Perception Flashcards
What is perception
The set of processes by which we recognize, organize, and make sense of the sensations we receive from environmental stimuli
Is what we sense in our sensory organs they same as what we perceive
No
Problem solved by perception
Understand what is going on outside of the brain
Importance of perception
Necessary in order to know how to act in the world to achieve goals
Inverse problem of perception
Create a representation (perception) of what is out in the world (the distal stimulus) from what we sense (proximal stimulus)
Sources of information for perception
Genes
Past experience
Internal state
Environmental context
Proximal stimulus
What we learned on the timescale of evolution
Genes
Information learned on timescale of a human life
Past experience
Information learned on timescale of current episode
Internal state
Information learned now
Environmental context
Proximal stimulus
The stimulus itself -> pattern of light on eye
The energy or matter that impinges on the sensory receptors
Sensory system function
Do the conversion of proximal stimulus into neural signals
General sensory system steps
Distal stimulus
Proximal stimulus
Sensory receptors
Neural pathways
Hierarchy of cortical areas
Percept
Distal stimulus
Thing out in the world
Sensory receptos function
Specialized cells to transduce (convert) external phenomena (light, sound, pressure, etc…) into neural signals
Neural pathway
APs travel from sensory receptors via thalamic nuclei to cerebral cortex
Function of Hierarchy of cortical areas
Attempt to construct useful representation of distal stimulus
Percept definition
Mental representation of the distal stimulus after all the neural processing
Function of cornea
focuses light
Function of lens in eye
muscles cause it to change shape and focus light onto the retina
Retina
back surface of eye
Fovea
most sensitive part of retina where the light we are looking directly at lands
contains mostly cones
Optic disk
part of retina that has no photoreceptors → blind spot
Where cell axons exit the eye to form the optic nerve
Optic nerve
ganglion cell axons leaving the eye
Types of neurons in eye
Bipolar cells
Ganglion cells
Rods and cones (photoreceptors)
Explain the path of light into the eye
Light comes in onto the surface of the retina and passes through all the cell to get to the photoreceptors
Photoreceptos send signal to bipolar cells, which send signal to ganglion cells
Ganglion cell axons form the optic nerve
Photoreceptor function
Convert light into neural signals
Rod function and types
Only one type
don’t detect color
Just detects how much light there
Used in dim light
Cone function
Detect colour –> specific wavelengths
Used in bright lights
3 types:
S cones –> short wavelength
M cones –> medium wave
L –> long wavelength
Distribution of receptors on retina
Fovea contains only cones –> higher acuity
lots more rods in the periphery (greater eccentricity) –> lower visual acuity –> better dark vision out to the side
Can rods and cones increase their sensitivity
Yes
Where do the visual fields end up on the retina
Both visual fields end up on both retina
- Left visual field lands on right side of each eye
- Right visual field lands on left side of each eye
Where does the partial crossover of optic nerves occur
optic chiasm
Where does the left visual field end up
Right primary visual cortex (V1)
Where does the right visual field end up
Left primary visual cortex (V1)
How does the information from the visual field get flipped
Left/right and up/down
Single pathway of information from eye
Ganglion cells
LGN (thalamus)
Optic radiations
Primary visual cortex (V1)
Along which sulcus is V1 located
Calcarine sulcus
What is sound
changes in air pressure
What does the ear drum do
Ear drum (tympanum) converts changes in air pressure into mechanical vibrations
Where do the mechanical vibrations from the Ear drum travel to next
through bones of middle ear (ossicles) to oval window of cochlea
What are the sound receptor in the cochlea that detect vibration
Hair cells
Where does transaction of vibrations occur
Organ of Corti in between the tubes of the cochlea
Outer ear function
funnels sound into the ear
Middle ear parts
eardrum and ossicles
Inner ear parts
Cochlea
Names of ossicles
malleus
incus
stapes
What do ossicles do
pushes against oval window of the cochlea
What travels through the cochlea
pressure waves
What is the organ of corti made up of
Hair cells on a basilar membrane and has a loose membrane on top
What causes the hair cell ion channels to open or close
Tiplinks pull on ion channels when they swing one way and ions go in
when it swings the other way they close
mechanically gated
Organization of basilar membrane of cochlea
Which hair cell is active depends on frequency
Low frequency near tip
High frequency near base
Primary auditory pathway steps
Auditory nerve
Cochlear nuclei (medulla)
Superior olivary nucleus (pons)
Superior olivary nucleus (pons)
Inferior colliculus (midbrain)
Medial geniculate nucleus (thalamus)
Primary auditory cortex (temporal lobe)
Does auditory info switch sides
no because sound always arrives at both ears
Mechanoreception
Detects pressure, texture, vibration and distortion
Touch
Thermoception:
Detects hot and cold
Nocioception
Detects harmful chemical, mechanical, or thermal stimuli (too hot/cold)
Pain –> tissue damage
Proprioception
Detects mechanical forces on muscles, tendons and joints
Lets us know where we are relative to our body
Primary somatosensory pathway steps
Dorsal root ganglion (PNS)
Gracile/cuneate nuclei (medulla)
Ventral posterior nuclei (thalamus)
Primary somatosensory cortex (parietal lobe)
Where do all three sensory pathways pass
Thalamus and then to the cortex
