Last night, I listened to the latest Zoom lecture presented by my great and good friends of the Secret Science Club, featuring psychiatrist and bioengineer Karl Deisseroth of Stanford University. This lecture was cosponsored by the Lasker Foundation, which presents an annual lecture with the SSC. Dr Deisseroth's book Projections: A Story of Human Emotions came out this year.
This is going to be a somewhat short recap, because I accidentally deleted about half of the original post I was pretty much liveblogging. It was a long day, and I was beat,,,
Dr Deisseroth began his lecture by describing the discovery that free-swimming green algae could move towards light sources. These algae have rudimentary eyespots, which interact with flagellae which enable them to swim. There is a correlation between activation of the eyespot/flagellum connection and an electrical current. Among these motile algae is the colonial alga Volvox.
This discovery ultimately led to the discovery of rhodopsins, proteins activated by light. A variety of rhodopsins, channelrhodopsins, are ion channels, which allow ions to move across membranes in a cell. There are three families of channelrhodopsins.
The study of channelrhodopsins allowed the development of the field of optogenetics, in which channelrhodopsins are inserted into neurons to allow the manipulation of nerve impulses through the use of light. Biological drives, such as hunger and social drives can be manipulated by shining lights of different colors onto neurons in which channelrhodopsins have been inserted. For example, a mouse can be induced to walk in circles by the use of light.
One of the fundamental challenges of neurobiology is the determination of what particular cells do. Optogenetics can help determine what is going on in the individual cell, through the use of markers in neurons.
As a psychiatrist, Dr Deisseroth studied dissociation, a conscious state where normally integrated cognitive procesess selectively uncouple from affective responses. Dissociation can be caused by PTSD, certain drugs, psychilogical disorders, trauma, and epilepsy. Dissociation can be studied through optogenetics.
Studying mice dosed with ketamine, a dissociative drug, researchers determined that a layer of the
unbiased screen with optics- surface of mouse brain observed as saline or dissociative drug ketamine added, brain activity occur. Ketamine affects retrosplenial cortex, interfering with the typical oscillation of nerve impulses.
Using optogenetics, researchers mapped out connections between the retrosplenial cortex and the deep structures of the thalamus to determine the neural pathways involved in dissociative disorders
Kudos to Dr Deisseroth, the Lasker Foundation, and Margaret and Dorian for delivering a fantastic lecture which I have not done justice to. Here's a video of the good Doctor explaining the use of optogenetics in studying the brain:
Pour yourself a nice beverage, and soak in that SCIENCE!