Cochlear implants and the bionic eye

Question 1

Place coding of frequency along the basilar membrane

Answer 1

-High frequency at base of basilar membrane (cochlea)
-Low frequency at apex of basilar membrane (cochlea)

Question 2

Cochlear implants

Answer 2

-Electrodes inserted along the basilar membrane
-Stimulation causes spiral ganglion cells to generate action potentials
Challenges
-A large number of electrodes to reproduce sound well
-Fast sound processors required to determine how much of each frequency is in the sound
-Our brain loses capacity to make sense of novel input as we age (people with congenital hearing loss need implants at a young age)

Question 3

Colour of light determined by:

Answer 3

Hue – the wavelength of electromagnetic radiation
Brightness – the intensity of electromagnetic radiation
Saturation – the purity of electromagnetic radiation

Question 4

Layers of retina

Answer 4

The retina can be divided into distinct layers:
1) Photoreceptor layer
2) Bipolar cell layer
3) Ganglion cell layer
-Rods and cones form synapses with bipolar cells (which form synapses with ganglion cells)
-Ganglion cells send axons through optic nerve  visual info to brain

Question 5

Deuteranopia

Answer 5

colour blindness caused by the absence of green cones

Question 6

Protanopia

Answer 6

colour blindness caused by the absence of red cones

Question 7

The retinogeniculate pathway

Answer 7

-LGN contains 6 layers of neurons
 Inner two are magnocellular
 Outer four are parvocellular
 Koniocellular sublayers are found below each of the magno and parvocellular layers
-Projects to primary visual cortex in the occipital lobe

Question 8

Centre surround receptive field structure in LGN

Answer 8

-A small bar of light passing over the ON region of LGN cell’s receptive field
will increasing firing rate; a bar that passes over the OFF region will decrease
firing rate

Question 9

Suprachiasmatic nucleus

Answer 9

in hypothalamus, receives light information from the
environment and uses it to entrain behaviours to 24 hour light/ dark cycle
VIA MELANOPSIN GANGLION CELLS

Question 10

Bionic Eye

Answer 10

-Device consisting of: camera for collecting visual scene information/ receiver for processing image data/ implant that converts image data to electrical impulses
-Implant generates an array of phosphenes (looks like a picture made up of light dots)