Stephen Lottenberg

Regional glucose metabolic changes after learning a complex visuospatial/motor task: A positron emission tomographic study.

Regional cerebral glucose metabolic rate (GMR) quantified with positron emission tomography (PET) with 18-fluoro-2-deoxyglucose (FDG) was measured twice in 8 young men performing a complex visuospatial/motor task (the computer game Tetris), before and after practice. After 4-8 weeks of daily practice on Tetris, GMR in cortical surface regions decreased despite a more than 7-fold increase in performance. Subjects who improved their Tetris performance the most after practice showed the largest glucose metabolic decreases after practice in several areas. These results suggest that learning may result in decreased use of extraneous or inefficient brain areas. Changes in regional subcortical glucose metabolic rate with practice may reflect changes in cognitive strategy that are a part of the learning process.

A positron emission tomography [18F]deoxyglucose study of developmental stuttering.

Positron emission tomography using [18F]deoxyglucose (FDG) as a marker of regional brain metabolism was used to investigate the neural substrate of stuttering. Four patients with severe developmental stuttering were studied while reading aloud to another person (stuttering condition) and while reading aloud in unison with someone else (non-stuttering condition). The patients were also compared with four normal controls reading aloud by themselves. In the stuttering condition, significant decreases in regional glucose metabolism in Brocas area, Wernickes area and frontal pole were seen compared with themselves while not stuttering. These differences were also seen in stuttering condition compared with normal controls. Significantly lower left caudate metabolism was seen in patients during both stuttering and non-stuttering conditions compared with normal controls. A circuit for stuttering is proposed based on these findings.

Noninvasive evaluation of hepatic fibrosis using frequency demodulation of ultrasound signals

A new ultrasound image can be produced by frequency demodulation (FM) of the conventional ultrasound signal. This new FM image appeared to produce a more accurate representation of the fine structure of the liver. The individual features of the FM image were correlated with hepatic portal fibrosis and cirrhosis on liver biopsy in 34 patients with minimal hepatic fat and sinusoidal collagen. An overall ultrasound score correlated with portal fibrosis (r=0.788;P<0.001). We conclude that the FM image may be helpful in measuring and following the progression of hepatic fibrosis in patients with chronic liver disease.