Periodic Reporting for period 4 - PERCEPT (The mind's eye: How expectation and attention shape perception)
Reporting period: 2020-07-01 to 2022-01-31
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, predictions grounded in 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 likely ‘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 addressed 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 used an integrated application of psychophysical, neuroimaging, brain stimulation, mathematical modelling, and pharmacological techniques. The research program comprised three subprojects. The first subproject examined 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 tested 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 shed novel light on the mechanisms that underlie experience and the extent to which these mechanisms are plastic, with important implications for the study of clinical disorders characterized by dysfunctional experience of the world.
The project comprised three subprojects. The objective of the first subproject was to determine how predictions derived from previous experience and statistical regularities in the environment influence sensory processing and perception. We found that predictions grounded in statistical regularities in the environment quickly structure what we attend to and what we ignore, and play a particularly important role in helping the brain ignore distracting information. In particular, our findings show how experience with distracting information renders it less distracting to the brain by revealing the underlying neural mechanisms.
The objective of the second subproject was to determine the automaticity of predictive processing using meditation. Here, we specifically asked if and how meditation can reduce the effect of past experience on current experience. We developed a novel theoretical framework, grounded in the notion of the predictive brain, in which we propose that meditation - by bringing the practitioner more and more into the present moment - gradually reduces the temporal depth of predictive processing, and thereby, the influence of the past learning on current experience. We propose that this can explain also the unusual experiences reported by expert meditators during meditation, such as loss of sense of self and time. We also set up and ran several neuroimaging studies in expert meditators to test the predictions that can be derived from this theoretical framework, and gain insight into the plasticity of the predictive mind.
The objective of the third subproject was 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 did not provide evidence that dopamine affects what percept dominates our conscious experience. In addition, we ran 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 their actions. Finally, we have suggested a theoretical extension of the most dominant theoretical framework of the predictive brain, the free energy principle.
The objective of the second subproject was to determine the automaticity of predictive processing using meditation. Here, we specifically asked if and how meditation can reduce the effect of past experience on current experience. We developed a novel theoretical framework, grounded in the notion of the predictive brain, in which we propose that meditation - by bringing the practitioner more and more into the present moment - gradually reduces the temporal depth of predictive processing, and thereby, the influence of the past learning on current experience. We propose that this can explain also the unusual experiences reported by expert meditators during meditation, such as loss of sense of self and time. We also set up and ran several neuroimaging studies in expert meditators to test the predictions that can be derived from this theoretical framework, and gain insight into the plasticity of the predictive mind.
The objective of the third subproject was 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 did not provide evidence that dopamine affects what percept dominates our conscious experience. In addition, we ran 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 their actions. Finally, we have suggested a theoretical extension of the most dominant theoretical framework of the predictive brain, the free energy principle.
The project findings go beyond the state of the art by revealing how past experience influences how we perceive and attend to the world around us. The project has also delineated how intensively training the mind to be free of expectation through meditation may change how we habitually perceive and give attention to things. Lastly, the project results contribute to theories on the neural mechanisms that determine which percept dominates our conscious model of the world around us.