Schizophrenia - Biological

Question 1

DOPAMINE HYPOTHESIS

Answer 1

Initial hypothesis
————————-

too much dopamine = symptoms of SZ
Supported by Griffith et al(1968)

Question 2

Griffith et al

Answer 2

induced psychosis in non SZ volunteers (4) by giving them dextro- amphetamine
-> showed onset of paranoid delusions and detached emotional responses

Question 3

REVISED HYPOTHESIS
different subtypes of dopamine receptors identified :D1-D5
(d2 mostly found in subcritical regions - limbic system)
Two pathways?

Answer 3

Mesolimbic pathway-

TOO MUCH->positive symptoms (overstimulation)

Mescortical pathway -
TOO LITTLE ->negative symptoms(motivation, cognition)

Question 4

EVALUATION OF DOPAMINE HYPOTHESIS

- strengths

Answer 4

May be genetic predisposition; twin & family studies

Gottesman(1991) > as genetic similarity increased so did probability o both individuals having SZ

Question 5

EVALUATION OF DOPAMINE HYPOTHESIS -weaknesses

Answer 5

Doesn’t clearly explain the root cause of dopamine imbalance?

Research disappointing - 108 genetic loci associated with SZ
THEREFORE MORE THAN JUST A FEW ABNORMAL GENES

Question 6

EVALUATION OF DOPAMINE HYPOTHESIS -weaknesses

Answer 6

Difficult to measure neurotransmitter levels
~ measure metabolite levels in cerebrospinal fluid via lumbar puncture (painful)

Dopamine broke down into metabolite HVA HOWEVER diet &drugs can affect levels so results are difficult to interpret as much variation

Question 7

EVALUATION of dopamine hypothesis -weaknesses

Answer 7

Seratonin receptors also blocked by antipsychotics

SO dopamine hypothesis alone cannot fully explain SZ

Cause or effect? - correlational

Question 8

STRUCTURAL ABNORMALITIES - Enlarge Ventricles

Answer 8

Cavities that transport cerebrospinal fluid

4 ventricles:
Left lateral, right lateral, 3rd and 4th

Those with SZ have LARGER ventricles than those without SZ

Question 9

ENLARGED VENTRICLES support ?

Answer 9

Weinberger -
Used CAT scans= found ventricular size was greater in 58 chronic SZ compared to 56 controls

Andreasen -
Through MRI scans found those with SZ had ventricles 20-50% LARGER

Question 10

STRUCTURAL ABNORMALITIES - Cortical Atrophy

Answer 10

• Loss of neutrons in cerebral cortex
• Atrophy widens the groves covering the cerebral cortex

Vita used scans to assess 124 SZ and 45 controls
> 33% with SZ had severe atrophy which was NOT related to age or family history but GENDER (mainly Male)

Question 11

STRUCTURAL ABNORMALITIES - Reversed Cerebral Asymmetry

Answer 11

Most without SZ have a larger LEFT hemisphere than right ~ this is reversed in those with SZ

language formation linked to left therefore DAMAGE= poverty of language( ALOGIA )

Question 12

WEAKNESS/STRENGTHS of Reversed cerebral asymmetry

Answer 12

DOES NOT ESTABLISH CAUSE AND EFFECT (studies after diagnosis)
»> possible brain adapts to cope with SZ and abnormalities are an EFFECT of the disorder

Lyon et al - ^ dosage of anti-psychs increased density of brain tissue
(Medication causes abnormalities?)

Question 13

Structural abnormalities - weaknesses/strengths part 2

Answer 13

McCarley et al -presence of enlarged ventricles is most reliable finding in research that uses brain scanning

Neurodevelopment link? (Exposure to noxious agents, or events in uteri, childhood which hinders healthy Brian development)

EG Distanto studied 60,000 patients - SZ more prevalent in those born in January(mothers exposed to flu virus or vitamin D deficiency)
WEAKNESS CORRELATIONAL MOST BORN IN JAN DO NOT DEVELOP SZ