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Aim: Smartphone technology is increasingly used by the public to assess sleep. Specific features of some sleep-tracking applications are comparable to actigraphy in objectively monitoring sleep. The clinical utility of smartphone apps should be investigated further to increase access to convenient means of monitoring sleep. Methods: Smartphone and subjective sleep measures were administered to 29 community-dwelling healthy adults [aged 20-67, Mean (M) = 26.8; 18 women, 11 men], and actigraphy to 19 of them. Total sleep time (TST) and sleep efficiency were measured with actigraphy and the Sleep Time app (Azumio Inc.). Sleep diaries captured subjective TST and sleep efficiency, and the Epworth Sleepiness Scale and Pittsburgh Sleep Quality Index provided self-report data. An exit questionnaire was administered to examine app feasibility and likelihood of future use. Results: The app significantly overestimated TST when compared to actigraphy. There was no significant difference in sleep efficiency between methodologies. There was also no significant difference between TST recorded through the app and through sleep diaries. Participants’ self-reported ease of use of the smartphone app positively correlated with likelihood of future use. Conclusions: Based on the current findings, future research is needed to investigate the utility and feasibility of multiple smartphone applications in monitoring sleep in healthy and clinical populations.

BACKGROUND: Deficits in basic vision are associated with visual hallucinations in Parkinson's disease. Of particular interest is contrast sensitivity loss in this disorder and its effect on object identification. OBJECTIVES: Evaluate whether increased contrast improves object perception in persons with Parkinson's disease and visual hallucinations, without dementia. METHODS: We assessed 26 individuals with mild to moderate idiopathic Parkinson's disease, half of whom reported one or more episodes of hallucinations/unusual perceptual experiences in the past month, with a letter‐identification task that determined the contrast level required to achieve 80% accuracy. Contrast sensitivity was further assessed with a chart that presented stimuli at multiple spatial frequencies. The groups were closely matched for demographic and clinical characteristics except for experience of hallucinations. RESULTS: Relative to participants without visual hallucinations, those with hallucinations had poorer spatial frequency contrast sensitivity and required significantly greater contrast to correctly identify the letters on the identification task. Specifically, participants with hallucinations required a mean contrast of 52.8%, whereas participants without hallucinations required 35.0%. When given sufficient contrast, the groups with and without hallucinations were equally accurate in letter identification. CONCLUSIONS: Compared to those without hallucinations, individuals with Parkinson's disease and hallucinations without dementia showed poorer contrast sensitivity. Once contrast was individually enhanced, the groups were equally accurate at object identification. These findings suggest the potential of visual perception tests to predict, and perception‐based interventions to reduce, hallucinations in Parkinson's disease.

Objective Parkinson's disease (PD) has long been conceptualized as a motor disorder, but nonmotor symptoms also manifest in the disease and significantly reduce quality of life. Anxiety and cognitive dysfunction are prevalent nonmotor symptoms, even in early disease stages, but the relation between these symptoms remains poorly understood. We examined self-reported anxiety and neurocognitive function, indexed by measures of executive function (set-shifting and phonemic fluency), categorical fluency, and attention/working memory. We hypothesized that anxiety would correlate with cognitive performance. Method The Beck Anxiety Inventory and cognitive tests (Trail Making, Verbal Fluency, Digit Span) were administered to 77 nondemented adults with mild to moderate idiopathic PD (39 men, 38 women; Mage = 62.9 years). Results Higher anxiety was associated with more advanced disease stage and severity and with poorer set-shifting when using a derived metric to account for motoric slowing. Depression correlated with greater anxiety and disease severity, but not with cognitive performance. Conclusions Our findings support the association of anxiety with a specific domain of executive function, set-shifting, in nondemented individuals with mild to moderate PD, raising the possibility that treatment of anxiety may alleviate aspects of executive dysfunction in this population. (PsycINFO Database Record