Types of mechanoreceptors and meaning
RA1: Meissner corpuscle
RA2: Pacinian corpuscle
SA1: Merkel disk receptor
SA2: Ruffini endings
RA: rapidly adapting
SA: slowly adapting
1: close to surface –> smaller area of skin
2: deeper –> larger area of skin
Sensory adaptation definition
The proximal stimulus is represented on a relative scale, not an absolute scale
Where does the influence of context on perception occur
very early in the sensory pathways (eg: in the eye itself)
What does the sensitivity of the visual system to a light stimulus depend on
the ambient light level
How do photoreceptors adapt to changes in ambient light
Photoreceptors adjust their sensitivity depending on the environment light
Shifts between depending on rods or cones after they can’t adapt anymore
Will a faint light that is detected in a dark room also cause the same response of a ganglion cell in a light
No, you would need a brighter light in an lighter environment
State Weber’s law and equation
The JND is proportional to the magnitude of the stimulus
∆I/I =K
What is the JND
The “just noticeable difference” (JND) is the smallest detectable change (∆I) in a stimulus (I)
What is K in webers law and give example
K is the Weber fraction
K=0.05 = 5% difference noticable
What stays the same according to webers law
Ratio between size of JND and the size of the stimulus itself stays about the same
Purpose of webers law
Determine how small of a stimulus we can detect in a given situation
Does the Weber fraction stay the same in auditory adaptation
Yes
Weber’s law and weight explained
Need a larger difference (JND) in weight for heavier objects but the ratio stays the same
If the just noticeable difference for a 100g object is 5g then what is the JND for a 200g object
20g
Somatosensory adaptation function of SA and RA mechanoreceptors
Need rapid adaptors to detect texture
Need slower adaptors to detect weight or ongoing pressure
What is a receptive field
Area of sensory surface to which a neuron responds perceptual
Explain what Perceptual resolution and acuity are inversely
related to sensory receptive field size means
Smaller receptive field –> higher acuity/resolution
Larger receptive field –> less acuity/resolution
is resolution better for cones in the fovea or periphery
Fovea because they are more packed –> smaller receptive field
What size are the receive filed for higher order neurons and what is the complexity of the stimuli they respond to
Higher-order neurons have larger receptive fields –> combine info from lots of photo receptors
Higher-order neurons respond to more complex sensory stimuli –> tree or cloud
What is the visual receptive field of a cone
area on retina
How does the visual receptive field vary with eccentricity
Receptive fields get bigger farther out in the periphery
Explain what the receptive field of a retinal ganglion cell consists of
Lots of photoreceptors send output to a smaller number of bipolar cells
The bipolar cells send the output to one ganglion cell
Explain visual centre-surround receptive field of ganglion cell
On center-surround cells: excited when light hits the center and inhibited in the surround
Off center-surround cells: inhibited by light in the middle and excited by light in the surround
What would happen to a centre surround cell if you shined light on both the surround and the centre
It would mostly cancel out
What would happen if you make the surround dark for a surround centre cell
Cell would be very excited
How do we get a centre surround system
Done by wiring of the ganglion cells to other cells by combining excitatory and inhibitory inputs –> can make ON or OFF centre cells
What is the auditory receptive field of a hair cell
frequency of sound
What is the receptive field of a mechanoreceptor
area on skin
Where do receptive field size and acuity vary in the body
Tips of fingers have smaller receptive fields → high acuity/resolution
Back/thigh has large receptive fields → high acuity/resolution
Where do receptors respond strongest to touch
when touch is right above
Explain the somatosensory center-surround receptive fields and Lateral inhibition
Relay neurons (farther down the pathway) responds strongly to the touch in the center and respond negatively to touch in the periphery of the receptive field
What is the topography of the brain and its characteristics
Spatial organization (topography) of sensory surface is generally preserved in (projected onto) primary sensory cortex
If two sensory receptors are found next to each other where will they be represented in the cortex
beside each other
What is cortical magnification
Area of cortex is proportional to density of sensory receptors (and inversely related to receptive field size)
More receptors → smaller receptive field → more space on cortex
What is a retinotropic map and what does it show
Topographic map for vision
Location of a stimulus on the surface of the retina is being mapped onto the surface of primary visual cortex neural tissue (V1) in the occipital lobe
How is the retinotropic map different from the representation on the retina
Stimulus is flipped upside down and left/right
Cortical magnification can be seen
What part of our visual field is being processed the most and to what extend
The center 10 degrees of the retina takes up more than ½ of V1 space → cortical magnification
What is a tonotropic map and what does it show
topographic map for audition
In primary auditory cortex (temporal lobe) is organized by frequency
What is a somatotopic map and what does it show
topographic map for somatosensory
It shows the organization of primary somatosensory cortex (parietal lobe) by body area
Where is the upper left side of the body represented on the primary somatosensory cortex
on the lower right side
