Functions

Read SSR from file or IO stream

Read a file or IO stream and store the data in an SSR type.

Matching .mat files are read and modulation frequency information extracted. Failing that, user passed arguments are used or the modulation frequency is extracted from the file name.

Arguments

• fname: Name of the file to be read
• min_epoch_length: Minimum epoch length in samples. Shorter epochs will be removed (0)
• max_epoch_length: Maximum epoch length in samples. Longer epochs will be removed (0 = all)
• valid_triggers: Triggers that are considered valid, others are removed ([1,2])
• stimulation_amplitude: Amplitude of stimulation (NaN)
• modulationrate: Modulation frequency of SSR stimulation (NaN)
• carrier_frequency: Carrier frequency (NaN)
• participant_name: Name of participant ("")
• remove_first: Number of epochs to be removed from start of recording (0)
• max_epochs: Maximum number of epochs to retain (0 = all)
• env (nothing)
• bkt ("")

Supported file formats

• BIOSEMI (.bdf)

filter_highpass(a::SSR; cutOff::Real=2, fs::Real=samplingrate(a), order::Int=3, tolerance::Real=0.01, kwargs...)

Applly a high pass filter.

A zero phase high pass filter is applied to the data using filtfilt. A check is performed to ensure the filter does not affect the modulation rate. The filter coefficents are stored in the processing field.

Examples

a = read_SSR(fname)
b = filter_highpass(a)
c = filter_highpass(a, cutOff = 1)

filter_lowpass(a::SSR; cutOff::Real=150, fs::Real=samplingrate(a), order::Int=3, tolerance::Real=0.01, kwargs...)

Applly a low pass filter.

A zero phase high pass filter is applied to the data using filtfilt. A check is performed to ensure the filter does not affect the modulation rate. The filter coefficents are stored in the processing field.

Examples

a = read_SSR(fname)
b = filter_lowpass(a)
c = filter_lowpass(a, cutOff = 1)

filter_bandpass(a::SSR; lower::Number=modulationrate(a) - 1, upper::Number=modulationrate(a) + 1, fs::Real=samplingrate(a), n::Int=24, rp::Number = 0.0001, tolerance::Real=0.01, kwargs...)

Applly a band pass filter. A check is performed to ensure the filter does not affect the modulation rate. The filter coefficents are stored in the processing field.

Examples

a = read_SSR(fname)
a = filter_bandpass(a)

downsample(s::SSR, ratio::Rational)

Downsample signal by specified ratio.

function extract_epochs(a::SSR; valid_triggers::Union{AbstractArray,Int} = [1, 2], remove_first::Int = 0, remove_last::Int = 0, kwargs...)

Extract epoch data from SSR

Arguments

• a: A SSR object
• valid_triggers: Trigger numbers that are considered valid ([1,2])
• remove_first: Remove the first n triggers (0)
• remove_last: Remove the last n triggers (0)

Examples

epochs = extract_epochs(SSR, valid_triggers=[1,2])

ftest(s::SSR)
ftest(s::SSR; kwargs...)

Run f-test statistics on steady state response measurement.

Arguments

• freq_of_interest: Frequency to analyse for presence of a response
• side_freq: Adjacent frequencies above and below the frequency of interest used to quantify the noise
• ID: Participant ID for storage in resulting dataframe
• spill_bins: Number of bins each side of the FFT bin of interes to ignore in noise computation
• results_key: Dictionary key name to store results in s.processing

Examples

s = read_SSR(fname)
s.modulationrate = 33.2u"Hz"
s = ftest(s)
println(s.processing['statistics'])

Reference

Hofmann, M., Wouters, J. Improved Electrically Evoked Auditory Steady-State Response Thresholds in Humans. JARO 13, 573–589 (2012). https://doi.org/10.1007/s10162-012-0321-8

Luke, Robert, and Jan Wouters. "Kalman filter based estimation of auditory steady state response parameters." IEEE Transactions on Neural Systems and Rehabilitation Engineering 25.3 (2016): 196-204.

plot_spectrum(eeg::SSR, chan::Int; kwargs...)
plot_spectrum(eeg::SSR, chan::AbstractString; kwargs...)

Plot the spectrum of a steady state response measurement.