Because escape responses are so critical, the nerve fibers that
control them in many invertebrates tend to be especially large.
The tail-flick escape response of crayfish, which is often
successful, is mediated by such “giant” nerve fibers. But even
those giant fibers are no match for a shrew’s myelinated fibers.
And shrews have a second advantage as well: they are warm-
blooded, and thus their nervous system is always at the optimum
temperature for peak performance. The combination of those two
attributes makes shrews formidable predators, at least from the
perspective of a crayfish. If escape fails and a battle ensues,
a shrew quickly prevails. The shrew’s brain is ultimately
responsible for its sensory abilities, so we have sought to
understand how the animal’s brain is organized and how that
might contribute to the shrew’s skill as a predator. In all
mammals, an outer six-layered sheet of tissue called the
neocortex is the final processing station for visual, tactile,
and auditory information. To investiga