Brain and behaviour
C1: The Science of Mind
What is Psychology?
Psychology is the scientific study of behaviour, mental processes, and brain functions. It studies the
mind: which is defined as the brain and its activities, including thought, emotions, and behaviour.
Psychology as a science originated from the merging of philosophy and natural sciences. Psychologists
attempt to answer questions once posed by philosophers using scientific research methods of the
natural sciences.
How Did the Science of Psychology Begin?
Wilhelm Wundt (1832-1920) is considered the first experimental psychologist. One of his students,
Titchener (1867-1923), expanded on Wundt’s views and fathered structuralism: the approach that to
understand the mind, it needs to be broken down into the smallest elements of mental experience.
To oppose structuralism, a group of psychologists in the early 1900s founded Gestalt psychology. This
theory suggests context is essential and when the mind is broken down, important information is lost.
Late 1800s, William James built on Darwin’s evolution theory with his functionalism: the idea that all
psychological mechanisms and behaviour is purposeful and contributes to survival.
In the first half of the 19th century, Sigmund Freud’s work on, among others, psychotherapy and
abnormal behaviour, dominated psychology. He fathered psychoanalysis to treat patients.
Opposing Freud’s beliefs about the selfish nature of humans, humanistic psychology emerged to
advocate the idea that humans are inherently good and motivated to learn and improve.
By the 1960s, American psychology was divided into Freudians and behaviourists, who studied the mind
purely by studying observable behaviours (mainly in animals). Thorndike (1874-1949) proposed the law
of effect, which suggested behaviours followed by pleasant or helpful outcomes persist and behaviours
followed by harmful or unpleasant outcomes cease to occur. Another influential behaviourist is Skinner
(1904-1990), who focussed on the effects of punishment and reward on future behaviour.
Behaviourism’s ignorance of thought and emotions related processes, such as information processing,
thinking, reasoning and problem solving, led to the birth of cognitive psychology, which focussed exactly
on these things.
What Are Psychological Perspectives?
,To find the answers to some problems, it is necessary to view it from different psychological
perspectives.
Biological psychology focusses on the relationship between mind and behaviour and their underlying
biological processes, such as genetics, biochemistry, anatomy, and physiology. A branch of this
perspective is evolutionary psychology, which builds on functionalism, to attempt to answer questions
on how our physical structure and behaviour have been shaped by their contributions to survival.
Cognitive psychology investigates information processing, thinking, reasoning and problem-solving.
Developmental psychology explores the normal changes in behaviour that occur across our lifespan.
Social and personality psychology describe the effects of the social environment, including social and
cultural diversity, and individual differences on the behaviour of individuals.
Clinical psychology seeks to explain, define and treat psychological abnormalities.
C1: The Cellular Foundations of Behaviour
1.1 The Biological Approach to Behaviour
The mind-brain problem embraces the question of how and why certain types of brain activity are
conscious.
Biological psychology studies physiological, evolutionary and developmental mechanisms of behaviour
and experience. It tries to make sense of how a mass of glia and neurons contributes to behaviour.
The three main points to remember:
1. Perception occurs in the brain. What you perceive is different from what is.
2. Mental activity and certain types of brain activity are inseparable. This position is called monism.
Dualism opposes this train of thought, by stating mind and matter are different entities.
3. People differ from one another, and the behavioural differences are rooted in brain differences.
Biological explanations of behaviours are split into four categories:
1. Physiological explanations relate behaviour to brain or organ activity.
2. Ontogenetic explanations describe how something develops.
3. Evolutionary explanations reconstruct the evolutionary history of a structure or behaviour.
They call attention to similar behaviour among related species.
4. Functional explanations describe why a structure or behaviour evolved as it did.
Next follow four reasons why animals are used in research, while there mainly is interest in the human
brain and behaviour:
, 1. Many behavioural mechanisms are similar across species and sometimes easier to study in
nonhuman species.
