Accumulating evidence has suggested neurological soft signs (NSS) are promising endophenotypes for psychosis spectrum, and particularly for schizophrenia spectrum disorders.  

Although empirical findings from neuroimaging studies have suggested the specific network responsible for these signs, most of these findings were limited to motor coordination and disinhibition signs of NSS. Very little is known for the neural mechanism for sensory integration signs of NSS.  

Dr. Raymond Chan's team from the Neuropsychology and Applied Cognitive Neuroscience (NACN) Laboratory, the CAS Key Laboratory of Mental Health, Institute of Psychology has estimated the heritability and familiality of NSS in the Han Chinese population. However, these estimates were limited to behavioural level, it is still not known whether similar heritability estimates can be shown at a neural level.  

In the most recent study done by Dr. Chan's team and his international collaborators, they adopted functional imaging paradigms to 56 pairs of healthy twins (28 pairs of monozygotic and 28 pairs of dizygotic) in order to examine the heritability of complex motor sequencing and sensory integration signs.  

They administered the Fist-Edge-Pam (FEP) and Audio-Visual Integration (AVI) functional imaging tasks to all the participants. 

Due to the head motions during fMRI scanning, three pairs of twins were excluded resulting in 26 pairs of monozygotic twins and 27 pairs of dizygotic twins for the subsequent analysis.  

The structure equation modeling tool OpenMx was used to calculate the heritability of the FEP and AVI tasks performances.  

The findings showed that activation of the pre- and postcentral, temporal and parietal gyri, the supplementary motor area and the cerebellum were observed during the FEP task performance, whereas activation of the precentral, temporal and fusiform gyri, the thalamus and the caudate were observed during the AVI task performance.  

Structural equation modeling showed that significant heritability estimates were exhibited in the supplementary motor area for the FEP task, and in the precentral gyrus and the thalamic nuclei for the AVI task. The estimates ranged from 0.5 to 0.62.  

Considerable heritability of activation at the supplementary motor area, the precentral gyrus and the various nuclei of the thalamus supports the notion that complex motor sequencing and sensory integration are heritable from a brain-activation perspective.  

Moreover, the brain networks captured by the FEP and AVI tasks appear to be parts of the cortico-subcortical-cerebellar circuitry that underlies the abnormalities of schizophrenia spectrum disorders.  

These findings may provide important guidance for precision psychiatry and precision brain science. 

The paper is now available online in Human Brain Mapping entitled "Neural mechanism and heritability of complex motor sequence and audiovisual integration: A healthy twin study".

This study was supported by grants from Beijing Municipal Science & Technology Commission Grant, the National Key Research and Development Programme, the Beijing Training Project for the Leading Talents in Science and Technology, the "Strategic Priority Research Program (B)" of the Chinese Academy of Sciences, the National Science Fund China, and a grant from the CAS Key Laboratory of Mental Health, Institute of Psychology. 

healthy twins (Image by Raymond Chan)