A Primer on Interoception and its Importance in Psychiatry

Interoception is the perception of signals from inside the body. It plays a significant role in the nervous, cardiovascular, respiratory, gastrointestinal, genitourinary, and endocrine systems. It is also closely related to the autonomic nervous system and inflammatory pathways and plays a significant role in our optimal functioning. Recently, interoception has gained more attention in neuropsychiatric research. Anatomical and physiological aspects of interoception like relevant brain areas, the role of the vagus nerve, and the autonomic nervous system are gradually being understood. Different facets of interoception like interoceptive attention, detection, magnitude, discrimination, accuracy, awareness, and appraisal have been proposed and their assessments and importance are being evaluated. Further, interoception is often dysregulated or abnormal in psychiatric disorders. It has been implicated in the psychopathology, etiopathogenesis, clinical features and treatment of mood, anxiety, psychotic, personality and addiction-related disorders. This narrative review attempts to provide a nuanced understanding of the pathway(s), components, functions, assessments, and problems of interoception and will help us to detect its disturbances and evaluate its impact on psychiatric disorders, leading to a better perspective and management. This will also advance interoception-related research.

Pars Triangularis Volume Asymmetry and Schneiderian First Rank Symptoms in Antipsychotic-naïve Schizophrenia

Objective@#Schizophrenia is a disorder of language and self, with first-rank symptoms (FRS) as one of the predominant features in a subset of patients. Abnormal language lateralization is hypothesized to underlie the neurobiology of FRS in schizophrenia. The role of Broca’s area with its right-hemispheric counterpart, consisting of pars triangularis (PTr) and pars opercularis (POp) of the inferior frontal gyrus in FRS is undetermined. We compared the volumes and asymmetries of PTr & POp in anti-psychotic-naive schizophrenia patients with FRS (FRS[＋]) with those without FRS (FRS[−]) and healthy-controls (HC) using three dimensional, interactive, semi-automated volumetric morphometry. @*Methods@#Antipsychotic naïve FRS(＋) (n = 27), FRS(−) (n = 24) and HC (n = 51) were carefully assessed with structured and semi-structured clinical tools. T1-weighted images were acquired in a 3T scanner. Volumes of regions of interest were measured independently for both sides using slicer-3D software, and asymmetry indices were calculated. @*Results@#FRS(＋) but not FRS(−) had a significant volume deficit in right PTr after controlling for the potential confounding effects of age, sex, and intracranial volume (p = 0.029). There was a significant leftward asymmetry of PTr in patients with FRS (i.e., leftward asymmetry in patients) (p = 0.026). No significant volume/asymmetry abnormalities were observed in POp. @*Conclusion@#Study findings suggest reduced right PTr volume with leftward asymmetry to be associated with FRS in schizophrenia. This is consistent with the loss of Yakovlevian torque in schizophrenia. Role of PTr in the neurobiology of schizophrenia as a disorder of self, speech, and social cognition needs further systematic evaluation in future research.

Pars Triangularis Volume Asymmetry and Schneiderian First Rank Symptoms in Antipsychotic-naïve Schizophrenia

Objective@#Schizophrenia is a disorder of language and self, with first-rank symptoms (FRS) as one of the predominant features in a subset of patients. Abnormal language lateralization is hypothesized to underlie the neurobiology of FRS in schizophrenia. The role of Broca’s area with its right-hemispheric counterpart, consisting of pars triangularis (PTr) and pars opercularis (POp) of the inferior frontal gyrus in FRS is undetermined. We compared the volumes and asymmetries of PTr & POp in anti-psychotic-naive schizophrenia patients with FRS (FRS[＋]) with those without FRS (FRS[−]) and healthy-controls (HC) using three dimensional, interactive, semi-automated volumetric morphometry. @*Methods@#Antipsychotic naïve FRS(＋) (n = 27), FRS(−) (n = 24) and HC (n = 51) were carefully assessed with structured and semi-structured clinical tools. T1-weighted images were acquired in a 3T scanner. Volumes of regions of interest were measured independently for both sides using slicer-3D software, and asymmetry indices were calculated. @*Results@#FRS(＋) but not FRS(−) had a significant volume deficit in right PTr after controlling for the potential confounding effects of age, sex, and intracranial volume (p = 0.029). There was a significant leftward asymmetry of PTr in patients with FRS (i.e., leftward asymmetry in patients) (p = 0.026). No significant volume/asymmetry abnormalities were observed in POp. @*Conclusion@#Study findings suggest reduced right PTr volume with leftward asymmetry to be associated with FRS in schizophrenia. This is consistent with the loss of Yakovlevian torque in schizophrenia. Role of PTr in the neurobiology of schizophrenia as a disorder of self, speech, and social cognition needs further systematic evaluation in future research.

