The Hippocampus Encodes Distances in Multidimensional Feature Space

A key question in neuro-science is whether its spatial coding principles also provide a universal metric for the organization of non-spatial information. Initial evidence comes from studies revealing directional modulation of fMRI responses in humans [6, 7] during navigation through abstract spaces and the involvement of place and grid cells in encoding of non-spatial feature dimensions [8]. However, a critical feature of a map-like representation is information about distances be-tween locations, which has yet only been demonstrated for physical space [4, 9]. Here, we probe whether the hippocampus similarly encodes distances between points in an abstract space spanned by continuous stimulus-feature dimensions that were relevant to the acquisition of a novel concept.We find that, after learning, two-dimensional distances between individual positions in the abstract space were represented in the hippocampal multi-voxel pattern as well as in the univariate hippocampal signal as indexed by fMRI adaptation. These results support the notion that the hippocampus computes domain-general, multidimensional cognitive maps along continuous dimensions
https://www.cell.com/current-biology/pdf/S0960-9822(19)30205-2.pdf

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could hippocampus encode distance as a time sequence?

No matter the dimensions, if an agent wants to travel from a point to another, it needs to choose a path. Then if we put the path on a timeline, it is one dimensional. By comparing the current path (g->e) to memory (g->e->f->c), the remaining distance is also clear (f->c).

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Does anyone real plan a path or is it landmarks, directions, and distances?

This article from Buzsaki and Tingley seems relevant to this discussion.
Distance and duration are the same from the brain point of view.

Space and Time: The Hippocampus as a Sequence Generator

The current conceptual framework in neuroscience is based on the space and time
ideas of classical physics. However, in contemporary physics ‘there is no longer space which
“contains” the world, and there is no time “in which” events occur’ [4]. We suggest that
neuroscience requires a similar update in paradigm. When the concepts of space and time are
scrutinized, they turn out to be mere human-invented terms conveniently classifying events of
the world, rather than independent entities. At the experimental level, we consider that
conceptualizing the hippocampal system as a device that computes space and time fails
to account for many experimental observations [5] because the hippocampus may be ‘blind’
regarding the modality of its inputs. Whatever information is presented to it, from whichever
parts of the neocortex, it activates the same computational algorithms. Thus, the specific terms
that we tend to assign to generic hippocampal computation may reflect largely the experimental
conditions and the engaged neocortical inputs rather than an internal computation of space or
time

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I mean to illustrate it more as a storing instead of planing a path. Landmarks, directions and distances are helpful too. For example when travel from (g -> e), g and e are landmarks. two points confirm a direction. The effort travel from g to e is distance.

By further composing such simple movements between two closest points and put them on a time line, we then obtain a longer distance.

In this way of storing a distance we only need to record the spatial relationships between 2 closest points.

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Maybe is neither time or space which encodes the other. Could both rise from something more generic that can be called “action” or “movement”. We as all other animals are sensory-motor creatures. There-s this continuous stream of sensations we have, which demand certain actions to do which in turn change the sensations and so forth. We-re always on the move. When we walk, when finger swipes the cup, when our body seems motionless fovea moves across the view, when eyes are closed thoughts are felt and move themselves. From waking up to falling asleep is all this “action” in between, which later we learn that some of it is “time” and some of it is “space”, and rest of it is everything else. The sense of linear “size” of anything might be encoded by how much “streaming” was it (can be) filled with.

Or we might as well primarily encode “speed” as a felt rate of how fast the sensory-motor stream changes from which both space and time are derived.

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I don’t want to sidetrack this discussion, but I think of time and movement as extremely similar when it comes to neural representations. I talk about it here and here.

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I think time is more like a container and actions are entities in it. They work together to represent a piece of information. Like we could interpret walking as a sequence of neuron firings.

If that were true, it would be impossible for me to play out two actions simultaneously using different timescales, which musicians do all the time.

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Action pool = {A,B,C}
Time x = [A,A,{B,C},{A,C},C]

If two actions could be done at the same time, then it is recorded as happening at the same time or a close time interval. Maybe I misunderstand your reply in a different timescale. Could you further explain that?

When you said “time container” I don’t think I understood you. I thought you were saying that movements were defined together in some type of time context, and cannot be mutated in time individually.

There is a motion in my brain (you might call it an affordance) associated with hitting a drum with a stick. I can play this affordance at any speed. I can hit the drum quickly or slowly by warping the time of the motion.

I also have an affordance associated with stomping on a bass drum pedal. This is a completely different affordance, associated with different sensory areas, but I am able to play this motion at different time scales as well.

I can play both these affordance sequences in time at different timescales simultaneously. This is tricky for some people, but drummers do this all the time (esp. jazz drummers).

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This is a really interesting discussion, and as a musician I’ve thought a bit about it too.

In the case of the jazz drummer, intuitively it seems that there’s an initial amount of practice that allows them to multitask (merge the affordances) at all, then perhaps a smaller bit of learning or reinforcement each time there’s a new combination of speeds.

I’m sure you’ll agree, but I don’t think your attention will ever continue coordinating two different time scales without learning a new affordance which is the combined actions at their current relative speed.

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And it takes time and repetition to lock in the association between the two original child affordances at their respective scales into the parent rhythm affordance.

This is like learning a new complex object. Again, affordances and objects should be compared very closely as we build out this vocabulary.

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Just throwing a hypothesis here, but:

You are probably aware of the gaze heuristic: (example from wikipedia) a baseball catcher using the gaze heuristic observes the initial angle of the ball and runs towards it in such a way as to keep this angle constant.

Couldn’t a similar process be used to “warp time” so that the drumming motion is acted upon at the right speed?

For example, the drummer somehow moves his attention to where and when the stick should be (not necessarily his physical gaze; it could be performed in “the mind’s eye”), and the brain uses an adjusted gaze heuristic to adapt the motion accordingly?

It does not feel like that when you are playing.
It is all in the cerebellum - muscle memory.
What you seem to be learning is how to call up the learned pattern.
In the early stages of cognitive control it is slow and clumsy. as the cerebellum learns the sequence it becomes automatic and practiced. For combination patterns the cortex has to learn to hook up with the learned sequences that are automatic, making an new combination sequence.
It is just about the same thing as typing - after you learn where the keys are you don’t have to look anymore and you reach over to the control keys mostly without thinking where they might be. Typing words eventually becomes mostly automatic as you learn to string the letter sequences together. There comes a point where even the spelling of the words is automatic and you don’t really read the source material.
When I am at the keyboard learned fingering from practice learning scales kicks in automatically and my hands seem to move into the correct positions on their own. Seriously, sometimes while I am playing or typing I notice that my hands seem to be off doing there own thing and I am just along for the ride.
None of this stuff matches up with the gaze control thing you are describing.

As a side note - there is no royal road to learning muscle memory - it takes a lot of repetitions. About the only thing that you can screw up is getting sloppy early on trying to force speed and not precision. Then you learn the sloppy moves and not the precision as you do automatically add speed.

BTW: if you are trying to learn music use a metronome. It is a pain in the neck for the added complication when you are trying to learn. It is still easier than trying to add it in later when you have formed bad muscle memory timing.

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