Neuropsychologic profile of a high-functioning family with a mitochondrial cytopathy.

OBJECTIVE: To examine the neuropsychologic profile of 3 family members diagnosed with the same mitochondrial cytopathy corresponding to a defect in the respiratory chain. BACKGROUND: The neuropsychologic functioning of patients with mitochondrial cytopathies has been largely unexamined in the literature. These mitochondrial defects often result in cell death and the failure of whole systems, including the brain. There are over 40 known types of mitochondrial cytopathies, which vary greatly in their genetic, clinical, and behavioral manifestations. METHOD: The following project describes the neuropsychologic profiles of a family (a mother and her 2 children) afflicted by the same mitochondrial cytopathy possibly associated with nucleotide 15,924. Standardized tests of premorbid intelligence estimation, attention, executive function, language, verbal and visual memory, visuospatial functioning, motor functioning, visual acuity, mood, and activities of daily living were administered. RESULTS: Participants' profiles were characterized by estimated intellectual ability in the average to superior range with marked variability on a number of assessments, making it difficult to identify a distinct pattern. General trends, however, were reflective of executive function impairment associated with dysfunction of frontal-subcortical systems. CONCLUSIONS: Mitochondrial disorders are extremely complicated and variable in their presentation. A multifactor approach should be adopted when examining neuropsychologic profiles.

The neuropsychologic deficits of MELAS: evidence of global impairment.

OBJECTIVE: To examine the neuropsychologic profile of MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis, and strokelike episodes) and relate it to neuropathologic findings. BACKGROUND: MELAS is one of over 40 mitochondrial disorders. Symptoms include seizures, strokelike episodes, headaches, memory impairment, hemianopsia, hearing loss, short stature, diffuse limb weakness, exercise intolerance, nausea, and vomiting. Age of onset ranges from 2 to 40 years. A hallmark of MELAS is normal development until the first symptoms appear. METHOD: Because information regarding the neuropsychologic functioning of these individuals is sparse, we report findings from detailed neuropsychologic evaluations for a 13-year-old white male and a 33-year-old African-American male with MELAS. RESULTS: Results revealed global patterns of deterioration in executive function, attention, language, memory, visuospatial, and motor functioning. In both patients, brain scans revealed posterior pathology in the absence of frontal pathology. CONCLUSIONS: We compared our findings with other documented cases and concluded that MELAS is characterized by a pattern of global deterioration. This pattern differs from that observed in other mitochondrial disorders. The absence of identifiable frontal lobe pathology despite the presence of deficits in executive functioning may be related to the distribution patterns of deficient mitochondria and neuronal projection patterns.

Characteristics of visual target influence detection of change in naturalistic scenes in Alzheimer disease.

OBJECTIVE: To examine the role of visual characteristics of the target on Alzheimer disease (AD) patients' ability to detect change in naturalistic scenes. BACKGROUND: AD patients exhibit impairments in detecting changes in the visual environment. Unexamined to date is the influence of visual characteristics of the target on this ability. METHOD: The change-detection experiment used 36 pairs of photographs of naturalistic scenes. Each pair was identical except for one target that differed in color, gray-scale, or presence/absence. Scene complexity also varied. The task was to locate the target; reaction times (RTs) were recorded. RESULTS: RTs increased as scene complexity increased. AD patients exhibited slower RTs than elderly adult controls (ECs), who were slower than young adults (N = 14/group). AD patients were unable to locate the target in 33.3% to 61.9% of the complex gray-scale trials, compared with 4.8% to 38.1% in the EC group. Performance on color and presence/absence trials was relatively good for all groups. CONCLUSIONS: The ability of AD patients to detect change in simulated real-world scenes is influenced by visual characteristics of the target and by scene complexity.

Enhanced stimulus contrast normalizes visual processing of rapidly presented letters in Alzheimer's disease.

Deficient perception and cognition in Alzheimer's disease (AD) has been attributed to slow information processing and attentional disturbance, but an additional explanation may be reduced signal strength. In 21 individuals with probable AD, 29 healthy older and 54 younger adults, we enhanced the contrast level of rapidly-flashed masked letters. The AD group reached identification criterion (80% accuracy), but required significantly higher contrast than the control groups. A source of the prevalent masking deficit may be reduced signal strength arising from dysfunction of retina or visual cortex. Increasing stimulus contrast may be an effective means of enhancing cognitive performance in AD.

Visual contrast enhances food and liquid intake in advanced Alzheimer's disease.

BACKGROUND & AIMS: Patients with severe Alzheimer's disease (AD) in long-term care have deficient contrast sensitivity and poor food and liquid intake. The present study examined how contrast manipulations affect these intake levels. METHODS: Participants were nine men with advanced AD. Independent variables were meal type (lunch and supper) and condition (baseline, intervention, and post-intervention). Dependent variables were amount of food (grams) and liquid (ounces). Data were collected for 30 days (10 days per condition) for two meals per day. White tableware was used for the baseline and post-intervention conditions, and high-contrast red tableware for the intervention condition. In a follow-up study 1 year later, other contrast conditions were examined (high-contrast blue, low-contrast red and low-contrast blue). RESULTS: Mean percent increase was 25% for food and 84% for liquid for the high-contrast intervention (red) versus baseline (white) condition, with 8 of 9 participants exhibiting increased intake. In the follow-up study, the high-contrast intervention (blue) resulted in significant increases in food and liquid intake; the low-contrast red and low-contrast blue interventions were ineffectual. CONCLUSIONS: Simple environmental manipulations, such as contrast enhancement, can significantly increase food and liquid intake in frail demented patients with AD.

The impact of acuity on performance of four clinical measures of contrast sensitivity in Alzheimer's disease.

Investigations of contrast sensitivity losses in Alzheimer's disease (AD) have yielded mixed findings, with some investigators reporting deficits and others not. Potential reasons for these discrepancies include differences between samples and assessments utilized and the failure of some investigators to account for acuity differences between groups. To investigate these issues, we administered four clinical contrast sensitivity assessments to the same group of AD patients and elderly control participants and examined the impact of acuity on performance for each assessment. Results revealed group differences across the spatial frequency range. Further, group acuity differences significantly affected performance on two of the four measures (the Regan and the Vistech but not on the Pelli-Robson or Freiburg assessments). Information regarding the availability of established age norms, test-retest reliability data, and other factors including the time, cost, and training needed to administer each measure is provided to aid clinicians and researchers in their search for an effective measure of contrast sensitivity.