Revisiting the hypothesis of language retrogenesis from an evolutionary perspective.

Abstract

Objective: In this article, we reexamine the hypothesis of language retrogenesis, that is, the assumption that language change over healthy ageing mirrors, albeit inversely, language acquisition by the child. We additionally question whether this inverse pattern can as well be observed at the cognitive and neurobiological levels, and whether it can be informative (and a consequence, in fact) of how language evolved in humans. Method: We compare the language strengths and weaknesses signifying language acquisition and its eventual decay in healthy ageing. We further compare age-related cognitive and neurobiological readjustments during each of these two developmental stages, with a focus on brain areas involved in language processing. Finally, we delve into the evolutionary changes experienced by these areas. Results: We present evidence supporting the hypothesis of retrogenesis in two domains of language: the lexicon (lexical access, understanding of nonliteral meanings, and resolution of lexical competition) and syntax (understanding and production of complex sentences). Additionally, we show evidence that the brain areas supporting these complex tasks are late-myelinated in childhood and early-demyelinated during ageing. Finally, we show that some of these areas (such as the inferior frontal gyrus) are phylogenetically newer. Conclusions: Language acquisition in children and language degradation/loss in healthy ageing follow the principle of retrogenesis, but mostly in domains that are cognitively demanding and that depend on recently evolved brain devices. Putting this differently, the components of language that emerged more recently appear to be more, and earlier, affected during ageing, as well as developed later over childhood.

Lifespan Oscillatory Dynamics in Lexical Production: A Population-based MEG Resting-State Analysis

“…Using eight neuropsychological tests, we measured the LP performance, domain-general (DG), and language-specific processes (see Table 1). We also considered education levels as previous work suggested that this factor modulates semantic retrieval 22 . Education attainment was mapped to a 10-point scale ranging from CSE/GCSE diploma to PhD.…”

“…In this context, longer naming latencies and more frequent tip-of-the-tongue situations with age could be mitigated by enhanced semantic access thanks to a distributed anatomo-functional reorganization 12,[18][19][20] . Specifically, the enrichment of semantic repositories 2,21 could represent a strategy for maintaining the retrieval of words with stronger semantic connections 22 and conceptual categorization 23,24 contingent upon accumulated vocabulary knowledge throughout adulthood 25,26 . However, more pronounced inhibition deficits could challenge the ability to ignore task-irrelevant information [27][28][29] , leading to longer searches through a growing semantic store.…”

“…However, more pronounced inhibition deficits could challenge the ability to ignore task-irrelevant information [27][28][29] , leading to longer searches through a growing semantic store. Indeed, reduced access and retrieval of lexico-semantic representations 3,30 may induce more automatic and distracting thoughts, leading to a global decline in selecting the appropriate semantic information [31][32][33][34] , with difficulties beginning around midlife 4,22,35 .…”

Dynamics of White Matter Architecture in Lexical Production among Middle-Aged Adults

“…Indeed, this semantic expertise (Spreng & Turner, 2019) contributes to preserving language comprehension and implementing compensatory mechanisms to mitigate LP decline in older adults (Baciu et al, 2021). At the behavioral level, while advanced age is associated with the most significant LP decline (e.g., lower naming accuracy) (Shafto & Tyler, 2014; Verhaegen & Poncelet, 2013), increased naming latencies in low-frequency words with poorer semantic connections may onset in middle age (Benítez-Burraco & Ivanova, 2023). Therefore, a comprehensive investigation of midlife is crucial to understanding the aging mechanisms at play and predicting the neurocognitive trajectory in older late adulthood (Lachman, 2015; Park & Festini, 2016).…”

Language in healthy and pathological ageing: Methodological milestones and challenges

“…This means that language changes during ageing can serve as proxies for the cognitive strengths and weaknesses of the elderly as they age. Interestingly, the most complex aspects of language (like embedding, as usually found in dependent clauses) are impacted earlier by ageing, pretty much as they emerge later in the child, and they depend on brain circuits that are early‐demyelinated during ageing, pretty much as they are late‐myelinated during childhood (Benítez‐Burraco & Ivanova, 2023). This is seemingly due to their phylogenetic novelty, which results in less robust mechanisms of resistance to ontogenetic damage.…”