Vision

Wavelength = perception of colour

Intensity = perception of brightness

Sensitivity = ability to see when light is dim

Acuity = ability to see details

Eye consists of optic nerve - optic chiasm - optic tract - lateral geniculate nucleus - optic radiation - primary visual cortex

Convergence = eyes turn slightly inward when objects are close

Binocular disparity = difference between images on two retinas

The lens focuses light on retina and ciliary muscles alter shape of lens. Accomodation = adjusting lens to focus e.g. spherical for nearer, flatter for farther

In the dark, Na+ channels remain partially open releasing glutamate (partial depolarisation) and when light Na+ channels close and rods hyperpolarise inhibiting glutamate

Rhodopsin = pigment found in rods, a G protein linked to receptor that responds to light

Cones => phototopic vision with high acuity colour in good lighting. Located more on inside of retina and are less sensitive to light, as well as allowing rapid changes and finer details

Rods => scotopic vision with low acuity in dim light and lacks detail and colour info. Located more on outer retina and converge on a single interneuron, making peripheral vision and sensitivity to movement and blue area of spectrum.

Lateral Geniculate Nuceli:

• Thalamus
• 6 layers neurones receiving input from 1 eye
• Layers 1+2 = magnocellular
• Layers 3-6 = parvocellular
• Also koniocellular sub-layers

M+P Channels:

• Magnocellular layers = big cell bodies, respond to movements and input from rods
• Parvocellular layers = small cell bodies, colour detail or slow/still objects and input from cones

V1 = Contour integration and surface segmentation

V2 = Properties related to object surfaces

V4 = Integration of colour and object shape

V5 (MT) = Integration of motion signals

Ventral (WHAT) Stream = to inferotemporal cortex (ITC). Centre of object recognition and linked to hippocampus, prefrontal cortex and amygdala

Dorsal (WHERE) Stream = to posterier parietal cortex. Localisation of objects and interactions.