Electrophysiological study of working memory in mild cognitive impairment patients.
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Analysis of Variance↗
Biomedical subjects
S Belleville
Publications and source records attributed to S Belleville.
[Mild cognitive impairments in the elderly: a critical review].
The aging of the population leads to increased awareness of problems associated with age-related degenerative dementias. Given that these dementias are progressive in onset, many clinicians and researchers have proposed criteria that allow for the identification of older subjects manifesting cognitive impairment, but not responding to the criteria for dementia. Our knowledge of subjects with mild cognitive impairment is limited; it is, however, established that they present a high risk of developing dementia in the future. Although it is essential to increase our comprehension of their cognitive and functional decline, the study of subjects presenting mild cognitive impairment is compromised due to the existence of numerous non-converging classifications. The goal of the present article is to conduct a critical review of the different classifications of mild cognitive impairment in the elderly in order to attempt to identify the optimal criteria, allowing for a distinction to be made between subjects with mild cognitive impairment, who remain in a stable state and those whose condition evolves to a dementia. These criteria may enable us to describe a homogenuous group of individuals presenting with different rates of dementia risk factors. We present the classifications most frequently used in clinical and research settings. After listing them according to categorial, clinical or dimensional approaches, we performed a critical analysis for each one. Depending on the diagnostic criteria applied, major variations are revealed for the prevalence of cognitive impairment and the incidence of dementia. They are explained by methodological and theoretical shortcomings that we point out and discuss (e.g., reference group, lack of diagnostic criteria or exclusion criteria, high level of subjectivity). Beyond these criticisms, we discuss the challenges to be met in order to reach the optimal identification criteria. Notably, the impact of mild cognitive impairment on daily living activities should be tested with the use of more specific questionnaires/tasks. The goal of the objective definition of cognitive impairment should be to minimize subjectivity in the diagnosis. It is also suggested that sensitive cognitive measures would be used on all aspects of cognition, while recognizing and taking into account all confounding factors (e.g., age, education level). Given the nature and consequences of mild cognitive impairment, an inter-disciplinary approach is suggested (e.g., neurobiological, psychiatric, and genetic cues). A consensus on optimal diagnostic criteria is essential to propose cognitive and pharmacological treatments for the effective prevention of ementia.
Age Factors↗
Education, age, and the Brown-Peterson technique.
In this article, we discuss the effects of education level and age on short-term memory. The performance of young and elderly persons was compared on an adapted version of the Brown-Peterson procedure. Participants were asked to report consonant trigrams, after variable time periods, during which they performed a mental addition task or an articulation task. A control condition consisted of a no-interference task. Both age groups were divided according to individual educational level (greater or less than the median number of school years in each age group). The results revealed a significant effect of education. Moreover, the education effect interacted with the task: participants with less education were more impaired in mental addition than in articulation. However, neither the age effect nor the interactions involving age reached significance. These results indicate that education, to a greater extent than age, should be considered a determining factor of performance when interpolated tasks of high demand are used with the Brown-Peterson procedure.
Adult↗
A study of memory functioning in individuals with autism.
Memory tasks were administered to 14 high-functioning individuals with autism and 14 typically developing individuals matched on chronological age and verbal intelligence. The tasks consisted of free and cued recall of 15 semantically unrelated words in 3 encoding conditions: phonological encoding, semantic encoding, and a no encoding orientation. In both groups, semantic orientation led to better free recall than did orientation toward syllabic encoding or absence of orientation. In contrast, semantic cues at retrieval led to better cued recall than phonological cues in typically developing individuals, whereas both types of cue had the same effect in prompting cued recall for individuals with autism. These findings are incompatible with the hypothesis of an amnesic deficit and do not support the notion of executive or semantic deficits in the memory problems of autistic individuals, at least for those with a high level of functioning. It is proposed that these findings can be accounted for by enhanced phonological processing in autism. This interpretation is consistent with other findings of enhanced processing of low-level perceptual information in the visual and auditory modality in autism.
