On the transmission of partial information: inferences from movement-related brain potentials.

Results are reported from a new paradigm that uses movement-related brain potentials to detect response preparation based on partial information. The paradigm uses a hybrid choice-reaction go/nogo procedure in which decisions about response hand and whether to respond are based on separate stimulus attributes. A lateral asymmetry in the movement-related brain potential was found on nogo trials without overt movement. The direction of this asymmetry depended primarily on the signaled response hand rather than on properties of the stimulus. When the asymmetry first appeared was influenced by the time required to select the signaled hand, and when it began to differ on go and nogo trials was influenced by the time to decide whether to respond. These findings indicate that both stimulus attributes were processed in parallel and that the asymmetry reflected preparation of the response hand that began before the go/nogo decision was completed.     

Automatic and attentional priming in young and older adults: reevaluation of the two-process model.

Three experiments addressed the distinction between automatic and attentional mechanisms underlying semantic priming effects by factorially crossing prime-target relatedness, expectancy, and SOA in a task (pronunciation) that minimized postlexical checking processes. Also, possible age-related (young vs. older adults) differences in the automatic and attentional mechanisms were addressed. Across all experiments there was evidence of a Relatedness x Expectancy x SOA interaction, which is inconsistent with the notion of independent automatic and attentional mechanisms in semantic priming and the notion of a self-encapsulated modular lexicon. The results also indicated age-related differences in the build-up of the expectancy effect across SOAs when the prime was visually available for only 200 ms, independently of the prime-target SOA (Experiments 1 and 3), but not when the prime was visually available throughout the SOA (Experiment 2).     

The usefulness of the Western Aphasia Battery for differential diagnosis of Alzheimer dementia and focal stroke syndromes: preliminary evidence.

We assessed the usefulness of the Western Aphasia Battery for distinguishing the language disturbances caused by Alzheimer dementia (AD) from those caused by stroke. Using discriminant function analyses, the multiple variable "aphasia quotient--reading quotient--writing quotient" classified 29 (72.5%) of the 40 patients correctly. These 29 patients included 8 of 10 patients with left hemisphere infarction and fluent aphasia; 6 of 10 with AD; 5 of 10 patients with right hemisphere infarction; and all 10 of the neurologically normal control subjects. The patients with AD and those with right hemisphere stroke were the most difficult to classify using the aphasia battery.     

Parenting stress among families of children with attention deficit hyperactivity disorder

Prior research has shown that parenting stress levels can be quite high among families of children with attention deficit hyperactivity disorder (ADHD). This study investigated the degree to which such stress was related not only to the child's ADHD, but also to various other child, parent, and family-environment circumstances. Multimethod assessments were conducted on 104 clinic-referred children with ADHD. Data collected from these subjects were entered into hierarchical multiple-regression analyses, utilizing the Parenting Stress Index as the criterion. The results showed that child and parent characteristics accounted for a substantial portion of the variance in overall parenting stress. The child's oppositional-defiant behavior and maternal psychopathology were especially potent predictors. The severity of the child's ADHD, the child's health status, and maternal health status also emerged as significant predictors. These findings are discussed in terms of their impact upon the clinical management of children with ADHD.The authors are grateful to Mary Maher and Paula Nevins for their assistance in collecting and coding the data. The authors would also like to thank Dr. Kenneth Fletcher for his helpful comments regarding the statistical analyses.     

Narrative discourse after closed head injury in children and adolescents.

This study examined narrative discourse in 20 children and adolescents at least 1 year after sustaining a head injury. Narratives were analyzed along the dimensions of language structure, information structure, and flow of information. Severity of impaired consciousness was associated with a significant reduction in the amount of language and information. The most important finding which emerged was the disruption in information structure. This pattern confirms the impression of disorganized discourse in severely injured children. Explanations for the disruption in information structure are explored in terms of the role of vocabulary, memory, and localization of lesion according to magnetic resonance imaging. In view of recent evidence that frontal lobe damage is associated with discourse formulation deficits in adults and is the most common site of focal lesion in closed head injury, we examined discourse patterns in individual patients with frontal lobe lesions. Preliminary data from our single-case studies suggest discourse patterns similar to those reported for adults with frontal lobe injuries.     

