The effect of symptom duration on cognitive and motor performance in parkinsonism

Clinical utility of DaTscan in patients with suspected Parkinsonian syndrome: a systematic review and meta-analysis

Images of DaTscan (ioflupane [123I] SPECT) have been used as an adjunct to clinical diagnosis to facilitate the differential diagnosis of neurodegenerative (ND) Parkinsonian Syndrome (PS) vs. non-dopamine deficiency aetiologies of Parkinsonism. Despite several systematic reviews having summarised the evidence on diagnostic accuracy, the impact of imaging results on clinical utility has not been systematically assessed. Our objective was to examine the available evidence on the clinical utility of DaTscan imaging in changing diagnosis and subsequent management of patients with suspected PS. We performed a systematic review of published studies of clinical utility from 2000 to 2019 without language restrictions. A meta-analysis of change in diagnosis and management rates reported from each study was performed using a random-effects model and logit transformation. Sub-group analysis, meta-regression and sensitivity analysis was performed to explore heterogeneity. Twenty studies met the inclusion criteria. Thirteen of these contributed to the meta-analyses including 950 and 779 patients with a reported change in management and change in diagnosis, respectively. The use of DaTscan imaging resulted in a change in management in 54% (95% CI: 47-61%) of patients. Change in diagnosis occurred in 31% (95% CI: 22-42%) of patients. The two pooled analyses were characterised by high levels of heterogeneity. Our systematic review and meta-analysis show that imaging with DaTscan was associated with a change in management in approximately half the patients tested and the diagnosis was modified in one third. Regardless of time from symptom onset to scan results, these changes were consistent. Further research focusing on specific patient subgroups could provide additional evidence on the impact on clinical outcomes.

Is mercury in Tibetan Medicine toxic? Clinical, neurocognitive and biochemical results of an initial cross-sectional study

Mercury an important therapeutic substance in Tibetan Medicine undergoes complex "detoxification" prior to inclusion in multi-ingredient formulas. In an initial cross-sectional study, patients taking Tibetan Medicine for various conditions were evaluated for mercury toxicity. Two groups were identified: Group 1, patients taking " Tsothel" the most important detoxified mercury preparation and Group 2, patients taking other mercury preparations or mercury free Tibetan Medicine. Atomic fluorescence spectrometry of Tibetan Medicine showed mercury consumption 130 µg/kg/day (Group 1) and 30 µg/kg/day (Group 2) ( P ≤ 0.001), levels above EPA (RfDs) suggested threshold (0.3 µg/kg /day) for oral chronic exposure. Mean duration of Tibetan Medicine treatment was 9 ± 17 months (range 3-116) (Group 1) and 5 ± 1.96 months (range 1-114) (Group 2) (NS) with cumulative days of mercury containing Tibetan Medicine, 764 days ± 1214 (range 135-7330) vs. 103 days ± 111 (range 0-426), respectively ( P ≤ 0.001). Comparison of treatment groups with healthy referents (Group 3) not taking Tibetan Medicine showed no significant differences in prevalence of 23 non-specific symptoms of mercury toxicity, abnormal neurological, cardiovascular and dental findings and no correlation with mercury exposure variables; consumption, cumulative treatment days, blood/ urine Hg. Liver and renal function tests in treatment groups were not significantly increased compared to referents, with mean urine Beta₂ Microglobulin within the normal range and not significantly associated with Hg exposure variables after correcting for confounding variables. Neurocognitive testing showed no significant intergroup differences for Wechsler Memory Scale, Grooved Pegboard, Visual Retention, but Group1 scores were better for Mini-Mental, Brief Word Learning, Verbal Fluency after correcting for confounding variables. These results suggest mercury containing Tibetan Medicine does not have appreciable adverse effects and may exert a possible beneficial effect on neurocognitive function. Since evidence of mercury as a toxic heavy metal, however, is well known, further analysis of literature on mercury use in other Asian traditional systems is highly suggested prior to further studies.

