Transcript The Cerebral Cortex

The Cerebral Cortex
The Evolving Brain
• Different animal
species have many
structures in common,
including a cerebellum
and cortex.
• The cortex is much
larger in mammals
than in species that
evolved earlier, such as
fish and amphibians.
• The cross section of
the human brain shows
how the cerebral cortex
has developed around
and above more
primitive brain
structures.
When it comes to Cortex…
Size DOES Matter
• If flattened, a human
cortex would cover
about four pages of
this book.
• A chimpanzee's
would cover one
page
• a monkey's a
postcard
• a rat's a postage
stamp.
• From Scientific
American, October
1994, p. 102.
Areas of the Cortex
• More intelligent animals have increased
"uncommitted" or association areas of the
cortex.
• These vast areas of the brain are responsible
for integrating and acting on information
received and processed by sensory areas.
Forebrain Structures
Largest Brain Region
with the most complex
structures.
What separates us from
the beasts.
Cortical Specialization
• Localization—notion that different
functions are located in different areas
of the brain
• Lateralization—notion that different
functions are processed primarily on
one side of the brain or the other
Each hemisphere is
divided into 4 lobes
Frontal
Parietal
Occipital
Temporal
Lobes of the Cortex
• Frontal lobe—largest lobe, produces
voluntary muscle movements, involved in
thinking, planning, emotional control
• Temporal lobe—primary receiving area for
auditory information
• Occipital lobe—primary receiving area for
visual information
• Parietal lobe—processes somatic
information
Frontal Lobe
• Contains primary motor
cortex
• Important planning and
judgement
• Broca’s area for speech
• Controls emotions
Frontal
Lobe
Broca’s
Area
Motor
Motor
Cortex
Cortex
Temporal Lobe
Contains primary
auditory cortex

• Hearing Perception
– speech recognition
– face recognition
– word recognition
Auditory
Cortex
Temporal
Lobe
Occipital Lobe
• Input from Optic
nerve
• Contains primary
visual cortex
• The “eyes in the back of
your head”
Occipital
Lobe
Visual
Lobe
Parietal Lobe
• Receives inputs
from multiple senses
• Contains
somatosensory
cortex
• Deals with Skin
Senses
Somatosensory
Parietal
Cortex
Lobe
Motor
Cortex:
Located at
the back of
the Frontal
Lobe.
The more
precise
movements,
the more
motor
cortex the
part uses
up.
Sensory
Cortex:
Located at
the front of
the Parietal
Lobe.
The more
sensitive
the area, the
more
sensory
cortex it
uses up.
Language and the Brain
• Aphasia—partial or
complete inability to
articulate ideas or
understand language
because of brain injury or
damage
• Broca’s area—plays role in
speech production
• Wernike’s area—plays role
in understanding and
meaningful speech
Aphasias
• Broca’s Aphasia – Damage to Broca’s Area causes a
person to struggle formulating words while still being
able to comprehend speech.
• Wernicke’s Aphasia – Damage to Wernicke’s Area
would cause a person only to be able to speak in
meaningless words.
• Example of Wernicke’s Aphasia: Asked to describe a
picture of two boys stealing cookies from behind a
woman’s back, a patient responded,
• “Mother is away her working her work to get her better,
but when she’s looking the two boys looking the other
part. She’s working another time.”
Language Areas of the Brain
This research was done with a PET Scan
How We Read Out Loud
Brain Plasticity
2 Types of Plasticity
1. Structural Plasticity – Actual changing of
the neuron or actually growing new
neurons.
•
Neurogenesis only occurs in the hippocampus
2. Functional Plasticity – When an area of
the brain takes up a new function to
replace a damaged area of the brain.
Examples of Plasticity
• If a body part is amputated, the surrounding neurons in
the somatosensory cortex rewire themselves to other
areas in the body.
• Example: The hand is between the face and are regions
on the sensory cortex thus when stroking the face of
someone whose hand was amputated, the person felt the
sensation not only on their face but also on their
nonexistent “phantom” fingers.
• A 5-year old boy who had severe seizures in his left
hemisphere required the removal of the entire
hemisphere. What was the result? While he is paralyzed
on his right side he grew up to have above average
intelligence, completed college and grad school and is
now a business executive.
More Examples of Plasticity
• Newborn ferrets had the optic nerve of their
brains rewired to take visual information
into their auditory cortex. Result? It could
see light in its auditory cortex.
• The sense of touch invades the part of the
brain normally used for sight in blind
people.
Brain Plasticity
Can the brain rewire itself if you
lose your vision?
7:03 minute clip
Click below to view video
What happens when you’re born
without a portion of your brain?
See video from class on hydrocephalic
More on Phantom Limbs
• Mirror Therapy to help with Phantom limb pain. See
video HERE for explanation (5 min).
Can a person’s environment
affect their brain development?
YES!
Click on
video box to see
how
London Cab
Drivers
rewire their
brain
An enriched environment =
more neural connections in the
brain.
Methods to Study the Brain
The Brain
How do we learn about the brain & its functions?
Tools of discovery
1. Clinical observation (case study) -
Phineas Gage
– The Story of Phineas Gage (An
Reenactment) – Module 25 of The
Brain DVD (12:00)
The Brain
Tools of discovery
2. Manipulating the brain
a. Lesions – purposely destroying a part of
the brain and observing the results.
b. Brain Stimulation
The Brain
Tools of discovery
3. Electroencephalogram (EEG) – shows the
brain’s electrical activity.
The Brain
Tools of discovery
4. Three Major Imaging Techniques
• CT Scan
• PET Scan
• MRI
Brain Imaging: 3 Types
• Imaging of the human brain allows us to look inside the brain
without surgical intrusion.
CT Scan
• CT (computed tomography) scanning is a much-improved version of
x-ray imaging. A CT scan takes a series of cross-sectional
photographs, which are then put together to form a threedimensional image.
PET
PET (positron emission tomography) scans
reveal the activity of different areas of the brain
by showing consumption of radioactive glucose
(active neurons use more glucose) as the subject
performs various mental activities.
MRI
In MRI (magnetic resonance imaging), spinning atoms
within the brain are aligned in a strong magnetic field. A
brief pulse of radio waves disorients the aligned atoms,
and the signals released as the atoms realign are
processed to form images.
Two Types of MRI:
Structural MRI
Functional MRI
Shows structures within the
brain
Show functioning of different
structures in the brain
Click below to view an example
Click below to view an example