INTRODUCTION TO NEUROPSYCHOLOGY Dr. Malcolm Hughes

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INTRODUCTION TO NEUROPSYCHOLOGY Dr. Malcolm
Hughes
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Watson defined psychology as the science of the
mind and in that respect, the subject of
psychology has focused on a range of topics which
reflect the manner in which human subjects behave.
Attempts to explain behaviour in terms of brain
mechanisms is also expressed by the term
biological psychology.
The subject is sub-divided into disciplines which
include a) Neuro-anatomy
b) Psycho-genetics
c) Psycho-endocrinology
d) Psycho-neuro-immunology
e) Psychopharmacology
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Biological psychology is defined as explaining
behaviour in biological terms considerable
emphasis in placed on the brain structure at a
cellular level and the associated processes e.g.
chemical mechanisms. Now recognised that chemical
energy within the brain can be converted into
various kinds of brain activity conversely,
brain activity, e.g. cognitive processes and
emotions, can instigate changes in the brains
chemistry resulting in other mental and
behavioural responses.
Biological Explanations of Human
Behaviour Example some psychologists would
advocate that anger is an experience that merely
reflects a pattern of activity within a specific
area of the brain, heightened by certain hormones.
A further suggestion is that the brain is
programmed by natural selection to enable such
experiences to happen. This implies a
psychogenic influence.
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Within these areas of study, the understanding of
the brain and its constituent parts have led to
substantial contributions to the relationship
between brain and behaviour.

Included among these areas are the physiological
mechanisms associated with the central nervous
system.
An overall understanding of the anatomy of the
brain structure reflects the diversity of the
individuals mental processes and behaviour. Some
structures can highlight these effects quite
significantly. Among such structures are
a) The thalamus
b) The hypothalamus
c) The hippocampus and amygdala
d) The corpus callosum
e) The cerebral hemispheres
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Neuro-transmitters These are chemicals released
at the synapse separating two sections along a
nerve fibre. It is now recognised that a large
number of chemicals function as neurotransmitters
within the brain.
The three major categories of neurotransmitters
are a) Biogenic amines (contain an amine (NH2
group) b) Amino acids derived from the
breakdown of proteins c) Peptides
Each neurone has the capacity to synthesise its
neurotransmitters from precursor molecules that
reach the cell by way of the blood, derived
originally from foods that the individual
ate. Many neurotransmitters are synthesised both
in the cell body and in the terminal, close to
the point of release. Under normal
circumstances, the brain maintains fairly
constant levels of each neurotransmitter, even
during periods of fasting.
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Lateralisation of Brain Function The hemispheres
of the cerebral cortex are not mirror images of
each other have a division of labour known as
lateralisation. Via the Corpus callosum, each
hemisphere deals with information from both sides
of the body.
It is only through damage to the C. callosum that
we come to recognise the effects of
lateralisation. Damage to the C. callosum is
sometimes used to minimise the effects of
epilepsy (in v. severe cases) has the effect of
reducing the effects of epileptic seizures
crossing from one hemisphere to the other.
Maturation of the Corpus callossum Matures over 5
to 10 years is one of the last brain structures
to attain full maturity due to this part of the
brain developing more axons in the C. callossum
than are actually needed at maturity. The brain
then selects certain axons, then discards the
remainder. Only those axons that connect to
similar cells actually survive.
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Short-Term Memory vs Long-Term Memory It is
possible to draw an unlimited number of
distinctions among different types of memory
memory of recent events (short-term) vs. a memory
of older events (long-term). A question arises
as to how such distinctions (if any) are
natural ones and which distinctions are not?
It appears likely that two functions can be
physiologically different if some procedure (e.g.
damage to a specific brain area) impairs one
function, while some other procedure impairs
another function. However, no researcher has
found any procedure that impairs one type of
memory without equally impairing the other.
Hebb (1949)distinguished between short-term and
long-term memory Short-term memory memory for
events that have just occurred. Long-term memory
past events that must be retrieved from storage
events not currently occupying the persons
attention.
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• Individuals with damage to the hippocampus can
  form new short-term memories, but have difficulty
  developing new long-term memories.
• Individuals with certain kinds of head trauma
  forget the events that occurred immediately
  before the trauma (events in short-term memory)
  without forgetting earlier events (that were in
  the long-term memory).
• Short-term memory has several properties that
  differ from those of long-term memory e.g.
  literary recall.