Adolescent↗
[Plurality of patterns of cognitive impairment in normal aging and in dementia].
Normal aging, as well as most of the degenerative diseases of the central nervous system characterizing old age, have an impact on cognitive abilities which are obvious as well as increasingly understood. Cognitive changes in normal ageing realize a plurality of possible patterns of cognitive disabilities. Dementias are also well known to be characterized by a plurality of cognitive impairments patterns. The different cognitive patterns are likely to be due to distinct levels of impairments of different domains of cognition, or of different components within one given domain of cognition. These differences are such that in some cases they can even realize double dissociations. The plurality of cognitive impairments patterns in normal aging and in dementia will be discussed as well as the different factors that could contribute to such a plurality. Some of these factors relate to pre-morbid characteristics of the individuals known to influence the functional organization of the brain for cognition. Others--of major importance--are related to the nature and the distribution of the pathophysiological processes underlying normal ageing or a given degenerative disease. It is also reminded that some or many of these factors can interact with more general cognitive factors, such as speed of execution. It is however suggested that, despite of their presence, these general factors partly contribute to the cognitive impairments in neurodegenerative dementia. In this case, the impact of different disease-related factors over a general cognitive factor is probably much greater than in the case of normal aging.
Aged↗
Cognitive processing of drawing abilities.
This critical review examines constructional apraxia from a cognitive neuropsychological perspective. To our knowledge, van Sommers (1989) is the only researcher to present a global cognitive model of drawing abilities. He organizes it into two hierarchical systems: Marr's model of visual perception and a graphic production system. The latter comprises four hierarchically organized components: depiction decisions, production strategy, contingent planning, and articulatory and economic constraints. Van Sommers' model will be discussed in light of other models and on the basis of empirical neuropsychological studies (Farah, 1984; Kosslyn & Koenig, 1992; Roncato, Sartori, Masterson, & Rumiati, 1987; van Sommers, 1989). We find that: (1) the Kosslyn and Koenig visual perception model describes more accurately the perceptual components underlying copying than the visual perception system of van Sommers' drawing model, (2) Van Sommers' arguments in favor of a depiction processing as opposed to visual imagery are not convincing, (3) Van Sommers' assumption that a production strategy is a component is unclear, and (4) articulatory and economic constraints are not cognitive components, but constraints imposed during action programming. This literature review leads to a discussion of future research topics and the specificity of constructional apraxia.
Apraxias↗
Regional brain activity during tasks devoted to the central executive of working memory.
Most previous PET studies investigating the central executive (CE) component of working memory found activation in the prefrontal cortex. However, the tasks used did not always permit to distinguish precisely the functions of the CE from the storage function of the slave systems. The aim of the present study was to isolate brain areas that subserve manipulation of information by the CE when the influence of storage function was removed. A PET activation study was performed with four cognitive tasks, crossing conditions of temporary storage and manipulation of information. The manipulation of information induced an activation in the right (BA 10/46) and left (BA 9/6) middle frontal gyrus and in the left parietal area (BA7). The interaction between the storage and manipulation conditions did not reveal any significant changes in activation. These results are in agreement with the hypothesis that CE functions are distributed between anterior and posterior brain areas, but could also reflect a simultaneous involvement of controlled (frontal) and automatic (parietal) attentional systems. In the other hand, the absence of interaction between the storage and manipulation conditions demonstrates that the CE is not necessarily related to the presence of a memory load.
Adult↗
Local bias in autistic subjects as evidenced by graphic tasks: perceptual hierarchization or working memory deficit?
In the present study, copying tasks were used to assess hierarchical aspects of visual perception in a group of 10 nonsavant autistic individuals with normal intelligence. In Experiment 1, the hierarchical order of graphic construction and the constancy of this order were measured for the copying of objects and nonobjects. In comparison to control participants, autistic individuals produced more local features at the start of the copying. However, they did not differ from controls with respect to graphic constancy. Experiment 2 measured the effect of geometrical impossibility on the copying of figures. Results revealed that autistic individuals were less affected by figure impossibility than were controls. Therefore, these experiments seem to support the notion of a local bias for visual information processing in individuals with autism. Two interpretations are proposed to account for this effect. According to the hierarchical deficit hypothesis, individuals with autism do not manifest the normal global bias in perceiving scenes and objects. Alternatively, the executive function hypothesis suggests that autism brings about limitations in the complexity of information that can be manipulated in short-term visual memory during graphic planning.
