Summary Cognitive Neuroscience
Chapter 1: A Brief History of Cognitive Neuroscience
Neuronal conduction: The transformation of information in the brain.
A Historical Perspective
Cognition: The process of knowing which arises from awareness, perception and
reasoning).
Neuroscience: The study of how the nervous system is organized and functions.
The human brain has only been around for 100.000 years, primate brains for 34-
23 million years. Even the early Greeks tried to explain the world and our place in
it in Oeidipus Rex; they did, however, not have the methodology to explore the
mind systematically through experimentation.
The Brain Story
Central question of neuroscience: Is the mind enabled by the whole brain working
together or do specific parts of the brain carry out specific tasks?
Thomas Willis is one of the founders of cognitive neuroscience (1621-1675) and
coined many terms still used today. He discovered that brain damage can cause
differences in behaviour. Franz Joseph Gall expanded this theory; he thought that
the brain was the organ of the mind and that specific faculties were located
in specific parts of the cerebral cortex. He also thought that the more
frequently used areas of the brain would grow (which could be seen from the
skull: phrenology). Flourens actually proved Gall’s theory that specific parts
have specific functions and developed the notion that the whole brain
participates in behaviour: aggregate field theory. In 1836, Dax discovered that
this was not true; he found that people with speech disturbances had lesions in
the left hemisphere. Around the same time, Jackson found the topographic
organization of the brain: A map of the body was represented across a particular
cortical area. Many regions of the brain contribute to a given behaviour.
In 1861, Paul Broca found the area responsible for speech (no speech at all but
able to understand): Broca’s area. In 1876, Wernicke found someone who could
talk freely but it didn’t make sense, nor did the patient understand language:
Wernicke’s area. Brodmann insicated 52 regions in the brain (1909).
Cytoarchitectonics: How cells differ between brain regions.
Syncytium: The belief that the brain was a continuous mass of tissues that
shares a common cytoplasm.
Neuron doctrine: Opposite to syncytium: The nervous system is made up of
individual cells, discovered by Cajal. He also discovered that the transmission of
information only happens in 1 direction: from the dendrites to the axonal tip.
NOW: The knowledge of parts must be understood in conjunction with
the whole.
,The Psychological Story
Before empiricism, there were philosophers about the brain. They had two main
theories:
1. Rationalism: All knowledge could be gained through the use of reason
alone;
2. Empiricism: All knowledge comes from sensory experience, the brain
begins as a blank slate.
a. Psychological associationists believed that a person’s experience
determined mental development. Ebbinghaus was one of the first
associastionists and one of the first who understood that internal
mental processes, such as memory, could also be analysed.
Thorndike was the first to find out that a response followed by a
reward would be turned into a habit. Watson, a key associationist,
claimed that only observable behaviour should be studied and that
learning is key. In 1950 the behaviourist theory was rejected by
Miller and with that, he became the founder of cognitive
neuroscience.
In Canada, things were more focused on biology than on psychology; the
Montreal procedure was invented: A procedure that destroys neurons that
cause epilepsy (found by stimulating different parts of the brain during surgery).
Hebb was convinced that the workings of the brain explain behaviour (biology
and psychology cannot be separated).
Chapter 3: Structure and Function of the Nervous System
Neurons: Basic signalling units that transmit information throughout the nervous
system.
Glial cells: Nonnneural cells in the nervous system with various functions such
as: structural support to other neurons, electrical insulation to neurons and
modulating neural activity.
Soma: The cell membrane that encases the cell body.
Cytoplasm: Salty fluid in which neurons are contained, made up of ions of
potassium, sodium, chloride, calcium and proteins for example.
Dendrites: Branching extensions of the neuron that receive inputs from other
neurons. Many dendrites have spines: knobs attached to the dendrites by little
necks that receive inputs from other neurons.
Axon: A single process that extends from the cell body and is the output of the
neuron. Some axons branch to from axon collaterals as to transmit to more
than one cell. Most axons are wrapped in myelin, which has gaps in it called
nodes of Ranvier.
Synapse: The place where two neurons come into close contact so that chemical
or electrical signals are passed on.
, Neuronal signalling
Neuronal signalling: The process of neurons receiving, evaluating and
transmitting neuronal information. Within a neuron, information is transferred by
means of changes in the electrical state of the neuron. Between neurons,
information is transferred by means of synapses, mediated by neurotransmitters
(sometimes also by electrical signals).
Presynaptic neurons: When the axon of a neuron connects onto other neurons.
Postsynaptic: When other neurons make a connection onto their dendrites.
Most neurons are both.
The Membrane Potential
When a neuron is in a resting state (=resting membrane potential), the inside
is more negatively charged than the outside (-70 millivolts inside).
Most of a neuron consists of fatty lipids that protect the inside of the neuron from
dissolving in the salty water outside from it. Also, ions (molecules or atoms that
have either a positive or negative charge) cannot move across the neuron
because of this protection.
The membrane (soma) of a neuron does not just consist of lipid, it also contains
ion channels: allow certain ions to flow down their concentration pumps. And it
contains ion pumps: Transport ions across the membrane against the
concentration gradients: from regions of low concentration to regions of high
concentration.
Ion Channels
The channels allow one type of ion to pass through the membrane. The ones
found in neurons concern Sodium (Na+), Potassium (K+), Calcium (Ca²+) and
Chloride (Cl-).
Permeability: The extent to which an ion can cross the membrane through a
channel. The membrane is more permeable to K+ than to Na+; there are more
K+ channels. There are also channels that can change their permeability for
specific ions: gating ion channels.
Ion Pumps
Na+ and Cl- concentrations are greater outside of the cell, while K+
concentrations are greater inside of the cell. Why is this? Because neurons use
active transport proteins = ion pumps (Na+/K+ pump) that pumps Na+ out
of the cell and K+ into the cell. This mechanism requires energy, because it
pumps against the concentration gradients. Each pump is an enzyme that
hydrolyzes adenosine triphosphate (ATP); the resulting energy is used to move
three Na+ ions out of the cell and two K+ ions into it.
The inside and outside voltages of a cell are different because a cell is more
permeable to K+ than to Na+. Therefore, the inside is more negative than the
outside, which creates an electrical gradient. Because of the negative charge
of the inside of the neuron, the positively charged K+ ions are drawn back into
the neuron. Eventually, the forces pushing K+ out are equal to the forces drawing
