Synaptic background activity controls spike transfer from thalamus to cortex.
Characterizing the responsiveness of thalamic neurons is crucial to understanding the flow of sensory information. Typically, thalamocortical neurons possess two distinct firing modes. At depolarized membrane potentials, thalamic cells fire single action potentials and faithfully relay synaptic inputs to the cortex. At hyperpolarized potentials, the activation of T-type calcium channels promotes burst firing, and the transfer is less accurate. Our results suggest that this duality no longer holds if synaptic background activity is taken into account. By injecting stochastic conductances into guinea-pig thalamocortical neurons in slices, we show that the transfer function of these neurons is strongly influenced by conductance noise. The combination of synaptic noise with intrinsic properties gives a global responsiveness that is more linear, mixing single-spike and burst responses at all membrane potentials. Because in thalamic neurons, background synaptic input originates mainly from cortex, these results support a determinant role of corticothalamic feedback during sensory information processing.
Wolfart
Jakob
J
Unité de Neurosciences Integratives et Computationnelles, Centre National de la Recherche Scientifique, 91198 Gif-sur-Yvette, France. jakob.wolfart@unklinik-freiburg.de
Debay
Damien
D
Le Masson
Gwendal
G
Destexhe
Alain
A
Bal
Thierry
T
D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D016477:Artifacts; D020747:Calcium Channels, T-Type / Q000502:physiology; D002462:Cell Membrane / Q000502:physiology; D004558:Electric Stimulation; D005246:Feedback / Q000502:physiology; D005829:Geniculate Bodies / Q000502:physiology*; D006168:Guinea Pigs; D009474:Neurons / Q000502:physiology*; D009924:Organ Culture Techniques; D012684:Sensory Thresholds / Q000502:physiology; D009435:Synaptic Transmission / Q000502:physiology*; D014793:Visual Cortex / Q000502:physiology*; D014795:Visual Pathways / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology
D020747:Calcium Channels, T-Type