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COGS 17 – Neurobiology of Cognition
Handout #2, Wednesday, October 8th, 2008
Constant theme of the course:
BRAIN  MIND
STRUCTURE  FUNCTION
There is a physical basis for the mind, & we are studying it.
It’s really easy to get caught up in the little details of the neurobiology, but what will help you is if you
constantly try to understand WHAT this means for cognition. We’re studying the structure… so what
is the function? We’re studying the brain… so how does it define the mind?
Chapter 1 reading (Week 1, Tuesday)
Consciousness: an awareness of self, & requires the ability to communicate with self and others about self.
Three pieces of experimental evidence for consciousness:
Phenomenon
What is it?
What does this tell us
about consciousness?
Blindsight
This occurs when one is unaware of
Consciousness
a certain perception of a sensation,
(awareness of an object
and the corresponding sensory
in the visual field)
information is able to guide that
requires a special area
person’s behavior.
of the brain, the
“mammalian visual
system”; it is not a
general property for all
parts of the brain.
Unilateral
Damage to the R parietal cortex,
Consciousness
neglect
which is normally used for awareness (awareness of body and
of body and space, causes a failure
space) requires the R
to both notice and remember what is
parietal cortex.
in the L visual field.
Split brain
In attempts to treat epilepsy
(spreading & excessive neuronal
activity), the corpus callosum is cut.
Now, each hemisphere can still work,
but has no idea what is going on with
the other.
* Patient will say, “I see (R)”, but
cannot see (L).
* Patient will point with L hand to (L).
Consciousness
(awareness of object in
left or right visual field)
requires visual
information to reach the
verbal areas in the left
side.
How?
What is sensed by the
eye is fed into two
separate visual
systems.
Primitive: no
awareness, simple
behavior. Mammalian:
awareness, speech.
The R parietal cortex
receives visual input
from the R occipital
cortex, which receives
sensory input from the
L field of both eyes.
Memories are also
lateralized.
Each hemisphere:
- receives visual input
from the opposite side
- controls movement
for the opposite side
Left hemisphere:
- understands verbal
instruction
- produces words
COGS 17 – Neurobiology of Cognition
Handout #2, Wednesday, October 8th, 2008
Chapter 2 reading (Week 1, Thursday)
Information is gathered from the environment by sensory neurons. Movements are carried about by muscle
contractions which are controlled by motor neurons. There are also interneurons that communicate between
the sensory neurons and motor neurons, located entirely within the central nervous system. There are two
types of interneuron: local, which form circuits with nearby neurons and are responsible for small pieces of
information, and relay, which connect circuits of local interneurons in different brain regions.
The nervous system is the system in
body that receives input from the
environment, makes sense of it, and
controls behaviors as a response. It is
divided into the central nervous system
the peripheral nervous system. Of the
central nervous system, there is the
and the spinal cord. The basic
functional unit of the nervous system is
neuron. Here is a neuron:
the
and
brain
the
The neuron, or brain cell, has several
key
features. The soma contains the
nucleus, which essentially controls the
cell.
Extending from the soma are the dendrites, which receive input from surrounding neurons. The axon is the
long structure that transmits information along the cell in the form of an electrical signal known as the action
potential. Surrounding the axon is myelin, which is provided by the Schwann (for the PNS) or
oligodendrocytes (for the CNS). Myelination is needed in order to increase the speed of electrical conduction.
Myelination works because there are gaps in the myelin, called nodes of Ranvier, which allow the electrical
signal to jump from gap to gap, which is much faster than having the electrical signal travel down the entire
length of the axon. This type of electrical conduction is called “saltatory". Once the electrical signal reaches
the terminal button, it causes the release of neurotransmitter into the synapse, which is the connection
between two neurons. The released neurotransmitter binds to receptors on the dendritic spines of other
neurons, which recreate the electrical signal that is sent off down new neurons.
The internal structure of a neuron, as with all cells in the human body, is important to understand if we want to
know how the neuron carries out its functions. The important organelles of the neuron are contained within the
soma. The main bulk of the soma is the cytoplasm, which is a jelly-like liquid that fills the entire cell, and
contains the organelles. One of the organelles, the nucleus, is very important because it contains DNA in the
form of chromosomes, and in these chromosomes are genes which control what proteins are made by the
neuron. Proteins are needed by all cells and have several different cellular functions; these include providing
structure and serving as enzymes. Enzymes are proteins that catalyze biological reactions, and these
biological reactions are needed for the neuron to live. Another important organelle is the mitochondria, which
provides energy to the neuron.
