fmri.cluster {fmri}

Cluster thresholding.

Description

Detection of activated regions using cluster thresholding.

Usage

fmri.cluster(spm, alpha = 0.05, ncmin = 2, ncmax=ncmin, 
             minimum.signal = 0, verbose = FALSE)

Arguments

spm

fmrispm object

alpha

multiple test (over volume and cluster sizes) adjusted significance level used for thresholds.

ncmin

minimal cluster size used. An activation is detected if for any clustersize in nvmin:20 the size specific threshold is exceeded.

ncmax

maximal cluster size used. An activation is detected if for any clustersize in ncmin:ncmax the size specific threshold is exceeded.

minimum.signal

allows to specify a (positive) minimum value for detected signals. If minimum.signal >0 the thresholds are to conservative, this case needs further improvements.

verbose

intermediate diagnostics

Details

Approximate thresholds for the existence of a cluster with spm-values exceeding a 1-beta threshold k_{nc,na:ne} for cluster size nc are based on a simulation study under the hypothesis and adjusted for number of voxel in mask and spatial correlation. beta is chosen such that under the hypothesis the combined (over cluster sizes ncmin:ncmax) test has approximate significance level alpha.

Value

Object with class attributes "fmripvalue" and "fmridata"

pvalue

cluster based p-values for voxel that were detected for any cluster size, a value of 1 otherwise.

mask

mask of detected activations

weights

voxelsize ratio

dim

data dimension

hrf

expected BOLD response for contrast (single stimulus only)

Author(s)

Joerg Polzehl [e-mail]

See Also

fmri.lm, fmri.pvalue, fmri.searchlight

Examples

  ## Not run: fmri.cluster(fmrispmobj)