SENSATION + PERCEPTION

colour constancy

brain’s ability to recognize colour of an object as being the same even under different light conditions

sensation

process by which sensory organs detect environmental stimuli + convert them into electrical signals for the nervous system

stimulus

something that elicits a reaction from our sensory systems

transduction

transformation of sensory stimuli energy into neural impulses

perception

brain’s interpretation of these electrical signals to create an internal representation of the world

bottom-up processing

interpretation based on raw sensory data

top-down processing

interpretation based on prior experience, knowledge + expectations

pyschophysics

study of relationship between the physical qualities of stimuli (physics) and our mental experience of them (psyche)

absolute threshold

minimum amount of stimulus that can be detected > 50% of the time

liberal bias

low threshold for detecting a signal

sensitivity

ability to perceive and process information about the environment (inverse of the threshold value)

conservative bias

high threshold for detecting a signal

just-noticeable difference/difference threshold

smallest difference betwen two stimuli that c an be detected more than 50 % of the time

weber’s law

as stimuli increases, differences must become larger to be ditectable

weber’s fraction = minimum change in stimulus/stimulus

adaptation

stop noticing a stimulus that remains constant over time

vision

processing of light reflected from objects

visible light

type of electromagnetic radiation emitted by the sun, artificial light etc,, that can be detected by the eye

wavelength

distance between successive peaks

amplitude

height of wave

cornea

transparent tissue covering the front of eye, focuses light

iris

opaque, colourful muscle encircling pupil

pupil

hole in the iris where light enters the eye

lens

membrane at front of the eye that focuses incoming light on the retina

accomodation

adjustments of the lens’ thickness by specialized muscles in order to change the degree to which it bends light

retina

surface in the back of the eye containing photoreceptors

photoreceptors

receptor cells specialized for transducing light (rods + cones)

rod

photoreceptor cell that primarily supports nighttime vision

cone

photoreceptor cell that is responsible for high-resolution colour vision

visual transduction

when light reaches the photoreceptors + photo pigments undergo chemical reactions to generate electrical signals

photo pigments

light sensitive molecules

blind spot

area in the middle of the visual field where there are no photoreceptors and no information can be received

rods vs cones

1. rods all have same type of photopigment, cones have 3 options

2. rods contain rhodopsin

3. rod to cone ratea of 20:1 (cones are concentrated in fovea while rods are in central periphery)

4. cones have more direct connections to neural celsl; rods converge more

5. cones recieve more cortical representation

6. cones have higher acuity, wheras rods have higher sensitivity

rhodopsin

light-sensitive pigment that lets us see in the dark

fovea

small pit in centre of the retina that plays an essential role in our ability to see fine details and perceive color

trichromatic theory

3 types of cells work togehter to produce perception of colour

ganglion cells

cells in the retina that are organized in pairs that respond to opposing colours and receive input from cones

prosopagnosia

inability to recognize faces

feature detectors

specialized neurons that respond to specific attributes of visual stimuli

processes of higher-level vision

The brain processes and organizes the data it receives from the retina through hierarchical

series of steps of increasing complexity

1. Visual information travels along optic nerve to optic chiasm, where axons from each side of the retinas are diverted to corresponding side of the brain

2. Thalamus (relay station) passes information on to primary visual cortex

3. Image reconstructed in primary visual cortex

4. Visual association cortex combines incoming sensory inputs with prior knowledge & expectations

5. Additional processing in temporal lobe allows

   you to recognize specific objects, like faces

ventral stream

processes ‘what’ information, responsible for recognizing objects + faces

dorsal stream

processes ‘where’ information, responsible for determining location + the perception ofmovement

gestalt psychology

perspective that we perceive whole, organized patterns and objects

figure + ground

the automatic tendency to divide visual scenes into an object of main focus (figure) and ground (background)

depth perception

brain uses various cues to translate a 2-d image projected onto to the retina into 30d

binocular cues

depth information gathered from the separation between an individual’s two eyes

binocular disparity

cue for depth perception stemming from the slightly disparate views that two eyes have on an object or scene

monocular cues

depth information that can be gathered using just one eye

motion parallax

when you move your head, objects closer to you appear to move faster than objects farther away

linear perspective

parallel lines appear to converge in distance

interposition

nearby objects occlude more distant ones

relative height

objects further away appear closer to the horizon

relative size

objects further away appear smaller than nearby objects

size constancy

objects further away project a smaller image on the retina, but brain accounts for variation in retinal images + interprets it as a cue for depth

sound

waves of vibration in the form of mini collisions between adjacent molecules in a medium like air or liquids

frequency

number of cycles that occur per second, measured in Hertz (hz)

pitch

the highness or lowness of sound (determined by frequency, the greater the frequency the higher the pitch)

