Wednesday, March 3, 2010

Manifolds of the Visual Brain

Remember the first time you learned to ride a bike? Or your first trip abroad? Our most precious experiences are retained in the form of episodic memories, or autobiographical memories. Episodic memory is also sometimes referred to as “auto-noetic” or self-knowing in the sense that you know or are aware of remembering. Dr. Endel Tulving, a research scientist at the Rotman Institute in Toronto and one of the principle founders of the study of episodic memory suggests that this is what makes this form of memory unique. Human memory is made up of all different kinds of systems that interact with one another across a vast and complex network. While we will be talking about single components of memory it is important to keep in mind that remembering is a highly integrated process, and does not originate from any one point in the brain. In other words there is no central perspective from where we (the subjects) are looking at a particular memory or episode. The very idea of the subject is challenged by the simultaneous presentation of past and present of emotion and material world. “Monadological points of view can be interlinked only on a nomad space.”[i](p.494) Memory is a patchwork or collection of our various experiences, which reflects on the very nature of the human subject. When the Buddha went to seek enlightenment he clothed himself with the various shreds of garment he found on the dead in the charnel houses. The sewing of the various scraps is symbolic of the way in which the universe comes together and also represents the act of renunciation from worldly things and the self. Because of the inherent characteristics of episodic memory it is easier to conceptualize it as curved space, a non-Euclidean space-time.

I will elaborate further. One of the core kinds of memory found in episodic experiences is visual memory. While there are four primary kinds of visual memory stores, ranging from low to high level (a function of greater content capacity and temporal longevity), as far as information rich images are concerned we are interested in visual long term memory (VLTM). VLTM is like the workhorse of the memory stores able to retain more or less accurate information for more than 7,000 pictures, including their associated objects. Contrast this with the visual temporary memory system or the visual cache, which holds up to 3-4 serial items. This number is based on our capacity for detecting changes among an array of objects. Furthermore the temporary memory system is volatile and prone to displacement. Tests by Gajewski and Brockmole[ii] (p. 21) have shown that there is no indication of a learning curve on later change displacement trials in spite of repetition of certain color-shape-location combinations. In topological terms one might say that the space-time of temporary working memory is characterized by a lack of continuous function, if we look for example at the way it quickly reaches its capacity limit and then discards information. In Deleuzian terms it does not distribute continuous variation well; it lacks that property of smooth space that forms the basis for “rhythmic value”. (Deleuze, p.478) The space is modular and broken, interrupted again and again by new memories that are then cast out creating “jumps”.

VLTM on the other hand, displays characteristics of smooth space. What makes VLTM interesting and unique is not just the fact that it has a high storage capacity, but in the way it functions as a system. Already what is different is that VLTM accumulates or collects objects and scenes. It operates as a continuous function of visual memory over time and appears to have a particular directionality, a kind of curve. This is evinced by the robust network of interactions that occur in and around VLTM, which begins by being consolidated by the hippocampus in conjunction with TE in the temporal cortex (an advanced visual perception area)[iii]. VLTM is based on the power of repetition. When we remember episodes from our past we are re-experiencing events and reinforcing particular memories. It also allows the memory to make associations with situations in our present. The hippocampus is not only the control station for visual memory, but the meeting point for all kinds of sensory modalities, a ‘haptic’ space par excellence. Over subsequent repetition the image, scene or experience can be consolidated and not only in the hippocampus but potentially in other areas as well, like the cerebral cortex. This is known from studying patients with hippocampal damage. The patients had difficulty retrieving information from the last 10 years, but could for example remember things from their childhood. Therefore repetition of memories appears to be the key to the longevity of VLTM: “It is free action, however, which by its essence unleashes the power of repetition as a machinic force that multiplies its effect and pursues an infinite movement. Free action proceeds by disjunction and decentering.”(Deleuze, p.498)

Episodic memory is a decentralized configuration of our past experiences. It connects thoughts, impressions, emotions and images with a “matter-flow” that is almost never ending for a being existing in time. Consciousness is perpetually making infinite statements. As we know the past does not simply get superseded by the now, but transforms into it, the outer and inner worlds being homeomorphic to one another. We can for example learn increasingly more about objects on successive views. On another level it tells us about the mind’s flexibility in traversing various topological spaces. Within consciousness the objects we have experienced do not simply remain dormant, but interact with one another forming new relations, as in dreams or when we create art. These memories in turn are re-experienced (in the same perceptual area where they were first formed) over and over again and in such a manner enter into relation with the world and are transformed by it, which negates the notion behind Euclid’s fifth postulate which assumes that two straight lines, meet in at most one point. In the realm of consciousness this does not hold true. Instead, what we witness in the domain of memory is a curved space-time.

Caldwell Lever

[i] Deleuze, Gilles, and Guattari Felix. A Thousand Plateaus: Capitalism and Schizophrenia. University of Minnesota, 1987.
[ii] Brockmole, James R. The Visual World in Memory. Hove [England]: Psychology, 2009. Print
[iii] "Ars Memorae." KINO BRAIN. Web. 03 Mar. 2010.

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