Same Modulation but Different Starting Points: Performance Modulates Age Differences in Inferior Frontal Cortex Activity during Word-Retrieval

Abstract

The neural basis of word-retrieval deficits in normal aging has rarely been assessed and the few previous functional imaging studies found enhanced activity in right prefrontal areas in healthy older compared to younger adults. However, more pronounced right prefrontal recruitment has primarily been observed during challenging task conditions. Moreover, increased task difficulty may result in enhanced activity in the ventral inferior frontal gyrus (vIFG) bilaterally in younger participants as well. Thus, the question arises whether increased activity in older participants represents an age-related phenomenon or reflects task difficulty effects. In the present study, we manipulated task difficulty during overt semantic and phonemic word-generation and used functional magnetic resonance imaging to assess activity patterns in the vIFG in healthy younger and older adults (N = 16/group; mean age: 24 vs. 69 years). Both groups produced fewer correct responses during the more difficult task conditions. Overall, older participants produced fewer correct responses and showed more pronounced task-related activity in the right vIFG. However, increased activity during the more difficult conditions was found in both groups. Absolute degree of activity was correlated with performance across groups, tasks and difficulty levels. Activity modulation (difficult vs. easy conditions) was correlated with the respective drop in performance across groups and tasks. In conclusion, vIFG activity levels and modulation of activity were mediated by performance accuracy in a similar way in both groups. Group differences in the right vIFG activity were explained by performance accuracy which needs to be considered in future functional imaging studies of healthy and pathological aging.

Differences in EEG power in young and mature healthy adults during an incidental/spatial learning task are related to age and execution efficiency

“…Greater activation in young adults relative to older adults was reported in structures such as the frontal superior and inferior bilateral gyrus, right superior temporal gyrus and left supramarginal gyrus in an fMRI study when the participants judged the familiarity of melodies, although no differences were observed in the ability of the groups (Sikka, Cuddy, Johnsrude and Vanstone 2015). Moreover, age-related alterations in the activation of these structures have been reported in fMRI studies in normal ageing or in mild cognitive impairment (Meinzer et al 2012;Zhao et al 2014). Reduced theta activity during automatic encoding of face-place associations reinforced with semantic relatedness was also observed in the left frontal inferior gyrus in association with poor performance in adults aged 59-72 years (Crespo-Garcia, Cantero and Atienza 2012).…”

Grey Matter Correlates of Three Language Tests in Non-demented Older Adults

“…Evidence also suggests that higher degree of leftward asymmetry in language-related regions is correlated with better language function [34-36]. In older adults, however, the neural basis of language displays a more symmetric pattern, located in the bilateral frontal and temporal lobes [37-39]. Based on substantial evidence provided by fMRI studies, a theory was proposed (the HAROLD model) [40], suggesting that the reduction of hemispheric asymmetry in older adults may reflect the plasticity of the ageing brain to engage extra neural circuits to compensate age-related neural inefficiency [40-42].…”

Communication Difficulty and Relevant Interventions in Mild Cognitive Impairment

“…Similarly, Meinzer and colleagues also observed increased activation of inferior frontal cortex across different difficulty levels of verbal fluency tasks in an older group, as compared to a younger group. 70 …”