Cortical Microcircuits and their Computational Functions
Saturday 13th December 2008
Organizers: Terry Sejnowski, Salk Institute, Tomaso Poggio, MIT
There are around 100,000 neurons under a mm2 of cerebral cortex
and about one billion synapses. Thalamic inputs to the cortex
carry information that is transformed by local microcircuits of
excitatory and inhibitory neurons. In recent years there has
been an explosion of discoveries about the anatomical organization
of the micrcircuits and the physiolgical properties of the neurons
and synapses that compose them. The goal of this workshop is to
explore the funcitonal implications of these new findings and in particualr
to attempt to characterize the elementary computational operations
that are performed in different layers of cortex.
Some of the issues that speakers will address include:
- How is the input from the thalamus able to dominate the cortex
when the vast majority of the synapses in cortex are from cortical
neurons and the thalamic inputs constitute less than 5% of the synapses
on the first layer of cells in layer 4.
- Is there a canonical microcircuit? How does it differ between
sensory areas and motor areas, between the early and late stages
in the cortical hierarchy, and in cortical areas that support working
- How is the gain of the microcircuit affected by top down
inputs from higher cortical areas through attentional control?
How are microcircuit with positive feedback stabilized?
- What do the intrinsic properties of dendrites contribute to
the computation performed by neurons?
- What is the relation between proposed operations for canonical
microcircuits such as gain control, normalization, tuning, soft-max? Can
one compare the ventral stream to the dorsal stream?
- What is the consequence of short-term synaptic plasticity on
transient and tonic cortical processing?
Chair - Terry Sejnowski
7:30 am - Rodney Douglas, (INI, Zurich) - Canonical cortical microcircuits
8:10 am - Thomas Serre (MIT) - Microcircuits for perception
8:50 am - break
9:00 am - David Heeger (NYU) - "Normalization model of attention"
9:40 am - Paul Tiesinga (UNC, Chapel Hill) - Microcircuits for gain control
Chair - Rodney Douglas
4:00 pm - Attila Losonczy (Janelia Farm) - Dendritic computation
4:40 pm - Terry Sejnowski (Salk/UCSD) - "Local balance on dendritic branches"
5:20 pm - Break
5:30 pm - Viren Jain (MIT) - "Progress and prospects for high-throughput reconstruction of neural circuitry"
6:10 pm - Bernie Widrow (Stanford) - "Mechanisms for cognitive memory"
- Rodney Douglas, (INI, Zurich) - Canonical cortical microcircuit
- Paul Tiesinga (UNC, Chapel Hill) - Microcircuits for gain control
- Attila Losonczy (Janelia Farm) - Dendritic computation
- Terry Sejnowski (Salk/UCSD) - Thalamic inputs to cortex
- Tomaso Poggio (MIT) - Functions of microcircuits
- Bernie Widrow (Stanford) - Mechanisms for cognitive memory
- Sebastian Seung (MIT) - Connectomics
- David Heeger (NYU) - Microcircuits for normalization