Unit 3: The Brain
The Tools of Discovery:
Having Our Head Examined
Techniques to study the Brain
A brain lesion
experimentally destroys
brain tissue to study
animal behaviors after
such destruction.
Electrical stimulation of the brain involves sending a
weak electric current into a brain structure to
stimulate it. (It is not painful because the brain has no
pain receptors.)
Electroencephalogram (EEG)
 an amplified
recording of the
waves of electrical
activity that sweep
across the brain’s
surface
 these waves are
measured by
electrodes placed
on the scalp
CAT Scan
 CAT (computed tomography) Scan
 a series of x-ray photographs taken from different
angles and combined by computer into a composite
representation of a slice through the body; also called
CT scan
PET Scan
 PET (positron emission tomography) Scan
 a visual display of brain activity that detects
where a radioactive form of glucose goes while
the brain performs a given task
MRI
MRI (magnetic resonance imaging) is a technique
that uses magnetic fields and radio waves to produce
computer-generated images that distinguish among
different types of soft tissue. It allows us to see
structures within the brain. fMRI let’s us see blood
flow in the brain while it is working.
Older Brain Structures
The Brainstem
The brainstem is the oldest part
and central core of the brain,
beginning where the spinal cord
swells as it enters the skull. It is
responsible for automatic survival
functions.
The brainstem consists of:
• The medulla
• Pons
• Reticular formation
Medulla, Pons, Reticular Formation
The medulla controls breathing, heart rate, digestions, and
other vital reflexes like swallowing, coughing, vomiting and
sneezing.
The pons helps coordinate movements on the left and right
sides of the body which helps you maintain balance.
The reticular formation is a network of neurons in the
brainstem and thalamus that helps control attention, sleep
and arousal.
The Thalamus
• The thalamus is the
sensory relay system of
the brain. It processes
most information going
to our higher brain
centers (except smell). It
also send messages from
the higher brain to the
medulla and cerebellum.
The Cerebellum
Cerebellum means “little brain”
 Coordinated, rapid
voluntary movements
 e.g., playing the piano,
kicking, throwing, etc.
 Lesions to cerebellum
 jerky, exaggerated
movements
 difficulty walking
 loss of balance
 shaking hands
o One thing to note—These older brain
functions all occur without any
conscious effort, which illustrates a
recurring theme: Our brain processes
most information outside of our
awareness.
o Whether we are asleep or awake, our
brainstem manages its life-sustaining
functions, freeing our newer brain
regions to dream, think, talk, or
savor a memory.
The Limbic System
The limbic system is at the
outside edge of the older brain.
• The amygdala influences
aggression, rage and fear
and the processing of
emotional memories.
• The hypothalamus controls
maintenance functions
(eating, drinking, body
temp). The “reward center”
is here.
(4 f's mnemonic)
• The hippocampus is linked
to memory.
Amygdala
• In one experiment, part of a rhesus monkey’s
brain, including the amygdala, was surgically
lesioned, leaving the normally ill-tempered
monkey extremely mellow.
• However, electrically stimulating the amygdala
in a normally placid domestic animal, such as a
cat, resulted in an animal that is prepared to
attack.
15
 Upon discovering their
mistake, Olds and Milner
recognized that they had stumbled upon a brain
center that provides a pleasurable reward.
 More animal research has revealed both a general
reward system that triggers the release of the
neurotransmitter dopamine and specific centers
associated with the pleasures of eating, drinking,
and sex.
 We no longer refer to these areas as pleasure
centers, but as reward centers.
Sanjiv Talwar, SUNY Downstate
Hypothalamus
Older Forebrain Structures
The Cerebral Cortex
Introduction
Cerebral cortex
 the intricate fabric of
interconnected neural cells
that covers the cerebral
hemispheres
 Imagine, like bark on a tree
 the body’s ultimate control
and information processing
center
The Cerebral Cortex
Structure of the Cortex
Glial cells (“glue cells”)
• cells in the nervous
system that support,
nourish, and protect
neurons
• A recent postmortem
analysis of Einstein’s
brain did not find more
or larger neurons, but it
did reveal a much
greater concentration of
glia than found in an
average person.
oEach brain hemisphere is divided
into four lobes, geographic
subdivisions separated by
prominent fissures, or folds:
a) Starting at the front of your brain and going
around over the top, there are the frontal lobes
(behind your forehead).
b) The parietal lobes are at the top and to the
rear.
c) The occipital lobes are at the back of your
head.
d) The temporal lobes are on the sides of your
head, just above your ears.
o Each lobe carries out many functions, and
many functions require the interplay of
several lobes.
The Cerebral Cortex
 Frontal Lobes
 involved in speaking and muscle
movements and in making plans and
judgments. Many of the functions we
think of as human happen in the prefrontal cortex.
 Parietal Lobes
 include the sensory cortex &
processes somatic information
 Occipital Lobes
 include the visual areas, which
receive visual information from the
opposite visual field
 Temporal Lobes
 include the auditory areas
Auditory and Visual Function
The functional MRI scan
shows that the visual
cortex is active.
Here, the auditory
cortex is active.
Association Areas
Association areas are areas of the cerebral cortex that are not
involved in primary motor or sensory functions. They are
involved in higher mental functions such as learning,
remembering, thinking and speaking.
More intelligent animals have more “uncommitted”
association areas.
The Cerebral Cortex
 Motor Cortex
 area at the rear of the frontal lobes that controls
voluntary movements
 Sensory Cortex
 area at the front of the parietal lobes that
registers and processes body sensations
Functions of the Cortex
Motor cortex
Sensory cortex
Brain Song video
Right-Left Differences
Our Divided Brain
 Our brain is divided into two hemispheres.
 The left hemisphere processes reading,
writing, speaking, mathematics, and
comprehension skills.
 In the 1960s, it was termed as the dominant
brain, but this is no longer considered correct.
General
function only
– not location
of function!
Roger Sperry
studied the
differences
between the
hemispheres.
He also
pioneered split
brain research.
Language
Aphasia is an impairment of language, usually caused by
left hemisphere damage either to
• Wernicke’s area (impaired meaning)
• Angular Gyrus (reading).
• Broca's area (impaired speaking)
Language
Say it
output
visual to auditorysee it  hear it
See it
meaning
Phineas Gage
In 2009 and 2010, these two pictures were
found. Their owners had thought they were
pictures of a whaler with a harpoon. The
inscription on the tamping iron matches the
actual tamping iron.
Plasticity/Hemispherectomy/Injury
The brain is sculpted by our genes but also by our
experiences. Plasticity refers to the brain’s ability to
modify itself often after some type of injury or illness.
Hemispherectomy is the surgical
removal of an entire cerebral
hemisphere. It is VERY unusual,
and generally performed on
children with severe damage in
one hemisphere.
Concussions cause brain damage.
Dividing our Brain
Splitting the Brain
A procedure in which the two hemispheres of the
brain are isolated by cutting the connecting fibers
(mainly those of the corpus callosum) between them.
Corpus Callosum