Differences between Patterns of Brain Activity Associated with Semantics and Those Linked with Phonological Processing Diminish with Age (2025)

Neural Signatures of Semantic and Phonemic Fluency in Young and Old Adults

Journal of Cognitive Neuroscience, 2009

As we age, our ability to select and produce words changes, yet we know little about the underlying neural substrate of word-finding difficulties in old adults. The present study was designed to elucidate changes in specific frontally mediated retrieval processes involved in word-finding difficulties associated with advanced age. We implemented two overt verbal (semantic and phonemic) fluency tasks during functional magnetic resonance imaging and compared brain activity patterns of old and young adults. Performance during the phonemic task was comparable for both age-groups and mirrored by strongly left lateralized (frontal) activity patterns. On the other hand, a significant drop of performance during the semantic task in the older goup was accompanied by additional right (inferior and middle) frontal activity, which was negatively correlated with performance. Moreover, the younger group recruited different subportions of the left inferior frontal gyrus for both fluency tasks, while the older participants failed to show this distinction. Thus, functional integrity and efficient recruitment of left frontal language areas seems to be critical for successful word-retrieval in old age.

The Effect of Aging on the Neural Correlates of Phonological Word Retrieval

Journal of Cognitive Neuroscience, 2012

Age has a differential effect on cognition, with word retrieval being one of the cognitive domains most affected by aging. This study examined the functional and structural neural correlates of phonological word retrieval in younger and older adults using word and picture rhyme judgment tasks. Although the behavioral performance in the fMRI task was similar for the two age groups, the older adults had increased activation in the right pars triangularis across tasks and in the right pars orbitalis for the word task only. Increased activation together with preserved performance in the older participants would suggest that increased activation was related to compensatory processing. We validated this hypothesis by showing that right pars triangularis activation during correct rhyme judgments was highest in participants who made overall more errors, therefore being most error-prone. Our findings demonstrate that the effect of aging differ in adjacent but distinct right inferior frontal ...

Age-related changes in word retrieval: Role of bilateral frontal and subcortical networks

Neurobiology of Aging, 2008

The Neural Language Systems That Support Healthy Aging: Integrating Function, Structure, and Behavior

Language and Linguistics Compass, 2016

Although healthy aging is generally characterized by declines in both brain structure and function, there is variability in the extent to which these changes result in observable cognitive decline. Specific to language, age-related differences in language production are observed more frequently than in language comprehension, although both are associated with increased right prefrontal cortex activation in older adults. The current paper explores these differences in the language system, integrating them with theories of behavioral and neural cognitive aging. Overall, data indicate that frontal reorganization of the dorsal language stream in older adults benefits task performance during comprehension, but not always during production. We interpret these results in the CRUNCH framework (compensation-related utilization of neural circuits hypothesis), which suggests that differences in task and process difficulty may underlie older adults' ability to successfully adapt. That is, older adults may be able to neurally adapt to less difficult tasks (i.e., comprehension), but fail to do so successfully as difficulty increases (i.e., production). We hypothesize greater age-related differences in aspects of language that rely more heavily on the dorsal language stream (e.g., syntax and production) and that recruit general cognitive resources that rely on frontal regions (e.g., executive function, working memory, inhibition). Moreover, there should be a relative sparing of tasks that rely predominantly on ventral stream regions. These results are both consistent with patterns of age-related structural decline and retention and with varying levels of difficulty across comprehension and production. This neurocognitive framework for understanding age-related differences in the language system centers on the interaction between prefrontal cortex activation, structural integrity, and task difficulty.

Age-related Neural Reorganization during Spoken Word Recognition: The Interaction of Form and Meaning

Journal of Cognitive Neuroscience, 2012

Research on language and aging typically shows that language comprehension is preserved across the life span. Recent neuroimaging results suggest that this good performance is underpinned by age-related neural reorganization [e.g., Tyler, L. K., Shafto, M. A., Randall, B., Wright, P., Marslen-Wilson, W. D., & Stamatakis, E. A. Preserving syntactic processing across the adult life span: The modulation of the frontotemporal language system in the context of age-related atrophy. Cerebral Cortex, 20, 352-364, 2010]. The current study examines how age-related reorganization affects the balance between component linguistic processes by manipulating semantic and phonological factors during spoken word recognition in younger and older adults. Participants in an fMRI study performed an auditory lexical decision task where words varied in their phonological and semantic properties as measured by degree of phonological competition and imageability. Older adults had a preserved lexicality effect, but compared with younger people, their behavioral sensitivity to phonological competition was reduced, as was competition-related activity in left inferior frontal gyrus. This was accompanied by increases in behavioral sensitivity to imageability and imageability-related activity in left middle temporal gyrus. These results support previous findings that neural compensation underpins preserved comprehension in aging and demonstrate that neural reorganization can affect the balance between semantic and phonological processing.

Aging Modulates the Hemispheric Specialization during Word Production

Frontiers in Aging Neuroscience, 2017

Although older adults exhibit normal accuracy in performing word retrieval and generation (lexical production; e.g., object naming), they are generally slower in responding than younger adults. To maintain accuracy, older adults recruit compensatory mechanisms and strategies. We focused on two such possible compensatory mechanisms, one semantic and one executive. These mechanisms are reflected at inter-and intra-hemispheric levels by various patterns of reorganization of lexical production cerebral networks. Hemispheric reorganization (HR) changes were also evaluated in relation to increase naming latencies. Using functional magnetic resonance imaging (fMRI), we examined 27 healthy participants (from 30 years to 85 years) during an object naming task, exploring and identifying task-related patterns of cerebral reorganization. We report two main results. First, we observed a left intrahemispheric pattern of reorganization, the left anterior-posterior aging (LAPA) effect, consisting of supplementary activation of left posterior (temporo-parietal) regions in older adults and asymmetric activation along the left fronto-temporal axis. This pattern suggests that older adults recruit posterior semantic regions to perform object naming. The second finding consisted of bilateral recruitment of frontal regions to maintain appropriate response times, especially in older adults who were faster performers. This pattern is discussed in terms of compensatory mechanism. We suggest that aging is associated with multiple, co-existing compensation and reorganization mechanisms and patterns associated with lexical production.