Although neurons are the functional units of the nervous system and the brain, there are many other cell types
that are needed for neurons to work. In the brain, there are four types of neuroglial cells:
Astrocytes
Oligodendrocytes
Ependymal
Microglia
Remove excess NT and ions
Myelinate neurons
Line ventricles, release CSF
Fight pathogens
“Moppers”
“Warmers”
“Squirters”
“Security guards”
Astromop!
Oligodendrowarmer!
Epensquirt!
Microguard!
COGS 17 – Neurobiology of Cognition
Handout #2, Wednesday, October 8th, 2008
Chapter 3 reading (Week 2, Tuesday)
Because the nervous system and the brain are so complex, researchers have come up with different ways to
study the different parts of the body and the brain.
There are three different axes by which we study the body and the brain.
Anterior-posterior:
refers to near the head/near the tail.
Ventral-dorsal:
refers to toward belly/back, or toward the bottom/toward the top.
Lateral-medial:
refers to toward the side/toward the middle.
We can also describe different body parts or brain regions relative to one another by saying they are
ipsilateral (on the same side) or contralateral (on opposite sides).
Since the brain is such a complex structure with many substructures, researchers need to slice the brain in
different ways, in order to visualize the structures deep within the brain. There are three different planes by
which we can slice the brain.
Horizontal:
looking at it from the top/bottom
Frontal:
looking at it from the front/back
Saggital:
looking at it from either side
Support structures
Meninges: protective tissue around the brain and spinal cord
- Dura mater (“tough mother”)
thick layer
- Arachnoid mater (“spider mother”) spider-web-y and spongy layer
- Pia mater (“pious mother”)
glad wrap layer
 If meninges are inflamed, meningitis 
Ventricles: hollow inter-connected cavities in the brain that produce CSF
o Forebrain: lateral ventricles (first & second), third ventricle
o Midbrain: cerebral aqueduct
o Hindbrain: fourth ventricle
 If flow from ventricles is blocked, hydrocephalus (“water on brain”)  which can be drained 
CSF: cerebrospinal fluid, made by ependymal cells along the ventricles
- cushions and supports the fragile brain
- provides a reservoir of hormones and nutrients
- contained in subarachnoid space (between the two arachnoid membranes)
- half-life = ~3 hours, drains from subarachnoid space and is reabsorbed by veins
Blood vessels: arteries bring blood in, veins bring blood away
- main purpose is to bring oxygen and glucose for the brain to function
- the brain is less than 2% of body weight, but it requires 20% of continuous blood supply
- cut blood supply for 6 seconds  unconscious; 4-6 minutes  permanent brain damage
Blood-brain barrier: semi-permeable membrane that prevents most chemicals from entering brain
Brain development
There are two components to brain development: genetic and environmental. The genetic component comes
into play after the eighteenth day of conception. The neural plate fuses such that it becomes the neural tube,
which in turn produces the forebrain, midbrain and hindbrain. The tube also develops three chambers, which
become the ventricles. As development progresses, the individual ventricles form from the dividing chambers.
Sometime later, there is a switch, and then the brain becomes susceptible to environmental influence:
chemicals and outside signals can change the brain structure.
COGS 17 – Neurobiology of Cognition
Handout #2, Wednesday, October 8th, 2008
Brain organization
Forebrain
- Telencephalon
 Limbic system
 Basal ganglia
 Basal forebrain
- Diencephalon
 Thalamus
 Hypothalamus
Midbrain
- Mesencephalon
 Tectum
 Tegmentum
Hindbrain
- Metencephalon
 Cerebellum
 Pons
- Myelencephalon
 Medulla oblongata
Four lobes
Frontal
Parietal
Occpital
Temporal
emotions
control of movement
arousal
receives all sensory input
4 F’s: feeding, fighting, fleeing, sex
part of sensory pathways to brain
part of motor pathways from brain
coordination of fine movement, balance
sleep and arousal
vital reflexes: e.g. breathing, heart rate, vomiting, coughing
 executive functioning, defines personality
*Primary motor cortex (M1)
produces movement
*Primary somatosensory cortex (S1) receives & combines input from sensory organs
 understanding space and own relationship to it
End of “where” pathway
 visual processing
*Primary visual cortex (V1)
 auditory and visual processing
*Primary auditory cortex (A1)
End of “what pathway”