Patterns Of Functional Abnormalities Research Articles

Neural Correlates of Schizotypal Personality Disorder: A Systematic Review of Neuroimaging and EEG Studies.

Schizotypal Personality Disorder (SPD) is a cluster A personality disorder affecting 1.0% of the general population, characterised by disturbances in cognition and reality testing dimensions, affected regulation, and interpersonal function. SPD shares similar but attenuated phenomenological, genetic, and neurobiological abnormalities with Schizophrenia (SCZ) and is described as part of schizophrenia spectrum disorders. The aim of this work was to identify major neural correlates of SPD. This is a systematic review conducted according to PRISMA statement. The protocol was prospectively registered in PROSPERO - International prospective register of systematic reviews. The review was performed to summarise the most comprehensive and updated evidence on functional neuroimaging and neurophysiology findings obtained through different techniques (DW- MRI, DTI, PET, SPECT, fMRI, MRS, EEG) in individuals with SPD. Of the 52 studies included in this review, 9 were on DW-MRI and DTI, 11 were on PET and SPECT, 11 were on fMRI and MRS, and 21 were on EEG. It was complex to synthesise all the functional abnormalities found in a single, unified, pathogenetic pathway, but a common theme emerged: the dysfunction of brain circuits including striatal, frontal, temporal, limbic regions (and their networks) together with a dysregulation along the dopaminergic pathways. Brain abnormalities in SPD are similar, but less marked, than those found in SCZ. Furthermore, different patterns of functional abnormalities in SPD and SCZ have been found, confirming the previous literature on the 'presence' of possible compensatory factors, protecting individuals with SPD from frank psychosis and providing diagnostic specificity.

S9. NEUROIMAGING AND NEUROPHYSIOLOGY BIOMARKERS OF SCHIZOTYPAL PERSONALITY DISORDER: A SYSTEMATIC REVIEW

BackgroundSchizotypal personality disorder (SPD) is a cluster A personality disorder affecting 1.0% of general population, characterised by disturbances in cognition and reality testing dimensions, affect regulation, and interpersonal function. SPD shares similar but attenuated phenomenological, genetic, and neurobiological abnormalities with schizophrenia (SCZ) and is described as part of the continuum of schizophrenia spectrum disorders. Neuroimaging and neurophysiology are the main non-invasive techniques for the investigation of brain structure and function, so they play a crucial role in psychiatric research and for their applications into clinical practice. The present review aims to systematically identify the major neuroimaging and neurophysiology biomarkers of SPD.MethodsThe present review has been conducted according to PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) statement. The protocol was prospectively registered in PROSPERO - International prospective register of systematic reviews. The systematic review was performed to summarise the most comprehensive and updated evidence on functional neuroimaging and neurophysiology findings obtained through different techniques (DW-MRI, DTI, PET, SPECT, fMRI, MRS, EEG) in subjects with SPD.ResultsThe search initially yielded 218 records. After study selection and reference screening, the final set comprised 52 studies. Of the 52 studies included in this review, 9 were on DW-MRI and DTI, 11 were on PET and SPECT, 11 were on fMRI and MRS, and 21 were on EEG. Although it was complex to synthesise all the functional abnormalities found in the included studies into a single, unified, pathogenetic pathway, a common theme that emerged was the dysfunction of brain circuits including striatal, frontal, temporal, limbic regions, and their networks. This dysfunction may be the result of a dysregulation along the dopaminergic pathways and lead to deficits or defects in processes that organise a person’s cognitive-perceptual evaluation of the environment and the relatedness to him/herself. As for the limitations, a quantitative data synthesis was not planned for this work, therefore no meta-analytical integrations are presented in this review. The results of individual neuroimaging studies, in fact, are not comparable due to small and heterogeneous samples, analytical flexibility, or differences in imaging modalities and behavioral tasks.DiscussionBrain abnormalities in SPD are similar, but less marked, than those found in SCZ, and they do not mirror each other. In fact, different patterns of functional abnormalities in SPD and SCZ have been found in this systematic review, suggesting the ‘presence’ of possible compensatory factors, protecting subjects with SPD from frank psychosis and providing diagnostic specificity. Specifically, SPD differentiates from SCZ by showing: (a) milder frontal-striatal-temporal white matter dysconnectivity in DTI studies, (b) lesser frontal and striatal dysfunction and a decreased striatal dopaminergic activity in PET and SPECT studies, respectively, (c) different patterns of dysfunctional activation of frontal-striatal-thalamic circuitry during attentional processing in fMRI studies, and (d) milder alterations in EEG sensory gating and no evidence of alterations in EEG auditory or visual processing.

Cerebral imaging and physiopathology of Alzheimer's disease

Alzheimer's disease (AD) is characterised by macroscopic cerebral damages which can be studied in vivo with neuroimaging techniques, even at the earliest stage. Studies were conducted in patients with amnestic Mild Cognitive Impairment (MCI) who best represent incipient AD. Right temporo-parietal hypometabolism, assessed by resting-state (18)FDG-PET, distinguishes patients who further develop AD from those who remain stable. From the pre-dementia stage of MCI, atrophy of the hippocampal region detected with structural MRI contrasts with functional alteration of the posterior cingulate gyrus measured with (18)FDG-PET and SPECT. Results from resting-state fMRI confirm this pattern of functional abnormalities and highlight changes in the hippocampal region functional connectivity, decreased with the posterior cingulate region, and increased with some frontal areas. Altogether with a structural connectivity impairment highlighted by DTI, those results support the hypothesis of a dysconnexion between the hippocampal and the posterior cingulate regions. Finally, activation fMRI data support the hypothesis of a functional compensation involving not only the frontal cortex but also, at the pre-dementia stage, the hippocampal region. Thus, this synthesis focuses on the hypotheses of dysconnexion and functional compensation, suggested to explain the discrepancies between the structural and functional alteration patterns, as well as on relevant results from resting-state fMRI, DTI and activation fMRI studies. Furthermore, this synthesis emphasizes the relevance of neuroimaging for the early detection of AD.

Engagement of brain areas implicated in processing inner speech in people with auditory hallucinations.

The neurocognitive basis of auditory hallucinations is unclear, but there is increasing evidence implicating abnormalities in processing inner speech. Previous studies have shown that people with schizophrenia who were prone to auditory hallucinations demonstrated attenuated activation of brain areas during the monitoring of inner speech. To investigate whether the same pattern of functional abnormalities would be evident as the rate of inner speech production was varied. Eight people with schizophrenia who had a history of prominent auditory hallucinations and eight control participants were studied using functional magnetic resonance imaging while the rate of inner speech generation was varied experimentally. When the rate of inner speech generation was increased, the participants with schizophrenia showed a relatively attenuated response in the right temporal, parietal, parahippocampal and cerebellar cortex. In people with schizophrenia who are prone to auditory hallucinations, increasing the demands on the processing of inner speech is associated with attenuated engagement of the brain areas implicated in verbal self-monitoring.