Transcript Section 6 – The Brain

Section 6 – The Brain
Chapter 16: The neural correlates of consciousness
Chapter 17: The unity of consciousness
Chapter 18: Damaged brains
All right, brain, you don't like me, and I
don't like you, but let's just get me through
this, and I can get back to killing you with
beer!
Presenters: David & Mimi & Monica
Why Did the Chicken Cross the Road?
Cogito
Ergo Sum

Nietzsche: Because if you gaze too long across
the road, the road gazes also across you.

Jean-Paul Sartre: In order to act in good faith
and be true to itself, the chicken found it
necessary to cross the road

Albert Einstein: Whether the chicken crossed
the road or the road crossed the chicken
depends upon your frame of reference.

Darwin: It was the logical next step after
coming down from the trees.

Buddha: If you ask this question, you deny your
own chicken- nature.
Descartes

Donald Hoffman: If we assume that the
chicken is a conscious agent, then the road
is an icon in the multimodal user interface.
Chapter 16: The neural correlates of consciousness
How can this gray, wrinkly physical lump of stuff in be the seat of
consciousness?

One way to tackle this mind-baffling question is to
look for neural correlates of consciousness (NCC).

Correlations between neural events and conscious
experiences DOES NOT imply causality.

When a correlation between two events, A and B, is
observed, there are 3 ways to interpret this
phenomenon.
1. A might have caused B
Neural events cause conscious experience
2. B might have caused A
Conscious experience cause neural events
3. Third variable C gives rise to both A & B
X factor cause conscious experience & neural events.
Let’s consider the “unconscious state”.
Prior to surgery, a patient undergoes anesthesia, going
from a conscious state to an unconscious state.
What is biological mechanism behind this effect?
Hans Flohr (German neuroscientist) observes that the
normal functioning NMDA synapse is necessary for
consciousness.
Anesthetics abolish consciousness by interfering with the
functioning of NMDA receptors.
Conclusion: The NCC is the functioning NMDA synapses
and the cell assemblies they support.
But is it really that straightforward?
What is the “neural correlate” of conscious visual experiences vs.
unconscious vision ?
“So far we can locate no single region in which the
neural activity corresponds exactly to the vivid picture of
the world we see in front of our eyes”. Francis Crick
Are aspects of the visual system competing for
consciousness?
Binocular rivalry: different images are
presented to the two eyes.
First experiment were conducted on
macaque monkeys.
Procedure: Monkeys are shown different
display to each eye, horizontal grating to
one, vertical grating to the other.
Result: Some cells in early visual cortex (V1) WHAT DOES THIS MEAN?
responds to vertical stripes, some responds
THE NCC lies in IT?
to horizontal stripes. Their behavior did not
change when the monkey's perception
Can we really assume that
monkey's consciousness =
changed. But the behavior of these cells did
human consciousness?
change in the inferior temporal cortex (IT),
to match what the monkey reported seeing.
Phantom Limb Phenomenon
After
“The Little Man”
What we would look
like if our body parts
are proportional to
our sensory input.
losing an arm or leg, 90% of
patients experience a “phantom
limb”.
Patients feel pain in their
“phantom limbs” from time to
time.
Some report a touch on the face
can sometimes felt as a touch on
the phantom hand.
What gives rise to this
experience?
The somatosensory cortex map of
the body shows the sensory input
of the face as being represented
next to the hand.
If the hand is missing, the
sensory input of the face will start
to invade the hand area.
Chapter 17: The unity
of consciousness




Why do we seem to have only one consciousness?
Eccles dualism: The mind plays an active role in
selecting, reading out and integrating neural activity,
molding it into a unified whole according to its desire
or interest.
A far more constructive approach is to try to find out
how the brain carries out the integrating and unifying
functions.
Or, reject the idea that consciousness really is unified
at all. Perhaps, on closer inspection, we might find
that the apparent unity is illusory. In this case, the
task is to explain how we can possibly be so deluded.
The Binding
Problem
 As the coin flips, what keeps the color,form, movements
and other attributes of the coin together?
 In V1, there are many retinotopic maps. That is, the
organization of cells reflects the layout of the retina.
 GWT relates consciousness to working memory.
 There is evidence that attention is required for binding.
 However, binding at attention are probably not the same
thing because some things requiring binding are carried
out unconsciously: catching the coin by way of the
visuomotor system.
Binding by synchrony



The thalamus controls attention by selecting the
features to be bound together by
synchronization of firing. (Crick)
Andreas Engel, Wolf Singer, and colleagues say,
Neurons forming part of one represented object
fire together, and they fire out of synchrony with
neurons representing other objects at the same
time.
Synchronization is necessary but not sufficient
for consciousness. For consciousness,
information must also enter short-term memory.
Unity as illusion


Singleness of action is a vital requirement; if motor
responses were not unified, an animal could quite
literally tear itself apart!
Some people reject the idea that consciousness is
unified at all. Like Dennet's multiple drafts, by
paying attention to some thing the appearance of a
unified self having a unified experience is created. As
soon as attention lapses, the unity falls apart and
things carry on as normal.
Doh! what about multiple
consciousnesses?
The unification that comes
with self-consciousness is
an exception that is only
possible through language.
Semir Zeki
(neuroscientist)
Reentry and the Dynamic Core
Think of how many people you have seen in
your lifetime.
Think of how many paintings you’ve seen.
This is a vast amount of information, and you
can easily discriminate between all these states.
Consciousness is highly informative is it not?
There are two types of consciousness (Edelman
& Tononi).
Primary consciousness: many animals have
which allows for the construction of a scene, the
maintenance of short-term memory and hence a
“remembered present”.
Higher order consciousness: emerged later in
evolution, depends on reentrant connections
between language and conceptual systems.
CONSCIOUSNESS
OF
CONSCIOUSNESS
Synesthesia : Superunity
Synesthesia confounds the notion that conscious
experiences are unified.
To a person who possesses this ability, their senses of touch,
sight, sound are enmeshed.
Written letters or numbers are seen as colored, but people
can hear shapes, see touches or even have colored orgasms
(woah!).
Chapter 18 – Damaged Brains
What is like to blind but
believe that you can see?
What is like to be
paralyzed but convinced
that you can move?
What is like not to notice
that you don’t don’t
notice half of the world?
What do you
mean I have
hemifield
neglect?
Amnesia




Korsakoff: most common form of
amnesia, caused by the toxic
effects of alcohol.
Retrograde: a loss of long-term
memory that stretches back into
the past.
Classical conditioning remains
unimpaired and procedure
learning remains intact.
Are amnesiacs conscious?
Neglect



Anosagnosia: patients
are paralyzed but
convince themselves
that they can move.
Anton’s syndrome:
patients are blind but
convince themselves
that they can see.
Hemifield neglect:
occurs in right brain
damage, so patients
neglect their left visual
field.
Blindsight


Blindsight is a condition in
which a person claims that
he or she cannot see a
certain area of their visual
field, but when asked to
make a guess, that person is
right 90-95% of the time
A person with blindsight
could detect a slow or fastmoving stimuli, but was only
aware of the fast ones.
Wisdom tells me I am nothing.
Love tells me I am everything.
And between the two, my life flows.
Nisargadatta Maharaj