Single and combined effects of methylphenidate and behavior therapy on the classroom performance of children with attention-deficit hyperactivity disorder

Twenty-four boys with attention deficit-hyperactivity disorder (ADHD) participating in an intensive summer treatment program each received b.i.d. placebo and two doses of methylphenidate (MPH, 0.3 mg/kg and 0.6 mg/kg) crossed with two classroom settings: a behavior modification classroom including a token economy system, time out and daily home report card, and a regular classroom setting not using these procedures. Dependent variables included classroom observations of on-task and disruptive behavior, academic work completion and accuracy, and daily self-ratings of performance. Both MPH and behavior modification alone significantly improved children's classroom behavior, but only MPH improved children's academic productivity and accuracy. Singly, behavior therapy and 0.3 mg/kg PMH produced roughly equivalent improvements in classroom behavior. Further, the combination of behavior therapy and 0.3 mg/kg MPH resulted in maximal behavioral improvements, which were nearly identical to those obtained with 0.6 mg/kg MPH alone.The authors gratefully acknowledge the assistance of Patricia Donovan, Michelle Berry, Mary Ingram, Patricia Wells, Beth Gnagy, Karen Greenslade, Mary Hamilton, and the entire staff of the Western Psychiatric Institute and Clinic ADHD Summer Treatment Program.     

Effects of aging on the diurnal pattern of water intake in rats.

This study was undertaken to confirm previous findings that Long-Evans rats exhibit age-related changes in the diurnal/nocturnal distribution of water intake and to examine the circadian pattern of these age-related changes. Twenty-one aged and 10 young pathogen-free rats were continuously monitored for water consumption over 12:12 h light/dark cycles. ANOVA, profile analysis, and cosinor analysis each demonstrated that aged rats differed from young rats. The age-related changes in circadian pattern can be described as a blunted rhythm (decreased amplitude) and an altered timing of peak activity (advanced acrophase). These differences, however, were only apparent in a subset of aged rats with the remaining aged rats exhibiting a circadian pattern indistinguishable from that of the young group.     

Nifedipine blocks retention of a visual discrimination task in chicks.

Reports that the dihydropyridine Ca2+ channel antagonists may facilitate memory led to the present study of the behavioral effects of nifedipine. Ninety-two 4-day-old male chicks received 0, 100 nM, 100 microM, or 10 mM nifedipine. Drugs were administered in volumes of 2 microliters into the fourth cerebral ventricle 5 min before training on a visual discrimination task. Nifedipine did not produce any detectable changes in behavior during acquisition trials. Retention, however, was impaired 24 h after training in the 100 nM and 100 microM nifedipine-treated chicks, which made significantly more errors than controls. Nifedipine did not affect the amount of time required to complete the task. No effects on body weight gain were detected, suggesting that the memory impairment was not due to a change in feeding behavior. These data are discussed in terms of the role of calcium-dependent processes in memory.     

General slowing alone cannot explain age-related search effects: reply to Cerella (1991)

Cerella (1991) has argued that the performance of older adults in the Fisk and Rogers (1991) study is a linear function of the performance of younger adults that is independent of task-specific cognitive requirements. We demonstrate that this is not the case. First, we show that the scatter plot analyses used by Cerella can hide the very task-specific age-related slowing they were designed to reveal. Second, we demonstrate that the percentage of variance explained by such analyses can be misleading. Third, we show that there are reliable differences across tasks in the parameters relating younger and older adults' performance. Finally, we argue that the general, task-independent proportionate slowing that Cerella suggested explains so much of the variance in age-related performance is actually an average slowing that is a function of a relatively small task-independent and a relatively large task-dependent factor.     

Impairment of spontaneous alternation performance by an NMDA antagonist: attenuation with non-NMDA treatments.

N-Methyl-D-aspartate (NMDA) receptor antagonists disrupt learning on a variety of tasks. Previous findings indicate that glucose, naloxone, and physostigmine ameliorate learning deficits produced by several treatments. The present experiment examines whether these agents also reverse the amnestic effects of NMDA receptor blockade. Mice were tested for spontaneous alternation performance in a Y-maze. The animals received either saline or the NMDA antagonist, NPC 12626 (35 mg/kg, IP), 50 min prior to testing and received an additional injection of saline, glucose, naloxone, or physostigmine 30 min prior to testing. NPC 12626 significantly decreased alternation scores. Glucose (250 mg/kg), physostigmine (0.01 mg/kg), and naloxone (1 mg/kg) reversed the effects of NPC 12626. Thus, impairments of learning after NMDA receptor blockade share with other amnestic conditions the susceptibility to attenuation by glucose, naloxone, and physostigmine.