Bidirectional plasticity of intrinsic excitability controls sensory inputs efficiency in layer 5 barrel cortex neurons in vivo.
Responsiveness of cortical neurons to sensory inputs can be altered by experience and learning. While synaptic plasticity is generally proposed as the underlying cellular mechanism, possible contributions of activity-dependent changes in intrinsic excitability remain poorly investigated. Here, we show that periods of rhythmic firing in rat barrel cortex layer 5 pyramidal neurons can trigger a long-lasting increase or decrease in their membrane excitability in vivo. Potentiation of cortical excitability consisted of an increased firing in response to intracellular stimulation and a reduction in threshold current for spike initiation. Conversely, depression of cortical excitability was evidenced by an augmented firing threshold leading to a reduced current-evoked spiking. The direction of plasticity depended on the baseline level of spontaneous firing rate and cell excitability. We also found that changes in intrinsic excitability were accompanied by corresponding modifications in the effectiveness of sensory inputs. Potentiation and depression of cortical neuron excitability resulted, respectively, in an increased or decreased firing probability on whisker-evoked synaptic responses, without modifications in the synaptic strength itself. These data suggest that bidirectional intrinsic plasticity could play an important role in experience-dependent refinement of sensory cortical networks.
Centre de Recherche de l'Institut du Cerveau et de la Moelle épinière, Université Pierre et Marie Curie (UPMC), INSERM UMR-S 975, CNRS UMR 7225, Hôpital Pitié-Salpêtrière, F-75013, Paris, France. severine.mahon@upmc.fr
Séverine
S
Mahon
Stéphane
S
Charpier
D000200:Action Potentials / Q000502:physiology; D000344:Afferent Pathways / Q000502:physiology*; D000818:Animals; D001710:Biotin / Q000031:analogs & derivatives / Q000378:metabolism; D058256:Brain Waves / Q000502:physiology; D004558:Electric Stimulation; D004569:Electroencephalography; D008297:Male; D009473:Neuronal Plasticity / Q000502:physiology*; D010812:Physical Stimulation; D017966:Pyramidal Cells / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011930:Reaction Time / Q000502:physiology; D013003:Somatosensory Cortex / Q000166:cytology* / Q000502:physiology*; D014738:Vibrissae / Q000294:innervation*
C070614:neurobiotin; D001710:Biotin