p258 perception module 4

visual perception how work

• light from above hits bottom of the retina

• lights from below hits the top of retina

• images are projected upside down into retina

retina

made up of layers of neurons; final layer comprosed of light-sensitive neurson called photorecptors

rods

• very light sensitive

• requires less light

• better for seeing at night

• reduced resolution

• color-blind (blakc n white)

• spread throughout the rest of retina, called periphery

cones

• less light sensitive (needs more light)

• high resolution

• better for well lit conditions

• different structural variations respond to colours

• packed into center of the retina, aka fovea

fovea and where (insert pic)

cones packed here at center of retina

periphery

spread throughout the rest of the retina

photorecptors…retina

transduce light into neural code, signals are passed on to additional layers of neurons in the retina

neural circuit

optic nerve

thalamus

what does the eye tell the brain

sparse code

computer algorithm that needs a small number of hidden nodes to represent a stimulus

emerging idea in the field

like localization of function in the brain, regions of the visual cortex respond to specific classes of stimuli

agnosias

cases in which individuals have difficulty perceiving one type of visual stimulus, but not another

countervailing view of visual processing

regions are not specialized for function

dorsal visual streams

• projects upwards and stops in the parietal lobe

• ex: monkeys w lesions in the dorsal stream could do discriminating task, but had impairments comparing the location of objects across trials

ventral visual stream

projects downwards and stops in temporal lobe

• monkeys w lesions in the ventral stream had difficulty doing matching tasks

Goodale and milner what they did

observed differences in patients ith dorsal and ventral stream danger

auditory nervous system pieces

• ossicles

• pinna

• ear cannal

• eardrum

• cochlea

ossiscles

pinna

ear canal

cochlea

tiny coiled bone structure filled w fluid

coil shaped

basilar membrane and mechanoreceptors

strip of tissue w tiny hair cells called mechanoreceptors that move in vibration w fluid in the cochlea

why do ears have such complex structure

• due to underwater env in which human’s brains and bodies first evolved

• sound loses amplitude when moving through water

• our ears still designed as if we live underwater

tonotopic map

• responding frequencies decrease as the coil progresses inward

• sound signal is systematically organized into different frequencies as it is sent to the brain

• organization is preserved as signals are sent to subcortical structures to the auditory cortex

primary audtiory cortex (A1) is where and responds to what

• in temporal lobe

• neurons in A1 respond to specific stimuli

• respond to pitch and rhythm of soundwaves

slide 33 module 4

differing lengths of sound waves means…

• short = choppier waves

  • ex: mouse vocal chord

• long = slower waves

  • ex: lion vocal chords

height of sound waves

olfaction

sense of smell

measure chemicals moving through the air

gustation

sense of taste

measure chemicals that have been ingested

what are receptors on tongue called, and 5 types

• taste buds

• sweet

• sour

• salty

• savoury

• bitter

Chemical process when tasting

• chemicals bind to receptors

• chnages in electrical potentioa

• neurotramitter realzes

• signla transmitted to brain stem

• signals relayed to primary gustatory cortex

  • lateral sulcus

  • or frontal lobe

olfactory system how work

• begins in nose and throat

• molecules pass thro olfactory emithelium

• strip of tissue in nasal caivty w milliong of chem receptors

• neurons transduce chemical information sending it to olfactory bulb

• incomplete

flavor

combo of olfactory and gustatory perception

• smell contributes more to flavour than taste

rodent model of taste and smell

cortical homunculus

spatially organized map of the body

locations on the mpa respond to touch on specific regions of the body

enlarged portions of the body (hands) are dense w receptors

regions of the cortex are distorted bc receptor density

Construction perception (unconscious inference) person and defintion

• hermann von Helmholtz

• brain’s attempt to construct a model of the external world based on sensory input

• sensory perception ==> mental model (one stable model of outside world) ==> action

evidence for constructive perception

• our eyes move several times per minutes

• yet we perceive static not jittered pics

James Gibson Direct Perception

• behaviour is directly based on sensor input from env without the construction of a mental model

• sensory stimulus ==> action

what did Muller thing of direct model

• didnt make much sense

• sensory perception > formation of nerve pathways > action

Helmholtz model

Constructivist theory

• sensory data is used as evidence to construct the 3D external world ‘

• reality we percieve is construction of the brain

illusions

• when the brain wrongly infers environments from sensory input

• misperceiving the lightness of an object

Why do our brains fall for illusions and ex

• our brains are more concerned w stable traits of objects

  • light bouncing off an objects varies in env

  • but reflectance is less variable

• ex: pink backpack perceived as pink whether inside or outside in varying light conditions

bistable stimuli

• images in which brain can change its mind when it views it

• incomplete