Functional MRI evidence for the decline of word retrieval and generation during normal aging

Abstract

This fMRI study aimed to explore the effect of normal aging on word retrieval and generation. The question addressed is whether lexical production decline is determined by a direct mechanism, which concerns the language operations or is rather indirectly induced by a decline of executive functions. Indeed, the main hypothesis was that normal aging does not induce loss of lexical knowledge, but there is only a general slowdown in retrieval mechanisms involved in lexical processing, due to possible decline of the executive functions. We used three tasks (verbal fluency, object naming, and semantic categorization). Two groups of participants were tested (Young, Y and Aged, A), without cognitive and psychiatric impairment and showing similar levels of vocabulary. Neuropsychological testing revealed that older participants had lower executive function scores, longer processing speeds, and tended to have lower verbal fluency scores. Additionally, older participants showed higher scores for verbal automatisms and overlearned information. In terms of behavioral data, older participants performed as accurate as younger adults, but they were significantly slower for the semantic categorization and were less fluent for verbal fluency task. Functional MRI analyses suggested that older adults did not simply activate fewer brain regions involved in word production, but they actually showed an atypical pattern of activation. Significant correlations between the BOLD (Blood Oxygen Level Dependent) signal of aging-related (A > Y) regions and cognitive scores suggested that this atypical pattern of the activation may reveal several compensatory mechanisms (a) to overcome the slowdown in retrieval, due to the decline of executive functions and processing speed and (b) to inhibit verbal automatic processes. The BOLD signal measured in some other aging-dependent regions did not correlate with the behavioral and neuropsychological scores, and the overactivation of these uncorrelated regions would simply reveal dedifferentiation that occurs with aging. Altogether, our results suggest that normal aging is associated with a more difficult access to lexico-semantic operations and representations by a slowdown in executive functions, without any conceptual loss.

Circulating IGF-1 deficiency exacerbates hypertension-induced microvascular rarefaction in the mouse hippocampus and retrosplenial cortex: implications for cerebromicrovascular and brain aging

“…Circulating IGF-1 levels and blood pressure measurements Although the factors responsible for the deleterious effects of aging on behavior and neuronal function (Baciu et al 2016;Berghuis et al 2015;Campbell et al 2014;Doi et al 2015;Haider et al 2014;Hofmann et al 2014;Kumar and Thakur 2015;Lopez et al 2014;Manich et al 2014;Salminen et al 2014;Samaras et al 2014;Sarubbo et al 2015;Loprinzi 2016;Wallis et al 2016) are not completely understood, there is strong evidence that in elderly humans a decline in circulating IGF-1 levels (Franco et al 2014) plays a critical pathophysiological role. To understand the effects of IGF-1 deficiency on the cerebral microcirculation in the present study, we used a novel mouse model of adult-onset isolated endocrine IGF-1 deficiency, which phenotypically better mimics age-related IGF-1 deficiency observed in humans that most other available rodent models of GH/IGF-1 deficiency (Arum et al 2014a;Hill et al 2015;Rojanathammanee et al 2014;Wiesenborn et al 2014;Arum et al 2014b;Schneider et al 2014).…”

Changes in Cortical Activation Patterns in Language Areas following an Aerobic Exercise Intervention in Older Adults

“…Much of this literature has been informed by studies involving transcranial magnetic stimulation (TMS), but there is also growing evidence that cortical inhibition can be assessed using fMRI [30, 37] and that fMRI may be sensitive to aging-related changes in inhibition [14, 30, 37]. Aging-related changes in inhibitory function during language production, particularly in BA 44/45, have been reported with increasing frequency [19, 38, 39]. Future research should endeavor to incorporate multiple neuroimaging/neurophysiological techniques to better identify the physiological origin of the effect of exercise on verbal fluency.…”

Targeting age‐related differences in brain and cognition with multimodal imaging and connectome topography profiling

“…Aging is a multifactorial process defined as a time-dependant functional decline that affects most living organisms (López-Otín, Blasco, Partridge, Serrano, & Kroemer, 2013). Though not fully understood, aging involves the accumulation of structural and metabolic changes that ultimately lead to impairments in multiple cognitive domains, including executive function, episodic memory, and word retrieval (Baciu et al, 2016;Fjell, Sneve, Grydeland, Storsve, & Walhovd, 2017;Tromp, Dufour, Lithfous, Pebayle, & Després, 2015). Collectively, these contribute to increasing challenges for psychosocial functioning, wellbeing, and quality of life in older age (Pan et al, 2015;Wilson et al, 2013).…”