REGULATION OF INSECT BRAIN EXCITABILITY BY OCELLUS

Unitary discharges were recorded from various areas of the brain in the fleshfly (Boettcherisca peregrina), whose compound eyes were occluded to light but the ocelli were exposed to it. 1. Giving olfactory and mechanical stimulation to the antenna, the excitatory and the inhibitory neurones were found. In the excitatory neurones the unitary discharges appeared during the stimulation or the spontaneous discharges were increased by it. Phasic responses were found mostly in the protocerebrum, and tonic ones were in the deutocerebra, tritocerebra and the suboesophageal ganglion. In the inhibitory neurones the spontaneous discharges disappeared during the stimulation. The inhibition of the discharge was tonic in the deuto- and tritocerebra. 2. When the ocelli were illuminated, the frequency of the spontaneous discharges was increased in many units and was decreased in some units. 3. By turning off the illumination to the ocelli, the unitary response to the antennal stimulation was decreased (light facilitatory unit) in most units of the protocerebrum, while it was increased (light occlusive unit) in most units of the deutocerebra, tritocerebra and the suboesophageal ganglion. 4. By darkening the ocelli, the latency of the unitary response was prolonged in most of the light facilitatory units, while it was shortened in the light occlusive units. 5. The light facilitatory units were mainly found in the medial region of the brain, and the light occlusive units were in the dorsal region of the protocerebrum and in the ventral region of the deutocerebra, tritocerebra and the suboesophageal ganglion. The results suggest that the ocelli regulate the brain activity. © 1969 Springer-Verlag.