Homeland Security Commissions LED-Based Puke-Saber

E++99 writes "Homeland Security has contracted with Intelligent Optical Systems, Inc. to develop an "LED Incapacitator," a nonlethal weapon consisting of a large flashlight with a cluster of LEDs capable of emitting "super-bright pulses of light at rapidly changing wavelengths." Sounds innocuous enough... until they they shine "the evil color" at you and you start puking! A working prototype has been completed, and they will soon be putting it through its paces. Homeland Security hopes to give it to Border Patrol agents and National Guardsmen by 2010."

Comments

Re:So I'm confused here...

[Ungrounded Lightning]

They're probably referring to pulse repetition rate (1/frequency) when they say "wavelength".

Right after a neuron fires it "rearms" the membrane by pumping ions across it. In time sequence its sensitivity varies smoothly through:
  - The absolute refractory period: Nothing can fire it.
  - The negative afterpotential: It can be fired but it takes extra stimulus.
  - The positive afterpotential: It takes LESS than the usual amount of stimulus to fire it.
Then it returns to its normal, resting, sensitivity.

The sensitivity slope may be an artifact of the ion pumps and channels, but it appears to function as a mechanism for encoding the strength of a stimulus as a pulse rate.

This has a side effect: If a nerve is given short pulses of stimulation with a spacing corresponding to the length of time between a stimulus that fires it and the peak of the positive afterpotential, once it fires once it will tend to continue to fire in synchrony with the pulses from then on. If you have a bundle of such nerves with similar timing and all affected by the stimulus, each additional pulse picks up additional nerves and phase-locks them to the stimulus. Within a few pulses most of the fibers in the bundle tend to be firing rapidly and in unison.

You can see this with a strobe light with a variable repetition rate. Run it slow and you see distinct pulses - a flicker. Run it fast and you see a continuous light - the pulses have fused into a continuous response. But run it near the "flicker fusion rate" boundary and you get a lot of weird visual effects - notably flickering rainbow colors across the neighboring (or entire) visual field that tend to enhance and obscure the actual image with a flickering, undecipherable, psychedelic-poster version of itself.

You get colors other than those of the actual source (if it is colored rather than white) and effects in other parts of the visual field than the actual strobing light and things it is illuminating. This is because nerves for parts of the eye that would not normally be stimulated enough to trigger by this light (if it were non-strobing) still become entrained when they happen to be in a positive afterpotential period when a blink occurs.

(By the way: Don't try this if you're epileptic. It can produce a seizure. Indeed: Some people discover they're epileptic when they are exposed to such flickering lights.)

One speculation about the hypothetical "brown note" was that infrasound at a positive-afterpotential repetition rate matching that of nerves controlling the intestines might force peristalsis in the colon or trigger the appropriate reflexes for defecation. (It might be interesting to retry the debunking experiments with a train of narrow high-pressure pulses, approximating impulses, rather than a sine wave. B-) )

This flashlight appears to be attempting a variation of the same effect. By entraining the nerves of the visual processing responsible for locating onself in space and/or ones motion, it could create a visual illusion of movement that doesn't match the signals from the inner ear and the muscle-position sensors. A mismatch among these three systems produces motion sickness, nausea, and vomiting.

This reflex appears to be a defense against ingestion of neurotoxic poisons (such as those in some mushrooms and food-poisoning bacteria), using their disruption of the complex navigation system as an early warning and attempting to eliminate them from the digestive system before enough are absorbed to disable a critical system and kill the victim.