Hypertension and cognitive function

Previous research indicates that blood pressure may impact a variety of cognitive functions, including short-term memory, abstract reasoning, visual-spatial abilities, and attention (Boller, Vrtunski, Mack, & Kim, 1977; Elias, Robbins, Schultz, & Pierce, 1990; Franceschi, Tancredi, Smirne, Mercinelli, & Canal, 1982; Mazzucchiet al., 1986). However, studies which have assessed the cognitive functioning of hypertensive adults have offered conflicting results, particularly when hypertension levels were in the mild range (e.g., Bolleret al., 1977; Eliaset al., 1990; Elias, Wolf, D'Agostino, Cobb, & White, 1993; Farmeret al., 1987, 1990; Franceschiet al., 1982; Pérez-Stable, Coates, Halliday, Gardiner, & Hauck, 1992; Schmidtet al., 1991; Waldstein, Ryan, Manuck, Parkinson, & Bromet, 1991). A number of factors may contribute to the inconsistent findings in this area. Researchers have employed a wide range of neuropsychological instruments to assess varying domains of cognitive function. Sample sizes in some studies have been too small to ensure sufficient power. Finally, studies have employed varying methodological control over potential confounding factors such as concurrent medical conditions, alcohol abuse, psychiatric disorders, or antihypertensive medication. This study compared male veterans with blood pressures in the mildly hypertensive range (n=166) to normotensive veterans (n=176) on neuropsychological measures of verbal fluency, visual-spatial ability, verbal and visual memory, dexterity, attention, and executive functions. Results revealed that, after controlling for differences in education and income, there was no relationship between mild hypertension and combined measures of cognitive performance. The present findings suggest that mild hypertension alone has little effect on cognitive function in adults.

Virtual reality environment for simulating tasks with a myoelectric prosthesis: an assessment and training tool

Intuitively and efficiently controlling multiple degrees of freedom is a major hurdle in the field of upper limb prosthetics. A virtual reality myoelectric transhumeral prosthesis simulator has been developed for cost-effectively testing novel control algorithms and devices. The system acquires EMG commands and residual limb kinematics, simulates the prosthesis dynamics, and displays the combined residual limb and prosthesis movements in a virtual reality environment that includes force-based interactions with virtual objects. A virtual Box and Block Test is demonstrated. Three normally-limbed subjects performed the simulated test using a sequential and a synchronous control method. With the sequential method, subjects moved on average 6.7±1.9 blocks in 120 seconds, similar to the number of blocks transhumeral amputees are able to move with their physical prostheses during clinical evaluation. With the synchronous method, subjects moved 6.7±2.2 blocks. The virtual reality prosthesis simulator is thus a promising tool for developing and evaluating control methods, prototyping novel prostheses, and training amputees.

Prose memory in patients with idiopathic Parkinson's disease

BACKGROUND

The findings of previous studies have suggested that verbal memory impairments were observed in people suffering from Parkinson's disease (PD). Very few studies have examined the comprehensive profile of prose memory deficits that challenges people with PD.

METHODS

Prose memory of 19 patients with PD was examined. Their performance in three constructs, namely recall accuracy, temporal sequence, and distortions, during immediate, delayed and recognition trials was studied.

RESULTS

The patients with PD performed significantly worse in recall accuracy and temporal sequencing of information in the immediate recall trial. During the recognition trial, they made more false alarms than their healthy counterparts.

CONCLUSIONS

Our findings confirm that the performance of people with PD in immediate recall of a prose was impaired. However, the level of performance in subsequent learning and delayed recall trials became comparable to that of the normal controls. The deficit remaining after multiple learning trials was the significantly high false alarms committed in the recognition trial. Our findings highlight the importance of qualitative analysis, in addition to quantitative evaluation, of prose memory in PD.

Neuropsychological deficits in patients with chronic fatigue syndrome

The degree of neuropsychological dysfunction across multiple domains was examined in individuals suffering from chronic fatigue syndrome (CFS). In this descriptive study, a similar series of neuropsychological tests was administered to a group of CFS patients and healthy participants. More specifically, CFS patients (n = 141) who met the 1994 Case Definition criteria were compared to 76 healthy control participants on tests of memory, attention (concentration), speed of information processing, motor speed, and executive functioning. On the 18 measures administered, CFS patients scored 1 standard deviation below the healthy mean on nine measures and scored 2 standard deviations below the healthy mean on four of the measures. Moreover, results indicated that CFS patients were more likely than healthy controls to fail (1.6 SD below the healthy mean) at least one test in each of the following domains: attention, speed of information processing, and motor speed, but not on measures of memory and executive functioning. Finally, CFS patients demonstrated a greater total number of tests failed across domains.

Spatial behaviour is driven by proximal cues even in mildly impaired Parkinson's disease

This investigation addresses the question whether patients with mild to moderate Parkinson's disease (PD) show spatial deficits in real-life settings. Therefore, a "search through"-locomotor task incorporating basic features of both the radial arm maze and the Morris water maze paradigms was used. The participants had to find and remember five out of twenty hidden locations within a completely controlled environment. Different spatial memory errors and inter-response intervals were recorded automatically. Fourteen patients with idiopathic PD and fourteen healthy controls matched for age, sex, handedness, and education were investigated. Patients and controls were widely comparable with respect to intelligence, verbal memory, and executive functions. Results show that performance deteriorated in about half of the patients if the starting position was moved by 90 degrees and the proximal cues were deleted simultaneously. This deficit was systematically related to specific measures of attention. Moreover, patients were less able to update their locomotor strategies towards a more effective strategy. Results are discussed with respect to the patient's inability to generate rules which can be flexibly used in changing environments, especially if proximal cues are removed. It is concluded that deficits in spatial behaviour can be elicited even in near-to-real-life situations if appropriate testing procedures are used.

