Improved conceptual generation and selection with transcranial direct current stimulation in older adults

ABSTRACT

Introduction: Normal aging is associated with deficits in various aspects of spoken language production, including idea generation and selection, and involves activity in frontal brain areas including left inferior frontal cortex (LIFG). These conceptual preparation processes, largely involving executive control, precede formulation and articulation stages and are critical for language production. Noninvasive brain stimulation (e.g., transcranial direct current stimulation, tDCS) has proven beneficial for age-related fluency and naming deficits, but this has not been extended to conceptual preparation mechanisms. Method: We investigated whether tDCS could facilitate idea generation and selection in 24 older adults aged 60–80 years. In the first phase, participants completed an idea generation test and a selection test with no stimulation. In the second phase they completed an alternate version of the tests in conjunction with either active or sham stimulation. Active stimulation applied 1-mA anodal tDCS over LIFG for the test duration (10 min). Results:  Responses were faster following active stimulation than following sham. Furthermore, improvements were specific to test conditions involving novel generation (p = .030) and selection (p = .001) and were not observed in control conditions for which these mechanisms were minimally involved. Conclusions:  We concluded that tDCS benefits conceptual preparation mechanisms. This preliminary evidence is an important step for addressing age-related decline in propositional language generation, which is integral to conversational speech. This approach could also be extended toward rehabilitation in neurological patients with deficits in these processes.

KEYWORDS:

• Normal aging
• conceptual preparation
• idea generation
• selection
• transcranial direct current stimulation

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the National Health and Medical Research Council (NHMRC) Postdoctoral Training Fellowship [grant number APP1012153] awarded to M.S.; and an Australian Postgraduate Award scholarship awarded to D.M. by the University of Queensland, on behalf of the Queensland Government Department of Education. For the duration of this study G.R. was the recipient of an Australian Research Council Discovery Early Career Researcher Award [grant number DE120101119], and is now funded by the Australian National Health and Medical Research Council [NHMRC Boosting Dementia Research Leadership Fellowship number APP1135769], [Dementia Research Team grant number APP1095227].