title: Transcranial random noise stimulation mitigates increased difficulty in an arithmetic learning task.
abstract: Proficiency in arithmetic learning can be achieved by using a multitude of strategies, the most salient of which are procedural learning (applying a certain set of computations) and rote learning (direct retrieval from long-term memory). Here we investigated the effect of transcranial random noise stimulation (tRNS), a non-invasive brain stimulation method previously shown to enhance cognitive training, on both types of learning in a 5-day sham-controlled training study, under two conditions of task difficulty, defined in terms of item repetition. On the basis of previous research implicating the prefrontal and posterior parietal cortex in early and late stages of arithmetic learning, respectively, sham-controlled tRNS was applied to bilateral prefrontal cortex for the first 3 days and to the posterior parietal cortex for the last 2 days of a 5-day training phase. The training involved learning to solve arithmetic problems by applying a calculation algorithm; both trained and untrained problems were used in a brief testing phase at the end of the training phase. Task difficulty was manipulated between subjects by using either a large ("easy" condition) or a small ("difficult" condition) number of repetition of problems during training. Measures of attention and working memory were acquired before and after the training phase. As compared to sham, participants in the tRNS condition displayed faster reaction times and increased learning rate during the training phase; as well as faster reaction times for both trained and untrained (new) problems, which indicated a transfer effect after the end of training. All stimulation effects reached significance only in the "difficult" condition when number of repetition was lower. There were no transfer effects of tRNS on attention or working memory. The results support the view that tRNS can produce specific facilitative effects on numerical cognition--specifically, on arithmetic learning. They also highlight the importance of task difficulty in the neuromodulation of learning, which in the current study due to the manipulation of item repetition might have being mediated by the memory system.
authors.affiliation: Department of Experimental Psychology, University of Oxford, South Parks Road, Oxford OX1 3UD, UK. Electronic address: tudor.popescu@tu-dresden.de.
authors.forename: Tudor
authors.initials: T
authors.lastname: Popescu
authors.affiliation: Department of Experimental Psychology, University of Oxford, South Parks Road, Oxford OX1 3UD, UK.
authors.forename: Beatrix
authors.initials: B
authors.lastname: Krause
authors.affiliation: Department of Experimental Psychology, University of Oxford, South Parks Road, Oxford OX1 3UD, UK.
authors.forename: Devin B
authors.initials: DB
authors.lastname: Terhune
authors.affiliation: Department of Experimental Psychology, University of Oxford, South Parks Road, Oxford OX1 3UD, UK.
authors.forename: Olivia
authors.initials: O
authors.lastname: Twose
authors.affiliation: Department of Experimental Psychology, University of Oxford, South Parks Road, Oxford OX1 3UD, UK.
authors.forename: Thomas
authors.initials: T
authors.lastname: Page
authors.affiliation: Department of Experimental Psychology, University of Oxford, South Parks Road, Oxford OX1 3UD, UK.
authors.forename: Glyn
authors.initials: G
authors.lastname: Humphreys
authors.affiliation: Department of Experimental Psychology, University of Oxford, South Parks Road, Oxford OX1 3UD, UK.
authors.forename: Roi
authors.initials: R
authors.lastname: Cohen Kadosh
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001288:Attention / Q000502:physiology*; D056344:Executive Function / Q000502:physiology*; D005260:Female; D006801:Humans; D007858:Learning / Q000502:physiology*; D008297:Male; D055641:Mathematical Concepts; D008433:Mathematics; D009949:Orientation / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology; D065908:Transcranial Direct Current Stimulation; D055815:Young Adult
keywords: Cognitive training; Mental arithmetic; Posterior parietal cortex; Prefrontal cortex; Task difficulty; Transcranial random noise stimulation