Inferring cellular networks using probabilistic graphical models

This week’s Science has a nice introductory article (but with some mathematical detail) on using probabilistic graphical models to model cellular networks. Even for those of you who already know the formalisms (Bayesian networks, HMMs, etc.), you might find the recent biological applications discussed interesting.

Also, there are several other mathematical biology articles in the issue, including a review on evolutionary game theory.

Two new Hebbian rules in vitro

Mu-Ming Poo’s lab (which in 1998 found a very impressive result in hippocampal culture where excitatory synapses are potentiated when a Hebb-like protocol is used on the pre- and post-synaptic cell) has recently added two new Hebbian rules also found in hippocampal cell culture.

The first one applies to inhibitory hippocampal synapses (Neuron, Aug 2003) and the second one applies to spike trains in the mossy fiber pathway (Neuron, Feb 2004). The relative spike timing between the pre and post cells results in different amounts of potentiation/depression depending on the synapse type.

Some questions: Are there many different STDP rules? Or, are we missing the bigger picture (ie. a more general rule) of which these are all only specific examples? (Remember, this is just in hippocampus!)