Optical recording of oscillatory neural activities in the molluscan brain.

The procerebrum (PC) of the terrestrial slug shows a coherent oscillatory activity. Information is encoded in the PC by neurons with synchronized oscillatory activity, and the oscillatory activity will propagate to other brain regions as the PC transmits information. Using the optical recording of membrane potentials and the correlation analysis, we showed that the metacerebrum/mesocerebrum (MC) region also shows an oscillatory activity coherent with that of the PC. The MC oscillation was either inphase or antiphase with the PC oscillation, and its amplitude was larger when it was antiphase than it was inphase. These results indicate that the MC is capable of producing an oscillatory activity, possibly driven by synaptic input from the PC.