Protocol for the Brain Health Support Program Study of the Canadian Therapeutic Platform Trial for Multidomain Interventions to Prevent Dementia (CAN-THUMBS UP): A Prospective 12-Month Intervention Study

BACKGROUND/OBJECTIVES

CAN-THUMBS UP is designed as a comprehensive and innovative fully remote program to 1) develop an interactive and compelling online Brain Health Support Program intervention, with potential to positively influence dementia literacy, self-efficacy and lifestyle risk factors; 2) enroll and retain a community-dwelling Platform Trial Cohort of individuals at risk of dementia who will participate in the intervention; 3) support an open platform trial to test a variety of multidomain interventions that might further benefit individuals at risk of dementia. This manuscript presents the Brain Health Support Program Study protocol.

DESIGN/SETTING

Twelve-month prospective multi-center longitudinal study to evaluate a fully remote web-based educational intervention. Participants will subsequently be part of a Platform Trial Cohort and may be eligible to participate in further dementia prevention clinical trials.

PARTICIPANTS

Three hundred fifty older adults who are cognitively unimpaired or have mild cognitive impairment, with at least 1 well established dementia risk factor.

INTERVENTION

Participants engage in the Brain Health Support Program intervention for 45-weeks and complete pre/post intervention measures. This intervention is designed to convey best available evidence for dementia prevention, consists of 181 chapters within 8 modules that are progressively delivered, and is available online in English and French. The program has been developed as a collaborative effort by investigators with recognized expertise in the program's content areas, along with input from older-adult citizen advisors.

MEASUREMENTS

This study utilizes adapted remote assessments with accessible technologies (e.g. videoconferencing, cognitive testing via computer and mobile phone, wearable devices to track physical activity and sleep, self-administered saliva sample collection). The primary outcome is change in dementia literacy, as measured by the Alzheimer's Disease Knowledge Scale. Secondary outcomes include change in self-efficacy; engagement using the online program; user satisfaction ratings; and evaluation of usability and acceptance. Exploratory outcomes include changes in attitudes toward dementia, modifiable risk factors, performance on the Neuropsychological Test Battery, performance on self-administered online cognitive assessments, and levels of physical activity and sleep; success of the national recruitment plan; and the distribution of age adjusted polygenic hazard scores.

CONCLUSIONS

This fully remote study provides an accessible approach to research with all study activities being completed in the participants' home environment. This approach may reduce barriers to participation, provide an easier and less demanding participant experience, and reach a broader geography with recruitment from all regions of Canada. CAN-THUMBS UP represents a Canadian contribution to the global World-Wide FINGERS program (alz.org/wwfingers).

An Action Plan to Face the Challenge of Dementia: INTERNATIONAL STATEMENT ON DEMENTIA from IAP for Health

An international committee set up through the IAP for Health met to develop an action plan for dementia. Comprehensive international and national initiatives should move forward with calls for action that include increased public awareness regarding brain health and dementia, support for a broad range of dementia research objectives, and investment in national health care systems to ensure timely competent person-centred care for individuals with dementia. The elements of such action plans should include: 1) Development of national plans including assessment of relevant lifecourse risk and protective factors; 2) Increased investments in national research programs on dementia with approximately 1% of the national annual cost of the disease invested; 3) Allocating funds to support a broad range of biomedical, clinical, and health service and systems research; 4) Institution of risk reduction strategies; 5) Building the required trained workforce (health care workers, teachers, and others) to deal with the dementia crisis; 6) Ensuring that it is possible to live well with dementia; and 7) Ensuring that all have access to prevention programs, care, and supportive living environments.

Progressive supranuclear palsy in a family with TDP-43 pathology

A member of a family with an autosomal dominant pattern of frontotemporal dementia (FTD) with a TDP-43 pathological substrate in other members and no mutations in FTD-associated genes developed behavioral variant FTD followed by Progressive Supranuclear Palsy. Autopsy revealed a pure tauopathy of PSP pattern.

CONCLUSIONS

The findings raise the possibility of shared pathogenic pathways and a proximal genetic abnormality between PSP and FTLD-43.

The semantic category effect increases with worsening anomia in Alzheimer's type dementia

A large number of patients (n=72) with probable Alzheimer's type dementia (DAT) and mild cognitive impairment (MCI) carried out a picture naming task which comprised stimuli from biological and nonbiological categories. The results were stratified into five ranges of overall naming ability. Every group except those with scores within the range of elderly normal individuals demonstrated better nonbiological naming than biological naming, an effect which increased with worsening impairment. In general, patients diagnosed with other dementia (n=15) did not fit well within the pattern of the DAT/MCI participants, except those known to have a significant semantic impairment. A category effect favoring nonbiological items appears to be robust and produce a predictable pattern across progressive levels of impairment in AD.