A Functional Domain Based Approach in Neurocognitive Rehabilitation with Transcranial Direct Current Stimulation: A Case Report

Transcranial direct current stimulation (tDCS) is a novel brain stimulation technique which has kindled hope in alleviating motor, language as well as cognitive deficits in neuronal injury. Current case report describes application of tDCS in two phases using two different protocols in a patient with hypoxic injury. In the first phase anodal stimulation of dorsolateral prefrontal cortex improved the language fluency. Subsequently, after 6 months second phase application of anodal stimulation over posterior parietal region targeted arithmetic and working memory deficits. Individualising the treatment protocols of brain stimulation, based on the lesion and the functional deficits, for neuro-rehabilitation is emphasised.

Neural Correlates of a Perspective-taking Task Using in a Realistic Three-dimmensional Environment Based Task: A Pilot Functional Magnetic Resonance Imaging Study

OBJECTIVE: Perspective-taking ability is an essential spatial faculty that is of much interest in both health and neuropsychiatric disorders. There is limited data on the neural correlates of perspective taking in the context of a realistic three-dimensional environment. We report the results of a pilot study exploring the same in eight healthy volunteers. METHODS: Subjects underwent two runs of an experiment in a 3 Tesla magnetic resonance imaging (MRI) involving alternate blocks of a first-person perspective based allocentric object location memory task (OLMT), a third-person perspective based egocentric visual perspective taking task (VPRT), and a table task (TT) that served as a control. Difference in blood oxygen level dependant response during task performance was analyzed using Statistical Parametric Mapping software, version 12. Activations were considered significant if they survived family-wise error correction at the cluster level using a height threshold of p<0.001, uncorrected at the voxel level. RESULTS: A significant difference in accuracy and reaction time based on task type was found. Subjects had significantly lower accuracy in VPRT compared to TT. Accuracy in the two active tasks was not significantly different. Subjects took significantly longer in the VPRT in comparison to TT. Reaction time in the two active tasks was not significantly different. Functional MRI revealed significantly higher activation in the bilateral visual cortex and left temporoparietal junction (TPJ) in VPRT compared to OLMT. CONCLUSION: The results underscore the importance of TPJ in egocentric manipulation in healthy controls in the context of reality-based spatial tasks.

Transcranial Direct Current Stimulation in Schizophrenia

Transcranial direct current stimulation (tDCS) is an upcoming treatment modality for patients with schizophrenia. A series of recent observations have demonstrated improvement in clinical status of schizophrenia patients with tDCS. This review summarizes the research work that has examined the effects of tDCS in schizophrenia patients with respect to symptom amelioration, cognitive enhancement and neuroplasticity evaluation. tDCS is emerging as a safe, rapid and effective treatment for various aspects of schizophrenia symptoms ranging from auditory hallucinations-for which the effect is most marked, to negative symptoms and cognitive symptoms as well. An interesting line of investigation involves using tDCS for altering and examining neuroplasticity in patients and healthy subjects and is likely to lead to new insights into the neurological aberrations and pathophysiology of schizophrenia. The mechanistic aspects of the technique are discussed in brief. Future work should focus on establishing the clinical efficacy of this novel technique and on evaluating this modality as an adjunct to cognitive enhancement protocols. Understanding the mechanism of action of tDCS as well as the determinants and neurobiological correlates of clinical response to tDCS remains an important goal, which will help us expand the clinical applications of tDCS for the treatment of patients with schizophrenia.