Preliminary findings of four-week, task-based anodal prefrontal cortex transcranial direct current stimulation transferring to other cognitive improvements in schizophrenia

Most transcranial Direct Current Stimulation (tDCS) trials of schizophrenia administer few sessions and do not assess transfer effects to other cognitive domains. In a randomized, double-blind, sham-controlled, parallel groups trial, we determined the extent to which 4-weeks of 2 mA tDCS at 20 min/day totalling 20 tDCS sessions administered during a spatial working memory test, with anodal right dorsolateral prefrontal cortex (DLPFC) and cathodal left tempo-parietal junction (TPJ) placement, as an adjunct to antipsychotics reduced auditory hallucinations and improved cognition in 12 outpatients with schizophrenia. Anodal tDCS significantly improved language-based working memory after 2 weeks and verbal fluency after 2 and 4 weeks. Thus, four weeks of tDCS appears to be safe and elicits transfer benefits to other prefrontal-dependent cognitive abilities in schizophrenia.

Adjunctive raloxifene treatment improves attention and memory in men and women with schizophrenia

There is increasing clinical and molecular evidence for the role of hormones and specifically estrogen and its receptor in schizophrenia. A selective estrogen receptor modulator, raloxifene, stimulates estrogen-like activity in brain and can improve cognition in older adults. The present study tested the extent to which adjunctive raloxifene treatment improved cognition and reduced symptoms in young to middle-age men and women with schizophrenia. Ninety-eight patients with a diagnosis of schizophrenia or schizoaffective disorder were recruited into a dual-site, thirteen-week, randomized, double-blind, placebo-controlled, crossover trial of adjunctive raloxifene treatment in addition to their usual antipsychotic medications. Symptom severity and cognition in the domains of working memory, attention/processing speed, language and verbal memory were assessed at baseline, 6 and 13 weeks. Analyses of the initial 6-week phase of the study using a parallel groups design (with 39 patients receiving placebo and 40 receiving raloxifene) revealed that participants receiving adjunctive raloxifene treatment showed significant improvement relative to placebo in memory and attention/processing speed. There was no reduction in symptom severity with treatment compared with placebo. There were significant carryover effects, suggesting some cognitive benefits are sustained even after raloxifene withdrawal. Analysis of the 13-week crossover data revealed significant improvement with raloxifene only in attention/processing speed. This is the first study to show that daily, oral adjunctive raloxifene treatment at 120 mg per day has beneficial effects on attention/processing speed and memory for both men and women with schizophrenia. Thus, raloxifene may be useful as an adjunctive treatment for cognitive deficits associated with schizophrenia.

Peripheral BDNF: a candidate biomarker of healthy neural activity during learning is disrupted in schizophrenia

BACKGROUND

Brain-derived neurotrophic factor (BDNF) is an important regulator of synaptogenesis and synaptic plasticity underlying learning. However, a relationship between circulating BDNF levels and brain activity during learning has not been demonstrated in humans. Reduced brain BDNF levels are found in schizophrenia and functional neuroimaging studies of probabilistic association learning in schizophrenia have demonstrated reduced activity in a neural network that includes the prefrontal and parietal cortices and the caudate nucleus. We predicted that brain activity would correlate positively with peripheral BDNF levels during probabilistic association learning in healthy adults and that this relationship would be altered in schizophrenia.

METHOD

Twenty-five healthy adults and 17 people with schizophrenia or schizo-affective disorder performed a probabilistic association learning test during functional magnetic resonance imaging (fMRI). Plasma BDNF levels were measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

We found a positive correlation between circulating plasma BDNF levels and brain activity in the parietal cortex in healthy adults. There was no relationship between plasma BDNF levels and task-related activity in the prefrontal, parietal or caudate regions in schizophrenia. A direct comparison of these relationships between groups revealed a significant diagnostic difference.

CONCLUSIONS

This is the first study to show a relationship between peripheral BDNF levels and cortical activity during learning, suggesting that plasma BDNF levels may reflect learning-related brain activity in healthy humans. The lack of relationship between plasma BDNF and task-related brain activity in patients suggests that circulating blood BDNF may not be indicative of learning-dependent brain activity in schizophrenia.

Serum testosterone levels are related to cognitive function in men with schizophrenia

BACKGROUND

Sex steroids such as oestrogen and testosterone are potent neurodevelopmental hormones that also play a role in neuromodulation and neuroprotection of the mature brain. Sex steroid hormones may also be involved in the pathophysiology of schizophrenia as reduced circulating sex steroid levels and changes in brain sex steroid receptors are found in people with schizophrenia compared to controls. In men with schizophrenia, recent studies have documented an inverse correlation between serum testosterone and negative symptoms. Our study sought to confirm whether men with schizophrenia had lower levels of testosterone relative to controls and to determine whether lower testosterone levels were related to higher symptom severity and impaired cognition.

