Multicentre structural and functional MRI

Neuroimaging techniques are likely to continue to improve our understanding of the brain in health and disease, but studies tend to be small, based in one imaging centre and of uncertain generalisability. Multicentre imaging studies therefore have great appeal but it is not yet clear under which circumstances data from different scanners can be combined. The successful harmonisation of multiple Magnetic Resonance Imaging (MRI) machines will increase study power, flexibility and generalisability. I have conducted a detailed study of the performance of three research MRI scanners in Scotland under the name CaliBrain, with the aims of developing reliable, valid image acquisition and analysis techniques that will facilitate multicentre MRI studies in Scotland and beyond. Fourteen healthy volunteers had two brain scans on each of three 1.5T MRI research machines in Aberdeen, Edinburgh and Glasgow. The scans usually took place 2-3 weeks apart. Each scan was performed using an identical scanning protocol consisting of a detailed structural MRI (sMRI) and a range of functional MRI (fMRI) paradigms. The quality assurance (QA) of scanner performance was monitored in all three sites over the duration of the study using a three-part protocol comprising a baseline assessment, regular measures and session specific measures. The analyses have demonstrated that the data are comparable but also that within- and between-scanner variances are evident and that harmonisation work could enhance the level of agreement. The QA data suggest that scanner performance was similar between and within machines over the course of the study. For the structural MRI scans an optimised methodology was utilised to minimise variation in brain geometry between scanners and fit all the scanned brains into a common stereotactic space, such that repeated measures analyses yielded no significant differences over time for any of the three scanners. I examined the reproducibility of the fMRI motor task within and between the three sites. Similar results were obtained in all analyses; areas consistently activated by the task include the premotor, primary motor and supplementary motor areas, the striatum and the cerebellum. Reproducibility of statistical parametric maps was evaluated within and between sites comparing the activation extent and spatial agreement of maps at both the subject and the group level. The results were within the range reported by studies examining the reproducibility of similar tasks on one scanner and reproducibility was found to be comparable within and between sites, with between site comparisons often exceeding the within site measures. A components of variance analysis showed a relatively small contribution of the factor site with subject being the main source of variation. Similar results were obtained for the working memory task. The analysis of the emotional face processing task showed poor reproducibility both within and between sites. These findings suggest that multicentre structural and functional MRI studies are feasible, at least on similar machines, when a consistent protocol is followed in all participating scanning sites, a suitable fMRI task is employed and appropriate analysis methods are used

Correlations between fMRI activation and individual psychotic symptoms in un-medicated subjects at high genetic risk of schizophrenia

<p>Abstract</p> <p>Background:</p> <p>It has been proposed that different types of psychopathology in schizophrenia may reflect distinguishable pathological processes. In the current study we aimed to address such associations in the absence of confounders such as medication and disease chronicity by examining specific relationships between fMRI activation and individual symptom severity scores in un-medicated subjects at high genetic risk of schizophrenia.</p> <p>Methods:</p> <p>Associations were examined across two functional imaging paradigms: the Hayling sentence completion task, and an encoding/retrieval task, comprising encoding (at word classification) and retrieval (old word/new word judgement). Symptom severity was assessed using the positive and negative syndrome scale (PANSS). Items examined were hallucinations, delusions, and suspiciousness/persecution.</p> <p>Results:</p> <p>Associations were seen in the anterior middle temporal gyrus in relation to hallucination scores during the sentence completion task, and in the medial temporal lobe in association with suspiciousness/persecution scores in the encoding/retrieval task. Cerebellar activation was associated with delusions and suspiciousness/persecution scores across both tasks with differing patterns of laterality.</p> <p>Conclusion:</p> <p>These results support a role for the lateral temporal cortex in hallucinations and medial temporal lobe in positive psychotic symptoms. They also highlight the potential role of the cerebellum in the formation of delusions. That the current results are seen in un-medicated high risk subjects indicates these associations are not specific to the established illness and are not related to medication effects.</p

