Posts tagged psychosis
Abundant evidence exists that psychosis is more prevalent in urban areas as compared to rural areas. The fact that living in the city makes one vulnerable to psychosis is not up for debate – but healthy debate ensues about the mediating mechanisms.
Last year, Zammit et al claimed that the high incidence of psychosis in urban settings is a result of greater social fragmentation in urban areas.
Today I came across a study [pdf] that had nothing to do with psychosis and came up with this novel hypothesis that the mediating mechanism may be global versus local focus or processing style. If that seems farfetched, bear with me for a while.
First a bit of background, the new study was referenced by Christian Jarrett in a BPS research digest blog post in which he lucidly shows that it has been found that living in urban areas has been found to be associated with a propensity for global processing style (seeing the forest); while living in rural areas has been found to be associated with a local processing style (focusing on the trees and missing the forest).
The study itself is pretty straight forward; in one of the local/global task it used the famous Ebbinghaus illusion (see image) to measure the amount of bias towards global vis-a-vis local processing.
In the second task it used large, composite (global) shapes/letters made of small, parts (local) which were also themselves shapes/letters and then measured whether one was more drawn in making inferences/similarity based on global percepts or the local figurine.
The study measured this global vs. local bias in Himba society (Namibia) members who had varying level of exposure to urban environments as well as Japanese and British urbanites. What they found was that living in urban areas/ exposure to urban areas was significantly predictive of whether you would lean more towards more global mode of processing. The authors link this with more ‘visual clutter’ in the cities necessitating a global style of processing.
Christian mentions in passing the fact that autistic people have a very local bias of processing and are marked by weak central coherence; what he perhaps doesn’t realize is that psychotics, which have been conceptualized to lie diametrically opposed on a continuum from autistic, have a global processing bias and a strong central coherence.
Badcock and Crespi, and I even before them, have been crying from the rooftops to conceptualize psychosis and autism as diametrical disorders – and some investigators have paid heed. Suzzana N et al [pdf] have recently shown that as conceptualized by Badcock and Crespi , Autistics and Psychotics are actually at opposed ends of local vs global processing.
We refer particularly to Crespi and Badcock (2008), who make the novel claim that the autism and positive schizophrenia spectra are diametrically opposed. They argue that individuals with autistic traits and individuals with positive symptoms of schizophrenia (e.g., magical ideation, unusual perceptual experiences and paranoia) should exhibit opposite cognitive profiles. The current investigation focuses specifically on their claim that autistic and positive schizophrenia traits contrastingly affect preference for local (i.e., piecemeal) versus global (i.e., integrative) processing.
Crespi and Badcock (2008) argue that while autistic traits are associated with a preference for local over global processing, positive schizophrenia traits are associated with a preference for global over local processing. That is, these authors claim that while individuals with autism show a tendency to focus on detail or process features in their isolation, individuals with traits of positive schizophrenia show a tendency to look at the ‘bigger picture’ or process features as an integrated whole. Although a preference for local processing fits theoretically with the tendency of individuals with autism to notice minor features or changes to the environment that are often overlooked by others (Hayes 1987), the link between traits of positive schizophrenia and a preference for global processing is less obvious. It is hypothesized though, that a global processing style could contribute to the complex delusions and enhanced creativity for individuals with positive schizophrenia (Nettle 2006; Oberman and Pascual-Leone 2008), as well as the tendency of these individuals to make ‘‘loose” associations between words and between aspects of the environment (Maher 1983; Spitzer 1997; Spitzer et al. 1993). Importantly, the effect of such loose associations is that one thought does not logically relate to the next, and thus these associations may be strongly linked to the hallucinations and delusions experienced by individuals with positive schizophrenia. However, while there are potential links of local and global processing to features of autism and positive schizotypy, the preferred processing styles for individuals with autistic and schizophrenic traits are yet to be examined together in the one investigation. Therefore, the current study aims to provide the first complete empirical test of Crespi and Badcock’s claim regarding local-global processing.