Adolescent↗
Atypical memory performance in an autistic savant.
This study explored the mechanisms underlying the hypermnesia of an autistic savant (NM) through three experiments. The first two served to assess whether absence of interference was responsible for NM's exceptional list memory. The third investigated the type of cues used in recall. Results indicated absence of retroactive interference but presence of slight proactive interference in list recall of proper names. Normal interference effects were found, however, in list recall of common nouns. Exceptional performance was also demonstrated in a missing-name task involving spatial and verbal recall cues. The findings suggest that the outstanding episodic memory presented by some savant persons with autism might be related to an abnormally high resistance to interference.
Adolescent↗
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.
Adult↗
[Dissociations between music and language functions after cerebral resection: A new case of amusia without aphasia].
We present the neuropsychological study of a patient, I.R., who sustained bilateral damage to the temporal lobes and to the right frontal lobe as a result of successive brain surgeries that occurred ten years earlier. The patient is 40 years old and right-handed; she had no special training in music or in language, representing, therefore, the large majority of listeners. Her performance is compared to that of four neurologically intact subjects who are closely matched in terms of education, sex and age. In the present study, we report I.R.'s performance on various tests aiming at assessing her general cognitive functioning with a particular focus on auditory aspects. The results show that, despite extensive damage to her auditory cortex, I.R.'s speech abilities are essentially intact (see Tables 1 and 2). The only impairments that are detected in the language domain are related to a short-term memory deficit, to some abnormal sensitivity to retroactive interference in long-term memory (see Table 3) and to articulation. These difficulties do not, however, affect linguistic communication, which is obviously undisturbed I.R. is not aphasic). Similarly, I.R. does not experience any difficulty in the recognition and memorization of familiar sounds such as animal cries, traffic noises and the like (see Tables 5 and 7). In contrast, I.R. is severely impaired in most musical abilities: She can no longer discriminate nor identify melodies that were once highly familiar to her; she can no longer discriminate nor memorize novel melodies (see Table 4). Her pattern of musical losses is compatible with a basic and severe perceptual deficit that compromises access to and registration in memory systems. The observation that the auditory impairment affects music and spares language and environmental sounds refers to a neuropsychological condition that is known as music agnosia. I.R. represents, to our knowledge, the fourth case of music agnosia available in the literature (Peretz et al., 1994; Griffiths et al., 1997). The existence of such cases suggests that music processing is not mediated by a general-purpose auditory architecture but by specialized cortical subsystems. Not only does I.R. suffer from music agnosia, but she is also impaired in the discrimination and recognition of musical instruments and of human voices (see Table 5). These latter two deficits probably do not result from the music agnosic condition. Rather, they seem to reflect damage to adjacent brain areas that are specialized in timbre processing (see Peretz. et al., 1994, for the relevant discussion). It is also worth mentioning that I.R. appears to be impaired in musical expressive abilities as well: I.R. can no longer sing a single note. Thus, her losses are rather general in the musical domain, hence justifying the classification of her case as amusia. Cases of amusia without aphasia are relatively frequent in the neuropsychological literature. However, all of these reported cases are anecdotal. Thus, in the present study, special focus is given to the measurement and direct comparison of performance in the language and music domain; in both domains, task characteristics and materials were as similar as possible. To this aim, the lyrics and the tune of the same popular song excerpts were used. The musical and the spoken parts were presented separately in a primed familiarity decision task and in a memory recognition task. In both situations, I.R. performs at or close to chance when she has to deal with music, whereas she recognizes easily and performs normally on the spoken material (see Tables 6 and 7). These results clearly argue for the autonomy of music and language in the processing of auditory information.
