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Age-related sensitivity to task-related modulation of language-processing networks.

ABSTRACT: It is widely assumed that cognitive functions decline with age and that these decrements are associated with age-related changes in patterns of functional activity. However, these functional changes may be due to age-related increased responsiveness to task demands and not to other cognitive processes on which neural and behavioural responses rely, since many ageing studies use task paradigms that may not be orthogonal to the cognitive function being investigated. Here we test this hypothesis in adults aged 20-86 years by combining measures of language comprehension, functional connectivity and neural integrity to identify functional networks activated in two language experiments with varying task demands. In one, participants listened to spoken sentences without performing an overt task (the natural listening condition) while in the other they performed a task in response to the same sentences. Using task-based ICA of fMRI, we identified a left-lateralised frontotemporal network associated with syntactic analysis, which remained consistently activated regardless of task demands. In contrast, in the task condition only a separate set of components showed task-specific activity in Opercular, Frontoparietal, and bilateral PFC. Only the PFC showed age-related increases in activation which, furthermore, was strongly mediated by grey matter health. These results suggest that, contrary to prevailing views, age-related changes in cognitive activation may be due in part to differential responses to task-related processes.

SUBMITTER: Davis SW

PROVIDER: S-EPMC4410794 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:ObjectiveIntraoperative tasks for awake language mapping are typically selected based on the language tracts that will likely be encountered during tumor resection. However, diminished attention and arousal secondary to perioperative sedatives may reduce a task's usefulness for identifying eloquent cortex. For instance, accuracy in performing select language tasks may be high preoperatively but decline in the operating room. In the present study, the authors sought to identify language tasks that can be performed with high accuracy in both situational contexts so the neurosurgical team can be confident that speech errors committed during awake language mapping result from direct cortical stimulation to eloquent cortex, rather than from poor performance in general.MethodsWe administered five language tasks to 44 patients: picture naming (PN), text reading (TR), auditory object naming (AN), repetition of 4-syllable words (4SYL), and production of syntactically intact sentences (SYNTAX). Performance was assessed using the 4-point scale of the quick aphasia battery 24 hours preoperatively and intraoperatively. We next determined whether or not accuracy on each task was higher preoperatively than intraoperatively. We also determined whether 1) intraoperative accuracy on a given task predicted intraoperative performance on the other tasks and 2) low preoperative accuracy on a task predicted a decrease in accuracy intraoperatively.ResultsRelative to preoperative accuracy, intraoperative accuracy declined on PN (3.90 vs 3.82, p = 0.0001), 4SYL (3.96 vs 3.91, p = 0.0006), and SYNTAX (3.85 vs 3.67, p = 0.0001) but not on TR (3.96 vs 3.94, p = 0.13) or AN (3.70 vs 3.58, p = 0.058). Intraoperative accuracy on PN and AN independently predicted intraoperative accuracy on the remaining language tasks (p < 0.001 and p < 0.01, respectively). Finally, low preoperative accuracy on SYNTAX predicted a decrease in accuracy on this task intraoperatively (R2 = 0.36, p = 0.00002).ConclusionsWhile TR lacks sensitivity in identifying language deficits at baseline, accuracy on TR is stable across testing settings. Baseline accuracy on the other four of our five language tasks was not predictive of intraoperative performance, signifying the need to repeat language tests prior to stimulation mapping to confirm reliability.

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Age-related sensitivity to task-related modulation of language-processing networks.

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