Surprising Discoveries about Synapse Evolution with Seth Grant (BSP 51)

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Episode 51 of the Brain Science Podcast is an interview with Dr. Seth Grant from Cambridge University, UK.  Dr. Grant's work focuses on the proteins that make up the receptors within synapses.  (Synapses are the key structures by which neurons send and receive signals.)  By comparing the proteins that are present in the synapses in different species, Dr. Grant has come to some surprising conclusions about the evolution of the synapse and the evolution of the brain.

In this interview, Dr. Grant explains how his research team has uncovered the identity ofsynapse proteins in a variety of species including yeast, fruit flies, and mice.  Our discussion is centered on the paper he published in Nature Neuroscience in June 2008.  Dr. Grant's team has made several surprising discoveries.  First, he has discovered that some proteins associated with neuron signaling are actually found in primitive unicellular organisms like yeast. He has also discovered that the protein structure of the synapse becomes more complex as one moves from invertebrates like fruit flies to vertebrates like mice, but that most of the complexity seems to have arisen early on in vertebrates.

According to Dr. Grant:

The origins of the brain appear to be in a protosynapse, or ancient set of proteins found in unicellular animals; and when unicellular animals evolved into metazoans, or multicellular animals, their protosynaptic architecture was co-opted and embelished by the addition of new proteins onto that ancient protosynaptic set; and that set of new molecules was inserted into the junctions of the first neurons, or the synapse between the first neurons in simple invertebrate animals.  When invertebrates evolved into vertebrates, around a billion years ago, there was a further addition, or enhancement of the number of these synaptic molecules, and that has been conserved throughout vertebrate evolution, where they have much larger numbers of synaptic molecules.  The large complex synapses evolved before large anatomically complex brains.

The discovery that there are significant differences between the synapses in vertebrates and non-vertebrates is significant, because it has long been assumed that synapses were essentially identical between species, and that brain and behavioral complexity was based on having more neurons and bigger brains.  Instead, Dr. Grant proposes an alternative hypothesis:

The first part of the brain to ever evolve was the protosynapse. In other words, synapses came first.

When this big synapse evolved, what the vertebrate brain then did, as it grew bigger and evolved afterwards; it exploited the new proteins that had evolved into making new types of neurons in new types of regions of the brain. In other words, we would like to put forward the view that the synapse evolution has allowed brain specialization, regionalization, to occur.

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Addition Show Notes and Links

References:

Blog posts and other links:

Learn more about Dr. Grant's work:

Send email feedback to Ginger Campbell, MD at brainsciencepodcast@gmail.com.

Brain Evolution with Gary Lynch, PhD (BSP 48)

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Episode 48 of the Brain Science Podcast is an interview with Gary Lynch, PhD, co-author (with Richard Granger) of Big Brain: The Origins and Future of Human Intelligence.  Dr. Lynch has spent decades studying memory at the level of the synapse.  His work with computer simulations based on how the brain really works led him to a fascination with the question of how our brains got so large.  Are humans smart because we have big brains or because are brains are different?

Dr. Lynch argues that the unique features of the human brain are a natural result of increased brain size.  He also argues against the conventional view that increasing brain size resulted from selection pressures during the millions of years of primate evolution that proceeded the emergence of homo sapiens.  We talk about the evidence supporting this radical position during the interview.

We also talk about another radical theory that Dr. Lynch has proposed, which is the idea that the olfactory cortex formed the template for the evolution of the cortex in mammals and primates.  This intriguing theory brings a new perspective to the fact that the olfactory system has unique access to important brain systems including the frontal lobes, the amygdala (which is involve in emotion), and the hippocampus (which is essential to long-term memory.

In addition to discussing the evidence that led him to his controversial theories, Dr. Lynch discusses the challenges facing scientists interested in pursuing research questions about brain evolution.

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References and Links:

The figure below is used with the permission of the author and the artist (Cheryl Cotman).