Dissociable brain regions process object meaning and object structure during picture naming

Although imaging studies have indicated that the fusiform gyrus is important in tasks of picture naming, whether this region encodes an object's structure or its meaning is not clear. We used positron emission tomography to examine cerebral blood flow (CBF) changes in response to a picture naming task that varied on two dimensions: familiarity (or difficulty: hard vs easy) and category (tools vs animals). Results show that although familiarity effects are present in the frontal and left lateral posterior temporal cortex, they are absent from the fusiform gyrus. This provides strong evidence that the processing carried out in the fusiform gyrus relates to an object's structure, not to its meaning, and that the left posterior middle temporal gyrus instantiates in part the semantic network that represents the object's meaning.

Normal optic nerve head topography in the early stages of dementia of the Alzheimer type

In view of the existing controversy as to whether or not the optic nerve head (ONH) is altered in Alzheimer disease, we used modern imaging technology to evaluate the ONH structure in individuals with dementia of the Alzheimer type (DAT). Real-time topographical images of the ONH were obtained with a Heidelberg retina tomograph from individuals in the early stages of DAT and age-matched controls. The various ONH parameters examined in this study did not differ significantly between DAT and age-matched subjects. These results suggest that the deficits in visual function that are known to occur in DAT are not related to ONH structural anomalies, at least in the earlier stages of the disease.

The spectrum of category effects in object and action knowledge in dementia of the Alzheimer's type

The validity and origin of category effects in the anomia demonstrated by individuals with dementia of the Alzheimer's type (DAT) remains controversial. Twenty DAT subjects were tested with picture naming and semantic association judgment tests. Picture and word stimuli were drawn from biological, nonbiological, and actions-verbs categories, all of equal difficulty and previously normed on elderly controls. DAT subjects made significantly more naming and semantic judgment errors in the biological category than in the nonbiological category. They were relatively more accurate in naming and making judgments for actions-verbs when presented as words or as 5-s animations. When line drawings of actions were shown for naming, performance deteriorated significantly. Converging results from these 2 tasks provide strong evidence for a semantic memory impairment preferentially affecting biological items to a greater extent than nonbiological items or action verbs in DAT.

Neuroretinal function is normal in early dementia of the Alzheimer type

We recently demonstrated that retinal ganglion cell function, optic nerve head parameters and the retinal nerve fiber layer thickness are not altered in early dementia of the Alzheimer type (DAT). Our current objective was to assess whether the function of cells located more distally in the retina is also unaffected by the disease. We evaluated 23 individuals with early to moderate DAT and 23 healthy age-matched subjects, all displaying clinically normal visual function. Scotopic and photopic flash electroretinograms (fERGs) and oscillatory potentials (OPs) were recorded. The amplitude and latency of the retinal potentials did not differ between DAT and control subjects. Our current results showing normal fERGs and OPs in early DAT indicate that the underlying neurons giving rise to these signals are not impaired by the disease process. These data support and extend our recent findings suggesting that visual deficits in DAT do not stem from neuroretinal dysfunction.

The impact of semantic impairment on word stem completion in Alzheimer's disease

Both the extent of semantic memory impairment and the level of processing attained during encoding might constitute critical factors in determining the amount of word-stem completion (WSC) priming encountered in Alzheimer's disease (AD) subjects. We investigated the impact of varying encoding level in AD and elderly normal subjects, using a set of stimuli ranked as "intact" or "degraded" in terms of each subject's semantic knowledge on probe questions. For both shallow and deep encoding conditions, overall priming in the two subject groups was equivalent. However, for the deep encoding condition, consisting of a semantic judgment task performed on each target word, the priming effect noted in AD subjects was significantly smaller for semantically degraded items than for semantically intact items. Results indicate that the degree of semantic impairment represents one important variable affecting the amount of WSC priming which results when deep encoding procedures are used at study.

An evaluation of the retinal nerve fiber layer thickness by scanning laser polarimetry in individuals with dementia of the Alzheimer type

PURPOSE

To determine, using scanning laser polarimetry, whether or not the retinal nerve fiber layer (RNFL) is altered in dementia of the Alzheimer type (DAT).