Validity of the Dementia Rating Scale in assessing cognitive function in Parkinson's disease

Two studies examined the validity of the Dementia Rating Scale (DRS) as a measure of cognitive functioning among patients with Parkinson's disease (PD). The DRS accounted for more variation in the level of cognitive functioning of PD patients than either the Mini-Mental Status Examination or a battery of tests selected to assess specific cognitive deficits associated with PD. Further, DRS subtests displayed strong convergent and discriminant validity with a comprehensive Criterion Neuropsychology Battery. The DRS subtests appear to be valid measures of attention, perseveration, conceptualization, and memory among PD patients. However, the DRS-Construction subtest should be supplemented with additional visuoconstructional items to provide a thorough screen of cognitive functioning in PD. Although about three-quarters of nondemented PD patients did not appear to have any specific cognitive deficits on the DRS, the remaining patients were impaired on the Construction or Initiation/Perseveration subtests of the DRS. In summary, the DRS is a valid mental status screening test of cognitive functioning for individuals with PD.

Outcome of chronic opioid therapy for non-cancer pain

Potential iatrogenic mood and cognitive declines associated with long-acting opioid therapy were examined in 19 patients receiving long-acting oral opioid medications and compared to ten patients receiving usual care. Pain, mood, and cognitive function were measured before and after achieving stable doses. In addition to reducing pain, long-acting opioid medication reduced anxiety and hostility. No declines in cognitive function were associated with the long-acting opioid medications, and the group receiving long-acting opioid medications showed significant improvement on a measure of psychomotor speed and sustained attention. Both patient groups reported significant reductions in perceived impairment in daily activities due to pain. Treatment responders taking long-acting opioid medications (63%) were taking a significantly lower dose at follow-up than the treatment non-responder group. These findings suggest that long-acting opioid medications can improve mood and do not impair cognitive functioning in patients with chronic non-cancer pain.

Meta-analytic comparison of the components of visual cognition in Parkinson's disease

Controversy surrounds the presence of deficits of visual cognition in Parkinson's Disease. This literature has been seriously undermined by a number of methodological and theoretical faults that make interpretation of this hypothesis difficult. This review proposes a structure of visual cognition composed of 13 aspects. A meta-analysis of these components on 70 studies that used standardised neuropsychological tests and an appropriate normal control group indicates that the PD subjects are significantly compromised on tests of attention and concentration, complex visuospatial functions, and multifactorial spatial functions. More detailed analysis of the basic components of visual cognition was not undertaken due to low statistical power; hence, it remains unclear whether these subjects have primary visual processing deficits in association with their higher order deficits. The observed deficits may be interpreted as being a consequence of either undetermined lower level visual cognitive deficits or a compromise in executive functioning.

Reversal of visuospatial deficit on the Clock Drawing Test in Parkinson's disease by treatment with weak electromagnetic fields

Visuospatial deficits are among the most frequently encountered abnormalities in neuropsychological testing of patients with Parkinson's disease, being present in up to 90% of cases. Clinically, impairment of visuospatial functions may not be noted by Parkinsonian patients but may contribute to various functional disabilities including frequent falls, difficulties operating a vehicle, ambulating, and dressing. I have reported recently that treatment with external electromagnetic fields (EMFs) in the picotesla (pT) range intensity is an effective nonpharmacological modality in the management of the motor and various cognitive deficits of Parkinsonism including visuoperceptive and visuospatial functions. The present communication concerns four fully medicated Parkinsonian patients who, in response to treatment with EMFs, exhibited reversal of visuospatial impairments as demonstrated on the Clock Drawing Test. Specifically, prior to treatment with EMFs these patients demonstrated a visuospatial deficit which was evident by the placement of the numbers on the clock distant from the periphery. Following a series of treatments with EMFs this visuospatial deficit was corrected. The report supports prior observations demonstrating that externally applied pT range intensity EMFs may bring about reversal of visuospatial deficits in Parkinsonian patients which usually are not improved by treatment with dopaminergic or anticholinergic drugs.