Overactivation of fear systems to neutral faces in schizophrenia

Background The amygdala plays a central role in detecting and responding to fear-related stimuli. A number of recent studies have reported decreased amygdala activation in schizophrenia to emotional stimuli (such as fearful faces) compared with matched neutral stimuli (such as neutral faces). We investigated whether the apparent decrease in amygdala activation in schizophrenia could actually derive from increased amygdala activation to the neutral comparator stimuli. Methods Nineteen patients with schizophrenia and 24 matched control participants viewed pictures of faces with either fearful or neutral facial expressions, and a baseline condition, during functional magnetic resonance imaging scanning. Results Patients with schizophrenia showed a relative decrease in amygdala activation to fearful faces compared with neutral faces. However, this difference resulted from an increase in amygdala activation to the neutral faces in patients with schizophrenia, not from a decreased response to the fearful faces. Conclusions Patients with schizophrenia show an increased response of the amygdala to neutral faces. This is sufficient to explain their apparent deficit in amygdala activation to fearful faces compared with neutral faces. The inappropriate activation of neural systems involved in fear to otherwise neutral stimuli may contribute to the development of psychotic symptoms in schizophrenia

Spectro-temporal processing during speech perception involves left posterior auditory cortex

This functional magnetic resonance imaging study investigates the neural underpinnings of spectro-temporal integration during speech perception. Participants performed an auditory discrimination task on a set of sine-wave analogues that could be perceived as either nonspeech or speech. Behavioural results revealed a difference in the processing mode; spectro-temporal integration occurred during speech perception, but not when stimuli were perceived as nonspeech. In terms of neuroimaging, we observed an activation increase in the left posterior primary and secondary auditory cortex, namely Heschl's gyrus and planum temporale encroaching onto the superior temporal sulcus, reflecting a shift from auditory to speech perception. This finding demonstrates that the left posterior superior temporal lobe is essential for spectro-temporal processing during speech perception

Correlations between fMRI activation and individual psychotic symptoms in un-medicated subjects at high genetic risk of schizophrenia-0

<p><b>Copyright information:</b></p><p>Taken from "Correlations between fMRI activation and individual psychotic symptoms in un-medicated subjects at high genetic risk of schizophrenia"</p><p>http://www.biomedcentral.com/1471-244X/7/61</p><p>BMC Psychiatry 2007;7():61-61.</p><p>Published online 29 Oct 2007</p><p>PMCID:PMC2169235.</p><p></p>symptom dimensions were as follows: Delusions × hallucinations r = 0.34 (p < 0.01); delusions × suspiciousness/persecution r = 0.48 (p < 0.01); hallucinations × suspiciousness/persecution r = 0.32 (p < 0.01)

Correlations between fMRI activation and individual psychotic symptoms in un-medicated subjects at high genetic risk of schizophrenia-2

<p><b>Copyright information:</b></p><p>Taken from "Correlations between fMRI activation and individual psychotic symptoms in un-medicated subjects at high genetic risk of schizophrenia"</p><p>http://www.biomedcentral.com/1471-244X/7/61</p><p>BMC Psychiatry 2007;7():61-61.</p><p>Published online 29 Oct 2007</p><p>PMCID:PMC2169235.</p><p></p>symptom dimensions were as follows: Delusions × hallucinations r = 0.34 (p < 0.01); delusions × suspiciousness/persecution r = 0.48 (p < 0.01); hallucinations × suspiciousness/persecution r = 0.32 (p < 0.01)

Correlations between fMRI activation and individual psychotic symptoms in un-medicated subjects at high genetic risk of schizophrenia-1

<p><b>Copyright information:</b></p><p>Taken from "Correlations between fMRI activation and individual psychotic symptoms in un-medicated subjects at high genetic risk of schizophrenia"</p><p>http://www.biomedcentral.com/1471-244X/7/61</p><p>BMC Psychiatry 2007;7():61-61.</p><p>Published online 29 Oct 2007</p><p>PMCID:PMC2169235.</p><p></p>esenting increasing activation with increasing difficulty. For the encoding/retrieval task, contrasts shown are (c) word classification versus experimental baseline, (d) correct recognition versus experimental baseline, and (e) correct rejection versus experimental baseline. For illustration purposes maps are thresholded at T = 4.5, 4, 6, 5, 5 respectively, extent threshold = 50 voxels. Left hemisphere shown on left of image