Background: Despite the acknowledged importance of environmental risk factors in the etiology of narcolepsy, there is little research on this topic. This study sought to fill this gap in the literature and assess the risk of stressors and infectious diseases using a case-control study. Methods: Cases (n = 63) were recruited through the Stanford Center for Narcolepsy. All were HLA-DQB1*0602 positive, met conventional Multiple Sleep Latency Test criteria, and reported unambiguous cataplexy. Controls (n = 63) were nonrelated family members of cases and local community members. A self-administered questionnaire was used to assess the frequency and timing of possible risk factors. Results: Of the infectious diseases examined, only flu infections and unexplained fevers carried a significant risk. Several of the stressors carried a significant risk including a major change in sleeping habits. When the timing of all risk factors was considered, exposure prior to puberty increased the risk for developing narcolepsy. Conclusions: These findings emphasize the importance of environmental risk factors in the etiology of narcolepsy. This highlights the need for further research on this aspect of narcolepsy so a complete understanding of a disorder that affects 1 in 2,000 individuals can emerge.

A number of studies have employed a delayed matchingto-sample procedure to investigate memory for event duration and memory for number of events in pigeons. In a typical experiment on memory for event duration, trials begin with the presentation of a continuous signal (e.g., the overhead houselight) for either a short (e.g., 2 sec) or a long (e.g., 8 sec) duration. Termination of the sample is followed immediately by the presentation of two comparison stimuli. A peck to one comparison stimulus (e.g., red) is reinforced if the sample duration was short, whereas a peck to the other comparison stimulus (e.g., green) is reinforced if the sample duration was long. Following acquisition, memory for time is assessed by inserting delay intervals of varying length between the termination of the sample and the onset of the comparisons. Previous research has shown that at delays longer than baseline training, pigeons continue to respond with high accuracy following the short-duration sample, whereas accuracy of responding to the long-duration sample drops to well below 50% correct (Fetterman, 1995;Gaitan & Wixted, 2000;Grant, 1993;Kelly & Spetch, 2000;Kraemer, Mazmanian, & Roberts, 1985;Santi, Bridson, & Ducharme, 1993;Santi, Ducharme, & Bridson, 1992;Sherburne, Zentall, & Kaiser, 1998;Spetch, 1987;Spetch & Rusak, 1989Spetch & Wilkie, 1983). This result is commonly known as the choose-short effect, because pigeons show a bias to peck the comparison stimulus that is correct for the shortduration sample as the delay interval is extended beyond that used in training.Similar experiments have been conducted to assess memory for number of events in pigeons. In this case, the sample stimulus consists of a small number or a large number of equally spaced light flashes, each lasting 200 msec. For example, the small sample would consist of two flashes of light in 4 sec (2f/4sec), whereas the large sample would consist of eight flashes of light in 4 sec (8f/4sec). A peck to one comparison stimulus (e.g., red) is reinforced if the sample number was small, whereas a peck to the other comparison stimulus (e.g., green) is reinforced if the sample number was large. Roberts, Macuda, and Brodbeck (1995) used this type of procedure and found that, during delay testing, pigeons continued to respond with high accuracy following the samples consisting of a small number of light flashes (2f/4sec), whereas the accuracy of responding following the large number (8f/4sec) dropped to well below 50% correct. Fetterman (2000) reported a similar finding with rates of stimulus change (slow vs. fast) serving as sample stimuli. Delay tests indicated a bias to respond to the comparison alternative associated with the slow sample. Fetterman (2000) hypothesized that rate discriminations were based on the number of sample events (light flashes) and that the choose-slow bias represented an instance of a choosesmall effect. Thus, memory for number reveals a choosesmall effect, just as memory for time reveals a chooseshort effect. This research was supported by...

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