Figure 3. Octopus learning and memory circuits contain parallel paths. Amacrine cell numbers are for Octopus vulgaris (Young, 1971) and granule cell numbers are for Mus musculus. (a). The tactile learning and memory system converges on the subfrontal lobe, with a long path that passes through the inferior frontal lobes and a short path (dotted line) through the posterior buccal lobe. (b). The visual learning and memory system converges on the vertical lobe. The long path passes through the superior frontal lobes, while the short path goes through the subvertical lobe. (c). Parallel long and short paths are a feature of learning and memory systems. In the vertebrate cerebellum, for example, sensorimotor information from the spinal cord reaches the deep cerebellar nuclei through parallel paths. The deep cerebellar nuclei send output back to the spinal cord through intermediaries, such as the red nucleus and the neocortex (not shown). Note that, although not diagrammed, many of these feed-forward connections are reciprocated.