measuring perception Flashcards
Perception
the way we interpret stimuli
what sense do we have
- sight
- taste
- touch
- smell
- pain
- temperature
- balance
- proprioception
joahannes Muller (1801-1858)
doctrine of specific nerve energies: the nature of a sensation depends on which neurons are active and now one how the neurons are stimulated
Charles Sherrington
- 1857 - 1952
- neurons are not physically connected but work in networks
wilder penfield
- 1891- 1976
- stimulating neurons in certain regions of the brain lead to patients feeling sensations of touches on their body
Horace barlow
- 1921-
- neuron doctrine: perception depends on a combination of specialized neurons, each selective for a particular stimulus attribute
brain modularity
the human mind and brain has a set of distinct modules which each carry out one or more specific functions
- sensory modalities have primary receiving areas
polysensory
some area of the brain take in information from several senses combined
Herman von helmholtz
- 1821 - 1894
- invented the opthalmoscope which lets you look at back of eyeball
- said that behavior was explained by only physical forces
Santiago Ramon y cajal
- 1852- 1934
- created first detailed drawing of neurons
- discovered the synapse
action potential
electrochemical signal that travels through the neuron
membrane potential
difference in electrical potential across the cell membrane due to differences in concetration of ions in and out of the cell
resting potential
the membrane potential when a neuron is at rest (-70mV)
firing rate
the rate at which a neuron produces action potentials
- expressed in terms of action potentials (spikes) per second
baseline firing rate
a neurons low rate of spontaneous firing at failry random intervals in the absence of any stimulus
- a stimulus must reach a minimun level of intensity to ivoke a firing rate above the baseline rate
refractory period
- after an action potential, there is brief period during which no new action potential can be initiated
- its an upper limit to the action potentials per second we can perceive
distal stimulus
the small subset of stimuli that we attend to
- aka attended stimulus
top down knowledge
- existing knowledge
- knowledge, expectaton and goals which can affect perception
bottom up information
information contained in neural signals from receptors
functional neuroimaging
an array of techniques used for measuring brain activity in healthy volunteers carrying out cerefully designed tasks
EEG
using many electrodes on the scalp, it measures electrical activity from populations of many neurons in the brain
- good temporal resolution but low spatial resolution
- based on electrical fields associated with brain activity
Event related potential
a measure of electrical activity from a subpopulation of neurons in response to particular stimuli that require averaging manu EEG recordings
visually evoked potentials (VEp)
a measure of electrical activity from a sub population of visual neurons in response to a visual stimulus
MEG
a technique similar to EEG that measures changes in magnetic activity across populations of many neurons in the brain
- good temporal but low spatial
PET
- measures changes in blood flow which measure underlying neural activity
- uses an introduction of radioactive substance into the blood
fMRI
functional neuroimaging technique based on a measurement of the changes in blood oxygenation associated with brain activity.
- it relies on production of magnetic fields in the brain
- high spatial resolution but low temporal
CT
- brain imaging technique
- uses x-rays to create images of slices
MRI
- brain imaging technique that uses the response of atoms to strong magnetic fields to form images of structures like the brain
- good spatial precision
FNIRS
- look at blood flow changing at thr surface
- shines an infared light inside through scalp to see how much blood is being used in areas of cortex
- cant detect things deep in brain but good temporal resolution
Gustav Fechner
invented psychophysics
- 1801-1887
psychophysics
science of defining quantitative relationships between physical and psychological (subjective) events
Absolute threshold
minimum amount of stimulation necessary for a person to detect a stimulus 50% of the time
method of adjustment
a psychophysical method where a participants observes a stimulus and manipulates a control that directly adjust the intensity until it cannot be detected
- quick and dirty - simple (less accurate)
method of constant stimuli
psychophysical method where a participant is repeatedly presented with a fixed set of stimuli in random order and they must indicate whether or not each one was detected
- simple and accurate but not efficient
staircase method
psychophysical method where participant is presented with a stimulus and indicates whether it was detectedand based on that the next stimuli will be a step up or down from that
- efficient
- more accurate than adjustment
Just noticeable difference
the minimum difference between two stimuli that allows an observer to perceive that the two stimuli are different
- involves comparing two stimuli
- a steep function represents a small JND
Weber’s law
a statement of the relationship between the intensity of a standard stimulus and the size of the JND
- JND=kl
psychophysical scaling
the process of measuring how changes in stimulus intensity relate to changes in perceived intensity
Fechner’s law
a variant of weber’s law that describes the relationship between the perceived intensity of a stimulus as it changes in cmparsion to the natural log ratio of the physical intensity
- S=klnl/lo
Steven’s law
- webr’s law was good for brightness and loudness but it didn’t account for other’s like electric shock and line length
- S=cl^n
- power law
Signal detection theory
a psychophysical theory that distinguishes between the ability to detect a stimuus and the willingness to report it.
- considers the decision making process of people
outcomes of a signal detection experiment
- hit: correct response
- miss: didnt hear present stimulus
- false alarm: not really there but heard
- correct rejection
receiver operating characteristic (ROC)
the plot of the hit rate as a function of the false alarm rate.
- different stimuli have different ROCs
noise
random variation in the neural code
chance performnce
- 45 degree line that is refer to when false alarm = hit rate
sensitivity
- the value that defines the eae with which a observer can tell whether a stimulus is there or not or the JND
criterion
an internal threshold set by the observer.
- includes their bias
