A more synthetic approach to neuroscience (to complement the analytic approach)
large-scalecomplete behaviour
State-of-the-art• IBM Cognitive Computing (Synapse)
• Dharmendra Mohda
• 109 simple, spiking neurons (now 5x1011)
Mohda’s slide
Some friction
• "...tremendous historic milestone" Modha
• "...a hoax and a PR stunt" - Markram
• "It is highly unethical of Mohda to mislead the public in making people believe they have actually simulated a cat's brain. Absolutely shocking." - Markram
State-of-the-art
• Blue Brain project - Henry Markram (EPFL)
• 10^6 ‘realistic’ neurons
• Concern: “It takes the established principles in neuroscience combined with mountains of data, shoving it all together to see what emerges” - nerd-alert.net
IBM Blue Gene
Cortical column activity
Our recent attempt
• Spaun (Semantic Pointer Architecture Unified Network)
• 2.5 million neurons
• 8 different tasks
• Including basic perceptual tasks...
Eliasmith et al., Nov. 2012, Science.
With no changes to Spaun between tasks...
(8 tasks include: recognition, copy drawing, reinforcement learning, counting, serial working memory, question answering, RVC, RPM)
Bandit TaskDelay Approach Reward Return
Time (seconds)
Neu
ron
num
ber
Tria
l num
ber
Freq
uenc
y (s
pike
s/s)
How did we build it?
With the Neural Engineering Framework (NEF)
• A ‘neural compiler’
• Three principles
• General
• Unified
• Quantitative
Eliasmith & Anderson (2003) MIT Press
... and the Semantic Pointer Architecture (SPA)
• Specific functional claims:
• Working memory
• Action selection (BG)
• Motor/perception hierarchies
• Communication protocol:
• Semantic pointers
Eliasmith (2013), Oxford
Semantic Pointers• E.g. The pointer would be the activity of the top
level of a standard hierarchical visual model for object recognition
• This pointer can thensupport ‘symbol’manipulation
• It can also be used toreactivate a full visual representation
Serre et al., 2007 PNAS
SPA: Semantic Pointers• Semantic pointers are: Compressed, content-based
‘addresses’ to information in association cortices
• ‘Pointer’ because they are used to recall ‘deep’ semantic information (content-based pointer)
• ‘Semantic’ because they themselves define a ‘surface’ semantic space
Unified view
• Symbolicism
• Working with structure, SPs
• Connectionism
• Statistical categorization, SPs
• Dynamicism
• Brain/body dynamics, SPs & control
Still a long way to go...
...but I think the SPA/NEF/Nengo combination can help
(... btw, it’s a group effort, so everything here is open source and downloadable).
Further informationResearch, Papershttp://compneuro.uwaterloo.ca/
Nengo software, Tutorials, Demo videoshttp://www.nengo.ca
Spaun team: Terry Stewart, Xuan Choo, Travis Dewolf, Trevor Bekolay, Charlie Tang, Dan Rasmussen
CNRG lab: Eric Hunsberger, James Bergstra, Eric Crawford, Oliver Trujillo, Peter Blouw, Peter Suma, Brent Komer, Aaron Voelker, Youssef Zaky