In the last few decades
neuroscientific research has significantly advanced our understanding of
learning and memory. In Synaptic Self, LeDoux provides an overview of
this research and demonstrates how it sheds light on the relationship between
our sense of self and the ever-changing mass of neurons on which we depend. The
scope of Synaptic Self is quite broad, beginning with the question “what
is a synapse?” and ending with the question “who are you?” The lion’s share of
the book, however, is devoted to an historical and conceptual introduction to
neuroscience and its relationship to cognitive science, psychology, and
philosophy of mind. The book also discusses brain development, learning,
memory, emotions, mental illness, and consciousness. In fact, the book is
sufficiently informative in these areas to serve as a supplementary text for
suitably focused post-secondary courses.

Throughout Synaptic Self
LeDoux retains a focus on explicating the role of the so-called limbic system
in perception and cognition (LeDoux argues that the term “limbic system” is
antiquated). He describes in detail the various structures and
mechanisms underlying its influence on our conscious and unconscious life and
argues that emotional processing is able to influence what is viewed as “the
facts” in any given situation. Only in the final chapter does LeDoux “bite the
bullet,” as he says, and attempt to explain in what sense it is that we are our
synapses. In order to make sense of his assertion LeDoux needs to demonstrate
how it is that a coherent and seemingly stable self is sustained by an
inherently fluxional landscape of potentially independent neurons. In other
words, he needs to explain how it that our neurons are able to cooperate with
each other in bringing about our everyday experience of the world.

 Briefly, he argues that the necessary neural coordination can be
understood in terms of seven principles, which can be summarized as follows: 1)
Since the various brain systems experience the same world they are in a
position to cooperate with each other in rendering comprehensible wholes. 2)
Cooperation is realized at a neural level partly in terms of the formation of
synchronous activity both within and across brain regions. 3) This kind of
coordinated neural activity is further enhanced by the release of
neuromodulators from groups of nuclei in the brain stem and hypothalamus. Such
nuclei have fibers that project diffusely throughout the brain. Whenever
anything significant occurs they fire, releasing neuromodulators
that selectively enhance (or inhibit) the
synaptic transmission of whichever neurons happen to be active when they
are released. In this way also coherent systemic patterns of
activity are encouraged to form. 4) Augmenting the roles synchronous firing and
neuromodulators is the view that certain regions of the brain are simply
designed to integrate information from various neural subsystems. Exactly how
these convergence zones perform tasks of integration is largely left up to the
reader to imagine. 5) So far the neural coordination has all been bottom up,
but LeDoux also invokes the organizational potential of thought – a process
known colloquially among materialists as “downward causation.” The existence of
reciprocal connections between areas like the prefrontal cortex and portions of
the limbic system provides pathways by means of which thinking, embodied in
patterns of neural activity, is able to explicitly modulate bottom-up
processing. As a result, thought is another powerful way through which the
brain coordinates its activities and generates experiential coherence. 6)
Portions of the limbic system, on the other hand, are also able to transmit, as
opposed to simply modulate, patterns of activity up to the prefrontal cortex
effectively informing working memory as to the nature and significance of the
objects or ideas under consideration. 7) Hence, top-down and bottom-up systems
reciprocally reinforce each other to coordinate the emergence of focal
consciousness and to maintain a coherent and functional self. These seven
principles, when read in the context of the book, provide the reader with a
basic understanding of how various neural structures and mechanisms cooperate
in the emergence and maintenance of selves.

LeDoux’s focus on the role
of emotional processing is important and timely. Ultimately, however, he bites
off more than he can chew. Leaving aside for the moment the vagaries of
understanding how convergence zones work, one problem that receives very little
attention is the problem of how we are aware of anything at all. Whatever else
a self is, it is something that is conscious. Although coordinated brain
activity is certainly necessary for a self to “be,” it is by no means
sufficient. LeDoux is certainly aware of this fact, but does not seem to fully
apprehend its depth and significance. At one point, for example, he suggests,
“a working memory point of view is an excellent way of attacking the
[mind-body] problem” (195). The notion of working memory, however, presupposes
the possibility of ideas, percepts, and other experiences with which to work;
hence, it begs the question of the possibility of these experiential entities.
LeDoux is on much more certain ground when he makes assertions such as: “An
informed conception about the brain regions and circuits underlying a
particular function is the best way to begin to determine how the brain
actually performs that function.” (258) The other main problem with LeDoux’s
analysis is that he does not sufficiently demonstrate how his seven principles
interact over time in any given instance to allow a self to emerge.  Nevertheless, Synaptic Self is an
informative read for individuals interested in the neural structures and
systems that support consciousness.

© 2002 Michael Kurak