Motor performance after unilateral hemisphere damage in patients with tumor

HIV infection across aging: Synergistic effects on intrinsic functional connectivity of the brain

The objective of the study was to examine additive and synergistic effects of age and HIV infection on resting state (RS) intra- and inter-network functional connectivity (FC) of the brain. We also aimed to assess relationships with neurocognition and determine clinical-, treatment-, and health-related factors moderating intrinsic brain activity in aging HIV-positive (HIV+) individuals. The current report presents data on 54 HIV+ individuals (age M = 41, SD = 12 years) stabilized on cART and 54 socio-demographically matched healthy (HIV-) comparators (age M = 43, SD = 12 years), with cohort education mean of 16 years (SD = 12). Age at seroconversion ranged 20-55 years old. ANOVA assessed additive and synergistic effects of age and HIV in 133 ROIs. Bivariate statistics examined relationships of FC indices vulnerable to age-HIV interactions and neurocognitive domains T-scores (attention, executive, memory, psychomotor, semantic skills). Multivariate logistic models determined covariates of FC. This study found no statistically significant age-HIV effects on RS-FC after correcting for multiple comparisons except for synergistic effects on connectivity within cingulo-opercular network (CON) at the trending level. However, for uncorrected RS connectivity analyses, we observed HIV-related strengthening between regions of fronto-parietal network (FPN) and default mode network (DMN), and particular DMN regions and sensorimotor network (SMN). Simultaneously, FC weakening was observed within FPN and between other regions of DMN-SMN, in HIV+ vs. HIV- individuals. Ten ROI pairs revealed age-HIV interactions, with FC decreasing with age in HIV+, while increasing in controls. FC correlated with particular cognitive domains positively in HIV+ vs. negatively in HIV- group. Proportion of life prior-to-after HIV-seroconversion, post-infection years, and treatment determined within-FPN and SMN-DMN FC. In sum, highly functioning HIV+/cART+ patients do not reveal significantly altered RS-FC from healthy comparators. Nonetheless, the current findings uncorrected for multiple comparisons suggest that HIV infection may lead to simultaneous increases and decreases in FC in distinct brain regions even in patients successfully stabilized on cART. Moreover, RS-fMRI ROI-based analysis can be sensitive to age-HIV interactions, which are especially pronounced for inter-network FC in relation to neurocognition. Aging and treatment-related factors partially explain RS-FC in aging HIV+ patients.

Effects of age, HIV, and HIV-associated clinical factors on neuropsychological functioning and brain regional volume in HIV+ patients on effective treatment

It is yet unclear if people infected with human immunodeficiency virus (HIV+) on stable, combined antiretroviral therapies (cARTs) decline with age at the same or greater rate than healthy people. In this study, we examined independent and interactive effects of HIV, age, and HIV-related clinical parameters on neuropsychological functioning and brain regional volume in a sizable group of Polish HIV+ men receiving cART. We also estimated the impact of nadir CD4 cell count, CD4 cell count during participation in the study, duration of HIV infection, or duration of cART along with age. Ninety-one HIV+ and 95 control (HIV-) volunteers ages 23-75 completed a battery of neuropsychological tests, and 54 HIV+ and 62 HIV- of these volunteers participated in a brain imaging assessment. Regional brain volume in the cortical and subcortical regions was measured using voxel-based morphometry. We have found that HIV and older age were independently related to lower attention, working memory, nonverbal fluency, and visuomotor dexterity. Older age but not HIV was associated with less volume in several cortical and subcortical brain regions. In the oldest HIV+ participants, age had a moderating effect on the relationship between the duration of cART and visuomotor performance, such as that older age decreased speed of visuomotor performance along with every year on cART. Such results may reflect the efficacy of cART in preventing HIV-associated brain damage. They also highlight the importance of monitoring neuropsychological functioning and brain structure in HIV+ patients. This is particularly important in older patients with long adherence to cART.

