Temporal kinetics of prefrontal modulation of the extrastriate cortex during visual attention

Single-unit, event-related potential (ERP), and neuroimaging studies have implicated the prefrontal cortex (PFC) in top-down control of attention and working memory. We conducted an experiment in patients with unilateral PFC damage (n=8) to assess the temporal kinetics of PFC-extrastriate interactions during visual attention. Subjects alternated attention between the left and the right hemifields in successive runs while they detected target stimuli embedded in streams of repetitive task-irrelevant stimuli (standards). The design enabled us to examine tonic (spatial selection) and phasic (feature selection) PFC-extrastriate interactions. PFC damage impaired performance in the visual field contralateral to lesions, as manifested by both larger reaction times and error rates. Assessment of the extrastriate P1 ERP revealed that the PFC exerts a tonic (spatial selection) excitatory input to the ipsilateral extrastriate cortex as early as 100 msec post stimulus delivery. The PFC exerts a second phasic (feature selection) excitatory extrastriate modulation from 180 to 300 msec, as evidenced by reductions in selection negativity after damage. Finally, reductions of the N2 ERP to target stimuli supports the notion that the PFC exerts a third phasic (target selection) signal necessary for successful template matching during postselection analysis of target features. The results provide electrophysiological evidence of three distinct tonic and phasic PFC inputs to the extrastriate cortex in the initial few hundred milliseconds of stimulus processing. Damage to this network appears to underlie the pervasive deficits in attention observed in patients with prefrontal lesions.     

Mild hypoxia disrupts recollection,not familiarity

Yonelinas et al. (2002) found that hypoxic patients exhibited deficits in recollection that left familiarity relatively unaffected. In contrast, Manns, Hopkins, Reed, Kitchener, and Squire (2003) studied a group of hypoxic patients who suffered severe and equivalent deficits in recollection and familiarity. We reexamine those studies and argue that the discrepancy in results is likely due to differences in the hypoxic groups that were tested (i.e., differences in amnestic severity, subject sampling methods, and patient etiology). Yonelinas et al. examined memory in 56 cardiac arrest patients who suffered a brief hypoxic event, whereas Manns et al. examined a group of severely amnesic patients that consisted of 2 cardiac arrest patients, 2 heroin overdose patients, 1 carbon monoxide poisoning patient, and 2 patients with unknown etiologies. We also consider an alternative explanation proposed by Wixted and Squire (2004), who argued that the two patient groups suffered similar deficits, but that statistical or methodological artifacts distorted the results of each of Yonelinas et al.'s experiments. A consideration of those results, however, indicates that such an explanation does not account for the existing data. All of the existing evidence indicates that recollection, but not familiarity, is disrupted in mild hypoxic patients. In more severe cases of hypoxia, or those with more complex etiologies such as heroin overdose, more profound deficits may be observed.     

Raters who pursue different goals give different ratings

J. N. Cleveland and K. R. Murphy (1992) suggested that phenomena such as rater errors and interrater disagreements could be understood in terms of differences in the goals pursued by various raters. We measured 19 rating goals of students at the beginning of a semester, grouped them into scales, and correlated these with teacher evaluations collected at the end of the semester. We found significant multiple correlations, both within classes and in an analysis of the pooled sample (adjusting for instructor mean differences, incremental R2 =.08). Measures of rating goals obtained after raters had observed a significant proportion of ratee performance accounted for variance (incremental R2 =.07) not accounted for by measures of goals obtained at the beginning of the semester.     

A model of childhood perceived peer harassment: analyses of the Canadian National Longitudinal Survey of Children and Youth Data

The authors developed a model of childhood perceived peer harassment, using several personality, peer, and familial characteristics of victims, and tested it with children 10 to 11 years old (N = 3,434) drawn from the Canadian National Survey of Children and Youth, which is a stratified random sample of 22,831 households in Canada. A 3-step analytic procedure with 3 separate subsamples of the children was used to explore psychosocial correlates of peer harassment. Results from the latent variable path analysis (comparative fit index = .90) showed that victims are likely to feel anxious and disliked by their peers. Their parents reported using high levels of control and low levels of warmth with their children and reported high levels of depression and marital conflict themselves. These results are discussed from a social-cognitive perspective.     

Death anxiety and death obsession in Spanish students

This study examined the dimensional structure of Templer's Death Anxiety Scale and Abdel-Khalek's Death Obsession Scale. The responses of 289 Spanish students to the Spanish forms of both scales were evaluated by means of a principal components analysis with varimax rotation. Three significant factors were identified: Death Obsession, Cognitive-Affective, and Death Anxiety. The distribution of the factor loadings for the items of both scales on Factors 1 and 3 supported the discriminant validity of the constructs specific to each of the scales, while Factor 2 showed a common component in both scales characterized by cognitive and affective aspects in relation to the idea of death.     

Co-reference and reasoning

Memory &; Cognition - Co-reference occurs when two or more noun phrases refer to the same individual, as in the following inferential problem: Mark is kneeling by the fire or he is looking at...     

Text cohesion and metacomprehension: Immediate and delayed judgments

In three experiments, we examined comprehension judgments made after a piece of text had been read. We propose that such metacognitive judgments are based on the content of working memory at the exact moment of assessment. Generally speaking, this working metacognition hypothesis is in agreement with Koriat's cue utilization approach, which implies that different elements of information will be available (and used) depending on the moment at which a judgment is made. More specifically, our hypothesis focuses on the management of working memory during reading as a cause for cue (un)availability. In support of these views, the results of Experiment 1 showed that a cohesion manipulation affecting the comprehension of specific paragraphs influences judgments only on these paragraphs, and not on judgments on the whole text. In Experiment 2, we showed that an interfering task that takes place just before this paragraph judgment is made wipes out this cohesion effect. Experiment 3 showed, on the other hand, that the whole-text judgment may, nevertheless, be affected by text cohesion, provided that the readers keep an access to the text when the judgment is made. These results support the idea that working memory management makes different cues available for metacognitive ratings at different delays.     

Anticipatory balance control is affected by loadless training experiences

The main purpose of this study was to identify whether a lot of sports training had any effect on the balance control associated with a leg movement. The nature of the training experience was also an important concern and we chose subject who had undergone specific training experience in absence of equilibrium constraints. To this end a comparison between control (untrained) subjects, triathletes and swimmers was designed to establish whether a general training in sports (triathletes) or a specific loadless training (swimmers), leads to differences in the balance control. A leg movement is preceded by a shift of the center of mass (CM) towards the supporting side to maintain equilibrium and forward to create the condition for progression. To provide an acceleration of the CM sideward and forward, an initial displacement of the center of pressure (CP) towards the moving limb and in posterior direction was performed. Interestingly, the lateral pressure onto the ground was greater increased in swimmers in both leg raising and obstacle avoidance tasks compared to the control group and/or triathletes whereas the backward CP shift in all group was the same. The initial control of the CM shift is very different in swimmers compared to triathletes and controls. The increased lateral pressure onto the ground in swimmers may be a result of a prolonged training in water. This suggests that prolonged training in the absence of equilibrium constraints has more of an effect on balance control than a prolonged general training. In addition, the lack of differences in the backward CP shift suggests that M/L and A/P controls support two functional goals: equilibrium maintenance and movement initiation.