PlexinA1 deficiency in BALB/cAJ mice leads to excessive self-grooming and reduced prepulse inhibition

Body Focused Repetitive Behavior Disorders: Behavioral Models and Neurobiological Mechanisms

OBJECTIVE

Body Focused Repetitive Behaviors (BFRB) is an umbrella term for undesirable, repetitive motor activities such as Trichotillomania (TTM), Skin Picking Disorder (SPD), nail biting, cheek chewing, lip biting, finger sucking, finger cracking and teeth grinding. Such behaviors are engaged in to eliminate a part of the body and may result in impaired functionality. The frequency of presentation to clinicians is low since BFRB are defined as harmless, although the number of studies on this condition has increased rapidly recently, including those making a clear determination of epidemiological data, those investigating the etiopathogenesis and those providing treatment guidelines, although they remain inadequate. The present study provides a review of studies investigating the etiology of BFRB to date.

METHOD

Articles published between 1992 and 2021 stored in the Pubmed, Medline, Scopus and Web of Science databases were reviewed, and the prominent research studies of the condition identified were included in the evaluation.

RESULTS

Studies investigating the etiopathogenesis of BFRB were found in most cases to investigate adult populations, and were hampered by such confounding factors as clinical heterogeneity, high rates of comorbid psychiatric diseases and small sample sizes. The identified studies reveal that attempts have been made to explain BFRB based on behavioral models, and that the condition is inherited at a high rate. Treatment planning is mostly associated with monoamine systems (especially glutamate and dopamine) and interventions were directed to addiction elements. Furthermore, cognitive flexibility and motor inhibition defects in neurocognitive area and cortico-striato-thalamocortical cycle abnormalities in neuroimaging studies have been reported.

CONCLUSION

Studies investigating the clinical features, incidence, etiopathogenesis and treatment of BFRB, which holds a controversial place in psychiatric classification systems, would contribute to a better understanding of the disease and a more appropriate definition of the condition.

The Vulnerability of the Developing Brain: Analysis of Highly Expressed Genes in Infant C57BL/6 Mouse Hippocampus in Relation to Phenotypic Annotation Derived From Mutational Studies

The hippocampus has been shown to have a major role in learning and memory, but also to participate in the regulation of emotions. However, its specific role(s) in memory is still unclear. Hippocampal damage or dysfunction mainly results in memory issues, especially in the declarative memory but, in animal studies, has also shown to lead to hyperactivity and difficulty in inhibiting responses previously taught. The brain structure is affected in neuropathological disorders, such as Alzheimer's, epilepsy, and schizophrenia, and also by depression and stress. The hippocampus structure is far from mature at birth and undergoes substantial development throughout infant and juvenile life. The aim of this study was to survey genes highly expressed throughout the postnatal period in mouse hippocampus and which have also been linked to an abnormal phenotype through mutational studies to achieve a greater understanding about hippocampal functions during postnatal development. Publicly available gene expression data from C57BL/6 mouse hippocampus was analyzed; from a total of 5 time points (at postnatal day 1, 10, 15, 21, and 30), 547 genes highly expressed in all of these time points were selected for analysis. Highly expressed genes are considered to be of potential biological importance and appear to be multifunctional, and hence any dysfunction in such a gene will most likely have a large impact on the development of abilities during the postnatal and juvenile period. Phenotypic annotation data downloaded from Mouse Genomic Informatics database were analyzed for these genes, and the results showed that many of them are important for proper embryo development and infant survival, proper growth, and increase in body size, as well as for voluntary movement functions, motor coordination, and balance. The results also indicated an association with seizures that have primarily been characterized by uncontrolled motor activity and the development of proper grooming abilities. The complete list of genes and their phenotypic annotation data have been compiled in a file for easy access.

Interference of commissural connections through the genu of the corpus callosum specifically impairs sensorimotor gating

White matter abnormalities in schizophrenic patients are characterized as regional tract-specific. Myelin loss at the genu of the corpus callosum (GCC) is one of the most consistent findings in schizophrenic patients across the different populations. We characterized the axons that pass through the GCC by stereotactically injecting an anterograde axonal tracing viral vector into the forceps minor of the corpus callosum in one hemisphere, and identified the homotopic brain structures that have commissural connections in the two hemispheres of the prefrontal cortex, including the anterior cingulate area, the prelimbic area, the secondary motor area, and the dorsal part of the agranular insular area, along with commissural connections with the primary motor area, caudoputamen, and claustrum. To investigate whether dysmyelination in these commissural connections is critical for the development of schizophrenia symptoms, we generated a mouse model with focal demyelination at the GCC by stereotactically injecting demyelinating agent lysolecithin into this site, and tested these mice in a battery of behavioral tasks that are used to model the schizophrenia-like symptom domains. We found that demyelination at the GCC influenced neither the social interest or mood state, nor the locomotive activity or motor coordination. Nevertheless, it specifically reduced the prepulse inhibition of acoustic startle that is a well-known measure of sensorimotor gating. This study advances our understanding of the pathophysiological contributions of the GCC-specific white matter lesion to the related disease, and demonstrates an indispensable role of interhemispheric communication between the frontal cortices for the top-down regulation of the sensorimotor gating.