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M Van der Linden

Publications and source records attributed to M Van der Linden.

At least 19 recordsLinked to original sources
PubMed2006

The left intraparietal sulcus and verbal short-term memory: focus of attention or serial order?

One of the most consistently activated regions during verbal short-term memory (STM) tasks is the left intraparietal sulcus (IPS). However, its precise role remains a matter of debate. While some authors consider the IPS to be a specific store for serial order information, other data suggest that it serves a more general function of attentional focalization. In the current fMRI experiment, we investigated these two hypotheses by presenting different verbal STM conditions that probed recognition for word identity or word order and by assessing functional connectivity of the left IPS with distant brain areas. If the IPS has a role of attentional focalization, then it should be involved in both order and item conditions, but it should be connected to different brain regions, depending on the neural substrates involved in processing the different types of information (order versus phonological/orthographic) to be remembered in the item and order STM conditions. We observed that the left IPS was activated in both order and item STM conditions but for different reasons: during order STM, the left IPS was functionally connected to serial/temporal order processing areas in the right IPS, premotor and cerebellar cortices, while during item STM, the left IPS was connected to phonological and orthographic processing areas in the superior temporal and fusiform gyri. Our data support a position considering that the left IPS acts as an attentional modulator of distant neural networks which themselves are specialized in processing order or language representations. More generally, they strengthen attention-based accounts of verbal STM.

Adult↗
PubMed2006

Chronic posttraumatic stress symptoms after nonsevere stroke.

OBJECTIVE: To determine whether posttraumatic stress disorder (PTSD)-related symptoms were present 1 year after a nonsevere stroke and, if so, to examine the relationship between PSTD, coexisting cognitive variables, and infarct localization METHODS: The authors assessed 49 patients using standard measures of memory, trauma experience, neurologic deficit, depression, anxiety, and PTSD. RESULTS: Fifteen (31%) patients had significant PTSD symptoms on the Impact of Event Scale (IES > 30). PTSD-like syndrome was independent of neurologic impairment, peristroke amnesia, long-term memory impairment, nosognosia, hypochondriac preoccupations, and physical pain during hospitalization, but was more frequent in women, less educated patients, and patients with more negative appraisals of the stroke experience. Intrusions were increased after basal ganglia strokes, suggesting that the re-experiencing phenomena may be modulated by frontosubcortical pathways. CONCLUSIONS: Posttraumatic stress disorder symptoms seem frequent in patients with nonsevere stroke and were associated with the subjective intensity of the stroke experience and accompanied by a depressive and anxious state.

Adult↗
PubMed2006

A multiple case study of verbal short-term memory in velo-cardio-facial syndrome.

BACKGROUND: Velo-cardio-facial syndrome (VCFS, 22q11.2 deletion) is characterized by severely delayed language development. The current study explored the integrity of verbal short-term memory (STM), a cognitive function critically involved in language development, in eight children with VCFS. METHODS: Using a multiple case study design, we presented a series of STM tasks exploring immediate serial recall for word and non-word lists to eight children with VCFS (aged 8-12 years) and to chronological-age-matched control groups. A first task assessed the integrity of phonological coding in verbal STM by comparing recall for phonologically similar and dissimilar words. Subsequently, the interaction between verbal knowledge and STM capacity was investigated by comparing recall for high- and low-imageability words, for high- and low-frequency words, and for words and non-words. A final task assessed short-term serial order recognition for digit sequences. RESULTS: When computing the number of items recalled in the word recall tasks, independently of their serial position, only one child presented consistent difficulties. Short-term recall of non-words was normal in each child. Phonological similarity and verbal knowledge influenced STM performance to a similar extent in children with VCFS and controls. On the other hand, when applying a strict serial recall criterion, difficulties with the word and non-word recall tasks were observed in most children. Half of the patients were also impaired in the serial order recognition task. CONCLUSIONS: Despite mild intellectual disability, it is possible for short-term retention capacities for verbal item information to be at an age-appropriate level in VCFS. However, STM for serial order information could be impaired more specifically.

Child↗
PubMed2005

Exploration of the neural substrates of executive functioning by functional neuroimaging.

This review presents neuroimaging studies that have explored the cerebral substrates of executive functioning. These studies have demonstrated that different executive functions not only recruit various frontal areas but also depend upon posterior (mainly parietal) regions. These results are in accordance with the hypothesis that executive functioning relies on a distributed cerebral network that is not restricted to anterior cerebral areas. However, there exists an important heterogeneity in the cerebral areas associated with these different processes, and also between different tasks assessing the same process. Since these discrepant results could be due to the paradigms used (subtraction designs), recent results obtained with conjunction and interaction analyses are presented, which confirm the role of parietal areas in executive functioning and also demonstrate the existence of some specificity in the neural substrates of the executive processes of updating, shifting and inhibition. Finally, functional magnetic resonance imaging studies show that the activity in cerebral areas involved in executive tasks can be transient or sustained. Consequently, to better characterize the functional role of areas associated with executive functioning, it is important to take into account not only the localization of cerebral activity but also the temporal pattern of this activity.

