LFP and oscillations-what do they tell us?
Bottom Line: In particular, we treat oscillations as the (observable) signature of context-sensitive changes in synaptic efficacy that underlie coordinated dynamics and message-passing in the brain.This rich source of information is now being exploited by various procedures-like dynamic causal modelling-to test hypotheses about neuronal circuits in health and disease.Furthermore, the roles played by neuromodulatory mechanisms can be addressed directly through their effects on oscillatory phenomena.
Affiliation: The Wellcome Trust Centre for Neuroimaging, University College London, Queen Square, London WC1N 3BG, UK. Electronic address: firstname.lastname@example.org.Show MeSH
Related in: MedlinePlus
Mentions: The circumstantial evidence for predictive coding is substantial—both in terms of the anatomy of extrinsic (between-areas) and intrinsic (within-area) connections and the physiology of synaptic interactions . In these schemes, top-down predictions are used to form prediction errors at each level of cortical and subcortical hierarchies. The prediction errors are then returned to the level above to update predictions in a Bayesian sense. In brief, the prediction errors report the ‘newsworthy’ information from a lower hierarchical level that was not predicted by the higher level. A crucial aspect of this message passing is the selection of ascending information by adjusting the ‘volume’ or gain of prediction errors that compete for influence over higher levels of processing. Functionally, this gain corresponds to the expected precision (inverse variance or signal-to-noise ratio) that sets the confidence afforded to prediction errors. Psychologically this has been proposed as the basis of attentional gain . Physiologically, precision corresponds to the postsynaptic gain or sensitivity of cells reporting prediction errors (currently thought to be large principal cells that send extrinsic efferents of a forward type, such as superficial pyramidal cells in cortex). This is important because the synaptic gain or efficacy of coupled neuronal populations determines the form of their spectral (oscillatory) behaviour. See Figure 1. Because, synchronous activity determines synaptic gain , oscillations have a mechanistic impact on neuronal processing—rather than being epiphenomenal—which completes the circular causality between synchrony and synaptic efficacy.
Affiliation: The Wellcome Trust Centre for Neuroimaging, University College London, Queen Square, London WC1N 3BG, UK. Electronic address: email@example.com.