Where We are and Where We are Going
Ever wonder how we know where we are at any point in time, or how we move our bodies to just the spot we want them to be?
We do it so effortlessly, and with no real thinking we are aware of, it seems simply natural. But as with all functions, something has to direct them and make them happen,
Recent insights in neuroscience have revealed that the way the brain operates our motions is nothing less than astounding.
A recent review in Scientific American (Jan. 2016) reports that inside our brains are sets of neurons, individual cells, that each have the remarkable ability to map our space, and know where we are in it.
Where in the brain is our map-making centers?
These cells reside in a part of the brain at the level of our ears, deep inside the brain, in two structures- the hippocampus and the entorhinal cortex. The hippocampus is named after a mythic creature in Greece that had the head of a horse and rear of a dolphin, and seems to have the shape of a sea-horse. The hippocampus is where many of our long-term memories are formed. The entorhinal cortex is just in front of the hippocampus, and just behind the cells that receive signals from our noses to register the perception of smells, hence the word rhinal (or of the nose), in its name. It is the area of the brain that connects the hippocampus to the main cortex.
So much for the technicalities, the amazement comes from what the special cells in the hippocampus and entorhinal cortex do. To really appreciate what comes next, one has to stop a moment to consider what we are talking about are single, individual nerve cells knowing where you are.
What do the special map-making cells actually do?
The special cells come in two forms, at least- grid cells and place cells.
Grid cells fire only when one approaches the angle of a hexagon in space. This is worth explaining. The existence of grid cells reveals that our brain converts our space into flat sheets of hexagons. One on sheet the hexagon may be about one foot in length per side of the hexagon. Other sheets of hexagons created in our minds could be several yards in length per side of the hexagon.
Once the brain has laid a set of hexagons on the space around us, wherever we are, then the grid cells only fire when we walk to an actual angle of one of these hexagons.
This neat process allows the brain to know precisely in which direction we are moving, and how quickly.
A subset of grid cells only fires if one approaches the side of one of the maps' hexagons that lies along an actual wall, or divide, an actual boundary to the space on is in.
Another set of cells in the brain only fire if one moves in a particular direction, thereby allowing us to perceive, to know, what direction we are moving in.
Another set of cells is devoted entirely to firing only at set speeds of motion, allowing us to know how fast we are moving.
All these special cells combine to give as complete a picture as possible of where we are and where we are going. It is the combination of all this information that determines if one last special cell to be mentioned, fires. That cell is called a place cell, and it fires only when all sorts of conditions- where one is in the hexagon at hand, the direction of motion, the speed of motion, the colors and details of the space- come together to define an actual place. To me, this is the most incredible fact- there are such nerve cells in our brains that only fire when we are in an actual, real, place. It is as though one cell can actually, and does, have the power to recognize, in this case recognize a space or place.
Incredible.
Just to help understand all this a bit more, grid cells will fire whenever anyone approaches a corner of any hexagon mapped to any place the person is at. They fire when you are inside, or outside; in the bathroom, or bedroom; while you are home or away. But place cells only fire in specific places, hence the name place cells.
Space and memory
You may have noticed much of this mechanism takes place in or near the hippocampus, the brain's memory machine. There is no coincidence here. Once the brain has mapped a space you are in with its hexagons, and lined up the special place cells to fire in specific places, those patterns are kept in mind, placed in memory.
These areas of the entorhinal cortex that preserve place memory are often the first to go in Alzheimer's disease, explaining why getting lost out in the world is such a common and early experience when this dread disease begins.
BOTTOM LINES
The brain has incredible approaches to knowing where we are and where we are going.
It starts with mapping any room or place we are in with a set of hexagons, then tracks how we are moving in those hexagons. That and other information combine to allow single cells to remember any spot we have been.
It starts with mapping any room or place we are in with a set of hexagons, then tracks how we are moving in those hexagons. That and other information combine to allow single cells to remember any spot we have been.
The ability to know where you are and where you are going is extraordinary, the fact that much of this sense and perception is mediated by single, individual nerve cells is even more amazing.
We at Advanced Pediatrics hope everyone has a wonderful holiday, wherever your brain's maps may take you!
To your health,
Dr. Lavin
*Disclaimer* The comments contained in this electronic source of information do not constitute and are not designed to imply that they constitute any form of individual medical advice. The information provided is purely for informational purposes only and not relevant to any person's particular medical condition or situation. If you have any medical concerns about yourself or your family please contact your physician immediately. In order to provide our patients the best uninfluenced information that science has to offer,we do not accept samples of drugs, advertising tchotchkes, money, food, or any item from outside vendors.
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