Send email feedback to Ginger Campbell, MD at brainsciencepodcast@gmail.com

Review: "Principles of Brain Evolution" (BSP 47)

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Episode 47 of the Brain Science Podcast is a discussion of Principles of Brain Evolution by Georg F. Striedter.  My goal is to highlight the main ideas of this complicated and often controversial subject.  Understanding the principles of brain evolution is an important element in our multidisciplinary attempt to understand how our brains make us who we are.

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Show Notes and Links:

Important terms:

  • homologues: characteristics with shared ancestry.

  • neurocladistics: a rigorous method for classifying neural structures based on their ancestry.

  • small-world network: a mathematical graph where most nodes connect to nearby nodes but almost any two can be connect in relatively small number of steps (the famous six-degrees of separation).

  • Boskop man: an extinct hominid that is thought to have had a larger brain than modern humans.

People and scientists discussed:

Announcements:

Donations and Subscriptions are appreciated

Send email feedback to Ginger Campbell, MD at brainsciencepodcast@gmail.com

What Do We Know about the Evolution of Human Thought?

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In a recent blog post I objected to Richard Lewontin's claim that we know nothing about the evolution of the human brain.  Apparently my reaction was shared by quite a few researchers in the field.  Michael Balter describes their reaction at an interdisciplinary panel that was also held at this year's AAAS annual meeting.

One thing that seems to drive some of these discussions is a difference of opinion about whether their is an insurmountable gap between human intelligence and what other animals can do.  This connects with the ongoing debate about the importance of genetic factors.  But there seems to be no doubt that this is an extremely fruitful area of research.

"How Human Intelligence Evolved--Is It Science or 'Paleofantasy'?" by Michael Balter. Science 22 February 2008: Vol. 319. no. 5866, p. 1028

Lewontin Claims We Know Nothing About Brain Evolution

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Episode 30 of the Brain Science Podcast was devoted to the subject of language evolution.  In that episode, I mentioned Steven Jay Gould's claim that language was a spandrel, an incidental by-product of evolution.  Gould's co-author on his famous 1970's paper about spandrels was Richard Lewontin, who is well-known for disagreeing with prevailing opinions in evolution.  At the recent annual meeting of the American Association for the Advancement of Science, he reportedly gave a talk that discounted all the current theories about brain evolution.

I have not read the transcript of his lecture, but I just finished reading Georg Striedter's comprehensive textbook, Principles of Brain Evolution  (2005).  This text is highly regarded by leaders in neuroscience research like Michael S Gazzaniga.  It does an excellent job of describing both the challenges and progress in the field, as well as exploring the pros and cons of alternative theories.  I can't help wondering what Lewontin's comments contribute to the field.  Of course, it is reasonable to point out how limited our knowledge is, but to  dismiss the work of so many scientists seems rather arrogant. If anyone has access to the transcript I would like to read it.

From AAAS: The Evolution of Morality

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The Science magazine podcast is providing highlights from this year's AAAS meeting in Boston.

So far, I found the discussion of the evolution of morality with Marc Hauser and several other scientists to very interesting.  One issue that was raised was whether the utility of a theory depends on its ability to generate testable hypotheses.  Listen and let me know what you think.

The Evolution of Language (BSP 30)

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Episode 30 of the Brain Science Podcast is a discussion of The First Word: The Search for the Origins of Language, by Christine Kenneally.  We focus mostly on the first part of the book, which tells the story of how the study of language evolution has grown from almost a banned subject to a new field of inquiry called evolutionary linguistics.  We also reflect on how recent findings in neuroscience like the importance of plasticity are influencing the field.

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Scientists discussed in the Episode:

*References:

*Additional references can be found in Kenneally's book and at the websites of the scientists listed above.  Also, be sure to check out Kenneally's blog for follow-up information.

The Wisdom of the Aging Brain (BSP 17)

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This week we discuss another book by Elkonon Goldberg, Ph.D.  I highly recommend this book to everyone, because it is an excellent review of many of the topics we have discussed over the last several months including memory, emotion, and neuroplasticity.   In this episode, we continue our discussion of the role of the pre-frontal lobes in intelligence, as well as what happens to our brain as we age.

