algorithms.event_related

Module: algorithms.event_related

Event-related analysis

Functions

nitime.algorithms.event_related.fir(timeseries, design)

Calculate the FIR (finite impulse response) HRF, according to [Burock2000]

Parameters:

timeseries : float array

timeseries data

design : int array

This is a design matrix. It has to have shape = (number of TRS, number of conditions * length of HRF)

The form of the matrix is:

A B C …

where A is a (number of TRs) x (length of HRF) matrix with a unity matrix placed with its top left corner placed in each TR in which event of type A occurred in the design. B is the equivalent for events of type B, etc.

Returns:

HRF: float array :

HRF is a numpy array of 1X(length of HRF * number of conditions) with the HRFs for the different conditions concatenated. This is an estimate of the linear filters between the time-series and the events described in design.

Notes

Implements equation 4 in Burock(2000):

\[\hat{h} = (X^T X)^{-1} X^T y\]

M.A. Burock and A.M.Dale (2000). Estimation and Detection of Event-Related fMRI Signals with Temporally Correlated Noise: A Statistically Efficient and Unbiased Approach. Human Brain Mapping, 11:249-260

nitime.algorithms.event_related.freq_domain_xcorr(tseries, events, t_before, t_after, Fs=1)

Calculates the event related timeseries, using a cross-correlation in the frequency domain.

Parameters:

tseries: float array :

Time series data with time as the last dimension

events: float array :

An array with time-resolved events, at the same sampling rate as tseries

t_before: float :

Time before the event to include

t_after: float :

Time after the event to include

Fs: float :

Sampling rate of the time-series (in Hz)

Returns:

xcorr: float array :

The correlation function between the tseries and the events. Can be interperted as a linear filter from events to responses (the time-series) of an LTI.

nitime.algorithms.event_related.freq_domain_xcorr_zscored(tseries, events, t_before, t_after, Fs=1)

Calculates the z-scored event related timeseries, using a cross-correlation in the frequency domain.

Parameters:

tseries: float array :

Time series data with time as the last dimension

events: float array :

An array with time-resolved events, at the same sampling rate as tseries

t_before: float :

Time before the event to include

t_after: float :

Time after the event to include

Fs: float :

Sampling rate of the time-series (in Hz)

Returns:

xcorr: float array :

The correlation function between the tseries and the events. Can be interperted as a linear filter from events to responses (the time-series) of an LTI. Because it is normalized to its own mean and variance, it can be interperted as measuring statistical significance relative to all time-shifted versions of the events.