Neurological soft signs in Chinese adolescents with antisocial personality traits
Introduction
Neurologic soft signs (NSSs) were usually subtle but observable impairments in motor and sensory functions. They were neither localized to a specific region of the brain nor characteristic of any specific neurological condition (Bombin et al., 2005). However, recent studies using brain imaging technologies demonstrated that NSSs may be associated with specific brain regions or even brain connections. For instance, research indicated that higher rates of soft neurologic signs were associated with a reduction of gray matter volume of subcortical structures, including putamen, globus pallidus, and thalamus, in both patients with first-onset schizophrenia and healthy volunteers (Dazzan et al., 2006, Dazzan et al., 2004). Further, another study found that fist–edge–palm task, one of the NSSs, induced significant activations within the cortical networks that contain bilateral sensorimotor, supplementary motor area, left parietal, and the right cerebellum in healthy subjects (Chan et al., 2006, Rao et al., 2008).
Antisocial Personality Disorder (ASPD) develops mostly during childhood or early adolescence and persists into adulthood. It is characterized by dysfunctional interpersonal relationships, a lack of empathy and remorse, impulsivity, and aggression (Glenn et al., 2013). Several studies investigated the biological mechanisms underlying these behaviors. Neuroimaging studies found structural and functional abnormalities of people with ASPD. For example, Rankin et al. revealed that the medial orbitofrontal cortex (OFC) and ventral striatal structures contributed to empathy, and the right anterior temporal areas were essential for real-life empathic behavior (Rankin et al., 2006). Meantime, some research demonstrated the relationship between brain structure and impulsive aggressive behavior. Researchers found that aggressive impulsive behavior was associated with reduced metabolism in the orbitofrontal, anterior medial frontal, and left anterior frontal regions (Goyer et al., 1994). Hoptman et al. found that the inferior frontal white matter microstructure (Hoptman et al., 2002) and amygdalofrontal functional disconnectivity (Hoptman et al., 2010) was associated with aggressive and antisocial behavior. Further, reduced metabolism was found in the superior parietal cortex in aggressive patients (Hirono et al., 2000), and individuals with impulsive personality disorders (Siever et al., 1999).
There are some previous studies correlating NSSs and ASPDs or antisocial behavior. A study recruited inpatients with schizophrenia with violent behavior, and patients were classified into high (n=28), low (n=27), or no (n=34) violence groups. This study found that the high violence group showed more neurologic and neuropsychologic abnormalities than the other two groups in the area of integrative sensory and motor functions (Krakowski et al., 1989). Another study comprised 14 homicidal men with ASPD according to a forensic psychiatric examination. Ten healthy volunteers served as controls. The NSSs scores of antisocial offenders were dramatically increased as compared with normal controls (Lindberg et al., 2004). These aforementioned researches may indicate that antisocial behavior or ASPD was related to a certain neurophysiology deficit.
The Cambridge Neurological Inventory was a clinical instrument for assessment of soft neurologic signs, and it consisted of three subscales: the motor coordination, sensory integration, and disinhibition. These subscales have been devised to investigate the putative areas of the prefrontal, parietal, and frontal lobes, respectively (Chen et al., 1995, Chan and Gottesman, 2008). Given the aforementioned researches, the purpose of this study was to investigate the specific relationship between NSSs and characteristics of antisocial personality traits in adolescents, and to explore the particular NSSs linked to certain brain regions in adolescents with antisocial personality traits. In addition, considering adolescence was a vulnerable period and facilitates the start of risk behaviors (Garcia and Costa, 2008), such as cannabis abuse (Dervaux et al., 2010), smoking, unprotected sex, and so on, and higher levels of psychopathic traits in adolescence predicted violent recidivism (Gretton et al., 2004), we chose teenagers as our experimental subjects.
Section snippets
Participants
The adolescents were recruited from five cities in China (Beijing, Changsha, Suzhou, Chengdu, and Yinchuan). Adolescents or their family members with a history of psychotic illness were excluded on the basis of a brief questionnaire. Eventually, 2861 effective questionnaires were collected, comprising 1395 boys and 1466 girls. Permission was taken from the Medical Ethics Committee of Central South University, and written informed consent was obtained from all participants.
Personality Diagnostic Questionnaire-4+, PDQ-4+
Antisocial personality
Demographics
Ninety-six adolescents with only antisocial personality traits were detected according to the cut-off score of antisocial personality disorder subscale of PDQ-4+. Further, 96 healthy controls were recruited by random selection from the enrolled teenagers without any pathological personality traits we detected, and they were matched for age and gender. Meantime, none of the subjects reported cannabis or other drug abuse. As demonstrated in Table 1, there were no significant between-group
Discussion
The results revealed that adolescents with antisocial personality traits exhibited a higher prevalence of NSSs than normal control participants. The ASP group showed greater motor coordination, sensory integration, disinhibition, and total NSSs than the normal group. Our study suggested that neural abnormality was involved in development of ASPD. The present findings were also similar to those from previous studies focused on antisocial personality or antisocial behavior (Krakowski et al., 1989
Conflict of interest
None of the authors reports conflicts of interest.
Acknowledgments
This study was supported by grants from the National Key Technologies R&D Program in the 11th 5-year plan of China (Grant No. 2009BAI77B02); the National Natural Science Foundation of China (Grant No. 81401128).
References (29)
- et al.
Neurological soft signs as candidate endophenotypes for schizophrenia: a shooting star or a Northern star?
Neurosci. Biobehav. Rev.
(2008) - et al.
The neural basis of motor sequencing: an fMRI study of healthy subjects
Neurosci. Lett.
(2006) - et al.
The Cambridge Neurological Inventory: a clinical instrument for assessment of soft neurological signs in psychiatric patients
Psychiatry Res.
(1995) - et al.
Impulsivity and sensation seeking in cannabis abusing patients with schizophrenia
Schizophr. Res.
(2010) - et al.
The neuropsychology of antisocial personality disorder
Dis. Mon.
(2007) - et al.
Frontal white matter microstructure, aggression, and impulsivity in men with schizophrenia: a preliminary study
Biol. Psychiatry
(2002) - et al.
Neurological soft signs in homicidal men with antisocial personality disorder
Eur. Psychiatry
(2004) - et al.
Deficits in facial affect recognition among antisocial populations: a meta-analysis
Neurosci. Biobehav. Rev.
(2008) - et al.
A regulation role of the prefrontal cortex in the fist-edge-palm task: evidence from functional connectivity analysis
NeuroImage
(2008) - et al.
d, l-fenfluramine response in impulsive personality disorder assessed with [18F] fluorodeoxyglucose positron emission tomography
Neuropsychopharmacology
(1999)