neurodudes

In the September Nature Neuroscience, we have a promising new technique: Millisecond-timescale, genetically targeted optical control of neural activity.

I think several people have suggested doing something like this before but no one has actually done it. What they’ve done is genetically modified (by lentivirus, for those curious) ordinary hippocampal neurons in culture, adding the same photo-electric transducing protein — rhodopsin – found in photoreceptors. Yup. You heard me right. They’ve expressed a cation-channel-gating rhodopsin in ordinary hippocampal neurons. With an standard fluorescence microscope (Xenon lamp + Chroma GFP cube), they can photostimulate single action potentials (and sub-threshold depolarizations) in single neurons.

Now here’s my idea for bioengineers to take this to the next level: Add a second photosensitive protein tied to an inhibitory channel. Ideally, we would want total separation between the stimulating wavelengths for the two different (excitatory, inhibitory) channels. Now, you have a system where all neurons can be directly excited or inhibited with different laser lines. In other words, a network of neurons where all voltages can be fully controlled. Sweet!

This seems like a great tool to add to the existing arsenal of photostimulation techniques (like photoelectric effect-based light-on-silicon stimulation that was pioneered by Goda lab.) Here’s a question: Is this the end of multi-electrode arrays? In slice, we already have single spike detection with Ca-sensitive dyes from Yuste’s lab. Now, we have optical single spike stimulation. Perhaps MEAs will be relegated to the domain implantable devices. Regardless, I’m proud to see several of the authors are from Stanford! Read on for the full abstract. (more…)

This group in Japan has some cool goals.

The basic idea is to combine microfluidic plumbing with single neuron electrodes. Here’s their schematic:

Steve Potter, Jerry Pine and colleagues believe that a lack of normal input in high-density hippocampal cultures is the primary cause of synchronized bursting. By using MEA stimulation spread across several electrodes, they change the electrical behavior of the culture to show more dispersed spiking and less bursting. They suggest that these findings can be directly applied to epilepsy… interesting idea: epilepsy as a loss of normal cortical input to the epileptic focus. Click here for the entire article from this week’s J. Neurosci or below for the abstract.
(more…)

University of Florida has an Oct 21 press release about Thomas DeMarse’s work in hybrots, that is, cultured neurons interacting with a computer via an MEA to control an avatar in a simulated world. In this case, the neurons are flying a plane in a flight simulation program.

It looks from the press release that he has got the animat to actually learn to fly a plane (i.e. got input about the simulated environment and controlled a simulator joystick to keep the plane steady!

full article

Unfortunately he doesn’t describe what kind of learning rule/feedback was used, so I guess we’ll have to wait for the paper to see how much excitement is justified.

P.S. there’s also a lively discussion on SlashDot about this press release.