Abstract
SUMMARYActive tactile perception combines directed motion with sensory signals to generate mental representations of objects in space. Competing models exist for how mice use these signals to determine the precise location of objects along their face. We tested six of these models using behavioral manipulations and statistical learning in head-fixed mice. Trained mice used a whisker to locate a pole in a continuous range of locations along the anteroposterior axis. Mice discriminated locations to ≤0.5 mm (<2°) resolution. Their motor program was noisy, adaptive to touch, and directed to the rewarded range. This exploration produced several sets of sensorimotor features that could discriminate location. Integration of two features, touch count and whisking midpoint at touch, was the simplest model that explained behavior best. These results show how mice locate objects at hyperacute resolution using a learned motor strategy and minimal set of mentally accessible sensorimotor features.
Highlights
Locating objects through the sense of touch is an essential behavior across animal species
We trained water-restricted head-fixed mice (n = 15) to discriminate the location of a smooth vertical pole randomly presented in contiguous ranges of go (0–5 mm) and no-go (5–10 mm) positions along the anteroposterior axis of the animal, about 8 mm lateral from the whisker pad (Figure 2A)
Sensorimotor Features at Touch that Discriminate Location and Choice What features of touch could mice possibly use to discriminate location? We examined how six sensorimotor features associated with proposed hyperacute localization models (Figure 1) were distributed at the instant of touch
Summary
Locating objects through the sense of touch is an essential behavior across animal species. Tactile object localization is an active process that combines directed sensor motion with mechanosensory signals. Rodents sweep their large whiskers back and forth and use the resulting tactile sensations to locate [1] and orient to objects [2] and guide navigation [3]. High-speed videography [10] and physical models [11,12,13,14] can quantify motion and forces that drive whisker input with submillisecond resolution during behavior [15, 16]. Examination of the activity patterns within and across these cortical columns has revealed how sensorimotor features of tactile exploration are represented and processed in the brain [17,18,19,20,21]
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