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researResearch
Coding and the brain
Project Leader :
Claude Berrou
Department:
• Electronics
This fundamental research project aims to clearly identify, deepen and take
advantage of strong analogies that can be seen between the structures of the
cerebral cortex and those of modern error-correcting decoders, both turbo
and belief propagation types. This project is based on a connectionist vision of
information processing in which memory and computation are inseparable
and interact persistently.
With respect to work that might be carried out to bring together information
theory and brain biology, both in France and abroad, this project adopts an
original, bottom-up approach. Instead of starting from general statistical
considerations (entropy, channel capacity, etc.) to try to justify the choices of
nature in information processing, let us observe the « material » similitude of
these choices with modern decoders.
At the heart of this project is an obvious organizational and operational
similarity between the network of biological neurons, for example that of the
neocortical column containing thousands of neurons, and the decoder of an
LDPC (Low Density Parity Check) code. We are called upon by this similarity
to address the understanding of cerebral functioning by spatial-temporal
approaches that have proven themselves in the domain of error correction. In
particular, the properties of graphs and the importance of cycles in graphs
are at the heart of this study. Indeed various arguments concerning
informational nature, as well as the most recent observations of
neurobiologists, lead us to view the cycle as the fundamental support of
memory, reasoning and conscience. The cycle is also a graphic concept of the
highest importance in corrective coding/decoding. It was recently
demonstrated that a code constructed from an exclusively arborescent
representation (one not including cycles) could not be a good code. But
contrary to the cortex, cycle information propagation is not optimal, due to
correlation effects. This dilemma leads us to consider the construction of
original redundant codes whose code words are apparently systematically
associated with cycles and whose decoding should thus not be negatively
affected by correlation effects, since such effects should always be positive.
The work carried out in this project is part of a strongly reductionist vision of
the physico-chemical complexity of the biology of the brain. It seems to us
that the knowledge gained over the past few decades by neorobiologists opens
the door to information theory (coding, communication, graphs, etc.) to make
a considerable contribution to the understanding and imitation of cerebral
behavior. The principal observation that can be made today is the following: we
still do not know how information is carried, maintained and processed in the
cerebral cortex, despite all the work that has been carried out thus far in the
disciplines of neuroscience.
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