title: A Quantitative Analysis of Context-Dependent Remapping of Medial Frontal Cortex Neurons and Ensembles.
abstract: The frontal cortex has been implicated in a number of cognitive and motivational processes, but understanding how individual neurons contribute to these processes is particularly challenging as they respond to a broad array of events (multiplexing) in a manner that can be dynamically modulated by the task context, i.e., adaptive coding (Duncan, 2001). Fundamental questions remain, such as how the flexibility gained through these mechanisms is balanced by the need for consistency and how the ensembles of neurons are coherently shaped by task demands. In the present study, ensembles of medial frontal cortex neurons were recorded from rats trained to perform three different operant actions either in two different sequences or two different physical environments. Single neurons exhibited diverse mixtures of responsivity to each of the three actions and these mixtures were abruptly altered by context/sequence switches. Remarkably, the overall responsivity of the population remained highly consistent both within and between context/sequences because the gains versus losses were tightly balanced across neurons and across the three actions. These data are consistent with a reallocation mixture model in which individual neurons express unique mixtures of selectivity for different actions that become reallocated as task conditions change. However, because the allocations and reallocations are so well balanced across neurons, the population maintains a low but highly consistent response to all actions. The frontal cortex may therefore balance consistency with flexibility by having ensembles respond in a fixed way to task-relevant actions while abruptly reconfiguring single neurons to encode "actions in context."
  
  
  
  Flexible modes of behavior involve performance of similar actions in contextually relevant ways. The present study quantified the changes in how rat medial frontal cortex neurons respond to the same actions when performed in different task contexts (sequences or environments). Most neurons altered the mixture of actions they were responsive to in different contexts or sequences. Nevertheless, the responsivity profile of the ensemble remained fixed as did the ability of the ensemble to differentiate between the three actions. These mechanisms may help to contextualize the manner in which common events are represented across different situations.
authors.affiliation: Robarts Research Institute, University of Western Ontario, London, Ontario N6A 5B7, Canada, liyamariama@gmail.com.
authors.forename: Liya
authors.identifier: 0000-0003-0183-7155
authors.initials: L
authors.lastname: Ma
authors.affiliation: Department of Psychology, University of Nevada Las Vegas, Las Vegas, Nevada 89154.
authors.forename: James M
authors.identifier: 0000-0001-7099-5312
authors.initials: JM
authors.lastname: Hyman
authors.affiliation: Department of Theoretical Neuroscience, Bernstein Center for Computational Neuroscience, Central Institute of Mental Health, Medical Faculty Mannheim, Heidelberg University, 68159 Mannheim, Germany, and.
authors.forename: Daniel
authors.initials: D
authors.lastname: Durstewitz
authors.affiliation: Department of Psychiatry, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada.
authors.forename: Anthony G
authors.identifier: 0000-0002-4077-5471
authors.initials: AG
authors.lastname: Phillips
authors.affiliation: Department of Psychiatry, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada.
authors.forename: Jeremy K
authors.initials: JK
authors.lastname: Seamans
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology; D000818:Animals; D003071:Cognition / Q000502:physiology*; D003198:Computer Simulation; D003657:Decision Making / Q000502:physiology; D005625:Frontal Lobe / Q000502:physiology*; D008297:Male; D008959:Models, Neurological; D009415:Nerve Net / Q000502:physiology*; D009473:Neuronal Plasticity / Q000502:physiology*; D009474:Neurons / Q000502:physiology*; D051381:Rats; D020318:Rats, Long-Evans; D013647:Task Performance and Analysis
keywords: behavioral flexibility; ensemble analysis; medial prefrontal cortex