Transcript PSYCH-UNIT-2-1-BIO-THE-NEURONx

Psychology
Unit 2 - Biological Bases of Behavior,
Bio & The Neuron
“The astonishing hypothesis - You,
your joys and your sorrows, your sense
of identity, and your free will, are no
more than the vast assembly of nerve
cells and their molecules.”
- Francis Crick, Nobel Prize winning Biologist
This is an odd and unnatural view... at first.
Most people don’t believe it.
Maybe you don’t believe it
Most believe in dualism.
As Rene Descarte did.
“Are humans merely physical machines?”
He answered no. Animals are machines, he
said. But people have a duality.
What we are is not physical, we are immaterial
souls that have a physical body.
17th century perpetual motion machines of the French gardens.
Descarte knew what an automated machine (or robot) would be like.
Certainly humans were much better than that.
Dualism
Descartes Argument #1:
The creativity & spontaneity of human action
The use of language for instance.
“How are you?”
“I’m OK.” (standard response)
But, one could go into detail, you have the
choice, you are not a machine:
“I’m pretty darn awesome,
if I do say so
myself!”
Dualism
Descartes Argument #2:
“I think, Therefore I am.”
Of what could Descartes be sure of?
★ What if everything I am experiencing is just a
dream?
★ Or if it is a trick of some demon?
★ Do I even have a body?
★ Or is that too just an illusion?
★ How do I know I’m not crazy?
1 thing he can not doubt...
he is, himself...
thinking.
This was the launching point for
philosophy.
Dualism
Descartes Argument #2:
“I think, Therefore I am.”
There is something really different about having a
mind.
The soul by which I am, what I am, is entirely distinct
from my body.
Isn’t it just common sense?
“My arm” - “My heart”
“My child” - “My car” - “My leg”
We talk about owning our
body as if we are separate
from them.
Dualism seems right
Argument #2: Personal identity
Same person after radical bodily
changes
Personal identity: Many people, 1
body
Synopsis: Fantasy. But believable in
fictional movie form. We go along for
the ride and believe it, because the
dualist perspective seems right.
You can imagine it...
because we believe it for
ourselves.
Dualism just seems
right
Argument #2. Personal identity
Many people, 1 body
Synopsis: Movie “All of Me”...
fantastical farce about an eccentric
millionaires whose soul inhabits
her male lawyer’s body.
Cultural Traditions Back Dualism
Argument #3: The survival of the self
after the destruction of the body
“What will happen when you die?”
Fate of the soul?
(cultures vary, but share the idea of what you are is
separable from this physical thing you carry around.
The body can be destroyed, the soul lives on.)
Christians: 96% --> heaven
Jewish: Most said heaven
Atheists: “I’m gonna go to heaven.”
Current scientific view: Dualism is wrong!
Mind = Brain “The mind is what the brain does.”
Just like computation is the
product of a computer.
Problems with dualism science.
1. We now have a better
understanding of what physical
things can do (computers & robots)
2. Strong evidence for the role
of the brain
Mind = Brain “The mind is what the brain does.”
A computer can beat you at chess, but...
can a computer read your mind?
If so, is that proof that your mind is what
the brain does?
YouTube: 60 Minutes - Reading Your Mind
Neurons
About 1,000,000,000,000 [1,000 Billion]
★ Sensory neurons,
★ Motor neurons,
★ Interneurons (connect Sensory & Motor)
Neurons can regenerate!
All-or-nothing
Intensity: expressed through number of
neurons firing & frequency of firing
Neurons
All-or-nothing
Intensity: expressed through
number of neurons firing &
frequency of firing
Although neurons are all or
nothing, there are ways to
“code intensity.” Could be the
sheer # of neurons or the
frequency of firing.
Neurons
Synapse - tiniest little gap. Where the neuron
communicates chemically. 1/10,000 of a
millimeter wide. When a neuron fires the axon
sends chemical shooting through the gap.
Communication over synapses; axons
release neurotransmitters
★ excitatory
★ inhibitory
Drugs: agonists vs. antagonists
agonist - increases effect of neurotransmitters.
antagonists - slow down the amount of neurotransmitters
(destroy connections, or block them)
★ curare antagonist - blocks motor neurons paralyzes you.
★ alcohol inhibitory - it relaxes/shuts down the
portion of the brain that tells you not to do things.
Result - you are ‘less inhibited.’
★ amphetamines speed/coke - increase the
amount of arousal & Norepinephrineneurotransmitter responsible for awareness &
arousal
★ Prozac works on serotonin, depression =
neurotransmitter issue, not getting enough
serotonin
★ L-DOPA - Parkinson’s Disease is a lack of
dopamine & L-Dopa... in part
Is the brain wired up like a personal computer?
NO -- because it is:
★ highly resistant to damage
★ extremely fast
★ unlike most human-designed
computers, the brain works through
massively parallel processing
What do different parts of the brain do?
You don’t need your
brain for everything...
