Abstract:Stable perception arises from the interaction between sensory inputs and internal activity fluctuations in cortex. Here we analyzed how different types of activity contribute to cortical sensory processing at the cellular scale. We performed whole-cell recordings in the barrel cortex of anesthetized rats while applying ongoing whisker stimulation and measured the information conveyed about the time-varying stimulus by different types of input (membrane potential) and output (spiking) signals. We found that sub… Show more
“…5 C ). This decrease in the late component is likely caused by reducing cortical recurrent activity triggered by the sensory input, which in some cases also induced UP states (Anderson et al 2000; Hasenstaub et al 2007; Reig and Sanchez-Vives 2007; Alenda et al 2010). Figure 4.Whisker deflection activates M1 after the initial response in S1.…”
Section: Resultsmentioning
confidence: 99%
“…5). This delayed response component may reflect a stimulus-evoked UP state (Anderson et al 2000; Hasenstaub et al 2007; Reig and Sanchez-Vives 2007; Alenda et al 2010), which often originates in more frontal cortical regions (Massimini et al 2004; Ruiz-Mejias et al 2011). Another possibility might be the delayed protraction of the whiskers following the initial air puff.…”
Individual striatal neurons integrate somatosensory information from both sides of the body, however, the afferent pathways mediating these bilateral responses are unclear. Whereas ipsilateral corticostriatal projections are prevalent throughout the neocortex, contralateral projections provide sparse input from primary sensory cortices, in contrast to the dense innervation from motor and frontal regions. There is, therefore, an apparent discrepancy between the observed anatomical pathways and the recorded striatal responses. We used simultaneous in vivo whole-cell and extracellular recordings combined with focal cortical silencing, to dissect the afferent pathways underlying bilateral sensory integration in the mouse striatum. We show that unlike direct corticostriatal projections mediating responses to contralateral whisker deflection, responses to ipsilateral stimuli are mediated mainly by intracortical projections from the contralateral somatosensory cortex (S1). The dominant pathway is the callosal projection from contralateral to ipsilateral S1. Our results suggest a functional difference between the cortico-basal ganglia pathways underlying bilateral sensory and motor processes.
“…5 C ). This decrease in the late component is likely caused by reducing cortical recurrent activity triggered by the sensory input, which in some cases also induced UP states (Anderson et al 2000; Hasenstaub et al 2007; Reig and Sanchez-Vives 2007; Alenda et al 2010). Figure 4.Whisker deflection activates M1 after the initial response in S1.…”
Section: Resultsmentioning
confidence: 99%
“…5). This delayed response component may reflect a stimulus-evoked UP state (Anderson et al 2000; Hasenstaub et al 2007; Reig and Sanchez-Vives 2007; Alenda et al 2010), which often originates in more frontal cortical regions (Massimini et al 2004; Ruiz-Mejias et al 2011). Another possibility might be the delayed protraction of the whiskers following the initial air puff.…”
Individual striatal neurons integrate somatosensory information from both sides of the body, however, the afferent pathways mediating these bilateral responses are unclear. Whereas ipsilateral corticostriatal projections are prevalent throughout the neocortex, contralateral projections provide sparse input from primary sensory cortices, in contrast to the dense innervation from motor and frontal regions. There is, therefore, an apparent discrepancy between the observed anatomical pathways and the recorded striatal responses. We used simultaneous in vivo whole-cell and extracellular recordings combined with focal cortical silencing, to dissect the afferent pathways underlying bilateral sensory integration in the mouse striatum. We show that unlike direct corticostriatal projections mediating responses to contralateral whisker deflection, responses to ipsilateral stimuli are mediated mainly by intracortical projections from the contralateral somatosensory cortex (S1). The dominant pathway is the callosal projection from contralateral to ipsilateral S1. Our results suggest a functional difference between the cortico-basal ganglia pathways underlying bilateral sensory and motor processes.
