Philosophy and Memory Traces: Descartes to Connectionism (review)

John Sutton. Philosophy and Memory Traces: Descartes to Connectionism (Cambridge: Cambridge University Press, 1998). Pp. xiii, 372. $69.95 cloth.

John Sutton, a Postdoctoral Research Fellow in the School of Philosophy at the University of Sydney, has written an intriguing and well-researched book that defends two theories of autobiographical memory: one is an historically honored theory of memory traces treated as dynamic patterns of fleeting animal spirits and the other is the very contemporary theory of connectionism in which memories are stored only superpositionally (i.e., many memory traces are piled or layered in the same physical system) and reconstructed rather than reproduced. Both theories reject the static archival metaphors. Sutton argues that the contemporary theory finds its roots in the older one. He quotes Karl Lashley to the effect that a mere substitution of "nerve impulse" for "animal spirit" and "synapse" for "brain pore" results in a theory of learning (and presumably of memory, too) as change in the resistance of synapses. Modern neuroscientists and memory theorists, Sutton claims, look repeatedly to Descartes, the father of modern philosophy, for inspiration.

The book, historically anchored, is divided into four parts. Part I deals with animal spirits and memory traces and is dominated by the author's long, rereading of Descartes' dynamic physiology of memory; Part II deals with, amongst other things, English responses to Descartes' theory of memory, including John Locke's neurophysiology of the self; Part III and Part IV deal with connectionist models of memory traces and with such contemporary concerns as the catastrophic effects of superposition, truth in memory, and the difficulties of cognitive control over mental contents.

Let us consider the first model mentioned above. Descartes, in April 1630, wrote to Marin Mersenne that he was studying chemistry and anatomy simultaneously. L'Homme, translated as Treatise on Man, was the result of these studies. Although the work was published in the l66Os (with several printings), it was almost complete by July 1633. Upon hearing of the condemnation of Galileo, Descartes prudently chose not to risk antagonizing the Church by publishing Le Monde, of which L'Homme was a part.

L'Homme describes a soul-less world in which earthen machines imitate our bodily functions. These machines are animated, and they dream. These Cartesian automata cannot only walk, breathe, sleep, and wake, but also can nourish themselves and reproduce. They also have capacities of sensation, memory and emotion. Thanks to God's workmanship, these machines accomplish all these tasks by the whooshing of animal spirits shaking through brain tissues, these spirits constantly undergoing sifting, filtering, and sieving in the textured, porous net, forming and retracing patterns across the inner surfaces of a filamentous mesh. These animal spirits connect the deepest interior, the pineal gland, to the world in numerous ways.

In the section of L'Homme on memory, Descartes explicitly defines ideas as impressions or figures which animal spirits trace on the surface of the pineal gland as they leave it. These idea-impressions derive either directly from sensory impressions or from imagination as well as several other internal causes. Whatever their source, traces of these idea-patterns are carried by spirits flowing from the gland and then imprinted on the internal part of the brain, which is the seat of memory.

Descartes also sketches a theory of recall or retrieval. Animal spirits leaving the gland move through ventricles toward different regions of the brain substance. The pattern of the pores through which the spirits flow constrains the patterned flow of spirits, and the pattern itself is altered over time by the differing motion of the spirits. The patterns are not stored faithfully but are retained in such a way that they play a role in recreating the idea on the surface of the gland. This is representation without resemblance: patterns are stored only implicitly and are not maintained in exactly the same form throughout the interval between experience and...