METHODS

Thirty individuals with mild to moderate DAT and 30 healthy age-matched controls participated in the study. Fundus images were acquired with a Nerve Fiber Analyzer. RNFL thickness measurements were obtained under an ellipse located 1.75 disc diameter from the optic nerve head (ONH) center.

RESULTS

No differences in RNFL thickness were observed between DAT and healthy subjects. The regional distribution of RNFL thickness was similar between the two test groups, with the RNFL being thickest in the superior and inferior retinal segments relative to the nasal and temporal regions.

CONCLUSIONS

Our data indicate that the RNFL is not altered in DAT, at least in the earlier stages of the disease.

Recommendations of the Canadian Consensus Conference on Dementia--dissemination, implementation, and evaluation of impact

BACKGROUND

Subsequent to the development of consensus statements on a clinical topic, it is vital to establish a plan for dissemination, implementation and evaluation of impact. Consensus statements can be used for both guiding continuing medical education (CME) and producing clinical practice guidelines (CPGs). Insufficient attention to dissemination can lead to a failure to change physician behaviour and improve patient outcomes.

METHODS

A plan to disseminate the conclusions of the Canadian Consensus Conference on Dementia (CCCD) was developed. This plan was based on a literature review of CME and CPGs. A Medline search was performed on the dissemination and evaluation of the 1989 Canadian Consensus Conference on the Assessment of Dementia (CCCAD) and other published guides for physicians on dementia care. CCCD dissemination that has occurred to date (June, 2000) was reviewed in this paper.

RESULTS

Lectures and unsolicited printed material are weak forms of CME. Small-group interactive CME that provides practice opportunities appears to be the most effective way to change physician behaviour. The ability of CPGs to change physician behaviour is uncertain. It appears that inadequate attention has been placed on CPG dissemination and implementation. The CCCAD had a modest impact on clinical practice in Canada. While dissemination of the conclusions of the CCCD has taken place, evaluation of the impact of the CCCD has yet to be done. Local initiatives utilizing the conclusions of the CCCD are on-going.

CONCLUSIONS

Further work is needed on how to optimize the impact of consensus statements and CPGs. While dissemination of the CCCD has occurred, it is currently unknown whether it has led to any change in physician practices.

Assessment of suspected dementia

At the Second Canadian Consensus Conference on Dementia (CCCD) (February, 1998), a group of neurologists, geriatricians, and psychiatrists met to consider guidelines for evaluation of dementia in Canada. This review paper formed a background paper for their discussion of dementia diagnosis. These experts from across the country concluded that diagnosis of suspected dementia cases continued to rest on skilled clinical assessment. Mental status exam, preferably in some quantifiable form, has become an essential part of the assessment. Selected laboratory tests are advisable in all cases (CBC, TSH, electrolytes, calcium, and glucose), but the CCCD continued to advise that CT scanning was mandatory only in selected cases where clinical findings pointed to another possibility besides Alzheimer's disease. The growing list of other diagnostic measures with potential usefulness in diagnosis of Alzheimer's disease or dementia in general was reviewed, but the evidence was judged as insufficient to support routine use of these tests by physicians. As new treatments for Alzheimer's disease become available, neurologists face new diagnostic challenges--differentiating Mild Cognitive Impairment, Frontotemporal dementias and Mixed dementias, and Lewy Body Dementia. Guidelines to aid in differential diagnosis are presented.

Pattern of semantic memory impairment in dementia of Alzheimer's type

The specific pattern of semantic memory impairment in patients with dementia of Alzheimer's type (DAT) remains unclear. Specifically, the presence of a category-specific deficit for biological concepts (reflected in anomia for these concepts) has been questioned. We studied 9 DAT patients using a semantic association judgement test in which they had to decide which of the two given words was most like a target word (e.g., lamb: goat, sheep). The 150 target words were drawn from 6 categories: animals, clothing and furniture, fruits and vegetables, tools, action verbs, and abstract nouns. Age- and education-matched control subjects performed equivalently (between 86 and 90% correct) in all categories. Compared to control subjects, DAT patients made significantly more errors in abstract and biological nouns, but not in verbs and man-made artifacts. This pattern of semantic memory impairment--a sparing of verbs and a selective deficit of nouns in the biological category--has been documented in patients with temporal lobe damage, suggesting a critical dysfunction in the temporal lobes of DAT.

