Neuron
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This Perspective reviews recent findings in placebo hypoalgesia and provides a conceptual account of how expectations and experience can lead to placebo hypoalgesia. In particular, we put forward the idea that the ascending and the descending pain system resembles a recurrent system that allows for the implementation of predictive coding-meaning that the brain is not passively waiting for nociceptive stimuli to impinge on it but is actively making inferences based on prior experience and expectations. ⋯ We discuss how modulatory neurotransmitters such as opioids might be related to the characterization of expectations with an emphasis on the precision of these expectations. Finally, we develop experimental strategies that are suited to test this framework at the behavioral and neuronal level.
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Most behaviors, even simple innate reflexes, are mediated by circuits of neurons spanning areas throughout the brain. However, in most cases, the distribution and dynamics of firing patterns of these neurons during behavior are not known. We imaged activity, with cellular resolution, throughout the whole brains of zebrafish performing the optokinetic response. ⋯ By correlating neuronal responses with an array of sensory and motor variables, we find that the network can be clearly divided into distinct functional modules. Comparing aligned data from multiple fish, we find that the spatiotemporal activity dynamics and functional organization are highly stereotyped across individuals. These experiments systematically reveal the functional architecture of neural circuits underlying a sensorimotor behavior in a vertebrate brain.