Sensorimotor mapping and oropharyngeal reflexes in goldfish, Carassius auratus.

The vagal lobe of goldfish and some carps is a laminated, specialized lobe of the midmedulla containing both primary sensory terminals and primary motor neurons. Both the sensory and motor components are represented in the lobe in a matching, orotopic fashion, i.e. the oral cavity is mapped across the surface of the lobe. Anatomical tracing studies reveal that the circuitry exists for a point-to-point reflex system in which the superficial sensory layers are mapped directly onto the underlying motor layer. The utility of this relatively direct sensorimotor coupling appears to be in terms of sorting food within the mouth according to its gustatory properties. The direct coupling between the mapped sensory layer and the similarly mapped motor layer may be a useful model in which to study the evolutionary development of less tightly coupled sensorimotor systems.