Weak electromagnetic fields reverse visuospatial hemi-inattention in Parkinson's disease

Drawing tasks, both free and copied, have achieved a central position in neuropsychological testing of patients with unilateral cerebral dysfunction by virtue of their sensitivity to different kinds of organic brain disorders and their ability to provide information on lateralized brain damage. In the drawings of patients with right hemispheric damage, visuospatial neglect is revealed by the omission of details on the side of the drawing contralateral to the hemispheric lesion. Patients with unilateral cerebral damage, particularly those with left hemispheric damage, also demonstrate a tendency to place their drawings on the side of the page ipsilateral to the cerebral lesion, a phenomenon which has been termed visuospatial hemi-inattention. It has been reported previously that brief external application of alternating pulsed electromagnetic fields (EMFs) in the picotesla (pT) range intensity improved visuoperceptive and visuospatial functions and reversed neglect in Parkinsonian patients. The present communication concerns four fully medicated elderly nondemented Parkinsonian patients (mean age: 74.7 +/- 4.6 yrs; mean duration of illness: 7.7 +/- 5.2 yrs) in whom application of these EMFs produced reversal of visuospatial hemi-inattention related to left hemispheric dysfunction. These findings support prior observations demonstrating that pT EMFs may bring about reversal of certain cognitive deficits in Parkinsonian patients.

Impaired problem solving in Parkinson's disease: impact of a set-shifting deficit

Parkinson's disease (PD) is associated with specific cognitive deficits in the absence of dementia, including the inability to suppress previously learned responses in a changed context. Our goal was to determine whether this set-shifting deficit is sufficient to account for impaired performance on a problem-solving task, or, instead, whether it is necessary to postulate deficits in one or more other cognitive capacities, such as logical deduction. Deductive reasoning and other conceptual abilities were assessed in 15 nondemented subjects with PD who had never been medicated, 15 nondemented subjects with PD who were currently receiving medication, and 15 healthy elderly control subjects. On a deductive reasoning task, Poisoned Food Problems, the PD groups made more errors than the control group. The PD groups' error pattern was characterized by intrusions of information from previous problems. By contrast, the PD groups made appropriate assessments of redundant and irrelevant information that appeared in these problems, and performed normally on other tests of concept formation and problem solving that did not require set shifting, indicating that the capacities for logical deduction and concept formation were intact. The set-shifting deficit, conceptualized as a difficulty in suppressing a prepotent response, appears to be a primary cognitive impairment in PD and presumably arises from dysfunction of the nigrostriatal-dorsolateral prefrontal cortex complex loop.

Reversal of a visuoconstructional deficit in Parkinson's disease by application of external magnetic fields: a report of five cases

Visuoperceptive and visuomotor deficits are among the most frequently encountered abnormalities in neuropsychological testing of patients with Parkinson's disease, being present in up to 90% of cases. Clinically, the presence of visuoperceptive and visuomotor impairment may not be noted by Parkinsonian patients but may contribute to various functional disabilities including difficulties operating a vehicle, ambulating, and dressing. The present communication concerns five medicated Parkinsonian patients who responded to extracranial treatment with magnetic fields in the picotesia range intensity with improvement in motor, behavioral, and autonomic functions as well as visuoconstructional tasks as demonstrated on the Bicycle Drawing test. Specifically, prior to treatment with magnetic fields these patients failed to draw the spokes in the wheels of a bicycle that extended completely to the periphery of the rim. I considered this observation to reflect a specific visuoconstructional deficit inherent to the Parkinsonian disease process. This visuoconstructional impairment was reversed, however, by external applications of magnetic fields. The report supports prior observations demonstrating that picotesla range intensity magnetic fields may bring about reversal of specific cognitive deficits in Parkinsonian patients.

The effects of picoTesla range magnetic fields on perceptual organization and visual memory in parkinsonism

Drawing tasks, both free and copied, have achieved a central position in the neuropsychological evaluation of constructional abilities in brain injured patients. The Rey-Osterrieth Complex Figure Test was devised in early 1940s as a tool to investigate perceptual organization and visual memory. The Bicycle Drawing Test is used as a measure of mechanical reasoning as well as visuographic functioning. Recent reports have demonstrated that extracranial treatment with magnetic fields (MF) in the picoTesla range improves constructional abilities including visuoperceptive functions in Parkinsonian patients. To evaluate further the effects of these extremely weak MF on cognitive functions in Parkinsonism, I investigated in a 69 year old fully medicated Parkinsonian patient the influence of a single, extracranial application of MF on the patient's performance on the Complex Figure (copy and recall) as well as the Bicycle Drawing Test. Results of the trial showed that a 30 minute application of MF produced a dramatic improvement in the patient's ability to copy and recall the Complex Figure. This treatment was also associated with a marked improvement in the performance of bicycle drawing with reversal of the Parkinsonian micrographia. Collectively, these findings demonstrate that this treatment modality may reverse some of the cognitive impairments associated with Parkinsonism which usually are not improved by treatment with dopaminergic or anticholinergic medications.

