Classification of Ocellar Interneurones in the Cockroach Brain

ABSTRACT Nine types of ocellar interneurones with arborizations in the ocellar tract have been identified in the cockroach, Periplaneta americana. These neurones are classified into (1) five types of ‘PS-neurone’, which project into the posterior slope, (2) two types of ‘OL-neurone’, which project into the lobula and medulla of the optic lobe, and (3) two types of ‘D-neurone’, which descend to the thoracic ganglia. When recordings were made in the ocellar tract, all types of neurones exhibited similar responses: a tonic hyperpolarization during illumination and one or a few transient depolarizations at the end of illumination. However, these neurones are classified into several physiological types from the responses recorded in their axons or terminal regions.