Wallenberg's syndrome following neck manipulation.

We describe 4 patients ages 28 to 41 with lateral medullary infarction (Wallenberg's syndrome) following chiropractic neck manipulation. In 3 patients, angiography documented dissection of the extracranial 3rd segment of the vertebral artery near the atlantoaxial joint. The onset of neurologic symptoms following manipulation varied from immediate to 4 days. All had good recovery with minor residual deficits. Although the association between chiropractic neck manipulation and vertebral-basilar artery distribution infarction is well known, we emphasize its occurrence in young healthy individuals without commonly regarded predisposing factors.

Effects of meditation on brainstem auditory evoked potentials.

Brainstem auditory evoked potentials (BAEPs) were measured in five advanced practitioners of Transcendental Meditation (TM) to determine whether such responses would reflect reported increases in perceptual acuity to auditory stimuli following meditation. The BAEP provides an objective physiological index of auditory function at a subcortical level. Repeated measures of the BAEPs of TM practitioners were taken before and after a period of meditation and were compared with those of age-matched controls. Peak latencies as well as interwave latencies between major BAEP components were evaluated. No pre-postmeditation differences for experimental subjects were observed at low stimulus intensities (0--35 dB). At moderate intensities (40--50 dB), latency of the inferior collicular wave (wave V) increased following meditation, but at higher stimulus intensities (55--70 dB), latency of this wave was slightly decreased. Comparison of slopes and intercepts of stimulus intensity-latency functions indicates a possible effect of meditation on brainstem activity.

The effect of transcendental meditation on iconic memory.

Three experiments investigated the effects of transcendental meditation (TM) on iconic memory. The task involved reporting of digits shown tachistoscopically, using Sperling's partial-report technique. Experiment 1 was a pilot study involving a meditation group and a nonmeditation gropu. All subjects were run in a pretest/treatment/posttest design. During the treatment phase the meditation group practiced TM for a 20-minute period and the nonmeditation group relaxed with eyes closed. The results showed that the treatment increased performance in meditators, but not in nonmeditators. In this experiment important controls such as individual administration of the task, extrinsic rewards, subject pacing, and adequate practice were lacking. Experiment 2 was a replication of the first, with these controls added. The results no longer showed a superiority for the meditation treatment. In fact, the meditation group performed worse on each day of running. Experiment 3 was a replication of Experiment 1, to assess whether the meditation effect of Experiment 1 was due to (a) differential increased attention of the meditators (minimized in subject-paced Experiment 2), (b) a gain early in learning for the meditators that was eliminated due to practice in Experiment 2, or (c) a lack of proper control procedures in Experiment 1. The performance of the meditators was, again, significantly lower. This research illustrates the importance of careful control when investigating the effects of meditation on behavior. It also suggests that the effects of meditation may depend on which hemisphere is dominant in performing the task.

Changes in cerebral hemispheric lateralization with hypnosis.

Cerebral hemisphere dominance was measured in 20 subjects before, during, and after hypnotic suggestion. During hypnosis, subjects demonstrated lower right ear/left hemisphere laterality scores on a dichotic listening task compared to pre- and posthypnosis periods. These results support the view that hypnosis facilitates greater participation of the right cerebral hemisphere in cognition and may partially account for several well known hypnotic effects.

The effect of transcendental meditation on right hemispheric functioning.

This study reports two experiments investigating the effects of transcendental meditation on right hemispheric functioning. The task used in both experiments was the Seashore Tonal Memory Test. In the first experiment a non-meditator group and an experienced meditator group were run. The design involved three periods: a pretest, a meditation or rest period, and then a posttest. The results showed the experienced meditators were significantly better in both pretest and posttest performance. There were no pretest-posttest differences. The second experiment was done to replicate the first experiment and to control for possible selection bias. The design was the same as the first experiment, except that an additional group of inexperienced meditators was included. The results again showed significantly superior performance for the experienced meditators compared to the non-meditators. In addition, the experienced meditators were superior to the inexperienced meditators. There were no significant differences between the non-meditators and the inexperienced meditators. These results support the hypothesis that meditation facilitates right hemispheric functioning. Alternative explanations, such as selection bias, are also discussed.