Impact of changed positive and negative task-related brain activity on word-retrieval in aging

Abstract

Previous functional imaging studies that compared activity patterns in older and younger adults during non-linguistic tasks found evidence for two phenomena: older participants usually show more pronounced task-related positive activity in the brain hemisphere that is not dominant for the task and less pronounced negative task-related activity in temporo-parietal and midline brain regions. The combined effects of these phenomena and the impact on word-retrieval, however, have not yet been assessed. We used functional magnetic resonance imaging to explore task-related positive (active task > baseline) and negative activity (baseline > active task) during semantic and phonemic verbal fluency tasks. Increased right-frontal positive activity during the semantic task and reduced negative activity in the right hemisphere during both tasks was associated with reduced performance in older subjects. No substantial relationship between changes in positive and negative activity was observed in the older participants, pointing towards two partially independent but potentially co-occurring processes. Underlying causes of the observed functional network inefficiency during word-retrieval in older adults need to be determined in the future.

Electrical Brain Stimulation Improves Cognitive Performance by Modulating Functional Connectivity and Task-Specific Activation

“…As in previous studies that used similar word generation designs (Meinzer et al, 2009(Meinzer et al, , 2012) a whole-brain comparison of correct semantic word generation trials with the baseline condition (saying the word "rest" aloud) elicited a reliable and highly consistent pattern of task-related activity for both conditions. Most pronounced activity was found in the lateral (ventral and dorsal) IFG and medial frontal areas, but also left posterior temporal and parietal areas and the right inferior frontal gyrus [ Fig.…”

“…In the language domain, increasing proficiency in a newly learned second language is associated with more focal left-lateralized activity in prefrontal cortices, resembling the network active during language processing in the mother tongue (Abutalebi, 2008). Furthermore, increased bilateral IFG activity is associated with reduced semantic word-generation performance in healthy aging (Meinzer et al, 2009(Meinzer et al, , 2012, and even in young adults when task demands are increased (Thompson-Schill et al, 1997). Other studies found increased activity after tDCS.…”

“…The task has been described previously in detail (Meinzer et al, 2009(Meinzer et al, , 2012. In short, each category was visually presented in blocks of 10 consecutive trials.…”

“…Incorrect and excluded trials of both scanning sessions were included as additional regressors in the statistical model. The number of trials in the respective analyses of individual subjects ranged from 44 to 54 trials (please note that previous studies using the same design only used 40 trials (Meinzer et al, 2009(Meinzer et al, , 2012, thus, it was ensured that a sufficient number of trials could be analyzed for all subjects). Planned contrasts of interest were estimated for each subject and session (semantic word generation vs baseline trials).…”

Neurophysiological Markers of Language Recovery in Subacute Stroke

“…Age-related neural differences for semantic versus phonemic fluency were also identified in a study by Meinzer et al (2012). The findings showed increased right IFG by the older adults accompanied by a reduction in behavioural performance in semantic fluency, suggesting that semantic and phonological processing may differ as a function of age.…”