Week 1: Introduction + Neurons and glial cells
Learning goals
Introduction (Histories of cognitive and biological psychology + classic methods)
History of cognitive psychology
Introspection
Wundt and Titchener introduced the method of introspection. Psychologists believed that the
mind could be studied best by training subjects to look inside of their minds (to intro-spect)
and to report back what exactly they had observed.
Another psychologist of the time, Watson, poked some holes into the method of
introspection. He identified two limitations of introspection: the reports are not falsifiable (1),
and the reports would be too variable (2) (meaning that you do not know by what the
differences in the reports are caused).
Behaviourism
Watson rejected the idea of studying the mind entirely; it is non-observable and
non-objective to study the mind, and therefore it does not meet the criteria of the scientific
method. He believed that a focus on behaviour was more appropriate. Thus, there was no
longer a focus on consciousness, but now on experience, and learning; behaviourism.
Just like Watson poked holes into introspection, Chomsky did just that with
behaviourism. He identified an important limit of behaviourism; it is unable to explain creative
processes such as language. (e.g. Skinner explained from a behaviourist POV that language
is learned through the way people respond to verbal behaviour, but that does still not explain
how, for example, completely new sentences can be formed and understood by others -
language also does not need to be reinforced).
The eventual downfall of behaviourism was caused by the limitations of
reinforcement (1), and upcoming cognitive models based on the computer metaphor (2).
Toward cognitive psychology
Cognitive models based on computer metaphor
The introduction of the electronic digital computer encouraged scientists to think of the
human mind organised in a similar way to the computer. They compared the ways of how
the human mind and how the computer generate output. This led to cognitive models based
on the computer metaphor.
Broadbent came up with a model featuring a selective filter (Broadbent’s filter of
attention) that would decide which information moved on for further processing, and which
does not (memory). Sternberg focused on the step after that, the temporary storage of
information. Information would get stored so it can later be used to perform a certain task,
this cognitive model assumed a STM and a LTM.
Thus, a grave difference between cognitive models and behaviourism is that
cognitive models focus on mental processes, and behaviourism on stimuli
and responses.
Sternberg conducted an experiment in which the subject had to
indicate, by using a ‘yes’ or ‘no’ lever, wether a certain number had
appeared in a previously shown row of numbers. Sternberg assumed that
,the numbers got stored into the STM (cognitive process). The results showed that mean
reaction time increases linearly as a function of the size of the memory set. This was the
case for both ‘yes’ and ‘no’ answers, indicating that all items in STM are serially scanned
before a decision is made. Scanning speed was about 40 ms (scanning the items in the
STM). This was determined based on the fact that reaction speed increased with 40 ms for
each extra number added to the list.
Sternberg’s experiment shows the fundamental principles of the field of cognitive
psychology: mental processes exist and can be examined through experimental
manipulation.
History of biological psychology:
Biological psychology is the study of the biological basis of human behaviour. It studies the
relationship between biological and physiological processes. An important milestone in the
history of biological psychology is Darwin’s theory of evolution. Because of this, one now
understand that mental processes and brain regions evolved to have specific
functions.There are two techniques that can be helpful in understanding the nervous system:
the electrical stimulation technique (1) and experimental ablation (2).
Electrical stimulation technique
The electrical stimulation technique is based on the fact that electrical signals are
transmitted through the nervous system, manipulate those and you can manipulate the
nervous system. Eventually you can create a map of brain regions and their functions (as
Penfield did). Electrical stimulation requires the removal of a part of the skull so the cerebral
cortex can be reached. In humans, this is only possible during brain surgery (with
permission). Scientists then rely on introspection of a patient when the result of the electrical
stimulation is not observable. This is a limitation of the electrical stimulation technique: most
of it has to be performed on animals, but they cannot introspect (so they cannot report
non-observable (to the scientists) experiences).
Experimental ablation
Experimental ablation is more intrusive and therefore only conducted in animals. It requires
the purposefully damaging of a specific brain area to examine its function. It allows scientists
to see what function of the brain is involved in what tasks.
