Neural representation of scale illusion: magnetoencephalographic study on the auditory illusion induced by distinctive tone sequences in the two ears

Modifying Deutsch's scale illusion for application in music

Deutsch's scale illusion demonstrates that the overall pitch range is the preferred organization when in competition with both local (note-to-note) pitch proximity and laterality (differences in the input ear). Such intricate factors can make it difficult to mimic this illusion. If a note is under a condition in which grouping by the overall pitch range and the local pitch proximity do not conflict, we hypothesized that an illusion would be perceived simply as the result of the competition between pitch proximity and laterality. In this paper, we aimed to replicate such a condition by modifying Deutsch's scale illusion. Psychophysical studies were conducted with healthy subjects. In the first half of the study, the C major scale with successive tones was presented in ascending form, alternating between the right and left ears; counterpart notes were simultaneously presented to the opposite ear, and the subjects were asked to listen to these dichotic tone patterns. Several counterpart notes were applied; we found that when the sequences of counterpart notes were close in note-to-note pitch proximity and were not overlapped with the ascending scale in pitch, the subjects appeared to perceive the scale clearly. In the latter half of the study, we applied this condition in music and devised auditory illusions such that melodies of the passages of "Lightly Row," "Cherry Blossoms," and "Jingle Bells" were perceived by listening to "jagged" dichotic tone patterns. The method we described in this paper is simple, and it is possible to easily create auditory illusions in music by applying our method.

Intraoperative Meditation Music as an Adjunct to Subarachnoid Block for the Improvement of Postoperative Outcomes Following Cesarean Section: A Randomized Placebo-controlled Comparative Study

Context

Music therapy is a nonpharmacological modality which can provide promising results for postcesarean section recovery.

Aims

The aim of this study was to compare the effects of two types of intraoperative meditation music with control group on postcesarean section pain, anxiety, nausea, vomiting, and psychological maternal wellbeing.

Settings and Design

A prospective, randomized, controlled study was conducted on 189 patients.

Patients and Methods

The inclusion criteria were the American Society of Anaesthesiologists physical status classes 1E and 2E women aged over 18 years posted for emergency cesarean section under spinal anesthesia. The exclusion criteria were patients with hearing/ear abnormalities and psychiatric disorders. Patients were randomly allocated into three groups - soothing meditation music (M) group, binaural beat meditation music (B) group, and control (C) group - where no music was played. After intervention, data were collected and statistically analyzed.

Statistical Analysis Used

Student's t-test was applied for calculation of normative distribution and Mann-Whitney U-test for nonnormative distribution. Nominal categorical data between the groups were compared using Chi-squared test. P <0.05 indicated a statistically significant difference.

Results

Both intraoperative meditation music groups had statistically significant less postoperative pain and anxiety and a better overall psychological wellbeing as compared to the control. There was no statistically significant difference in the occurrence and severity of postoperative nausea and vomiting across all three groups.

Conclusions

Intraoperative meditation music as good adjunct to spinal anesthesia can improve a cesarean section patient's postoperative experience by reducing postoperative pain, anxiety, and psychological wellbeing.

The effect of illusionary perception on mismatch negativity (MMN): An electroencephalography study

Mismatch negativity (MMN) is a unique brain response elicited by any discernible change of features in a tone sequence. Although the occurrence of MMN is dependent upon the difference of a stimulus parameter, such as frequency or intensity, recent studies have suggested that MMN occurs as a result of a comparison between an internal representation created by perception and an incoming tone. The present study aimed to investigate MMN occurs based upon the physical properties of stimuli or as a result of the perception of the scale illusion. A scale illusion occurs during presentation of ascending and descending musical scales between C4 and C5. The tones of these scales are presented to the right and left ear alternately using a dichotic listening paradigm. Although the ascending/descending sequences are alternated between ears after each tone, we perceive the illusion of progressively ascending/descending tones as being separated by ear. The experiment was designed as an oddball task using the illusionary sequence and three different types of tone sequences as control conditions. Brain response to these sequences and infrequently presented deviants was measured using electroencephalography (EEG). All of the control sequences showed MMN in response to the deviant. However, the illusionary sequence did not result in a significant MMN. These results suggest that in the case of scale illusion, the occurrence of MMN is based upon the representation of tones created by perception, but not upon the physical properties of a tone sequence.

Neural correlates of auditory scale illusion

The auditory illusory perception "scale illusion" occurs when ascending and descending musical scale tones are delivered in a dichotic manner, such that the higher or lower tone at each instant is presented alternately to the right and left ears. Resulting tone sequences have a zigzag pitch in one ear and the reversed (zagzig) pitch in the other ear. Most listeners hear illusory smooth pitch sequences of up-down and down-up streams in the two ears separated in higher and lower halves of the scale. Although many behavioral studies have been conducted, how and where in the brain the illusory percept is formed have not been elucidated. In this study, we conducted functional magnetic resonance imaging using sequential tones that induced scale illusion (ILL) and those that mimicked the percept of scale illusion (PCP), and we compared the activation responses evoked by those stimuli by region-of-interest analysis. We examined the effects of adaptation, i.e., the attenuation of response that occurs when close-frequency sounds are repeated, which might interfere with the changes in activation by the illusion process. Results of the activation difference of the two stimuli, measured at varied tempi of tone presentation, in the superior temporal auditory cortex were not explained by adaptation. Instead, excess activation of the ILL stimulus from the PCP stimulus at moderate tempi (83 and 126 bpm) was significant in the posterior auditory cortex with rightward superiority, while significant prefrontal activation was dominant at the highest tempo (245 bpm). We suggest that the area of the planum temporale posterior to the primary auditory cortex is mainly involved in the illusion formation, and that the illusion-related process is strongly dependent on the rate of tone presentation.