Consolidation of Long-Term Memories On a daily
basis, information passes into the short-term
memory. Of that, a tiny fraction becomes readily
available long-term memory, while a larger
fraction becomes harder-to-recall long-term
memory. i.e. there is a tendency to consolidate
or strengthen some short-term memories into
long-term memories, but the degree of
consolidation varies.
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Brain and Memory in Old and Young Question as to
why some people have better memories that others?
This is most noticeable among infants and older
people.
The reality is that both infants and old people
perform well on some memory tasks and poorly on
others e.g. infant amnesia when we remember few
events from the first 4 to 5 years of our
lives. In the first 4 or 5 years, we learn many
implicit memories but do not form many explicit
ones.
In this instance, infant memories resemble those
of people with hippocampal damage this is due to
the hippocampus not yet having fully matured
(Moscovitch, 1985).
Similarly, old people who have trouble with
recent explicit memory still manage to learn new
skills or adjust old skills. The prefrontal
cortex also deteriorates in old age the
deficits may be due in part to a declining number
of dopamine and nor-epinephrine synapses in the
prefrontal cortex.
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• Influence of Protein Synthesis on Learning and
  Memory.
• Proteins are essential building blocks of the
  body in relation to the nervous system, protein
  synthesis is necessary for
• growth of an axon or dendrite
• increase or decrease in the production of
  neurotransmitters
• alteration of any nerve receptor

It is recognised that the drugs which suppress
protein synthesis also impair long-term storage
of memory (in rats) although they do not impair
short-term memory (Davis Squire, 1984).
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The Neurobiology of Schizophrenia
The generic term schizophrenia constitutes a
group of disorders marked by a progressive
deterioration of personality and its link with
the world judgement, emotional stability and
thinking processes deteriorate. Can result in an
increase in problems in personal relationships
together with an inability to cope.
The condition is characterised by a deteriorating
ability to function in everyday life and some
combination of hallucinations, delusions, thought
disorders, movement disorders and inappropriate
emotional expressions. One of the difficulties of
schizophrenia is that affected people vary
considerably in both their behavioural symptoms
and their biological characteristics.
Until the 1980s the condition was responsible
for the bulk of patients in mental
institutions. Up to that period, 40 of all beds
in U.K. hospitals were designated for those with
mental conditions. 45 of those beds were
occupied by schizophrenic sufferers. The
incidence in the general population is in the
region of 0.85
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• Psychobiological Factors relating to
  Schizophrenia Brain Atrophy or Dysfunction
• Several lines of evidence point towards brain
  damage in schizophrenia. Based upon
• Forebrains of schizophrenics approx 6 lighter
  than those of others.

• Ventricles of the brain are larger than average.

• There are fewer neurones in the cerebral
  cortex, dorso-medial thalamus, amygdala and
  hippocampus.

• Schizophrenics also have lower-than-average
  levels of brain metabolism greater in the
  posterior part of the brain than the anterior.

• When performing certain tasks, schizophrenics
  fail to recruit extra activity in the frontal
  cortex when necessary therefore perform tasks
  poorly.

• Evidence indicates poor organisation of
  neurones, notably in the cerebral cortex a
  number of neurones remain in the white
  matter rather than migrate to the grey matter
  during brain maturation.

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Alzheimers Disease
Condition that becomes more prevalent with
increasing age can occur among a small group
before they are 40 or 50 years of age. By the
age of 65 74 less than 5 affected Among
those aged 85 approx. 50 affected
Symptoms begin with minor episodes of
forgetfulness. Later symptoms include Serious
memory loss, confusion, depression, restlessness,
hallucinations, delusions and disturbances of
eating, sleeping and other daily activities.
Alzheimers disease is associated with a
widespread atrophy of the cerebral cortex,
hippocampus and other areas. The most heavily
damaged is the entorhinal cortex, the portion of
the cerebral cortex that conducts the greatest
amount of communication with the hippocampus
acetylcholine producing neurones degenerate and
plaques (degenerated axons and dendrites) appear
in the damaged areas.
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Brain atrophy in Alzheimers Disease (b) compared
to the brain of a normal person (a) Note that
the cerebral cortex of the Alzheimic patient
(right) has gyri that are clearly shrunken in
comparison with those of a normal person.