Ð52Ð
Basis
Function: ÒSticksÓ
¥ The set of basis functions you use determines the range of possible HRFs
that you can compute
¥ ÒStickÓ (or Dirac delta) functions are very flexible
H But they come with a strict
limitation
¥ d(t
) is 1 at t=0 and is 0 at all other values of t
¥ yq(t ) = d(t
Ðq×TR) for q=0,1,2,É,p
Þ h(0) 
= b0
= b0Þ h(TR) =
b1
=
b1Þ h(2 ×TR) =
b2
=
b2Þ h(3 ×TR) =
b3
=
b3Þ et
cetera
Þ h(t ) = 0 for any t not on the TR grid
time
h
t=0
t=TR
t=2×TR
t=3×TR
t=4×TR
t=5×TR
Each
piece of h(t ) looks like
a stick poking up