Abstract
Functional brain imaging studies and non-invasive brain stimulation methods have shown the importance of the left supramarginal gyrus (SMG) for pitch memory. The extent to which this brain region plays a crucial role in memory for other auditory material remains unclear. Here, we sought to investigate the role of the left and right SMG in pitch and rhythm memory in non-musicians. Anodal or sham transcranial direct current stimulation (tDCS) was applied over the left SMG (Experiment 1) and right SMG (Experiment 2) in two different sessions. In each session participants completed a pitch and rhythm recognition memory task immediately after tDCS. A significant facilitation of pitch memory was revealed when anodal stimulation was applied over the left SMG. No significant effects on pitch memory were found for anodal tDCS over the right SMG or sham condition. For rhythm memory the opposite pattern was found; anodal tDCS over the right SMG led to an improvement in performance, but anodal tDCS over the left SMG had no significant effect. These results highlight a different hemispheric involvement of the SMG in auditory memory processing depending on auditory material that is encoded.
Highlights
Together, these studies indicate that pitch and rhythm processing can be dissociated, and neural processes related to encoding pitch and rhythm may rely on distinct neural circuits
The participants performed significantly better on the pitch memory span task after receiving anodal transcranial direct current stimulation (tDCS) over the left supramarginal gyrus (SMG) compared to sham stimulation
Experiment 1 revealed that anodal tDCS over the left SMG significantly facilitated pitch memory, whereas rhythm memory was not affected
Summary
Together, these studies indicate that pitch and rhythm processing can be dissociated, and neural processes related to encoding pitch and rhythm may rely on distinct neural circuits. With regards to the neural network for pitch and rhythm memory, brain imaging alone cannot tell us about causal relationships between brain areas and behaviour. For this alternative methods that permit the investigation of modulations in brain activity are more powerful (e.g. lesions[20,21,22]; brain stimulation[23,24,25,26,27,28]). The aim of this study was to examine the role of the left and right SMG for rhythm and pitch memory. An effect of anodal tDCS on memory performance was hypothesised as brain imaging studies show the involvement of the SMG for rhythm memory[12,13,43], but the lateralisation of the effect is less predictable
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