And this is exactly what they found. They used an embedded figural task to assess the global vs. Local bias and their results showed that indeed psychosis prone individuals had a more global style of processing.
Now one thing I am good at is putting two and two together and the moment I saw the new study correlating global style with urban living, a lot of pieces fell into place. Form the above it is apparent that global processing style may be an intermediate mediating factor that leads to association between urban living and psychosis.
What neural mechanism may be involved?
To quote from the Suzzana et al paper again:
The contrasting preferences for local versus global processing are identified with differences in brain connectivity in particular (Crespi and Badcock 2008). Reference is made to both structural (intrahemispheric and interhemispheric) and functional connectivity. Specifically, Crespi and Badcock argue that the preference for local over global processing displayed by individuals with autistic traits, compared to controls or individuals low on autistic traits, is a result of increased connectivity within neural regions relative to decreased connectivity across regions (Courchesne and Pierce 2005a, b; Happe´ and Frith 2006). Crespi and Badcock then argue that schizophrenia is associated with decreased connectivity within neural regions relative to an increased connectivity across brain regions (Colger and Serafetinides 1990; Siekmeier and Hoffman 2002), leading individuals with traits of positive schizophrenia to favor a global (over local) processing style, compared to controls or people low on these traits. These differences in brain connectivity for autism and positive schizophrenia are said to be mediated, at least in part, by genomic imprinting.
While genomic imprinting may be one mechanism, maybe there is something about exposure to urban environments (maybe it’s ‘visual clutter’) that also has a similar effect on pruning of synapses and unduly affect local pruning at the cost of pruning between widely separated regions thus leading to global processing bias.
Instructive to pause here and note that in children they start with local bias and around 6 year of age revert to global bias that adults typically have and this is mediated by synaptic pruning. See this open access PLOS one article.
Thus, it seems Psychosis and the City are intimately connected; and that, this is because, to live in a city, you need to (de)focus on ‘the big picture’.
Caparos, S., Ahmed, L., Bremner, A., de Fockert, J., Linnell, K., & Davidoff, J. (2012). Exposure to an urban environment alters the local bias of a remote culture Cognition, 122 (1), 80-85 DOI: 10.1016/j.cognition.2011.08.013
Crespi, B., & Badcock, C. (2008). Psychosis and autism as diametrical disorders of the social brain Behavioral and Brain Sciences, 31 (03) DOI: 10.1017/S0140525X08004214
Zammit, S., Lewis, G., Rasbash, J., Dalman, C., Gustafsson, J., & Allebeck, P. (2010). INDIVIDUALS, SCHOOLS AND NEIGHBOURHOODS; A MULTILEVEL LONGITUDINAL STUDY OF VARIATION IN INCIDENCE OF PSYCHOTIC DISORDERS Schizophrenia Research, 117 (2-3), 181-182 DOI: 10.1016/j.schres.2010.02.223
Russell-Smith, S., Maybery, M., & Bayliss, D. (2010). Are the Autism and Positive Schizotypy Spectra Diametrically Opposed in Local Versus Global Processing? Journal of Autism and Developmental Disorders, 40 (8), 968-977 DOI: 10.1007/s10803-010-0945-7
The term Schizophrenia , as many of the readers will recall, was coined by Eugen Bleuler, a Swiss psychiatrist , who intended the ‘split personality’ to reflect the fact that there was an underlying dissociation between various functions like memory, cognition, emotion that are normally integrated in normal people.
He also gave the famous 4 a’s that he presumed lied at the core of the schizophrenia and were fundamental aspects of the disorder.
‘affect’: Inappropriate or flattened affect-emotions in-congruent to circumstances/situation.
‘autism’: social withdrawal- preferring to live in a fantasy world rather than interact with social world appropriately.
‘ambivalence’ : holding of conflicting attitudes and emotions towards others and self; lack of motivation and depersonalization.
