Abstract Many studies have shown relative preservation of word priming in subjects with mild amnesia, but some impairment 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 a 70-year-old woman with transient global amnesia. This subject was examined during her attack as well as 8 months after. She was tested for word priming on a speeded category membership decision task. Implicit or explicit encoding procedures were used in three different experiments. Results indicated that there was no significant difference between the priming effects measured in the implicit and explicit conditions or between the priming effects measured during and after the transient global amnesia attack. Results also confirmed 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 amnesia. These findings demonstrate that word priming is preserved during transient global amnesia. They also suggest that the capacity to encode, store and retrieve information implicitly, e.g. unintentionally, is retained in this neurological condition.
Neural stem cells and progenitors in the developing brain must choose between proliferation with renewal and differentiation. Defects in navigating this choice can result in malformations or cancers, but the genetic mechanisms that shape this choice are not fully understood. We show by positional cloning that the 30-zinc finger transcription factor Zfp423 (OAZ) is required for patterning the development of neuronal and glial precursors in the developing brain, particularly in midline structures. Mutation of Zfp423 results in loss of the corpus callosum, reduction of hippocampus, and a malformation of the cerebellum reminiscent of human Dandy-Walker patients. Within the cerebellum, Zfp423 is expressed in both ventricular and external germinal zones. Loss of Zfp423 results in diminished proliferation by granule cell precursors in the external germinal layer, especially near the midline, and abnormal differentiation and migration of ventricular zone-derived neurons and Bergmann glia.
Mobility decline is a symptom of advanced dementia that impacts function, safety, caregiving, and quality of life. The causes of mobility decline in dementia are multi-factorial, including cognitive, physical, and neurological changes. Many of these factors are progressive in nature, leading to a loss of independent mobility and increased numbers of falls. Monitoring mobility status is essential for preventing excess disability in people with dementia however, the cognitive and behavioral symptoms of dementia present unique challenges for mobility assessment. The goals of this review were to identify and describe existing measures of mobility for people with dementia and to determine their feasibility for use in advanced stages of the disease. Electronic searches of Medline, Embase, CINAHL and PsychInfo databases were conducted using key words related to dementia, mobility, measurement, and validation. Descriptive characteristics (e.g. tool purpose, type, reporting method, number of items) were extracted and measures coded for elements of mobility targeted. Study features such as setting and disease severity were also charted. Tools were evaluated for feasibility of use in advanced dementia according to practical details including the need for communication, attention, motivation, and complex motor skills. Tools deemed feasible were screened for psychometric strength. 38 measures were included. 36% of studies included people with advanced dementia. 68% of tools were performance-based. Elements of mobility evaluated were walking (53% of measures), postural transitions (42%), standing (40%), mobility-related behavioral/psychological symptoms (24%), transfers (10%), bed mobility (5%) and wheeled mobility (3%). Only 18% of tools received high scores for feasibility. Four of the 14 tools screened for psychometric strength showed both good reliability and good external validity. Existing measures provide only partial information regarding mobility and few target elements that become relevant as dementia progresses. Most tools are not feasible for individuals with advanced dementia and the psychometric evaluation of these tools is limited. More work is needed to develop a comprehensive, dementia-specific, assessment tool that considers the unique symptoms of dementia. Importantly, such a tool should be designed to identify transitions in mobility through the progression of the disease.
Abstract Basic activities of daily living (ADL) are self-maintenance abilities such as dressing or bathing. Instrumental ADL (IADL) are more complex everyday tasks, such as preparing a meal or managing finances (Lawton & Brody, 1969 Lawton, M. P. and Brody, E. M. 1969. Assessment of older people: Self-maintaining and instrumental activities of daily living. Gerontologist, 9: 179–186. [Crossref], [PubMed], [Web of Science ®] , [Google Scholar]). IADL questionnaires play an important role in assessing the functional abilities of older adults and evaluating the impact of cognitive impairment on routine activities. This paper examined the cognitive processes that underlie IADL performance and concluded that the accurate and reliable execution of IADL likely draws upon the integrity of a wide range of cognitive processes. This review examined IADL in mild cognitive impairment (MCI) because of the controversial nature of distinguishing a significant decline in functional abilities in those with MCI versus dementia or MCI versus cognitively normal aging. The challenges of investigating IADL empirically were explored, as well as some of the reasons for the inconsistent findings in the literature. A review of questionnaire-based assessments of IADL indicated that: MCI can be distinguished statistically from healthy older adults and dementia, individuals with multiple domain MCI are more impaired on IADL than those with single domain MCI, mild IADL changes can be predictive of future cognitive decline, and the ability to manage finances may be among the earliest IADL changes in MCI and a strong predictor of conversion to dementia. This paper concluded with recommendations for more sensitive and reliable IADL questionnaires. Keywords: Mild cognitive impairmentInstrumental activities of daily livingCognitive correlates of everyday functioningPrediction of future declineAssessment and classification Acknowledgments This work was supported by doctoral awards from the Natural Science and Engineering Research Council and the Ontario Graduate Scholarship in Science and Technology.
