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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.