‘associations’ : loosening of thought associations leading to word salad/ flight of ideas/ thought disorder.
Bleuler maintained that these distinctive and fundamental features identified and formed the core of Schizophrenia while the manifest symptoms like hallucinations and delusions (first rank symptoms as per Schneider) were peripheral and not that important).
The readers of this blog will also be familiar with the ABCD model of psychology where Affect, Behavior (social aspects), Cognition and Desire (motivation/ dynamics) are the four fundamental domains; it is easy to see how the four a’s of Bleuler map to the 4 domains of psychology and it seems that schizophrenics have major troubles in each domain:
affect: this directly maps to Affect dimension and inappropriate affect is a major core part of the syndrome.
autism: though named somewhat incorrectly the intent of autism was to catch the behavioral and social impediments of the schizophrenics.
ambivalence: here there are conflicts and ambiguities regarding what one desires; for self and for others; lack of motivation/conflicted motivation is significant at this dimension.
associations: here the cognitive underpinnings are all too evident- the thought disorganization and flight of ideas is all too cognitive in nature.
It is amazing how the insights of Bleuler from a century before lend themselves so easily to fit the ABCD framework. What do you think, a bit stretched? or have I started making loose associations myself ?
It has been this blog’s thesis that autism and its milder form autism spectrum disorders (ASD) are diametrically opposed to psychosis and its milder form schizotypy. In no area is this more apparent than in the perception or attribution of minds to others. It thus gave me immense pleasure to read this new article by Wegner et al that looks at how the perception of others’ mind is affected in different sub-clinical conditions like ASD, Schizotypy and Psychopathy.
Wegner et al review a great deal of literature to come to the conclusion that others’ mind perception is a two dimensional construct and that we typically attribute mind to an entity depending on whether the entity can experience like us and whether they have goals and agency like us. Thus people can differ in the perception of either Agency or Experience when they attribute mind to an entity. Also b reviewing the available literature they came to the hypothesis that ASD folks should attribute less of agency , but perhaps equal experience to other humans and other entities as compared to controls; Schizotypals on the other hand have been shown to attribute more of mind and in particular agency to other entities than human. They also hypothesized that owing to lack of empathy the psychoptahs might perceive all animals/humans as lacking experience and thus mind-deficient to an extent and subject to manipulation.
They used online surveys to ascertain scores on ASD, schizotypy and psychopathy and correlated that with mind perception and attribution inclinations. How they assessed mind perception was by letting the subjects ascribe perceived experience and perceived agency to nine entities viz. baby, dead woman, dog, God, man , robot, Superman, tree and woman. They performed a confirmatory factor analysis that confirmed that indeed mind perception has two components- Experience and agency.
They got results in line with their hypothesis. ASD folks did not differ in ascribing Experience to fellow humans but did differ in ascribing agency. Schizotypals on the other hand ascribed too much agency to Robots/animals etc; and in general attributing min dto even things like tress , god and dead woman. Psychopaths on the other hand showed reduced ascription of Experience to other humans as well as animals. As an interesting aside, psychopaths attributed more mind to superman perhaps self-identifying with the fictional character
Thus, though mind perception in both ASD and Schizotypy is distorted it is tilted one way in autism and the other way in psychosis. With clinical populations the authors hope to get even stronger results. I am pleased because finally people have started taking the autism is opposed to psychosis paradigm seriously and have started doing research around it that is leading to fruitful results and confirmations.
Another new study that I came across recently and would like to link to found that VPA (valproic acid) treated mice were indeed an apt model of autism in mice and had the same brain correlates and signatures as in Autistic people. It is worth noting that VPA/sodium valproate is used to treat psychosis and I have pointed earlier too how this indicates that autism and psychosis are di\ametrically opposed. It is good that we are getting multiple confirmations of the important autism-psychosis opposition theory.
