The use of optogenetics in Parkinson's Disease research could potentially do wonders towards finding treatment and cures for the disease. Kravitz and his team published a paper in Nature that showed that optogenetics could improve an animal model of Parkinsonism! (Granted, they also showed they could worsen it). Optogenetics, which utilizes different expressed proteins to inhibit or increase neuronal firing with light, is a very useful tool in this field.
Optogenetics use simple viral carrier systems that help deliver genes to the neurons; opsins (Channel rhodopsin being used to activate firing potentials and Halorhodopsin to inhibit them with different wavelengths of light) allow for this to happen, and ultimately allow for neuronal firing to be manipulated at precise milisecond intervals.
In the case of the Parkinsonian research, the experiment performed was a manipulation of the basal ganglial pathways (which are suspects implied in PD). There was optogenetic control via channelrhodospin of MSNs (medium spiny projection neurons) as well as regulation of dopamine receptors. If the direct pathway was activated, there was an increase of locomotion as well as a reduction of "freezing", which had been observed when the indirect pathway was activated and parkinsonian states were elicited (which had decreased locomotion and increased freezing). Intrigued to see where this will go in the future!
Read more: http://www.nature.com/nature/journal/v466/n7306/abs/nature09159.html