Experimental ablation on humans is considered unethical, therefore to study brain
areas in humans, patients with naturally occurred brain damage, or surgically removed brain
areas, are used. A limitation of that is that the actual brain damage can only be established
with an autopsy (1), that it is difficult to determine what area is responsible for what task
when multiple brain areas are damaged/removed (2), and that it is difficult to generalise from
small-N or single-N studies (3).
Donders’ subtraction method
Information processing is a topic where biological and cognitive psychology very much are
combined.
Donders’ subtraction method provides insight in how long mental processes can
take. Donders stated that the duration of a mental process can be measured by having
subjects perform two nearly identical tasks, the only difference would be that one task has
critical process and the other does not. For example, the simple RT (go-task)(respond to
,specific stimulus: requires discrimination/critical process) and the go/no-go task (respond to
all stimuli: does not require critical process). To determine the time necessary to discriminate
between stimuli (DT), Donders’ substraction method can be used: DT = simple RT -
go/no-go task
*The reaction time in go/no-go task is longer
The neuron and glial cells
● I know what types of neurons and glial cells exist, and understand their role in
the CNS
For starters, there are three types of neurons;
sensory neurons, interneurons, and
motorneurons. Sensory neurons sense what is
going on, and send that signal to the CNS via
interneurons. Interneurons connect sensory
and motor pathways, so the signal then is
connected to motor neurons, and muscles
contract.
Glial cells are cells, that besides neurons, make up the nervous system. They
do many things, such as offering support, and doing things for neurons because they
cannot do them themselves. Glial cells can be divided into microglia and macroglia.
Microglia are responsible for immunologic defence, and for the removal of dead cells
via a process called phagocytosis (breaking down and engulfing undesirable cells).
Microglia fight diseases in the nervous system, but in the case of dysregulated
immune system they can start attacking healthy neurons. An example of this is
multiple sclerosis (MS). MS is caused by microglia attacking the myelin on neurons,
disrupting electrical impulses along the nerve. As a result of the attack, plaques for in
the affected areas in the brain and spinal cord - leading to coordination, balance, and
cognitive impairments.
Macroglia consists of three types of glial cells: astrocytes,
oligodendrocytes, and Schwann cells. Astrocytes have multiple functions.
First, it provides structure and solidity to the CNS as it hangs in between
neurons, kind of like a big star (astron = star). They also isolate synaptic
clefts in order to make sure that when during chemical communication
between neurons, released neurotransmitters do not just go around
everywhere floating through the CNS and affecting other neurons. Lastly,
they are also tasked with the feeding of neurons with glucose. Due to the blood-brain
barrier, glucose cannot enter the brain by itself as the capillaries in many parts of the
brain do not have gaps to let molecules through. This is a nifty thing, as that way,
there is always control over what substances can (not) enter the brains fluids. The
astrocyte is able to extract glucose from the capillaries, and pass it on to the neurons
it has attached itself to.
Oligodendrocytes also have a crucial role within the CNS. They provide
neurons with their myelin sheaths by wrapping their arms around their axons multiple
times. One oligodendrocyte can create multiple myelin sheaths, and hangs in
between the axons of neurons like a spider.
Schwann cells are kind of like the little brother of oligodendrocytes. They also
are responsible for the creating of myelin sheats, but in the PNS. Another important
, difference between Schwann cells and oligodendrocytes, is that a single Schwann
cell can only form one myelin sheath by wrapping itself around the axon.
● I know what important structures of neurons are and what their functions are
The important structures as a neuron are as follows (from ‘head to toes’): The
dendrites are the branch-like structures on a neuron. They receive signals from other
neurons via synapses. A synapse between a presynaptic terminal button and
postsynaptic dendrite is called an axodendritic synapse.