Gray, K., Jenkins, A., Heberlein, A., & Wegner, D. (2010). Distortions of mind perception in psychopathology Proceedings of the National Academy of Sciences, 108 (2), 477-479 DOI: 10.1073/pnas.1015493108
A new paper by Ben Bashat et al extends their earlier findings that had found that there was accelerated maturation of white matter in children with Autism. In this new paper they use Tract Based Spatial statistics (TBSS) to determine the white matter integrity of children (age around 3 years) with Autism as compared to normal controls. Of course they used Diffusion tensor Imaging to find out Fractional anisotropy and other measures of white matter integrity.
Essentially they found that in some regions/tracts there was greater Fractional Anisotropy (FA) as compared to controls. These regions/tracts were genu and body of the corpus callosum (CC), left superior longitudinal fasciculus (SLF) and right and left cingulum (Cg). They also found that in areas of high FA there was corresponding decrease in Radial diffusivity (Dr). What this essentially means, to my naive mind, is that greater conductance or speed of action potential in axons would primarily be due to enhanced myelination which reduces leakage or lateral flow of AP.
I’ll like to contrast the results with an earlier study I had blogged about regarding creativity, psychopathology and white matter mylienation connection. As per that study an inverse relation was found between people high on creativity (divergent type) and Fractional anisotropy in frontal regions, i’e there was low FA. Also importantly there was increased Dr (radial diffusivity) in the same regions and thus the conclusion was that there was reduced myelination in those areas which meant reduced signal transmission speed and more signal leak . It is notable that that study too used DTI and Tract based Spatial statistics (TBSS) analysis method to arrive at their conclusions.
Regular readers of this blog will know my fanaticism for Autism and Psychosis as opposites on a continuum theory. This new paper nicely fits in with my last post linking creativity/psychosis and white matter/myelination, I had as much surmised that Autism would show the opposite effect and have high FA and decreased Dr. It is heartening to note when such a relation is found and reported- goes to show the strength and ability to make predictions of the theory.
However, I would also like to point out and highlight that I believe Autistic spectrum is characterized by another type of ability – the savantic intelligence- that may be directly due to this white matter /excess myelination effect. Perhaps the signals travel so fast that decisions are made locally without the time available to get other far-0off regions involved- thus giving attention to details but inability to link disparate regions and ideas.
Weinstein, M., Ben-Sira, L., Levy, Y., Zachor, D., Itzhak, E., Artzi, M., Tarrasch, R., Eksteine, P., Hendler, T., & Bashat, D. (2010). Abnormal white matter integrity in young children with autism Human Brain Mapping DOI: 10.1002/hbm.21042
Ben Bashat, D., Kronfeld-Duenias, V., Zachor, D., Ekstein, P., Hendler, T., Tarrasch, R., Even, A., Levy, Y., & Ben Sira, L. (2007). Accelerated maturation of white matter in young children with autism: A high b value DWI study NeuroImage, 37 (1), 40-47 DOI: 10.1016/j.neuroimage.2007.04.060
Jung, R., Grazioplene, R., Caprihan, A., Chavez, R., & Haier, R. (2010). White Matter Integrity, Creativity, and Psychopathology: Disentangling Constructs with Diffusion Tensor Imaging PLoS ONE, 5 (3) DOI: 10.1371/journal.pone.0009818
Divergent thinking is influenced by dopaminergic function. Reuter  found a correlation between divergent thinking (the Inventiveness battery of the Berliner Intelligenz Struktur Test) and polymorphisms of the dopamine D2 receptor gene–DRD2 TAQ IA. Higher creativity scores were observed in carriers of the A1 allele. This polymorphism is unrelated to general intelligence , , which suggests that it is more specifically related to Glr (“long-term storage and retrieval”). This finding is in line with functional imaging research showing the D2 system to be involved in attentional set shifting and response flexibility, which are important components of divergent thinking . Furthermore, the finding indicates that divergent thinking is related to regional differences in D2 densities, since the DRD2 TAQ IA polymorphism has been shown to modulate D2 binding potential (D2BP) in both striatal  and extrastriatal regions .