Cerebral Cortex↗
PubMed2005

Metacognitions in proneness towards hallucinations and delusions.

The objectives of the present study were to examine the degree of co-existence of hallucinations and delusions in the nonclinical population. In addition, we wished to investigate the role of metacognitions in hallucinations and delusions. Finally, we explored the relative roles of positive and negative metacognitive beliefs in proneness to hallucinations and delusions. Three hundred and thirty-one nonclinical participants completed instruments assessing: hallucination-proneness (Launay-Slade Hallucinations Scale; LSHS), delusion-proneness (21-item version of the Peters et al. Delusions Inventory; PDI-21) and metacognitive beliefs (Meta-Cognitions Questionnaire; MCQ). Participants were successively grouped according to their scores on the LSHS and the PDI-21. Results revealed that hallucination-proneness was positively and significantly associated with delusion-proneness. Furthermore, hallucination-prone and delusion-prone participants scored significantly higher on some sub-scales of the MCQ compared to non-prone participants. Finally, multiple regression analysis revealed that positive and negative beliefs were good predictors of proneness towards hallucinations and delusions.

Adult↗
PubMed2004

[Neuropsychological rehabilitation in early stage Alzheimer's disease: principles, methods and perspectives].

An increasing number of studies have demonstrated the efficiency of various neuropsychological interventions on individuals with early Alzheimer's disease. There are also some encouraging findings suggesting that the interventions can be successfully applied in less controlled real-world contexts and largely provided into caregiving systems. The interventions have to be directly focused on daily life situations and they should include the perspective of the patients by allowing them to retain a capacity to maximize their cognitive abilities, to state specific preferences and needs, and to make intervention-related decisions.

Alzheimer Disease↗
PubMed2004

The effects of emotional salience, cognitive effort and meta-cognitive beliefs on a reality monitoring task in hallucination-prone subjects.

OBJECTIVES: A tendency to externalize internal information on reality monitoring tasks has been documented in psychiatric patients with hallucinations. Furthermore, previous studies suggest that factors such as the emotional salience of the material, cognitive effort and meta-cognitive beliefs are important contributory factors in this tendency to externalize internal information on reality monitoring tasks. However, few studies have investigated these aspects in hallucination-prone subjects. Also, these factors have never been examined simultaneously. In the following study we wished to examine the effects of emotional salience, cognitive effort and meta-cognitive beliefs on reality monitoring functioning in hallucination-prone subjects. DESIGN: Between-participants group design. METHOD: One hundred normal subjects were administered a reality monitoring task. Words were presented by the experimenter. After each word, subjects were asked to say the first word that came to their mind. Words varied in terms of emotional valence and cognitive effort (high cognitive effort for words requiring longer latency times to associate a word and vice versa). Following a delay, words were presented consisting of those already presented by the experimenter or the subject (old) and those never presented before (new). For each word, subjects were required to identify whether the word was old or new. If the word was identified as old, subjects were required to identify the source of the word (subject or experimenter). Subjects also completed a questionnaire assessing meta-cognitive beliefs. RESULTS: Subjects were grouped according to their scores on a revised and elaborated version of the Launay-Slade Hallucinations Scale (LSHS). Those with scores within the top 25% were included in the hallucination-prone group (HP) (N = 25), whereas scores within the lower 25% were included in the non-hallucination-prone group (NHP) (N = 25). Results showed that the HP subjects had significantly more source discrimination errors than NHP subjects for self-generated items. In other words, HP subjects tended to misattribute to the experimenter items that they had produced themselves. This pattern was especially marked with emotionally charged material and with words that required more cognitive effort. In addition, HP subjects scored significantly higher on a scale assessing meta-cognitive beliefs compared with NHP subjects. Finally, scores on a scale assessing meta-cognitive beliefs were positively associated with source discrimination errors. CONCLUSIONS: These results suggest that cognitive effort, emotional salience and meta-cognitive beliefs all play a prominent role in the externalizing bias in hallucination-prone subjects. The results also provide evidence for the validity of the idea of a continuity between hallucination-prone subjects and psychotic patients with hallucinations on reality monitoring tasks, including a number of contributing factors in the occurrence of hallucinations.

Adult↗
PubMed2003

Alzheimer's disease as a disconnection syndrome?

