title: Spike count, spike timing and temporal information in the cortex of awake, freely moving rats.
abstract: OBJECTIVE
  Sensory processing of peripheral information is not stationary but is, in general, a dynamic process related to the behavioral state of the animal. Yet the link between the state of the behavior and the encoding properties of neurons is unclear. This report investigates the impact of the behavioral state on the encoding mechanisms used by cortical neurons for both detection and discrimination of somatosensory stimuli in awake, freely moving, rats.
  
  
  METHODS
  Neuronal activity was recorded from the primary somatosensory cortex of five rats under two different behavioral states (quiet versus whisking) while electrical stimulation of increasing stimulus strength was delivered to the mystacial pad. Information theoretical measures were then used to measure the contribution of different encoding mechanisms to the information carried by neurons in response to the whisker stimulation.
  
  
  RESULTS
  We found that the behavioral state of the animal modulated the total amount of information conveyed by neurons and that the timing of individual spikes increased the information compared to the total count of spikes alone. However, the temporal information, i.e. information exclusively related to when the spikes occur, was not modulated by behavioral state.
  
  
  CONCLUSIONS
  We conclude that information about somatosensory stimuli is modulated by the behavior of the animal and this modulation is mainly expressed in the spike count while the temporal information is more robust to changes in behavioral state.
authors.affiliation: School of Biomedical Engineering, Science and Health Systems, Drexel University, 3141 Chestnut Street, PA 19104, Philadelphia, USA. National Institute on Aging, National Institutes of Health, Baltimore, MD, USA.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Scaglione
authors.forename: Guglielmo
authors.initials: G
authors.lastname: Foffani
authors.forename: Karen A
authors.initials: KA
authors.lastname: Moxon
mesh_terms: D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D001522:Behavior, Animal / Q000502:physiology; D002540:Cerebral Cortex / Q000502:physiology*; D004558:Electric Stimulation; D004567:Electrodes, Implanted; D051381:Rats; D013003:Somatosensory Cortex / Q000502:physiology; D014738:Vibrissae / Q000294:innervation / Q000502:physiology; D014851:Wakefulness / Q000502:physiology*