(1) The basal lobe is the ultimate controller which contains two lobes that are connected by commissures. Electrical stimulation of the lobes evokes eye, head, and tentacle movements, and removal of the lobes bilaterally induces symptoms characteristic of a neocortical ablation in mammals, causing the abolition of all the primary senses while retaining the basic reflexes.
(2) Damage of the optic lobe or peduncle induces blindness, but the animal can still move about and use its remaining senses to live. Whether a combination of lesions here induces blindsight has not been explored. This could be investigated by independently severing the two main visual pathways that interconnect the optic lobe with the basal lobe.
(3) The inferior frontal system is akin to M1 of mammals, and it sends direct projections to the eight spinal cords, one per tentacle (labelled ANC--for axial nerve cord--in the figure below). Note that each spinal cord contains up to 40 million neurons, and collectively they (the eight spinal cords) represent more neurons than found in the CNS (Olson and Ragsdale 2023).
(4) The vestibular sense is regulated by the statocyst. Details related to the efference-copy mechanism (a cerebellum) must be housed in the pedal and brachial lobes, which are bi-lobes not connected by commissures, much like what is found for the cerebellar hemispheres of mammals.
(5) The ANC is the spinal cord mechanism per tentacle. If the spinal cord is transected from the ANC then stepping movements can still be evoked, as is true following spinal transection in vertebrates. Acetylcholine is used to contract the muscles.
(6) A family member of the octopus is the giant squid which is preyed upon by Sperm whales (Moby Dick). Since Sperm whales are very smart (just ask Captain Ahab), a giant squid (Footnote 1) must also be very smart when dealing with Moby Dick who must travel a thousand meters with limited oxygen to eat squid.
Footnote 1: The giant squid has a similar nervous system to that of the octopus, but with tentacles/spinal cords spanning 10-13 meters in length.
Figure 1: The central nervous system of the octopus highlighting the major ganglia. See text for details. From figure 3 of Olson and Ragsdale (2023).
Very interesting. My knowledge of this is, like most people's, limited. The octopus demonstrates extreme problem-solving techniques but the belief is they lack memory capacity.
Dear Dr. Wilkin,
It seems even amoeba can remember things to learn; therefore I would suggest that an octopus, which is many orders of magnitude smarter based on the number of neurons (about 500 million) too has the capacity for memory and learning. Memory in mammals is believed to be stored at the level of individual synapses, according to Donald Hebb (1949, 1968) and Eric Kandel (2006). This storage happens in the neocortex for declarative memory and in the cerebellum for implicit/motor memory. Whether such a functional segragation exists in the octopus awaits empirical conformation. The basal lobe is known to have neurons that make associations between the different senses; this is a prerequisite for consciousness.
Ed Tehovnik.
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