Brain Areas Involved in Tactile Letter Recognition (graphesthesia)

J Korean Neurol Assoc > Volume 23(1); 2005 > Article

Journal of the Korean Neurological Association 2005;23(1): 49-54.

촉각에 의한 문자인식와 관련된 뇌영역

김광기, 우성호 이경민

강원대학교 의과대학 신경과학교실, 서울대학교 의과대학 신경과학교실*, 서울대학교 대학원 인지과학 협동과정†

Brain Areas Involved in Tactile Letter Recognition (graphesthesia)

Kwang-Ki Kim

Department of Neurology, Kangwon National University Hospital, Chuncheon; Department of Neurology, Seoul National University Hospital*, Seoul; Program of Cognitive Science, Seoul National University†, Seoul, Korea

Abstract

Background: Graphesthesia is the ability to recognize letters or symbols via somatic sensation. We employed functional MRI to determine neurological substrates underlying this ability. We also designed a behavioral experiment to examine the relationship between graphesthesia and working memory.
Methods: Images were acquired in a 1.5T scanner from ten right-handed normal subjects while tactile stimulation was applied for either graphesthesia or simple sensation. Additional eight right-handed normal observers participated in the behavioral experiment where they performed a visuo-spatial or a verbal working memory task, simultaneously with graphesthesia. Overall performance times were measured to detect interference in the dual-task situations.
Results: Comparison between graphesthesia and simple sensory stimulation revealed activations at bilateral prefrontal, parietal and superior temporal cortices, regardless of the hand stimulated. The right parietal operculum was activated for both hand conditions, while the corresponding area in the left hemisphere was activated by right-hand stimulation only, suggesting a right-hemisphere dominance for graphesthesia. From the behavioral experiments, we observed that the visuo-spatial task, but not the verbal task, interfered with graphaesthesia.
Conclusions: Taken together, these results suggest that the brain areas underlying the visuo-spatial sub-system of working memory are involved in graphesthesia and that some cognitive processes underlying graphesthesia are right-lateralized.KeyWords:Graphaesthesia, Functional magnetic resonance imaging, Visuo-spatial working memory