Next is the soma (cell body). Inside of the soma excitatory and inhibitory
signals received from the dendrites are organised and weighed, potentially leading to
an action potential (in the case of more excitatory (EPSPs) than inhibitory signals
(IPSPs). Inside of the cell body are cell organelles (‘little
organs’): the nucleus (holds DNA and has pores for
mRNA transport for protein synthesis), the endoplasmic
reticulum (produces (rough ER contains the ribosomes),
stores, and transports proteins), the Golgi apparatus
(packs neurotransmitters into vesicles), lysosomes (for
removing the wase from the cytoplasm), and microtubuli
(the road systems than allow axoplasmic transport). A
synapse can also be formed on the soma, this is then
called an axosomatic synapse.
Then come the axon hillock and the axon itself. The axon hillock generates a
new action potential if the EPSPs and IPSPs combined reach the threshold of
excitation (-55mV) - it is like decision point. The axon itself allows the propagation of
an action potential. On an axon too can a synapse be formed, we call this an
axoaxonic synapse.
Now come the terminal buttons. Terminal buttons store vesicles filled with
neurotransmitters, that will be released into the synapse via a process called
exocytosis once an action potential takes place.
● I know how the membrane potential is supported
The term ‘membrane potential’ refers to a difference in the electrical charge of a
neuron. When a neuron is inactive (so, not busy firing), it is at the resting membrane
potential (ca. -65 to -70 mV) - the outside of the neuron is more positive than the
inside. Important ions involved in the support of the resting membrane potential are:
Na+ (sodium), Cl- (chloride), K+ (potassium), and A- (large negatively charged
proteins).
The largest concentration of Na+ and Cl- is outside of the cell, in the
extracellular fluid. Inside of the cell, there is a large concentration of K+ and A+. It is
important to note that the membrane of the neuron (made up of a double layer of
phospholipids) is not permeable for A-, so it cannot escape the cell. The other ions
can travel inside and outside of the neurons by means of the forces of diffusion and
electrostatic pressure. Diffusion refers to the process in which ions want to move
from areas of high concentration to areas of low concentration. Electrostatic pressure
refers to the process in which similarly charged ions repulse each other, but
differently charged ions attract each other (opposites attract).
Due to the forces of diffusion and electrostatic pressure, Na+ ions leak into
the neuron, and K+ ions leak out, they leak via leak channels. If this were to continue,
Learning goals
Introduction (Histories of cognitive and biological psychology + classic methods)
History of cognitive psychology
Introspection
Wundt and Titchener introduced the method of introspection. Psychologists believed that the
mind could be studied best by training subjects to look inside of their minds (to intro-spect)
and to report back what exactly they had observed.
Another psychologist of the time, Watson, poked some holes into the method of
introspection. He identified two limitations of introspection: the reports are not falsifiable (1),
and the reports would be too variable (2) (meaning that you do not know by what the
differences in the reports are caused).
Behaviourism
Watson rejected the idea of studying the mind entirely; it is non-observable and
non-objective to study the mind, and therefore it does not meet the criteria of the scientific
method. He believed that a focus on behaviour was more appropriate. Thus, there was no
longer a focus on consciousness, but now on experience, and learning; behaviourism.
Just like Watson poked holes into introspection, Chomsky did just that with
behaviourism. He identified an important limit of behaviourism; it is unable to explain creative
processes such as language. (e.g. Skinner explained from a behaviourist POV that language
is learned through the way people respond to verbal behaviour, but that does still not explain
how, for example, completely new sentences can be formed and understood by others -
language also does not need to be reinforced).
The eventual downfall of behaviourism was caused by the limitations of
reinforcement (1), and upcoming cognitive models based on the computer metaphor (2).
Toward cognitive psychology
Cognitive models based on computer metaphor
The introduction of the electronic digital computer encouraged scientists to think of the
human mind organised in a similar way to the computer. They compared the ways of how
the human mind and how the computer generate output. This led to cognitive models based
on the computer metaphor.
Broadbent came up with a model featuring a selective filter (Broadbent’s filter of
attention) that would decide which information moved on for further processing, and which
does not (memory). Sternberg focused on the step after that, the temporary storage of
information. Information would get stored so it can later be used to perform a certain task,
this cognitive model assumed a STM and a LTM.
Thus, a grave difference between cognitive models and behaviourism is that
cognitive models focus on mental processes, and behaviourism on stimuli
and responses.
