The impact of tDCS on memory and its link to neurotransmitters
On the neurophysiological level, learning and memory rely on synaptic plasticity processes, particularly on an interplay of long-term potentiation (LTP) and long-term depression (LTD). These processes are further mediated by glutamate and GABA, the main excitatory and inhibitory neurotransmitters respectively. Similar mechanisms of action were proposed to underlie the beneficial long-term effects of tDCS in different learning paradigms. Since the induced neurophysiological and behavioural changes are not only collaterally occurring but causally linked, the three-way combination of tDCS, magnetic resonance spectroscopy (MRS), and cognitive measures offers relevant insights into the underlying principles of tDCS that ultimately determine the clinically sought-after cognitive benefits. In sight of the observed large inter-individual heterogeneity in stimulation benefits, neurophysiological measures could also be deployed as biomarkers for stimulation outcomes. So far, these connections have mainly been demonstrated in the motor cortex but whether the findings are transferable to frontal brain regions remains to be shown. In our study, healthy young participants performed a verbal memory task while receiving concurrent tDCS. Furthermore, we assessed glutamatergic metabolites and GABA prior to and after the stimulation. Since we could not replicate the previous findings in the motor cortex, regarding the hypothesized neurotransmitter changes, contributing factors will be discussed in the presentation.