Abstract Details

Title Sampling Frequency of Visual Perception in Parkinson’s Disease is Slower Than Normal Aging

Topic Aging, Dementia, and Behavioral Neurology

Presentation(s) Behavioral and Cognitive Neurology Posters (7:00 AM-5:00 PM)

Poster/Presentation
Number 015

Objective To compared visual sampling frequency between Parkinson’s disease (PD) patients and normal healthy age-matched controls.

Background Visual disturbance, such as visual hallucination, is one of the most disturbing non-motor symptoms in PD. However, the mechanism is still unclear. Since PD have bradykinesia and rigidity as the motor symptoms, we entertained the possibility that visual perception might suffered from similar problem or what we will call “the bradykinesia of the visual system”. The previous vision studies have shown that we can measure the “speed” or the sampling frequency of the visual perception by using behavioral paradigm and the peak frequency of posterior dominant rhythm (PDR) from electroencephalography (EEG).

Design/Methods

60 PD patients (diagnosed by movement specialists base on MDS-PD criteria) and 30 age-matched controls were recruited. N-flashes discrimination task was used to measure shortest time interval between two flashes (interstimulus interval, ISI) that the participants can reliably discriminate between single versus double flash/es. The shorter ISI infers faster sampling frequency. The peak of PDR (in Hz) on eye closed was also measured at rest. The ISI, reaction time, and peak of PDR in PD and controls were compared.

Results

ISI in PD patients tended to be longer than controls (mean= 21.4 ms, SE=3.1 versus mean=13.6, SE=1.4 respectively, p=0.05). The reaction time in PD patients was significantly slower than controls (mean=503.3 ms, SE=106.4 versus mean=173.0 ms, SE=16.6 respectively, P<0.05). Peak of PDR in PD patients made less than controls (mean= 8.51, SE=0.16 versus mean = 9.76, SE=0.18 respectively, p< 0.001). Lastly, there were a significant negative correlation between ISI and peak of PDR (Pearson’s r = -0.47, p<0.001)

Conclusions We found evidence supported our hypothesis that PD patients had slower visual sampling frequency which can be behaviorally and neurophysiologically measured. This slower visual sampling frequency that might lead to poorer visual perception which underlie visual hallucination.

Authors/Disclosures
Natchawan Tantithanarat, MD (King Chulalongkorn Memorial Hospital) PRESENTER	Ms. Tantithanarat has nothing to disclose.
	No disclosure on file
Roongroj Bhidayasiri, MD, FRCP, FRCPI (Chulalongkorn Center of Excellence for Parkinson'S Disease & Related Disorders)	No disclosure on file

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