Reversal of visual neglect in Parkinson's disease by treatment with picoTesla range magnetic fields

Visual neglect and impairment in perceptual motor or visuospatial tasks are among the most frequently encountered abnormalities in neuropsychological testing of patients with Parkinson's disease, being present in up to 90% of patients. It has been proposed that neglect reflects an attentional-arousal deficit induced by lesions that interrupt a cortical-limbic-reticular loop. Recently, we have reported that application of extracranial magnetic fields (MF) in the picoTesla range was efficacious in reducing the severity of the motor disability of Parkinsonism as well as improving some of the cognitive abnormalities associated with the disease such as visuoperceptive deficits. We now present a 61 year old fully medicated Parkinsonian patient in whom rapid reversal of left visual neglect as well as improvement in visuoconstructional (drawing) performance was noted immediately after a single external application of MF. We propose that this effect was related to enhancement of directed attention through a mechanism involving an interaction between the pineal gland, which is considered a "magnetosensor," and the reticular formation which mediates arousal and attention. This report demonstrates the efficacy of extremely weak MF in reversing some of the cognitive abnormalities in Parkinsonism, notably neglect and visuoperceptive deficits, which contribute significantly to impairment of the patient's daily living activities.

A meta-analysis of the relative sensitivity of neuropsychological screening tests

The National Institute of Mental Health recently formed a committee of experts which published a proposal for a lengthy neuropsychological test battery judged most apt to detect diffuse brain damage while covering a wide range of cognitive abilities. The purposes of the present study were (1) to assemble empirical evidence of the existence of statistically significantly sensitive screening tests across an equivalently wide range of functional domains, and (2) to present this evidence systematically, in such a manner as to help clinicians select subsets of screening tests manifesting greatest sensitivity to diffuse brain damage. It was found that in certain functional domains (speed of processing, problem solving, executive functions), marked differences in sensitivity occurred. Brief tests just as sensitive as time-consuming tests were also identified. The reader is cautioned about possible extraneous sources of the differences obtained (test and group selection bias, test reliability, test difficulty, procedural effects, Type I error). Nevertheless, it was concluded that a brief highly sensitive and functionally wide-ranging neuropsychological test battery for screening cases of putative diffuse brain dysfunction can be assembled.

Rapid improvement of visuoperceptive functions by picoTesla range magnetic fields in patients with Parkinson's disease

Impairment in perceptual motor or visuospatial tasks is among the most frequently encountered abnormality in neuropsychological testing of patients with Parkinson's disease, being present in up to 90% of cases. Visuoperceptive deficits can result from cortical and subcortical lesions involving the right hemisphere, thalamus, and basal ganglia and are thought to reflect a defect in attentional-arousal mechanisms induced by lesions that interrupt a cortical-limbic-reticular activating loop. Clinically, the presence of visuoperceptive impairment may not be noted by Parkinsonian patients but may contribute to various disabilities including difficulty driving a vehicle and difficulties performing daily tasks which require intact visuospatial abilities (i.e., walking, dressing, drawing and copying designs). The present communication concerns two fully medicated Parkinsonian patients who responded to extracranial treatment with picoTesla range magnetic fields (MF), behaviorally and also demonstrated rapidly and dramatically enhanced visuoperceptive functions as demonstrated on various drawing tasks. These findings demonstrate the efficacy of extremely weak MF in enhancing cognitive functions in patients with Parkinson's disease.

Gender- and age-specific changes in motor speed and eye-hand coordination in adults: normative values for the Finger Tapping and Grooved Pegboard Tests

Normative values for the Finger Tapping and Grooved Pegboard Tests were developed on a sample of 360 normal volunteers stratified according to gender, three educational groups ranging from 7 to 22 years, and four age groups subdivided between the ages of 16 to 70 years. Retest reliability was estimated for both measures. The Finger Tapping Test showed significant gender differences, since women were substantially slower, particularly in the older age groups. On the Grooved Pegboard Test, a converse gender difference was noted, since women were substantially faster than men. A smaller effect with increasing age resulted, and better educated individuals performed faster. If these motor and visuomotor tests are to be applied, then stratified normative estimates need to be implemented to provide viable clinical judgements.

Characterizing the neuropsychological functioning of persons with human immunodeficiency virus (HIV) infection, Part II. Neuropsychological functioning of persons at different stages of HIV infection

Neuropsychological impairment has been reported to occur in persons at all stages of infection with the human immunodeficiency virus (HIV). However, the findings of studies to characterize the incidence and pattern of impairment have been limited by inconsistent definitions of impairment and the failure to control for confounding variables, such as hematological abnormalities, history of head injury, or substance abuse. In the present study, neuropsychological tests were administered to 141 persons at four stages of HIV infection. Significant differences were found in the percentage of persons who showed impairment at each stage of infection. Further, participants' performance on the tests tended to decline across progressive stages of infection. These findings may help psychiatric nurses identify and manage the changes associated with HIV infection.

