Sensory information flows in parallel pathways from whiskers to cortex. Sensory fibres from the whisker follicle run via the trigeminal nerve to brainstem nuclei, which project to nuclei in the contralateral thalamus, which in turn project to somatosensory cortex. The lemniscal pathway (red) runs via the principal nucleus and the dorsomedial section of the ventroposterior medial nucleus (VPMdm) to barrels in layer 4 of primary somatosensory cortex (S1). The extralemniscal pathway (blue) runs via the interpolar nucleus and the ventrolateral section of the VPM (VMPvl) to septa between barrels and to w:secondary somatosensory cortex (S2). The paralemniscal pathway (green) runs via the interpolar nucleus and the posterior nucleus (POm) to S2 and to barrel columns in S1 especially layer 5 (image by Peter Haslehurst, adapted from Diamond et al., 2008 and Fox, 2008).

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