Spatial judgment is impaired in Parkinson's disease (PD), with previous research suggesting that disruptions in attention and executive function are likely contributors. If judgment of center places demands on frontal systems, performance on tests of attention/executive function may correlate with extent of bias in PD, and attentional disturbance may predict inconsistency in spatial judgment. The relation of spatial judgment to attention/executive function may differ for those with left-side versus right-side motor onset (LPD, RPD), reflecting effects of attentional lateralization. We assessed 42 RPD, 37 LPD, and 67 healthy control participants with a Landmark task (LM) in which a cursor moved horizontally from the right (right-LM) or left (left-LM). The task was to judge the center of the line. Participants also performed neuropsychological tests of attention and executive function. LM group differences were found on left-LM only, with both PD subgroups biased leftward of the control group (RPD p < .05; LPD p < .01; no RPD-LPD difference). For left-LM trials, extent of bias significantly correlated with performance on the cognitive tasks for PD but not for the control group. PD showed greater variability in perceived center than the control group; this variability correlated with performance on the cognitive tasks. The correlations between performance on the test of spatial judgment and the tests of attention/executive function suggest that frontal-based attentional dysfunction affects dynamic spatial judgment, both in extent of spatial bias and in consistency of response as indexed by intertrial variability. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Objective:To investigate the relation between orthostatic hypotension (OH) and posture-mediated cognitive impairment in Parkinson disease (PD) using a cross-sectional and within-group design.Methods:Individuals without dementia with idiopathic PD included 18 with OH (PDOH) and 19 without OH; 18 control participants were also included. Neuropsychological tests were conducted in supine and upright-tilted positions. Blood pressure was assessed in each posture.Results:The PD groups performed similarly while supine, demonstrating executive dysfunction in sustained attention and response inhibition, and reduced semantic fluency and verbal memory (encoding and retention). Upright posture exacerbated and broadened these deficits in the PDOH group to include phonemic fluency, psychomotor speed, and auditory working memory. When group-specific supine scores were used as baseline anchors, both PD groups showed cognitive changes following tilt, with the PDOH group exhibiting a wider range of deficits in executive function and memory as well as significant changes in visuospatial function.Conclusions:Cognitive deficits in PD have been widely reported with assessments performed in the supine position, as seen in both our PD groups. Here we demonstrated that those with PDOH had transient, posture-mediated changes in excess of those found in PD without OH. These observed changes suggest an acute, reversible effect. Understanding the effects of OH due to autonomic failure on cognition is desirable, particularly as neuroimaging and clinical assessments collect data only in the supine or seated positions. Identification of a distinct neuropsychological profile in PD with OH has quality of life implications, and OH presents itself as a possible target for intervention in cognitive disturbance.

Objective To examine the feasibility and efficacy of a home-based gait observation intervention for improving walking in Parkinson disease (PD). Design Participants were randomly assigned to an intervention or control condition. A baseline walking assessment, a training period at home, and a posttraining assessment were conducted. Setting The laboratory and participants' home and community environments. Participants Nondemented individuals with PD (N=23) experiencing walking difficulty. Intervention In the gait observation (intervention) condition, participants viewed videos of healthy and parkinsonian gait. In the landscape observation (control) condition, participants viewed videos of moving water. These tasks were completed daily for 8 days. Main Outcome Measures Spatiotemporal walking variables were assessed using accelerometers in the laboratory (baseline and posttraining assessments) and continuously at home during the training period. Variables included daily activity, walking speed, stride length, stride frequency, leg swing time, and gait asymmetry. Questionnaires including the 39-item Parkinson Disease Questionnaire (PDQ-39) were administered to determine self-reported change in walking, as well as feasibility. Results At posttraining assessment, only the gait observation group reported significantly improved mobility (PDQ-39). No improvements were seen in accelerometer-derived walking data. Participants found the at-home training tasks and accelerometer feasible to use. Conclusions Participants found procedures feasible and reported improved mobility, suggesting that observational training holds promise in the rehabilitation of walking in PD. Observational training alone, however, may not be sufficient to enhance walking in PD. A more challenging and adaptive task, and the use of explicit perceptual learning and practice of actions, may be required to effect change.

The effects of age on the ability to resolve perceptual ambiguity are unknown, though it depends on frontoparietal attentional networks known to change with age. We presented the bistable Necker cube to 24 middle-aged and OAs (older adults; 56-78 years) and 20 YAs (younger adults; 18-24 years) under passive-viewing and volitional control conditions: Hold one cube percept and Switch between cube percepts. During passive viewing, OAs had longer dominance durations (time spent on each percept) than YAs. In the Hold condition, OAs were less able than YAs to increase dominance durations. In the Switch condition, OAs and YAs did not differ in performance. Dominance durations in either condition correlated with performance on tests of executive function mediated by the frontal lobes. Eye movements (fixation deviations) did not differ between groups. These results suggest that OAs' reduced ability to hold a percept may arise from reduced selective attention. The lack of correlation of performance between Hold and executive-function measures suggests at least a partial segregation of underlying mechanisms.

