Vibrissa

Vibrissa, the singular form of vibrissae, is a specialized tactile hair found on the faces of many mammals. Typically longer and stiffer than ordinary hairs, each vibrissa grows from a deep follicle that is richly innervated and connected to a blood sinus, enabling sensitive detection of deflection. In most species vibrissae are arranged in fixed groups on the face, including mystacial vibrissae on the upper lip, genal vibrissae along the cheeks, supraorbital vibrissae above the eyes, and, in some animals, carpal vibrissae on the forelimbs.

Anatomy and movement: The vibrissa follicle-sinus complex anchors the hair and houses mechanoreceptors. A dense network of nerves and surrounding tissues allows precise sensing of contact, texture, and air movement. Muscles can actively move the whiskers, enabling the animal to scan its surroundings by sweeping the whiskers through the environment.

Function: Vibrissae provide high-resolution tactile information that supports navigation, obstacle avoidance, texture and object discrimination, and prey detection, particularly in darkness, murky water, or cluttered habitats. They can also play a role in social signaling for some species.

Neural processing: Sensory input from vibrissae travels via the trigeminal nerve to brainstem and thalamic stations, then to the somatosensory cortex. In many mammals, a specialized cortical representation, often described as a barrel cortex, encodes whisker input, linking whisker position to precise sensory perception.

Development and variation: Vibrissae are generally long-lasting but can be shed and regenerated. The number, arrangement, and sensitivity of vibrissae vary by species and individual.