Membrane potential dynamics of neocortical projection neurons driving target-specific signals.

Primary sensory cortex discriminates incoming sensory information and generates multiple processing streams toward other cortical areas. However, the underlying cellular mechanisms remain unknown. Here, by making whole-cell recordings in primary somatosensory barrel cortex (S1) of behaving mice, we show that S1 neurons projecting to primary motor cortex (M1) and those projecting to secondary somatosensory cortex (S2) have distinct intrinsic membrane properties and exhibit markedly different membrane potential dynamics during behavior. Passive tactile stimulation evoked faster and larger postsynaptic potentials (PSPs) in M1-projecting neurons, rapidly driving phasic action potential firing, well-suited for stimulus detection. Repetitive active touch evoked strongly depressing PSPs and only transient firing in M1-projecting neurons. In contrast, PSP summation allowed S2-projecting neurons to robustly signal sensory information accumulated during repetitive touch, useful for encoding object features. Thus, target-specific transformation of sensory-evoked synaptic potentials by S1 projection neurons generates functionally distinct output signals for sensorimotor coordination and sensory perception.

Yamashita T ，Pala A ，Pedrido L ，Kremer Y ，Welker E ，Petersen CC ... -  《-》

Target-specific membrane potential dynamics of neocortical projection neurons during goal-directed behavior.

Yamashita T ，Petersen CCh 《eLife》

Synaptic mechanisms underlying sparse coding of active touch.

Sensory information is actively gathered by animals, but the synaptic mechanisms driving neuronal circuit function during active sensory processing are poorly understood. Here, we investigated the synaptically driven membrane potential dynamics during active whisker sensation using whole-cell recordings from layer 2/3 pyramidal neurons in the primary somatosensory barrel cortex of behaving mice. Although whisker contact with an object evoked rapid depolarization in all neurons, these touch responses only drove action potentials in ∼10% of the cells. Such sparse coding was ensured by cell-specific reversal potentials of the touch-evoked response that were hyperpolarized relative to action potential threshold for most neurons. Intercontact interval profoundly influenced touch-evoked postsynaptic potentials, interestingly without affecting the peak membrane potential of the touch response. Dual whole-cell recordings indicated highly correlated membrane potential dynamics during active touch. Sparse action potential firing within synchronized cortical layer 2/3 microcircuits therefore appears to robustly signal each active touch response.

Crochet S ，Poulet JF ，Kremer Y ，Petersen CC ... -  《-》

Characteristics of synaptic connections between rodent primary somatosensory and motor cortices.

Rocco-Donovan M ，Ramos RL ，Giraldo S ，Brumberg JC ... -  《-》

Pathway-specific reorganization of projection neurons in somatosensory cortex during learning.

Chen JL ，Margolis DJ ，Stankov A ，Sumanovski LT ，Schneider BL ，Helmchen F ... -  《-》