Quantitative and qualitative analyses of clock drawings in Alzheimer's and Huntington's disease.

Although visuoconstructive impairment has been reported in both Alzheimer's (DAT) and Huntington's (HD) disease, there is little knowledge concerning how this cognitive deficit differs quantitatively and qualitatively in these two progressive dementias. To address this issue, the present study compared performances on the Clock Drawing Test (CDT: command and copy) of 25 DAT patients, 25 equally demented HD patients, and 25 elderly normal controls (NC). In the command condition, both patients groups were significantly impaired compared to the NC group. Although there was no significant difference between DAT and HD patients' total quantitative scores, a qualitative error analysis revealed a number of dissociations between the two patient groups. Graphic difficulties, very common in HD patients, were virtually absent in DAT patients; in contrast, conceptual errors were almost exclusively seen in DAT patients and were related to the severity of their dementia. Perseveration and "stimulus-bound" responses were also more frequent in DAT patients, and both groups made visuospatial errors. In the copy condition, the DAT, but not the HD, patients evidenced a marked improvement in performance. These results indicate that while both DAT and HD patients have significant visuoconstructive difficulties even in the early stages of their disorders, the specific cognitive processes underlying their quantitative impairments are quite different. It is possible that the DAT patients' conceptual errors are yet another indicator of the deterioration of their semantic knowledge.     

Discrimination of Facial Identity and Facial Affect by Temporal and Frontal Lobectomy Patients

The purpose of this study was to determine the extent to which lobectomy affects ability to discriminate facial identity or facial expression. Fifteen right temporal, 15 left temporal, 5 right frontal, and 4 left frontal lobectomy patients, pair-matched for age, sex, and education to normal control subjects, participated in this study. Tasks included a Facial Identity Matching Task and a Facial Affect Matching task. The lobectomized patients as a whole were significantly impaired on both tasks (22% decrement in performance). The patients made twice as many errors resulting from perseveration of response-set of the first condition (identity or emotion matching) into the second condition. The site of lobectomy did not influence general performance on any one task or selective performance on any subset of affective categories. It was concluded that all four brain regions play a significant and equal role in face processing, and that circuits more specifically dedicated to visual face processing, which are responsible for hemispheric dominance affects and affect/identity dissociations, are probably located more posteriorly in the brain. Finally, it was concluded that perseveration of acquired habit may, under specific conditions, characterize temporal lobe dysfunction just as much as frontal lobe dysfunction.     

Observing behavior in monkeys (Macaca arctoides): Support for the information hypothesis

A single lever, discrete-trials observing procedure was used with stumptailed monkeys (Macaca arctoides). Lever-presses during a trial produced colored key lights (IS⁺ and IS^?) which signaled whether the trial would end with response-independent food or without food. During the baseline period, both IS⁺ and IS^? were produced on a variable-interval (VI) 15-sec schedule which began operating at the onset of the trial. The two experimental conditions involved a combination of this VI schedule and a DRL schedule. In one of these conditions, only a response that both met the VI requirement and was preceded by at least 6 sec of nonresponding could produce IS^? on nonfood trials, while the schedule for IS⁺ on food trials remained VI 15 sec. In the other experimental condition, the schedules for producing the two stimuli were the reverse. All subjects eventually learned to produce either IS⁺ or IS^? on the combined VI-DRL schedule. These data support an information hypothesis of observing in monkeys and contrast with data from pigeons which support a conditioned reinforcement hypothesis.     

Pattern of intrusions in verbal recall: comparison of Alzheimer's disease, Parkinson's disease, and frontal lobe dementia

Although some researchers have suggested that intrusions in word list learning are more frequent in Alzheimer's disease, recent studies have shown that this might not be true. In fact, intrusions are common in many neurological degenerative diseases. The goal of the present study was to examine the types of intrusions made by three groups of patients, namely patients with Parkinson's disease (PD), Alzheimer's disease (AD), and dementia with prominent frontal lobe semiology (FD). Although PD patients learned more words (trials 1 to 5 on the RAVLT) than the two other groups, there was no significant difference in the total number of intrusions. However, significant differences between groups were observed for nonrelated intrusions, the proportion of PD patients (15.4%) being lower than the proportion of AD (45.5%) and FD (45.8%) patients with this type of intrusions. No other type of intrusions (same category, recurring, phonemic) significantly differentiated between the three groups. The proactive interference effect (PI), measured as the difference between first recall of list A and list B recall, was stronger in PD than in the two other groups, reflecting the strong positive correlation between total number of words recalled on the RAVLT and severity of the PI effect. Prior list intrusions (intrusions from list A while recalling list B items) were significantly more pronounced in FD than in the two other groups. Finally, free associations (series of intrusions related to one another but not to the target items) were observed almost exclusively in FD patients. These findings illustrate some qualitative differences between various neurological degenerative diseases. They also stress the marked similarities between AD and FD with regards to verbal learning.     

