Recognition of Japanese kanji words in children with specific learning disorders: a preliminary study using magnetoencephalography.

INTRODUCTION

In Western countries, reading disorders are believed to be caused by phonological processing problems. Conversely, Japanese children with developmental dyslexia (DD) and developmental dysgraphia often have difficulty learning kanji that are ideographic characters. It is believed that kanji learning and alphabet learning have different pathologies, as the latter uses phonetic character. In this study, we aimed to clarify the characteristics of kanji word recognition in Japanese children with DD and developmental dysgraphia using magnetoencephalography with high spatial resolution.

METHODS

Seven Japanese children with learning disorders, including 4 with DD and 3 with developmental dysgraphia, and 14 typically developing Japanese children (TDC) underwent magnetoencephalography while presented with kanji compounds and pseudo-kanji character sequences in their parafoveal visual fields, along with a foveal silent movie.

RESULTS

No differences were found between conditions or groups, except significantly smaller source activation in the posterior transverse region of the collateral sulcus (ptCoS) in the patient group, when presenting pseudo-kanji than presenting kanji, or than TDC when presenting deviant pseudo-kanji. The ptCoS activity from kanji exhibited a positive correlation with writing skills in the patient group, independently of attention deficit hyperactivity disorder (ADHD) symptom scores.

CONCLUSIONS

These results suggest that ptCoS activity during the presentation of kanji characters in Japanese children with DD and developmental dysgraphia reflects their writing ability, regardless of ADHD symptoms. Some forms of ptCoS dysfunction may be related to the neural basis of specific kanji writing functions in Japanese patients with DD and developmental dysgraphia.