Category Archives: proprioception

Memory

I was riding the NYC subway listening to my iPod the other day when it ran out of batteries (hard to relate to such an experience I know). I was a bit vexed because I had Massive Attack’s “Lately” stuck in my head and really wanted to scratch that itch. I realized that by focusing on the song, I was able to produce a damned good internal manifestation of it. I instantly tried specifically to do the same with a visual image, Max Ernst’s work (The Elephant Celebes, 1921) , but I could only remember object positions and placements; if I focused I could recall the pleasing quality of soft swaths of dark gray with silvery white punctuations that make up the central figure of the canvas, but never a detailed, full image. Perhaps some people can summon perfect pictures of a loved one’s face, but personally I’ve never been able to do that; only by relying on some other form of memory like a happy event am I able to better recall faces. I am explicitly, however, trying to avoid such considerations because this is one of the classic problems in confronting human memory, it’s capacity and quality are completely contingent on context. Despite all that is known and available to read on this subject, my inward exam led me to think about memories of unimodal (one sense at a time) sensory experiences in general.

I am really treading on thin philosophical and scientific ice by using introspection as my main mode of exploration, but this is meant to be neither of those things, merely thought provoking. Because this is such personal territory, it’s obvious that there will be some variation from person to person, for instance, in the extreme, a man blind from birth will find it decidedly impossible to recall any visual image, and can probably recall audio better than any person with sight. This person to person variation may have something to do with inherent differences in brain structure, including those completely lacking sensory apparati. So before I do a little run down of the various sensory systems, allow me a digression, starting from auditory stimuli, about brains that may facilitate the discussion to follow.

Music isn’t a very general example of an auditory stimulus, and this may have something to do with the fidelity of the remembered experience. There are a few factors which immediately come to mind that might be relevant: (1) the amount of cortex devoted to representing the type of stimulus in question, and (2) the involvement of mirror neurons, (3) the temporal quality of music. The Cerebral Cortex as it is “properly” referred to is the outermost few millimeters of the brain of higher organisms. The wrinkled quality that a brain has (if you’ve ever seen an image of one) is thought to be a way to increase the amount of cortex. This is where the brain does its most complex information processing. It is here that one can find single neurons (brain cells) which respond* to the various senses in such complex ways that single cells will react best when you are looking at a picture of Bill Clinton versus, say, a car or your grandmother. Mirror Neurons are wonderful little devices in your head which respond when you perform an action and when you observe another individual performing the same action. For example if you reach out and pick up an apple, the same mirror neuron will fire no matter how you do it. If you use a set of tongs for instance or daintily pick it up by the stem, and the same is true of the observed act, so that it seems mirror neurons encode intention of action. They’re very important for social interaction and learning and a host of other things, and they probably deserve their own post, but for now they are at the service of my argument about music and paintings.

The amount of cortex devoted to vision far outweighs any other sensory modality, certainly the visual cortex is larger than the primary auditory cortex. So it may simply be the case that it is more difficult for memories to light up all of the various parts of the visual cortex that are necessary to generate a truly accurate experience of sight.

When you hear somebody speak, mirror neurons potentiate, that is to say they make ready to use and facilitate the use of, the parts of your brain used for vocalising. This even goes so far as to provoke measurable electrical responses in the muscles of ones throat. When you watch somebody prick themselves it is thought that the mirror neuron system contributes to any sensation of pain or touch that you might experience as a result. It may thus be that when one is listening to music with singing, the mirror neuron system strengthens the auditory cortex’s memory based activity.

As to the temporal quality of music, this just doesn’t seem that relevant. I’m no more likely to be able to remember a series of images (unless it’s the final frames of Trufautt’s “The 400 Blows”) than I am to remember a single image.

Now, let’s see if these two ideas tell us anything when we try to examine other senses. Let’s consider the following 8 senses (What happened to five you ask? Well we need all these categories because the last three don’t really fit into the first five.). They are organized roughly by the amount of cortex devoted to them.

  1. Vision
  2. Somatosensation (touch)
  3. Audition
  4. Proprioception (muscle movement, posture)
  5. Gustation (taste)
  6. Olfaction (smell)
  7. Vestibular (balance, orientation)
  8. Interoception (hunger, thirst, drowsiness, air hunger, etc.)

This seems to immediately invalidate the suggestion that the amount of cortex devoted to a modality is what’s relevant. I have a very difficult if not impossible time remembering the experience of eating duck at WD-50, and yet the gustatory and olfactory cortical areas combined are smaller than the primary auditory cortex. As to the involvement of mirror neurons, it is incredibly difficult to asses. This is because one can’t really activate the mirror neuron system except by the use of vision or audition, so its potential utility in enhancing other unimodal memories is essentially nil. It might, however, facilitate the memory of a great LeBron James dunk or a beautiful Alvin Ailey dance piece. Despite this difficulty, it still seems to me that there is something extremely special about music. If I try to remember a series of isolated noises that I’ve heard it doesn’t even really make sense. I can think of specific sounds and noses: my fan blowing over my body on a hot summer night, a newer subway car’s increasing frequency whine as it picks up speed out of the station, a fluorescent bulb’s hum in the lab where I work. The problem with all of these is that I am unable to call these up without the associated visual experience as well, and then we’re back to the context/multi-modal issue. We must consider the possibility that our ability to both hear and make sounds facilitates a mirror neuron based enhancement of all music, vocal or otherwise; many instruments produce sounds well within the range of frequencies that we produce even if we can’t match their spectral qualities. I would really like to know if anybody out there feels that they have some sort of different experience of memory to the general one I’ve described here, or if they have theories of why we might perceive things in this way.

* I know respond is a weighted word, but I’ve got to cut this increasingly reductionist explanation off somewhere, if you’d like an explanation of what I mean by “respond” please email me and I’ll be happy to oblige.