Schizotypy and altered hemispheric asymmetries: The role of cilia genes

Altered Use of Context During Visual Perception in Psychotic Psychopathology: A Neurophysiological Investigation of Tuned and Untuned Suppression During Contrast Perception

BACKGROUND AND HYPOTHESIS

The human visual system streamlines visual processing by suppressing responses to textures that are similar to their surrounding context. Surround suppression is weaker in individuals with schizophrenia (ISZ); this altered use of visuospatial context may relate to the characteristic visual distortions they experience.

STUDY DESIGN

To understand atypical surround suppression in psychotic psychopathology, we investigated neurophysiological responses in ISZ, healthy controls (HC), individuals with bipolar disorder (IBP), and first-degree relatives (ISZR/IBPR). Participants performed a contrast judgment task on a circular target with annular surrounds, with concurrent electroencephalography. Orientation-independent (untuned) suppression was estimated from responses to central targets with orthogonal surrounds; the orientation-dependence of suppression was estimated by fitting an exponential function to the increase in suppression as surrounds became more aligned with the center.

RESULTS

ISZ exhibited weakened untuned suppression coupled with enhanced orientation-dependence of suppression. The N1 visual evoked potential was associated with the orientation-dependence of suppression, with ISZ and ISZR (but not IBP or IBPR) showing enhanced orientation-dependence of the N1. Collapsed across orientation conditions, the N1 for ISZ lacked asymmetry toward the right hemisphere; this reduction in N1 asymmetry was associated with reduced untuned suppression, real-world perceptual anomalies, and psychotic psychopathology. The overall amplitude of the N1 was reduced in ISZ and IBP.

CONCLUSIONS

Key measures of symptomatology for ISZ are associated with reductions in untuned suppression. Increased sensitivity for ISZ to the relative orientation of suppressive surrounds is reflected in the N1 VEP, which is commonly associated with higher-level visual functions such as allocation of spatial attention or scene segmentation.

Neuroanatomical correlates of musicianship in left-handers

BACKGROUND

Left-handedness is a condition that reverses the typical left cerebral dominance of motor control to an atypical right dominance. The impact of this distinct control - and its associated neuroanatomical peculiarities - on other cognitive functions such as music processing or playing a musical instrument remains unexplored. Previous studies in right-handed population have linked musicianship to a larger volume in the (right) auditory cortex and a larger volume in the (right) arcuate fasciculus.

RESULTS

In our study, we reveal that left-handed musicians (n = 55), in comparison to left-handed non-musicians (n = 75), exhibit a larger gray matter volume in both the left and right Heschl's gyrus, critical for auditory processing. They also present a higher number of streamlines across the anterior segment of the right arcuate fasciculus. Importantly, atypical hemispheric lateralization of speech (notably prevalent among left-handers) was associated to a rightward asymmetry of the AF, in contrast to the leftward asymmetry exhibited by the typically lateralized.

CONCLUSIONS

These findings suggest that left-handed musicians share similar neuroanatomical characteristics with their right-handed counterparts. However, atypical lateralization of speech might potentiate the right audiomotor pathway, which has been associated with musicianship and better musical skills. This may help explain why musicians are more prevalent among left-handers and shed light on their cognitive advantages.

Abelson Helper Integration Site 1 haplotypes and peripheral blood expression associates with lithium response and immunomodulation in bipolar patients

RATIONALE

In bipolar disorder (BD), immunological factors play a role in the pathogenesis and treatment of the illness. Studies showed the potential link between Abelson Helper Integration Site 1 (AHI1) protein, behavioural changes and innate immunity regulation. An immunomodulatory effect was suggested for lithium, a mood stabilizer used in BD treatment.

OBJECTIVES

We hypothesized that AHI1 may be an important mediator of lithium treatment response. Our study aimed to investigate whether the AHI1 haplotypes and expression associates with lithium treatment response in BD patients. We also examined whether AHI1 expression and lithium treatment correlate with innate inflammatory response genes.

RESULTS

We genotyped seven AHI1 single nucleotide polymorphisms in 97 euthymic BD patients and found that TG haplotype (rs7739635, rs9494332) was significantly associated with lithium response. We also showed significantly increased AHI1 expression in the blood of lithium responders compared to non-responders and BD patients compared to healthy controls (HC). We analyzed the expression of genes involved in the innate immune response and inflammatory response regulation (TLR4, CASP4, CASP5, NLRP3, IL1A, IL1B, IL6, IL10, IL18) in 21 lithium-treated BD patients, 20 BD patients treated with other mood stabilizer and 19 HC. We found significantly altered expression between BD patients and HC, but not between BD patients treated with different mood stabilizers.

