PSYCH 3220 Exam 2 Unit 2: Visual Cortex

what is the geniculostriate pathway

the main route for visual information: photoreceptors → bipolar cells → ganglion cells → LGN in the thalamus → primary visual cortex (V1)

what does LGN stand for, and where is it

lateral geniculate nucleus; it is in the thalamus

what forms the optic nerve

the axons of retinal ganglion cells

where do most ganglion cell axons go

about 90% travel to the LGN, about 10% head to the superior colliculus, and some also go to the SCN

what happens to information form the nasal retina at the optic chiasm

it crosses to the opposite side of the brain

what are optic radiations

white matter tracts that carry visual information from the LGN to V1

does each side of V1 receive information from the same-side eye or the opposite visual field

The opposite visual field. for example, the right visual field is processed by the left V1

what does a simple cortical cell respond best to

a bar with a particular orientation

what does a complex cell respond best to

a moving bar with a particular orientation

what does an end-stopped cell respond best to

a moving line of a particular length and direction

what is a feature detector

a neuron that responds especially to a particular visual feature, such as a line’s orientation or movement

what is selective adaptation

exposing someone to one kind of stimulus, then testing how that exposure affects their responses to a range of stimuli, it can be studied with humans

what is selective rearing

raising animals in specially controlled visual environments to study how visual experience affects the developing cortex

what can happen when an animal is raised seeing only vertical stripes

It may fail to develop cortical neurons that respond to horizontal stripes. This demonstrates how visual experience can shape the cortex

what is monocular rearing

restricting vision to one eye from birth during the critical period

how can monocular rearing affect ocular dominance

it can shift cortical dominance toward the eye that was not occluded

what is a retinotopic map

an organized map in the visual cortex where neighboring areas represent neighboring locations on the retina

what is cortical magnification

a small area of the retina, especially the fovea, activates a disproportionately large area of cortex

does an object appear larger just because it image falls on the fovea

no, the fovea receives more cortical representation, but that does not make the object look larger

what does lateralization mean for V1

each side of V1 processes information from the opposite visual field, not simply from the opposite eye

what are cortical columns

groups of neurons in the visual cortex organized by properties such as eye preference, receptive-field location, or orientation preference

what is a hypercolumn

A unit of visual cortex that combines columns representing different features for one area of the retina, including multiple orientation preferences.

what is an ocular dominance column

a column of neurons that responds more strongly to stimulation of one eye

what is a location column

a column containing neurons with receptive fields at the same location on the retina

what is an orientation column

a column containing neurons with the same preferred stimulus orientation

what is the extrastriate cortex

visual cortex outside V1; includes areas such as V2, V4, and V5/MT

what does the dorsal stream process, and where does it go

the “where/how” stream processes spatial information, including object movement and location. it travels toward the parietal lobe

what is the general route of the dorsal stream, aka the “where”

V1 → V2 → V5/MT, which helps perceive movement → posterior parietal cortex, which helps locate objects in space

what does the ventral stream process, and where does it go

the “what” stream supports object recognition and travels toward the temporal lobe

what is the general route of the ventral stream, aka the “what”

V1 → V2 → V4, associated with color perception → inferotemporal (IT) cortex, associated with object recognition

what is the tectopulvinar pathway

a route for nonconscious visual information: some ganglion cells → superior colliculus → pulvinar in the thalamus → parietal and temporal lobes

what is blindsight

the ability to respond to or locate visual stimuli without conscious visual awareness, associated in the notes with damage to both V1 areas