volume

the loudness of sound (determined by amplitude, the higher the amplitude the louder the sound)

pinna

captures and funnels soundwaves through auditory canal towards the middle ear

middle ear

contains the eardrum and the ossicles

human ear

components that work together to collect, amplify + transduce vibrations into neural signals

ossicles

tiny bones located between two membranes, amplify vibrations of incoming soundwaves + protect inner ear from loud noises

inner ear

contains the vestibular system + cochlea

basilar membrane

in the cochlea, contains specialized receptor cells for transducing vibrations transmitted into the inner ear into neural signals, occurs when hairlike auditory cilia bend in response to vibration, signal then carried along auditory nerve to the brain

place theory

theory proposing that different sound frequencies are processed at different parts of the basilar membrane, accounts for selective hearing loss

frequency theory

theory proposing that frequency of auditory neurons firing matches frequency of sound wave, for higher frequencies, groups of neurons alternate firing to match frequency

primary auditory cortex

contains place-frequency maps

sound localization

brain compares information coming from each ear to determine relative timing + intensity

tactile sense

perception of touch

mechanoreceptors

sensory receptors that respond to mechanical stimulation (eg, pressure, touch, vibration, stretch)

• myelinated mechanoreceptors allow for fine-grained discriminations

tactile agnosia

inability to recognize object by touch (caused by damage to association areas)

interoception

ability to perceive signals originating within the body

insula

part of the insular cortex, plays key role in processing bodies signals (interoception), imbues them with emotional and motivational significance

proprioception

sensory experience of the body’s position in space

proprioceptors

special receptors in muscles, tendons, joins that detect changes in muscle length, tension + joint position

vestibular system

system in the inner ear that helps maintain balance by detecting head movements and motion (information travels along auditory nerve to medulla + cerebellum then somatosensory cortex + primary motor cortex)

vestibulo-ocular reflex

reflex that helps stabilize gaze during head movements (signal moves from semicircular canals to the brainstem, which then coordinates eye muscles to move eyes in opposite direction of head )

olfaction

sense of smell (important for enhancement of taste, detection of hazards)

epithelium

mucous membrane in the nasal factory that contains olfactory cilia

olfactory cilia

olfactory receptor neurons

olfactory bulb

structure that recieves input from olfactory sensory neurons, responsible for basics processing + contains glomeruli

glomeruli

patters of activations that encode different odours

higher-level oflactory processing

infromation from olfactory bulb is sent to amygdala and hippocampus (parts of the limbic system) which allows us to make odour-memory connections

small → flavour

opening connecting back of mouth cavity w nasal cavity lets us smell substances that have entered the mouth

orbitofrontal cortex

part of olfcation association cortex, where smell and taste converge

gustation

sense of taste, taste receptors on the tongue correspond to 5 tastes (sweet, salty, sour, bitter, savoury/umami)

primary gustatory cortex

in the insula, sends connections to many cortical areas (, including orbitofrontal cortex, where neural signals for taste and smell are combined)

mcGurk effect

visual stimulus changes perception of sound (sight has dominance over other senses, particularly sound)

light/dark adaptation

rhodopsin (rod photochemical) breaks down and becomes inactive when exposed to bright light but regenerates in the dark

opponent-process theory

perceptual systems treat the visible spectrum as a circle, where the two ends meet (therefore cannot see ‘reddish-green‘ or ‘yellowish-blue‘ as the colours cancel each other out because ganglion cells are excited by one or the other)

afterimages

image that appears in eyes after a period of exposure to the original image (occurs because cones get fatigued after looking at one colour for too long and the ganglion cells begin to send weaker signals corresponding to that, then the opposing cells fire, sending signals that cause the perception of the opposing colour)

visual association cortex

combines incoming sensory inputs w prior knowledge + expectations

visual agnosia

inability to recognize visually presented objects

gestalt principles

• identified principles that the visual system follows to organize incoming data and recognize objects

  • proximity

  • simalarity

  • closure

  • good continuation

reversible figures

demonstrate how our overall perception of an object may differ from the elements from which its perception is derived

illusory contours

how the whole affects perception of parts, we let our prior expectations affect our perception of the shape

perceptual stability

tendency to perceive an object you’re familiar with as having constant shape, size, and brightness despite stimuli changes

evolutionary purpose of taste

• promotes increased nutrition

• prevents intake of poison

rubber hand illusion

• experimenter hides your hand and places rubber hand on table

• experimenter strokes your hidden hand and the fake rubber hand at the same time with a dual stick instrument

• the rubber hand seems to become your own and feel the stroking sensation

• vision tells your somatosensory cortex to shift its sensation to an area where receptors do not even exist

primary somatosensory cortex

cortex dedicated to sense of touch

primary sensory area

first cortical region in each lobe to recieve signals from its associated sensory nerves