M.H. van der Linden

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.

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.

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.

Phonological loop and central executive functioning in Alzheimer's disease

The phonological loop and central executive functioning were examined in patients with Alzheimers disease (AD) and in normal elderly subjects. AD patients showed abnormal functioning of the phonological loop and decreased performance on tasks assessing the central executive. However, when AD patients were separated into two groups on the basis of their span level, both groups showed deficits of the central executive but only patients with the lower span level presented a dysfunction of the phonological loop as well as impaired performance in tasks of phonological discrimination, articulation rate and speed of processing. These results are interpreted in terms of progression of the disease, with high-span level patients being less severely demented and displaying deficits only in higher-level cognitive functions (such as manipulation of information stored in working memory) whereas patients with a low span level have impairments encompassing a series of more basic processes.

Time course of the effects of diazepam and lorazepam on perceptual priming and explicit memory

The effects of diazepam and lorazepam on explicit memory and perceptual priming were studied 50, 130 and 300 min after drug administration. Sixty healthy volunteers were randomly assigned to one of five parallel groups (placebo, diazepam 0.2 or 0.3 mg/kg, lorazepam 0.026 or 0.038 mg/kg). The corresponding doses of benzodiazepines exerted a similar negative effect on explicit performance. Lorazepam markedly impaired priming performance, whereas the effect of diazepam was intermediate between that of placebo and that of lorazepam 0.038 mg/kg. The impairment was maximal at the theoretical peak plasma concentration. Contamination by explicit memory could account for the decrease in priming performance observed in the diazepam groups.

Pantomime interpretation and aphasia

Abstract In this study, 27 aphasic patients and 20 normal individuals took a drawn pantomime interpretation test. The scores made by aphasic patients were significantly lower than those of control subjects. The disorders observed could not be explained by the severity of the aphasic disorder considered at a communicative level, the onset time of the brain lesion or by lexical semantic disturbances. The authors suggest that one determinant is the ‘plausibility between the represented gesture and the object chosen. The plausibility factor is probably not of a linguistic nature. This interpretation is discussed in the light of earlier investigations.

Anterior cingulate and motor network metabolic impairment in progressive supranuclear palsy

Progressive supranuclear palsy is the prototype of subcortical dementia. Using positron emission tomography and statistical parametric mapping, we compared the glucose metabolic pattern obtained in this subcortical dementia to that observed in elderly healthy controls and in Alzheimers disease, the prototype of cortical dementia. Progressive supranuclear palsy was characterized by a relative decrease of metabolism in anterior cingulate, adjacent supplementary motor area, precentral cortex, middle prefrontal cortex, midbrain tegmentum, globus pallidus, and ventrolateral and dorsomedial nuclei of thalamus. The data in progressive supranuclear palsy highlight predominant metabolic impairment in brain structures engaged in response selection, in attention for action, and in motor networks.

To Be or Not to Be at Home? A Neuropsychological Approach to Delusion for Place

A woman, LB, while in recovery from a viral encephalitis, exhibited a delusion for place, which led her to insist that she was at home, in spite of compelling evidence to the contrary. Later, she developed a Capgras syndrome, that is, another misidentification syndrome. The patient was given a detailed neuropsychological evaluation to shed light on the mechanisms underlying her delusional misbelief. Two main deficits were in evidence: (1) a severe visual-spatial impairment, giving the patient a distorted perception of her surroundings; and (2) frontal lobe dysfunction, which played a critical role in her impulsive responses and lack of self-awareness. The pathogenesis of delusion for place and persons if discussed in light of these observations.

Level of agency in sub-clinical checking

This study examined cognitive representations of routine action, through the assessment of level of agency, in individuals with sub-clinical checking. The level of agency stems from Action Identification Theory [Vallacher, R. R., Wegner, D. M. (1989). Levels of personal agency: Individual variation in action identification. Journal of Personality and Social Psychology 57, 660-671], which states that how actions are usually identified (based on instrumental aspects or purpose) reflects the predominant accessibility of internal representation (movements executed vs. goal pursued). Furthermore, this framework proposed that altered action regulation is related to low-level of agency (i.e., action identification at an instrumental level). In the current study, the main result indicated that checking symptoms were related to a low-level of agency, that is, individuals with sub-clinical checking identified habitual actions on the basis of instrumental aspects. This seems to indicate that checkers may act with a lack of goal representations. The results are discussed in terms of the role of low-level of agency in checking phenomena and related cognitive dysfunction.

An Individualized and Everyday Life Approach to Cognitive Rehabilitation in Schizophrenia: A Case Illustration

Objective. The effectiveness of an individualized and everyday approach to cognitive rehabilitation for schizophrenia was examined in a case study. Method. After cognitive and functional assessment, concrete objectives were targeted for the persons everyday complaints. Strategies were constructed based on an analysis of the cognitive profile, daily life functioning, and processes involved in activities. They included a memory strategy for reading, a diary to compensate memory difficulties, and working memory exercises to improve immediate processing of information when reading and following conversations. Efficacy was assessed with outcome measures. Results. The program had beneficial effects on the persons cognitive and everyday functioning, which persisted at a 3-year follow-up. Conclusion. Findings provide suggestive evidence that an individualized and everyday approach may be a useful alternative in order to obtain a meaningfully lasting transfer of training to daily life, compared to the nomothetic ones which dominate the field.