Speech perception difficulties are common among elderlies; yet the underlying neural mechanisms are still poorly understood. New empirical evidence suggesting that brain senescence may be an important contributor to these difficulties has challenged the traditional view that peripheral hearing loss was the main factor in the etiology of these difficulties. Here, we investigated the relationship between structural and functional brain senescence and speech perception skills in aging. Following audiometric evaluations, participants underwent MRI while performing a speech perception task at different intelligibility levels. As expected, with age speech perception declined, even after controlling for hearing sensitivity using an audiological measure (pure tone averages), and a bioacoustical measure (DPOAEs recordings). Our results reveal that the core speech network, centered on the supratemporal cortex and ventral motor areas bilaterally, decreased in spatial extent in older adults. Importantly, our results also show that speech skills in aging are affected by changes in cortical thickness and in brain functioning. Age-independent intelligibility effects were found in several motor and premotor areas, including the left ventral premotor cortex and the right supplementary motor area (SMA). Age-dependent intelligibility effects were also found, mainly in sensorimotor cortical areas, and in the left dorsal anterior insula. In this region, changes in BOLD signal modulated the relationship between age and speech perception skills suggesting a role for this region in maintaining speech perception in older ages. These results provide important new insights into the neurobiology of speech perception in aging.

The manner and extent to which normal aging affects the ability to speak are not fully understood. While age-related changes in voice fundamental frequency and intensity have been documented, changes affecting the planning and articulation of speech are less well understood. In the present study, 76 healthy, cognitively normal participants aged between 18 and 93 years old were asked to produce auditorily and visually triggered sequences of finely controlled movements (speech, oro-facial, and manual movement). These sequences of movements were either (1) simple, in which at least two of the three movements were the same, or (2) complex, in which three different movements were produced. For each of the resulting experimental condition, accuracy was calculated. The results show that, for speech and oro-facial movements, accuracy declined as a function of age and complexity. For these movements, the negative effect of complexity on performance accuracy increased with age. No aging or complexity effects were found for the manual movements on accuracy, but a significant slowing of movement was found, particularly for the complex sequences. These results demonstrate that there is a significant deterioration of fine motor control in normal aging across different response modalities.

Older adults are not just slower than younger adults, they also exhibit specific articulatory difficulties. Although many physiological changes in orofacial functions occur in aging, only muscular endurance of the lips is related to age-related differences in speech production. This information is important for the development of speech interventions targeting older adults with speech motor disorders.