% fMRI impulse response function from "Detection versus Estimation in
% Event-Related fMRI: Choosing the Optimal Stimulus Timing," R. Birn,
% R. Cox, and P. Bandettini, NeuroImage 15, pp. 252-264 (2002).
%
% this is equation (1) from that paper.  It gives max height of ~1.000
%
% Example: Return impulse response at t=3.5sec after impulse
%  birnImpulse(3.5)
%

% History: 
%   Tom M. created July 1, 2002
%

function[rslt] = birnImpulse(t)
  global A
  A=1.0/111.8;
  rslt= A .* t.^8.60 .* exp(-t./0.547);