Effect of the Temporal Window of Integration of Speech Sound on Mismatch Negativity.

Speech-sound stimuli have a complex structure, and it is unclear how the brain processes them. An event-related potential (ERP), known as mismatch negativity (MMN), is elicited when an individual's brain detects a rare sound. In this study, MMNs were measured in response to an omitted segment of a complex sound consisting of a Japanese vowel. The results indicated that the latency from onset in the right hemisphere was significantly shorter than that in the frontal midline and left hemispheres during left ear stimulation. Additionally, the results of latency from omission showed that the latency of stimuli omitted in the latter part of the temporal window of integration (TWI) was longer than that of stimuli omitted in the first part of the TWI. The mean peak amplitude was found to be higher in the right hemisphere than in the frontal midline and left hemispheres in response to left ear stimulation. In conclusion, the results of this study suggest that would be incorrect to believe that the stimuli have strictly the characteristics of speech-sound. However. the results of the interaction effect in the latencies from omission were insignificant. These results suggest that the detection time for deviance may not be related to the stimulus ear. However, the type of deviant stimuli on latencies was found to be significant. This is because the detection of the deviants was delayed when a deviation occurred in the latter part of the TWI, regardless of the stimulation of the ear.

Electroconvulsive Therapy for Parkinson's Disease with Depression and Neuroleptic Malignant Syndrome: A Case Report.

Parkinson's disease is often complicated by psychiatric symptoms. Psychiatrists are caught in a dilemma between such symptoms and physical treatment since Parkinson's disease sometimes shows treatment resistance based on pharmacological treatment-induced dopamine dysfunction. Here, we report on a 64-year-old woman with a 15-year history of Parkinson's disease with stage IV severity based on the Hoehn and Yahr scale. She was admitted to our hospital with a diagnosis of major depressive disorder with psychotic features. Unfortunately, her treatment course for depression was complicated by neuroleptic malignant syndrome. Because we were concerned about the persistence of her depressive symptoms, the risk of psychotropic drugs causing adverse effects, and progressive disuse syndrome, we administered modified electroconvulsive therapy. Her symptoms of neuroleptic malignant syndrome and depression sufficiently improved after five sessions of modified electroconvulsive therapy. Additionally, the primary motor symptoms of her Parkinson's disease also markedly improved. The improvement of neuroleptic malignant syndrome and her motor symptoms based on dopamine dysfunction can be explained by electroconvulsive therapy's effectiveness in activating dopamine neurotransmission. Besides, the marked improvement of her depressive episode with psychotic features was presumed to involve dopamine receptor activation and regulation. Because advanced Parkinson's disease can sometimes be refractory to treatment based on pharmacological treatment-induced dopamine dysfunction, psychiatrists often have difficulty treating psychiatric symptoms; electroconvulsive therapy may stabilize the dopaminergic system in such cases, presenting a possible non-pharmacologic treatment option for Parkinson's disease.

Estimation of frequency difference at which stream segregation precedes temporal integration as reflected by omission mismatch negativity.

Both stream segregation and temporal integration are considered important for auditory scene analysis in the brain. Several previous studies have indicated that stream segregation may precede temporal integration when both processes are required. In the present study, we utilized mismatch negativity (MMN)-which reflects automatic change detection-to systematically estimate the threshold of the frequency difference at which stream segregation occurs prior to temporal integration when these functions occur together during a state of inattention. Electroencephalography (EEG) data were recorded from 22 healthy Japanese men presented with six blocks of alternating high pure tones (high tones) and low pure tones (low tones). Only high tones were omitted with 5 % probability in all blocks. Our results indicated that stream segregation should cancel temporal integration of close sounds, as indicated by omission-MMN elicitation, when the frequency difference is 1000 Hz or larger.

Temporal integration of deviant sound in automatic detection reflected by mismatch negativity.

Mismatch negativity (MMN) is an event-related potential that is elicited by deviant sounds that are presented along with frequent sounds in the absence of attention. Auditory MMN is generated by the comparison process between sensory memory trace of a frequent auditory event and a deviant event. It is well known that frequent sounds are encoded in memory trace and processed as a single unit within 160-170 ms. This study examined whether deviant sound would be similarly processed as a temporal unit. Twelve healthy men were presented with relatively short standard sounds and relatively long deviant sounds that contained an omitted (i.e. silent) part. Three types of deviant sounds were designed to vary in duration. The MMN amplitude was gradually enhanced from the short to long duration deviant events that contained an omitted part. In contrast, MMN latency showed no significant differences among the deviants. These findings show that deviant sounds are also processed as a unitary event.