Neuron
-
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.
-
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.
-
Convergent evidence suggests that corticostriatal interactions act as a gate to select the input to working memory (WM). However, not all information in WM is relevant for behavior simultaneously. For this reason, a second "output gate" might advantageously govern which contents of WM influence behavior. ⋯ Moreover, PFC and striatum correlated with distinct behavioral profiles. Whereas PFC recruitment correlated with mean efficiency of selection from WM, striatal recruitment and frontostriatal interactions correlated with its reliability, as though such dynamics stochastically gate WM's output. These results support the output gating hypothesis, suggesting that contextual representations in PFC influence striatum to select which information in WM drives responding.
-
Learning models propose a role for both signed and unsigned prediction errors in updating associations between cues and aversive outcomes. In this issue of Neuron, Klavir et al. (2013) show how these errors arise from the interplay between the amygdala and anterior cingulate cortex.
-
The ability to switch flexibly between aversive and neutral behaviors based on predictive cues relies on learning driven by surprise or errors in outcome prediction. Surprise can occur as absolute value of the error (unsigned error) or its direction (signed errors; positive when something unexpected is delivered and negative when something expected is omitted). ⋯ We report that errors exist in different magnitudes and that they differentially develop at millisecond resolution. Our results support a model where unsigned errors first develop in the amygdala during successful learning and then propagate into the dACC, where signed errors develop and are distributed back to the amygdala.