ABSTRACT
A receptor array is considered to be a two-dimensional, spatial distribution of sensory neurons and their closely associated interneurons in a bounded area. There can be hundreds to tens of thousands of receptors. The sensory neurons are in close proximity so that their output signals can interact locally in underlying interneuronal ganglia before the processed information is sent to the CNS. Examples of large sensory arrays include the vertebrate retina, the arthropod compound eye (CE) and optic lobes (OL), the vertebrate olfactory system, and the vertebrate cochlear system. In small sensory arrays, the sensory neurons generally send their axons directly to the CNS (e.g., ampullary electroreceptors in sharks, skates, and rays), or send their axons to a small numbers of interneurons, which in turn send axons to the CNS (e.g., gravity receptors in the cockroach,
Arenivaga
). This chapter describes the signal processing that occurs in the arthropod com-
pound eyes and OL. These receptor arrays have many interesting properties, including interneuron interactions that permit enhanced optical resolution and “feature extraction” from visual objects. Some visual feature extraction operations may be associated with dynamic flight stabilization; others may have to do with finding food, or a mate, or sensing danger. Unlike higher vertebrates, where sophisticated visual information takes place in the visual cortex of the brain, insects and crustaceans appear to do most of their visual feature extraction in their OLs, which lie directly under the receptors. The OL ganglia then send the processed information to the animal’s brain and ventral cord ganglia.