Evaluation of heme oxygenase-1 as a systemic biological marker of sporadic AD

BACKGROUND

Heme oxygenase-1 (HO-1) is a 32-kDa stress protein that catalyzes the degradation of heme to biliverdin. HO-1 immunoreactivity is greatly increased in neurons and astrocytes of the hippocampus and cerebral cortex of individuals with AD and colocalizes to senile plaques and neurofibrillary tangles.

METHODS

We investigated whether systemic HO-1 regulation is also deranged in AD patients and whether blood HO-1 measurements provide a peripheral biomarker of the disease. Plasma HO-1 protein levels were measured by competitive ELISA and lymphocyte HO-1 mRNA levels were determined by Northern analysis in patients with early probable sporadic AD, normal elderly controls (NEC), normal younger controls, individuals with age-associated cognitive decline (AACD) not meeting AD criteria, and patients with non-Alzheimer dementia, nondementing neurologic illness, and chronic medical disorders. CSF HO-1 protein concentrations were also determined by ELISA in pathologically confirmed AD and control cases.

RESULTS

Mean plasma HO-1 protein concentrations were significantly lower in AD patients (0.85 +/- 0.14 microg/mL) compared with NEC (1.77 +/- 0.34 microg/mL; p < 0.05) and control patients. The AACD group exhibited plasma HO-1 concentrations (1.06 +/- 0.33 microg/mL) intermediate between, but not different from, those of the AD patients and NEC. Lymphocyte HO-1 mRNA levels were lower in the AD cohort relative to NEC (p < 0.001) and individuals with AACD, non-Alzheimer dementia, nondementing neurologic illness, and chronic medical conditions. Lymphocyte HO-1 mRNA levels were also lower in the AACD group relative to NEC (p < 0.05). In comparison with all groups excluding AACD, the sensitivity and specificity of lymphocyte HO-1 mRNA measurement for diagnosis of early sporadic AD are 88% and 75%. Mean CSF HO-1 protein concentrations were lower (p < 0.01) in AD cases (19.07 ng/mL) relative to control values (32.48 ng/mL).

CONCLUSIONS

Plasma and CSF HO-1 protein and lymphocyte HO-1 mRNA levels are decreased in subjects with sporadic AD. Quantitative assay for lymphocyte HO-1 mRNA expression may serve as a useful biologic marker in early sporadic AD.

The neural substrate of picture naming

A PET study of 10 normal males was carried out using the bolus H215O intravenous injection technique to examine the effects of picture naming and semantic judgment on blood flow. In a series of conditions, subjects (1) passively viewed flashing plus signs, (2) noted the occurrence of abstract patterns, (3) named animal pictures, or (4) carried out a semantic judgment on animal pictures. Anticipatory scans were carried out after the subjects were presented with the instructions but before they began the cognitive task, as they were passively viewing plus signs. Our results serve to clarify a number of current controversies regarding the neural substrate of picture naming. The results indicate that the fusiform gyrus is unlikely to be the region where low-level perceptual processing such as shape analysis is undertaken. In fact, our evidence suggests that activation of the fusiform gyrus is most likely related to visual perceptual semantic processing. In addition, the inferior/middle frontal lobe activity observed while performing the picture naming and semantic judgment tasks does not appear to be due to the effects of anticipation or preparation. Furthermore, there appears to be a set of regions (a semantic network) that becomes activated regardless of whether the subjects perform a picture naming or semantic judgment task. Finally, picture naming of animals did not activate either parietal regions or anterior inferior left temporal regions, regardless of what subtraction baseline was used.

Object identification deficits in dementia of the Alzheimer type: combined effects of semantic and visual proximity

Identification deficits in dementia of the Alzheimer Type (DAT) often target specific classes of objects, sparing others. Using line drawings to uncover the etiology of such category-specific deficits may be untenable because the underlying shape primitives used to differentiate one line drawing from another are unspecified, and object form is yoked to object meaning. We used computer generated stimuli with empirically specifiable properties in a paradigm that decoupled form and meaning. In Experiment 1 visually similar or distinct blobs were paired with semantically close or disparate labels, and participants attempted to learn these pairings. By having the same blobs stand for semantically close and disparate objects and looking at shape-label confusion rates for each type of set, form and meaning were independently assessed. Overall, visual similarity of shapes and semantic similarity of labels each exacerbated object confusions. For controls, the effects were small but significant. For DAT patients more substantial visual and semantic proximity effects were obtained. Experiment 2 demonstrated that even small changes in semantic proximity could effect significant changes in DAT task performance. Labeling 3 blobs with "lion," "tiger," and "leopard" significantly elevated DAT confusion rates compared to exactly the same blobs labeled with "lion," "tiger," and "zebra." In conclusion both visual similarity and semantic proximity contributed to the identification errors of DAT patients.

