The brain is constantly challenged to decide between integrating or segregating multiple sensory signals. For instance, at a busy party, we should integrate the facial movements of the speaker we are listening to with the speech he produces whilst ignoring other voices. Despite its importance for many daily situations, little is known about how the brain computes this decision. This multidisciplinary proposal combines psychophysics, Bayesian Causal Inference, EEG/MEG and concurrent EEG-fMRI to characterise the computational operations and neural mechanisms for arbitrating dynamically between multisensory information integration and segregation. In particular, we will probe the role of phase resetting, alpha oscillations and cross-regional neural coherence.
First, we will investigate how the brain utilises multiple bottom-up correspondences such as audiovisual synchrony and motion congruency. Second, we will investigate how multisensory integration is jointly shaped by top-down prior congruency expectations and bottom-up sensory correspondences. We expect that temporal synchrony is critical for mechanisms of phase resetting, while dynamic motion congruency that becomes only later available may be more clearly sustained by inter-regional coherence. Oscillatory alpha activity will play a key role in top-down influences of prior congruency expectations. Using simultaneous EEG-fMRI, we will investigate how the multisensory network is modulated dynamically by alpha power in visual cortices on a trial-by-trial basis.
Collectively, this proposal will significantly advance our understanding of the neural and computational mechanisms underlying information integration and segregation, one of the brain’s most fundamental capacities. It will also provide critical tests for influential theories of oscillatory activity. he research outcome will have important implications for translational fields such as cognitive decline in ageing, robotics and performance enhancing technology.
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