★ sucking in newborns
★ limb flexion in withdrawal
from pain
★ vomiting
What does the brain do? Some subcortical
structures
Medulla: certain reflexes,
heartbeat, breathing
Cerebellum: complicated
skilled motor movements
(contains 30 billion neurons!)
Hypothalamus: hunger,
thirst, to some extent sleep
Cerebral Cortex: Where
the action is! The outer
layer. The crumpled up part.
The wrinkles. 2 feet sq. if
you took it out and flattened
it. 80% of our brain is
cortex.
Cerebral Cortex Mapping or Projection
Areas
1. topographical
2. size in the brain of the
body part is the extent to
which they have motor or
sensory control.
ex. shoulder is tiny. The
mouth is HUGE.
Some subcortical
structures
Less than 1/4 of the human
cortex contains projection
areas...
the rest is involved with
language, reasoning, moral
thought, etc.
Some very bad things that could happen to you and
your brain
Apraxia - can not coordinate their
movements.
Agnosia - disorder that isn’t blindness, their
eyes are intact. They lose the ability to
recognize things.
★ visual agnosia - failure to
recognize objects
★ prosopagnosia - failure to
recognize faces
Sensory neglect - disorder where one
could no longer be able to use a side of their
body, or even know about anything on that
side of you - in a sensory way.
Aphasia - Broca - “Tan.” “Tan, tan, tan,
tan!”
Acquired psychopathy - Damage to parts
of your brain (frontal lobe) rob you from the
ability to tell right from wrong.
How many minds do you have?
YouTube: Right Brain vs. Left Brain - The man with 2 brains
Brain has 2
Hemispheres
Left & Right sides are separate
Corpus Callosum: major
pathway between hemispheres
Some functions are ‘lateralized’
★ language on left
★ math, music on right
Lateralization is never 100%
Sensory Information sent to opposite
hemisphere
Contralateral Organization
Sensory data crosses over in pathways leading to the
cortex
Visual Crossover
left visual field to right hemisphere
right field to left
*Other senses similar
Contralateral Motor Control
Movements controlled by motor area
★ Right hemisphere controls left side
of body
★ Left hemisphere controls right side
★ Motor nerves cross sides in spinal
cord
Corpus Callosum
Major (but not the only) pathway
between sides
★ Connects comparable
structures on each side
★ Permits data received on
one side to be processed
in both hemispheres
★ Aids motor coordination
Corpus Callosum of left
and right side
The Story of HM
Henry Gustav Molaison (who became
famous as ‘HM‘ in neuroscience textbooks)
was born on February 26, 1926. After a
bicycle accident at the age of 7 he
suffered from debilitating epilepsy and in
1953 he underwent neurosurgery in an
attempt to contain seizures.
Before surgery,
1953
Doctors localised HM’s epilepsy in his medial-temporal
lobes and removed a large part of the hippocampus in
both hemispheres. At the time they had no idea of how
crucial these areas are for the normal functioning of the
human brain…
Soon after the operation it became clear that something
was wrong. HM suffered from severe anterograde
amnesia: he was otherwise normal but no longer able
to commit events to memory.
He would not remember the newspaper he
had just read or the people he met a few
minutes ago, he was stuck in the present.
Brain- temporal lobe cut away,
showing the hippocampus. The
hippocampus is the part of the
brain responsible for long-term,
declarative memories and for
spatial memories.
HM was studied
revolutionising the
understanding of
human memory.
Provided broad
evidence for the
rejection of old theories
&
the formation of new
theories on human
memory & the
underlying neural
structures.
When HM died in 2008,
neuroscientists were provided with
the most extensively studied brain in
history.
This anatomical treasure was entrusted
to Dr. Jacopo Annese in the University of
California, San Diego, who acquired
2041 slices of HM’s brain and made
them available to study.
Dr. Annese is the founder of the Brain
Observatory, an ambitious project which
aims to collect as much information as
possible on brain donors, in the hope
that one day we will be able to track the
connection between the brain structure
and our life history.
THE HM PROJECT:
YouTube: Clive Wearing - The Man With No Short Term Memory
A Bit of Humility
Mind as information processor, as
computer
Recognition, language, motor control,
logic, etc.
But there still remains:
“The Hard Problem of
Consciousness”
Subjective experience, “what it’s like”
qualia - is a term used in philosophy to refer to individual
instances of subjective, conscious experience. The term
derives from a Latin word meaning for "what sort" or "what kind."
Ex: the pain of a headache, the perceived redness of an evening
sky.
A bit of humility, Part I
“How it is that anything so remarkable as a
state of consciousness comes about as a
result of irritating nervous tissue, is just as
unaccountable as the appearance of the
Djin, when Aladdin rubbed his lamp.”
-- Thomas Huxley
Bit of Humility
Mechanistic conception of mental
life
But what about humanist values?
★ free will & responsibility
★ intrinsic value
★ spiritual value?
Can they be reconciled?