23 - Are There Still Traces? Memory and the Obsolescence of the Paradigm of Inscription

Summary

I

The most recent discoveries in contemporary neurobiology have revealed that no single memory centre exists in the brain where complete memories could be stored. In their book Memory: From Mind to Molecules, Eric Kandel and Larry Squire write: ‘Memory does not exist in a single site or region of the central nervous system’ (2008: 10). Memory occurs through a distributed economy of storage instead of being stocked in a single, localisable preservation site. There exist several memory systems, involving different parts of the brain, mainly the amygdala, the hippocampus, the cerebellum and the prefrontal cortex. It follows that memory itself is fragmented: scientists distinguish between declarative memory, episodic memory, semantic memory, procedural memory, to name only the best-known ones. The amygdala is involved in fear and traumatic memories. The hippocampus is associated with declarative and episodic memory as well as recognition memory. The cerebellum plays a role in processing procedural memories, such as the knowledge of piano playing. The prefrontal cortex is involved in remembering semantic tasks. All these memory systems work together and collaborate within what is now called the ‘global neuronal workspace’, but they remain different in their specificity. Therefore, they can also be dissociated and function independently from each other. Brain diseases show the extreme consequences of such dissociations. Injuries to the hippocampus area, for example, leave the patient unable to process new declarative memories, even if they can still remember information and events that occurred prior to the wound or surgery.

Another striking fact is that memories are not encoded as images. They do not have any material presence in the brain, nor leave any mark on neural connections. They rather produce modifications of the forms of these connections. Repeated neuronal activity leads to a modification in size and volume of the connections. For a long time, memories were said to imprint the connections, like a writing stylus on a wax tablet. Such a model has now become obsolete. The substitution of plasticity – change of form – for inscription and trace constitutes one of the fundamental shifts in the contemporary neurobiology of memory. Conceptualising the obsolescence of the writing metaphor has become one of the most urgent philosophical tasks.

Is such a shift sufficient to challenge the concept of trace, though?