title: The implications of state-dependent tDCS effects in aging: Behavioural response is determined by baseline performance.
abstract: Young adults typically display a processing advantage towards the left side of space ("pseudoneglect"), possibly as a result of right parietal dominance for spatial attention. This bias is ameliorated with age, with older adults displaying either no strongly lateralised bias, or a slight bias towards the right. This may represent an age-related reduction of right hemispheric dominance and/or increased left hemispheric involvement. Here, we applied anodal transcranial direct current stimulation (atDCS) to the right posterior parietal cortex (PPC; R-atDCS), the left PPC (L-atDCS) and a Sham protocol in young and older adults during a titrated lateralised visual detection task. We aimed to facilitate visual detection sensitivity in the contralateral visual field with both R-atDCS and L-atDCS relative to Sham. We found no differences in the effects of stimulation between young and older adults. Instead the effects of atDCS were state-dependent (i.e. related to task performance at baseline). Relative to Sham, poor task performers were impaired in both visual fields by anodal stimulation of the left posterior parietal cortex (PPC). Conversely, good performers maintained sensitivity in both visual fields in response to R-atDCS, although this effect was small. We highlight the importance of considering baseline task ability when designing tDCS experiments, particularly in older adults.
authors: Centre for Cognitive Neuroimaging, School of Psychology, University of Glasgow, Glasgow G12 8QB, UK; School of Psychology, University of Glasgow, Glasgow G12 8QB, UK. Electronic address: g.learmonth.1@research.gla.ac.uk.
authors: Gemma
authors: G
authors: Learmonth
authors: Centre for Cognitive Neuroimaging, School of Psychology, University of Glasgow, Glasgow G12 8QB, UK.
authors: Gregor
authors: G
authors: Thut
authors: Centre for Cognitive Neuroimaging, School of Psychology, University of Glasgow, Glasgow G12 8QB, UK; School of Psychology, University of Glasgow, Glasgow G12 8QB, UK.
authors: Christopher S Y
authors: CS
authors: Benwell
authors: School of Psychology, University of Glasgow, Glasgow G12 8QB, UK.
authors: Monika
authors: M
authors: Harvey
mesh_terms: D000293:Adolescent; D000368:Aged; D000375:Aging; D000704:Analysis of Variance; D001288:Attention / Q000502:physiology*; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D010296:Parietal Lobe / Q000502:physiology*; D010775:Photic Stimulation; D011597:Psychomotor Performance / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology; D013028:Space Perception / Q000502:physiology*; D065908:Transcranial Direct Current Stimulation / Q000379:methods*; D055815:Young Adult
keywords: Attention; Harold model; Non-invasive brain stimulation; Plasticity; Posterior parietal cortex; Pseudoneglect