What areas take up a lot of space on the primary somatosensory cortex –> cortical magnification
hand and face
What does the Somatosensory homunculus show
a map along the cerebral cortex of where each part of the body is processed –> preserving the relative organization of different body parts
How are the topographic maps for taste represented
Based on taste quality (sweet, salty, sour, etc)
What is plasticity and where does it occur
Changes in neural organization
Occurs from the molecular to the systems level
What is synaptic plasticity and cortical plasticity
Synaptic plasticity: Changes in the strength of synapses
Cortical reorganization: Changes in topographic maps
What does creating a lesion in the retina of both eyes lead to and what happens
overtime the neurons now respond to activation of adjacent areas on retina
Lesion of the visual field (in both eyes!) leads to reorganization in primary visual cortex
What happens to somatotropic maps after amputation of limbs and how can this help patients
After amputation of arm, pursing of lips
causes perceived sensation in missing arm
Could scratch lips to get rid of itch in phantom limb
overtime the cells from primary somatosensory cortex begin to respond to receptive fields for other body parts
What is hierchial organization
Moving from lower-order sensory neurons
(those closer to sensory receptors)
to higher-order sensory neurons
(those farther from sensory receptors)
How information is processed after it reaches the cortex
What are lower-order motor neurons vs higher order motor neurons
Lower –>those closer to sensory receptors
Higher –> those farther from sensory receptors
What happens to receptive fields, sensory features, processing, and multi sensory integration as we move up the hierarchy in the brain
Receptive fields get larger
Sensory features get more complex (and abstract)
Sensory features get more specific
Processing proceeds in serial (sequentially),
in parallel (simultaneously), and is recurrent (loops)
Multi-sensory integration increases
What is recurrent processing
Connections from higher order areas back down
Basic function of the hierarchy in the brain
Start off with raw sensory information and we start processing it, combining it, refining it to get increasingly specific representations
What is the order of the cortical hierarchy found in the brain for visual, auditory, somatosensory systems
Start in primary cortex –> secondary cortex –> tertiary cortex
Hierarchy in visual system examples
Serial, parallel, and recurrent processing in the visual system
Info goes from V1, to V2 to V3 to V4 → serial processing
V1 is connected to a bunch of different areas → parallel processing
V1 is sending signals to V2 → V2 is also sending signals back to V1 → lots of recurrency
Modularity of visual hierarchy parts
Primary visual cortex = striate cortex = V1
Primary visual cortex= extrastriate cortex = V2, V3, V4, V5/MT
Tertiary visual cortex = visual association cortex = MST, LIP, etc…
Multimodal association cortex = VIP, etc…
What is the multimodal association cortex
Processes multiple sense
Orientation feature detector location in visual system and function. Are all of the orientations responded to?
V1
Neurons that respond to bar of light in a particular orientation
V1 would have neurons that respond to each orientations
Tuning curve function and meaning of broadly tuned
Tuning curve shows the spike rate of neurons to certain stimuli –> ex: stimulus orientations
broadly tuned → still responds to other stimuli just not as strongly –> ex: other orientations
How are orientation feature detectors built
from having multiple center surround neurons feed their output to another neuron
Because the other neurons (neuron 2) is receiving input from the 4 neurons with center-surround receptive fields → end up with a neuron that responds to a oriented bar
What do cortical columns show
Organization of orientation feature detectors in V1
For each location in visual field, for each eye: detectors for all orientations
What is a cortical column
unit of cells dedicated to processing one location of the visual field that processes all orientation of lines in the right and left eye
How are the cortical columns organized
Organized by eye (ocular dominance columns) and by orientation (orientation columns shown in colours)
What are blobs
bundles of cells doing other thing
Where are the more complex feature detectors that detect oriented lines of a specific length found
V2
Where are neurons found that respond to Corners
V4
Where are shapes processed (not exact location)
Farther up the visual pathway from V4
What part of the visual system processes color and aspects of shape
V4
What part of the visual system processes motion
V5/MT
Modularity of auditory hierarchy
Primary auditory cortex = A1 = Core
Secondary auditory cortex = A2 = Belt
Tertiary auditory cortex = auditory association cortex = Parabelt (PB), etc…
Multimodal association cortex = T2/T3, PP, etc…
What are the function of directional feature detectors in the superior colliculus
specialized cells that calculate where sound is coming from
They each respond to sound in a certain direction
Function of auditory directional feature detectors
Detect if sound is arriving in or out of phase to the ears and uses the difference in phase to determine where the sound is coming from
Sound arriving at ears is out of phase when distance from sound source to ear differs. Size of this difference, interaural time delay (ITD), determines horizontal location of sound source
What is the interaural time delay (ITD)
Size of the difference between the phase determines horizontal location of sound source
At what time does sound arrives at the ears if it is coming from straight in front?
