Animal and human studies have suggested that cannabidiol (CBD) may possess anxiolytic properties, but how these effects are mediated centrally is unknown. The aim of the present study was to investigate this using functional neuroimaging. Regional cerebral blood flow (rCBF) was measured at rest using 99m Tc-ECD SPECT in 10 healthy male volunteers, randomly divided into two groups of five subjects. Each subject was studied on two occasions, 1 week apart. In the first session, subjects were given an oral dose of CBD (400 mg) or placebo, in a double-blind procedure. SPECT images were acquired 90 min after drug ingestion. The Visual Analogue Mood Scale was applied to assess subjective states. In the second session, the same procedure was performed using the drug that had not been administered in the previous session. Within-subject between-condition rCBF comparisons were performed using statistical parametric mapping (SPM). CBD significantly decreased subjective anxiety and increased mental sedation, while placebo did not induce significant changes. Assessment of brain regions where anxiolytic effects of CBD were predicted a priori revealed two voxel clusters of significantly decreased ECD uptake in the CBD relative to the placebo condition (po0.001, uncorrected for multiple comparisons). These included a medial temporal cluster encompassing the left amygdala-hippocampal complex, extending into the hypothalamus, and a second cluster in the left posterior cingulate gyrus. There was also a cluster of greater activity with CBD than placebo in the left parahippocampal gyrus (po0.001). These results suggest that CBD has anxiolytic properties, and that these effects are mediated by an action on limbic and paralimbic brain areas.

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Objective: To investigate the relation between atrophy of the hippocampal region and brain functional patterns during episodic memory processing in Alzheimer's disease. Patients and methods: Whole brain structural magnetic resonance imaging (MRI) data and single photon emission computed tomography (SPECT) measures of regional cerebral blood flow (rCBF) were obtained during a verbal recognition memory task in nine subjects with mild Alzheimer's disease and 10 elderly healthy controls. Using the statistical parametric mapping approach, voxel based comparisons were made on the MRI data to identify clusters of significantly reduced grey matter concentrations in the hippocampal region in the Alzheimer patients relative to the controls. The mean grey matter density in the voxel cluster of greatest hippocampal atrophy was extracted for each Alzheimer subject. This measure was used to investigate, on a voxel by voxel basis, the presence of significant correlations between the degree of hippocampal atrophy and the rCBF SPECT measures obtained during the memory task. Results: Direct correlations were detected between the hippocampal grey matter density and rCBF values in voxel clusters located bilaterally in the temporal neocortex, in the left medial temporal region, and in the left posterior cingulate cortex during the memory task in the Alzheimer's disease group (p < 0.001). Conversely, measures of hippocampal atrophy were negatively correlated with rCBF values in voxel clusters located in the frontal lobes, involving the right and left inferior frontal gyri and the insula (p < 0.001). Conclusions: Hippocampal atrophic changes in Alzheimer's disease are associated with reduced functional activity in limbic and associative temporal regions during episodic memory processing, but with increased activity in frontal areas, possibly on a compensatory basis.

Cognitive and olfactory impairments have previously been demonstrated in patients with spinocerebellar ataxia type 3 (SCA3), also known as Machado-Joseph disease (MJD)-SCA3/MJD. We investigated changes in regional cerebral blood flow (rCBF) using single-photon emission computed tomography (SPECT) imaging in a cohort of Brazilian patients with SCA3/MJD. The aim of the present study was to evaluate the correlation among rCBF, cognitive deficits, and olfactory dysfunction in SCA3/MJD. Twenty-nine genetically confirmed SCA3/MJD patients and 25 control subjects were enrolled in the study. The severity of cerebellar symptoms was measured using the International Cooperative Ataxia Rating Scale and the Scale for the Assessment and Rating of Ataxia. Psychiatric symptoms were evaluated by the Hamilton Anxiety Scale and Beck Depression Inventory. The neuropsychological assessment consisted of Spatial Span, Symbol Search, Picture Completion, the Stroop Color Word Test, Trail Making Test (TMT), and Phonemic Verbal Fluency. Subjects were also submitted to odor identification evaluation using the 16-item Sniffin' Sticks. SPECT was performed using ethyl cysteine dimer labeled with technetium-99m. SCA3/MJD patients showed reduced brain perfusion in the cerebellum, temporal, limbic, and occipital lobes compared to control subjects (pFDR <0.001). A significant positive correlation was found between the Picture Completion test and perfusion of the left parahippocampal gyrus and basal ganglia in the patient group as well as a negative correlation between the TMT part A and bilateral thalamus perfusion. The visuospatial system is affected in patients with SCA3/MJD and may be responsible for the cognitive deficits seen in this disease.

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