International Meeting for Autism Research (London, May 15-17, 2008): Prefrontal cortical activation by switching stimuli in autism spectrum disorder and healthy controls assessed by near-infrared spectroscopy
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Prefrontal cortical activation by switching stimuli in autism spectrum disorder and healthy controls assessed by near-infrared spectroscopy

Thursday, May 15, 2008
Champagne Terrace/Bordeaux (Novotel London West)
N. Narita , Institute of Education, Bunkyo University, Koshigaya, Japan
A. Saotome , Education, Bunkyo University, Koshigaya, Japan
M. Tazoe , The Department of Clinical Psychology, JAPAN LUTHERAN COLLEGE, Mitaka, Japan
M. Narita , Developmental and Regenerative Medicine, Mie University, Tsu, Japan
K. Sakatani , Department of Neurological Surgery, Nihon University School of Medicine, Tokyo, Japan
Background: It is known that patients with autism spectrum disorder (ASD) often slow at switching between stimuli, which causes their lack in the appropriate behavior  expected in the schoolroom activities.

Objectives:   To investigate the activation of prefrontal cortex (PFC) in relation with switching stimuli in ASD patients, we measured the changes in brain oxygenation using near-infrared spectroscopy (NIRS), during a set of two tasks performed consecutive order .

Methods: Preliminary 11 high-functioning (IQ>70 by WISC III) autism spectrum disorder (ASD) patients (ages of 7-44) and 15 healthy controls (ages of 7-38) were studied.  PFC oxygenation was continuously measured by NIRS while the subjects were undergone two different tasks, i.e., a picture book reading task, followed by working memory task, in this order. Change in parameters of NIRS (oxygenated [oxy-], deoxygenated [deoxy-], and total hemoglobin [total-Hb ]) in PFC during each task were examined between control and ASD subjects.

Results:  In the control group, the most common NIRS parameter change observed in the PFC was a relative decrease or no change in oxy-Hb and total-Hb level, with a slight increase or no change in deoxy- Hb level during the reading task in both side of PFC. Interestingly, it is rapidly converted into an activated PFC status immediately after the task was switched to the working memory task, typically was accompanied with an increase in oxy- and total-Hb, with a decrease in deoxy-Hb level in control subjects.  In contrast, most ASD patients lack this PFC activation, and the oxy-Hb consistently showed relatively low level compared to the control subjects. The mean oxy-Hb during each task was calculated, which showed a significant difference (p<0.01, by 2-way anova) between the control and the ASD subjects.

Conclusions: The delayed oxygenation of PFC by switching stimuli was characteristic in the high-functioning ASD patients which suggest their core defect in complex information processing.

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