Annalena Venneri

Delusions in Alzheimer's disease: spet evidence of right hemispheric dysfunction.

Delusional thinking and related behaviours are common symptoms in Alzheimers disease (AD). The aim of the study was to determine if any consistent cerebral image pattern can be identified using Tc99m-hexamethylpropyleneamine (HMPAO) SPET in AD patients with and without delusions. 18 AD patients with delusion and 15 AD patients without delusion underwent neuropsychological testing and regional cerebral blood flow imaging using Tc99m-HMPAO SPET. The reconstructed data was compared using regions of interest drawn over each cerebral lobe and a statistical parametric mapping (SPM) approach. The neuropsychological testing showed that there was no difference in the profiles of the deluded and non deluded AD patients. The imaging results showed a significant degree of image asymmetry. This took the form of a right hemisphere hypoperfusion mainly in the right frontal and limbic regions. The results do not indicate a specific focal site of hypoperfusion in the patients with delusion. They do, however, indicate that delusions in AD may be associated with areas of hypoperfusion in the right anterior hemisphere.

Walking difficulties in patients with Alzheimer’s disease might originate from gait apraxia

Objectives: To investigate whether gait apraxia is a possible cause for some of the walking abnormalities shown by patients with Alzheimer’s disease. Methods: 60 patients with Alzheimer’s disease, selected as being free from overt extrapyramidal impairment or other potential causes of walking deficits, were assessed with a new test evaluating aspects of walking and related movements. Norms for this test were collected from a sample of 182 healthy volunteers. Results: 40% of the Alzheimer group performed below the cut off score on this test, and half performed poorly. Performance of the Alzheimer group in the walking skills test correlated highly with scores in a test assessing limb apraxia and with dementia severity. Conclusions: Gait apraxia may be the cause of walking disorders found in a subgroup of patients with Alzheimer’s disease. Its detection is made easier by the use of a standardised test, but still relies heavily on the exclusion of other causes of walking deficits. It is a recognisable and independent form of apraxia.

Intra-individual measures of association in neuropsychology: Inferential methods for comparing a single case with a control or normative sample

Performance on some neuropsychological tests is best expressed as an intra-individual measure of association (such as a parametric or non-parametric correlation coefficient or the slope of a regression line). Examples of the use of intra-individual measures of association (IIMAs) include the quantification of performance on tests designed to assess temporal order memory or the accuracy of time estimation. The present paper presents methods for comparing a patients performance with a control or normative sample when performance is expressed as an IIMA. The methods test if there is a significant difference between a patients IIMA and those obtained from controls, yield an estimate of the abnormality of the patients IIMA, and provide confidence limits on the level of abnormality. The methods can be used with normative or control samples of any size and will therefore be of particular relevance to single-case researchers. A method for comparing the difference between a patients scores on two measures with the differences observed in controls is also described (one or both measures can be IIMAs). All the methods require only summary statistics (rather than the raw data from the normative or control sample); it is hoped that this feature will encourage the development of norms for tasks that use IIMAs to quantify performance. Worked examples of the statistical methods are provided using data from a clinical case and controls. A computer program (for PCs) that implements the methods is described and made available.

Brain activation and the phonological loop: The impact of rehearsal

Brain activation studies offer valuable techniques for exploring human cognition to complement behavioral measures and several studies report a wide range of neuroanatomical networks activated during verbal immediate memory. Behavioral investigations have shown use of multiple cognitive strategies across and within individuals, although aggregate data appear to reflect a common cognitive function. Variation in cognitive strategies could result in aggregate activation patterns that are relatively widespread and difficult to interpret. Imaging data (fMRI) from six participants instructed to use subvocal rehearsal showed significant left hemisphere activation in the inferior parietal gyrus and inferior and middle frontal gyri, a pattern of activation more clearly focused than in previous brain activation studies of immediate verbal serial ordered recall. Our results should be relatively free of the influence of other mental operations, and emphasise the importance of considering which cognitive strategies might give rise to focused or to diverse patterns of brain activation.

