The Literary Mind.pdf

HUMAN MEANING 23
ries of connections between such image schemas have only recently been developed
and remain speculative. Antonio Damasio has proposed a neurobiological
model of "convergence zones" that might have something to say about such
cross-modal integration. His model "rejects a single anatomical site for the
integration of memory and motor processes and a single store for the meaning
of entities or events. Meaning is reached by time-locked multiregional retroactivation
of widespread fragment records. Only the latter records can become
contents of consciousness." Because a higher-order convergence zone is crossmodal,
it offers a site for activating different neuronal patterns corresponding
to the identical image schema across different modalities.
The most specific evidence of image schemas in the brain comes from
reports of what are known as "orientation tuning" columns. The primary visual
cortex responds to moving bars of light in an interesting way: A given neuron
will have a preferred "orientation tuning"—it will respond best to a bar at a given
angle. Other neurons in the column appear to have the same preferred stimulus,
so that the column constitutes a neuronal group of cells that fire together in time
in an organized manner to recognize a line at a preferred angle. Different orientation
columns prefer different angles. In this way, orientation tuning columns
work like neurobiological image schemas for structuring certain kinds of visual
experience and for understanding it. These orientation tuning columns in the
primary visual cortex are connected to neuronal groups in another, separate visual
map, known as V2, and these two connected visual maps respond coherently
to the same preferred stimulus, which suggests that image schemas in primary
visual cortex are coordinated with analogous image schemas in V2.
Gerald Edelman's theory of neuronal group selection offers a suggestion for
a general neuroscientific explanation of image schemas. In simplistic outline, it
has the following logic. A sensory sheet (like the retina) projects to various
regions of the nervous system (called "maps"). For any particular map, repeated
encounter with a stimulus results in changes in synaptic strengths between neurons
in the map, thus forming up ("selecting") certain neuronal group patterns
in that map that become active whenever the stimulus is encountered. For any
particular stimulus object, there will be many neuronal group patterns in many
maps. (For example, there are different maps for different modalities, like vision,
and for different submodalities, like form, motion, and color.) These various
neuronal group patterns in the various maps are linked through another hypothetical
neurobiological process Edelman calls "reentrant mapping": a given
stimulus will result in activity in many maps, and these activities are linked
reinforcingly through "reentry."
For example, an image schema for container would be a coordinated dynamic
interaction across neuronal group patterns in various maps that arose through