Abstract #2342

Trial-By-Trial Global Modulation of BOLD Responses to Simple, Sensory Stimuli: Implications for Functional Brain Imaging and Understanding Positive and Negative BOLD Response Coupling

Stephen D. Mayhew¹, Karen J. Mullinger², Camillo Porcaro³,⁴, Richard W. Bowtell², Andrew P. Bagshaw¹, Susan T. Francis²

¹BUIC, School of Psychology, University of Birmingham, Birmingham, United Kingdom; ²SPMMRC, School of Physics and Astronomy, University of Nottingham, Nottingham, United Kingdom; ³Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, United Kingdom; ⁴LETs-ISTC-CNR, Fatebenefratelli Hospital-Isola Tiberina, Rome, Italy

Conventional GLM analyses of fMRI data localise brain activity from the average stimulus response, ignoring trial-by-trial variability which is most relevant to the dynamics of brain function and behavioural outcomes. We combine data from visual, motor and somatosensory tasks to show that single-trial responses across the whole brain are concurrently modulated with activity in the stimulated primary sensory cortex. These modulations induce a positive correlation between single-trial positive and negative BOLD responses, despite a negative correlation between the average response magnitudes. These findings demonstrate that stimulus modulations extend over a far greater extent of the brain than previously suspected.