Sternberg conducted an experiment in which the subject had to
indicate, by using a ‘yes’ or ‘no’ lever, wether a certain number had
appeared in a previously shown row of numbers. Sternberg assumed that
,the numbers got stored into the STM (cognitive process). The results showed that mean
reaction time increases linearly as a function of the size of the memory set. This was the
case for both ‘yes’ and ‘no’ answers, indicating that all items in STM are serially scanned
before a decision is made. Scanning speed was about 40 ms (scanning the items in the
STM). This was determined based on the fact that reaction speed increased with 40 ms for
each extra number added to the list.
Sternberg’s experiment shows the fundamental principles of the field of cognitive
psychology: mental processes exist and can be examined through experimental
manipulation.
History of biological psychology:
Biological psychology is the study of the biological basis of human behaviour. It studies the
relationship between biological and physiological processes. An important milestone in the
history of biological psychology is Darwin’s theory of evolution. Because of this, one now
understand that mental processes and brain regions evolved to have specific
functions.There are two techniques that can be helpful in understanding the nervous system:
the electrical stimulation technique (1) and experimental ablation (2).
Electrical stimulation technique
The electrical stimulation technique is based on the fact that electrical signals are
transmitted through the nervous system, manipulate those and you can manipulate the
nervous system. Eventually you can create a map of brain regions and their functions (as
Penfield did). Electrical stimulation requires the removal of a part of the skull so the cerebral
cortex can be reached. In humans, this is only possible during brain surgery (with
permission). Scientists then rely on introspection of a patient when the result of the electrical
stimulation is not observable. This is a limitation of the electrical stimulation technique: most
of it has to be performed on animals, but they cannot introspect (so they cannot report
non-observable (to the scientists) experiences).
Experimental ablation
Experimental ablation is more intrusive and therefore only conducted in animals. It requires
the purposefully damaging of a specific brain area to examine its function. It allows scientists
to see what function of the brain is involved in what tasks.
Experimental ablation on humans is considered unethical, therefore to study brain
areas in humans, patients with naturally occurred brain damage, or surgically removed brain
areas, are used. A limitation of that is that the actual brain damage can only be established
with an autopsy (1), that it is difficult to determine what area is responsible for what task
when multiple brain areas are damaged/removed (2), and that it is difficult to generalise from
small-N or single-N studies (3).
Donders’ subtraction method
Information processing is a topic where biological and cognitive psychology very much are
combined.
Donders’ subtraction method provides insight in how long mental processes can
take. Donders stated that the duration of a mental process can be measured by having
subjects perform two nearly identical tasks, the only difference would be that one task has
critical process and the other does not. For example, the simple RT (go-task)(respond to
,specific stimulus: requires discrimination/critical process) and the go/no-go task (respond to
all stimuli: does not require critical process). To determine the time necessary to discriminate
between stimuli (DT), Donders’ substraction method can be used: DT = simple RT -
go/no-go task
*The reaction time in go/no-go task is longer
The neuron and glial cells
● I know what types of neurons and glial cells exist, and understand their role in
the CNS
For starters, there are three types of neurons;
sensory neurons, interneurons, and
motorneurons. Sensory neurons sense what is
going on, and send that signal to the CNS via
interneurons. Interneurons connect sensory
and motor pathways, so the signal then is
connected to motor neurons, and muscles
contract.
Glial cells are cells, that besides neurons, make up the nervous system. They
do many things, such as offering support, and doing things for neurons because they
cannot do them themselves. Glial cells can be divided into microglia and macroglia.
Microglia are responsible for immunologic defence, and for the removal of dead cells
via a process called phagocytosis (breaking down and engulfing undesirable cells).
Microglia fight diseases in the nervous system, but in the case of dysregulated
immune system they can start attacking healthy neurons. An example of this is
multiple sclerosis (MS). MS is caused by microglia attacking the myelin on neurons,
disrupting electrical impulses along the nerve. As a result of the attack, plaques for in
the affected areas in the brain and spinal cord - leading to coordination, balance, and
cognitive impairments.
