H7 The seeing brain Flashcards
sensation
the effects of a stimulus on the sensory organs
perception
the elaboration & interpretation of a sensory stimulus based on previous knowledge
retina
internal surface of the eyes that consists of multiple layers. some layers contain photoreceptors that convert light to neural signals & others consist of neurons themselves
rod cells
type of photoreceptor specialized for low levels of light intensity
cone cells
type of photoreceptor specialized for high levels of light intensity & detection of different wavelenghts
receptive field
region of space that elicits a response from a given neuron
fovea
point with the highest concentration of cones
blind spot
the point at which the optic nerve leaves the eye (no rods & cones present here)
primary visual cortex (V1)
1st stage of visual processing in the cortex; combines simple visual features into more complex ones
simple cells
in vision, cells that respond to light in a particular orientation /points of light along that line
complex cells
in vision, respond to light in a particular orientation but not to single points of light
hypercomplex cells
in vision, respond to particular orientations & lenghts
hemianopia
cortical blindness restricted to 1 half of the visual field (damage in V1 in 1 hemisphere)
quandrantanopia
cortical blindness restricted to a quarter of the visual field
scotoma
small region of cortical blindness
retinopic organization
the receptive fields of a set of neurons are organized in such a way as to reflect the spatial organization present in the retina
blindsight
symptom in which patient denies having seen a visual stimulus even though behavior implies that stimulus was in fact seen
ventral stream
pathway in vision extending from occipital lobes →temporal lobes involved in object recognition, memory & semantics
dorsal stream
pathway in vision from occipital lobes → parietal lobes involved in visually guided action & attention
achromatopsia
brain damage that impairs color perception
akinetopsia
brain damage that impairs movement perception
V4
region of the extrastriate cortex associated with color perception
V5
region of the extrastriate cortex associated with motion perception
color constancy
color of a surface is perceived as constant even when illuminated in different lighting conditions
biological motion
the ability to detect whether a stimulus is animate or not from movement cues alone
structural descriptions
a memory representation of the 3D structure of objects
apperceptive agnosia
failure to understand the meaning of objects due to a deficit at the level of object perception
associative agnosia
failure to understand meaning of objects due to deficit at level of semantic memory
figure-ground segregation
process of segmenting a visual display into objects versus background surfaces
Gestalt approach
5 basic principles of how visual features are combined
1) law of proximity
2) law of similarity
3) = of good continuation
4) = of closure
5) = of common fate
lateral occipital complex (LOC)
region of the brain that is specialized for processing object shapes
integrative agnosia
failure to integrate parts into wholes in visual perception
object constancy
understanding that objects remain = irrespective of differences in viewing condition
viewpoint-invariant theories
theories that argue that particular object parts or features are mapped directly to structural descriptions
viewpoint-dependent theories
argue that seeing an object from an unusual view requires a ‘mental rotation’ into a normal viewpoint
adaptation
reduced neural response to a stimulus/stimulus feature that is repeated
category specificity
notion that the brain represents different categories in different ways
face recognition units (FRUs)
stored knowledge of the 3D structure of familiar faces
person identity nodes (PINs)
abstract description of people that links together perceptual knowledge with semantic knowledge
prosopagnosia
inability to recognize previously familiar faces
fusiform face area (FFA)
area in the inferior temporal lobes that responds more to faces & is implicated in processing facial identity
categorical perception
tendency to perceive ambiguous or hybrid stimuli as either one thing or the other
geniculostriate pathway
pathway from eye to brain that goes via lateral geniculate nucleus (LGN) and terminates in striate
cortex (another name for V1)
