Report
Teaser, summary, work performed and final results
Periodic Reporting for period 2 - PERCEPT (The mind\'s eye: How expectation and attention shape perception)
Teaser
How we see the world is not simply the result of light falling onto our retinas, but critically shaped by attention (what is relevant) and as a growing body of work indicates, by past experience (what is likely). Overturning the classical notion of perception as a largely...
Summary
How we see the world is not simply the result of light falling onto our retinas, but critically shaped by attention (what is relevant) and as a growing body of work indicates, by past experience (what is likely). Overturning the classical notion of perception as a largely stimulus-driven process, the idea that our brain is a prediction machine, continually trying to predict what is ‘out there’ based on past experience, is quickly growing in stature and influence. Yet, little is still known about how predictions shape perceptual experience. Moreover, it is completely unknown to what extent predictive processing occurs automatically. Lastly, how the brain ultimately ‘decides’ on one hypothesis or interpretation of the current sensory state is still unclear. This project addresses these outstanding questions with the ultimate aim to better understand how the brain infers the world and the mechanisms that give rise to perceptual experience. To this end, it uses an integrated application of psychophysical, neuroimaging, brain stimulation, mathematical modelling, and pharmacological techniques. The research program comprises three subprojects. The first subproject examines how expectations are implemented in the brain and shape stimulus processing, independently from and aided by attention. The second subproject investigates if one can teach oneself to be free of expectation and associated habitual responding, through intensive mental training, as cultivated by meditation. The third subproject tests the idea that the striatum, a subcortical brain region, and its irrigation by the neurotransmitter dopamine play a critical role in updating our internal model about the environment and thereby conscious perception. Findings are expected to shed novel light on the mechanisms that underlie experience and the extent to which these mechanisms are plastic, and will have important implications for the study of clinical disorders characterized by dysfunctional experience of the world.
Work performed
The project is comprised of three subprojects. The objective of the first subproject is to determine how predictions derived from previous experience influence sensory processing and perception, independently from and aided by attention. Results so far indicate that predictions do not influence visual information processing in the brain before 100ms. Effects of predictions are particularly pronounced at later information processing stages, suggesting previous experience primarily facilitates attentional selection and decision making. Moreover, we found that predictions play a particularly important role in helping the brain ignore distracting information. In particular, our findings show that experience with distracting information renders it less distracting to the brain.
The objective of the second subproject is to determine if meditation can reduce the effect of past experience on current experience. Yet, meditation is not one thing. We have developed a theoretical model that formulates predictions as to how different kinds of meditation may influence predictive processing and habitual responding, and are setting up experiments to test these predictions.
The objective of the third subproject is to elucidate the role of the striatum, a subcortical brain region, and its irrigation by the neurotransmitter dopamine in predictive processing and consciousness. Results from a first pharmacological study do not provide evidence that dopamine affects what percept dominates our conscious experience. In addition, we have set up an experiment in patients with obsessive compulsive disorder (OCD) who have deep brain stimulation (DBS) electrodes implanted in the striatum to test how striatal DBS may modulate predictive processing and conscious perception, and developed a predictive processing account of OCD to explain their inability to update their model of the external world based on new experience. Finally, we have suggested a theoretical extension of the most dominant theoretical framework of the predictive brain, the free energy principle.
Final results
Our findings so far go beyond the state of the art by revealing how past experience influences how we see things, and thereby, for example, our distractibility. The project is also expected to show how intensively training the mind to be free of expectation through meditation can change how we habitually perceive things. Lastly, the project is expected to shed light on the neural mechanisms that determine which percept dominates our conscious experience.