Macroglia consists of three types of glial cells: astrocytes,
oligodendrocytes, and Schwann cells. Astrocytes have multiple functions.
First, it provides structure and solidity to the CNS as it hangs in between
neurons, kind of like a big star (astron = star). They also isolate synaptic
clefts in order to make sure that when during chemical communication
between neurons, released neurotransmitters do not just go around
everywhere floating through the CNS and affecting other neurons. Lastly,
they are also tasked with the feeding of neurons with glucose. Due to the blood-brain
barrier, glucose cannot enter the brain by itself as the capillaries in many parts of the
brain do not have gaps to let molecules through. This is a nifty thing, as that way,
there is always control over what substances can (not) enter the brains fluids. The
astrocyte is able to extract glucose from the capillaries, and pass it on to the neurons
it has attached itself to.
Oligodendrocytes also have a crucial role within the CNS. They provide
neurons with their myelin sheaths by wrapping their arms around their axons multiple
times. One oligodendrocyte can create multiple myelin sheaths, and hangs in
between the axons of neurons like a spider.
Schwann cells are kind of like the little brother of oligodendrocytes. They also
are responsible for the creating of myelin sheats, but in the PNS. Another important
, difference between Schwann cells and oligodendrocytes, is that a single Schwann
cell can only form one myelin sheath by wrapping itself around the axon.
● I know what important structures of neurons are and what their functions are
The important structures as a neuron are as follows (from ‘head to toes’): The
dendrites are the branch-like structures on a neuron. They receive signals from other
neurons via synapses. A synapse between a presynaptic terminal button and
postsynaptic dendrite is called an axodendritic synapse.
Next is the soma (cell body). Inside of the soma excitatory and inhibitory
signals received from the dendrites are organised and weighed, potentially leading to
an action potential (in the case of more excitatory (EPSPs) than inhibitory signals
(IPSPs). Inside of the cell body are cell organelles (‘little
organs’): the nucleus (holds DNA and has pores for
mRNA transport for protein synthesis), the endoplasmic
reticulum (produces (rough ER contains the ribosomes),
stores, and transports proteins), the Golgi apparatus
(packs neurotransmitters into vesicles), lysosomes (for
removing the wase from the cytoplasm), and microtubuli
(the road systems than allow axoplasmic transport). A
synapse can also be formed on the soma, this is then
called an axosomatic synapse.
Then come the axon hillock and the axon itself. The axon hillock generates a
new action potential if the EPSPs and IPSPs combined reach the threshold of
excitation (-55mV) - it is like decision point. The axon itself allows the propagation of
an action potential. On an axon too can a synapse be formed, we call this an
axoaxonic synapse.
Now come the terminal buttons. Terminal buttons store vesicles filled with
neurotransmitters, that will be released into the synapse via a process called
exocytosis once an action potential takes place.
● I know how the membrane potential is supported
The term ‘membrane potential’ refers to a difference in the electrical charge of a
neuron. When a neuron is inactive (so, not busy firing), it is at the resting membrane
potential (ca. -65 to -70 mV) - the outside of the neuron is more positive than the
inside. Important ions involved in the support of the resting membrane potential are:
Na+ (sodium), Cl- (chloride), K+ (potassium), and A- (large negatively charged
proteins).
The largest concentration of Na+ and Cl- is outside of the cell, in the
extracellular fluid. Inside of the cell, there is a large concentration of K+ and A+. It is
important to note that the membrane of the neuron (made up of a double layer of
phospholipids) is not permeable for A-, so it cannot escape the cell. The other ions
can travel inside and outside of the neurons by means of the forces of diffusion and
electrostatic pressure. Diffusion refers to the process in which ions want to move
from areas of high concentration to areas of low concentration. Electrostatic pressure
refers to the process in which similarly charged ions repulse each other, but
differently charged ions attract each other (opposites attract).
Due to the forces of diffusion and electrostatic pressure, Na+ ions leak into
the neuron, and K+ ions leak out, they leak via leak channels. If this were to continue,
