Tsunehiro Takeda

The primary gustatory area in human cerebral cortex studied by magnetoencephalography

Magnetic fields (MFs) from gustatory stimulation with 1 M NaCl and 3 mM saccharin were recorded from the human brain by using a whole-cortex SQUID system. The averaged onset latency of MFs was 93 ms for NaCl and 172 ms for saccharin and no response was obtained for water. A high correlation coefficient was noted between the difference of onset MFs latencies in two tastants and that of behavioral reaction times, and responses to saccharin were delayed or abolished after treatment of a subjects tongue with a sweet-suppressing agent. This finding indicates that the MFs obtained were caused by gustatory stimulation. By plotting the estimated current dipole on the magnetic resonance image, we could locate the primary gustatory area at the transition area between the operculum and insula, as reported in macaque monkeys.

Three-dimensional optometer.

This paper describes the optical and control principles of a newly developed three-dimensional optometer (TDO). The TDO makes it possible to measure simultaneously three basic ocular responses in an actual work situation: accommodation; eye movement; and pupil area. Although the subjects must use a chin rest, they need not fixate their eyes or use any drug for the measurement. Normal lighting is allowed. The TDO can measure accommodation from -12.7 to + 26.6 diopters and 100% of pupil area change when the eye moves within 40 degrees horizontally and 30 degrees vertically. The accuracy of measuring both accommodation and pupil area with the TDO is about the same as that of commerically available apparatus: +/-0.25 diopters and +/-2%, respectively. The error of measuring the angle of the eyes was less than +/-0.5 degrees . Examples of measurements during work with a visual display terminal are presented.

Three-dimensional optometer III

We describe a newly developed three-dimensional optometer III (TDO III) that can measure simultaneously three major ocular functions-accommodation, eye movement, and pupil diameter-and head movement in an actual working environment. The TDO III permits free head movement as well as free eye movement because the measurement component is mounted on the head. Its size has been reduced substantially compared with the original model. The remaining weight of TDO III is counterbalanced to minimize head loading weight. Normal lighting is permitted, and it is unnecessary to dilate the pupil withadrugfor measurement. TDO III can measure accommodation from -12.7 to + 26.6 D and 100% of the pupil diameter change when the eye moves within a 40° horizontal and 30° vertical area. Head movement is permitted within a sphere 200 mm in diameter. The accuracy when measuring both the accommodation and pupil diameter with TDO III is ±0.25 D and ±0.3 mm, respectively. The error when measuring the angles of the eyes is less than ±0.5°. The eye position accuracy is ±10 mm, and the three Cartesian angles are ±1°. The accuracy of TDO III has been intensively investigated in both artificial and human eyes.

Three-dimensional visual stimulator

We describe a newly developed three-dimensional visual stimulator (TVS) that can change independently the directions, distances, sizes, luminance, and varieties of two sets of targets for both eyes. It consists of liquid crystal projectors (LCPs) that generate the flexible images of targets, Badal otometers that change target distances without changing the visual angles, and relay-lens systems that change target directions. A special control program is developed for real-time control of six motors and two LCPs in the TVS together with a three-dimensional optometer III that simultaneously measures eye movement, accommodation, pupil diameter, and head movement. The TVS measurement ranges are as follows: distance, 0 to -20 D; direction, ±16° horizontally and ±15° vertically; size, 0-2° visual angle; and luminance, 10(-2)-10(2) cd/m(2). The target images are refreshed at 60 Hz and speeds with which the target makes a smooth change (ramp stimuli) are as follows: distance, 5 D/s; direction, 30°/s, size, 10°/s. A simple application demonstrates the performance.

Measurement of Gustatory-Evoked Magnetic Fields with Sharp Stimulation

Non-invasive methods to measure brain function, particularly the methods of magnetoencephalography (MEG) and functional magnetic resonance imaging (fMRI), have improved rapidly and remarkably. With these methods, researchers have measured higher cortical functions of the living human brain, especially visual and auditory functions. MEG has the special advantage that it can trace the movement of cortical activity.

The Relation Between Gustatory-Evoked Magnetic Fields and Reaction Times to Different Taste Qualities

Kobayakawa et al. reported the development of a new gustatory stimulation apparatus for which the rise-time was less than 20 ms for a measurement of EEG [1]. They also modified the apparatus for a measurement of MEG, and reported the estimation of the source of the gustatory-evoked magnetic fields (GEMs) in the human cerebral cortex [2] [3]. In the present study we measured the reaction times (RTs) to the different taste qualities and compared them with the GEMs of different taste qualities to find the mutual relation between the reaction times and the onset of GEMs.