This paper reviews the growing amount of evidence supporting the hypothesis that Alzheimer's disease includes a disconnection syndrome. This evidence came mainly from neuropathological, electrophysiological, and neuroimaging studies. Moreover, a few recent neuropsychological studies have also explored the effects of a disconnection between cerebral areas on cognitive functioning. Finally, and more generally, the contribution of this interpretation to the understanding of Alzheimer's disease cognitive deficits is considered.

Alzheimer Disease↗
PubMed2002

Effects of incidental and intentional feature binding on recognition: a behavioural and PET activation study.

Using Positron Emission Tomography (PET), we investigated cerebral regions associated with the episodic recognition of words alone and words bound to contextual colours. Two modes of colour encoding were tested: incidental and intentional word-to-colour binding. Word-only recognition was associated with brain activation in a lexico-semantic left middle temporal region and in the cerebellum following an incidental colour encoding, and with brain activation in the left posterior middle frontal gyrus, right anterior cingulate and right inferior frontal gyrus following an intentional encoding. Recognition of bound features was associated with activation in left prefrontal and superior parietal regions following an incidental colour encoding, and with preferential right prefrontal cortex activation following an intentional colour encoding. Our results are in line with the hypothesis of a parietal involvement in context processing, and prefrontal areas in monitoring retrieval processes. Our results also support the hypothesis of a 'cortical asymmetry for reflective activity' (CARA).

Adult↗
PubMed2001

Neural and cognitive bases of upper limb apraxia in corticobasal degeneration.

OBJECTIVE: To investigate the neural and cognitive bases of upper limb apraxia in corticobasal degeneration (CBD). METHODS: Eighteen patients with CBD underwent a cognitive neuropsychological assessment of apraxia and resting [(18)F]-fluorodeoxyglucose PET scanning. Two complementary measures of apraxia were computed for each modality of gesture production. First, a performance score measured error frequency during gesture execution. Second, as a more stringent test of the integrity of the praxis system, the correction score measured the patient's ability to correct his or her errors on a second attempt. For each measure type, a cut-off score for the presence of apraxia was defined with regard to healthy controls. Using each cut-off score, the regional cerebral glucose metabolism of patients with CBD with apraxia (i.e., performing below cut-off score) was compared with that of patients with CBD without apraxia. RESULTS: Mean performance scores were below normal values in all modalities. Anterior cingulate hypometabolism predominated in patients with CBD who performed below the cut-off performance score. At variance, mean correction scores were below normal values for gesture imitation only. Hypometabolism in superior parietal lobule and supplementary motor area characterized patients with CBD who were unable to correct their errors at the same rate as control subjects did. CONCLUSIONS: Distinct neural networks underlie distinct aspects of the upper limb apraxic deficits in CBD. Extending previous findings of gesture production deficits in CBD, the use of complementary measures of apraxic behavior discloses a visuoimitative upper limb apraxia in CBD, underlain by a metabolic decrease in a parietofrontal neural network.

Aged↗
PubMed2001

Supervisory attentional system in nonamnesic alcoholic men.

BACKGROUND: Many studies have shown that recently detoxified alcoholic persons perform poorly on tasks thought to be sensitive to frontal lobe damage, supporting the hypothesis that the frontal lobes are highly vulnerable to chronic alcohol consumption. However, it appeared that most of the executive tasks used in these studies also involved nonexecutive components, and these tasks had been shown to be impaired as a result of nonfrontal lobe lesions. In this study, we examined further the "frontal lobe vulnerability" hypothesis using executive tasks, proved to be associated with frontal lobe functioning, that allowed us to distinguish the relative importance of executive and nonexecutive processes. METHOD: Thirty recently detoxified asymptomatic male alcoholic inpatients and 30 control subjects were tested for planning, inhibition, rule detection, and coordination of dual task, as well as the speed of processing and nonexecutive functions (such as short-term memory storage). RESULTS: Alcoholics performed worse than controls in almost all tasks assessing executive functions. However, they were not slower than the controls and showed normal results for nonexecutive functions. CONCLUSIONS: Chronic alcohol consumption seems to be associated with severe executive function deficits, which are still present after a protracted period of alcohol abstinence. These data support the idea that the cognitive deficits in recently detoxified sober alcoholic subjects are due, at least partly, to frontal lobe dysfunctioning.

Adult↗
PubMed2001

The functional anatomy of inhibition processes investigated with the Hayling task.

