Future research should take into account the lack of homogeneity observed within the population of children with a vocabulary delay at 2 years of age and attempt to identify subgroups within late-talking toddlers. It should also consider a multifactorial perspective of child development to further the understanding of this phenomenon.

HRSZ and HRBP shared several aspects of their cognitive impairment. Our data suggest that the extremely high genetic and familial loading of these HRs may have contributed to a quantitatively increased magnitude of the cognitive impairments in both HR subgroups, especially in memory. These offspring at heightened risk present difficulties in processing information that warrant preventive research.

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.Working memory (WM) is a short-term memory system involved in tasks that require concurrent retention and processing (Baddeley, 1986;Baddeley & Hitch, 1974, 1994Salthouse, 1994). In Baddeley's theoretical framework, WM is a tripartite system composed of two specialized slave systems-the phonological loop and the visuo spatial sketchpad-and a central executive. The phonological loop contributes to the retention ofverbal information and is subdivided into a passive phonological store and a rehearsal procedure. The visuospatial sketchpad holds images and spatial information. The central executive is an attentional component involved in the control and distribution oflimited resources (Baddeley, 1986(Baddeley, , 1992Baddeley & Hitch, 1974). This study focuses on the manipulation capacities of the central executive in normal aging. Manipulation is defined as the process of actively and consciously modifying the format of the information to be recalled. Within a WM framework, manipulation would require involvement of the central executive component.This work was supported by a grant from the Medical Research Council of Canada (MRC; PG-28) and from Ie Fond de la Recherche en Sante du Quebec (FRSQ) to S,8., by a chercheur-boursier fellowship from the FRSQ to S.8., and by a scholarship from the FCAR to N.R. and N,C. The authors thank Laurent Mottron, Francois Crepeau, Geoffrey R. Loftus, Frank Bellezza, and Leah Light for their helpful comments on an earlier version of the text Thanks to Michel Lamoureux and Jean-Francois Angers for statistical advice, as well as to Fanny Guerin, Sherif Karama, and Sonia Litalien for testing assistance. Special thanks to Rodolphe Sauvage for conducting Experiment 3. Finally, the authors gratefully acknowledge Ronald Dixon for his comments and for editing the text. Correspondence concerning this article should be addressed to Sylvie Belleville, Centre de Recherche de l'Institut Universitaire de Geriatric de...

The purpose of this study was to assess whether older adults can inhibit irrelevant auditory information while performing a span task. In Experiment 1, young and older participants recalled seven visually presented digits while subject to three types of irrelevant noise; white noise (nonverbal), and familiar and nonfamiliar language (verbal). A baseline measure was obtained in silence. The effect of each noise was also assessed under articulatory suppression (AS). In Experiment 2, the number of digits to recall was adjusted to participants' individual span. Results show a clear irrelevant speech effect (ISE), that is, recall declines in the presence of familiar and nonfamiliar verbal noise, but is unaffected by white noise. AS negates ISE. Most important, ISE does not interact with age: older adults have no more difficulty inhibiting irrelevant auditory information than do young adults. These results are discussed relative to current theories of inhibition in aging.

This study measures the effect of Alzheimer's disease (AD) and normal aging on the inhibition of prepotent responses. AD patients, normal aged controls, and young subjects were tested with the Hayling task, which measures the ability to inhibit a semantically constrained response, and with the Stroop procedure. AD patients showed a severe deficit in both error rates and response time on the Hayling task. Inhibition was also impaired on the Stroop procedure, both when using raw performance and when using an inhibition score that controlled for reading and naming speed. Normal aged participants showed modest impairment relative to young controls on both tests. Examination of individual performance in AD patients indicated that the impairment was found in most patients on the Hayling test but in only a subgroup of patients on the Stroop test.

The objectives of this study were to characterize the sleep of children with attention deficit hyperactivity disorder (ADHD), using actigraphy and parental questionnaires, and examine the potentially moderating role of psychostimulant medication and psychiatric comorbidity. Children with ADHD significantly differed from controls on parental and actigraphic measures of sleep, with parental reports indicating more severe sleep disturbances, and actigraphic recordings of longer sleep onset latency, lower sleep efficiency, and lower total sleep time. Both medicated and unmedicated ADHD subgroups differed from the control group on sleep measures, but did not differ from each other. Only the subgroup with comorbid psychiatric symptoms differed from the control group on actigraphic measures. The presence of psychiatric comorbidity, but not psychostimulant medication use, was associated with more severe sleep disturbances. The main implication of these findings is that clinicians should systematically attend to sleep disturbances in children with ADHD, particularly when other psychiatric symptoms are also present.