7.07 – Neuropsychological Assessment of the Elderly

7.07.9.

Persistent global amnesia following right thalamic stroke: An 11-year longitudinal study

The 11-year longitudinal study of a right-handed male patient, L. C., who suffered from a severe amnesic syndrome following a softening in the right thalamus, is reported. Memory impairment involving retrograde and long-term anterograde memory, both verbal and spatial, persisted without modification. Investigation revealed some residual implicit learning ability. Positron emission tomography studies in the resting state displayed a bilateral hypometabolism of the mesial frontal lobes. Evidence suggests that a lesion confined to the thalamus may not on its own account for severe amnesia; that involvement of other structures is necessary for severe amnesia to appear; and that a functional investigation should always be included in cases of small thalamic lesions before drawing conclusions about the structures responsible for a given deficit.

Isolated degenerative amnesia without dementia: An 8-year longitudinal study

Abstract A case of a 72-year-old patient suffering from progressive isolated memory disorders is reported. The patient has been followed up over eight years and her neuropsychological profile reveals a high standard of performance on all tests assessing Intelligence, language, praxis, attention, and short-term memory, but she fails all long-term memory tasks. MRI images showed bilateral hippocampal atrophy in the sagittal and coronal sections in the absence of white matter signal abnormalities. [18FDG] PET scan detected bilateral hypometabolism of the hippocampal regions and of the thalamus and mild metabolic reduction in the frontal area. The neuroimaging and neuropsychologlcal profiles point to a progressive amnesia of degenerative aetiology.

Transient global amnesia triggered by mild head injury

An episode of transient global memory loss was observed in a 27-year-old woman following a mild head injury in a car accident. Her clinical and neuropsychological profiles were indistinguishable from those of transient global amnesia (TGA). This paper argues that a cause-effect relationship may be postulated between head trauma and transient memory loss, perhaps as the result of a very stressful situation such as a car crash.

Memory and dating of past events in schizophrenia.

Memory deficits are frequently observed in schizophrenia but their intrinsic characteristics have not been clarified. We studied remote memory in a group of 20 schizophrenics and 20 healthy age and education matched controls using a newly devised public event questionnaire (PEQ) that employs a free recall, progressive cueing and recognition protocol and requires dating of events. Results indicate that patients with chronic schizophrenia perform significantly more poorly on the PEQ than a group of age and education matched controls both in terms of content and dating of events. The number of events recalled does not improve with progressive cuing or recognition. No distinctive pattern was observed in their temporal gradient. There was no significant difference in content scores for pre- and post-onset events in the schizophrenics. These findings indicate that remote memory deficits in chronic schizophrenics arise from deficient encoding rather than from a retrieval deficit secondary to executive dysfunction.

A Neurology of Awareness and Belief: So Near So Far?

Cognitive neuroscientists have used cognitive frameworks to interpret the various forms of breakdown in the “belief” system (e.g., misidentification, anosognosia, confabulation, asomatognosia, somatoparaphrenia, etc.) observed following focal (right) brain damage. Some cognitive theories can account for the formation of false beliefs but not for bizarre and persistent delusional states resistant to challenge. In his Target Article, Todd Feinberg has integrated psychoanalytic theory, detailed case study, and neuroscientific research knowledge to offer a synthetic account of these positive symptoms. Although they may appear superficially different, in his view in all of these disorders it is possible to detect abnormalities in some aspect of self-awareness and signs of regression to immature styles of thinking and ego functioning (e.g., denial, projection, splitting, and fantasy). One limitation of this argument is that apparently similar forms of brain damage and dysfunction do not always cause the same or even any abnormalities of belief and awareness. A way of confronting this objection, which Feinberg does not explore, is to use some variety of the cerebral reserve concept but specifically applied to cognitive reserve for the self-related functions as an individual diathesis to disorders of belief that makes the emergence of these symptoms more likely.