Word priming without awareness: A new approach to circumvent explicit memory contamination

A major methodological limitation arising in the experimental study of implicit memory is that tasks that are characterized as implicit memory tests can be seriously contaminated by the use of covert explicit memory strategies. Given the evidence indicating that brief presentation of words (below the awareness threshold of subjects) can produce semantic priming, we wondered whether rapid visual presentation of primed words might provide an avenue to produce word priming without explicit memory contamination. Normal subjects were tested for word priming on a speeded category membership decision task. Explicit or implicit encoding procedures were used in four different experiments. Results demonstrated that brief presentation of words can indeed offer a means of producing word priming in absence of explicit recognition or recall of the primed words presented during the study phase. They also showed that such priming is equivalent in degree to the priming measured when using either a conventional implicit memory design or an explicit encoding procedure prior to the study of the primes.

Lack of prognostic significance of SPECT abnormalities in non-demented elderly subjects with memory loss

OBJECTIVE

To determine if hypoperfusion abnormalities on single photon emission computed tomography (SPECT) are associated with poorer cognitive function at baseline or increased risk of decline in cognitive function and progression to dementia in memory-impaired but non-demented elderly subjects meeting the criteria for aging associated cognitive decline (AACD).

DESIGN

Cross sectional study of 36 AACD subjects comparing hexamethyl propylene-amine oxime (HMPAO) SPECT results rated by visual inspection with base line cognitive functioning. Prospective study of these AACD subjects with clinical and neuropsychological follow-up over 35 months.

SETTING

The memory clinic and nuclear medicine unit of a university teaching hospital.

SUBJECTS

Thirty-six subjects meeting the criteria for AACD recruited from patients seen on a physician referral basis.

MAIN OUTCOME MEASURES

1) Baseline cognitive function as measured by the Mini Mental State Examination (MMSE), Boston naming, Logical Memory I subtest of the WAIS-R, and verbal fluency, correlated with SPECT status. 2) Decline in cognitive function as measured by clinical exam and the MMSE, with progression to dementia on follow-up being correlated with SPECT status at baseline.

RESULTS

18 of the 36 subjects progressed to dementia (probable Alzheimer's Disease) over follow-up. No correlation was found between the presence or absence of SPECT abnormality and MMSE or other cognitive measures. There was no correlation between the presence or absence of SPECT abnormality at initial examination, and cognitive decline according to the MMSE, or with the occurrence of clinical dementia on follow-up.

CONCLUSIONS

We conclude that SPECT abnormalities assessed by visual inspection do not correlate with severity of impairment in AACD individuals, and are not useful in predicting progression to dementia in AACD subjects.

Prevalence of potentially reversible dementias and actual reversibility in a memory clinic cohort

BACKGROUND

Although clinics for the evaluation of cognitive dysfunction have typically emphasized the detection and treatment of the reversible causes of dementia, it remains unclear whether the treatment of such causes results in reversal of the dementia. Therefore, the appropriate work-up for dementia is in dispute.

METHODS

A chart review was performed with records from an urban tertiary care referral-based memory clinic. The records for 196 patients with dementia or suspected dementia, seen between October 1991 and December 1993, were examined to determine the prevalence of potentially reversible dementias and whether the cognitive dysfunction improved or resolved after treatment. Data abstracted from the medical charts included demographic information, medication use, presence of depression, and results of neuropsychological tests, blood work and neuroimaging. The clinical diagnosis, the response to treatment, if applicable, and the outcome (mean follow-up period 16 months) were analysed. The recommendations of the 1989 Canadian Consensus Conference on the Assessment of Dementia (CCCAD) on the use of CT were retrospectively applied in each case.

RESULTS

Of the 196 patients, 45 (23.0%) had a potentially reversible condition identified by history, physical examination, blood testing or CT; in only 7 (3.6% of the total) did treatment result in improvement or resolution of the dementia. These 7 patients had higher results for the Mini-Mental State examination (mean result 26) and exhibited only mild cognitive deficits. Potentially reversible lesions were found in the CT scans of 6 (3.1%) patients: 4 had normal-pressure hydrocephalus and 2 had a brain tumour. If the CCCAD recommendations had been followed, CT would have been performed in 76 (38.8%) of the patients, and 1 of the 6 patients with a lesion would have been missed.

