Abstract
Active sensing involves the fusion of internally generated motor events with external sensation. For rodents, active somatosensation includes scanning the immediate environment with the mystacial vibrissae. In doing so, the vibrissae may touch an object at any angle in the whisk cycle. The representation of touch and vibrissa self-motion may in principle be encoded along separate pathways, or share a single pathway, from the periphery to cortex. Past studies established that the spike rates in neurons along the lemniscal pathway from receptors to cortex, which includes the principal trigeminal and ventral-posterior-medial thalamic nuclei, are substantially modulated by touch. In contrast, spike rates along the paralemniscal pathway, which includes the rostral spinal trigeminal interpolaris, posteromedial thalamic, and ventral zona incerta nuclei, are only weakly modulated by touch. Here we find that neurons along the lemniscal pathway robustly encode rhythmic whisking on a cycle-by-cycle basis, while encoding along the paralemniscal pathway is relatively poor. Thus, the representations of both touch and self-motion share one pathway. In fact, some individual neurons carry both signals, so that upstream neurons with a supralinear gain function could, in principle, demodulate these signals to recover the known decoding of touch as a function of vibrissa position in the whisk cycle.
Highlights
Animals navigate the world around them with actively moving sensory organs [1]
Animals interrogate the world around them with actively moving sensory organs, resulting in a blend of sensory inputs: one input is from the object under study, while the second is from self-generated movement of the sensor
A well-known example is proprioception, in which receptors in the limb muscles and joints are used to infer the position of tactile sensors in the hands
Summary
Animals navigate the world around them with actively moving sensory organs [1]. This process results in a blend of sensory input from the presence of two underlying sensory signals. The detection of an external stimulus with confidence, as well as the ability to confirm the position and trajectory of the sensor, depends on the ability of the animal to distinguish among internally versus externally generated sensations Ambiguity among these sources leads to unpleasant outcomes, such as vertigo [3] and motion sickness [4] for the case of vestibular control. To resolve this ambiguity, nervous systems use three complementary signaling mechanisms to reference input from a sensory organ relative to the position of the sensors [5]. These three mechanisms report complementary, but not necessarily complete [6], information on sensor position
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