AP BIOLOGY

Detailed explanation-1: -In the octopus, as far other cephalopod species, the ‘brain’ is assembled through a series of ganglia of molluscan origin to form lobes that are fused together into masses (for the common octopus see description in Young, 1971; see also an outline of the brain and its main connections in Figure 1A).

Detailed explanation-2: -Flatworms (Planaria) These cords are connected to cerebral ganglia located in the head region.

Detailed explanation-3: -The cerebellum is connected via large myelinated tracts to a number of different brain regions, allowing it to participate in brain-wide information processing (Schmahmann, 2019). The octopus brain contains about 150 million neurons, while the octopus PNS has 350 million neurons (Budelmann, 1994).

Detailed explanation-4: -The central brain of the octopus is arranged quite differently from the vertebrate brain. It is composed of about 40 interconnected lobes which are arranged, typically for invertebrate ganglia, with the cell bodies of the monopolar neurons forming an outer cortex.