INTERPRETATION

Both potential and actual reversibility of dementia was low in these memory clinic patients. The patients whose condition improved with intervention had early and milder cognitive deficits, which suggests that thorough evaluation of early memory loss is warranted.

A role for the hippocampal formation in implicit memory: a 3-D PET study

The apparent preservation of word priming effects in amnesia has been interpreted as supporting the view that implicit memory depends on brain systems that are independent of mesial temporal lobe structures which are in part responsible for explicit memory disorders. Nevertheless, a number of studies have demonstrated word priming deficits in amnesic patients relatively to normal subjects, suggesting that such structures may also be involved in implicit memory. To determine whether one such structure, the hippocampal formation, is a component of the brain system subserving word priming, a 3-D PET study was carried out in 13 normal individuals. Encoding was carried out using the brief multiple presentation technique, a procedure that allows one to effectively circumvent contamination of implicit memory tasks by explicit memory strategies. Results revealed that word priming was indeed associated with an activation of the right hippocampal formation. This finding of an hippocampal involvement in word priming calls into question the notion of absolute dissociability between the brain systems underlying performance on various explicit and implicit memory tasks.

The Neural Substrate for Concrete, Abstract, and Emotional Word Lexica A Positron Emission Tomography Study

Viewing of single words produces a cognitively complex mental state in which anticipation, emotional responses, visual perceptual analysis, and activation of orthographic representations are all occurring. Previous PET studies have produced conflicting results, perhaps due to the conflation of these separate processes or the presence of subtle differences in stimulus material and methodology. A PET study of 10 normal individuals was carried out using the bolus H2 15O intravenous injection technique to examine components of processing of passively viewed words. Subjects viewed blocks of random-letter strings or abstract, concrete, or emotional words (words with positive or negative emotional salience). Baseline conditions were either passive viewing of plus signs or an anticipatory state (viewing plus signs after being warned to expect words or random letters to appear imminently). All words (and to a lesser extent the random letters) produced robust activation of cerebral blood flow in the left posterior temporal lobe, in addition to bilateral occipital activation. Furthermore, emotional words produced activation in orbital and midline frontal structures. Further activation in the left orbital frontal gyrus, the left inferior temporal gyrus, the left caudate nucleus, the anterior cingulate, and the cerebellum could be ascribed to the anticipatory state. This pattern of activity suggests that the occipital regions are recruited for visual-perceptual analysis of words, and the left temporal lobe represents the neural substrate for the orthographic lexicon. In addition, emotionally relevant material produces further processing in limbic brain structures of the frontal lobes. Detailed analysis of the task therefore substantially clarifies the neuroanatomic basis of single-word processing.

On the status of object concepts in aphasia

While verbal comprehension is often impaired in aphasia due to left hemispheric damage, the status of nonverbal conceptual knowledge of objects remains controversial. We tested 16 aphasic subjects for their comprehension of concrete single words. Eight showed significant impairment on word-to-picture matching, when distractors were semantically and not just perceptually confusable. These 8 also made errors in answering verbal probe questions concerning the same items. When tested on a nonverbal pictorial version of the same probe questions, however, 3 of these 8 improved their performance to the level of normal controls. The other 5 showed continuing impairment in indicating responses to pictorial probes. These 5 showed no evidence of generalized intellectual impairment, and it is concluded that they demonstrated a comprehension deficit not limited to the verbal domain. Unlike the other aphasic patients, these latter 5 also had CT scan lesions extending into the posterior left temporal lobe (involving Brodmann's areas 22, 21, and 37). They were also more impaired in terms of general aphasia severity. It is suggested that a nonverbal (as well as verbal) semantic memory deficit occurs in a subgroup of patients with single word comprehension disturbance due to aphasia, and this may reflect general severity of language impairment as well as damage to certain localized brain regions.

