Psycho-sensory modalities of visual hallucinations and illusions in Parkinson's disease.

BACKGROUND: Visual illusions (VI) in Parkinson's disease (PD) are generally considered part of the prodrome towards fully formed visual hallucinations (VH), and classified as minor hallucinations. However, this sequential relationship has not been clearly demonstrated and very little is known about the specific phenomenology of VI in regards to VH. We aimed to describe and compare psycho-sensory modalities associated with VI and VH in PD patients. METHODS: PD patients with VI (PD-I, n=26) and VH (PD-H, n=28) were included in this case-controlled study. We compared qualitative and quantitative psycho-sensory modalities of VI and VH using the PsychoSensory hAllucinations Scale (PSAS), and demographical and clinical features of each group. RESULTS: PD-I perceptions were more often colored blots (P=0.05) or objects (P=0.005) compared to PD-H. Conversely, PD-H perceptions were more often described as animals (P<0.001), occurring at night (P=0.03) compared to PD-I. The experienced phenomena were more frequent in PD-H (P=0.02), and lasted longer (P=0.02) than for PD-I, but no between-group difference was observed for other repercussion factors including negative aspect, conviction, impact, controllable nature of the perception. Passage hallucinations and sense of presence were observed in both groups with similar frequencies (respectively P=0.60 and P=0.70). Multivariate analysis adjusting for disease severity or duration confirmed these results. CONCLUSION: VI and VH in PD have different qualitative sensory modalities, with similar quantitative repercussion for patients, and similar association with modalities such as "sense of presence and passage hallucinations", in contrast to the generally accepted classification of VI as minor VH. REGISTRATION NUMBER: clinicaltrials.gov number NCT03454269.

Femtosecond time resolved coherent anti-Stokes Raman spectroscopy: experiment and modelization of speed memory effects on H2-N2 mixtures in the collision regime.

With the aim of temperature diagnostic, femtosecond time-resolved CARS (coherent anti-Stokes Raman spectroscopy) is applied to probe H2 in H2-N2 mixtures. In a first part, a Lorentzian profile is used to model the femtosecond CARS response. A difference between the experimental broadening and the expected one is observed in the collision regime. The observed broadening increases strongly in an inhomogeneous way with respect to the perturber concentration. This is of considerable importance for temperature measurements. In a second part, we show that in the collision regime, this inhomogeneous broadening is due to the speed dependence of the collisional parameters and the memory effects of the radiator speed. A new modelization of the time-resolved CARS response taking into account the speed memory effects is presented and applied to the temperature diagnostic in H2-N2 mixtures. The numerical results are in good agreement with experiments.