ACTIVITY PATTERNS IN THE ISOLATED CENTRAL NERVOUS SYSTEM OF THE BARNACLE AND THEIR RELATION TO BEHAVIOR

¹ Department of Biology, Reed College, Portland, Oregon 97202

1. Rhythmical patterns of activity in most nerve trunks of the sessile barnacle, Balanus cariosus (Pallas) have been demonstrated to occur in the totally isolated central nervous system at a periodicity consistent with the behavior of the intact animal.

2. When activity in various nerves is compared by simultaneous recording, a pattern of phase relationships is observed that is consistent with the hypothesis that the patterned activity constitutes a program that determines the behavior of the barnacle.

3. The evidence presented suggests that the centrally generated rhythm is autogenic, because in the isolated central nervous system there is no possibility of regular timing cues being made available to central neurons from peripheral sense organs, and no apparent stimulation is required to start and maintain the rhythm.

4. Single muscle fibers in the adductor scutorum muscle attached to the otherwise isolated central nervous system show excitatory junctional potentials with the same temporal rhythm and the expected in-phase, out-of-phase relationships with a variety of nerve trunks including its own supply.

5. It is suggested that observed variation in intact barnacle behavior may be brought about in the system by some direct influence on oscillator neurons and/or sensory feed-back to modulate the extent and timing of rhythmical activity and by uncoupling the timer from the motor output side by turning it off (inhibition) during periods of inactivity. The first of these would also explain frequency variations seen in the isolated preparations in the absence of sensory feed-back.

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