2. We are interested in explaining behaviour of certain animals.
3. What we learn about animals, sheds light on human evolution.
4. Legal or ethical restrictions prevent certain kinds of research on humans.
The legal standard for animal research emphasizes the three R’s:
1. Reduction of number of animals
2. Replacement of animals with for example computer models if possible
3. Refinement: modifying the procedure to reduce pain and discomfort
Minimalists accept certain types of animal research, depending on the type of animal, the amount of
distress and the value of the research. Abolitionists, however, advocate it is morally wrong to use
animals.
Research on humans often causes ethical issues. It is often not done on a group of enough diversity,
which has led for example to medication failing on certain groups of people because of slight genetic
differences.
1.2 Neurons and Other Cells
All animal cells have a nucleus, containing DNA. They also contain ribosomes, which synthesize proteins.
Some of the proteins roam freely, and others are transported to different locations by the endoplasmic
reticulum (ER). The metabolic activities that provide the energy the cell uses for activity, are performed
by mitochondria. Brain activity requires more energy than other organ activity, so mitochondria have a
big responsibility. The structure that separates the inside of the cell from the outside environment is
called the membrane.
The nervous system consists of neurons. Neurons are cells that receive information and transmit it to
other cells. They consist of a cell body or soma with a nucleus. Attached to this is an axon, which is often
covered in a myelin sheath with interruptions knows as nodes of Ranvier. The axon ends in branches
where information transmission is prepared, the presynaptic terminal. Afferent axons bring information
into a structure and efferent axons carry information away from a structure.
Also attached to the soma are branching fibres called dendrites that receive information and contain
dendritic spines, which increase the surface area available for synapses.
Neurons vary in size and shape depending on their location and function. Vertebrate motor neurons and
sensory neurons look quite different. If a neuron’s axon and dendrites are contained within a single
structure, we speak of an intrinsic neuron.
Between the neurons lie several types of glia:
, - Star-shaped astrocytes are active partners of neurons. They for example connect functionally
related axons, shield them from chemicals and help synchronize neurons, thus playing an
important role in generating rhythms.
- Microglia remove viruses from the brain without damaging neurons.
- Oligodendrocytes build myelin sheaths in the brain and spinal cord. In the peripheral nervous
system, Schwann cells take up this responsibility.
- Radial glia guide migration of neurons and their parts during embryonic development.
The membrane that excludes chemicals from the brain, is known as the blood-brain barrier. It’s made of
fats, so chemicals that dissolve in fat can cross it. Other vital substances like glucose and vitamin B1
(thiamine), which the body needs to use glucose, are pumped into the brain by special protein channels,
which is a form of active transport.
Gut bacteria can influence behaviour like mood or motivation.
1.3 The Action Potential
The phospholipid membrane of a neuron maintains an electrical gradient: a charge difference between
the inside and outside of the cell. This phenomenon is known as polarization. Neurons have a resting
potential of –70 mV.
This membrane is selectively permeable. It contains sodium-potassium pumps, which transports three
sodium ions out of the cell while drawing two potassium ions in through different voltage-gated
channels. Sodium ions want to continuously flow into the neuron because of the polarization and the
concentration gradient (since sodium ions are more abundant outside the cell). During a resting
potential, the pumps are closed.
Axons send messages through action potentials. When the membrane becomes depolarized, sodium-
potassium channels slowly open. When the potential reaches a threshold, action potentials unfold by
the all-or-none law: its amplitude and velocity are independent of the stimulus intensity. When the
action potential hits its peak in charge, sodium channels close and potassium starts flowing out to revert
to the resting potential. Local anesthetic drugs, like Novocain, which dentists use, attach to sodium
channels, preventing sodium from entering. This way, axons can’t transmit the message of pain to your
brain.
The action potential gives birth to a new action potential along the axon’s length. This is referred to as
propagation of the action potential.
Axons go through a refractory period. Sodium channels shut tightly to start the absolute refractory
period. During 1 ms, no action potential is possible. During the next 2-4 ms, the relative refractory
period, the rapid outflow of potassium lowers the charge below resting potential.
Myelinated axons transmit faster because the nodes of Ranvier admit sodium ions to enable saltatory
conduction (jumping of the action potential).
