with age for all measures. The shape of the AMcVEMP TMTF resembled bandpass filter among young adults and got narrower with age. Lastly, for the non-linearity measures, harmonics were robust in most young, some middle-aged and fewer older adults, indicating loss of non-linearity with aging.
AMcVEMP offers several advantages in assessing older adults compared to conventional cVEMP: higher response rates and the ability to examine and quantify the magnitude, synchrony, and non-linearity from the sacculo-collic reflex. This study advances our overall understanding of age-related changes in the vestibular system. Further utility of AMcVEMP in clinical populations will advance our comprehension of vestibular pathophysiology. Furthermore, linking vestibular non-linearity with functional balance may facilitate the development of strategies to mitigate the risk of falls among older adults.
Jha, Raghav H., "Effects of age on amplitude-modulated cVEMP temporal modulation transfer function" (2023). Dissertations, 2020-current. 107.