A case of isolated dystextia due to subcortical infarction: a novel condition of digital device era.

BACKGROUND: In recent years, cases of dystextia (texting disabilities) and dystypia (typing disabilities) have been reported. However, reports describing isolated dystextia without aphasia or other cognitive impairments are rare, and the detailed pathophysiology is not fully understood. Most Japanese people use the alphabetical spelling system (Romaji) for texting and typing. Herein, we report the case of a man with isolated dystextia and dystypia resulting from Romaji conversion difficulties. CASE PRESENTATION: A 48-year-old, right-handed Japanese man developed texting and typing difficulties. The standard neuropsychological tests showed no signs of aphasia or other cognitive impairments, except for slight executive dysfunction. Thus, isolated dystextia and dystypia were diagnosed. Furthermore, the patient experienced Romaji conversion difficulties. Magnetic resonance imaging revealed a subcortical infarction in the left cerebral hemisphere. Single photon emission tomography revealed hypoperfusion, including in the left dorsolateral frontal cortex. CONCLUSIONS: The left dorsolateral frontal cortex may be related to Romaji conversion in Japanese individuals. Therefore, diaschisis of the left dorsolateral frontal cortex due to subcortical lesions may have impaired Romaji conversion, leading to dystextia and dystypia, in this patient.

Orthographic properties of distractors do influence phonological Stroop effects: Evidence from Japanese Romaji distractors.

In attempting to understand mental processes, it is important to use a task that appropriately reflects the underlying processes being investigated. Recently, Verdonschot and Kinoshita (Memory & Cognition, 46, 410-425, 2018) proposed that a variant of the Stroop task-the "phonological Stroop task"-might be a suitable tool for investigating speech production. The major advantage of this task is that the task is apparently not affected by the orthographic properties of the stimuli, unlike other, commonly used, tasks (e.g., associative-cuing and word-reading tasks). The viability of this proposal was examined in the present experiments by manipulating the script types of Japanese distractors. For Romaji distractors (e.g., "kushi"), color-naming responses were faster when the initial phoneme was shared between the color name and the distractor than when the initial phonemes were different, thereby showing a phoneme-based phonological Stroop effect (Experiment 1). In contrast, no such effect was observed when the same distractors were presented in Katakana (e.g., "くし"), replicating Verdonschot and Kinoshita's original results (Experiment 2). A phoneme-based effect was again found when the Katakana distractors used in Verdonschot and Kinoshita's original study were transcribed and presented in Romaji (Experiment 3). Because the observation of a phonemic effect directly depended on the orthographic properties of the distractor stimuli, we conclude that the phonological Stroop task is also susceptible to orthographic influences.

Pure agraphia in Romaji after left inferior frontal gyrus infarction: A case of selective deficit in syllable-to-grapheme conversion in Japanese.

The Japanese writing system employs two distinct categories of characters: Kana and Kanji. The difference between Kana and Kanji writing corresponds roughly to that between phonological and lexical systems in Western languages. When typing, most Japanese use alphabetical characters based purely on phonological rules. In particular, the Romaji system is used, in which a syllable consists of a single vowel, a consonant-vowel compound (e.g., ka, ki), or a sequence of consonant-y(semivowel)-vowel (e.g., kya, kyu). We describe a right-handed Japanese patient who developed pure agraphia that affected Romaji writing but preserved Kana and Kanji writing and who had a lesion in the left pars opercularis of the inferior frontal gyrus that extended to the anterior precentral gyrus. The patient demonstrated literal paragraphia in spelling Romaji across modalities. Our findings suggested that the patient's agraphia in Romaji after a confined left frontal infarction was manifested by a selective impairment in syllable-to-grapheme conversion.