Detecting latency differences in event-related BOLD responses: application to words versus nonwords and initial versus repeated face presentations.
We introduce a new method for detecting differences in the latency of blood oxygenation level-dependent (BOLD) responses to brief events within the context of the General Linear Model. Using a first-order Taylor approximation in terms of the temporal derivative of a canonical hemodynamic response function, statistical parametric maps of differential latencies were estimated via the ratio of derivative to canonical parameter estimates. This method was applied to two example datasets: comparison of words versus nonwords in a lexical decision task and initial versus repeated presentations of faces in a fame-judgment task. Tests across subjects revealed both magnitude and latency differences within several brain regions. This approach offers a computationally efficient means of detecting BOLD latency differences over the whole brain. Precise characterization of the hemodynamic latency and its interpretation in terms of underlying neural differences remain problematic, however.
Henson
R N A
RN
Wellcome Department of Cognitive Neurology, Institute of Cognitive Neuroscience, University College London, Queen Square, London WC1N 3BG, United Kingdom. r.henson@ucl.ac.uk
Price
C J
CJ
Rugg
M D
MD
Turner
R
R
Friston
K J
KJ
D000328:Adult; D001921:Brain / Q000098:blood supply / Q000502:physiology*; D002540:Cerebral Cortex / Q000098:blood supply; D003657:Decision Making / Q000502:physiology; D004193:Discrimination Learning / Q000502:physiology; D005145:Face; D005260:Female; D006801:Humans; D007089:Image Enhancement; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology*; D010364:Pattern Recognition, Visual / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology*; D011932:Reading; D012039:Regional Blood Flow / Q000502:physiology; D012660:Semantics