Biological Explanations for Schizophrenia: Structural

- Enlarged ventricles; reversed cerebral asymmetry; cortical atrophy. - Differences in brain structure may affect neuronal activity & cognitive functioning = a biological explanation of schizophrenia.

- Cavities in brain that produce & transport cerebrospinal fluid (CSF). - Protection; buoyancy & chemical stability in central nervous system (CNS). Handwritten notes also identify waste removal & nutrient delivery.

- 4 ventricles. Left & right ventricles extend into frontal; occipital & temporal lobes. - One between left & right thalamus; one between pons & medulla oblongata.

- Enlarged ventricles -> reduced neuronal activity in specific brain regions -> impaired language & other schizophrenia symptoms. - Enlargement in left temporal region may create added pressure on language-related areas identified as Wernicke's / Broca's areas -> impaired language processing / proficiency -> symptoms such as alogia. - Increased pressure on brain; used in the explanation linking ventricular enlargement to pressure on language areas.

- CAT scans comparing 58 individuals with chronic schizophrenia & 56 control participants. - Ventricles larger in chronic schizophrenia group than control group. - MRI scans: individuals with schizophrenia had ventricles 20-50% larger than controls. - Abnormally enlarged ventricles occur in some individuals with schizophrenia = empirical evidence for structural abnormalities.

- Right hemisphere larger than left in individuals with schizophrenia; opposite to pattern described for neurotypical brains. - Damage / deterioration to left hemisphere -> disruption of normal language functioning. - CAT scans of differently handed individuals with schizophrenia. - Increased reversals in frontal & occipital lobes; found only in individuals with schizophrenia who had no other atrophies.

- Degenerative loss of neurons / cortical tissue in cerebral cortex; may be localised or general. - Localised atrophy affects cognitive functions associated with affected cerebral cortex. - Grooves (sulci) widen as cortical tissue is lost. - Printed slide = 20-35% of people with chronic schizophrenia; handwritten version = 29-35%. Both figures appear in the source.

- CAT scans: 33% of individuals with schizophrenia showed moderate to severe cortical atrophy. - Relationships between atrophy; gender & ventricular enlargement.

- Neurotypical = typically less than 10 mm wide; schizophrenia = enlarged ventricles. - Neurotypical = approximately 86 billion neurons; schizophrenia = reduced neurons. - Neurotypical = left hemisphere typically larger than right; schizophrenia = reversed cerebral asymmetry; right larger than left. - Neurotypical = smaller grooves; schizophrenia = larger sulci across cerebral cortex.

- Lack of replicability / consistency; difficulty establishing cause & effect; lack of diagnostic specificity & sufficiently advanced scanning; neurodegenerative vs neurodevelopmental explanations. - McCarley et al. (1999); Lyon et al. (1981); Roy et al. (1998); Mathalon (2003).

- Structural abnormalities are not consistently reproduced across studies or all individuals diagnosed with schizophrenia = lack of replicability & consistency. Brain differences therefore cannot automatically be treated as universal indicators of schizophrenia. - Enlarged ventricles = most reliable physical indicator in schizophrenia. However; structural abnormalities were not consistently found across all affected individuals. - Age; sex / gender & symptom severity influence prevalence & pattern of brain damage. Individual differences help explain why findings vary across samples -> brain changes are not universal to every person with schizophrenia. - Researchers must account for individual participant variables instead of assuming a universal structural pattern. More precise detection techniques are needed for subtle anatomical / physiological differences -> inconsistency limits assigning schizophrenia's origins to brain structure alone.

- Unclear whether abnormalities cause schizophrenia or arise as a byproduct of living with it. Environmental factors & treatment history can alter brain tissue over time -> structural differences may follow the condition rather than explain its origin. - Higher doses of antipsychotic medication correlated with decreased brain tissue density. - Observed abnormalities may reflect long-term medication effects or illness progression. Reduced brain tissue density / cortical atrophy may therefore be a treatment effect or artifact rather than schizophrenia's primary aetiology. - Brain scans showing structural abnormalities do not establish those abnormalities as original causes. Medication; environmental influences & illness progression complicate interpretation -> cause & consequence remain difficult to distinguish.

- Reduced brain volume & enlarged ventricles are not exclusive to schizophrenia = similar structural findings may occur in other disorders. - Similar structural anomalies present in bipolar disorder & schizoaffective disorder; these conditions also share overlapping symptom profiles. - Current neuroimaging technology is described as insufficiently sophisticated to isolate subtle differences distinguishing these disorders. Shared abnormalities & overlapping symptoms make it difficult to identify which condition a structural pattern indicates. - Structural scans alone cannot provide a refined / definitive differential diagnosis. Lack of specificity & limited detection of subtle differences restrict their value in distinguishing schizophrenia from bipolar or schizoaffective disorder.

- Unclear whether schizophrenia originates in early neurodevelopmental factors or neurodegenerative processes involving progressive brain tissue loss after onset = uncertainty about how structural differences arise & develop. - Neurodevelopmental = exposure to noxious agents in utero; during childhood or adolescence. Neurodegenerative = progressive post-onset brain tissue loss. - Dual-process model: schizophrenia = combination of early neurodevelopmental vulnerability & subsequent neurodegenerative decline. - Schizophrenia may involve both early vulnerability & later degeneration -> complex; evolving neurobiological process. Viewing it through a purely static structural lens oversimplifies this process = reductionist in nature; structural differences alone do not capture its development over time.