Comparison of changes in oxygenated hemoglobin during the tree-drawing task between patients with schizophrenia and healthy controls

Abstract

Background

Tree-drawing test is used as a projective psychological test that expresses the abnormal internal experience in patients with schizophrenia (SZ). Despite the widely accepted view that the cognitive function is involved in characteristic tree-drawing in patients with SZ, no study has psychophysiologically examined it. The present study aimed to investigate the involvement of cognitive function during tree-drawing in patients with SZ. For that purpose, we evaluated the brain function in patients with SZ during a tree-drawing task by using near-infrared spectroscopy (NIRS) and compared them with those in healthy controls.

Patients and methods

The subjects were 28 healthy controls and 28 patients with SZ. Changes in the oxygenated hemoglobin ([oxy-Hb]) concentration in both the groups during the task of drawing a tree imagined freely (free-drawing task) and the task of copying an illustration of a tree (copying task) were measured by using NIRS.

Results

Because of the difference between the task conditions, [oxy-Hb] levels in controls during the free-drawing task were higher than that during the copying task at the bilateral frontal pole regions and left inferior frontal region. Because of the difference between the groups, [oxy-Hb] levels at the left middle frontal region, bilateral inferior frontal regions, bilateral inferior parietal regions, and left superior temporal region during the free-drawing task in patients were lower than that in controls.

Conclusion

[oxy-Hb] during the tree-drawing task in patients with SZ was lower than that in healthy controls. Our results suggest that brain dysfunction in patients with SZ might be associated with their tree-drawing.

Keywords:

• tree-drawing test
• near-infrared spectroscopy
• cognitive function
• mnemonic retrieval
• executive function
• working memory
• attention

Acknowledgments

The authors thank all subjects in the present study.

Author contributions

Nakano, Morita, and Igimi designed the study concept. Nakano drafted the manuscript. Nakano, Morita, Igimi, and Ishii were involved in the recruitment of subjects and data acquisition. Morita and Shoji diagnosed the patients. The statistical analysis was performed by Nakano and Morita, and the results were interpreted by all the authors. The study was supervised by Uchimura. Nakano and Shoji wrote the final version of the manuscript. All the authors contributed to the critical revision and approved the final manuscript.

Disclosure

The authors report no conflicts of interest in this work.