Sebastian Seung Explores the Brain's Wiring (BSP 85)

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Dr. Sebastian Seung

Dr. Sebastian Seung (MIT) is an ambitious young scientist; his goal is to unravel the entire wiring diagram of the human brain.  Considering that it took over a decade to determine the wiring diagram for the roundworm C elegans, which has a mere 302 neurons, it is clear that scientists can't leap directly to the 80 billion neuron human brain.  Even so, in his new book Connectome: How the Brain's Wiring Makes Us Who We Are, Seung makes a very good argument for the value of this long-term project.  In Episode 85 of the Brain Science Podcast I talked with Dr. Seung both about the challenges and potential benefits of this work.

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References and Links:

Send me feedback at brainsciencepodcast@gmail.com.

Interview with Neuroscience Pioneer Eve Marder, PhD (BSP 56)

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Episode 56 of the Brain Science Podcast is an interview with neuroscientist, Eve Marder, PhD.  Dr. Marder has spent 35 years studying the somatogastric ganglion of the lobster.  In this interview we talk about how she got into neuroscience during its early days, her recent tenure as president of the Society for Neuroscience, and how some of her key discoveries have implications for studying more complex nervous systems.

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

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 of  synapse 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.

Year-end Review for 2007 (BSP 27)

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Episode 27 is a look back on the first 26 episodes of the Brain Science Podcast.

I look back on some of the main topics that we have explored including memory, consciousness, emotions, decision-making, body maps, and plasticity.  Then I talk a little about what I hope to do in the covering year.  This episode is a little more personal than most, and will mainly be of interest to regular listeners.  It includes some ideas about how you can help the Brain Science Podcast grow and prosper.

However, in preparing this episode, I went back over the past year's episodes, and I have prepared a list of all the episodes so far and the main topics.  This should help both new listeners and regulars to find episodes that pertain to particular topics.

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"Memory: From Mind to Molecules" (BSP 12)

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This episode of the Brain Science Podcast is a discussion of memory based on the book, Memory: From Mind to Molecules (2000), by Larry R. Squire, and Eric R. Kandel.

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Show Notes

I highly recommend that you get this book for yourself if you want to read the details of the experiments.  The book contains excellent illustrations.

Some of the experimental animals mentioned in this episode include Aplysia (giant sea snails), drosophila (fruit flies), and mice.

Mechanisms of memory formation and storage seem to be shared from the simplest non-vertebrates up through humans.

Types of Memory:    declarative and non-declarative. Non-declarative memory is generally NOT subject to conscious awareness or control.

There are many different types of non-declarative memory including:

Declarative memory, which seems to be unique to animals that have a hippocampus and cerebral cortex, includes short-term (immediate and working memory) and long-term memory.  Much research has been devoted to discovering how and where long-term memory occurs.  The answer may surprise you.

This episode includes a discussion of some of the unanswered questions in memory research.

How Neurons Communicate: A Detailed Introduction (BSP 8)

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When I started preparing for this week's episode I realized that before I could discuss neurotransmitters (brain chemicals) I would need to discuss some basic information about how neurons work. Thus this episode is rather long and technical, but hopefully understandable to those who are new to the field. I am including more detailed show notes than I usually do, along with the approximate times for the main sections, in case there is a particular topic you want to go back and review.

How to get this episode:

  • Premium Subscribers now have unlimited access to all old episodes and transcripts.
  • Buy BSP 1-10 (zip file of mp3 files)
  • Transcripts: BSP 1-14
  • The most recent 25 episodes of the Brain Science Podcast are still FREE. See the individual show notes for links the audio files.

The main source for this episode was the textbook, From Neuron to Brain: A Cellular and Molecular Approach to the Function of the Nervous System, Fourth Edition (2001)

Topic Outline:

2:39-11:33 Neuronal signaling-the basics of electrical and chemical signaling types of signaling-electrical and chemical introducing the synapse the importance of membrane proteins

11:55 - 13:03   A bried discussion of how the brain differs from a  digital computer

13:3 3-13:50   Definition of neurotransmitters-

13:56 -22:10   How neurotransmitters interact with receptors in the synapse

-direct and indirect  chemical synapses-why they are important

-neuromuscular junction-an example of a direct chemical synapse

-the importance of synaptic delay

-the role of second messengers in indirect chemical synapses

-release and recycling of neurotransmitters

22:25 -29:42 Types of Neurotransmitters and how they work-with examples

-how neuropeptides differ from low molecular weight neurotransmitters

-a little about how drugs work

29:58 - 41:54  How Neurotransmitters function in the Central Nervous System-with examples

-Glutamate is the key excitatory neurotransmitter in the brain

-an aside about Nutrasweet™ (30:33)

-glycine and GABA are inhibitatory

-acetycholine (33:32-34:34)

-discussion of Molecules of Emotion by Candace Pert (35:30-36:55)

-serotonin

-histamine

-dopamine and Parkinson's disease

42:07 - 43:36  Closing Summary

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