These are excerpts and elaborations from my book "The Nature of Consciousness"
|
Binding Brain and
Consciousness Knowledge about the world is
distributed around the brain. How it is then integrated into one unitary
perception is the "binding" problem.
This problem occurs at
several levels. A sensory input is channeled through several different areas of
the brain, each brain region focusing on one aspect of the input, but then
somehow the mind perceives the whole input as something that happens at the
same time in the same place, and it is a whole. The "binding" problem
refers to how the brain creates the whole perception out of a sensory input
that has been fragmented around the brain. For example, a visual input
is "split" so that one brain region analyzes the shape and one brain
region analyzes the color. But somehow these separate pieces of information are
joined again to produce the overall sensation of the image. At a higher level,
different sensory inputs come together: the sound of an event is merged with
the image of the event, or the smell of the event, or the touch of the event.
The result is the overall feeling of the situation. At an even higher level, the
situation is merged with pre-existing memories and concepts. We don't only see
a human being moving and speaking around us: we see our friend X talking to us.
At the highest level, this entire complex system of feelings and knowledge
"feels" unified in our consciousness. There is "one"
feeling of "me" existing in a "world". Somehow all has been
"bound" together into consciousness. There are different theories
about where and how and when this ultimate form of "binding" could
occur. Space-based binding is
advocated by scientists who believe that there is a specific place in the brain
where all information is integrated together. In the 1990s, a competing
paradigm has emerged which is based on time instead of space, and is therefore
referred to as "time-based binding": there is no particular place
where the integration occurs, because integration occurs over the entire brain,
and is regulated by some periodic process. Space-based binding theories
try to identify the "homunculus" in the brain that is responsible for
running the integration process. The working memory is a
popular candidate for such a task, but no piece of the brain seems likely to
show us the transformation of electrochemical processes into feelings
(conscious processes). According to the Portuguese
neurobiologist Antonio Damasio, the story is more complex. There is not just one working memory:
there is a whole system of "convergence zones". The brain has
"convergence zones" and convergence zones are organized in a
hierarchy: lower convergence zones pass information to higher convergence zones. Lower zones select relevant details from
sensory information and send summaries to higher zones, which successively
refine and integrate the information.
In order to be conscious of something, a higher convergence zone must
retrieve from the lower convergence zones all the sensory fragments that are
related to that something. Consciousness of something occurs when the higher
convergence zones fire signals back to lower convergence zones. Back to the beginning of the chapter "Consciousness: the Factory of Illusions" | Back to the index of all chapters |
|
|
|
|