Creativity and positive symptoms in schizophrenia revisited: Structural connectivity analysis with diffusion tensor imaging
Introduction
Creativity has long been thought as the ability to produce original, novel, flexible, and useful ideas that are free from established mental habit. One of the most commonly used definitions is “the production of effective novelty” (Mumford, 2003). A number of factors are thought to be related to creativity, such as divergent thinking (Guilford, 1959), openness (Dollinger et al., 2004), handedness (Shobe et al., 2009), language (Leonhard and Brugger, 1998), problem solving, adaptability, self-expression, quality of life (Runco, 2004), artistry (Bhattacharya and Petsche, 2002, Bhattacharya and Petsche, 2005), magical ideation (Badzakova-Trajkov et al., 2011), and schizotypy (Fisher et al., 2004).
Both creativity and schizotypy are suggested to be manifestations of the hyperactivation of unusual or remote concepts/words (Mohr et al., 2001). Therefore, relationships between creativity and schizophrenia-spectrum disorder have been widely investigated (Sass, 2000, Nelson and Rawlings, 2010). Indeed, a study reported that schizophrenia patients tended to engage in artistic occupation (Kyaga et al., 2011). However the results of studies on creativity in schizophrenia are varied. Some studies reported enhanced mental imagery manipulation in schizophrenia using jigsaw puzzle task (Benson and Park, 2013), whereas other studies reported lower figural creativity using the Berlin Intelligence Structure Test (Jaracz et al., 2012) or lower creativity in general using design, idea, and word fluency tests (Nemoto et al., 2007) in schizophrenia. One possible reason for these inconsistencies may be found in the differences in definition and measurement methods of creativity. Furthermore, Tsakanikos et al. reported that increased positive schizotypy or positive symptoms had relationships with increased creativity, whereas negative schizotypy or negative symptoms could be related to reduced creativity (Tsakanikos and Claridge, 2005). Thus, the clinical background of patients should also be taken into account in respect to such inconsistencies.
In previous literature investigating the semantic priming effect, it has been suggested that enhanced automatic spreading activation in semantic networks is associated with creativity (Tsakanikos and Claridge, 2005), and might underlie some of the positive symptoms (Spitzer, 1997) such as thought disorder (Kreher et al., 2008), hallucination (Lindamer and Whitman, 1997, Kerns et al., 1999), or delusion (Debruille et al., 2007) in schizophrenia. Thus, it is reasonable to ask the following questions: what is the difference between creativity and positive symptoms, or why could hyperactivation result in innovative output in one case, but in psychotic symptoms in another? Fisher et al., in dealing with these questions, suggested that frontal lobe functions, i.e., executive functions such as monitoring, controlling, or inhibiting ability, play pivotal roles in the use of semantic information and differentiate creativity from psychopathology (Fisher et al., 2013).
Therefore, in this study, we aimed to examine creativity in schizophrenia patients with multiple creativity measures with and without semantic contents, and to investigate its impact on psychopathology, especially on positive symptoms. We predicted that overall creativity performance in schizophrenia might increase or decrease depending on the proportion of positive and negative symptoms, and that some creativity measures would positively correlate with positive symptoms. Furthermore, we hypothesized that this correlation between creativity and pathological, positive symptoms would be underpinned by the pathology of the frontal lobe structure. One of the influential hypotheses of schizophrenia, “the disconnection hypothesis” (Friston, 1998), assumes that dysconnectivity among multiple neural systems might underlie some symptoms of schizophrenia, mainly positive symptoms. We therefore utilized diffusion tensor imaging (DTI) to investigate the structural connectivity, and examined its relation with creativity and psychopathology.
Section snippets
Participants
Forty-three patients with schizophrenia (22 men and 21 women, age = 37.37 ± 8.66) were recruited. Each patient fulfilled the criteria for schizophrenia based on the Structural Clinical Interview for DSM-IV Axis I Disorders (SCID) Patients Edition, Version 2.0. None of the patients were comorbid with other mental disorders. Predicted IQ was measured using the Japanese Version of the National Adult Reading Test (JART) short form (Matsuoka et al., 2006, Matsuoka and Kim, 2007), which is thought to
Scores of fluency tasks and PDI
Demographic and clinical data are shown in Table 1a. Many patients had mild symptom severity. The scores of fluency tasks and PDI are shown in Table 1b. Inter-rater reliabilities of scoring fluency tasks between two examiners, “SS” and “MK”, were P = .98 in Idea Td, .96 in Idea Tm, .95 in Idea Ti, 1.00 in Design Td, 1.00 in Design Tm, and 1.00 in Design Ti. An independent sample t-test revealed that Idea Tm, Idea Ti, Verbal C, and Verbal L were significantly lower and PDI was higher in
Discussion
Using comprehensive creativity scales and structural connectivity with DTI, we found decreased idea and verbal fluency in general, but retained design fluency in schizophrenia. In the schizophrenia group, phonological fluency was positively correlated with delusion severity. DTI analyses revealed correlation between frontal white matter integrity and phonological fluency, and between widespread white matter region and delusion severity in schizophrenia. These two results showed substantial
Role of funding source
This work was supported by grants-in-aid for scientific research A (24243061), B (23390290), S (22220003), and on innovative areas (23118004, 23120009), from the Ministry of Education, Culture, Sports, Science and Technology of Japan (MEXT), and Grants-in-Aid for Young Scientists A (23680045), B (23791329) from the Japan Society for the Promotion of Science. A part of this study is the result of Development of BMI Technologies for Clinical Application carried out under the Strategic Research
Contributors
Shuraku Son designed the study and wrote the protocol, and also managed the literature searches and analyses and wrote the first draft of the manuscript. Shuraku Son, Manabu Kubota, and Jun Miyata undertook the analysis and interpretation of clinical and psychological data. Shuraku Son performed data processing and statistical analyses, under technical supervision by Manabu Kubota, Jun Miyata, Toshihiko Aso, Shin-ichi Urayama, Hidenao Fukuyama, Toshiya Murai, and Hidehiko Takahashi. All authors
Conflict of interest
All authors declare that they have no conflicts of interest in this study.
Acknowledgment
The authors wish to extend their gratitude to Kimito Hirose, Kousuke Tsurumi, Masanori Isobe, Miki Ono, Naoto Yokoyama, and Yasuo Mori for their assistance in data acquisition and are especially thankful to the patients and volunteers for participating in the study.
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