Cognitive Neuroscience - Vision

The retina has 3 layers of cells: the , and .

While cells or the retina are responsible for dim light vision, cells of the retina are responsible for daytime vision.

The optic nerve crosses at the , such that each side of the brain receives visual information from the opposite side of the .

The of the is the primary relay nucleus for visual processing.

In the context of visual processing, the receptive field of a neuron refers to the region in the that elicits a response from that particular neuron.

When a spot of light falls on the centre of the receptive field of an ON (ganglion) cell, the cell will be ; when a spot of light falls on the surround of its receptive field, the cell will be .

When a spot of light falls on the centre of the receptive field of an OFF (ganglion) cell, the cell will be ; when a spot of light falls on the surround of its receptive field, the cell will be .

When light of the same level of luminance covers the entire receptive field of an ON or OFF cell, the firing rate of the cell will .

the contrasting centre-surround configuration of retinal ganglion cells enables the detection of .

cones respond maximally to short wavelength light or blue light. cones respond maximally to medium wavelength light or green light. cones respond maximally to long wavelength light or red light.

The ratio of the activity of three types of cone cells enables the coding of at the layer of the retina.

Neurons in the // of the cerebral cortex detect simple features of the visual scene, such as line orientation, colour and movement.

In area V1, cells are bar detectors; cells are movement detectors; and cells are edge detectors.

Area V4 specialises in .

Area V4 enables , which is referred to as the ability to recognise the colour of an object despite changes in lighting.

Area V5/MT contributes to .

Visual information leaves the occipital lobe via two streams or pathways: the stream consists of projections to posterior parietal regions, and the stream consists of projections to inferior temporal regions.

The stream of the visual system is specialised in object recognition, whereas the stream is specialised in locating objects in space and guiding movements.

When outlining the visual processing in the brain, the is where the visual scene is analysed in small segments, as each module within the area only focuses on one small portion of the . In the striate cortex neurons detect simple features such as . The regions provide the role of divide and conquer whereby these regions specialise in certain functions, such as for colour vision and for movement perception. The visions are then projected from the regions to other cortical areas via two separate streams: the stream and the stream. The ventral stream ('' pathway) is where simple features are combined into wholes for . The dorsal stream ('' and '' pathway): serves to and guides actions.