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Evoked brain responses are generated by feedback loops

Garrido, MI; Kilner, JM; Kiebel, SJ; Friston, KJ; (2007) Evoked brain responses are generated by feedback loops. P NATL ACAD SCI USA , 104 (52) 20961 - 20966. 10.1073/pnas.0706274105. Gold open access

Abstract

Neuronal responses to stimuli, measured electrophysiologically, unfold over several hundred milliseconds. Typically, they show characteristic waveforms with early and late components. It is thought that early or exogenous components reflect a perturbation of neuronal dynamics by sensory input bottom-up processing. Conversely, later, endogenous components have been ascribed to recurrent dynamics among hierarchically disposed cortical processing levels, top-down effects. Here, we show that evoked brain responses are generated by recurrent dynamics in cortical networks, and late components of event-related responses are mediated by backward connections. This evidence is furnished by dynamic causal modeling of mismatch responses, elicited in an oddball paradigm. We used the evidence for models with and without backward connections to assess their likelihood as a function of peristimulus time and show that backward connections are necessary to explain late components. Furthermore, we were able to quantify the contribution of backward connections to evoked responses and to source activity, again as a function of peristimulus time. These results link a generic feature of brain responses to changes in the sensorium and a key architectural component of functional anatomy; namely, backward connections are necessary for recurrent interactions among levels of cortical hierarchies. This is the theoretical cornerstone of most modern theories of perceptual inference and learning.

Type: Article
Title: Evoked brain responses are generated by feedback loops
Open access status: An open access publication
DOI: 10.1073/pnas.0706274105
Publisher version: http://www.ncbi.nlm.nih.gov/pmc/ articles/PMC24092...
Keywords: connectivity, dynamic causal modeling, EEG, predictive coding, top-down, CORTICAL CONNECTIONS, NEURONAL CIRCUITS, VISUAL-CORTEX, TOP-DOWN, PERCEPTION, ERP, NEOCORTEX, MODEL
UCL classification: UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences > UCL Queen Square Institute of Neurology
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences > UCL Queen Square Institute of Neurology > Clinical and Movement Neurosciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences > UCL Queen Square Institute of Neurology > Imaging Neuroscience
URI: http://discovery.ucl.ac.uk/id/eprint/112794
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