Neurons at the boundaries of sensory areas are cross-modal

Via in vivo electrophysiology combined with sensory stimuli, Mark T. Wallace , Ramnarayan Ramachandran and Barry E. Stein found that

“at the borders between each of these domains [visual, auditory, and somatosensory cortex] a concentration of multisensory neurons was found whose modality profile matched the representations in neighboring cortices and that were able to integrate their cross-modal inputs…”

Here’s the article.

Attention influences perception

Really elegant study in Nature Neuroscience showing how attention (consciousness for you philosophers…) can modulate perception. Most previous work that I’ve seen has been about how attention changes response time but this study shows how the percept itself can change.

The neat part is that the experimenters found a way of assaying stimulus salience (contrast, in this case) without directly asking. It’s interesting to see how this “Holy Grail of Consciousness” is being scientifically deconstructed bit-by-bit with rather simple experiments. Check out the full article here or click below for the news & views.
Continue reading

Brain regions which process what you are doing vs. what you think you are doing

Daniel Moran, Andrew B. Schwartz, and G. Anthony Reina “…created a virtual reality video game to trick the monkeys into thinking that they were tracing ellipses with their hands, though they actually were moving their hands in a circle.

They monitored nerve cells in the monkeys enabling them to see what areas of the brain represented the circle and which areas represented the ellipse. They found that the primary motor cortex represented the actual movement while the signals from cells in a neighboring area, called the ventral premotor cortex, were generating elliptical shapes.”

http://news-info.wustl.edu/tips/page/print/652.html

Registry of standard biological parts

Today, I attended an interesting CBA talk on the MIT Registry of Standard Biological Parts. The basic premise is that molecular biology has elucidated enough about particular genes, proteins, promoters, etc. that we can start to make an inventory of these various “parts”. More than just a database, the Registry promotes the idea of reliable engineering with combinable components (think resistors and capacitors put together into larger circuits). This all sounds very ambitious and a bit idealized (especially if you’re a biologist) until you realize that they’ve actually done this already and built some neat, complex things (like a synchronized oscillator and a bullseye).

Though not directly related to neuroscience, this combination of biology and computation is very interesting. I encourage all of you to check out parts.mit.edu. It looks like they’re trying to make it as open source as possible, too.

For discussion: Is this the right approach to engineering with biology? What can be made more easily with biological substrates than with silicon?

IBNS Travel Award Applications Due February 16th

IBNS Travel Award Applications Due February 16th

A limited number of student travel awards will be available for this meeting. To qualify, you must be a student presenting a paper as first author at this IBNS meeting. Undergraduate, graduate and post doctoral students may apply. Applicants for these awards must be members of the Society, or apply for membership prior to the time the application is submitted.
Continue reading

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!)