How do devices measure continuous biological events
Devices sample at intervals and connect the dots
Fundamentals of digital bio recording
- amplifying the signal
- filtering noise
- selecting appropriate sampling rate
Types of digital bio recording amplifiers
- input amplifiers
- bio-amplifiers
- bridge amplifiers
Input amplifiers
Don’t do much
Bio amplifiers
- safe for use on humans
- amplify small signals
What is wrong with raw data
Has too much noise
Appropriate filter
50Hz low pass filter
- everything below 50Hz is kept
What is the significance of 50 Hz in filtering
The frequency emitted by technology
Issues with 10Hz low pass filters
Excessive filtering
- crops peaks of biological data
50Hz high pass filter
Only allows >50Hz
- leaves only noise, no waveform of interest
Why does sampling rate matter
Needs to be fast enough to catch important events
- higher rate = higher quality
High sampling rate
1k/sec
Low sampling rate
4/sec
P100
Stereotypical waveform representing average latency (100ms) for a visual evoked potential
Why is there a delay between stimuli and response
- phototransduction at eye level
- signal transmission
- synapses
Latency
Time between stimulus and response
Left tail (stats)
Smaller than mean
Right tail (stats)
Larger than mean
SD
Standard variation from the mean in the data
P significance
P<0.05 significant
P>0.05 insignificant
P<0.05 meaning
There is less that 0.05% chance that the data sets are the same
Paired t -test
Same group before and after intervention
Unpaired t-test
Comparison between two different groups
Chart mode use
Used to record continuous events, where changes in the parameter of interest occur relatively slowly and over relatively long time periods