Word priming with brief multiple presentation technique: preservation in amnesia

Many studies have shown relative preservation of word priming in subjects with mild amnesia, but some decrease in severe amnesia. This calls into question the degree of separation between implicit and explicit memory. Possible contamination of implicit memory tasks by impaired explicit memory strategies might be obscuring the actual dissociation between the two memory systems. We have developed a method of circumventing explicit memory contamination by using brief duration repeated primes below the awareness threshold of subjects. We have used this approach to evaluate the status of word priming in densely amnesic subjects. One group of amnesic subjects with alcoholic Korsakoff's syndrome and one group of normal elderly control subjects were tested for word priming on a speeded category membership decision task. Implicit or explicit encoding procedures were used in three different experiments. Results demonstrated that brief multiple presentation of words can offer a means of producing word priming in the absence of explicit recognition or recall of the primed words in both amnesic subjects and normal elderly control subjects. Moreover, there was no significant difference in the magnitude of the priming effect between these groups in the three experiments. These findings show that amnesic subjects can exhibit normal levels of word priming. They also suggest that amnesics retain the capacity to encode, store and retrieve information implicity, e.g. unintentionally.

PET activation and language

Brain activation studies using positron emission tomography (PET) to study language have produced a breakthrough in our understanding of the neural basis of language over the past decade. A neural basis for the visual lexicon and for auditory verbal short term memory components have been proposed. Wernicke's and Broca's areas are being recast in terms of localized components of phonological input and output. Some classical regions, such as the arcuate fasciculus, are having their "classical" roles questioned, while other regions, such as the basal temporal language zone, are growing progressively in terms of their recognized importance. Finally, other areas, such as the anterior cingulate and the left inferior prefrontal area, seem to be activated across a range of tasks, but their exact processing roles remain a matter of some debate.

HM-PAO (CERETEC) SPECT brain scanning in the diagnosis of Alzheimer's disease

OBJECTIVE

To evaluate the accuracy of Single Photon Emission Computed Tomography (SPECT) scanning in the diagnosis of Alzheimer's Disease (AD) and its capacity to improve the diagnostic accuracy of conventional clinical evaluation.

DESIGN

Comparison of SPECT scanning of AD and normal subjects with the criterion standard of clinical diagnosis confirmed by 1-year repeated evaluation.

SETTING

A memory clinic in a tertiary care university hospital.

PATIENTS

One hundred twenty patients were evaluated upon entering the Jewish General Hospital (McGill University) Memory Clinic. Fifty-eight patients were diagnosed as having AD and 17 as having vascular dementia. Twenty unmatched controls (recruited mainly through newspaper advertisements) were normal, and 25 had cognitive impairment without dementia (not included in the statistical analysis).

MAIN OUTCOME MEASURES

Comparison of visual inspection of SPECT, based on the system of classification developed by Holman et al., using B pattern alone as positive or B (bilateral posterior temporal and/or parietal cortex deficits) or C (bilateral posterior temporal and/or parietal deficits with additional defects) pattern and B or C or D (unilateral posterior temporal and/or parietal defects with or without additional defects) as positive compared with clinical diagnosis after repeated evaluations. Sensitivity and specificity, as well as positive predictive value (PPV) and negative predictive value (NPV) based on the prevalence of AD in a memory clinic setting of 30% or 50%, were calculated.

RESULTS

With B pattern as positive, the sensitivity of SPECT was 21% whereas the specificity was 80%. With B or C as positive, the sensitivity was 29% and the specificity was 75%. With B or C or D as positive, the sensitivity was 55% and the specificity was 65%. With a 30% prevalence, the PPV with B pattern as positive was 31% whereas the NPV was 30%. The PPV with B or C as positive was 33% while the NPV was 29%, and the PPV with B or C or D as positive was 40% whereas the NPV was 23%. With a 50% prevalence, the PPV with B pattern as positive was 51% and the NPV 49.6%; the PPV with B or C as positive was 54% and the NPV 48.6%; the PPV with B or C or D as positive was 61% while NPV was 41%.

CONCLUSION

The sensitivity and specificity were too low for SPECT to be useful as a diagnostic test for AD. The poor positive and negative predictive values in our tertiary care clinic mean that SPECT is not useful in "ruling-in" or "ruling-out" AD in that setting. In fact, clinical evaluation is more accurate.

Absence of mutations in superoxide dismutase and catalase genes in patients with Parkinson's disease

BACKGROUND

Parkinson's disease (PD) is an adult-onset, neurodegenerative disorder characterized by a selective loss of the dopaminergic cells of the substantia nigra and by progressive motor decline. Studies have shown aberrant oxidative stress metabolism within the substantia nigra and other dopaminergic regions of the brain in patients with PD.

OBJECTIVE

To screen the genes of three free radical detoxifying enzymes--copper/zinc superoxide dismutase, manganese superoxide dismutase, and catalase--for mutations in patients with PD.

