Saturday, 22 September 2018
 
  Home arrow Artificial Intelligence arrow A Brief Sketch of the Brain  
Main Menu
Home
About us
Email
Blog
Forum
Search
How To Order
Contact Us
Private Policy
Terms of use
Articles/Tutorials
Artificial Intelligence
Robotics
Products Categories
Robotics Solar Robotics

List All Products


Advanced Search
Product Scroller
JRT RP1073
JRT RP1073


JRT RP1068
JRT RP1068


JRT RP1093
JRT RP1093


L2988 Compact Motor Driver Kit
L2988 Compact Motor Driver Kit


JRT RP1079
JRT RP1079


JRT Shop
  New 
New
Top 
Top Ten
Special 
Special
Random 
Random
 
Robotic Arm
Robotic Arm

Avoider III
Avoider III


Robotic Arm
Robotic Arm

Scoutwalker III: Adept Two-motor Walking Robot
Scoutwalker III: Adept Two-motor Walking Robot


JRT RP1066
JRT RP1066


Download J Robotics's listed product's catalog. To download please click here. | For free E-Mail id like myname@jrt.in, register with us.  
A Brief Sketch of the Brain Print E-mail

What's the scale of things here?
The following lengths (from Posner p. 305) give approximate sizes for structures in the nervous system:

0.001 mm: synapses (tip of a connection between neurons)
0.1 mm: neurons (brain cell)
1 mm: local circuits (small networks of cells)
10 mm: maps (spatially organized topographic maps)
100 mm: systems (e.g., the visual system)
1000 mm: the central nervous system (including spinal cord)

How many things are we talking about?
Short answer: a LOT.
Long answer: Per cubic millimeter (mm^3), there are about 10^5 neurons and 10^9 synapses. For you computer types, that's about 2^16 neurons and 2^30 synapses. It's estimated that there are around 10^12 (or 2^40) neurons and 10^15 (or 2^50) synapses in the nervous system. A typical brain cell receives inputs from thousands of other cells, and the influence of each connection is 1-5% of threshold -- that is, only 1-5% of what the cell needs to respond.


How fast does the brain work?
Not very fast by computer standards. An action potential (i.e., nerve impulse) lasts about 1 ms (millisecond). Axons, the long output connection from a cell, come in two basic types: myelinated and unmyelinated. Myelinated axons have an extra layer of "insulation," which allows the action potential to travel about 10 to 100 meters per second. Unmyelinated axons are slower, transmitting at only about 1 meter per second. When the signal reaches the end of the line, it has to cross the synapse to influence the next cell; this process takes about 5 ms. The effect can last from a millisecond to many minutes, depending mostly on the type of the synapse. [Posner p. 339-340]

How are memories stored in the brain?
This is one of the great questions of neuroscience, and research has nearly converged on an answer. Short-term memories -- those which last a few minutes or hours -- may be stored in a variety of ways, including protein activation and inactivation within neurons, or simply cycles of neural activity. More important to uploading is the issue of long-term memory. It appears that long-term memories are stored by structural changes in neural processes. These changes include the number of branches a neural process makes and the number and efficacy of synapses. Byrne et al. present an excellent overview of recent work documenting these changes in Aplysia (a marine mollusc). There is currently no reason to believe that memories in humans operate by a different mechanism. [It may also be speculated that these same morphological characteristics are responsible for other aspects of personality, though this has yet to be demonstrated.]

OK, so neurons and connections, is that it?
Well, there's more in the brain than that. There are also various forms of "glia" cells (meaning "glue"), which serve mostly support functions. The most important of these, from a processing standpoint, are the astrocytes; astrocytes may affect information processing by regulating the neuronal microenvironment, by slow signaling mechanisms (e.g., calcium waves), or by other poorly understood processes. Also, there are all sorts of hormones and other chemical interactions in the brain which definitely do have an effect on the mind; these chemical interactions would need to be simulated for the upload to be accurate.
More Brain Facts and Figures are available from the University of Washington.

 
< Prev
JRT Videos

You need to a flashplayer enabled browser to view this YouTube video  

more videos....

Newsletter/Register

Advertisement

© 2018 J Robotics Technologies, India

Get The Best Free Joomla Templates at www.joomla-templates.com