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Dopamine improves impaired multisensory perception in Parkinson's disease
Parkinson's disease (PD) is a neurodegenerative disease primarily associated with movement deficits. Although far less studied, PD patients also suffer from sensory and cognitive deficits. In this study, we investigate potential deficits of PD in multisensory perception.
To test multisensory perception, we applied a visuo-tactile illusion. If a brief visual stimulus (˜16 ms), accompanied by two electrical pulses (˜0.3 ms), is presented with a short stimulus onset asynchrony (SOA) of ˜50 – 100 ms, this paradigm is known to induce the perception of a second, illusory visual stimulus in healthy subjects (double-flash illusion (DFI), Lange et al. 2013). Here, we hypothesized that the critical SOA to perceive the DFI was prolonged in PD. 11 PD patients suffering from the akinetic-rigid subtype were tested twice with the DFI: after withdrawal of medication for > 12h (OFF) and after administration of dopaminergic medication (ON).
In line with our hypothesis, 5 patients (OFF) showed prolonged SOAs (> 200 ms) to perceive the DFI (SEE). Notably, 6 patients were unable to perceive the DFI at any SOA. For the SEE group, critical SOAs shifted to 70 – 170 ms in the ON state, i.e. patients perceived more DFI for short SOA and less for long SOA compared to OFF.
In summary, we reveal altered multisensory perception in PD patients. Dopaminergic medication reduces the alteration and shifts multisensory perception towards healthy subjects. The results demonstrate a critical role of dopamine for PD beyond known motor symptoms and add to the understanding of mechanisms underlying PD and multisensory perception.
Lange, Oostenveld, Fries (2013) Reduced occipital alpha power indexes enhanced excitability rather than improved visual perception. J Neurosci. 13;33(7):3212 – 20.