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Chapter 16

PSYC 211 Chapter Notes - Chapter 16: Dopamine Hypothesis Of Schizophrenia, Neural Development, Movement Disorder


Department
Psychology
Course Code
PSYC 211
Professor
Yogita Chudasama
Chapter
16

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Chapter 16: Schizophrenia and the Affective Disorders
Notes taken by: Ashley Brown
Contact for mistakes: Ashley.brown@mail.mcgill.ca
Mental disorders include deficient or inappropriate social behaviours,
illogical/incoherent/obsessional thoughts, inappropriate emotional responses (incl.
depression, mania, or anxiety), delusions, and hallucinations.
- caused by abnormalities in the brain both structural and biochemical
Schizophrenia
Description
Has been around for thousands of years. The major symptoms are universal. Literally
means “split mind” but does not imply a split or multiple personality.
Schizophrenia: a serious mental disorder characterized by disordered thoughts,
delusions, hallucinations, and often bizarre behaviours; has three categories of symptoms:
(1) positive, (2) negative, and (3) cognitive
- positive symptoms: a symptom evident by its presence, such as delusions,
hallucinations, or thought disorders
o appear to involve excessive activity in some neural circuits that
include dopamine as a NT
o thought disorder: disorganized, irrational thinking; probably most
important symptom can’t differentiate between plausible
conclusions and absurd ones
loose associations
incoherence
neologism
o delusion: a belief that is clearly in contradiction to reality
persecution: false beliefs that others are plotting and conspiring
against oneself
grandeur: false belief’s in one’s power and importance, like
they think they have godlike powers or special knowledge no
one else possesses
control: the person believes that he or she is being controlled
by others through such means as radar or a tiny radio receiver
implanted in his or her brain
o hallucination: perception of a nonexistent object or event
with schizophrenia are most commonly auditory, typically
voices talking to the person
olfactory hallucinations are also seen often making them think
someone is trying to kill them with poison gas
- Negative symptom: a symptom characterized by the absence of behaviours
that are normally present: social withdrawal, poverty of speech, flattened
emotional response, lack of affect, and reduced motivation

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o Anhedonia: inability to experience pleasure
o Not specific to schizophrenia
o Both these and cognitive symptoms appear to be caused by
developmental or degenerative processes that impair the normal
functions of some of regions of the brain
- Cognitive symptom: a symptom that involves cognitive deficits, such as
difficulty in sustaining attention, deficits in learning and memory, poor
abstract thinking, and poor problem solving
o Low psychomotor speed or the ability to rapidly and fluently perform
movements of fingers, hands, and legs
o Both these and negative symptoms are not specific to schizophrenia
(both involved in many neurological disorders esp. those involving
damages to frontal lobes)
Symptoms appear gradually and insidiously over a period of 3 to 5 years
- negative symptoms first to emerge
- then cognitive
- positive symptoms follow several years later
Heritability
Appears to be heritable strong evidence given by adoption and twin studies
Not one gene either several genes or having a “schizophrenia gene” that imparts a
susceptibility to develop schizophrenia, the disease being triggered by other factors
- strong evidence for the latter
Another genetic factor is paternal age
- children of older fathers are more likely to develop schizophrenia
- mutations in the spermatocytes has been linked as a cause for the increased
incidence of schizophrenia
Epigenetic (on top of the genes) mechanisms may contribute to the development of
schizophrenia in addition to mutations
- epigenetic changes might be responsible for a decreased expression of reelin,
a protein involved in neuronal migration
Abnormalities in non-coding RNA (ncRNA) may be responsible for excessive or
inadequate amounts of normal proteins during critical stages of development, which
could produce effects as deleterious as those caused by mutant proteins
Pharmacology of Schizophrenia: The Dopamine Hypothesis
Evidence suggest that the positive symptoms of schizophrenia are caused by a
biochemical disorder.

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- the dopamine hypothesis suggest that the positive symptoms are caused by
over activity of synapses between dopaminergic neurons of the VTA and
neurons in the nucleus accumbens and amygdala
Effects of Dopamine Agonist and Antagonist
Chlorpromazine: a dopamine receptor blocker; a commonly prescribed
antischizophrenic drug
- not effective in treating neuroses or affective psychoses
- eliminates, or at least diminishes, positive symptoms (but not negative
symptoms
A lot of drugs made that relieve the positive symptoms all have in common the fact
that they block D2 and D3 dopamine receptors
There are drugs that produce the positive symptoms of schizophrenia
- amphetamine, cocaine, methylphenidate, and L-DOPA
- all are dopamine agonist
Mesolimbic pathway (which begins in the VTA and ends in the nucleus accumbens and
amygdala) is more likely to be involved with the positive symptoms of schizophrenia
- if reinforcement mechanisms were activated at inappropriate times then
inappropriate behaviours such as delusions might be reinforced
- amygdala is involved in conditioned emotional responses and it received a
strong projection for the mesolimbic dopaminergic system
The Search for Abnormalities in Dopamine Transmission in the Brains of Schizophrenic
Patients
Studies found that dopaminergic neurons in schizophrenic patients release more
dopamine
- amphetamines caused the release of more dopamine in the striatum of
schizophrenic patients than in normal subjects
- patients with greater amounts of dopamine release showed greater increases in
positive symptoms
Also a possibly the schizophrenic’s brains contain a greater number of dopamine
receptors
- post mortem studies found that their might be a modest increase in the number
of D2 receptors in the brains of schizophrenics
- unlikely that these increases are the primary cause of the disorder
Consequences of Long-Term Drug Treatment of Schizophrenia
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