Decline and fall: A biological, developmental, and psycholinguistic account of deliberative language processes and ageing

Abstract

Background. This paper reviews the role of deliberative processes in language-those language processes that require central resources, in contrast to the automatic processes of lexicalisation, word retrieval, and parsing. Aims. We describe types of deliberative processing, and show how these processes underpin high-level processes that feature strongly in language. We focus on metalinguistic processing, strategic processing, inhibition, and planning. We relate them to frontal-lobe function and the development of the fronto-striate loop. We then focus on the role of deliberative processes in normal and pathological development and ageing and show how these processes are particularly susceptible to deterioration with age. In particular, many of the commonly observed language impairments encountered in ageing result from a decline in deliberative processing skills rather than in automatic language processes. Outcomes & Results. We argue that central processing plays a larger and more important role in language processing and acquisition than is often credited. Conclusions. Deliberative language processes permeate language use across the lifespan. They are particularly prone to age-related loss. We conclude by discussing implications for therapy.

Superior longitudinal fasciculus and language functioning in healthy aging

“…It is believed that with the inclusion of more subjects over the age of 70 this pattern of decline would be evident. This is comparable to a theory of language and aging put forth by Harley et al (2011) who argued that aging is associated with a decline in deliberative processing skills rather than automatic language processes, which do not demand attention. Deliberative processing requires general executive resources and depends on the integrity of brain areas outside traditional language regions, most notably the frontal lobes.…”

“…It involves the recruitment of more general cognitive processes, such as planning, strategy, and suppression for language use. Harley et al (2011) proposed that age-related deterioration of the frontal lobes has profound effects on deliberative processing and is responsible for language difficulties experienced by older adults.…”

Ageing makes us dyslexic

“…All three groups performed close to ceiling at reading and understanding words (all p < 0.05). The PAT and PALPA data (Appendix 2) confirmed our earlier (Harley et al, 2011) finding that PD group performed significantly worse (p <0.05) than the TAAs, and the TAAs in turn performed worse than the HYAs (p < 0.01) on the PAT Phonological Abilities Test (Muter, Hulme, & Snowling, 1997). For PALPA, as expected the pattern of results was mixed: tasks that tapped PA, such as written and auditory rhyme judgement, showed a significant impairment in the performance of the PD group.…”

“…It is well known that ageing affects spoken language production, particularly word retrieval, while leaving the comprehension of spoken and written language relatively intact (Burke & Shafto, 2004;Cohen & Faulkner, 1986;Harley, Jessiman, & MacAndrew, 2011). Very little is known however about how ageing affects reading.…”

“…We also showed that the degree of impairment is correlated with measures of executive processing and frontal-lobe efficiency in both groups and with the severity of the disease in the PD group (Harley, Jessiman, & MacAndrew, submitted). We argue that while much of language processing proceeds automatically without drawing heavily on attentional resources and making use of wellknown neural pathways largely dedicated to language, tasks that involve a metalinguistic aspect, where language or language processing are temporarily the attentional focus, require more resources and place more general neural demands, particularly on executive processes known to be housed in the frontal lobes of the brain; we call these types of processes deliberative language (Harley et al, 2011;Rogalsky, & Hickok, 2011). Phonological awareness tasks are a clear example of processing involving executive processing, so depend on the integrity of the frontal lobes, areas thought to be particularly prone to the effects of typical ageing (West, 1996) and greatly affected by the deterioration of the frontostriate loop in PD (Harley, et al, 2011).…”