Neural evidence for phonologically based language production deficits in older adults: An fMRI investigation of age-related differences in picture-word interference

Brain and Behavior, 2017

Introduction: Older adults often show declines in phonological aspects of language production, particularly for low-frequency words, but maintain strong semantic systems. However, there are different theories about the mechanism that may underlie such age-related differences in language (e.g., age-related declines in transmission of activation or inhibition). Methods: This study used fMRI to investigate whether age-related differences in language production are associated with transmission deficits or inhibition deficits. We used the picture-word interference paradigm to examine age-related differences in picture naming as a function of both target frequency and the relationship between the target picture and distractor word. Results: We found that the presence of a categorically related distractor led to greater semantic elaboration by older adults compared to younger adults, as evidenced by older adults' increased recruitment of regions including the left middle frontal gyrus and bilateral precuneus. When presented with a phonologically related distractor, patterns of neural activation are consistent with previously observed age deficits in phonological processing, including age-related reductions in the recruitment of regions such as the left middle temporal gyrus and right supramarginal gyrus. Lastly, older, but not younger, adults show increased brain activation of the pre-and postcentral gyri as a function of decreasing target frequency when target pictures are paired with a phonological distractor, suggesting that cuing the phonology of the target disproportionately aids production of low-frequency items. Conclusions: Overall, this pattern of results is generally consistent with the transmission deficit hypothesis, illustrating that links within the phonological system, but not the semantic system, are weakened with age.

Educational level and task performance influence on lexical access lateralization changes in healthy aging

Revista M�dica del Hospital General de M�xico

Hemispheric asymmetry reduction in older adults (HAROLD) model has claimed that older adults tend to display less lateralized brain activation patterns with respect to younger ones during memory, language, and naming tasks, but only a few times have these patterns been explored within older population. Furthermore, it is unclear if this phenomenon is a compensation response or an adaptive pattern that is not helping cognitive functions. Literature has assumed that education level (EL) could be critical, to explain such patterns. We aimed to control this as a variable by comparing neural correlates with an functional magnetic resonance imaging picture naming task in literate, healthy older adults with high and low EL. Our results showed that EL is not a determinant factor for activation of neural pattern reorganization prognosis. It was found that performance is a more reliable variable to observe neural pattern reorganization in the elderly. This study supports the de-differentiation hypothesis of HAROLD model because there is no reduction in lateralization of some highly-specialized structures in persons who maintained optimal lexical access, in contrast to those who had low scores in naming task.

Language in normal aging: Linguistic and neuropsychological factors

Journal of Neurolinguistics, 1989

We have hypothesized that non-linguistic cognitive factors (memory, attention, etc.) contribute to the language changes of normal aging. In this paper, after reviewing the changing patterns of language use associated with normal aging, we address the question of whether and how non-lin~istic factors contribute to these patterns. We focus on the processes of naming. One hundred and fifty-two men and women, ages 30-79, were administe~d three naming tests: the Boston Naming Test, the Action Naming Test, and the Category Naming Test. In addition, each subject was tested on several neuropsychoiogical tests that provided measures of short and long-term memory, attention, visual-perceptual processes, metaiinguistic skills, perseveration, and semantic memory. On the basis of performance on the neuropsychologicai tests, we developed a model of neuropsychoiogicai measures that may influence naming performance. Multiple regression analyses revealed that although our measures did contribute significantly to naming performance across age groups, a different pattern emerged within each age group, Our results indicate that involvement of non-linguistic cognitive processes innaming may actually decrease with age. These findings suggest that the mild anomia of normal aging is primarily linguistic. and is not significantfy influenced by memory, attentional, perceptual, or metalinguistic factors.

Contribution of NIRS to the study of prefrontal cortex for verbal fluency in aging

Brain and Language, 2012

Healthy aging is characterized by a number of changes on brain structure and function. Several neuroimaging studies have shown an age-related reduction in hemispheric asymmetry on various cognitive tasks, a phenomenon captured by Cabeza (2002) in the Hemispheric Asymmetry Reduction in Older Adults (HAROLD) model. Although this phenomenon is supported by a range of neuroimaging data on memory and inhibitory processes, there is little evidence concerning changes in hemispheric asymmetry for language processing, and particularly word retrieval, which is assessed with verbal fluency task (VFT). This study aimed to investigate the age-related changes in cerebral oxygenation in the prefrontal cortex for both letter and category VFT, varying the complexity of the criteria (i.e., degree of productivity) and using near-infrared spectroscopy (NIRS). Sixteen younger and 16 older adults participated in this study. For both VF conditions, participants were instructed to pronounce as many nouns as possible as a function of high-productivity (e.g., ''animals'' or ''L'') or low-productivity (e.g., ''flowers'' or ''V'') criteria. Behavioral data (i.e., accuracy responses) showed comparable performance in younger and older adults for both VF conditions. However, NIRS data showed more reduced activation (i.e., significantly reduced increase in [O 2 Hb] and reduced decrease in [HHb]) in older than younger adults for both VFT. In addition, a bilateral effect was found for both groups, suggesting that VFT requires both executive and language functions. The results are discussed in the context of the current theories of aging.