PATIENTS AND METHODS

A total of 107 unrelated patients with PD from two PD populations (familial and sporadic) were screened for mutations in the genes of copper/zinc superoxide dismutase, manganese superoxide dismutase, and catalase by single-strand conformation analysis. The diagnosis of PD was based on the clinical observations of resting tremor, rigidity, and bradykinesia.

RESULTS

No mutations were identified. However, we did identify an amino acid substitution (glycine to aspartic acid) in exon 9 of the catalase gene in one patient; decreased red blood cell catalase activity was observed in this patient.

CONCLUSION

Parkinson's disease is not caused by mutations in the genes of these three detoxifying enzymes. The exon 9 variant in the catalase gene in the one family with PD is most likely a silent mutation and not the genetic cause of PD in this family.

Increased semantic priming in patients with dementia of the Alzheimer's type

Semantic priming on a lexical decision task(LDT) was examined in 50 patients with mild to moderate dementia of the Alzheimer's Type(DAT), and 25 normal age-matched controls. DAT patients were slower in their responses, and showed significantly greater priming effects (mean 54 ms vs. 27 ms in controls). The size of the priming effect correlated with the speed of response on the LDT task for the individual DAT patients but not for controls. Twenty of the DAT patients (vs. one control) showed priming greater than 60 ms. This subgroup of DAT patients with "hyperpriming" was slower than the nonhyperpriming group on "yes" responses to targets preceded by unassociated prime words and more impaired on tests of clock drawing and verbal fluency. Slowing of responses alone, however, seems unable to account for the presence of increased priming in DAT patients. Its presence may reflect semantic memory deficits, as well as impaired attentional processing and supervisory control systems. The exact mechanism of this increased priming remains to be established.

Influence of affective words on lexical decision task in major depression

In cognitive science, lexical decision task is used to investigate visual word recognition and lexical access. The issue of whether or not individuals who are depressed differ in their access to affectively laden words and specifically to words that have negative affect was examined. Based on some aspects of the Resource Allocation Model (Ellis), it was postulated that patients suffering from depression take more time to recognize items from an affective-loaded list. In order to compare their behavior in a lexical decision task, patients suffering from depression and healthy controls were studied. We hoped to find an interaction between the mood state of subjects and the categories (affective or neutral) of words. Two groups of right-handed adults served as subjects in our experiment. The first group consisted of 11 patients suffering from depression (mean age: 40.2; sd: 6.8). All of this group met the DSM-III-R and the Research Diagnostic Criteria for major depressive disorder. Severity of their disease was rated using the 24-item Hamilton Depressive Rating Scale. All patients suffering from depression were without psychotropic medication. The control group was composed of 24 subjects (mean age: 32.7; sd: 7.9). A depressive word-list and a neutral word-list were built and a computer was used for the lexical-decision task. A longer reaction time to detect the non-word stimuli (F1,33 = 11.19, p < 0.01) was observed with the patients by comparison to the normal subjects. In the analysis of the word stimuli, a group by list interaction (F1,33 = 7.18, p < 0.01) was found.(ABSTRACT TRUNCATED AT 250 WORDS)

Semantic memory loss in dementia of Alzheimer's type. What do various measures measure?

This paper examines three methodological issues concerning the measurement of semantic memory impairment in brain-damaged patients. Ten carefully selected patients with dementia of Alzheimer's type (DAT) and anomia were studied. A battery of perceptual tests and direct tests of semantic memory led to the conclusion that these patients represented a homogeneous group having a prominent deterioration of their semantic memory store without visual perceptual deficits. The first issue addressed in this patient group was whether verbal fluency impairment accurately reflected the loss of semantic memory. It was found that verbal fluency (generation of semantic category lists) was impaired due to two major constraints: deterioration of semantic memory store, and variable difficulties in semantic search. Verbal fluency, therefore, reflects semantic memory loss to some degree, but is not a direct test of semantic memory store in DAT. The second issue was whether semantic memory impairment in our patients conformed to the 'semantic storage disorder' syndrome hypothesized by Shallice (1987). It was shown that, consistent with this hypothesis, the patients demonstrated co-occurrence of consistency of errors, loss of semantic cueing, and preserved superordinate knowledge with loss of detailed knowledge of concept items. The third issue was whether semantic cueing and semantic priming are altered in a similar manner in DAT. It demonstrated that semantic cueing and semantic priming, using the same words whose concepts were degraded in semantic memory, yielded an entirely different pattern of results. Cueing and priming therefore may not be used interchangeably in the study of semantic loss after brain damage.