#191: Finding Your Place with Dr. Mayank Mehta

July 28, 2017

Think of any board game you played as a kid.

Chances are good that the game-board was divided up into squares, or spaces, or steps on a path, or a hexagon grid over a map, or something.  It seems like there’s almost nothing more natural to us than mapping environments into discreet chunks of space.  A chessboard seems like the classic example.

But maybe there is a far older, far more ancient example — an example that pre-dates not only human games, but humanity itself, stretching back into the brains of the long-extinct common ancestors that we share with most parts of the animal kingdom.

Almost four decades ago, researchers discovered cells within the brain that are triggered when a physical location is recognized and perceptually “inhabited by” an animal.  Called “Place Cells,” these neurons apparently filled one role that could be considered either incredibly boring or incredibly complex.

The boring part is their output: On for “we’re here,” and off otherwise.  A little like the red light that is on outside the deejay’s doorway when recording is in session.

The complex part is: How in the heck to the place cells actually know where they are?

In humans, place cells seem to form a grid.

The grid’s cells are about a yard across.

Does this seem like too much?  Too little?  Is it surprising there is a fixed number to this abstraction at all?  But apparently, there is.  This is the fundamental unit of the human mind’s inner map.  Europeans use kilometers; Americans use miles; old sailors used leagues… But for the map inside your skull, the built-in scale seems to be around a yard.

As a discrete distance for your location, the brain thinks a yard is “close enough.”

In recent years, researchers have found new ways to explore how place cells discern our locations from the perceptual clues offered by reality.  And in some cases, by virtual reality.

Dr. Mayank Mehta, a UCLA professor in the departments of Physics & Astronomy, Neurology, and Neurobiology (yes, you read that right) has been working for years to interrogate the brain’s inner cartographer.  Much of his most groundbreaking work has been done with rats.  Can an animal that operates so heavily off of its sense of smell be fooled by a visually-based virtual environment?  How many of the rodent place cells will buy in to the illusion?  And what exactly is happening with those that don’t?

Episode #191 provides a fascinating interview with a man who is literally pushing into the borderlands of physical reality…and charting new territory.

Show Notes
  • 00:00:32

    Episode Introduction: Finding Your Place with Dr. Mayank Mehta

  • 00:01:45

    This Week in Neuroscience: Tells In Your Computer Mouse

  • 00:05:39

    Smarts Drug Smarts News + Updates

  • 00:06:57

    Interview Lead-in: Dr. Mayank Mehta and Place Cells

  • 00:08:17

    Interview Begins: Dr. Mayank Mehta

  • 00:10:32

    What Are Place Cells?

  • 00:12:55

    Making Virtual Reality For... Rats.

  • 00:14:24

    How To Make Virtual Reality Feel Real For Rats

  • 00:18:36

    How The Brain Tells Apart: Real vs. Virtual

  • 00:20:00

    Hippocampus Sensory Inputs

  • 00:23:02

    Visual Cues & Place Cells

  • 00:25:37

    Hippocampus, Place Cells, Space, and Memory

  • 00:28:23

    Theta Rhythm

  • 00:32:15

    What Virtual Reality Has Revealed

  • 00:36:50

    The Matrix: For Rats?

  • 00:40:47

    Interview Wrap-Up

  • 00:41:40

    Ruthless Listener Retention Gimmick: Aetiology of Anxiety

  • 00:44:04

    Episode Wrap-Up

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