172 Self and the Phenomenon of Life
b2726 Self and the Phenomenon of Life: A Biologist Examines Life from Molecules to Humanity “9x6”mechanism, called “selective attention,” enables the brain to focus on a
particular item out of thousands of objects in the visual scene.^18
Dehaene and Changeux proposed that perception arises as a
construct of incoming sensory data based on internal models derived
from previous experiences. In the process the brain matches the new
with the old and assembles the former into the latter. It is a way of making
sense of the present by comparing with the past. This theory, called the
“global neuronal workspace model,” posits that conscious awareness
results from a dialogue between the sensory, motor, attention, memory,
and value areas to form a higher-level, unified space where information
is shared and broadcasted back to lower-level processors. The dialogue is
made possible by pyramidal cortical neurons, which send long-distance
cortico-cortical connections among the primary sensory areas and the
association areas of the brain.^19
Edelman stated that the brain is too complex to work logically
by a computer-like algorithm. He suggested that it works by select-
ing (through parallel and reentrance dynamics) the relevant out of
randomly formed possible representations. He pointed out that the
thalamo- cortical fibers that project in a reciprocal manner fit this recur-
sive modality, and therefore are important for conscious experience.^20
Crick, on the other hand, proposed that the synchronized firing (at about
40 hertz) between the thalamus and the cortex could be correlated with
visual consciousness.^21
As to the awareness of the bodily self, much can be learned from
the phenomenon of phantom limb. The phantom limb experience is the
perception of a body part when it is no longer there. The phenome-
non occurs in at least 90% of amputees, often accompanied by pain,
which may persist for years. Using neuro-magnetic imaging techniques,
there is a correlation between the severity of phantom-limb pain and the
degree of reorganization in the somatosensory cortex. The phenomenon
provides additional credence to the theory that the perception of body
image, like perception of the external world, is also a product of systems
construction in the brain.^22