Conditioned Inhibition Produced by Extinction of a Conditioned Stimulus

Four experiments used a conditioned taste aversion procedure to examine the potential for CS-alone extinction treatment to produce a conditioned stimulus that possesses inhibitory properties. In Experiment 1, saccharin was paired with LiCl, and then saccharin was presented alone for several trials to produce extensive behavioral extinction. Animals receiving this treatment were retarded in reacquiring conditioned responding to saccharin relative to control subjects receiving conditioning to the flavor for the first time. In Experiment 2, the extinguished saccharin stimulus was shown to decrease conditioned responding to a known excitor when the two stimuli were presented in compound as a summation test. Experiments 3A and 3B replicated the findings of Experiments 1 and 2 while providing evidence that the effects were not due to the differential effects of neophobia during testing. These three experiments revealed that an extinguished conditioned excitor passes retardation and summation tests for conditioned inhibition. Experiment 4 found that extinction of a known excitor was slowed when the excitor was extinguished in compound with a previously extinguished conditioned stimulus. That is, an extinguished CS provided protection from extinction to another CS, a finding also consistent with the view that extinction produces conditioned inhibition.     

Is Speech Arrest during Wada Testing a Valid Method for Determining Hemispheric Representation of Language?

Background and objective: The intracarotid amobarbital procedure, or Wada test, is the method of choice to determine hemispheric representation of language, and is routinely used in the presurgical evaluation for intractable epilepsy. Some investigators perform comprehensive language assessments, but others base language lateralization solely on speech arrest. This study sought to determine whether speech arrest alone during Wada testing provides valid data regarding language lateralization. Methods: The subjects (previously reported) were 21 patients evaluated for intractable epilepsy, who underwent language lateralization by Wada testing and functional MRI (FMRI). For each patient, language representation was determined by calculating: (1) a Wada laterality index based exclusively on speech arrest; (2) a Wada laterality index based on comprehensive language assessment; and (3) an FMRI laterality quotient. Correlation coefficients and categorical classifications were analyzed. Results: There was no significant correlation between the Wada laterality quotient derived from duration of speech arrest and either the comprehensive Wada language laterality score (r= .35,p= .12) or FMRI language laterality score (r= .32,p= .16). Categorical classification as left, right or bilateral language also showed marked discordance between speech arrest and the other two methods. Conclusion: Duration of speech arrest during Wada testing is not a valid measure of language dominance.     

Culturally Sensitive AIDS Educational Videos for African American Audiences: Effects of Source, Message, Receiver, and Context

The importance of using culturally sensitive educational materials in HIV-related interventions with racial and ethnic minority groups is widely recognized. However, little empirical research has been conducted to assess the relative effectiveness of different techniques for creating culturally sensitive AIDS educational videos. Two field experiments with three samples of African American adults (N = 174, 173, and 143) were conducted to assess how source characteristics (race of communicator), message characteristics (multicultural message vs. culturally specific message), and audience characteristics (racial distrust and AIDS-related distrust) influence proximate (perceptions of the message's credibility and attractiveness) and distal (AIDS-related attitudes, beliefs, and behavioral intentions) output variables for AIDS educational videos. In Study 1, an AIDS video with a culturally specific message was rated as more credible, more attractive, and of higher quality than was a video with a multicultural message. The multicultural message was rated less favorably when delivered by a White announcer than when the announcer was Black. In Study 2, the same pattern was replicated with a second community sample and a campus-based sample. Study 2 also indicated that a multicultural message might be more effective if delivered in a culturally specific context, namely, after audience members watch a culturally specific video. Minimal changes were observed in distal outcome variables. It is argued that influencing proximate output variables is necessary, though not sufficient, for effecting long-term change in AIDS-related attitudes, beliefs, and behaviors.     

When are supercomputers worth the bother?

The availability of the UNIX operating system on large supercomputers has greatly simplified the importation of research software from workstations and minicomputers. Supercomputers generally offer much greater memory and storage than do smaller machines, which may make their use mandatory for some large applications. Realization of the full performance offered by vectorizing supercomputers such as the Cray C90 sometimes requires modification of existing code. The use of high-level interpreters for the development of applications is recommended, to minimize the amount of compiled code that must be optimized.     

The φ-maze: A versatile automated T-maze for learning and memory experiments in the rat

The φ-maze is a novel implementation of the T-maze that can be used for various behavioral experiments. It consists of a start/goalbox from which a central alley leads to a choice point. Left and right arms return to the start/goalbox, where reinforcers are delivered. A holding chamber at the choice point can be used for delayed (non)matching-to-sample experiments. Lamps mounted under the translucent acrylic floor serve as visual stimuli. The design incorporates reliable and inexpensive automated guillotine doors and a modification of a commercially available pellet dispenser that allows the automated dispensing of Froot Loop reinforcers. The φ-maze has been used successfully in experiments involving spatial and visual alternation, visual discrimination, and delayed matching-to-sample.     

Circadian factors during sustained performance: Background and methodology

Cornell University Medical College, Westchester Division, The New York Hospital, White Plains, New York It is well established that there is a complex timekeeping mechanism in the human brain. This mechanism is associated with a variety of physiological and psychological rhythms having a period of about a day, and thus referred to as circadian rhythms. The circadian system has recently been modeled in terms of two underlying oscillators, one much more resistant to changes in routine than the other. These oscillators are considered to be endogenous, that is, internal to the organism, and not reliant for their existence upon changes in the person’s environment or general behavior. They thus continue to run even when the sleep/wake cycle is suspended, as in sustained operations. Thus, by their very nature, sustained operations require the individual to override the inputs that are coming from his or her circadian system (especially the indication that sleep is required). The aim of this paper is to provide a background to the area of circadian rhythms research, including a section on the methodology, so that the impact of the circadian system on sustained operations can be better understood.