Lack of the metabotropic glutamate receptor subtype 7 selectively modulates Theta rhythm and working memory

Metabotropic glutamate receptors (mGluRs) are known to play a role in synaptic plasticity and learning. We have previously shown that mGluR7 deletion in mice produces a selective working memory (WM) impairment, while other types of memory such as reference memory remain unaffected. Since WM has been associated with Theta activity (6-12 Hz) in EEGs, and since EEG abnormalities have been observed in these mice before, we studied the effect of mGluR7 gene ablation on EEG activity in the hippocampus, in particular in the Theta range, during performance of a WM task. In an eight-arm maze with four arms baited, mGluR7 knock-out (KO) and wild-type mice committed the same number of reference memory errors, whereas KOs committed more WM errors. While performing the task, KO mice showed substantially higher Theta amplitudes, and the ratio of Theta to overall EEG power was much increased. No change was seen in the Delta (0-5 Hz), or Gamma (30-40 Hz) EEG bands compared with controls. When recording EEGs during periods of rest in the home cages, no difference was seen between groups. These findings suggest that mGluR7 is important for modulation and control of Theta activity. Since only WM was affected, and only the Theta range of EEG activity was altered, these results show a correlation between Theta rhythm and WM performance, and therefore support the concept that Theta activity in the hippocampus is involved in WM storage.     

When is the ball going to hit the ground? Duration estimates, eye movements, and mental imagery of object motion

Performance in 2 versions of a computer-animated task was compared. Participants either indicated the time of arrival of a target that rolled off a horizontal surface and fell--hidden from view--onto a landing point (production task) or judged flight time on a rating scale (judgment task). As predicted, performance was significantly better in the production task (Experiment 1), in which imagery of object motion probably replaced reasoning processes. Participants who exhibited eye movements suggesting mental tracking performed particularly well in the production task (Experiment 2). There was, however, no decrement in performance when participants were asked to fixate the point where the target disappeared. For motion duration estimations, eye movements seem to be only a by-product of mental tracking.     

Auditory,visual, and cross-modal negative priming

Auditory, visual, and cross-modal negative priming was investigated using a task in which participants judged whether stimuli were animals or musical instruments. Negative priming was observed, but only if the attended and the ignored primes evoked different responses. This pattern—negative priming after conflict, but not after nonconflict, primes—was demonstrated with visual stimuli and replicated with auditory stimuli, as well as across modalities, both auditory to visual and visual to auditory. Implications for theories of negative priming are discussed.     

The Influence of Indirect Knowledge of Previous Performance on Ratings of Present Performance: The Effects of Job Familiarity and Rater Training

In a 2 × 2 × 2 crossed factorial design, trained or untrained subjects viewed a videotape and evaluated performance on either a familiar (college lecturer) or unfamiliar (salesperson) job. Prior to viewing the videotape, some subjects reviewed positive information about the ratee's prior performance, whereas other subjects did not review any prior performance information. To determine whether assimilation or contrast effects occurred, we compared ratings provided by subjects who reviewed positive information about prior performance with ratings provided by subjects who did not review any prior performance information. A three-way interaction was obtained. Ratings of performance on the familiar job by untrained or trained subjects revealed only a small assimilation effect. However, when rating performance on the unfamiliar job, a large assimilation effect was observed among untrained subjects, whereas a large contrast effect was observed among trained subjects. The results indicate that rater error training may reverse, rather than reduce or eliminate, rating errors that arise from knowledge of a ratee's prior performance. Implications for further understanding and reducing assimilation and contrast effects are discussed.     

The effect of affirmative action on attributions about minority group members

In the first study subjects were given information about an applicant to graduate school and asked to rate his qualifications. The information experimentally varied (a) whether the school had an affirmative action policy, (b) the ethnicity of the applicant, and (c) whether the applicant was accepted or rejected. Based on Kelley's discussion of the discounting and augmentation principles, it was predicted that the minority applicant would be rated as less qualified when the university was committed to an affirmative action program. The reverse pattern was predicted for the non-minority applicant. The results supported the first prediction but not the second. Experiment 2 was designed to eliminate alternative interpretations of the data and the same results were found. Possible interpretations for the failure of affirmative action in affecting the ratings of nonminority applicants are discussed.     

Social problem-solving skills in boys with conduct and oppositional defiant disorders

The current study compared the social problem-solving skills of a clinic-based sample of 30 boys diagnosed with conduct disorder (CD) and 25 boys diagnosed with oppositional defiant disorder (ODD). Past research has indicated that contextual factors influence children's social problem-solving; thus, three hypothetical conflict situations (i.e., child-child, teacher-child, and parent-child) and situations which differed by degree of negative intent of the provocateur (i.e., hostile vs. Ambiguous intent) were examined. Problem-solving strategies were aggregated into three broad dimensions: 1) aggressive/antisocial solutions; 2) nonverbal-nonaggressive solutions; and 3) verbal-nonaggressive solutions. Compared to ODD boys, CD boys proposed more aggressive/antisocial solutions in parent-child conflicts when parental intent was ambiguous and in teacher-child conflicts regardless of intent. Compared to ODD boys, CD boys proposed fewer verbal-nonaggressive solutions in child-child conflicts. The implications of these findings for treatment intervention with CD and ODD boys were discussed. Aggr. Behav. 23:457–469, 1997. © 1997 Wiley-Liss, Inc.     

The challenge of merging: merger patterns, premerger status, and merger support

Employees of merging organizations often show resistance to the merger. The employees' support depends on the companies' premerger status and on the merger pattern. Based on an intergroup perspective, three studies were conducted to investigate the influence of premerger status (high, low) and merger pattern (assimilation, integration-equality, integration-proportionality, transformation) on participants' support for a pending organizational merger. Students (Study 1) and employees (Study 2) had to take the perspective of employees of a fictitious merging organization. Study 3 investigated students' perceptions of a potentially pending university merger using a 2 (status) x 3 (merger pattern: assimilation, integration-equality, integration-proportionality) design. Across all studies, the low-status group favored integration-equality and transformation whereas the high-status group preferred integration-proportionality and assimilation. Perceived threat mediated the effects. Legitimacy was a stronger mediator for effects of the low-status group.     

Speech perception deficits in Parkinson's disease: underestimation of time intervals compromises identification of durational phonetic contrasts

Besides motor, vegetative, and cognitive signs, patients suffering from Parkinson's disease (PD) may show distinct perceptual deficits such as underestimation of time intervals extending across several seconds. Assuming this impairment also to affect the domain of tens of milliseconds, disrupted encoding of the acoustic speech signal with respect to segment durations conveying linguistic information must be expected. To test this hypothesis, 10 PD patients and matched controls performed an identification task using a series of 10 stimuli derived from the utterance "Boten" (/bo:tn/, 'messengers'; produced with nasal plosion) by exclusive manipulation of occlusion length (110-20 ms in steps of 10 ms). Under these conditions, word-medial silence cues the voicing category of the respective stop consonant. Seven PD subjects showed normal identification curves, i.e., categorized the shortest and longest stimuli with high probability each as the minimal pair cognates "Boden" and "Boten," respectively. In contrast, the remaining three patients labeled all items across the complete range of occlusion lengths as "Boden." A subsequent experiment found a horizontal shift of the identification curves toward larger signal durations (> 120 ms) in these three subjects. Bilateral cerebellar degeneration has been found to yield a different response pattern, i.e., near-chance level of performance. Considering recent information-processing models of scalar interval timing, striatal disorders seem to slow down an oscillatory pacemaker, whereas cerebellar dysfunctions may impair comparison of measured durations with stored reference memory traces.