Spindle Neurons in Humpback Whales

from Hof & Van Der Gucht (2006)

Spindle Neurons: The Next New Thing?

In July, The Neurocritic wrote about a special class of cells found in the anterior cingulate cortex and frontoinsular cortex of humans and great apes. These spindle neurons are a unique type of neuron found in layer Vb in the ACC and FI cortex of humans. In 1999, it was discovered that besides humans, only great apes have spindle neurons (Nimchinsky et al.).

And now we can add humpback whales to the select group of animals who possess these magical spindle neurons.

Hof PR, Estel Van Der Gucht E. (2006). Structure of the cerebral cortex of the humpback whale, Megaptera novaeangliae (Cetacea, Mysticeti, Balaenopteridae). Anatom Rec Part A, Early View (Published Online: 27 Nov 2006).

Cetaceans diverged from terrestrial mammals between 50 and 60 million years ago and acquired, during their adaptation to a fully aquatic milieu, many derived features, including echolocation (in odontocetes), remarkable auditory and communicative abilities, as well as a complex social organization. Whereas brain structure has been documented in detail in some odontocetes, few reports exist on its organization in mysticetes. We studied the cerebral cortex of the humpback whale (Megaptera novaeangliae) in comparison to another balaenopterid, the fin whale, and representative odontocetes. We observed several differences between Megaptera and odontocetes, such as a highly clustered organization of layer II over the occipital and inferotemporal neocortex, whereas such pattern is restricted to the ventral insula in odontocetes. A striking observation in Megaptera was the presence in layer V of the anterior cingulate, anterior insular, and frontopolar cortices of large spindle cells, similar in morphology and distribution to those described in hominids, suggesting a case of parallel evolution. They were also observed in the fin whale and the largest odontocetes, but not in species with smaller brains or body size. The hippocampal formation, unremarkable in odontocetes, is further diminutive in Megaptera, contrasting with terrestrial mammals. As in odontocetes, clear cytoarchitectural patterns exist in the neocortex of Megaptera, making it possible to define many cortical domains. These observations demonstrate that Megaptera differs from Odontoceti in certain aspects of cortical cytoarchitecture and may provide a neuromorphologic basis for functional and behavioral differences between the suborders as well as a reflection of their divergent evolution.

John Allman's Lab at Cal Tech thinks

they participate in fast, intuitive social decision-making. We have found that the Von Economo [spindle] neurons emerge mainly in the first three years after birth. We also have evidence that in autistic subjects the Von Economo neurons are abnormally located, possibly as a result of a migration defect. This abnormality may be at least partially responsible for defective social intuition in autism.

It's interesting to see how the popular press is covering this finding:

Humpback whales have "human" brain cells: study

WASHINGTON (Reuters) - Humpback whales have a type of brain cell seen only in humans, the great apes, and other cetaceans such as dolphins, U.S. researchers reported on Monday.

This might mean such whales are more intelligent than they have been given credit for, and suggests the basis for complex brains either evolved more than once, or has gone unused by most species of animals, the researchers said.

The finding may help explain some of the behaviors seen in whales, such as intricate communication skills, the formation of alliances, cooperation, cultural transmission and tool usage, the researchers report in The Anatomical Record.

Patrick Hof and Estel Van der Gucht of the Department of Neuroscience at Mount Sinai School of Medicine in New York studied the brains of humpback whales and discovered a type of cell called a spindle neuron in the cortex, in areas comparable to where they are seen in humans and great apes.

Although the function of spindle neurons is not well understood, they may be involved in cognition -- learning, remembering and recognizing the world around oneself. Spindle cells may be affected by Alzheimer's disease and other debilitating brain disorders such as autism and schizophrenia.

Oh, here's a great one. Whale-human chimeras:

New study finds some whales have human brain cells

NEW YORK: Brains of some species of whales have spindle neurons, the elongated nerve cells found in humans and some great apes and associated mostly with decision-taking and involved in higher cognitive functions like consciousness and expressing emotions, say U.S. scientists who have studied whales.

What is surprising is that these cells in whales were found located in the same region as in human brain and these were absent in smaller-brained whales and also in dolphins. Two of the whales which possessed spindle neurons are the humpback whale and the fin whale.

. . .

The two wrote in the report, "In spite of the relative scarcity of information on many cetacean species, it is important to note in this context that sperm whales, killer whales, and certainly humpback whales, exhibit complex social patterns that included intricate communication skills, coalition-formation, cooperation, cultural transmission and tool usage."