Chronic occupational exposure to manganese and neurobehavioral function

Comprehensive examinations of neurobehavioral function were performed in two groups of workers with chronic exposure to industrial manganese, and two control groups. Group 1 included 17 exposed workers without parkinsonism while Group 2 consisted of four exposed workers with parkinsonian syndrome resulting from chronic manganese poisoning. Group 3 was composed of eight idiopathic parkinsonian patients while Group 4 included 19 control subjects. Age, sex, and educational level of these four groups were matched. The neuropsychological battery consisted of tests of orientation, intelligence, learning and memory, language and communication, visuospatial and visual perception, visual attention, manual dexterity, and information processing speed. There was no evidence of neurobehavioral impairment in the non-parkinsonian workers whereas impaired general intelligence, visuoperceptive impairment and defective manual dexterity, as well as slowdown in response speed were manifested in the parkinsonian workers.

Neuropsychological aspects of Parkinson's disease

The neuropsychological effects of Parkinson's disease have gained wide recognition in recent literature. Effects have been documented in almost all areas of cognitive functioning, including general intellectual functioning, visual-spatial functioning, executive functions, attention and memory functions, language functions, and affective processes. Visual-spatial functions, memory functions, and executive functions have received particular interest. This review of the literature is an attempt to tie together the large number of studies in these cognitive areas and to present a suggestion for a comprehensive neuropsychological battery tailored to the patient with Parkinson's disease. Throughout the review, factors relevant to Parkinson's disease, e.g., dementia, motor symptoms, and hemiparkinsonism, are considered.

Parkinson's disease: a conceptualization of neuropsychological deficits within an information-processing framework

Parkinson's disease patients are frequently impaired in a variety of neuropsychological tasks involving memory, perceptual motor performance and cognitive flexibility. Although various theories have been forwarded to explain specific impairments, few attempts have been made to account for all the deficits within a single theoretical framework. Furthermore, the frequent occurrence of dementia, the adverse side effects of medication and the motor symptoms of the disease tend to interfere with neuropsychological performance. This has hindered the clear delineation of the neuropsychological profile of Parkinsonian patients. The present paper examines the evidence for intellectual deficits in non-demented Parkinson's disease patients. A number of problems inherent in cognitive research on Parkinson's disease are discussed. The contribution of dementia, motor symptom severity and medication in the expression of these intellectual impairments is examined. It is suggested that many of the neuropsychological deficits described in Parkinson's disease may result from a common underlying deficit in some aspect of information processing. Although it is not possible to pinpoint the precise mechanism(s) involved on the basis of the available evidence, several possibilities are suggested by cognitive and electrophysiological data.

Planning and spatial working memory in Parkinson's disease

The higher level cognitive function of planning was studied in a group of medicated Parkinson's disease patients and a group of matched control subjects, using a computerised version of Shallice's Tower of London task. Baseline measurement of the ability to execute a given plan of action, to generate low level strategies required for efficient searching, and spatial working memory capacity, all of which contribute to performance on the planning task, established that the Parkinson's disease group was unimpaired on any of these measures. On the Tower of London task, the Parkinson's disease group was also unimpaired in terms of the average number of moves required to solve a problem. However, a specific planning deficit was evident when "thinking" times were analysed, and this was after the confounding influence of motor initiation and execution times had been carefully extracted from total performance times. This finding is discussed in relation to putative functions of the frontal lobes and basal ganglia, and an attention-switching hypothesis is developed to account for it.

Problem solving ability of parkinsonians

The hypothesis to be verified is that the cognitive defects in nondemented and nondepressed Parkinsonians are due solely to a bilateral nigrostriatal disorder that causes motor slowing. It was tested on 26 mildly disabled patients with idiopathic Parkinson disease optimally controlled with L-Dopa, nondemented and nondepressed and not receiving anticholinergic. The test used was a simplified version of the London Towers Test of problem-solving ability, designed to measure a facet of prefrontally-induced bradyphrenia, already calibrated on 131 healthy subjects. The results revealed no significant difference between the Parkinsonians and controls, thus providing no support for the hypothesis in question.

Dementia and treatment with L-dopa in Parkinson's disease

We compared the neuropsychological performance of patients with Parkinson's disease who were young at onset of the disease (mean age, 41.4 years) and had received prolonged L-dopa treatment (mean, 52.1 months) with nontreated patients of the same age. A similar comparison was made for patients who were older at onset of the disease (mean, 62.1 years). There were no significant differences in cognitive and memory functions between the L-Dopa-treated and untreated young patients, whereas the L-Dopa-treated patients in the older age group performed more poorly than untreated patients in some memory tests (Wechsler Memory Scale I: logical and visual) and cognitive functions (Wechsler Adult Intelligence Scale: similarities, block design, and cognitive flexibility). Treatment duration, disease duration, and mean L-Dopa dose were comparable for the two age groups. After linear effects of age and disease duration had been eliminated, the duration of L-Dopa treatment did not correlate with the cognitive variables studied. These observations suggest that treatment with L-Dopa may not be the cause of cognitive impairment in Parkinson's disease.

