Abstract
The importance of somatosensory information arising from intraoral mechanoreceptors in intraoral sensory discrimination (e.g. detecting position, consistency, size and shape of an object in the oral cavity) should be stressed, since sensory discrimination in the oral cavity are performed without visual information by nature. Nonetheless, there is little information about how the somatosensory information is processed within the cerebral cortex during intraoral sensory discrimination tasks. For this, many studies showed that visual cortical areas are active during tactile discrimination such as Braille reading and blind discrimination of Mah-Jong tiles both in blind and normally sighted humans. The present study was conducted to investigate if visual cortical areas as well as prefrontal area are activated during intraoral form discrimination task by assessing total ([total-Hb]), oxygenated ([oxy-Hb]) and deoxygenated ([deoxy-Hb]) hemoglobin concentration changes using 44 channel near-infrared spectroscopy (NIRS) in normally sighted humans. Among 12 subjects tested (23-62 years old), increase in [total-Hb] and [oxy-Hb] was observed in visual cortical area in all subjects during the task. Also, such task-related increase in [total-Hb] and [oxy-Hb] in prefrontal area was observed in 8 subjects. The findings suggest that visual cortical areas play important roles in intraoral somatosensory discrimination and somatosensory processing patterns within the cerebral cortex may be variable among individuals. [J Physiol Sci. 2008;58 Suppl:S145]