Adult↗
Proper name hypermnesia in an autistic subject.
The case study of an autistic "savant" subject with person names hypermnesia is presented. NM's performance in memorizing person names is compared to that of normal controls, IQ-matched controls, and one overtrained control. The data show a selective hypermnesia for both the free recall of person names and the recognition of faces. Recall of common names and of biographical informations linked to faces is unremarkable. NM's hypermnesia is restricted to list learning as low performance is observed in face-name learning tasks. A comparison of the data with that of the overtrained control indicates that training is not responsible for NM's pattern of results. These findings, when combined with previous results involving proper names, demonstrate a double dissociation between proper names and other types of semantic and referential information. However, aspects of NM's performance pattern are more compatible with a network model of proper names than with a sequential model. We propose that the contextual regularity of proper names in ecological situations can be responsible for their high memorization by NM.
Adult↗
Examination of the working memory components in normal aging and in dementia of the Alzheimer type.
The verbal and attentional components of working memory were examined in patients with Alzheimer's disease, normal elderlies, and young controls. Patients with Alzheimer's disease, showed a reduced span but were sensitive to word length. This is indicative of a functional rehearsal procedure. However, the effect of phonological similarity on immediate recall was smaller in patients with Alzheimer's disease and these patients showed a depressed performance in tasks of phonological analysis. There was also a significant decrement in a task that assessed the attentional component of working memory. Examination of individual patterns of performance showed that the phonological deficiency was severe in a subgroup of patients while the attentional deficit was more general.
Adolescent↗
Irrelevant speech effect in aging: an assessment of inhibitory processes in working memory.
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.
Adult↗
Perspective production in a savant autistic draughtsman.
This study examines perspective construction in an autistic patient (E.C.) with quasinormal intelligence who exhibits exceptional ability when performing three-dimensional drawings of inanimate objects. Examination of E.C.'s spontaneous graphic productions showed that although his drawings approximate the 'linear perspective' system, the subject does not use vanishing points in his productions. Nevertheless, a formal computational analysis of E.C.'s accuracy in an experimental task showed that he was able to draw objects rotated in three-dimensional space more accurately than over-trained controls. This accuracy was not modified by suppressing graphic cues that permitted the construction of a vanishing point. E.C. was also able to detect a perspective incongruency between an object and a landscape at a level superior to that of control subjects. Since E.C. does not construct vanishing points in his drawings, it is proposed that his production of a precise realistic perspective is reached without the use of explicit or implicit perspective rules. 'Special abilities' in perspective are examined in relation to existing theoretical models of the cognitive deficit in autism and are compared to other special abilities in autism.
Adult↗
A pure reversible amnesic syndrome following tuberculous meningoencephalitis.
The authors report the case of a 33-year-old right-handed man who developed a pure classical amnesic syndrome during the course of a probable tuberculous meningitis. This amnesic syndrome occurred 3 months after the onset of the illness, after the patient had stopped the treatment and it regressed completely after the antituberculous treatment had been recommenced. The neuroradiological investigations suggested that both the mamillary bodies and the medial temporal lobe regions were involved in this amnesic syndrome.
Adult↗
Functional dissociations following bilateral lesions of auditory cortex.
We present two patients with bilateral lesions of the superior temporal cortex who manifested a number of functional dissociations in the auditory domain. The perception of speech and environmental sounds were preserved; yet, the perception of tunes, prosody and voice was impaired. As the processing of melodic but not rhythmic variations in musical sequences was selectively disturbed, the deficit cannot be attributed to a general impairment in auditory memory or sequential processing. These findings suggest that melody processing is not mediated by a general-purpose auditory architecture but by specialized cortical subsystems residing within the lesioned areas. Current taxonomies of auditory agnosia and models of normal music cognition are evaluated in light of the functional dissociations manifested by these patients.
Adult↗
[The approach of cognitive neuropsychology toward the studies on autism].
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Adult↗