Purpose Somatosensory information associated with speech articulatory movements affects the perception of speech sounds and vice versa, suggesting an intimate linkage between speech production and perception systems. However, it is unclear which cortical processes are involved in the interaction between speech sounds and orofacial somatosensory inputs. The authors examined whether speech sounds modify orofacial somatosensory cortical potentials that were elicited using facial skin perturbations. Method Somatosensory event-related potentials in EEG were recorded in 3 background sound conditions (pink noise, speech sounds, and nonspeech sounds) and also in a silent condition. Facial skin deformations that are similar in timing and duration to those experienced in speech production were used for somatosensory stimulation. Results The authors found that speech sounds reliably enhanced the first negative peak of the somatosensory event-related potential when compared with the other 3 sound conditions. The enhancement was evident at electrode locations above the left motor and premotor area of the orofacial system. The result indicates that speech sounds interact with somatosensory cortical processes that are produced by speech-production-like patterns of facial skin stretch. Conclusion Neural circuits in the left hemisphere, presumably in left motor and premotor cortex, may play a prominent role in the interaction between auditory inputs and speech-relevant somatosensory processing.

Many older adults experience declines in auditory and cognitive abilities that negatively affect language comprehension, including spoken word recognition. In the case of auditory function, poor neural responses to sound at the earliest stages of auditory processing may adversely affect phoneme identification, and ultimately, lexical access. Declines in cognitive functions, such as inhibitory control or working memory, may also impede word recognition. Furthermore, complex interactions between auditory and cognitive declines make it difficult to distinguish these possible causes of age differences in speech perception. We review age‐related changes in spoken word recognition, with respect to current models of this process. Then, we invoke frameworks of sensory–cognitive compensation and argue that online, sensitive measures of sensory processing and of comprehension are important in distinguishing between effects of sensory and cognitive decline. We conclude that investigations of spoken word recognition in older listeners must carefully assess listener differences at early levels of auditory processing, in conjunction with cognitive abilities.

Previous work has demonstrated a relationship between age-related declines in inhibitory control and difficulties identifying words of low lexical frequency and high neighborhood density (Sommers & Danielson, 1999). We hypothesized that declines in consistency of the auditory brainstem response (ABR; neural response to a repeated sound; Anderson et al., 2012) might also impede lexical access in older adults. We measured audiometric thresholds, ABR consistency, vocabulary, inhibitory control, and working memory in two groups (younger: 18-23yo, n = 41; older: 54-76yo, n = 41). We used mean target fixation proportion from 200 to 750 ms after word onset in a visual world task as a proxy for lexical access speed as listeners identified spoken words (varying on low/high: lexical frequency, neighborhood density, and cohort density; Magnuson et al., 2007). ABR consistency significantly predicted speed of word identification across variations in neighborhood and cohort densities, but contra previous findings, cognitive measures did not improve model fits. Interactions involving age, vocabulary, and lexical frequency suggest age-related linguistic expertise influences lexical access of uncommon words. We conclude that older adults exhibit increases in phonological competition due to declines in auditory encoding, suggesting that a consistent neural response to sounds leads to more efficient speech processing and lexical access.

The comprehension of spoken language is a complex skill that requires the listener to map the acoustic input onto the meaningful units of speech (phonemes, syllables, and words). At the sentence level, the listener must detect the syntactic structure of the utterance in order to determine the semantic relationships among the spoken words. Each higher level of analysis is thus dependent on successful processing at the prior level, beginning with perception at the phoneme and word levels. Unlike reading, where one can use eye movements to control the rate of input, speech is a transient signal that moves past the ears at an average rate of 140 to 180 words per minute. Although seemingly automatic in young adults, comprehension of speech can represent a greater challenge for older adults, who often exhibit a combination of reduced working memory resources and slower processing rates across a number of perceptual and cognitive domains. An additional challenge arises from reduced hearing acuity that often occurs in adult aging. A major concern is that, even with only mild hearing loss, the listening effort required for success at the perceptual level may draw resources that would ordinarily be available for encoding what has been heard in memory, or comprehension of syntactically complex speech. On the positive side, older adults have compensatory support from preserved linguistic knowledge, including the procedural rules for its use. Our understanding of speech perception in adult aging thus rests on our understanding of such sensory-cognitive interactions.