Faulty neural circuits

Question 1

Retinitis pigmentosa

Answer 1

one of the most common causes of blindness progresses to reduce the field of view to become smaller and smaller until the patient is completely blind

Question 2

How does retinitis pigmentosa occur?

Answer 2

mutations that decrease the number of photoreceptors and cause damage to whole of photoreceptor layer

Question 3

How can halorhodopsin be used to treat retinitis pigmentosa?

Answer 3

expressed in remaining parts of photoreceptors leads to hyperpolarisation which mimics wild type retina
centre surround + direction selectivity intact

Question 4

Halorhodopsin

Answer 4

hyperpolarises cells in response to yellow light so that vision using remaining cells is restored

Question 5

Channelrhodopsin

Answer 5

depoalrises in response to blue light so can be used in retinal cells that are not normally light sensitive

Question 6

What are the problems with retinal implants?

Answer 6

stimulates retinal ganglion cells but not photoreceptors or bipolar cells

Question 7

How can epilepsy be corrected?

Answer 7

use halorhodopsin in excitatory cells
use channelrhodopsin in inhibitory cells
inject virus using optogenetic tools

Question 8

Controlling seizures in mice using halorhodopsin

Answer 8

light stimulation -> no seizure
no light stimulation -> seizure