Veering while walking is often reported in individuals with Parkinson's disease (PD), with potential mechanisms being vision-based (asymmetrical perception of the visual environment) or motoric (asymmetry in stride length between relatively affected and non-affected body side). We examined these competing hypotheses by assessing veering in 13 normal control participants (NC) and 20 non-demented individuals with PD: 9 with left-side onset of motor symptoms (LPD) and 11 with right-side onset (RPD). Participants walked in a corridor under three conditions: eyes-open, egocentric reference point (ECRP; walk toward a subjectively perceived center of a target at the end of the corridor), and vision-occluded. The visual hypothesis predicted that LPD participants would veer rightward, in line with their rightward visual-field bias, whereas those with RPD would veer leftward. The motor hypothesis predicted the opposite pattern of results, with veering toward the side with shorter stride length. Results supported the visual hypothesis. Under visual guidance, RPD participants significantly differed from NC, veering leftward despite a shorter right- than left-stride length, whereas LPD veered rightward (not significantly different from NC), despite shorter left- than right-stride length. LPD participants showed significantly reduced rightward veering and stride asymmetry when they walked in the presence of a visual landmark (ECRP) than in the eyes-open condition without a target. There were no group differences in veering in the vision-occluded condition. The findings suggest that interventions to correct walking abnormalities such as veering in PD should incorporate vision-based strategies rather than solely addressing motor asymmetries, and should be tailored to the distinctive navigational profiles of LPD and RPD.

Parkinson’s disease (PD) and normal aging have been associated with changes in visual perception, including reliance on external cues to guide behavior. This raises the question of the extent to which these groups use visual cues when disambiguating information. Twenty-seven individuals with PD, 23 normal control adults (NC), and 20 younger adults (YA) were presented a Necker cube in which one face was highlighted by thickening the lines defining the face. The hypothesis was that the visual cues would help PD and NC to exert better control over bistable perception. There were three conditions, including passive viewing and two volitional-control conditions (hold one percept in front; and switch: speed up the alternation between the two). In the Hold condition, the cue was either consistent or inconsistent with task instructions. Mean dominance durations (time spent on each percept) under passive viewing were comparable in PD and NC, and shorter in YA. PD and YA increased dominance durations in the Hold cue-consistent condition relative to NC, meaning that appropriate cues helped PD but not NC hold one perceptual interpretation. By contrast, in the Switch condition, NC and YA decreased dominance durations relative to PD, meaning that the use of cues helped NC but not PD in expediting the switch between percepts. Provision of low-level cues has effects on volitional control in PD that are different from in normal aging, and only under task-specific conditions does the use of such cues facilitate the resolution of perceptual ambiguity. (JINS, 2015, 21, 146–155)

We thank Guaraldi et al. for their comment on our article,1 and for drawing our attention to their work assessing cognitive function in patients with peripheral autonomic disorders, pure autonomic failure (PAF), and autoimmune autonomic neuropathy.2 The results in their study are similar to our results in Parkinson disease (PD),2 and to data we reported earlier on reversible cognitive impairment in individuals with orthostatic hypotension (OH) due to the peripheral disorder autoimmune autonomicganglionopathy.3 Cognitive changes in all of these studies are most significant in the domains of attention and executive functioning; while disease-specific decrements vary across each participant group regardless of posture, the totality of these data strongly suggest an independent effect of OH that may go unnoticed during standard clinical assessment. This is perhaps most relevant for PD, where the management focus tends to be on motor features and OH may be unrecognized whereas dysautonomic signs are prioritized in autoimmune autonomic ganglionopathy, autonomic neuropathies, and PAF. All these studies highlight the need for clinical awareness of cognitive impairment in association with OH, and for additional work to delineate the pathophysiologic mechanisms underlying OH-induced cognitive impairment.1–3