The cortical areas involved in inhibition processes were examined with positron emission tomography (PET). The tasks administered to subjects were an adaptation of the Hayling test. In the first condition (response initiation), subjects had to complete sentences with a word clearly suggested by the context, whereas in the second condition (response inhibition), subjects had to produce a word that made no sense in the context of the sentence. Results indicated that the response initiation processes were associated to increases of activity in the left inferior frontal gyrus (BA 45/47), whereas response inhibition processes led to increases in a network of left prefrontal areas, including the middle (BA 9 and BA 10) and inferior (BA 45) frontal areas.

Adult↗
PubMed2001

Memory impairment differs in frontotemporal dementia and Alzheimer's disease.

The aim of this study was to assess short-term and long-term explicit memory and implicit memory in frontotemporal dementia (FTD; frontal variant) and to compare FTD and Alzheimer's disease (AD) patients with similar severity of dementia. Fifteen FTD patients [mean age: 68 years; Mini-Mental State (MMS): 24], 30 probable AD patients (mean age: 72 years; MMS: 23) and 12 healthy subjects participated in the study. The three groups were comparable in terms of gender and educational level. Short-term memory was assessed with the digit span and Corsi block-tapping tests. Explicit verbal memory was assessed with the Grober and Buschke test, and implicit memory with a verbal priming task and a fragmented picture test. FTD patients demonstrated a genuine memory deficit with impaired digit span, encoding deficit and retrieval strategy difficulties, but preserved implicit verbal and visual priming. Memory patterns differed in AD and FTD: short-term memory and free recall were similarly decreased in FTD and AD but cues provided more benefit to FTD than to AD; encoding was more impaired and the forgetting rate was faster in AD than in FTD; priming was lower in AD than in FTD. AD patients with clinical and imaging frontal lobe dysfunction tended to have lower memory performance and to differ even more from FTD patients than AD patients without frontal lobe dysfunction.

Aged↗
PubMed2001

Acquisition of a novel vocabulary in an amnesic patient.

This study explored the ability of a severe amnesic patient (AC) to acquire new vocabulary words. We compared AC's knowledge of words entered into the French lexicon during three different periods: before 1920, between 1965 and 1985, and after 1986 (i.e. after the onset of his amnesia). AC's knowledge was assessed by asking him to give, for each word, its definition (word-definition task), the general domain to which the word belonged ("domain" task), and to generate a sentence containing the word (sentence-generation task). Finally, we administered a recognition task in which AC had to select, for each word, its correct definition amongst four definitions. For all of these tasks, the results showed that AC's performance was similar to that of four control subjects matched for age, education, and profession. In particular, there was no difference with regard to AC's knowledge of words entered into the language after the onset of his amnesia. Therefore, these results indicate that, despite his profound amnesia, AC was able to learn normally new vocabulary words. More generally, they confirm that, at least is some cases, semantic learning can be spared in amnesia.

Adult↗
PubMed2001

An atypical neuropsychological profile of a Korsakoff syndrome patient throughout the follow-up.

The basis of amnesia in alcoholic Wernicke-Korsakoff syndrome (WKS) has been generally associated with diencephalic lesions and more specifically with lesions of the anterior thalamic nuclei. These brain structures are considered to be involved in encoding/consolidation processes of episodic memory. However, frontal lobe damage responsible for executive function deficits has also been documented. The present report details the nature and extent of amnesia in an alcoholic patients with WKS and which appears to be mainly due to frontal lobe (executive) deficits.

Alcohol Amnestic Disorder↗
PubMed2000

Striatum forever, despite sequence learning variability: a random effect analysis of PET data.

This PET study is concerned with the what, where, and how of implicit sequence learning. In contrast with previous studies imaging the serial reaction time (SRT) task, the sequence of successive locations was determined by a probabilistic finite-state grammar. The implicit acquisition of statistical relationships between serially ordered elements (i.e., what) was studied scan by scan, aiming to evidence the brain areas (i.e., where) specifically involved in the implicit processing of this core component of sequential higher-order knowledge. As behavioural results demonstrate between- and within-subjects variability in the implicit acquisition of sequential knowledge through practice, functional PET data were modelled using a random-effect model analysis (i.e., how) to account for both sources of behavioural variability. First, two mean condition images were created per subject depending on the presence or not of implicit sequential knowledge at the time of each of the 12 scans. Next, direct comparison of these mean condition images provided the brain areas involved in sequential knowledge processing. Using this approach, we have shown that the striatum is involved in more than simple pairwise associations and that it has the capacity to process higher-order knowledge. We suggest that the striatum is not only involved in the implicit automatization of serial information through prefrontal cortex-caudate nucleus networks, but also that it plays a significant role for the selection of the most appropriate responses in the context created by both the current and previous stimuli, thus contributing to better efficiency and faster response preparation in the SRT task.

Adult↗