Effects of light on emotional processing

Low or disorganised patterns of light exposure have been associated with both
mood and sleep disturbances. In Parkinson*s disease (PD) which is traditionally
treated with dopamine replacement and deep brain stimulation, neuro modulation
through the visual system is becoming a viable non-invasive alternative for
treating the non-motor (enhance mood and attenuate sleep disturbances) and
motor symptoms of PD. Light ameliorates disturbances of mood, sleep and
performance in elderly people with major depression. The neurobiological
mechanisms underlying the positive effects of light in PD and depression remain
poorly understood. Therefore, further work is required to better understand how
light modulates brain activations in response to different emotional valence in
persons with PD and in persons with symptoms of depression .

Our primary objectives are to study: 1) differences in the brain*s sensitivity
to the effects of light on emotional processing in people with PD and people
with depressive symptoms compared with healthy controls 2) whether different
spectrum of light modify emotional brain responses; 3) determine whether the
magnitude of post-illumination pupil response and PD/depressionsymptoms
severity correlates with the effects of blue light (as opposed to red light) on
emotional brain responses. Secondary objective : 1) determine if the
association between affective state, sleep and ambient light in the natural
environment are mediated by the degree of sensitivity of the brain to light.

Case-control study involving 10-days of ambulatory monitoring, followed by an
MRI session and pupillometry.

This study involves 2 site visits and 10 days of ambulatory monitoring. Total
participation time is approximately 7 hours (including components done at
home). Overall, the risk associated with participation can be considered
negligible and the burden can be considered modest.
For the multi-parameter ambulatory recording, participants will wear
thee small non-invasive and nonintrusive integrated sensors and recorders.
Wearing of these ambulatory sensors is of negligible burden and without risk.
To avoid any risk during light stimulation, the maximum intensities of
the light source in the set-up are well below the recommendations of the
American National Standard (ANSI-2007) for red, blue and white illumination.
These sub-threshold intensities, in combination with the limited exposure
durations, and exclusion of participants with increased retinal sensitivity to
light, will eliminate any risk associated with bright light exposure.
In the PD group the fMRI experiment is conducted while patients are at
the end of their regular dopaminergic medication cycle (i.e., while
experiencing the end-of-dose phenomenon), because this closely resembles the
real-life clinical situation. As in their usual daily life participants are
likely to experience increased PD symptoms end-of-dose which will directly
resolve upon intake of their usual medication after the assessment. No risks
are associated with a transient end-of-dose state and this is common practice
in PD research.