METHOD

Circulating serum hormone levels (testosterone, oestrogen, and prolactin), cognitive function and symptoms were assessed in 29 chronically ill men with schizophrenia or schizoaffective disorder. Twenty healthy men were recruited as a comparison group. A series of regression analyses were performed to determine the extent to which circulating sex steroid hormone levels predict cognition and symptoms in men with schizophrenia.

RESULTS

We did not find a significant difference in serum testosterone levels between groups. However, circulating testosterone levels significantly predicted performance on verbal memory, processing speed, and working memory in men with schizophrenia. With the exception of an effect of oestrogen on verbal memory, circulating sex steroid levels did not predict cognitive function in healthy men. Testosterone levels were not related to positive or negative symptom severity, but testosterone influenced excitement/hostility levels in our schizophrenia sample.

CONCLUSIONS

The results suggest that circulating sex steroids may modulate cognitive deficits associated with schizophrenia.

Hearing a voice in the noise: auditory hallucinations and speech perception

BACKGROUND

It has recently been suggested that auditory hallucinations are the result of a criterion shift when deciding whether or not a meaningful signal has emerged. The approach proposes that a liberal criterion may result in increased false-positive identifications, without additional perceptual deficit. To test this hypothesis, we devised a speech discrimination task and used signal detection theory (SDT) to investigate the underlying cognitive mechanisms.

METHOD

Schizophrenia patients with and without auditory hallucinations and a healthy control group completed a speech discrimination task. They had to decide whether a particular spoken word was identical to a previously presented speech stimulus, embedded in noise. SDT was used on the accuracy data to calculate a measure of perceptual sensitivity (Az) and a measure of response bias (beta). Thresholds for the perception of simple tones were determined.

RESULTS

Compared to healthy controls, perceptual thresholds were higher and perceptual sensitivity in the speech task was lower in both patient groups. However, hallucinating patients showed increased sensitivity to speech stimuli compared to non-hallucinating patients. In addition, we found some evidence of a positive response bias in hallucinating patients, indicating a tendency to readily accept that a certain stimulus had been presented.

CONCLUSIONS

Within the context of schizophrenia, patients with auditory hallucinations show enhanced sensitivity to speech stimuli, combined with a liberal criterion for deciding that a perceived event is an actual stimulus.

Grip strength in children

The grip strength in a group of 487 healthy children aged between 5 years and 15 years was measured. There was a clear correlation between age and grip strength. Up to the age of 12 years, there was a striking parallellism between boys and girls. From the age of 13 years, boys developed a 25% stronger grip force than girls. The difference between the dominant and nondominant hand grip was not significant, but was constantly stronger in the right hand for right-hand dominant children. There was a high variation in grip forces (from 6.9 kg to 38.4 kg).

Human melanoma targeting with alpha-MSH-melphalan conjugate

A conjugate made of alpha-MSH as a drug carrier and melphalan has been designed in order to target human melanoma cells. Iodination of the alpha-MSH moiety led to a relatively stable tracer which could be easily separated and analysed by reverse phase high pressure liquid chromatography. The conjugate was found to be unstable at neutral pH and a serious denaturation can take place at concentrations exceeding 100 micrograms/ml, especially in plasma. Receptor-mediated cytotoxicity has been shown by the use of cultured alpha-MSH receptor positive/negative cells as well as in vivo B16 murine melanoma model. Body distribution and uptake of the labelled compound were unaltered as compared to those of labelled free hormone. alpha-MSH receptor recognition properties also remained unchanged with a better apparent affinity of the conjugate probably due to the alkylating activity of melphalan itself. Using human melanoma dendritic cells expressing more than 10,000 alpha-MSH binding sites per cell as an in vitro model, we were able to demonstrate higher cytotoxicities as compared to melphalan-treated cells. In contrast, melanoma cells with low receptivity did not show higher cytotoxicity. P388D1 mouse plasmocytoma cells lacking receptors were much more sensitive to melphalan than the conjugate. This phenomenon appeared to be related with the number of binding sites expressed at the time of the experiment as well as cell differentiation and the doubling time. Our findings strongly support the concept of a receptor-mediated cytotoxicity and may enable the in vivo melphalan delivery to target tissues to be increased, achieving an improvement of drug penetration inside melanoma cells.