Lack of correlation between phonetic magnetic mismatch field and plasma d-serine levels in humans.

OBJECTIVE: Uncovering molecular bases for auditory language processing in the human brain is a fundamental scientific challenge. The power and latency of the magnetic mismatch field (MMF) elicited by phoneme change, which are magnetoencephalographic indices of language function in its early stage of information processing, are theoretically thought to be modulated by N-methyl-d-aspartate-type glutamate receptor (NMDAR) function, but no study has yet assessed this possibility. We have thus sought to demonstrate an association between phonetic MMF power/latency and levels of plasma d-serine, an intrinsic co-agonist of glycine binding sites on NMDAR, in adults. METHODS: The MMF response to phoneme changes was recorded using 204-channel magnetoencephalography in 61 healthy, right-handed, Japanese adults. Plasma levels of d- and l-serine were measured for each participant. RESULTS: We did not find a significant correlation between MMF power/latency and plasma serine levels. CONCLUSIONS: Despite a sufficient sample size, we failed to find an association between the physiological markers of the early stage of information processing of language in the auditory cortex and biomarkers indexing glutamatergic function. SIGNIFICANCE: Our study did not indicate that a molecular index of glutamatergic function could be a surrogate marker for the early stage of information processing of language in humans.

Preattentive dysfunction in bipolar disorder: a MEG study using auditory mismatch negativity.

BACKGROUND: Neuropsychological studies have demonstrated that cognitive dysfunction represents pathophysiological mechanisms underlying bipolar disorder. However, information processing deficits in bipolar disorder have not often been examined electrophysiologically. Here, we examined preattentive processing and sensory information processing using mismatch field (MMNm) and P1m components, respectively, using magnetoencephalography. METHODS: Ten patients with bipolar disorder and 20 healthy volunteers participated in the study. The participants were presented with auditory stimuli sequences comprising standard and deviant stimuli. MMNm was elicited in response to changes in duration and frequency of pure-tone stimuli and a vowel across-category change. RESULTS: The magnetic global field power of MMNm in the right hemisphere under the pure-tone condition was significantly delayed in patients with bipolar disorder compared to healthy volunteers, and that of P1m did not differ between the two groups. The MMNm dipole in the left hemisphere was located inferior in patients with bipolar disorder than in healthy volunteers. This finding did not correlate with clinical symptoms. CONCLUSIONS: Information processing at the preattentive level is impaired in patients with bipolar disorder irrespective of clinical symptoms, and this dysfunction is not due to sensory level dysfunction. The quality of preattentive information processing impairment is different between patients with bipolar disorder and patients with major depressive disorder, as shown by the MMNm latency and power differences.

Preattentive dysfunction in major depression: a magnetoencephalography study using auditory mismatch negativity.

Information processing deficits in major depressive disorder have been infrequently examined electrophysiologically. Its preattentive and sensory information processing was examined using mismatch field (MMNm) and P1m components, respectively, by magnetoencephalography. Fourteen major depressive disorder patients and 19 healthy volunteers participated in the study. MMNm was elicited in response to duration and frequency changes of pure-tone stimuli and in response to a vowel across-category change. The magnetic global field power (mGFP) of MMNm was significantly smaller in the major depressive disorder patients than in the healthy volunteers, although that of P1m did not differ between the two groups. Information processing at the preattentive level is impaired functionally in major depressive disorder, and this dysfunction is not due to the dysfunction at the lower level of information processing.

The influence of gender and personality traits on individual difference in auditory mismatch: a magnetoencephalographic (MMNm) study.

The mismatch negativity (MMN; and its magnetic counterpart, MMNm) is widely used to assess early-stage auditory cortical function in humans and its impairment in various neuropsychiatric disorders. To establish MMN as a useful clinical tool for objective monitoring of auditory cortical function in an individual, we investigated the effect of gender and personality traits on individual difference in MMNm in healthy subjects. Participants were 88 healthy adults (31 women and 57 men). The MMNm in response to the duration or frequency change of tones and those in response to across-phoneme change between vowels /a/ and /o/ were recorded using 204-channel whole-head magnetoencephalography. The temperament and character inventory (TCI) was used to assess individual personality traits. Women were associated with significantly delayed peak latency of phonetic MMNm for the right hemisphere compared with men. Men had greater strength of tonal duration MMNm for the left hemisphere than women. Additionally, the persistence score predicted the strength of phonetic MMNm for the left hemisphere in the combined sample and the tonal duration MMNm for the left hemisphere in men; reward dependence predicted the latency of the tonal duration MMNm for the left hemisphere in men; and cooperativeness predicted the strength of the tonal frequency MMNm for the right hemisphere in women. These results suggest that gender and personality traits have an effect on individual variability of the MMNm. Our observation may provide useful information to establish MMN/MMNm as a clinical tool for monitoring auditory cortical function on an individual basis.

Procedural memory predicts social skills in persons with schizophrenia.

Despite a growing number of studies that have investigated the relationship between neurocognition and psychosocial outcome in schizophrenia, no studies have looked at the relationship between procedural memory and social skills measures in schizophrenia. The goal of this study was to investigate whether procedural memory, often preserved in schizophrenia, could predict nonverbal social skills in chronic patients with schizophrenia. Fourteen outpatients with schizophrenia participated in our study. Procedural memory was evaluated using the Mirror Reading Test, and nonverbal and verbal social skills were evaluated using a structured role play test. As predicted, there was a significant positive correlation between the learning index of the Mirror Reading Test and nonverbal skills (Spearman rho=0.559, p = 0.038), but not for verbal communication skills or processing skills. Although preliminary, these results provide the first evidence of an association between procedural memory and nonverbal social skills in patients with schizophrenia.

Delayed automatic detection of change in speech sounds in adults with autism: a magnetoencephalographic study.

OBJECTIVE: Autism is a form of pervasive developmental disorder in which dysfunction in interpersonal relationships and communication is fundamental. This study evaluated neurophysiological abnormalities at the basic level of language processing, i.e. automatic change detection of speech and non-speech sounds, using magnetoencephalographic recording of mismatch response elicited by change in vowels and tones. METHODS: The auditory magnetic mismatch field (MMF) was evaluated in 9 adults with autism and 19 control subjects using whole-head magnetoencephalography. The MMF in response to the duration change of a pure tone or vowel /a/ and that in response to across-phoneme change between vowels /a/ and /o/, were recorded. RESULTS: The groups were not significantly different in MMF power under any conditions. However, the autism group showed a left-biased latency prolongation of the MMF particularly under the across-phoneme change condition, and this latency delay was significantly associated with greater symptom severity. CONCLUSIONS: These results suggest that adults with autism are associated with delayed processing for automatic change detection of speech sounds. These electrophysiological abnormalities at the earliest level of information processing may contribute to the basis for language deficits observed in autism. SIGNIFICANCE: These results provide the first evidence for delayed latency of phonetic MMF in adults with autism.