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Magnetic resonance spectroscopy (MRS) is a non-invasive in vivo method used to quantify metabolites that are relevant to a wide range of brain processes. This paper briefly describes neuroimaging using MRS and provides a systematic review of its application to anxiety disorders.
A literature review was performed in the PubMed, Lilacs and Scielo databases using the keywords spectroscopy and anxiety disorder. References of selected articles were also hand-searched for additional citations.
Recent studies have shown that there are significant metabolic differences between patients with anxiety disorders and healthy controls in various regions of the brain. Changes were mainly found in N-acetylaspartate, which is associated with neuronal viability, but some of them were also seen in creatine, a substance that is thought to be relatively constant among individuals with different pathological conditions.
MRS is a sophisticated neuroimaging technique that has provided useful insights into the biochemical and neurobiological basis of many anxiety disorders. Nevertheless, its utilization in some anxiety disorders is still modest, particularly social phobia and generalised anxiety. Although it is an extremely useful advance in neuroimaging, further research in other brain areas and patient populations is highly advisable.
Prefrontal and/or temporo-limbic abnormalities associated with antisocial personality disorder (APD), high psychopathy scores and violent behaviours can readily be evaluated by neuroimaging methods.
In this study, we compared the brain metabolites in adult male military conscripts with APD, high psychopathy scores and serious violent crimes (n = 15) with age- and educational-level-matched healthy controls (n = 15) by means of magnetic resonance spectroscopy.
All cases were diagnosed by means of the Diagnostic Statistical Manual-IV APD module of the Structured Clinical Interview for DSM III-R Axis II Disorders (SCID-II) semistructured questionnaire in Turkish. The psychopathy scores were evaluated by means of the Hare Psychopathy Checklist-Revised translated into Turkish (PCL-R). PCL-R is a 20-item, reliable and valid instrument for assessment of psychopathy, both in categorical and dimensional natures. All patients had a total score of 29 (of possible 40) or higher from PCL-R, indicating a high degree of psychopathy.
Our results showed no significant differences in ratio of N-acetyl aspartate (NAA), creatine (Cr) and choline-related compounds in the right dorsolateral prefrontal cortex, anterior cingulate cortex (ACC) and amygdala–hippocampus regions of cases compared with controls. ACC NAA/Cr was significantly negatively correlated with both the PCL-R total score and the PCL-R factor I score (interpersonal/affective problems) among the cases.
As ACC plays an important role in decision-making and emotional information processing, we postulate that the lower NAA/Cr ratio, suggesting impaired neural integrity, may increase the severity of interpersonal/affective problems of the psychopathy factor in male subjects exhibiting APD, high psychopathy overall scores and violent crimes.
Studies investigating the cognitive effects of serotonin depletion, using the technique of acute tryptophan depletion (ATD) by dietary means, have generally suggested that ATD impairs delayed verbal recall and recognition. In two previous studies in the elderly, this result has not been replicated and ATD impaired working memory. These results may be susceptible to type II error but a similar testing schedule in the individual studies allows data to be pooled in a larger analysis.
Data from two separate double-blind placebo-controlled studies of the effects of ATD on cognitive function in the elderly were combined. In one study, a low dose and in the other a high dose of amino acids was used. In a repeated measures analysis of variance, the effects of ATD and the interaction of this with the other factors (age, gender and dose) on cognitive measures was examined.
Data from 31 healthy subjects aged between 60 and 81 years were analysed. There were no main effects of ATD or consistent interactions between ATD and age, gender or dose. There were significant interactions between ATD, gender and dose. When tryptophan depleted, females having the higher dose drink had reduced scores on Digit span and immediate recall on the Rey Auditory Verbal Learning Test.
The enlarged data set did not confirm an overall effect of ATD on working memory or on delayed word recall but does suggest an effect of ATD on encoding or registration in the subgroup of females receiving a higher strength drink.
There have been limited data available on the prevalence of structural brain abnormalities in asymptomatic individuals and a growing interest in the various ethical issues related to reporting of such findings. This study evaluated the prevalence of incidental abnormalities on brain magnetic resonance imaging (MRI) in a random sample of 60- to 64-year-old community-dwelling individuals as well as successfully followed a referral pathway taking into account of the various ethical issues related to the referral process. The Personality and Total Health (PATH) Project was designed to study the risk and protection factors of normal ageing, dementia and other neuropsychiatric disorders.
MRI scans were performed in randomly selected 478 healthy, community-dwelling 60- to 64-year-old individuals. All scans were reported for abnormalities by a radiologist.
Abnormalities were detected in 22 (4.8%) subjects, comprising 10 tumours (pituitary adenoma 4, meningioma 3, suprasellar tumour 1, cavernous haemangioma 1, subarachnoid lipoma 1), 6 infarct-like lesions, 2 arachnoid cysts, 1 possible normal pressure hydrocephalus, and 1 each of unconfirmed aneurysm and mesial temporal sclerosis. Further evaluation led to novel intervention in one case of pituitary adenoma, and adjustment of drug treatment to modify risk factors in two cases with subclinical infarction.
While no case required immediate referral or urgent surgical intervention, the change in the outcome of treatment of some cases suggests that appropriate referral process should be in place when researchers study large number of subjects in the community using MRI of the brain.
The perception of music without a stimulus, or musical hallucination, is reported in both organic and psychiatric disorders. It is most frequently described in the elderly with associated hearing loss and accompanied by some degree of insight. In this setting it is often referred to as ‘musical hallucinosis’. The aim of the authors was to present examples of this syndrome and review the current understanding of its neurobiological basis.
We describe three cases of persons experiencing musical hallucinosis in the context of hearing deficits with varying degrees of associated central nervous system abnormalities.
Putative neurobiological mechanisms, in particular those involving de-afferentation of a complex auditory recognition system by complete or partial deafness, are discussed in the light of current information from the literature.
Musical hallucinosis can be experienced in those patients with hearing impairment and is phenomenologically distinct for hallucinations described in psychiatric disorders.