Augmenting Memory With A Neuroprosthesis

By Neuroskeptic | December 7, 2013 3:14 am

A new paper in the Journal of Neural Engineering describes Facilitation of memory encoding in primate hippocampus by a neuroprosthesis that promotes task-specific neural firing

The research – from Sam Deadwyler’s team at Wake Forest University (and funded by DARPA) really is pretty amazing – if it pans out.

Four Rhesus macaques were trained to perform a short-term delayed-match-to-sample memory task, involving remembering the position and shape of an icon on a screen, and then picking it out from a line-up up to 40 seconds later. The task is difficult. Even though the monkeys were trying hard to succeed, in order to earn a tasty juice reward, they made a lot of mistakes.

…until they got a helping hand:

hampson_mimo

An array of electrodes was implanted into the hippocampus, able to both record neural activity and stimulate it. Using a mathematical model called “MIMO”, the authors first determined the pattern of activity that was seen when each animal correctly performed each type of trial (“strong code”), and when they failed (“weak code”).

Then, by monitoring activity on a trial-by-trial basis, they were able to predict whether a monkey was going to succeed or not. If it was set for failure, they stimulated the hippocampus to reproduce the ‘correct’ activity pattern – they injected the “strong code” that was missing.

The result?

memory_boostThe MIMO stimulation (red line) improved memory performance compared to no stimulation (blue) and a ‘scrambled’ stimulation (green) containing no useful information, a crucial control condition. Interestingly, the scrambled stimulation did not impair performance. Information processing in the hippocampus must be fairly robust to ‘noise’. One for the computational modellers to ponder.

Two years ago, the same team reported the success of this system in rats. But implementing it in non-human primates is a big step up the ladder of brain complexity (although the anatomy of the hippocampus is fairly constant across species.)

Deadwyler et al have also published the results of a different neuroprosthesis in monkeys, one aimed at the prefrontal cortex. In that paper, the ‘helping hand’ helped the monkeys make the correct choice when selecting their response. This time, it was the actual encoding of memory that was boosted.

So that’s cool. A relatively simple algorithm was able to do the hippocampus’s job better than it did it itself. But I wonder, is this because the delayed-match-to-sample memory task is so artificial and repetitive – i.e. unlike the kinds of tasks that the hippocampus evolved to perform? Would a neuroprothesis be able to boost a monkey’s memory ‘in the wild’?

Which begs the really big question – how might this help humans?

ResearchBlogging.org
Hampson RE, Song D, Opris I, Santos LM, Shin DC, Gerhardt GA, Marmarelis VZ, Berger TW, & Deadwyler SA (2013). Facilitation of memory encoding in primate hippocampus by a neuroprosthesis that promotes task-specific neural firing Journal of Neural Engineering, 10 DOI: 10.1088/1741-2560/10/6/066013

CATEGORIZED UNDER: animals, dbs, science, select, Top Posts
  • http://neuroecology.wordpress.com/ Adam J Calhoun

    Do they report any impediments? Somehow with these things I always feel that, though they may be improving one type of memory, they’ve GOT to be screwing up the proper coding of something (possibly subtle)

    • http://blogs.discovermagazine.com/neuroskeptic/ Neuroskeptic

      Maybe the monkey was remembering something on the failed trials, just not the information it needed to do the task (e.g. maybe it remembered some random noise that happened in the testing room, the taste of juice, etc.)

      In which case, it might well be that the stimulation knocked out those incidental memories, ‘replacing’ them with task-relevant information?

      • Chris Cozby

        Agreed

  • Eric Shumard

    Resistance is futile.

  • John

    I don’t believe it. The green line has to be lower than a blue line with no noise introduced into the system. On the blue line you’ll have the pattern occurring from time to time. If this really works how can the green line not be worse? It makes no sense.

    There’s something very fishy here.

    • Wouter

      Doing some modeling myself, I can tell you that the difference between a organized and random neural network is fairly minimal; the difference is in the order of a percentage or so. In other words, the difference may actually be present in the data, but simply too small to be picked up.

      • John

        Then the effect of the organized is too big. 20%??

    • gjbloom

      Neural nets excel at filtering the noise out of a signal.

    • ESRogs

      “They were able to predict whether a monkey was going to succeed or not. If it was set for failure, they stimulated the hippocampus to reproduce the ‘correct’ activity pattern …”

      If they also only gave the scrambled stim when they predicted failure then it would make sense for the green line not to be worse.

      If they gave the scrambled stim even when they predicted success, then I would be surprised as well.

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  • http://blogs.discovermagazine.com Edwin Harnell

    “although the anatomy of the hippocampus is fairly constant across species.”

    Presumably this is because the hippocampus is a primitive part of the brain which hasn’t evolved much with time or across species?

    Could this technology be used to enhance the cognitive functioning of Alzheimer’s and Parkinson’s sufferers? My understanding is these conditions affect mainly the prefrontal cortex. I thought the hippocampus was part of the limbic system and was responsible for emotional reaction rather than task learning.

  • Eric Mankin

    This work has been going on for a long, long time in rats – here was the breakthrough. http://viterbi.usc.edu/news/news/2011/restoring-memory-repairing.htm

  • Neurofanatic

    It’s all about the translation! We can only understand noise and signals, when we understand the translations! prefrontal cortex has nothing to do with memory, rather only with millisecond sensitive signals! Such as… Pain, pleasure, etc. When signals received, translations occures, then we have memory, only then we have the basis of “learning”. This is useless, we are not capable of translating signals, let alone understanding them!

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About Neuroskeptic

Neuroskeptic is a British neuroscientist who takes a skeptical look at his own field, and beyond. His blog offers a look at the latest developments in neuroscience, psychiatry and psychology through a critical lens.

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