Genetic influences on prefrontal activation during a verbal fluency task in adults: a twin study based on multichannel near-infrared spectroscopy.

Near-infrared spectroscopy (NIRS) studies have reported that prefrontal hemodynamic dysfunction during executive function tasks may be a promising biomarker of psychiatric disorders, because its portability and noninvasiveness allow easy measurements in clinical settings. Here, we investigated the degree to which prefrontal NIRS signals are genetically determined. Using a 52-channel NIRS system, we monitored the oxy-hemoglobin (oxy-Hb) signal changes in 38 adult pairs of right-handed monozygotic (MZ) twins and 13 pairs of same-sex right-handed dizygotic (DZ) twins during a letter version of the verbal fluency task. Heritability was estimated based on a classical twin paradigm using structured equation modeling. Significant genetic influences were estimated in the right dorsolateral prefrontal cortex and left frontal pole. The degrees of heritability were 66% and 75% in the variances, respectively. This implies that the prefrontal hemodynamic dysfunction observed during an executive function task measured by NIRS may be an efficient endophenotype for large-scale imaging genetic studies in psychiatric disorders.

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.

Prefrontal activation during inhibitory control measured by near-infrared spectroscopy for differentiating between autism spectrum disorders and attention deficit hyperactivity disorder in adults.

The differential diagnosis of autism spectrum disorders (ASDs) and attention deficit hyperactivity disorder (ADHD) based solely on symptomatic and behavioral assessments can be difficult, even for experts. Thus, the development of a neuroimaging marker that differentiates ASDs from ADHD would be an important contribution to this field. We assessed the differences in prefrontal activation between adults with ASDs and ADHD using an entirely non-invasive and portable neuroimaging tool, near-infrared spectroscopy. This study included 21 drug-naïve adults with ASDs, 19 drug-naïve adults with ADHD, and 21 healthy subjects matched for age, sex, and IQ. Oxygenated hemoglobin concentration changes in the prefrontal cortex were assessed during a stop signal task and a verbal fluency task. During the stop signal task, compared to the control group, the ASDs group exhibited lower activation in a broad prefrontal area, whereas the ADHD group showed underactivation of the right premotor area, right presupplementary motor area, and bilateral dorsolateral prefrontal cortices. Significant differences were observed in the left ventrolateral prefrontal cortex between the ASDs and ADHD groups during the stop signal task. The leave-one-out cross-validation method using mean oxygenated hemoglobin changes yielded a classification accuracy of 81.4% during inhibitory control. These results were task specific, as the brain activation pattern observed during the verbal fluency task did not differentiate the ASDs and ADHD groups significantly. This study therefore provides evidence of a difference in left ventrolateral prefrontal activation during inhibitory control between adults with ASDs and ADHD. Thus, near-infrared spectroscopy may be useful as an auxiliary tool for the differential diagnosis of such developmental disorders.