Nerve root enhancement of the cauda equina occurs in Guillain-Barré syndrome (GBS), but the frequency, diagnostic value, and meaning of this finding is unknown. We prospectively obtained gadolinium-enhanced lumbosacral spine MRIs in 24 consecutive patients with acute GBS and blindly rated nerve root enhancement as absent, mild, or prominent. The MRIs were obtained 13 days, mean, after onset of symptoms (range 2 to 42 days). Twenty of 24 patients had cauda equina nerve root enhancement, which was mild in 6 and prominent in 14. Eighteen of 19 with "typical" GBS had enhancement, compared with 2 of 5 with a variant presentation. Sixty percent of patients with prominent enhancement had severe back or leg pain in contrast to 10% of patients with mild or no enhancement. The GBS disability grade (0 to 5 scale) was higher in patients with prominent enhancement, and significantly fewer patients with prominent nerve root enhancement could walk independently by 2 months. There was no relationship between nerve root enhancement and the timing of the MRI, CSF protein, any of several EMG abnormalities, duration of hospitalization, mean disability grade at 2 months, or the time required for patients to improve to grade 2. In two patients, the EMGs at 11 and 20 days, respectively, were normal except for slightly prolonged F-responses and neurogenic recruitment, but there were prominent nerve root enhancement and an elevated CSF protein. Enhancement of the cauda equina nerve roots with gadolinium on lumbosacral MRI is 83% sensitive of acute GBS and was present in 95% of typical cases. This finding may be useful when electrophysiologic abnormalities are equivocal. In addition, conspicuous nerve root enhancement correlates with pain, GBS disability grade, and duration of recovery.

Quantitative EEG changes were studied during cocaine withdrawal in 36 subjects. All subjects had used cocaine orally (n = 28) or intravenously (n = 8) within 48 h of admission to an inpatient unit. EEGs were recorded 2 and 6 days following admission. Nine subjects returned for a 1-month follow-up EEG. Modal EEG frequency significantly decreased on day 6 compared to day 2. The most dramatic change in both absolute and relative power from day 2 to day 6 was a decrease in the beta2 (18–26 Hz) band. Those subjects who returned for the 4-week follow-up showed a further decrease in beta2 power. Power in the beta2 band was significantly greater for the intravenous users than for the smokers, and the decrease in power from day 2 to day 6 was also significantly greater in this group. While acute effects of cocaine on the EEG have been reported to last only several hours, this study indicates that chronic use may cause longer lasting neuroadaptive changes, particularly in those who have used cocaine intravenously.

The place-preference paradigm was evaluated as a measure of morphine's positive reinforcing properties. Previous place-preference studies obtained a morphine place preference of 26%-63%. In order to examine whether differences in procedure may account for this scatter, the present experiment investigated whether there is any difference in the absolute magnitude of preference when animals are conditioned on their non-preferred side of the box or when animals are randomly assigned to the side of conditioning. Furthermore, the number of conditioning days was extended with 3 intervening test days, and drug doses were doubled following each test day. The results showed no significant difference between conditioning animals on their non-preferred side or randomly assigning them to the side of conditioning. However, by extending the number of conditioning days, as well as by following the drug regimen used, the animals showed a greater magnitude of preference than that observed in previous studies. The implications of these findings for the usage of this paradigm as a measure of morphine's positive reinforcing properties are discussed.

It is common to model inductive datatypes as least fixed points of functors. We show that within the Cedille type theory we can relax functoriality constraints and generically derive an induction principle for Mendler-style lambda-encoded inductive datatypes, which arise as least fixed points of covariant schemes where the morphism lifting is defined only on identities. Additionally, we implement a destructor for these lambda-encodings that runs in constant-time. As a result, we can define lambda-encoded natural numbers with an induction principle and a constant-time predecessor function so that the normal form of a numeral requires only linear space. The paper also includes several more advanced examples.

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