Understanding and using language is critical for everyday cognition, so it is not surprising that older adults report language problems – most commonly word-finding difficulties during language production – as being among their biggest worries. However, while some abilities like word production do tend to decline with age, most aspects of language comprehension are well-preserved. This pattern of both decline and preservation is surprising given that broadly similar brain regions in the frontal and temporal lobes underpin both production and comprehension. Our research focuses on understanding why language abilities like comprehension can remain intact while others – such as word-finding – appear to decline.
An important possibility is that some abilities are preserved across the lifespan as a result of neural recruitment and compensation. The brain system underpinning language normally includes frontal and temporal regions in the left hemisphere, but this system is very dynamic and task demands can lead to increased activity and to the recruitment of right hemisphere regions. The language abilities that are well preserved may be those where flexible neural recruitment is more successful.
Another possibility is that declining language abilities are those that most rely on other non-language cognitive abilities (such as attention and working memory) which themselves tend to change with age. Because the Cam-CAN project will gather a number of behavioural and neural measures across a broad range of cognitive domains, we will be able to assess whether specific language and non-language abilities change together and how this relates to patterns of neural activity and neural recruitment.
Current behavioural examinations of language comprehension involve a task where subjects listen to sentences that manipulate syntactic and semantic aspects of the sentence. Preliminary results suggest that, in accordance with previous findings, there is no overall age effect on syntactic aspects of comprehension(see figure below, left):
Production tasks centre around confrontation naming in response to pictures of objects and people. These data will eventually be used to examine specific aspects of semantic and phonological processing during object naming, and to understand the specific problems that older adults develop with retrieving proper names. Preliminary results replicate previous findings that age affects confrontation naming accuracy, with decreasing naming accuracy across the age range (see figure below, right):