No abstract

The main ingredient in cannabis, Δ(9)-tetrahydrocannabinol (THC), can elicit acute psychotic reactions in healthy individuals and precipitate relapse in schizophrenic patients. However, the neural mechanism of this is unknown. We tested the hypothesis that THC psychopathology is related to changes in electroencephalography (EEG) power or inter-regional coherence. In a within-subjects design, participants (n=16) were given intravenous THC (1.25 mg) or placebo under double-blind conditions, during EEG recordings. Using fast-Fourier transform, EEG data were analyzed for power and coherence in the delta (1-3.5 Hz), theta (3.5-7 Hz), alpha (8-13 Hz), beta (14-25 Hz), low-gamma (30-40 Hz), and high-gamma (60-70 Hz) bands during engagement in the n-back test of working memory (WM). Compared with placebo, THC evoked positive and negative psychotic symptoms, as measured by the positive and negative syndrome scale (p<0.001) and slowed WM performance (p<0.05). Under THC, theta power was specifically reduced, (p<0.001) regardless of WM load; however, the reduction showed no relationship with psychotic symptoms or WM impairment. Coherence between bi-frontal electrodes in the theta band was also reduced by THC (p<0.05) and these reductions correlated with the change-in positive psychotic symptoms (rho=0.79, p<0.001). Bi-frontal specificity was suggested by the absence of a relationship between psychotic symptoms and fronto-parietal coherence. The results reveal that the pro-psychotic effects of THC might be related to impaired network dynamics with impaired communication between the right and left frontal lobes.

We investigated the epidemiology of systemic lupus erythematosus (SLE) in the Marshfield Epidemiologic Study Area (MESA), a defined rural region where nearly all residents obtain their health care from a large clinic system. Computerized medical records were searched to identify MESA residents diagnosed with SLE from 1991 through 2001. Medical records were manually reviewed for all selected patients to identify cases of SLE using the 1982 revised American College of Rheumatology criteria. Patients with > or = 4 criteria were classified as definite SLE. Age- and gender-specific SLE incidence rates (1991-2001), the population prevalence rate of SLE on 31 December 2001 and survival rates were calculated. We identified 117 MESA residents with definite SLE. The average age-adjusted incidence of definite SLE was 5.1 per 100 000 per year (95% CI: 3.6, 6.6) and the age-adjusted population prevalence was 78.5 per 100 000 (95% CI: 59.0, 98.0). The mean age at diagnosis among the 44 incident cases was 51.7 years (range: 14-90 years). Positive anti-nuclear antibody (ANA), hematologic abnormalities, arthritis and renal disease were common at diagnosis. Five- and 10-year survival rates were 88% and 76%, respectively. Epidemiologic characteristics of SLE in this rural Caucasian population are generally similar to those reported by other US studies. One notable difference is a relatively high incidence of SLE in older adults.

Neuromagnetic spectral distributions when silently viewing words and non-words were investigated using a 151-channel whole head MEG system. The data were analyzed with synthetic aperture magnetometry (SAM). The dominant changes of spectral power were identified in the parietal and occipital cortices in 15-30 Hz, 30-60 Hz and 60-125 Hz bands following both word and non-word stimulations. The changes in Broca's and Wernicke's areas were consistently observed in 60-125 Hz bands, mainly following word stimulation. The results indicated that the occipital and parietal cortices were most probably involved in visuospatial processing of words and non-words. The language areas, particularly Broca's and Wernickes's areas, might be involved in implicit word processing such as verbal searching and/or internal speech.