Matt Faw says subjective experience is caused by a simulation in the hippocampus – a bit like a holodeck. There’s a brief description on the Brains Blog, with the full version here.

In a very brief sketch, Faw says that data from various systems is pulled together in the hippocampal system and compiled into a sort of unified report of what’s going on. This is sort of a global workspace system, whose function is to co-ordinate. The ongoing reportage here is like a rolling film or holodeck simulation, and because it’s the only unified picture available, it is mistaken for the brain’s actual interaction with the world. The actual work of cognition is done elsewhere, but this simulation is what gives rise to ‘neurotypical subjective experience’.

I’m uneasy about that; it doesn’t much resemble what I would call subjective experience. We can have a model of the self in the world without any experiencing going on (Roger Penrose suggested the example of a video camera pointed at a mirror), while the actual subjectivity of phenomenal experience seems to be nothing to do with the ‘structural’ properties of whether there’s a simulation of the world going on.

I believe the simulation or model is supposed to help us think about the world and make plans; but the actual process of thinking about things rarely involves a continuous simulation of reality. If I’m thinking of going out to buy a newspaper, I don’t have to run through imagining what the experience is going to be like; indeed, to do so would require some effort. Even if I do that, I’m the puppeteer throughout; it’s not like running a computer game and being surprised by what happens. I don’t learn much from the process.

And what would the point be? I can just think about the world. Laboriously constructing a model of the world and then thinking about that instead looks like a lot of redundant work and a terrible source of error if I get it wrong.

There’s a further problem for Faw in that there are people who manage without functioning hippocampi. Although they undoubtedly have serious memory problems, they can talk to us fairly normally and answer questions about their experiences. It seems weird to suggest that they don’t have any subjective experience; are they philosophical zombies?

Faw doesn’t want to say so. Instead he likens their thought processes to the ones that go on when we’re driving without thinking. Often we find we’ve driven somewhere but cannot remember any details of the journey. Faw suggests that what happens here is just that we don’t remember the driving. All the functions that really do the cognitive work are operating normally, but whereas in other circumstances their activity would get covered (to some extent) in the ‘news bulletin’ simulation, in this case our mind is dealing with something more interesting (a daydream, other plans, whatever), and just fails to record what we’ve done with the brake and the steering wheel. But if we were asked at the very moment of turning left what we were doing, we’d have no problem answering. People with no hippocampi are like this; constantly aware of the detail of current cognition, stuff that is normally hidden from neurotypically¬†normal people, but lacking the broader context which for us is the source of normal conscious experience.

I broadly like this account, and it points to the probability that the apparent problems for Faw are to a degree just a matter of labelling. He’s calling it subjective experience, but if he called it reportable subjective experience it would make a lot of sense. We only ever report what we remember to have been our conscious experience: some time, even if only an instant, has to have passed. It’s entirely plausible that that we rely on the hippocampus to put together these immediate, reportable memories for us.

So really what I call subjective experience is going on all the time out there; it doesn’t require a unified account or model; but it does need the hippocampal newsletter in order to become reportable. Faw and I might disagree on the fine philosophical issue of whether it is meaningful to talk about experiences that cannot, in principle, be reported; but in other ways we don’t really differ as much as it seemed.

5 Comments

  1. 1. SelfAwarePatterns says:

    I agree with Faw that simulations are a significant part of what we call “consciousness”. When considering this idea, it’s important to understand that we wouldn’t consciously perceive the mechanics of the simulations, just the results.

    So if I see a cookie and consciously decide to ignore my diet and eat it, the simulation of me eating the cookie isn’t part of my subjective experience. Nonetheless, under this theory, my brain runs a quick scenario simulation of it along with possibly one of me sticking to my diet, compares the emotional valences associated with each, and the valence associated with eating the cookie causes that scenario to win out.

    Of course, sometimes we do consciously decide to imagine scenarios. But I think in these cases, it’s the brain, in essence, running a simulation of the simulation. When that happens, our effort to intentionally think through the scenario does make it part of our experience.

    However, I’m not sure I’m on board with the central role Faw sees for the hippocampus here. In my mind, the simulations take place throughout the thalamocortical system, but are coordinated by the pfc (prefrontral cortex), where the results are delivered.

    The pfc makes much better sense for this role than the hippocampus, because we have a lot more neurological case studies for what happens when the pfc is damaged. It’s much easier to conclude that someone who’s had a full lobotomy (disconnection of the pfc) is no longer conscious than a patient like H.M., who lost his hippocampi but nevertheless retained a personality, albeit a disabled one.

    The hippocampus definitely has a central role in memory. It’s a crucial part of the supporting infrastructure, but I doubt it’s where the theater of subjective experience plays out. Again, it makes a lot more functional and adaptive sense if this happens in the pfc.

    In this view, subjective experience is communication. Communication from the perception and emotion centers in the brain to the action planning centers. If you think about it, how else could the action planning centers in the pfc do their job if they didn’t have that information flowing in?

    That said, I’ve only read Faw’s blog post so far and plan to check out his full treatment to see if the case for the hippocampus is more compelling than I’m currently… simulating right now ūüôā

  2. 2. David Duffy says:

    The most interesting thing in that piece is the stuff on visualisation in hemispatial neglect patients. The idea that predictive coding is used in multiple brain regions would suggest the virtuality is distributed, eg

    http://journal.frontiersin.org/article/10.3389/fpsyg.2014.01133/full

  3. 3. John Davey says:


    but this simulation is what gives rise to ‚Äėneurotypical subjective experience‚Äô.
    /i>

    How ?

    Alas, a typical “information-to-consciousness migration” process that is utterly glossed over. The trouble is that this alleged and frequently postulated migration – to consciousness states from ‘information’ states – is the entire question of consciousness. You can’t state how you think that information x “leads” to consciousness with discussing what “leads” means.

    And when you find what “leads” means, pick up a Nobel Prize.

    J

  4. 4. John Davey says:


    but this simulation is what gives rise to ‚Äėneurotypical subjective experience‚Äô.

    How ?

    Alas, a typical ‚Äúinformation-to-consciousness migration‚ÄĚ process that is utterly glossed over. The trouble is that this alleged and frequently postulated migration ‚Äď to consciousness states from ‚Äėinformation‚Äô states ‚Äď is the entire question of consciousness. You can‚Äôt state how you think that information x ‚Äúleads‚ÄĚ to consciousness with discussing what ‚Äúleads‚ÄĚ means.

    And when you find what ‚Äúleads‚ÄĚ means, pick up a Nobel Prize.

    J

  5. 5. Jorge says:

    I kinda like this, if for no other reason than the hippocampus’s role in episodic memory formation.

    If you’re going to create coherent memorable narratives, it makes sense that the hippocampus would have access to the whole of conscious experience to craft memories from it. I mean, I can think of other ways it might work, but that’s parsimonious and intuitive.

    This is ‘easy problem’ territory though, there’s still not a single insight into why meat shaped like a hippocampus “feels pain”.

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