Cognitive Neuropsychology of HIV-Associated Neurocognitive Disorders

Advances in the treatment of the human immunodeficiency virus (HIV) have dramatically improved survival rates over the past 10 years, but HIV-associated neurocognitive disorders (HAND) remain highly prevalent and continue to represent a significant public health problem. This review provides an update on the nature, extent, and diagnosis of HAND. Particular emphasis is placed on critically evaluating research within the realm of cognitive neuropsychology that aims to elucidate the component processes of HAND across the domains of executive functions, motor skills, speeded information processing, episodic memory, attention/working memory, language, and visuoperception. In addition to clarifying the cognitive mechanisms of HAND (e.g., impaired cognitive control), the cognitive neuropsychology approach may enhance the ecological validity of neuroAIDS research and inform the development of much needed novel, targeted cognitive and behavioral therapies. The research described was supported by MH73419 and MH62512 from the National Institutes of Health. The views expressed in this article are those of the authors and do not reflect the official policy or position of the Department of the Navy, Department of Defense, nor the United States Government.     

Concurrence costs in double stimulation tasks

Seven experiments are described on reaction time (RT₁) to a first auditory stimulus in a double stimulation paradigm, where the response to a second visual stimulus was explicitly non-speeded. In all studies it was found that, compared to a single stimulus control condition, RT₁ showed a constant delay of about 20–30 msec. The effect occurred irrespective of (a) the viewing conditions of the second stimulus in terms of either duration, processing demands or presence vs absence of a backward masking signal (experiments 1, 4, 5, 6, 7); (b) the duration of the interstimulus interval ranging from -200 msec up to at least a second (experiments 2, 3, 5); and (c) the processing demands of the first task (experiment 7). It is suggested that the delay reflects a basic concurrence cost which remains when two reactions can be time-shared.     

Differences in semantic encoding as a function of reading comprehension skill

Using a modified Stroop procedure, we examined the extent to which the semantic encoding of a word is governed by the context within which that word appears. Good and poor comprehenders named the color of target words following their reading of either sentences or single words representing the object nouns of the sentences. Target words represented contextually emphasized (appropriate) attributes of the object nouns, nonemphasized (inappropriate) attributes of these nouns, or object attributes not related to these nouns (neutral). For single-word contexts, all subjects exhibited equal semantic interference to appropriate and inappropriate targets, relative to neutral targets. For sentence contexts, however, good comprehenders exhibited semantic interference only to appropriate targets, whereas poor comprehenders again exhibited equal interference to appropriate and inappropriate targets. These findings suggest that differences in comprehension skill may be attributable, at least in part, to fundamental differences in the way in which sentences are semantically encoded.     

Measuring medical students' reluctance to prescribe opioids for cancer pain

Among 644 senior medical students a 14-item scale which was internally consistent indicated no change over the 6 years of testing in intent to reserve opioids for terminally ill.     

A longitudinal study of bilingual and cognitive development(1)

This paper presents the findings of a longitudinal study of IQ data collected over a 5-year period (Grades K-4) on pupils enrolled in a French immersion program (anglophone pupils receiving all instruction in French except English language arts) and pupils in the regular English program. Although year-by-year results may fail to show IQ differences between the two groups, repeated measures analysis indicates that the immersion group has a higher IQ measure over the 5-year period. However, considering Grades 1–3 only, which involved the administration of the same test, the two groups do not score differentially with respect to either overall IQ measure or specific subtest scores (classification/categorization, analogies, following of verbal directions) when scores are adjusted for initial IQ (and age) differences, thus failing initially to support studies which show positive relationships between bilingualism and cognitive functioning. However, supportive of those studies is a further analysis on the data of immersion pupils classified as “high” French achievers vs. “low” French achievers. The high French achievers obtain significantly higher IQ measures and subtest scores (analogies and following of verbal directions) than the low French achievers, even when scores are adjusted for initial IQ and age differences. These findings are interpreted in the context of Cummins' (1976) “threshold” hypothesis relating to level of competence in the second language.     

Food and intracranial stimulation responding suppressed with regular-interval shock.

Attenuation of conditioned suppression during intracranial stimulation was compared with that during food reinforcement. Response rates controlled by food and by brain stimulation were equalized on a multiple schedule by adjusting the stimulating current. When foot shock was delivered during timeout periods separating response components, responding for food was significantly more suppressed than responding for brain stimulation. When components were shortened from 10 to 2 minutes, responding maintained by either food or brain stimulation showed a similar temporal pattern of suppression preceding each shock, but responding in the component involving food remained significantly more suppressed. Explanations for the attenuated suppression during brain stimulation based on neural disruption, stimulus blocking, and analgesic properties were questioned. The increased responding during brain stimulation seemed to reflect greater response strength relative to food reinforced responding.     

Large sex difference in adolescents on a timed line judgment task: attentional contributors and task relationship to mathematics

Visuospatial performance, assessed with the new, group-administered Judgment of Line Angle and Position test (JLAP-13), varied with sex and mathematical competence in a group of adolescents. The JLAP-13, a low-level perceptual task, was modeled after a neuropsychological task dependent upon functioning of the posterior region of the right hemisphere [Benton et al, 1994 Contributions to Neuropsychological Assessment: A Clinical Manual (New York: Oxford University Press)]. High-school boys (N = 52) performed better than girls (N = 62), with a large effect for sex (d = 1.11). Performance increased with mathematical competence, but the sex difference did not vary significantly across different levels of mathematics coursework. On the basis of earlier work, it was predicted that male, but not female, performance in line judgment would decline with disruptions to task geometry (page frame), and that the sex difference would disappear with disruptions to geometry. These predictions were supported by a number of univariate and sex-specific analyses, although an omnibus repeated-measures analysis did not detect the predicted interaction, most likely owing to limitations in power. Thus, there is partial support for the notion that attentional predispositions or strategies may contribute to visuospatial sex differences, with males more likely than females to attend to, and rely upon, internal or external representations of task geometry. Additional support for this hypothesis may require development of new measures or experimental manipulations with more powerful geometrical disruptions.     

Conditioned fear extinction and reinstatement in a human fear-potentiated startle paradigm

The purpose of this study was to analyze fear extinction and reinstatement in humans using fear-potentiated startle. Participants were fear conditioned using a simple discrimination procedure with colored lights as the conditioned stimuli (CSs) and an airblast to the throat as the unconditioned stimulus (US). Participants were extinguished 24 h after fear conditioning. Upon presentation of unsignaled USs after extinction, participants displayed significant fear reinstatement. In summary, these procedures produced robust fear-potentiated startle, significant CS+/CS- discrimination, within-session extinction, and significant reinstatement. This is the first demonstration of fear extinction and reinstatement in humans using startle measures.     

Skill training,retention, and transfer: The effects of a concurrent secondary task

In two experiments, we examined training, retention, and transfer of a duration production skill in a prospective paradigm. Participants were trained with feedback and then were either tested immediately for transfer without feedback or retrained with feedback 1 week later. There were three training and retraining conditions, two involving secondary tasks. Retention of the duration production skill was perfect across the 1-week delay when the secondary task condition was unchanged, but there was no skill transfer when that condition was changed. These findings demonstrate specificity of training, with the assumption that the cognitive operations learned during duration production training incorporate requirements of the secondary task. More generally, this study challenges the current practice in which training conditions often do not match eventual testing conditions.