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This study suggests that cigarette smoking can transiently normalize the impairment of auditory sensory gating in schizophrenic patients.

In addition to the numerous heroin users who voluntarily enter methadone treatment as a way to free themselves from illicit drug addiction and those ordered to do so by the courts, there are a large number of opioid users who enter methadone treatment with other objectives in mind. These include shorter-term goals that users do not necessarily equate with complete heroin abstinence. In this paper we report the results of a qualitative study designed to identify and describe the motivations active heroin users have for entering methadone treatment, and to suggest that many of these short-term methadone episodes may operate as self-prescribed attempts at risk reduction, and act as pilot tests for users considering or anticipating entering treatment to quit the use of illicit drugs. We argue that heroin users' motivations, perceptions about methadone, and the strategies they devise for adapting methadone treatment for their own needs should be recognized for their value in reducing the multiple risks associated with drug use.

This project applies agent-based modeling (ABM) techniques to better understand the operation, organization, and structure of a local heroin market. The simulation detailed was developed using data from an 18-month ethnographic case study. The original research, collected in Denver, CO during the 1990s, represents the historic account of users and dealers who operated in the Larimer area heroin market. Working together, the authors studied the behaviors of customers, private dealers, street-sellers, brokers, and the police, reflecting the core elements pertaining to how the market operated. After evaluating the logical consistency between the data and agent behaviors, simulations scaled-up interactions to observe their aggregated outcomes. While the concept and findings from this study remain experimental, these methods represent a novel way in which to understand illicit drug markets and the dynamic adaptations and outcomes they generate. Extensions of this research perspective, as well as its strengths and limitations, are discussed.

The evoked response to repeated auditory stimuli generally decreases in amplitude, a phenomenon that demonstrates the activity of sensory gating mechanisms in the central nervous system (CNS). Gating of the PSO wave of the auditory evoked response shows such behavior in normals, but not in schizophrenic or manic subjects. In mania, diminished gating of the auditory evoked response is correlated with elevated levels of noradrenergic metabolites. In animals, yohimbine, a presynaptic a-2 antagonist, increases noradrenergic neuronal transmission in the CNS and diminished gating of the auditory evoked response. The aim of this

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Inhibitory gating of response to repeated stimuli is demonstrated by several event-related potentials, including the auditory P50 wave. The present study examined the effects of variation in sound intensity on this phenomenon in schizophrenics and normal subjects. Paired clicks, 500 ms apart, were presented 50 dB above threshold to 10 normal subjects and 10 schizophrenics. The normal subjects demonstrated significantly more decrement of response to the second stimulus than did the schizophrenics. When the sounds were noticeably louder(70 dB above threshold), no such difference was observed. Rather, both groups had similarly diminished gating of response. A significant difference between schizophrenics and normal subjects was also observed when the sounds were 30 dB above threshold, but the difference was smaller than that at 50 dB. At any stimulus intensity, concomitant eye movements led to loss of gating of P50 in the normal subjects.

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