CONCLUSIONS

Our study suggests the involvement of AHI1 in the lithium mode of action. Moreover, mood-stabilizing treatment associated with the innate immunity-related gene expression in BD patients and only the lithium-treated BD patients showed significantly elevated expression of anti-inflammatory IL10, suggesting lithium's immunomodulatory potential.

It Is Not Just in the Genes

Asymmetries in the functional and structural organization of the nervous system are widespread in the animal kingdom and especially characterize the human brain. Although there is little doubt that asymmetries arise through genetic and nongenetic factors, an overarching model to explain the development of functional lateralization patterns is still lacking. Current genetic psychology collects data on genes relevant to brain lateralizations, while animal research provides information on the cellular mechanisms mediating the effects of not only genetic but also environmental factors. This review combines data from human and animal research (especially on birds) and outlines a multi-level model for asymmetry formation. The relative impact of genetic and nongenetic factors varies between different developmental phases and neuronal structures. The basic lateralized organization of a brain is already established through genetically controlled embryonic events. During ongoing development, hemispheric specialization increases for specific functions and subsystems interact to shape the final functional organization of a brain. In particular, these developmental steps are influenced by environmental experiences, which regulate the fine-tuning of neural networks via processes that are referred to as ontogenetic plasticity. The plastic potential of the nervous system could be decisive for the evolutionary success of lateralized brains.

MORC1 methylation and BDI are associated with microstructural features of the hippocampus and medial prefrontal cortex

BACKGROUND

Alterations in the hippocampus and prefrontal cortex (PFC) have frequently been reported in depressed patients. These parameters might prove to be a consistent finding in depression. In addition, peripheral DNA methylation of the MORC1 gene promoter showed stable associations with depression across independent samples. However, the question arises whether MORC1, supposedly acting as transcription factor, might also be involved in neurobiological alterations accompanying depression. This study further analyses the role of MORC1 in depression by investigating a potential correlation between peripheral MORC1 DNA methylation and neuronal structural properties previously associated with depression in humans.

METHODS

Beck Depression Inventory (BDI) was assessed in 52 healthy participants. DNA was extracted from buccal cells and MORC1 methylation correlated with micro- and macrostructural properties derived from magnetic resonance imaging (MRI) and neurite orientation dispersion and density imaging (NODDI) in the hippocampus and medial prefrontal cortex (mPFC).

RESULTS

MORC1 methylation was associated with volume reduction and neurite orientation dispersion and density markers in the hippocampus and mPFC. BDI was positively associated with neurite orientation dispersion and density markers in the hippocampus.

LIMITATIONS

The study was conducted in a small sample of healthy participants with subclinical depressive symptoms. Peripheral tissue was analyzed.

CONCLUSION

We found significant negative associations between peripheral MORC1 methylation and macro- and microstructural markers in the hippocampus and mPFC. Thus, MORC1 might be involved in neurobiological properties. Studies investigating neuronal methylation patterns of MORC1 are needed to support this hypothesis.

Semantic priming and schizotypal personality: reassessing the link between thought disorder and enhanced spreading of semantic activation

The term schizotypy refers to a group of stable personality traits with attributes similar to symptoms of schizophrenia, usually classified in terms of positive, negative or cognitive disorganization symptoms. The observation of increased spreading of semantic activation in individuals with schizotypal traits has led to the hypothesis that thought disorder, one of the characteristics of cognitive disorganization, stems from semantic disturbances. Nevertheless, it is still not clear under which specific circumstances (i.e., automatic or controlled processing, direct or indirect semantic relation) schizotypy affects semantic priming or whether it does affect it at all. We conducted two semantic priming studies with volunteers varying in schizotypy, one with directly related prime-target pairs and another with indirectly related pairs. Our participants completed a lexical decision task with related and unrelated pairs presented at short (250 ms) and long (750 ms) stimulus onset asynchronies (SOAs). Then, they responded to the brief versions of the Schizotypal Personality Questionnaire and the Oxford-Liverpool Inventory of Feelings and Experiences, both of which include measures of cognitive disorganization. Bayesian mixed-effects models indicated expected effects of SOA and semantic relatedness, as well as an interaction between relatedness and directness (greater priming effects for directly related pairs). Even though our analyses demonstrated good sensitivity, we observed no influence of cognitive disorganization over semantic priming. Our study provides no compelling evidence that schizotypal symptoms, specifically those associated with the cognitive disorganization dimension, are rooted in an increased spreading of semantic activation in priming tasks.