Perirhinal cortex lesions impair context aversion learning

Rats with perirhinal cortex lesions were compared with sham controls on a conditional discrimination in which saccharin was paired with LiCl in context 1, but paired with saline in context 2. Perirhinal-lesioned rats were slightly slower to acquire the discrimination but reached control levels by the end of acquisition. Both groups showed transfer to familiar tap water, consuming less in context 1 than in context 2. Unlike sham rats, perirhinal rats failed to show an aversion to context 1 on a place choice test. These data provide neuroanatomical support for the postulated difference between Pavlovian conditioning and conditional learning.     

Inhibition of return in a selective reaching task: an investigation of reference frames.

Most previous studies of inhibition of return (IOR) have examined reaction time (RT) and accuracy. These effects have been observed via saccades to targets or with key-press responses. In this study the authors examined, for the first time, IOR in components of a selective reaching task in which participants directly reached for and depressed target keys. When the interval between cue and target was 600 ms, robust IOR effects were observed in RT to begin the reach, but no effects were observed in the movement components (movement time to complete the reach and the path of the reach). However, when the cue-target interval was short (200 ms), hand paths deviated toward the cue. The results suggest that although RT measures of IOR appear to reveal perceptual rather than action-based processes, action-based representations may be briefly activated by irrelevant cues, which can be observed via analysis of three-dimensional reach path.     

Adults’ perception of native and nonnative vowels: Implications for the perceptual magnet effect

Two experiments were conducted to evaluate the perceptual magnet effect. In Experiment 1, Amer-ican English speakers representing diverse dialects were presented with a fine-grained set of stimuli (varying in just noticeable differences forF1 andF2) and indicated whether they heard “/i/” or “not /i/,” thus delimiting the /i/ portion of the vowel space for individual subjects. Then these same subjects selected their own /i/ prototype with a method-of-adjustment procedure. The data from this experiment were used to synthesize customized prototype and nonprototype stimulus sets for Experiment 2. In Experiment 2,24 of our original 37 subjects completed a discrimination task for each of three conditions, in which vector stimuli varied from the subject’s prototype, the nonprototype, or a foreign vowel (/y/) in 15-mel steps. Subjects displayed higher discrimination, as indexed byd′, for the nonprototype condition than they did for both the prototype and the foreign conditions. In addition, discrimination was better for variants further away from the referent in each condition. However, discrimination was not especially poor for stimuli close to subjects’ individual prototypes—a result that would have yielded the strongest support for the operation of a magnet effect. This negative finding, together with other aspects of our results, raises problems for any theory of vowel perception that relies solely on “one-size-fits-all” prototype representations.     

Potential Bone-Marrow Donors and Their Spouses: The Effects of Volunteerism on Distress Levels1

The current study sought to provide a better understanding of the reactions of bone-marrow volunteers to the possibility of donating by examining these volunteers in the context of their closest relationships. Using Tesser's (1988) self-evaluation maintenance (SEM) model as a guide, we examined the influence of spouses who are also volunteers on each member of the couple's distress levels and on the marrow volunteer's ambivalence about donating. We also examined the independent effects of known risk factors for donation-related distress and the combined effects of spouse volunteer status and these risk factors on distress levels. Questionnaire data were collected from 278 couples selected from 39 bone-marrow donor centers. Results demonstrated that when spouses of potential donors were engaged in any type of volunteer activity, members of the couple felt greater anxiety than when spouses were not volunteers. Additionally, other variables were found to have a conjoint effect with spouse volunteer status on volunteer and spouse anxiety levels.