To accompany Baars & Gage - Chapter 3 1 Chapter 3. Elsevier web materials.

To accompany Baars & Gage - Chapter 3

1

Chapter 3.

Elsevier web materials.


2

Chapter 3.

Neurons.

• Teaching materials.

• Powerpoints with movies, figures, and major chapter points.

• Study Guide• Quiz items

Yun Bo Yi & Sastri, U MichSingle neuron model - NSF


3

Basic parts of a neuron.


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It's a jungle in there --

Real neurons come in a rich variety of sizes, shapes and functions.


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Recording two patterns of spikes from a thalamic neuron.

McCormick Lab, Yale University(Audio will click when neuron fires)

QuickTime™ and aYUV420 codec decompressor

are needed to see this picture.


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Recording axonal spikes from a face-sensitive neuron.

Points to Notice:

-- This is the right hemisphere, "looking right." -- close-up zoom-- can you name the major lobes?-- rotation to the medial (inside) view


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Neurons that control eye movements.

Notice the flattened sheet of the cortex


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"Mirror neurons" are involved in imitation.

• Source: Pulvermueller, (?)

Notice that the graphs record "spikes per second" for each neuron. The upper traces show the actual firing

patterns.

Mirror neurons fire when a monkey observes an action it may imitate.

Note that this figure shows a monkey brain, looking to the

left.


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Neurons work together

--- in pathways, circuits, networks and maps.

A layer of pyramid-shaped (pyramidal) neurons in hippocampus. (Using a fluorescent

dye.)

QuickTime™ and aTIFF (LZW) decompressor


A common artificial neural network, called a backpropagation net, feeds back to its own input, adjusting connection weights to reduce errors. (Abraham,

TINS 2005)


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Neurons that fire in synchrony with each other.

Two separate electrodes are needed to record synchrony

between neurons.

When two competing images into the two eyes are interpreted as a single image in the cat brain, visual neurons recording the "seeing" eye show higher, synchronized voltages near 40 Hz. (Fries et al, TICS)


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Single neurons fire spikes; groups of neurons are usually

recorded as "field potentials," like the EEG.

The electro-magnetic field generated by tens of billions of neurons extends to the outside of the scalp. Scalp EEG picks up massive neuronal activity. Single

neurons fire single spikes

Single neurons fire single spikes

Group averages show field waves.

Group averages show field waves.

Sleep:

Waking:


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Neural net models can simulate some human functions.

This brain-based robot rides balanced on two wheels, using a Segway platform. It can play soccer --- slowly. Its neural net brain simulates the human cerebellum, using simplified neurons. Other versions of the Darwin robot series simulate other brain regions. All are run by brain-like neuronal nets with thousands of "neurons." Such models help to test out our detailed models of the brain at the level of cell assemblies.

(With thanks to Dr. Jeff Krichmar, The Neurosciences Institute, San Diego,

www.nsi.edu).

http://www.nsi.edu/


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Brain models can simulate simple human functions. Darwin VII

A brain-based robot, with video cameras for eyes, a microphone for ears, a grasper hand, and the ability to detect "tastes" from the electrical

conductiviey of objects.

With kind permission from the authors: J.L. Krichmar & G.M. Edelman, (2002) Machine Psychology: Autonomous Behavior, Perceptual Categorization and Conditioning in a Brain-Based Device, Cerebral Cortex 12:818-830. The Neurosciences Institute, www.nsi.edu

Retina Object Map

Auditory Motor Map

Notice that the "Retina" is picking up the visual markings on the blocks. Like the real retina, it only picks up colors

and "pixel" locations.

http://www.nsi.edu/


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Darwin VII before learning to associate a "good" or "bad" taste with a visually

distinctive block (parallel marks vs. round dots). Retina Object Map

Motor Map

Notice that Darwin VII "hears" its own sound when it grabs the

object to "taste" it.

Darwin VII's brain consists of neural maps, connected in the way they are in the real brarin. You can see four squares --- matrices of neurons with connections between them.

On the maps, yellow and red colors indicate higher neural activity. You can see the Retina, an Object Map (area IT), an Auditory map, and a Motor Map.



Auditory Motor Map


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Darwin VII after learning to associate a "good" taste with a visually marked block.

Note: Notice the improved efficiency of Darwin's association between the visual input and the rewarding "taste.' Darwin hasn't been told what to do, but learned by experience and

association between its neural maps, guided by "good" and "bad" tastes. Retina Object Map

Motor Map

Darwin VII does Hebbian learning (see Chapter 3), to learn objects, and to associate different inputs with each other. It has some 20,000 neurons, with a half million connections between them. It also has built-in instincts --- object-avoidance and tries to sample the taste of surrounding objects.



Auditory

To accompany Baars & Gage - Chapter 3 1 Chapter 3. Elsevier web materials.

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