“…Axon projections of L5 slender-tufted neurons have been shown to establish functional connections with L2/L3 pyramidal neurons (32,33). However, as spiking in supragranular layers does not increase significantly upon active whisking (20,41), the sensory information carried by these intracortical long range projections is likely within fine-scale synaptic activity (42). During active whisking, the membrane potential of L2 and L3 pyramidal neurons may therefore be locked to the phase of individual slender-tufted neurons (41).…”
Section: Contribution Of Slender-tufted Neurons To Cortical Signalingmentioning
The cortical output layer 5 contains two excitatory cell types, slender-and thick-tufted neurons. In rat vibrissal cortex, slendertufted neurons carry motion and phase information during active whisking, but remain inactive after passive whisker touch. In contrast, thick-tufted neurons reliably increase spiking preferably after passive touch. By reconstructing the 3D patterns of intracortical axon projections from individual slender-and thick-tufted neurons, filled in vivo with biocytin, we were able to identify cell type-specific intracortical circuits that may encode whisker motion and touch. Individual slender-tufted neurons showed elaborate and dense innervation of supragranular layers of large portions of the vibrissal area (total length, 86.8 ± 5.5 mm). During active whisking, these long-range projections may modulate and phase-lock the membrane potential of dendrites in layers 2 and 3 to the whisking cycle. Thick-tufted neurons with soma locations intermingling with those of slender-tufted ones display less dense intracortical axon projections (total length, 31.6 ± 14.3 mm) that are primarily confined to infragranular layers. Based on anatomical reconstructions and previous measurements of spiking, we put forward the hypothesis that thick-tufted neurons in rat vibrissal cortex receive input of whisker motion from slender-tufted neurons onto their apical tuft dendrites and input of whisker touch from thalamic neurons onto their basal dendrites. During tactile-driven behavior, such as object location, near-coincident input from these two pathways may result in increased spiking activity of thick-tufted neurons and thus enhanced signaling to their subcortical targets.axon reconstruction | barrel cortex | dysgranular zone B ased on classification of dendrite morphology, cortical layer 5 (L5) contains two primary excitatory cell types: slenderand thick-tufted neurons (1, 2). These two types are considered the main output neurons of a cortical column (3, 4). Slender-(or thin-) tufted pyramidal neurons project to the striatum and are commonly referred to as corticostriatal neurons. Thick-(or tall-) tufted pyramidal neurons project to the posterior nucleus of the thalamus, brainstem, superior colliculus, and pons (5-7). The two neuron types have been characterized across cortical areas, including somatosensory, visual, auditory, motor, and prefrontal cortices, and therefore represent canonical elements of the cortical microcircuitry (8-18).We recently showed that slender-and thick-tufted neurons in L5 of vibrissal cortex differentially increase spiking activity depending on the behavioral state (19,20). The majority of slender-tufted neurons carry phase information upon free-whisking (i.e., selfmotion of whiskers). Their modulation depth is highest among all excitatory cell types in vibrissal cortex. During quiet (i.e., nonwhisking) periods or passive whisker deflection (i.e., touch), however, slender-tufted neurons remain relatively inactive. In contrast, thick-tufted neurons are reliably activated upon passive ...
“…Similar results were obtained from human BOLD fMRI data, which showed a robust and specific learning-related modulation of spontaneous activity (Lewis et al 2009). Along similar lines, Alenda et al (2010) showed that an ongoing stimulus can modulate spontaneous membrane potential fluctuations throughout its duration. As a result, it was suggested that the cortex behaves somewhat like a central pattern generator, a system with rich spontaneous dynamics that is strongly modulated by, and responsive to, sensory inputs (Yuste et al 2005).…”
While the neuronal activity of the cerebral cortex is strongly modulated by sensory inputs, the cortex also exhibits rich spontaneous dynamics. Experimental evidence suggests that sensory stimulation may shape the spontaneous activity of the cortex, which in turn can influence its responses to further external stimulation. However, we still do not understand how sensory stimuli affect the underlying neural circuitry. Here we study whether spike-timing-dependent plasticity (STDP) can mediate sensory-induced modifications in the spontaneous dynamics of a new large-scale model of layers II, III and IV of the rodent barrel cortex. A central feature of our model is its level of physiological detail, including the types of neurons present, the probabilities and delays of connections, and the STDP profiles at each excitatory synapse. We stimulated the neuronal network with a protocol of repeated sensory inputs, resembling those generated by the protraction-retraction motion of whiskers when rodents explore their environment, and studied the changes in network dynamics. By applying dimensionality reduction techniques to the synaptic weight space, we show that the trajectories converge to an initial spontaneous attractor state, which is modified by each repetition of the stimulus. This reverberation of the sensory experience induces long-term modifications in the synaptic weight space. The post-stimulus spontaneous state encodes a unique memory of the stimulus presented, since a different dynamical response is observed when the network is presented with shuffled stim- uli. These results suggest that repeated exposure to the same sensory experience could induce long-term circuitry modifications via 'Hebbian' STDP plasticity.
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