The ability of the retina and brain to report the absolute light intensity (irradiance) in the environment was first observed half a century ago. However, its physiological basis is still poorly understood. The only retinal output neurons that are capable of transmitting intensity-encoding signals are called ipRGCs - intrinsically photosensitive retinal ganglion cells. These intensity signals have a remarkably diverse array of functional effects at many levels of the central nervous system, from modulation of sleep, activity and hormonal rhythms, through regulation of pupil size, to light avoidance and retinal development. New evidence suggests that they affect both the retina itself (a possible substrate for light adaptation) and the limbic thalamus and cortex (through which they appear to mediate effects of light on mood). Our current research is devoted to better understanding both of these novel output modalities of the ipRGC network.
We use mouse genetic models and combine:
Reconstruction of neural circuits using light and electron microscopy
in vitro and in vivo electrophysiology and functional imaging
Optogenetic and chemogenetic manipulations of neural activity
These powerful and complementary approaches allow us to reveal the operation of specific neural circuits and their role in shaping the behavior of animals in unprecedented detail.