methods Flashcards
two categories of performance measures
performance outcome measures (relates to motor skills)
performance production measures (relates to movement components)
types of movement error
constant error and variable error
constant error
provides the amount and direction of deviation from the target
problem: does not consider amount of scatter/variability of error
CE= sum(Xi-T)/n
Xi is score on trial i, T is the target position and n is the number of trials
used for discrete skills
variable error
measures the inconsistency or variability in the movement outcome
basically the standard deviation of CE
CE and VE are often reported together
VE= sqr sum (Xi-M)^2/n
where Xi is the score on tiral i, M is the subject’s average movement, and n is the # of trials performed
used for discrete skills
root-mean-square error (RMSE)
measure of overall error
gives an indication of the amount of spread of the movement across the duration of the trial/performance
used for continuous skills like in pursuit tracking
RMSE= sqr sun (Xi-Ti)^2/n
where Xi is the effector position at time point i, Ti is the target position at time point i, and n is the # of time points of the movement
root mean square
quantifies the magnitude of a signal or set of data
x(RMS) = sqr 1/N sum (absolute value Xn)^2
where X is the value of a signal or set of data at a specific point in time, and N is the number of data points
gets the sense of magnitude when an average might be misleading
reaction time
time between the onset of a stimulus and onset of a response
can be based on the onset of a movement or some othjer variable such as the onset of muscle activity
there is usually some delay between muscle activity and onset and a measurable movement of the body. motor RT is this delay period
simple-RT tasks
only one choice available
choice-RT tasks
multiple response choices are available and/or multiple stimuli may be presented
movement time
interval between the initiation of the response to the completion of the movement
response time
sum of reaction time and movement time
premotor RT
time for central processing
force plates
used to measure kinetic data
embedded in the floor, set of stairs, or on a moveable platform
used to determine how fast and hard a person loads a surface
can be used to measure the center of pressure
ie/ forces that causes movement
motion capture cameras
used to quantify kinematic data
- describes movement, independent of forces that cause the movement
- includes linear and angular displacements, velocities and accelerations
often used to quantify movement for designing videogames and creating movines
ie/ walking or reaching movements
electromyography (EMG)
used to record electrical activity from muscles
eye tracking
head mounted mobile systems used to monitor eye movements
neuroimaging, neurostimulation and neural recording equiptment
used to study nervous system activity and function (related to movement)
posturography
used to assess standing balance - usually uses a force plate
in this test support surface and/or visual surround can move
the manipulations across the six conditions create different conflicts between sensory informations
microneurography
recording nerves
a technique to record electrical activity of single axons within a nerve (to determine activity of an individual sensory receptor)
a thin microelectrode is passed through the skin, into the nerve and then into one of the nerve fascicles
within a fascicle, small adjustments are made, placing the electrode tip next to one or more axon sheaths
single neuron recording
improvements in the ability to amplify very small electrical signals and smaller electrode led to the ability to measure and record the activity of single neurons by 1920s
allowed for first studies of receptive fields and later tuning curves
the ability to isolate the activity of a single neuron is a powerful way to study how info is processed by the nervous system
requires an electrode in the brain within 50-150 um of neurons as well as cell sorting
extracellular recording
extracellular recording
measuring changes in voltge from outside f the cell membrane
microneurography
same technique as single neuron recording but applied to peripheral nerves, using similar electrodes and cell sorting techniques
awake studies
allow for studying how brain function relates to behaviour but requires electrodes and/or other hardware to be implanted on the head
cell sorting
a microelectrode will record all cells within around 100um
- each cell will have a slightly different waveform that must be isolated from the others
typically, of the dozens of neurons close enough for an electrode to hear, only a few have signals strong enough to be isolated and studied as individual cells
figure shows spikes from 4 cells that are different enough from each other and the background activity of many cells to be isolated.
similarily to action potential profile
labelled line theory
sensory info comes from different modalities and is transmitted to the brain via different pathways or labelled lines
electrical microstimulation
using similar or identical electrodes in the brain, it is possible to pass electric current to local neurons (instead of recording the current generated by neurons)
this can evoke APs in multiple neurons near the tip of the stimulating electrode.
these artifically generated spikes then activate other neurons through natural brain circuitry
regios like motor muscle contractions from different parts of the cortical area
stimulation of different parts of the hypothalamus can evoke feeding behaviour or stimulate the euphoric high of illicit drugs; stimulation of sensory areas can alter perception
stimulation vs recording
neural recordings provide information about function but does not alter neural function
electrical stimulation via electrodes in the brain seeks to manipulate neural activity (it does not record it)
fMRI
functional magnetic resonance imaging
a method used to visualize the activity of the brain
brain activity causes local changes in blood flow
fMRI measures the magnetic disturbance between oxygen rich and oxygen poor blood due to changes in neural activity
requires large and expensive equiptment
MEG
magnetoencephalography.
measures the very weak magnetic fields generated by the brain’s electrical activity
detects magnetic activity produced by thousands of neurons at a time
requires large and very expensive equiptment
EEG
electroencephalography
an array of scalp electrodes that record the electrical activity of the brain
signals come mainly from the cortex
uses comparatively cheaper equiptment
TMS
transcranial magnetic stimulation
noninvasive
stimulates the brain through the scalp
doesn’t hurt, you do not feel much - light flick of the head
a stimulation coil is placed on the head and generates a magnetic field
the magnetic field induces an electric current in the brain, which causes activation of axons of neurons
if you place the coil’s centre over the hand region of the motor cortex, you can activate the muscles in the hand
when doing this you generated a motor evoke potential (MEP), which is recorded by an EMG
MEP
motor evoked potential
the electrical activity from the muscle
the size of it can provide info about a variety of thingd
what can TMS used for
map connectivity in the cortex
- stimulate one region and see what other regions are activated
map excitability of the cortex
- the excitability can be quantified by the size of MEP
can cause virtual lesions to investigate function of a region
- certain stimulation parameters can temporarily disrupt a brain region, kind of like a very brief and temporary stroke. this is tested by measuring how TMS interferes with specific tasks
assess plasticity and recovery of function
- this can be assessed using the size of a MEP
rehabilitate motor function
- using a repetitive stimulation technique, you can facilitate activation of a brain region to make it more plastic
what are the types of tES (transcranial electrical stimulation)
transcranial direct current stimulation (tDCS)
transcranial alternating current stimulation (tACS)
transcranial random noise stimulation (tRNS)
these techniques use two or more electrodes on the scale to conduct electrical current to the brain
non invasive
anode
electrode
where current enters brain
cathode
electrode
current exits brain and flows to cathode
anodal stimulation
anode placed over brain area trying to modify
cathodal stimulation
cathod placed over brain area trying to modify
what does rES do
changes membrane potential (so brain region is more or less likely to activate
- different from TMS which activates neurons
effects can last approx 90 mins depending on stimulation parameters and brain site
