Sensation and Perception Exam 1

Sensation

• receiving stimulus

• ability to detect the stimulus

• reliant on the receptors that are used to detect the stimuli

Perception

• what you do with it

• our conscious interpretation of that data

• conscious experience and interpretation

sensation doesn’t always = perception

true

7 steps of perceptual process

1. stimulus in the environment (distal stimulus)

2. stimulus hits the receptor (proximal stimulus)

3. receptor processes

4. neural processes

5. perception

6. recognition

7. action

Step 1: stimulus in the environment (distal stimulus)

• the clock on the all

  • distal = distance

Step 2: stimulus hits the receptor (proximal stimulus)

what interacts with the receptor is the light image that reflects off the clock on the wall that hits the receptors in the eyes

Step 3: receptor processes

• transduction

• principle of transformation

• principle of representation

transduction

• the key thing that receptor does

• taking the environmental energy and turning it into electrical energy

• process that happens in all our sensory receptors

  • this matters because our nervous center relies on electrical energy to transform information

principle of transformation

stimuli and responses created by the stimuli are changed from distal stimulus to perception

principle of representation

person perceives stimulus based not on direct contact with stimuli but instead representations of stimuli that are formed on receptors

Step 4: neural processes

person perceives stimulus based not on direct contact with stimuli but instead representations of stimuli that are formed on receptors

steps 5-7 are ____ _____ that we can measure

behavioral processes

Step 5: perception

• our conscious experience

• perception does not require that we have a name for it

Step 6: recognition

ability to place object in a category that gives it meaning

Step 7: Action

behavioral responses

important for process

knowledge, memory, expectations, and attention

3 types of relationships

• stimulus-behavior relationship

• stimulus-physiology relationship

• physiology-behavior relationship

stimulus-behavior relationship

researchers manipulate stimuli and we measure behavior

stimulus-physiology relationship

measuring the brain

physiology-behavior relationship

the rarest

absolute threshold

smallest stimulus level that can be detected

classical physiological methods to measure absolute threshold

• method of limits

• method of adjustment

• method of constant stimuli

Method of limits

increase or decrease of stimulus intensity until threshold of detection

method of adjusment

participant adjust stimulus intensity continuously until detected

method of constant stimuli

• we present stimuli in random order, and ask if participant can detect it

  • preferred for accuracy (prevents bias) but need more trials

measuring above threshold

• magnitude estimation

• reaction time

• recognition testing

• phenomenological report

magnitude estimation

• participant assigns numbers to stimuli that are proportional to the subjective magnitude of the stimulus

  • like rate your pain on a scale of one to ten

recognition testing

participant names stimuli, “what is the object”

phenomenological report

• participant describes what is perceived

• much more open ended

• giving more details

• it can allow for a much more holistic description of the perceptual experience

difference threshold

• the minimum difference that must exist between two stimuli before a difference can be detected between them

  • weber fractions can be used

Weber fractions

• lifted weight - 2% difference needed to detect one is heavier than the other

• sound intensity - 4%

• light intensity - 8%

magnitude estimation

• if i double the intensity of a stimulus what do i perceive

response compression

• the result when doubling the physical intensity of a stimulus less than doubles the subjective magnitude

  • i.e. brightness of light

  • received as brighter but not twice as bright

response expansion

• the result when doubling the physical intensity of a stimulus more than doubles the subjective magnitude of the stimulus

  • i.e. electric shock

signal detection experiment differs from classical psychophysical experiments in 2 ways:

• only one stimulus intensity presented and it is a low intensity

• on some trials no stimulus is presented

possible responses to a trial for signal detection approach

• hit - correctly says “yes” when there is a stimulus

• miss - incorrectly says “no” when there is a stimulus

• false alarm - incorrectly says “yes” when there was no stimulus

• correct rejection - correctly says “no” when there is no stimulus

conservative responder

will say “yes” less often than a liberal responder

liberal criterion

high false alarm rate and very high rate

neutral criterion

low false alarm rate and high hit rate

conservative criterion

very low false alarm and also a low hit rate

what is an action potential

• when a neuron fires

  • sudden depolarization of the neuron

parts of the neuron

dendrites, cell body (soma), axon, axon terminal, axon hillock

dendrites

have receptors on cell membrane, receives inputs

excitatory inputs

more likely to happen

inhibited inputs

less likely to happen

cell body or soma

has nucleus

Axon

full length of the neuron, where an action potential happens

Axon terminal

the end of axon that releases neurotransmitters

Axon hillock

point where axon meets cell body, summation matters here for action potential

resting potential

• the difference between inside and outside of the neuron cell membrane at “rest"

