Professor Tim Crow and his research group developed and researched a specific hypothesis about the origins of psychosis - that it is associated with the unique human capacity for language.
Professor Crow arrived at this hypothesis by bringing together the fact that schizophrenia only appears to occur in humans and not in our closest relatives, chimpanzees. The same can be said of brain asymmetry: brain asymmetry has been linked to the capacity for language.
In the first CT scan study in 1976 Crow and colleagues at Northwick Park demonstrated that there are structural changes (e.g. a degree of enlargement of the cerebral ventricles) in individuals who have suffered from schizophrenia. Much subsequent work with MRI scans and in post-mortem brain studies has confirmed this and suggests that the changes are in the cerebral cortex and particularly are related to the subtle asymmetries that are characteristic of the human cortex. Through various experiments and observation, Crow has also proven that people with Schizophrenia show less left-sided dominance for language.
Crow is known for his suggestion that schizophrenia is a widespread genetic anomaly which arose quite recently in human evolution. He believes that it arose with the evolution of language and that the two are linked. In his argument, he says that schizophrenia is associated with atypical patterns of lateralisation – which is the differential functioning of the left and right cerebral hemispheres. He argues that through studying epigenetic variation, we can look at the changes in human evolution and see where the alterations in our genes have occurred, that lead to language development and henceforth schizophrenia. Crow reported that lateralisation occurs greater in males, who undergo more severe psychosis.
He has proposed that the origins of the psychoses relate particularly to those characteristics (e.g. cerebral asymmetry) that are associated with the specifically human capacity for language. This leads to a theory of the origin of psychotic symptoms – that they are associated with deviations in the subtle asymmetries of development of the cortex, and that the symptoms arise as confusions between thought and speech and through the abnormal attachment of meaning to perceived speech – and to its genetic basis in the change that led to the evolution of Homo sapiens as a species.
In 1980s, Crow published an article to the public that was known as a breakthrough in the field of research on schizophrenia. Crow focused on the classification of the symptoms of the disease instead of focusing on patients. Crow later introduced two syndromes of schizophrenia, one that is based on positive symptoms and the other on negative symptoms. These two syndromes are represented below as described by Crow:
|
Features |
Positive |
Negative |
|
Characteristic symptoms |
Hallucinations, delusions, and thought disorder |
Poverty of speech, flattening of affect, and social withdrawal |
|
State of illness |
Acute |
Chronic |
|
Response to anti-psychotic drugs |
Good |
Poor |
|
Intellectual impairment |
Absent |
Present |
|
Pathological process |
Increased dopamine receptors |
Structural brain abnormalities |
In 1993 Crow concluded that cerebral asymmetry was linked to genes on the X and Y chromosomes later drawing attention to an X chromosomal duplication to the Y short arm (the X transposed region – XTR) approximately 6 million years ago. The duplication generated a gene-pair (Protocadherin11XY) that codes for two cell surface adhesion factors expressed in the human brain and subject to a number of changes in the hominid lineage. According to Crow’s XY hypothesis the chromosomal and genetic changes are associated with the asymmetry of the brain (the torque) and with the evolution of the capacity for language, and a part of that variation constitutes the predisposition to psychotic illness.
In 2003 The Prince of Wales International Centre for SANE Research (POWIC) was opened on the co-located Warneford Hospital and University of Oxford’s Department of Psychiatry site. Crow was appointed the honorary scientific director of SANE whose aim was of finding the causes of and better treatment for serious mental illnesses, such as schizophrenia and depression.
Prior to the formation of SANE in 1986 there was a considerable paucity of research interest in schizophrenia and bipolar disorder. One of the charity’s endeavours has been to initiate and fund research into the causes and treatments of mental illness.
See a list of New Year’s Honours 2018 at the University of Oxford.
Sources for information of this article:
Sources
Crow TJ (2007) Nuclear schizophrenic symptoms as the key to the evolution of the human brain. Chapter 4.36 in JH Kaas & TM Preuss, Eds. Evolution of Nervous Systems vol 4. Primates. Academic Press, Amsterdam, pp 549-567.
Crow TJ (2012) Paul Broca and the evolutionary genetics of cerebral asymmetry. Human Nature, Royal Institute of Philosophy supplement 70: 132-147.
Li X, Crow TJ, Hopkins WC, Gong Q, Roberts N. (2018) Human torque is not present in chimpanzee brain. Neuroimage 165: 285-293.
https://en.wikipedia.org/wiki/Tim_Crow
https://en.wikipedia.org/wiki/The_Prince_of_Wales_International_Centre_for_SANE_Research