Читать книгу The Behavior of Animals - Группа авторов - Страница 61

The fact that underemployed cortical regions take over functions of overemployed regions is documented by neuroimaging in people blind from early age. Their visual cortex is activated by tactually reading Braille or embossed Roman letters or by other tactile discrimination tasks. Evidence of this sensory substitution was provided by transient disruption of the visual cortex by means of transcranial magnetic stimulation TMS. This induced errors in tactual discrimination tasks and distorted tactile perception in blind, but not in sighted test subjects (Cohen et al. 1997). Blindness causes the visual cortex to be recruited to a role in somatosensory processing, which contributes to the superior tactile perceptual talents of blind people.

Convergence of different sensory channels implies crossmodal interactions. In humans and most animals, a sudden touch to the body can enhance vision near that body part. Actually, cutaneous stimulation facilitates visual responses in the visual cortex (Cohen et al. 1997; Macaluso et al. 2000).

The notion that neural structures may have a “universal potential” is also in line with the fact that a perceptual principle may be implemented in different neural structures. “Lateral inhibition”—a principle by which contrast-borders are highlighted—discovered in the compound eye of the horseshoe crab, Limulus (Hartline 1949), is such a principle that works also in visual and tactile perception in vertebrates. The features-relating-algorithm—a principle of prey-selection—realized in the brains of toad (amphibian), mudskipper (fish), and mantis (insect) provides another example.