A teeny clump of cells that was not quite a brain

From 7½ Lessons
Jump to navigation Jump to search

A note for The Half-Lesson, "Your Brain Is Not for Thinking," in Seven and a Half Lessons About the Brain by Lisa Feldman Barrett.
Some context from page 1–2 is:

Its meager nervous system included a teeny clump of cells that was not quite a brain.

The appendix adds:

Scientists continue to debate whether amphioxi have brains. It all comes down to where you draw the dividing line between “brain” and “not a brain.”

The quote that I present in the appendix, "Nothing like the vertebrate brain is seen in either tunicates [sea squirts] or the amphioxus, although there are traces of its ground plan...if one looks hard enough," can be found on page 7 in [1].

For technical information on the amphioxus nervous system, see these papers (and references therein).[1][2][3][4][5][6]

For an interesting discussion on the definition of a brain, see this paper.[7]


  1. 1.0 1.1 Gee, Henry. 2018. Across the Bridge: Understanding the Origin of the Vertebrates. Chicago, IL: University of Chicago Press.
  2. Striedter, Georg F., and R. Glenn Northcutt. 2020. Brains Through Time: A Natural History of Vertebrates. New York: Oxford University Press.
  3. Bertrand, Stephanie and Hector Escriva. 2011. “Evolutionary Crossroads in Developmental Biology: Amphioxus.” Development 138 (22): 4819–4830.
  4. Lacalli, Thurston C. 2008. “Basic Features of the Ancestral Chordate Brain: A Protochordate Perspective.” Brain Research Bulletin 75 (2-4): 319–323.
  5. Wicht, Helmut and Thurston C. Lacalli. 2005. “The Nervous System of Amphioxus: Structure, Development, and Evolutionary Significance.” Canadian Journal of Zoology 83 (1): 122–150.
  6. Cisek, Paul. 2019. "Resynthesizing Behavior Through Phylogenetic Refinement." Attention, Perception and Psychophysics 81 (7): 2265–2287.
  7. Pagán, Oné R. 2019. "The Brain: A Concept in Flux." Philosophical Transactions of the Royal Society B 374 (1774): 20180383.