Cognition and the basal ganglia: a possible substrate for procedural knowledge

Disruption of neural activity within the basal ganglia of experimental animals causes selective learning deficits in tasks requiring switching between response strategies. These data along with reports of both general and specific intellectual impairment in patients with neurodegenerative disorders such as Parkinson's disease, appear to support the theory of cognitive functions of the basal ganglia. Recent studies have failed to confirm general cognitive or memory deficits in parkinsonian patients, but have identified deficiencies in devising and executing certain cognitive strategies. Following the lead of theorists such as Squire and Mishkin, this brief review emphasizes the distinction between procedural and declarative knowledge and examines the possible role of the basal ganglia in the acquisition and retention of procedural knowledge.

Evoked potential changes and neuropsychological performance in Parkinson's disease

Auditory brainstem responses (ABRs) and long latency exogenous and endogenous auditory evoked potentials (EPs) were investigated in 16 patients with Parkinson's disease and 11 control subjects. Parkinson's disease patients were impaired on mental status testing. While ABRs and the N1 component of the auditory EP were of normal latency in Parkinson patients, the endogenous components, N2 and P3, were prolonged. Prolongation of P3 latency in Parkinson's disease correlated with mental status decline, but not with severity of motoric disturbance. Thirteen PD patients also received neuropsychological evaluation. P3 latency was correlated with tests requiring learning or mental manipulation of information, but not with measures of verbal performance, immediate memory, or depression. P3 latency prolongation appears to have a selective relationship to intellectual changes in PD, and may be most sensitive to deficits requiring significant cognitive effort.

The effects of low doses of caffeine on human performance and mood

Caffeine is thought to have stimulant-like behavioral effects on mood and performance. However few behavioral studies have examined this substance's acute effects when administered in a range of doses that include the low doses typically found in foods and over-the-counter drugs. We therefore gave single doses of caffeine (32, 64, 128 and 256 mg) to 20 healthy male subjects and assessed various aspects of performance and self-reported mood states, as well as plasma caffeine concentration. As little as 32 mg (which elevated plasma caffeine concentration to less than 1 microgram/ml), typical of the dose found in a single serving of a cola beverage, and less than that found in a single cup of coffee or a single dose of over-the-counter drugs, significantly improved auditory vigilance and visual reaction time. All other caffeine doses administered also significantly improved performance on these tests. No adverse behavioral effects, such as increased anxiety or impaired motor performance, were noted even at the highest dose administered.

Is there a specific visuo-spatial impairment in Parkinsonians?

Twenty-five non-demented patients with mild, idiopathic, Parkinson's disease were compared with 25 age and education matched normal controls on a visuo-spatial performance task, whose characteristics were directional forecast, with minimal motor requirement and a maximal spatial load. No statistical support was found for the existence of spatial impairment in these patients.

Dementia in movement disorders

Of all the movement disorders, Huntington's disease has been most consistently associated with dementia, while it is only over the last decade that intellectual cognitive decline have been recognized as common features of Parkinson's disease. It is now known that the pathology in these two conditions reflects differential involvement of the striatum. The Huntington lesion is primarily in the caudate, while the Parkinson lesion preferentially affects the putamen. Both conditions have more diffuse pathology, and dementia may also occur in a wide range of other extrapyramidal diseases, such as progressive supranuclear palsy, the parkinsonism-dementia complex of Guam, and certain spinocerebellar degenerations. Clinicopathological correlations will be reviewed in these disorders of primarily subcortical pathology, and comparisons will be made with Alzheimer's disease, a disorder of predominantly cortical pathology.

Cognitive performance in early Parkinson's disease

The cognitive, memory and psychomotor performance of 67 patients with Parkinson's disease who had not received any antiparkinson medication was compared with the performance of 43 healthy subjects matched by age and education. The principal impairments in the patients were motor ones, evident in various tests such as general motor slowness and delayed initiation of movement, and they correlated with clinical rigidity and hypokinesia but not with tremor. The performance of the patients was inferior to that of the controls in memory tests involving the processing of information and learning (logical memory, associative learning) but not in less demanding tasks such as the retrieval of numbers. The total disability was due to a combined effect of aging and disease. A decrease of about 15% in the psychomotor and cognitive performance, related to aging alone, can be expected to occur between the ages of 50 and 70. The performance of the patients in memory tests and other tests evaluating cognitive capacity did not correlate either with their motor disability or with their mood. A possibility therefore exists that biological processes behind the cognitive decline and the motor disability are separate, even if they may occur simultaneously.