The effect of manipulation and distracting noise on immediate serial recall was measured in patients with dementia of the Alzheimer type (DAT), normal elderly individuals and young subjects. Experiment 1 compared serial word recall to word recall in alphabetical order. Alphabetical recall requires the active manipulation of the contents of working memory. Findings indicated that patients were severely impaired in the alphabetical recall task whereas performance of normal elderly subjects was comparable to young subjects. Experiment 2 investigated the effect of different irrelevant auditory backgrounds on immediate digit recall. In this task, both normal elderly subjects and DAT patients performed similarly to the group of young subjects, indicating comparable efficacy to resist auditory distraction. Heterogeneity of performance was assessed in the DAT patients, revealing that the alphabetical tasks yielded particularly heterogeneous performance levels. Finally, the absence of any systematic relationship between the two tasks suggests that they reflect different aspects of working memory.Key words: working memory, dementia of the Alzheimer type, manipulation, distraction, ageing Inhibition and manipulation in DAT 3Alzheimer's disease is the major cause of dementia. As no biological marker of Alzheimer's disease currently exists, the diagnosis of dementia of the Alzheimer type (DAT) relies on extensive neurological and neuropsychological assessment. In this context, the task of the clinical neuropsychologist is to find evidence for the presence of a cognitive impairment which goes beyond that observed in the normal course of ageing.There are empirical data suggesting that working memory (WM) is impaired in DAT. WM is a short-term retention system involved in on-line processing and maintenance of information. This memory system plays a major role in numerous cognitive tasks including language comprehension, mental calculation, and the control of actions. A decrease in the span capacities of DAT patients has been reported for numerous types of material (Belleville, Peretz &, Malenfant, 1996;Corkin, 1982;Dannenbaum, Parkinson, & Inman, 1988;Hulme, Lee, & Brown, 1993; Kaszniack, Garon, & Fox, 1979;Kopelman, 1985;Morris, 1984;1987;Orsini, Trojano, Chiacchio, & Grossi, 1988;Spinnler, Della Sala, Bandera, & Baddeley, 1988).However, span is typically not very helpful in early diagnosis as it is unimpaired in early DAT patients (Corkin, 1982;Martin, Brouwers, Cox & Fedio, 1985;and Orsini et al., 1988).Other researchers have found that DAT patients are particularly impaired in WM tasks that implicate dual task coordination. DAT patients are impaired in adapted versions of the Brown-Peterson procedure Morris, 1986) whereby subjects are required to memorize letters while performing tasks of increasing difficulty (e.g.: finger tapping, articulation, digit addition). Baddeley and collaborators (Baddeley, Bressi, Della Sala, Logie & Spinnler, 1991;Baddeley, Logie, Bressi, Della Sala, & Spinnler, 1986) have used a divided...

Cognitive impairments are central to schizophrenia, but their clinical utility for tagging heterogeneity in lifetime outcome and response to treatment is not conclusive. By exploiting four cognitive domains consistently showing large deficits in studies, we tested whether cluster analysis would define separate subsets of patients and then whether the disease heterogeneity marked by these clusters would be related to lifetime outcome and response to treatment. A total of 112 schizophrenia patients completed a neuropsychological evaluation. The PANSS, GAF-S and GAF-F were rated at the onset and endpoint of the illness trajectory. A blind judgment of the lifetime response to treatment was made. The first cluster presented near-normal cognitive performance. Two other clusters of severely impaired patients were identified: one generally impaired in the four cognitive domains and another selectively impaired in visual episodic memory and processing speed, each relating to a different lifetime evolution of disease and treatment response. Although the two impaired clusters were clinically indistinguishable in symptom severity and functioning at disease onset, patients with selective cognitive impairments demonstrated better improvement at outcome, whereas the generally impaired patients were more likely to be treatment refractory. The findings have implications for the management of patients and for clinical trials since particular combinations of cognitive deficits in patients would influence their treatment response.