same time
Auditory directional feature detectors and coincidence detectors explain
Coincidence detectors in the auditory cortex only fire when they are getting both inputs at the same time
Brain can figure out where the sound is coming from depending on which coincidence detector fires
Modularity of hierarchy in somatosensory system
Primary somatosensory cortex = S1= BA 1, 2, & 3
Secondary somatosensory cortex = S2 = PV
Tertiary somatosensory cortex = somatosensory association cortex = BA 5, MIP, AIP, etc…
Multimodal association cortex = VIP, etc…
Location of orientation feature detectors for somatosensory system
S2
Orientation feature detectors for somatosensory system function
Responds most strongly to specific angle of a bar on skin
How to build a orientation feature detector for somatosensory system
Taking 3 simple receptive fields we built a more complex receptive field for an orientation feature detector → larger and more specifc
What are somatosensory motion detectors and what are the three types
More complex feature detectors in somatosensory system
Motion-sensitive neurons: Respond to any motion in receptive field → all 4 axis
Orientation-sensitive neurons: Respond to motion along a particular axis
Direction-sensitive neurons: Respond to motion in a particular direction
What stream: pathway
Dorsal pathway: occipital lobe into parietal lobe (vision)
Where stream: pathway
Ventral pathway: occipital lobe into temporal lobe (vision)
Where (and How) stream function
Emphasis on location and motion → where things things are in the world and how to interact with them
Processing for action → need to know where the pen is to grab it
What (and why) stream function
Emphasis on shape and color
Processing for object recognition
Identifying what something is helps us understand why we want to interact with it
Visual what stream path
V1 into the temporal lobe through V4
What stream is involved in face sensitive cells in fusiform face area
Ventral what pathway
What does the fusiform face area respond best to
responds most strongly to faces of its own species but still fires to other faces
Visual where stream location
In intraparietal sulcus from the occipital lobe
Parts of the intraparietal sulcus
Anterior (AIP)
Medial (MIP)
Lateral (LIP)
Ventral (VIP)
Function of Anterior (AIP)
Represents space for hand movements → where something is relative to our hand
Function of Medial (MIP)
Represents space for arm movements → where something is relative to our arm
Function of Lateral (LIP)
Represents space for eye movements → where something is relative to where the eye is located
Function of Ventral (VIP
Represents space for facial movements → represent where things are relative to the face
What is the ventral what stream important for
Shape and colour
What is the dorsal where stream important for
motion
Auditory what and where pathways and function
Up joins into parietal where stream
Down that joins the temporal what stream
What we hear helps us identify where something is and what it is
Somatosensory what and where streams and function
Some output goes to the ventral temporal regions –> what
How something feels can help us identify what it is
Some output goes up to the dorsal where stream
If we feel something crawling up our leg we want to know where it is
Does perception depend on bottom up or top down processing
both
Bottom up processing facts
Stimulus driven
Feedforward connections → lower levels to higher levels
Stimulus to higher and more sophisticated levels if processing
Depends on proximal stimulus and genetic “hard-wiring” of sensory systems
Top down processing facts
Driven by goals and expectations
Feedback connections → higher level to lower levels
Depends on past experience, internal state, environmental context
Can have a strong effect on how we perceive the world
How bottom up processing would determine we are looking at a horse
Raw visual input to colour, orientation, movement ect. → combined to determine object → that we are looking at a horse
How we would interpret a blob using top down processing
We entered what the blob is based on our experience or the context
What is the likelyhood principle and is it related to bottom up of top down processing
We perceive the world in a way that is “most likely” based on our past experiences
top down
What does the interactive adaptation model show and how does it work
How top-down and bottom up work together
Used artificial neural network to explain the word superiority effect
Model of letter and word perception
Word superiority effect explanation
The word condition had the fastest and most accurate responses
In the word condition the features of the D send activation to the letter D →WORD is being activated by the D, W, O, R → WORD causes further activation of the D (top-down) → Letter D is perceived more quickly in the context of a word –> more activation of the letter D
In the letter condition the features of the D send activation to the letter D → D is activated –> no top down
Who came up with the interactive adaption model
McClelland and Rumelhart
