Exploration of the cortical pathophysiology underlying visual disturbances in schizophrenia comorbid with depressive disorder-An evidence from mouse model

Biological Methods for Diagnosing Depressive Symptoms in Patients with Schizophrenia: A Narrative Review

BACKGROUND

Depressive symptoms in patients with schizophrenia lead to more frequent exacerbations of the underlying disease, worsen the prognosis, and increase the risk of suicide. Clinical practitioners continue to face challenges in diagnosing this disorder.

AIM

This study aims to analyze published material on biological markers of depressive symptoms in patients with schizophrenia.

METHODS

The search of literature was conducted using the following electronic search engines (the total number of relevant papers found is also specified): ACCESSSS (n=150), Cochrane Library (n=48), PubMed (n=623), eLIBRARY (n=216), and Google Scholar (n=367). The final discussion included 67 papers consistent with the study aim and were published between January 1, 2018 and December 31, 2023.

RESULTS

Based on the available scaterred data, it appears that plasma biomarkers (e.g. C-reactive protein, metabolic parameters, hormones, enzymes, neurotrophic factors) are limited in specificity when it comes to diagnosing depressive symptoms in schizophrenia. Our analysis of the neuroimaging findings showed that depressive manifestations are associated with a decrease in the volume of the gray matter in the parietal, frontal, and temporal lobes (particularly in Broca's and Wernicke's areas) and in specific regions of the prefrontal cortex (including the medial right superior frontal, medial orbitofrontal, and superior and middle frontal gyri). It has been suggested that the SIRT1, OXT, CDKAL1, and APOE genes are involved in the development of depressive symptoms in patients with schizophrenia.

CONCLUSION

Understanding and identifying depressive symptoms in schizophrenia will improve the quality of care for patients with this disorder.

Optogenetic Methods to Investigate Brain Alterations in Preclinical Models

Investigating the neuronal dynamics supporting brain functions and understanding how the alterations in these mechanisms result in pathological conditions represents a fundamental challenge. Preclinical research on model organisms allows for a multiscale and multiparametric analysis in vivo of the neuronal mechanisms and holds the potential for better linking the symptoms of a neurological disorder to the underlying cellular and circuit alterations, eventually leading to the identification of therapeutic/rescue strategies. In recent years, brain research in model organisms has taken advantage, along with other techniques, of the development and continuous refinement of methods that use light and optical approaches to reconstruct the activity of brain circuits at the cellular and system levels, and to probe the impact of the different neuronal components in the observed dynamics. These tools, combining low-invasiveness of optical approaches with the power of genetic engineering, are currently revolutionizing the way, the scale and the perspective of investigating brain diseases. The aim of this review is to describe how brain functions can be investigated with optical approaches currently available and to illustrate how these techniques have been adopted to study pathological alterations of brain physiology.

Exploration of the cortical pathophysiology underlying visual disturbances in schizophrenia comorbid with depressive disorder-An evidence from mouse model

INTRODUCTION

Patients with schizophrenia frequently present with visual disturbances including hallucination, and this symptom is particularly prevalent in individuals with comorbid depressive disorders. Currently, little is known about the neurobiological mechanisms of such psychiatric symptoms, and few explanations for the co-occurrence of schizophrenia, depression, and visual disturbances are available.

METHODS

In this study, we generated a mouse schizophrenia model in which depressive symptoms were also induced. We adopted in vivo two-photon calcium imaging and ex vivo electrophysiological recording of the primary visual cortex to reveal the synaptic transmission and neural activity in the mouse schizophrenia model.

RESULTS

In vivo two-photon calcium imaging and ex vivo electrophysiological recording of the primary visual cortex revealed impaired synaptic transmission and abnormal neural activity in the schizophrenia model, but not in the depression model. These functional deficits were most prominent in the combined schizophrenia and depression model.

CONCLUSION

Overall, our data support a mechanism by which the visual cortex plays a role in visual disturbances in schizophrenia.