Same, But Different

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Science  04 Nov 2011:
Vol. 334, Issue 6056, pp. 571
DOI: 10.1126/science.334.6056.571-a

Cephalopods, such as octopus and cuttlefish, are the most advanced of the invertebrates. Their nervous system is as large as that of a dog, and their behavior is complex and sophisticated. Yet the organization of their brain is much simpler than that of vertebrates. Shomrat et al. characterized and compared the memory and learning networks in the large vertical lobe of the octopus and the cuttlefish to determine whether the physiology of neuronal networks is constrained by computational considerations. Both systems consisted of a simple two-layered network with a computationally typical fan-out–fan-in organization. The connectivity pattern was also the same in both animals: The first synaptic connection was glutamatergic and the second cholinergic; however, the synaptic sites of short- and long-term plasticity and neuromodulation were different. In the octopus, the first fan-out connection showed short- and long-term plasticity, whereas in the cuttlefish it was the second fan-in connection. These findings may have implications for our understanding of the evolution of microcircuits in the nervous system. The same structures produce similar functions via distinct mechanisms, presumably shaped by evolutionary pressures

Curr. Biol. 21, 1 (2011).

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