Acute effects of donepezil in healthy young adults underline the fractionation of executive functioning.

The cholinergic system is involved in the modulation of both bottom-up and top-down attentional control. Top-down attention engages multiple executive control processes, but few studies have investigated whether all or selective elements of executive functions are modulated by the cholinergic system. To investigate the acute effects of the pro-cholinergic donepezil in young, healthy volunteers on distinct components of executive functions we conducted a double-blind, placebo-controlled, independent-groups design study including 42 young healthy male participants who were randomly assigned to one of three oral treatments: glucose (placebo), donepezil 5 mg or donepezil 7.5 mg. The test battery included measures of different executive components (shifting, updating, inhibition, dual-task performance, planning, access to long-term memory), tasks that evaluated arousal/vigilance/visuomotor performance, as well as functioning of working memory subsidiary systems. Donepezil improved sustained attention, reaction times, dual-task performance and the executive component of digit span. The positive effects in these executive tasks did not correlate with arousal/visuomotor/vigilance measures. Among the various executive domains investigated donepezil selectively increased dual-task performance in a manner that could not be ascribed to improvement in arousal/vigilance/visuomotor performance nor working memory slave systems. Other executive tasks that rely heavily on visuospatial processing may also be modulated by the cholinergic system.

Effects of lorazepam on visual perceptual abilities.

OBJECTIVE: To evaluate the effects of an acute dose of the benzodiazepine (BZ) lorazepam in young healthy volunteers on five distinguishable visual perception abilities determined by previous factor-analytic studies. METHODS: This was a double-blind, cross-over design study of acute oral doses of lorazepam (2 mg) and placebo in young healthy volunteers. We focused on a set of paper-and-pencil tests of visual perceptual abilities that load on five correlated but distinguishable factors (Spatial Visualization, Spatial Relations, Perceptual Speed, Closure Speed, and Closure Flexibility). Some other tests (DSST, immediate and delayed recall of prose; measures of subjective mood alterations) were used to control for the classic BZ-induced effects. RESULTS: Lorazepam impaired performance in the DSST and delayed recall of prose, increased subjective sedation and impaired tasks of all abilities except Spatial Visualization and Closure Speed. Only impairment in Perceptual Speed (Identical Pictures task) and delayed recall of prose were not explained by sedation. CONCLUSION: Acute administration of lorazepam, in a dose that impaired episodic memory, selectively affected different visual perceptual abilities before and after controlling for sedation. Central executive demands and sedation did not account for results, so impairment in the Identical Pictures task may be attributed to lorazepam's visual processing alterations.

Effects of lorazepam on deductive reasoning.

RATIONALE: Benzodiazepines slow reasoning performance, but it is still unknown which phase of reasoning is affected and whether this effect is present for different types of relations between entities in reasoning problems. OBJECTIVES: We investigated which phases of deductive reasoning are affected by lorazepam and whether this effect varies according to the type of relations in deductive reasoning problems. METHODS: This was a double-blind, crossover design study of acute oral doses of lorazepam (2 mg) and placebo, using young healthy volunteers. We focused on response delay of three separable phases of deductive reasoning and matched working memory tasks (that involved only maintenance of information) the premise processing phase, the premise integration phase, and the validation phase, in which reasoners decide whether a conclusion logically follows from the premises (reasoning task) or is identical to one of the premises (maintenance task). Type of relations in the premises was also manipulated. We employed material that was difficult to envisage visually and visuospatially ("subiconic") and material easy to envisage visually or visuospatially. RESULTS: Lorazepam slowed response as memory load increased, irrespective of type of relations. It also specifically slowed validation in reasoning problems with visual relations, an effect that disappeared after subtraction of maintenance scores, and increased validation time in problems with subiconic relations, which remained after this subtraction. CONCLUSION: Acute lorazepam administration affected reasoning in two ways: it slowed processing nonspecifically when working memory demands increased and augmented validation time depending on the difficulty in generating and/or manipulating mental representations by the central executive.

Effects of auditory stimuli on intracranial pressure and cerebral perfusion pressure in traumatic brain injury.

The primary goal of medical and nursing management in the traumatic brain-injured patient is to decrease intracranial pressure (ICP) and maintain adequate cerebral perfusion pressure (CPP). Little is known about what effect, if any, auditory stimulation has on these parameters. Therefore, an experimental study was conducted to examine the effects of various auditory stimuli on intracranial pressure (ICP) and cerebral perfusion pressure (CPP) in traumatic brain-injured patients. A convenience sample of fifteen participants with admitting Glasgow Coma Scale scores between 3 and 8 was studied. Three types of auditory stimuli: earplugs, a music tape and a tape of ICU environmental noise were applied to patients in a computer-generated random order. The tapes delivered sound at 70 decibels. Each intervention lasted 15 minutes. ICP and CPP were recorded at a 30 second resolution time through a bedside computer. Data were analyzed using analysis of variance for a cross over design. Results showed no statistically significant change in ICP or CPP during the study period. Further studies are needed to examine the effects of auditory stimuli on ICP and CPP in traumatic brain-injured patients.

Opportunities and constraints: black-white differences in the formation of interracial friendships.

In this article, we examine the effects of classroom characteristics on the interracial friendliness of students in desegregated classrooms. We argue that social psychological processes that affect cross-race sociability are set in motion by the classroom climate, the organization of instruction, and the class racial composition. The effects of these variables on the likelihood of cross-race friendships are observed in longitudinal data from 455 students in 16 fourth- through seventh-grade desegregated classrooms. The results show that classroom characteristics associated with "status-leveling" effects operate differently for black and white students. Ability grouping influences the interracial sociability of white students more than that of blacks, while the academic status of peers affects the cross-race friendships of blacks more than of whites. Race differences in the effects of classroom climate on interracial friendships are also observed.