The effect of Parkinson's disease on the ability to maintain a mental set

In two experiments with an Odd-Man-Out choice discrimination task, Parkinsonian subjects had difficulty in alternating between two rules on successive trials. The pattern of errors suggested that the difficulty arises from an instability of cognitive set rather than any loss of reasoning ability, perseveration or increased distractibility.

Recognition memory in Parkinson's disease

On four tests of visual recognition memory Parkinsonian patients obtained normal scores, both immediately and after a delay. They also resembled controls closely in nearly all characteristics of memory. Their performance did not correlate with age, motor disability or disease duration. Parkinson's disease does not, therefore, affect this kind of memory.

Cognitive and motor shifting aptitude disorder in Parkinson's disease

Eighteen patients suffering from Parkinson's disease and nineteen control subjects, who were matched for age and intelligence, were compared in tests measuring "shifting aptitude" at cognitive and motor levels (word production, sorting blocks or animals, and finger pushing sequences). It was found that Parkinson patients produced fewer different names of animals and professions in one minute than control subjects, needed more trials for detecting a shift in a sorting criterion, and produced fewer finger responses in a change of pushing sequence than control subjects. These results are interpreted as reflecting a central programming deficit that manifests itself in verbal, figural and motor modalities, that is, a diminished "shifting aptitude" characteristic of patients with dysfunctioning basal ganglia. The results are discussed in relation to changes of behaviour organisations in animals with dysfunctioning basal ganglia.

Central catecholamine metabolism in vivo and the cognitive and motor deficits in Parkinson's disease

Cerebrospinal fluid levels of homovanillic acid (HVA) in unmedicated patients with Parkinson's disease were 45% of levels in control subjects. Levels of 3-methoxy-4-hydroxyphenylglycol (MHPG) and platelet monoamine oxidase activity (MAO) did not differ. Within the Parkinson's disease group platelet MAO B activity correlated with HVA (an MAO B substrate) but not MHPG (an MAO A substrate). A mild global dementia was found that did not correlate with the more severe motor deficit. There was a negative correlation between the motor deficit and HVA levels but not with MHPG. Cognitive functioning correlated positively with platelet MAO, and the ratio of HVA to MHPG levels and negatively with MHPG alone. It is postulated that dopaminergic and noradrenergic activity or the functional balance between these systems may contribute to the observed cognitive dysfunction.

A controlled study of dementia in Parkinson's disease

Tests of cognitive functions were carried out in a group of patients with Parkinson's disease and repeated after a three-year interval. Comparison was made with a control group drawn from a population of psychiatric patients, matched for age and sex. No differences in cognitive functions were found between the groups, either initially, or between those surviving for three years. Deaths among the index group included a high proportion of patients with cognitive impairment and there was an increasing prevalence and severity of dementia in the index group which exceeded that observed in the control group. Requirements for a methodologically sound study of dementia in Parkinson's disease are discussed.

Mental deterioration, visuoperceptive disabilities and constructional apraxia in Parkinson's disease

20 patients with Parkinson's disease were tested for visuoperceptive disabilities and constructional apraxia versus a group of 20 controls. The visuoperceptive disabilities in the parkinsonians were relatively independent of mental deterioration, where present. The visuoperceptive disabilities were responsible for constructional apraxia.

Cognition in Parkinson disease: an event-related potential perspective

Auditory event-related potentials (ERP) elicited in a target detection stimulus paradigm and pattern-shift visual ERPs were studied in 20 male patients with idiopathic Parkinson disease (PD) and 20 age-matched normal controls. Patients showed significantly increased latencies for both the P200 and P300 components of the auditory ERP. Patients and controls showed no significant differences in latency of the visual ERP but patients showed significantly decreased amplitude. Only one of five neuropsychological measures, the Symbol Digit Modalities test (SDMT), showed a significant negative correlation with P300 latency. The significant association between the two measures that showed impairments in the PD patients (P300 latency and SDMT scores) suggested that these measures reflect a common, disrupted aspect of cognitive function in PD.

Dementia in Parkinson disease: a neuropsychological analysis

An extensive set of neuropsychological measures was administered to 60 Parkinson's disease patients and age-, sex-, and education-matched controls in order to investigate the nature and prevalence of the cognitive deficit in the disease. Parkinsonian patients performed significantly poorer on all measures with the exception of tests for apraxia and object recognition, and on a test of vocabulary knowledge. Discriminant analysis of the test data revealed that over 93% of patients are impaired relative to matched controls, but that assigning a prevalence rate for dementia in the disease may be difficult due to the continuous distribution of cognitive deficits.