Cognitive deficits are common in Parkinson's disease (PD) and exacerbate the functional limitations imposed by PD's hallmark motor symptoms, including impairments in walking. Though much research has addressed the effect of dual cognitive-locomotor tasks on walking, less is known about their effect on cognition. The purpose of this study was to investigate the relation between gait and executive function, with the hypothesis that dual tasking would exacerbate cognitive vulnerabilities in PD as well as being associated with gait disturbances.Nineteen individuals with mild-moderate PD without dementia and 13 age- and education-matched normal control adults (NC) participated. Executive function (set-shifting) and walking were assessed singly and during dual tasking.Dual tasking had a significant effect on cognition (reduced set-shifting) and on walking (speed, stride length) for both PD and NC, and also on stride frequency for PD only. The impact of dual tasking on walking speed and stride frequency was significantly greater for PD than NC. Though the group by condition interaction was not significant, PD had fewer set-shifts than NC on dual task. Further, relative to NC, PD showed significantly greater variability in cognitive performance under dual tasking, whereas variability in motor performance remained unaffected by dual tasking.Dual tasking had a significantly greater effect in PD than in NC on cognition as well as on walking. The results suggest that assessment and treatment of PD should consider the cognitive as well as the gait components of PD-related deficits under dual-task conditions. (PsycINFO Database Record

Objective Anxiety is commonly endorsed in Parkinson's disease (PD) and significantly affects quality of life. The Beck Anxiety Inventory (BAI) is often used but contains items that overlap with common PD motor symptoms (e.g., “hands trembling”). Because of these overlapping items, we hypothesized that PD motor symptoms would significantly affect BAI scores. Methods One hundred non-demented individuals with PD and 74 healthy control participants completed the BAI. PD motor symptoms were assessed by the Unified Parkinson's Disease Rating Scale (UPDRS). Factor analysis of the BAI assessed for a PD motor factor, and further analyses assessed how this factor affected BAI scores. Results BAI scores were significantly higher for PD than NC. A five-item PD motor factor correlated with UPDRS observer-rated motor severity and mediated the PD-control difference on BAI total scores. An interaction occurred, whereby removal of the PD motor factor resulted in a significant reduction in BAI scores for PD relative to NC. The correlation between the BAI and UPDRS significantly declined when controlling for the PD motor factor. Conclusions The results indicate that commonly endorsed BAI items may reflect motor symptoms such as tremor instead of, or in addition to, genuine mood symptoms. These findings highlight the importance of considering motor symptoms in the assessment of anxiety in PD and point to the need for selecting anxiety measures that are less subject to contamination by the motor effects of movement disorders.

Objectives: Parkinson’s disease (PD) is associated with deficits in social cognition and visual perception, but little is known about how the disease affects perception of socially complex biological motion, specifically motion-defined communicative and non-communicative gestures. We predicted that individuals with PD would perform more poorly than normal control (NC) participants in discriminating between communicative and non-communicative gestures, and in describing communicative gestures. We related the results to the participants’ gender, as there are gender differences in social cognition in PD. Methods: The study included 23 individuals with PD (10 men) and 24 NC participants (10 men) matched for age and education level. Participants viewed point-light human figures that conveyed communicative and non-communicative gestures and were asked to describe each gesture while discriminating between the two gesture types. Results: PD as a group were less accurate than NC in describing non-communicative but not communicative gestures. Men with PD were impaired in describing and discriminating between communicative as well as non-communicative gestures. Conclusions: The present study demonstrated PD-related impairments in perceiving and inferring the meaning of biological motion gestures. Men with PD may have particular difficulty in understanding the communicative gestures of others in interpersonal exchanges. (JINS, 2016, 22, 1–11)

External support may improve task performance regardless of an individual’s ability to compensate for cognitive deficits through internally-generated mechanisms. We investigated if performance of a complex, familiar visual search task (the game of bingo) could be enhanced in groups with suboptimal vision by providing external support through manipulation of task stimuli. Participants were 19 younger adults, 14 individuals with probable Alzheimer’s disease (AD), 13 AD-matched healthy adults, 17 non-demented individuals with Parkinson’s disease (PD), and 20 PD-matched healthy adults. We varied stimulus contrast, size, and visual complexity during game play. The externally-supported performance interventions of increased stimulus size and decreased complexity resulted in improvements in performance by all groups. Performance improvement through increased stimulus size and decreased complexity was demonstrated by all groups. AD also obtained benefit from increasing contrast, presumably by compensating for their contrast sensitivity deficit. The general finding of improved performance across healthy and afflicted groups suggests the value of visual support as an easy-to-apply intervention to enhance cognitive performance.

