Three adult subjects were taught the following two-sample, two-comparison conditional discriminations (each sample is shown with its positive and negative comparison, in that order): A1-B1B2, A2-B2B1; B1-C1C2, B2-C2C1; and C1-D1D2, C2-D2D1. A teaching procedure was designed to encourage control by negative comparisons. Subjects were then tested for emergent performances that would indicate whether the baseline conditional discriminations were reflexive, symmetric, and transitive. The tests documented the emergence of two classes of equivalent stimuli: A1, B2, C1, D2 and A2, B1, C2, D1. These were the classes to be expected if the negative comparisons were the controlling comparisons in the baseline conditional discriminations. The negative comparisons, however, were not the comparisons that subjects were recorded as having chosen in the baseline conditional discriminations. Differential test results confirmed predictions arising from a stimulus-control analysis: In reflexivity tests (AA, BB, CC, DD), subjects chose comparisons that differed from the sample; one-node transitivity (AC, BD) and "equivalence" (CA, DB) tests also yielded results that were the opposite of those to be expected from control by positive comparisons; symmetry tests (BA, CB, DC), two-node transitivity (AD) tests, and two-node "equivalence" (DA) tests yielded results that were to be expected from control by either positive or negative comparisons.

Many students have sleep problems that may interfere with daily performance, such as driving and academics. Circadian rhythm management, sleep hygiene, and white noise could ameliorate sleep difficulties.

Male albino rats were tested both pre-and postoperatively either on a schedule of differential reinforcement of low-rate responding (DEL 20 sec; Experiment 1) or for spontaneous alternation (Experiment 2). Selective lesions were produced in the hippocampus and its fiber connections. Performance of both behaviors was consistently disrupted by total fornix, medial fornix, and septum lesions, while neither behavior was significantly disrupted by postcommissural fornix or entorhinal cortex lesions. Anterior hippocampus lesions consistently disrupted only DRL performance, while neither posterior hippocampus nor lateral fornix lesions resulted in consistently impaired performance of either behavior. These data are discussed as representing a possible functional differentiation between anterior and posterior portions of the hippocampal system.

The neuropsychological performance of 119 patients with severe closed traumatic brain injury (TBI) who had received toxicology screens at the time of trauma centre admission was examined. Three groups were created: normal screen, positive alcohol screen, or positive abused drugs screen (with or without the presence of alcohol). The admitting Glasgow Coma Scale (GCS) score was significantly lower in the positive alcohol screen group than the normal screen group, while the three groups did not differ in length of post-traumatic amnesia (PTA) or years of education. Neuropsychological assessment was conducted during inpatient rehabilitation, following resolution of PTA. Normal screen patients obtained significantly better scores than the abused-drugs patients on the Full Scale IQ (FIQ) and Verbal IQ (VIQ) indices of the Wechsler Adult Intelligence Scale-Revised and the Verbal Memory, General Memory, Attention-Concentration, and Delayed Recall indices of the Wechsler Memory Scale-Revised. Normal screen patients also scored significantly higher than positive alcohol screen patients on FIQ and VIQ indices and all five indices from the Wechsler Memory Scale-Revised. These data suggest the existence of an additive effect of substance abuse on neuropsychological outcome in TBI. Findings have potential implications for both acute management and rehabilitation of TBI.

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