cognitive psych -- intro and visual perception (retinal ganglion cells, visual system...)

What is cognitive psychology?

the scientific study of how the mind works

What is cognition?

processes relating to knwoledge or information
taking into account: acquisition, storage, transformation and use

what are the major goals and assumptions of the information-processing approach?

major goal = specify the processes and structures involved in cognition
major assumption = processing in people resembles processing in computers

what is visual perception?

result of an interaction between the external stimulus and the visual system

how does the visual system work?

visual system is hierarchically organised
informatio goes from : retina, LGN, primary visual cortex, other cortical regions specialised for vision

how do connections in bipolar cell's receptive fields work?

bipolar cells make indirect connections to surrounding photoreceptors

Direct + indirect connections = opposite electrical responses in the bipolar cell

The complexity of receptive fields increases through the visual processing hierarchy

Visual neurons become responsive to specific complex stimuli

ON-centre bipolar cells

Light falling into the receptive fields' centre photoreceptors causes an excitatory response

Light falling outside the receptive fields' centre photoreceptors causes an inhibitory response

OFF-centre bipolar cells

Light falling into the receptive fields' centre photoreceptors causes an inhibitory response

Light falling outside the receptive fields' centre photoreceptors causes an excitatory response

what are midget cells?

type of retinal ganglion cells

they have: small receptive fields, aren't sensitive to fast flicker, red-green colour selectiveness and work in the "what stream"

what are parasol cells?

type of retinal ganglion cells

they have: large receptive fields, are sensitive to fast flicker, aren't colour selective, work in the "where stream"

how does spatial frequency work?

Different populations of primary visual cortex neurons are sensitive to different spatial frequencies

Spatial frequency is encoded by population code , over a population of neurons sensitive to different spatial frequencies

Neurons selective for low spatial frequencies encode broad patterns of light and dark
neurons selected for high spatial frequencies do the opposite

what is the contrast sensitivity function?

human contrast sensitivity as a spatial frequency and peaks at medium spatial frequencies