Divergent thinking is traditionally measured using alternate uses test, for eg., in which a familiar object like brick is provided and subjects asked to name novel use for that object. The responses are marked for creativity as per the follwoing criterion:
- Fluency–the number of valid responses;
- Originality–how frequent the participant’s responses were among the responses of the rest of the sample;
- Flexibility–the number of semantic categories produced;
- Switching–the number of shifts between semantic categories;
- and Elaboration–how extensive each response is (if the task involves producing more than single words)
The main findings of the study was that dopamine D2 binding potential (D2BP) receptor density in thalamus correlated negatively with divergent thinking and creativity scores. Here is how the authors interpret the results:
Based on the current findings, we suggest that a lower D2BP in the thalamus may be one factor that facilitates performance on divergent thinking tasks. The thalamus contains the highest levels of dopamine D2 receptors out of all extrastriatal brain regions , . Decreased D2BP in the thalamus has been suggested, firstly, to lower thalamic gating thresholds, resulting in decreased filtering and autoregulation of information flow  and, secondly, to increase excitation of cortical regions through decreased inhibition of prefrontal pyramidal neurons , , . The decreased prefrontal signal-to-noise ratio may place networks of cortical neurons in a more labile state, allowing them to more easily switch between representations and process multiple stimuli across a wider association range . This state, which we hereforth will refer to as the “creative bias”, could benefit performance on tasks that involve continuous generation and (re-)combination of mental representations and switching between mind-sets. The creative bias could also explain why the different measures of divergent task performance correlate: A decreased signal-to-noise ratio in thalamus would decrease information gating and possibly increase fluency; decreased signal-to-noise ratio in cortical regions should better enable flexibility and switching between representations; similarly, the associative range should be widened and selectivity should be decreased which might spur originality and elaboration.
Besides carrying benefits related to fluency and switching, the decreased signal-to-noise ratio associated with the creative bias should be disadvantageous in relation to tasks that require high levels of selective attention. Some support for this prediction can be taken from Dorfman  who showed that the greater a person’s divergent thinking scores, the slower his or her reaction times were on a negative priming task requiring the inhibition of interfering information. Furthermore, the creative bias may also bring a risk of excessive excitatory signals from the thalamus overwhelming cortical neurotransmission, with ensuing cognitive disorganization and positive symptoms . It is thus tempting to suggest that dopaminergic modulation of neurotransmission mediated through dopamine D2-receptors could be one of the mechanisms which associate creativity with positive psychotic symptoms. Interestingly, positive symptoms are not necessarily related to problems in executive function, at least not to the same extent as negative symptoms , which indicates that in the creative individual “blind variation” might be affected without a concomitant decline in “selective retention”. It can be speculated that aberrant thalamic function may promote unusual associations, as well as improved performance on divergent thinking tests in healthy individuals, in the absence of the detrimental effects typically associated with psychiatric disorders. In other words, thinking outside the box might be facilitated by having a somewhat less intact box.
In plain English speak, the same decreased signal-to-noise ratio in perfrontal regions that gives rise to creativity also gives rise to proneness to psychosis. The more the noise that is introduced the greater the chances that the ideas generated by ‘blind variation’ are more creative; if the ‘selective retention’ procedure is also defective or loosened to an extent, it may result in psychopathology and psychosis, while if intact it leads to creativity. Thus while one factor , that of loosening of associations, flexibility and set switching is common to both psychosis and creativity, the defects in selective retention may be the crucial factor that distinguishes brains from bonkers.
de Manzano, ?., Cervenka, S., Karabanov, A., Farde, L., & Ullén, F. (2010). Thinking Outside a Less Intact Box: Thalamic Dopamine D2 Receptor Densities Are Negatively Related to Psychometric Creativity in Healthy Individuals PLoS ONE, 5 (5) DOI: 10.1371/journal.pone.0010670