Yes, I think spm_get_bf.m changed across SPM releases since that 2002 paper, such that the C,D parameters need to be updated. The latest people to work on this (to my knowledge) are Donald McLaren, Baerbel Herrnberger and Cyril Pernet, so I will forward you some of their emails to you in a second.
Please note though that this method is "quick and dirty" (really for quick whole-brain search), and there are better ways to estimate latency, eg nonlinear fitting of an HRF explicitly parameterised by amplitude, onset latency, dispersion, etc (eg Henson & Rugg, 2001, HBM Abstract, Neuroimage, 13, 683). These iterative approaches take longer (eg more suitable for ROIs) and benefit further from priors on the parameters (when the event-locked data are noisy) - eg within a PEB framework. And even then, they assume a linear relationship between BOLD latency and underlying neural latency (which is normally the parameter of interest), so better still would be to fit a proper biophysical model such as the Balloon model (see spm_hdm_ui.m), similar to that used for DCM, where neural latency could be a parameter inferred by inversion of the model.
Rik
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Professor Richard Henson
Deputy Director
MRC Cognition and Brain Sciences Unit
University of Cambridge
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England
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-----Original Message-----
From: SPM (Statistical Parametric Mapping) [mailto:[log in to unmask]] On Behalf Of MOUTHON Michael
Sent: 12 February 2018 10:13
To: [log in to unmask]
Subject: [SPM] BOLD latency analysis in SPM12 with Henson 2002
Dear Prof. Henson
I have a question relative to the formula to approximate the BOLD latency in Henson et al 2002 : 2C/(1 + exp(Dβ2/β1)) − C (where C = 1.78, D = 3.10)
In one of your previous post (https://www.jiscmail.ac.uk/cgi-bin/webadmin?A2=ind0911&L=spm&P=R105459&1=spm&9=A&J=on&d=No+Match%3BMatch%3BMatches&z=4) , you tell that McLaren has found a problem in this sigmoidal equation due to SPM update.
I can't found this McLaren post (dead link).
Can you explain me how can I found the correct formula and constants to work with SPM12 (and data recorded on a 3T scanner).
Thank you very much
Michael
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