Abstract:
Animal models of long-term potentiation are one of the most studied mechanisms of learning, however these invasive methods are not practised in humans. A novel paradigm known as ‘visual LTP’ has been suggested as a human analogue for synaptic plasticity assessment. This non-invasive method involves passive viewing of stimuli, while EEG is recorded at different time points to determine event-related potential (ERP) change. A high-frequency stimulation (8.6 Hz) protocol mimics neuronal tetanus, which brings about a stimulus specific change in the N1b component. The N1b modulation post HFS has been replicated many times, however the perceptual consequences of LTP-like change, which are intended to underlie learning, have not been as thoroughly investigated. A Bayesian adaptive psychophysics task was used to assess contrast sensitivity for the stimulated (HFS) and non-stimulated stimulus. The LTP-like N1b modulation was effectively induced for a specific stimulus, however there was also a transfer effect to the non-stimulated stimulus. The subsequent behavioural task revealed an increase in psychometric threshold for the stimulated stimulus compared to the non-stimulated. Thus the stimulus specific HFS appeared to reduce contrast sensitivity for said stimulus. Potential reasons for this result will be discussed. Keywords: Adaptive Psychophysics, Electrophysiology, Neuroplasticity, Perceptual Learning