Sensitivity and specificity for dementia of population-based criteria for cognitive impairment: the MoVIES project.

BACKGROUND: Few norms exist for the elderly on the cognitive tests commonly used to screen for dementia; conventional cutpoints used in clinical settings may be of limited value in population screening. A particular problem is posed by elderly populations with low educational levels, as performance on most cognitive tests is affected by education. Thus, a healthy but poorly educated population may obtain test scores in the range considered impaired in the clinical setting. METHODS: A random sample of 1,367 subjects aged 65+ years was screened for dementia in a rural community in Southwestern Pennsylvania. Two sets of cognitive measures were used: a global cognitive scale (the MMSE) and a brief battery of tests tapping a variety of cognitive domains. Rather than using a priori cutoff scores, we examined the specificity and sensitivity for dementia of two operationally defined levels of cognitive impairment, at the 5th and 10th percentiles of the study sample on each set of measures. RESULTS: Results suggest that the screening of multiple cognitive domains at the 10th percentile had significantly greater sensitivity but not lower specificity for definite dementia than did the use of the single global scale. CONCLUSION: Our data support the use of population-based cutpoints over standard cutoff scores, in that the global scale at the conventional cutoff was less sensitive than the battery at the same percentile, and because adequate norms do not exist for tests such as those in the battery.

Swimming in Aplysia brasiliana: analysis of behavior and neuronal pathways.

Swimming of Aplysia brasiliana was analyzed using time-lapse video and computer graphics techniques to quantify the cyclical movements of different regions of the parapodia. Both the speed of swimming and the period of oscillation are temperature dependent, whereas the metachronal offset is not. The parapodial arterial supply is described; ligation of parapodial arteries does not affect the parapodial motions. Peripheral and central lesions indicated that (1) the anterior parapodial nerve plays the major role in parapodial flapping, (2) a separate neuronal oscillator resides in each pedal ganglion, (3) bilateral coordination is mediated via the pedal commissure, and (4) the swimming "command" pathway is the cerebro-pedal connective. During regular parapodial flapping the speed of level midwater swimming is constant throughout the cycle, suggesting that swimming is not produced by jet propulsion. An alternative propulsion model is advanced.

Neuroethological studies of freely swimming Aplysia brasiliana.

Recently developed neurophysiological and behavioural techniques were used to study swimming in the marine gastropod Aplysia brasiliana. Aplysia swim by bilateral parapodial flapping with an anterior to posterior metachronal wave. Parapodial oscillations are measured from video records. Population recordings from nerves innervating the parapodia during normal swimming in intact Aplysia reveal synchronous phasic activity in large efferent units associated with parapodial opening. Isolated brain studies and stimulation of central pathways in intact animals suggest a central pattern generator. We conclude that the output of the neuronal oscillator that controls parapodial flapping radiates synchronously from each pedal ganglion. The putative command to swim originates within the cerebral ganglia.

Weight loss following LH lesions independent of changes in motor activity or metabolic rate.

Lesions in the lateral hypothalamus (LH) which resulted in aphagia and a significant loss in body weight, did not reduce either the running wheel activity or the stabilimeter activity of the animals. Following recovery, the animals failed to regain the lost weight. They had normal food and water intakes under ad lib conditions, and ate food when water deprived. They did not drink when deprived of food. Both control and LH animals also had higher than normal oxygen consumption rates. However, the LH group was not higher than the controls postoperatively. These data argue against their being a unitary LH lesion syndrome and suggest that the chronic weight loss seen in animals with LH lesions is not a secondary consequence either of having disrupted the pituitary-thyroid axis, or of having changed the animals' spontaneous activity levels.