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Show Notes

I want to thank Matthew Lofton for pointing out to me that there is evidence that elephants can recognize themselves in a mirror.  This means I was wrong when I said (in #16) that only humans and some primates can do this. He referred us to "I, Elephant," by Kaspar Mossmanin in the February 2007 issue of Scientific American Mind.  The original article was "Self-recognition in an Asian elephant," by:Plotnik, Joshua M.; de Waal, Frans B. M.; Reiss, Diana. Proceedings of the National Academy of Sciences of the United States of America, 11/7/2006, Vol. 103 Issue 45, p17053-17057.  He posted this information as a comment, but I wanted to bring this to everyone's attention.

Episodes that are referred to in this episode:

Note: You should have no problem listening to Episode #17 first, but I have provided these references for those who want to review or go back for more details.

Definitions used in this episode:

  • Attractor: a cognitive template that enables pattern recognition. An attractor is thought to be a concise set of neurons with strong interactions among themselves. A unique and important quality of attractors is that a broad range of inputs activate the same set of neurons. This is thought to be the mechanism of pattern recognition.

  • Cognitive competence: the ability to relate the old to the new so as to recognize the similarities between a new problem and one that has been previously solved.

  • Cognitive wisdom: an enhanced capacity for problem solving

  • Generic memory: memory for patterns

Brief list of topics discussed in this episode:

  • Review of important ideas about the prefrontal lobes from #16.

  • An hypothesis about the differing roles of the right and left hemispheres.

  • How the brain changes in normal aging.

  • Mechanisms that protect the brain from degenerative changes:

    • Generic memory-why this type of memory is more robust.

    • Pattern expansion-how parts of the cortex expand with use.

    • Effortless experts-why familiar tasks are less demanding.

    • Why vigorous mental activity is important throughout life.

For more links related to Dr. Goldberg's work see the show notes for Episode 16.

Emotion (BSP 11)

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Emotion: The Science of Sentiment, by Dylan Evans, is the featured book for this episode of the Brain Science Podcast.  Thanks to Kate from the UK for suggesting this book.

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  • Transcripts: BSP 1-14

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Show Notes

This episode is a short introduction to the idea that our emotions are an essential part of our intelligence.

  • We discuss the basic emotions, based on the work of anthropologist Paul Eckman.

  • We learn about culturally-learned emotions, such as "being a wild pig," which is observed among the Gurumba people of New Guinea.

  • Paul Griffiths introduced the idea of "higher cognitive emotions."

  • Emotions seem to exist on a continuum from the highly innate basic emotions to the culturally specific emotions.

  • The work of Joseph Ledoux and Antonio Damasio reveal that our emotions are an important element of normal intelligence.

  • We consider how fear actually follows two pathways in the brain.

  • We consider the role of the limbic system including the amygdala.

  • We consider the relationship between emotions and mood.

  • We consider how mood affects memory and decision making.

  • This includes Robert Zajonc's discovery of the "mere exposure" effect.

  • We briefly consider the question of whether computers could ever display emotions.

Further Reading:

The Feeling of What Happens: Body and Emotion in the Making of Consciousness (2000), by Antonio Damasio.

Review of "The First Idea" by Shanker & Greenspan (BSP 6)

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Episode 6 of the Brain Science Podcast is a discussion of The First Idea: How Symbols, Language, And Intelligence Evolved from Our Primate Ancestors to Modern Humans, by Stanley I. Greenspan, MD and Stuart G. Shanker, DPhil.

I wanted to talk about emotion, but I generally base the Brain Science Podcast on my current reading; which is why I chose this rather difficult book that touches on psychology, child development, evolution, and theories about the emergence of language and intelligence.

The basic premise which is discussed in the podcast is that emotional signaling is the basis for the emergence of language and intelligence.  Evidence supporting this hypothesis is discussed, as is how the theory challenges long-standing theories about language and intelligence.

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  • Buy BSP 1-10 (zip file of mp3 files)

  • Transcripts: BSP 1-14

  • New episodes of the Brain Science Podcast are always FREE.  All episodes posted after January 1, 2013, are free.  See the individual show notes for links the audio files.