Visual perceptual problems are common in Parkinson's disease (PD) and often affect activities of daily living (ADLs). PD patients with non-tremor symptoms at disease onset (i.e., rigidity, bradykinesia, gait disturbance or postural instability) have more diffuse neurobiological abnormalities and report worse non-motor symptoms and functional changes than patients whose initial symptom is tremor, but the relation of motor symptom subtype to perceptual deficits remains unstudied. We assessed visual ADLs with the Visual Activities Questionnaire in 25 non-demented patients with PD, 13 with tremor as the initial symptom and 12 with an initial symptom other than tremor, as well as in 23 healthy control participants (NC). As expected, the non-tremor patients, but not the tremor patients, reported more impairment in visual ADLs than the NC group, including in light/dark adaptation, acuity/spatial vision, depth perception, peripheral vision and visual processing speed. Non-tremor patients were significantly worse than tremor patients overall and on light/dark adaptation and depth perception. Environmental enhancements especially targeted to patients with the non-tremor PD subtype may help to ameliorate their functional disability.

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.

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. Language: en

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.

Emotion identification appears to decline with age, and deficient visual scanning may contribute to this effect. Eye movements of 20 older adults (OAs) and 20 younger adults (YAs) with normal saccades were recorded while viewing facial expressions. OAs made fewer fixations overall, and they made a higher proportion of fixations to the lower halves of faces. Topographical distribution of fixations predicted better OA accuracy for identifying disgust than other negative emotions. Impaired OA accuracy for fear and anger was specific to vision, with normal identification of these emotions in the auditory domain. Age-related frontal-lobe atrophy may affect the integrity of the frontal eye fields, with consequent scanning abnormalities that contribute to difficulties in identifying certain emotions.

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.

Background/Objectives: Visuospatial problems are common in Parkinson’s disease (PD) and likely stem from dysfunction in dopaminergic pathways and consequent disruption of cortical functioning. Characterizing the motor symptoms at disease onset provides a method of observing how dysfunction in these pathways influences visuospatial cognition. We examined two types of motor characteristics: Body side (left or right) and type of initial symptom (tremor or symptom other than tremor). Methods: 31 non-demented patients with PD, 16 with left-side onset (LPD) and 15 with right-side onset (RPD), as well as 17 healthy control participants (HC). The PD group was also divided by type of initial motor symptom, 15 having tremor as the initial symptom and 16 having an initial symptom other than tremor. Visuospatial function was assessed with the Clock Drawing Test. Results: Of the four Clock Drawing scoring methods used, the Rouleau method showed sensitivity to subgroup differences. As predicted, the LPD and non-tremor subgroups, but not the other subgroups, performed more poorly than the HC group. Conclusion: The findings provide further evidence for differences in cognition between these subtypes of PD and highlight the importance of considering disease subtypes when examining cognition.

Deficits in visual cognition in Alzheimer's disease (AD) arise from neuropathological changes in higher-order association areas of the cortex and from defective input from lower-level visual processing areas. We investigated whether enhanced signal strength may lead to improvement of visual cognition in AD. We tested 35 individuals with probable AD, 35 age-matched elderly control (EC) and 58 young control (YC) adults on letter identification, word reading, picture naming, discrimination of unfamiliar faces, and pattern completion. The contrast sensitivity step-difference across an independent sample of AD and EC groups was used in calculating an image filter, from which we produced stimulus-strength conditions of low-degraded, medium-normal, and high-enhanced. Using this filter we created a hypothetical proximal-strength equivalence between AD at medium strength and EC at low strength, and between AD at high strength and EC at medium strength. For letter identification, word reading, picture naming, and face discrimination, medium strength elicited AD accuracy levels and reaction times that were similar to those of EC at low strength. On picture naming, increased strength reduced perceptual-type errors for EC and AD and random errors for AD. For word reading, high strength elicited AD accuracy levels and reaction times that were equivalent to those of EC at medium strength. We saw no effect of signal-strength manipulation on performance of pattern completion, possibly owing to the complex cognitive demands of that task or to the inadequacy of the filter for its images. The results indicate that putative AD-EC differences in cognition directly reflect contrast sensitivity differences between the groups. Enhancement of stimulus strength can ameliorate vision-based deficits and lead to improvement in some aspects of cognitive performance. These results suggest new non-pharmacological avenues to explore in the attempt to improve cognition in elderly adults and especially in individuals with AD.

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.

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.