Matched filtering in active whisker touch

Abstract

Whiskers are present on most mammals, and whisker specialists, such as rodents, pinnipeds and insectivores, can actively position their whiskers to efficiently guide navigation, locomotion and exploration. That only a small number of whiskers give enough information about the local environment to be the primary tactile sense in many mammals has prompted researchers to explore how well adapted the whisker system is and how “matched” these sensors are to their function. In this chapter, we suggest that whisker touch systems have a matched filter design by arguing that (i) the layout of the vibrissae and their mechanical properties provide a computationally cheap way to gather tactile and spatial information; (ii) this layout is topographically mapped throughout the brain, enabling temporal and spatial information to be preserved easily during processing, freeing up other areas of the brain; and (iii) movement of the whiskers can focus the sensors onto salient regions of space and also control the amount, type and quality of information gathered from an environment. That anatomical and behavioural characteristics are maintained throughout many different mammalian orders indicates the importance of vibrissal touch sensing in arboreal, nocturnal animals, hence its conservation throughout mammalian evolution.