The left dorsal stream causally mediates the tone labeling in absolute pitch

Abstract

BackgroundAbsolute pitch (AP) refers to the ability of effortlessly identifying given pitches without the reliance on any reference pitch. Correlative evidence suggests that the left posterior dorsolateral prefrontal cortex (DLPFC) is responsible for the process underlying pitch labeling in AP. ObjectiveHere, we aimed at investigating the causal relationship between the DLPFC and the pitch-labeling process underlying AP. MethodsTo address this, we measured sight-reading performance of right-handed AP possessors and matched control musicians (N =18 per sample) under cathodal and sham transcranial direct current stimulation of the left DLPFC. The participants were instructed to report visually presenting notations as accurately and fast as possible by playing with their right hand on a piano. The notations were simultaneously presented with distracting auditory stimuli that either matched or mismatched them in different semitone degrees. ResultsUnlike the control participants, the AP possessors revealed an interference effect in that they responded slower in mismatching conditions than in the matching one. Under cathodal stimulation, half of the time discrepancies between matching and mismatching conditions vanished; specifically, the ones with small up to moderate deviations. ConclusionsThese findings confirm that the pitch-labeling process underlying AP occurs automatically and is largely non-suppressible when triggered by tone exposure. The improvement of the AP possessors sight-reading performance in response to the suppression of the left DLPFC using cathodal stimulation confirms a causal relationship between this brain structure and pitch labeling.