  • about -70mV

  • maintained by sodium-potassium pump

sodium potassium pump

uses energy to move ions where they dont want to be, creating an in-balance that creates the -70mV

Action potential

sudden depolarization of the neuron’s cell membrane that allows communication over long distances

depolarization to threshold

• at threshold the voltage-gated sodium ion channels can open - let sodium ions flow down concentration gradient

• must depolarize to threshold for action potential

all-or-none law

an action potential happens or it doesn’t happen

synaptic transmission

two neurons communicating

synapse

connection between two neurons

presynaptic neuron

neuron sending the signal by releasing neuro transmitters

post synaptic neuron

receives the input

sensory coding

how neurons represent various characteristics of the environment

population coding

particular object or quality is represented by the pattern of firing of a large number of neurons

sparse coding

particular object or quality is represented by the firing of a relatively small number of neurons

specificity coding

perception signal by activity in a specific neuron

• grandmother neuron

localization of function =

modularity of the brain

measuring structure of the brain

• CT

• structural MRI - magnetic resonance imaging (MRI)

measuring brain activity directly

• EEG

• ECoG

EEG (electroencephalography)

electrodes on scalp, noninvasive, good temporal resolution, poor spatial resolution

ECoG (electrocorticography)

electrode fridge on the brain surface, invasive, good temporal and spatial resolution where the grid is placed

measuring brain activity indirectly with a correlate of brain activity

functional MRI (fMRI)

Functional MRI (fMRI)

• way for us to quantify changes in oxygenation levels in blood and changes in blood flow

• good spatial resolution, poor temporal resolution, noninvasive

• identify area involved in a function

lesion method

study patients with focal brain injury and the changes in cognition/behavior

• can identify areas necessary for a function

Somatosensory system

focus on cutaneous sense of touch and pain

proprioception

body position, information that is not visually dependent

kinesthesis

body movement

Sensory relay

all of our sensory systems have a stop in the thalamus

touch receptors

mechanoreceptors, in the skin movements cause them to work, 4 types

4 types of touch receptors

Merkel receptor, Meissner corpuscle, Ruffini cylinder, pacinian corpuscle

Merkel receptor

• slow adapting fiber (SA1)

• collects fine detail information

• small receptive field

Meissner corpuscle

• rapidly adapting fiber (RA1)

• collects information for perceiving tactile slip and control grip force

• small receptive field

Ruffini cylinder

• slow adapting fiber (SA2)

• stretching of the skin

• large receptive field

Pacinian corpuscle

• rapidly adapting fiber (RA2)

• fine texture anad rapid vibrations

• large receptive field

Touch pathways

Dorsal column medical lemniscus (DCML) pathway

DCML pathway

touch receptors → to the medulla → VPL thalamus → S1 (primary receiving area)

Primary somatosensory cortex (S1)

• in the parietal lobe

• organization

  • lateralization - opposite side of body - left S1 gets right body info

  • localization - specific area for specific body parts

  • cortical magnification

• crosses the midline after the medulla and before the thalamus

Cortical magnification

• in the cortex there is a disproportionate allocation of space

  • more area for hand and face

• sensory homunculus

two types of touch

active and passive

active touch

active exploration of object, usually with hands

passive touch

• touch stimuli applied to skin without exploration

  • i.e. pencil placed in your fla hand

haptic perception

perception of 3D object but touch

• relies on 3 systems working together

  • sensory system

  • motor system

  • cognitive system

exploratory procedures (EPs)

distinctive movements that are used to identify objects with haptic exploration