Pavan Mallikarjun

Folding of the Prefrontal Cortex in Schizophrenia: Regional Differences in Gyrification

BACKGROUND Anatomy of prefrontal cortex in schizophrenia has been studied previously by quantifying the degree of gyrification. Conflicting results exist, with some studies showing hypergyria and others showing hypogyria. It is likely that regional variations in cortical folding exist within the prefrontal cortex that could be explored by studying the anatomical subdivisions formed by the sulci and gyri. With surface reconstructions from magnetic resonance imaging, we studied the gyrification within anatomically meaningful subdivisions of prefrontal cortex in schizophrenia. METHODS Prefrontal cortex was studied with an automated method to obtain Local Gyrification Index, reflecting the degree of cortical folding in 57 patients with schizophrenia and 42 control subjects. Regional differences within prefrontal cortex were compared between the two groups with a sulcogyral atlas. Effects of hemisphere and age were subsequently assessed. RESULTS Patients with schizophrenia had significant hypogyria in most prefrontal regions except the frontomarginal region, which showed hypergyria. The normal left > right pattern of prefrontal gyrification was reversed in schizophrenia. Patients with schizophrenia also showed significant age-related reduction in gyrification at the hypogyric regions. CONCLUSIONS The differences between reported findings regarding prefrontal gyrification might reflect regional variation in the nature of the abnormal process of gyrification in schizophrenia. Prefrontal gyrification is significantly influenced by age in schizophrenia, in addition to the influence of neurodevelopmental factors.

Reality distortion is related to the structure of the salience network in schizophrenia

BACKGROUND An intrinsic cerebral network comprising the anterior cingulate and anterior insula (the salience network) is considered to play an important role in salience detection in healthy volunteers. Aberrant salience has been proposed as an important mechanism in the production of psychotic symptoms such as delusions and hallucinations (reality distortion). We investigated whether structural deficits in the salience network are associated with the reality distortion seen in schizophrenia. METHOD A sample of 57 patients in a clinically stable state of schizophrenia and 41 controls were studied with high-resolution magnetic resonance imaging. RESULTS Bilateral volume reduction was seen in the anterior cingulate and anterior insula in patients with schizophrenia. Reduced volume in the two left-sided regions of the salience network was significantly correlated with the severity of reality distortion. CONCLUSIONS These findings suggest that a deficit of grey matter in the salience network leads to an impaired attribution of salience to stimuli that is associated with delusions and hallucinations in schizophrenia.

Prevention of postnatal depression

Postnatal depression is the most frequent psychiatric disorder seen after childbirth, with a prevalence rate of 10% to 15%. The women at risk need to be identified by a valid and reliable method, either using a screening instrument or an interview schedule. The preventive strategies need to have enough power to detect a clinically worthwhile effect to be considered useful in clinical practice. Many of the risk factors for developing postnatal depression are present during the pregnancy and immediate post-partum period. The risk factors for postnatal depression include depression or anxiety during pregnancy, experiencing stressful life events during pregnancy or the early puerperium, maternity blues, low levels of social support, past history of depression and poor marital adjustment. The antenatal and postnatal period provides an ideal opportunity to screen women for these risk factors. The women identified to be at risk can be identified, and preventive interventions can be implemented. Routine clinical practice can be improved to identify some of the women at risk by better communication between health professionals. There are no antenatal screening tools that have been shown to be of benefit in predicting postnatal depression. Edinburgh Postnatal Depression Scale is widely used in the postnatal period to screen for depression. The psychosocial interventions to prevent postnatal depression have not been shown to be beneficial and there is a dearth of psychopharmacological trials to make firm conclusions about their efficacy in preventing postnatal depression. Individualised psychosocial interventions aimed at the at-risk populations and initiated in the postnatal period appear to have some benefit in preventing postnatal depression. The focus of this article will be the risk factors associated with postnatal depression, screening methods and tools to identify those at risk of developing the disorder and the psychosocial, psychological and psychopharmacological interventions to prevent postnatal depression.

Regional contraction of brain surface area involves three large-scale networks in schizophrenia

In schizophrenia, morphological changes in the cerebral cortex have been primarily investigated using volumetric or cortical thickness measurements. In healthy subjects, as the brain size increases, the surface area expands disproportionately when compared to the scaling of cortical thickness. In this structural MRI study, we investigated the changes in brain surface area in schizophrenia by constructing relative areal contraction/expansion maps showing group differences in surface area using Freesurfer software in 57 patients and 41 controls. We observed relative areal contraction affecting Default Mode Network, Central Executive Network and Salience Network, in addition to other regions in schizophrenia. We confirmed the surface area reduction across these three large-scale brain networks by undertaking further region-of-interest analysis of surface area. We also observed a significant hemispheric asymmetry in the surface area changes, with the left hemisphere showing a greater reduction in the areal contraction maps. Our findings suggest that a fundamental disturbance in cortical expansion is likely in individuals who develop schizophrenia.

Appreciating symptoms and deficits in schizophrenia: right posterior insula and poor insight.

Poor insight is one of the most prominent clinical features of psychosis. Loss of insight in schizophrenia is characterised by abnormalities in awareness and attribution of the origin of pathological mental phenomena. Converging lines of investigations suggest that in healthy individuals, right posterior insula plays an important role in awareness and self-attribution of mental phenomena, contributing to the emergence of a sense of self (Craig, 2002; Farrer et al., 2003). In addition, neuroimaging studies investigating brain morphometry in schizophrenia have consistently reported deficits in the structure of insula (Glahn et al., 2008; Ellison-Wright and Bullmore, 2010). In the present study, we investigated the relationship between the morphometry of posterior insula and degree of insight in a sample of 57 patients in a stable phase of illness using high resolution Magnetic Resonance Imaging. We measured the cortical surface area and local white matter volume of posterior insula. A significant inverse relationship was found between right posterior insular structure and degree of insight in schizophrenia. No such relationship was noted for left posterior insula. Our results highlight the importance of a predominantly right-sided network that includes posterior insula as the neural basis of insight. Abnormalities in interoceptive awareness and self-appraisal of emotional states may contribute to the loss of insight seen in schizophrenia.

How much does phase resetting contribute to event-related EEG abnormalities in schizophrenia?

OBJECTIVE Patients suffering from schizophrenia demonstrate impaired low frequency electrophysiological responses to stimuli, but it remains unclear whether these abnormalities arise from phase resetting of ongoing oscillations, new phase-locked (evoked) activity or non-phase-locked (induced) activity. Our goal is to clarify the contribution of each of these three processes to the impairment of neural activity during information processing in schizophrenia, by using statistics that do not confound increases in the mean post-stimulus signal with phase resetting. METHODS Thirty-four male schizophrenia patients and 34 healthy matched controls performed an auditory oddball task. We applied the analysis procedure developed by Martinez-Montes et al. based on complex-valued wavelet transform to event-related signal elicited by target stimuli. RESULTS The largest abnormalities were found for phase-locked delta (1-4 Hz) and non-phase-locked theta (4-8 Hz). Delta phase resetting was moderately impaired and related to symptoms of disorganization. It also predicted evoked theta signal. CONCLUSION The substantial reduction of both evoked and induced oscillatory activity in schizophrenia indicates diminished recruitment of brain circuits engaged not only in stimulus-locked perceptual processing but also in more extensive processing less tightly time locked to the stimulus. Although reduced phase resetting makes a lesser contribution, it indicates a deficit in the ability to harness ongoing electrical activity.