Prevalence,and intellectual outcome of unilateral focal cortical brain damage as a function of age,sex and aetiology

Neurologists and neuropsychologists are aware that aging men are more at risk than women for brain damage, principally because of the well known male-predominant risk for cardiovascular disease and related cerebrovascular accidents. However, a disproportion in prevalence of brain damage between the sexes in childhood may be less suspected. Furthermore, sex-specific risk for other aetiologies of brain damage may be little known, whether in the pediatric or adult populations. Proposals of a sex difference in cognitive recovery from brain damage have also been controversial. Six hundred and thirty five "consecutive" cases with cortical focal lesions including cases of all ages and both sexes were reviewed. Aetiology of the lesion was determined for each case as was postlesion IQ. Risk was highly male prevalent in all age groups, with a predominance of cardiovascular aetiology explaining much of the adult male prevalence. However, several other aetiological categories were significantly male prevalent in juveniles (mitotic, traumatic, dysplasic) and adults (mitotic, traumatic). There was no sex difference in outcome (i.e., postlesion IQ) of these cortical brain lesions for the cohort as a whole, after statistical removal of the influence of lesion extent, aetiology and presence of epilepsy. Mechanisms potentially responsible for sex differences in prevalence, aetiology of brain damage, and recovery, are reviewed and discussed.     

Executive Function and Emotional,Behavioral, and Social Competence Problems in Children with Epilepsy

Many researchers have reported elevated rates of emotional, behavioral, and social competence problems (EBSP) in children with epilepsy. Although executive function has been found to be associated with EBSP in children with typical development, almost no research has looked at the individual components of executive function as potential predictors of EBSP in children with epilepsy. This is surprising given the deficits in executive function in children with epilepsy. We investigated EBSP and executive function in 42 children with epilepsy, aged 6.0 to 18.1 years and found, as expected, that EBSP were associated with executive function in these children even after epilepsy-related variables, such as seizure type, were accounted for. However, different components of executive function were related to different emotional, behavioral, and social competence problems in these children. Shifting of mental sets was a significant predictor of emotional, behavioral, and social competence problems whereas inhibition was a significant predictor of behavioral problems. This suggests that different executive function profiles in children with epilepsy may place them at-risk for developing different types of emotional, behavioral, and social competence problems. These results may help researchers and clinicians develop new techniques to identify and treat emotional, behavioral, and social competence problems in children with epilepsy.     

Inhibition: Mental Control Process or Mental Resource?

The current study tested 2 models of inhibition in 45 children with language impairment and 45 children with normally developing language; children were aged 7 to 12 years. Of interest was whether a model of inhibition as a mental-control process (i.e., executive function) or as a mental resource would more accurately reflect the relations among mental-attentional (M) capacity, inhibition, updating, shifting, and language competence. Children completed measures of M-capacity (in the verbal and nonverbal domains), inhibition, updating, shifting, and language. Path analyses showed the data provided a poor fit to the model of inhibition as a mental-control process but a good fit to the model of inhibition as a mental resource. Results are consistent with the theory of constructive operators and suggest inhibition is a mental resource rather than a mental-control process.     

Effect of normal aging on the manipulation of information in working memory

The goal of this study is to examine the central executive of working memory in normal aging, specifically focusing on its capacities to manipulate or modify the format of the to-be-recalled material. The central executive was measured with the alphabetical span procedure, during which subjects were asked to recall a random series of words in their alphabetical order. The storage demand was equalized across subjects by adjusting the list lengths according to individual span. Experiments 1, 2, and 3 showed that elderly subjects were not impaired in manipulating information, relative to young controls, even when the difficulty of the task was increased. In Experiment 4, validity was tested by asking young subjects to perform the task under the conditions of full or divided attention. Alphabetical recall was more impaired than direct recall during the divided attention condition, which suggests a larger involvement of the central executive component in the former. These results are discussed in relation to the hypothesis of a central executive impairment being associated with normal aging.