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Comment by CGMthrowaway | Hacker News Reader

fMRI is a step above dowsing rods. It's plugging a multimeter into an outlet and guessing what type and brand of appliances you are running in your house.

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Have you heard of time-domain reflectometry? A $20,000 multimeter could have the "impossible" feature you describe all but built in.

I was at a talk maybe 15 years ago in which the speaker gave pretty convincing evidence that given a time series of voltages you could learn a lot of things about what kind of appliances you've got running.

There are a lot of devices that have reasonably distinct patterns to their power consumption. Motors- especially well pumps, but also large central air fans and some others- are going to look very different from a microwave or vacuum cleaner or refrigerator, especially if you have time of day on your readings.

Constant lower draw devices- chargers, lights, speakers and such- are going to be harder to distinguish, though.

Turns out it's a (somewhat) active area of research.

https://ubicomplab.cs.washington.edu/pdfs/electrisense.pdf

https://www.researchgate.net/publication/266461208_Multimedi...

https://www.mdpi.com/1996-1073/14/9/2485

I'd say you're right about any given individual channel: the activation of a single voxel doesn't tell us much about all the fancy computation happening in that ~1 mm^3 of tissue.

But the pattern of activity of thousands of voxels across cortex does contain reliable information! And a decent amount of it too, at least in sensory cortices.

Try it with a crude task - eg finger tapping. It’s pretty convincing.

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