Biomedical subjects

C Elfgren

Publications and source records attributed to C Elfgren.

5 recordsLinked to original sources

PubMed2003

Subjective experience of memory deficits related to clinical and neuroimaging findings.

The aim of this study was to evaluate cognitive impairment, psychiatric symptoms and cerebral blood flow (CBF) patterns in middle-aged (35-64 years) and younger old patients (65-74 years) with subjective experience of memory deficits. The study group was heterogeneous with patients fulfilling criteria for dementia, as well as patients with mild cognitive impairment (MCI) and with non-verified cognitive impairment (non-MCI). Seventy per cent of the non-MCI patients reported long-lasting experiences of psychosocial stress tentatively causing the memory problems. The MCI patients were subdivided into two groups: MCI type 1 included patients with isolated memory impairment, while MCI type 2 included patients with memory impairment together with slight verbal and/or visuospatial impairments. CBF measurements comparing the two MCI groups with the non-MCI group were performed. The MCI type 2 showed reduced CBF in the left anterior medial temporal lobe as well as in parts of the posterior cingulate gyrus. The CBF pattern in MCI type 2 concurs with the pathophysiological process of Alzheimer's disease. The results indicate that it is important to make a subdivision of MCI patients regarding the presence of isolated memory impairments or memory impairments together with other slight cognitive deficits.

Adult↗

PubMed1999

Learning-related effects and functional neuroimaging.

A fundamental problem in the study of learning is that learning-related changes may be confounded by nonspecific time effects. There are several strategies for handling this problem. This problem may be of greater significance in functional magnetic resonance imaging (fMRI) compared to positron emission tomography (PET). Using the general linear model, we describe, compare, and discuss two approaches for separating learning-related from nonspecific time effects. The first approach makes assumptions on the general behavior of nonspecific effects and explicitly models these effects, i.e., nonspecific time effects are incorporated as a linear or nonlinear confounding covariate in the statistical model. The second strategy makes no a priori assumption concerning the form of nonspecific time effects, but implicitly controls for nonspecific effects using an interaction approach, i.e., learning effects are assessed with an interaction contrast. The two approaches depend on specific assumptions and have specific limitations. With certain experimental designs, both approaches may be used and the results compared, lending particular support to effects that are independent of the method used. A third and perhaps better approach that sometimes may be practically unfeasible is to use a completely temporally balanced experimental design. The choice of approach may be of particular importance when learning-related effects are studied with fMRI.

Adult↗

PubMed1999

Dynamic changes in the functional anatomy of the human brain during recall of abstract designs related to practice.

In the present PET study we explore some functional aspects of the interaction between attentional/control processes and learning/memory processes. The network of brain regions supporting recall of abstract designs were studied in a less practiced and in a well practiced state. The results indicate that automaticity, i.e., a decreased dependence on attentional and working memory resources, develops as a consequence of practice. This corresponds to the practice related decreases of activity in the prefrontal, anterior cingulate, and posterior parietal regions. In addition, the activity of the medial temporal regions decreased as a function of practice. This indicates an inverse relation between the strength of encoding and the activation of the MTL during retrieval. Furthermore, the pattern of practice related increases in the auditory, posterior insular-opercular extending into perisylvian supramarginal region, and the right mid occipito-temporal region, may reflect a lower degree of inhibitory attentional modulation of task irrelevant processing and more fully developed representations of the abstract designs, respectively. We also suggest that free recall is dependent on bilateral prefrontal processing, in particular non-automatic free recall. The present results confirm previous functional neuroimaging studies of memory retrieval indicating that recall is subserved by a network of interacting brain regions. Furthermore, the results indicate that some components of the neural network subserving free recall may have a dynamic role and that there is a functional restructuring of the information processing networks during the learning process.

Adult↗

PubMed1997

A dynamic role of the medial temporal lobe during retrieval of declarative memory in man.

Understanding the role of the medial temporal lobe (MTL) in learning and memory is an important problem in cognitive neuroscience. Memory and learning processes that depend on the function of the MTL and related diencephalic structures (e.g., the anterior and mediodorsal thalamic nuclei) are defined as declarative. We have studied the MTL activity as indicated by regional cerebral blood flow with positron emission tomography and statistical parametric mapping during recall of abstract designs in a less practiced memory state as well as in a well-practiced (well-encoded) memory state. The results showed an increased activity of the MTL bilaterally (including parahippocampal gyrus extending into hippocampus proper, as well as anterior lingual and anterior fusiform gyri) during retrieval in the less practiced memory state compared to the well-practiced memory state, indicating a dynamic role of the MTL in retrieval during the learning processes. The results also showed that the activation of the MTL decreases as the subjects learn to draw abstract designs from memory, indicating a changing role of the MTL during recall in the earlier stages of acquisition compared to the well-encoded declarative memory state.

Adult↗

PubMedDate not supplied

Neuropsychological findings in frontal lobe dementia.

Neuropsychological investigations were performed on 18 patients with a clinical diagnosis of frontal lobe dementia supported by regional cerebral blood flow measurements. Nature and degree of cognitive impairment were examined with a comprehensive test battery. The results of the neuropsychological assessment could be described as three levels of cognitive impairment. The increasing levels of cognitive impairment were accompanied by corresponding levels of reduced cerebral blood flow in frontotemporal areas. No apparent relationship emerged between impairment level and illness duration, indicating a considerable individual variation in the clinical course of frontal lobe dementia.

Adult↗