Age and HIV effects on resting state of the brain in relationship to neurocognitive functioning

This study examined the effects of age and HIV infection on the resting state (RS) functional connectivity (FC) of the brain and cognitive functioning. The objective was to evaluate the moderating role of age and HIV on the relationship between RS-FC and cognition. To examine RS-FC we implemented the Independent Component Analysis (ICA) and Regional Homogeneity (ReHo). Neurocognition was evaluated with comprehensive battery of standardized neuropsychological tests. Age and HIV were entered as the independent variables. The independent effects of age, HIV, and interaction effects of age-HIV on RS-fMRI measures (ICA, ReHo) were tested in 108 participants (age M = 42). RS-FC indices that exhibited age-HIV interactions were entered into further analysis. Bivariate correlation analysis was performed between the retained RS-FC indices and T-scores of neurocognitive domains (Attention, Executive, Memory, Psychomotor, Semantic Skills). Multivariate regression modeling determined the impact of age and HIV on these relationships. We found that in the ICA measures, HIV-seropositivity was decreasing RS-FC in the left middle occipital gyrus (p < .001). Age-HIV interaction was observed in the left superior frontal gyrus (LSupFrontG), where FC was decreasing with age in HIV+ (p < .001) and increasing in HIV- (p = .031). ReHo indices did not reveal significant effects. HIV strengthened the relationship between RS-FC in LSupFrontG, Memory and Psychomotor Factor scores. Aging weakened those relationships only in control group. In sum, age-HIV interaction effects are prominent rather in remote than local RS-FC. Seroconversion strengthens relationships between intrinsic brain activity and neurocognition, but no acceleration with years of age was noted in HIV+ individuals.

Interlimb differences in coordination of unsupported reaching movements

Previous research suggests that interlimb differences in coordination associated with handedness might result from specialized control mechanisms that are subserved by different cerebral hemispheres. Based largely on the results of horizontal plane reaching studies, we have proposed that the hemisphere contralateral to the dominant arm is specialized for predictive control of limb dynamics, while the non-dominant hemisphere is specialized for controlling limb impedance. The current study explores interlimb differences in control of 3-D unsupported reaching movements. While the task was presented in the horizontal plane, participant's arms were unsupported and free to move within a range of the vertical axis, which was redundant to the task plane. Results indicated significant dominant arm advantages for both initial direction accuracy and final position accuracy. The dominant arm showed greater excursion along a redundant axis that was perpendicular to the task, and parallel to gravitational forces. In contrast, the non-dominant arm better impeded motion out of the task-plane. Nevertheless, non-dominant arm task errors varied substantially more with shoulder rotation excursion than did dominant arm task errors. These findings suggest that the dominant arm controller was able to take advantage of the redundant degrees of freedom of the task, while non-dominant task errors appeared enslaved to motion along the redundant axis. These findings are consistent with a dominant controller that is specialized for intersegmental coordination, and a non-dominant controller that is specialized for impedance control. However, the findings are inconsistent with previously documented conclusions from planar tasks, in which non-dominant control leads to greater final position accuracy.

Task-dependent interactions between dopamine D2 receptor polymorphisms and L-DOPA in patients with Parkinson's disease

Variants in genes regulating dopamine transmission affect performance on tasks including working memory and executive function as well as temporal processing and sequence learning. In the current study, we determined whether a dopamine D2 receptor DNA sequence polymorphism interacts with L-DOPA during motor tasks in patients with Parkinson's disease (PD). Forty-five PD patients were genotyped for the DRD2 polymorphism (rs 1076560, G>T). Patients performed an explicit motor sequence learning task and the grooved pegboard test in both ON and OFF L-DOPA states. For motor sequence learning, DRD2 genotype mediated L-DOPA effects such that L-DOPA associated improvements were only observed in the minor T allele carriers (associated with lower D2 receptor availability, t10=-2.71, p=0.022), whereas G homozygotes showed no performance change with L-DOPA. For the grooved pegboard test, performance improved with L-DOPA independent of patients' DRD2 genotype. Collectively these results demonstrate that common DRD2 allelic differences found in the human population may explain how dopamine differentially contributes to performance across tasks and individuals.

Predictive value of Spanish neuropsychological testing for laterality in patients with epilepsy

In presurgical treatment planning for patients with epilepsy, neuropsychological testing assists in lateralization of the seizure focus. Previous research with English speakers has shown that patients with left hemisphere (LH) onsets versus right hemisphere (RH) onsets perform worse on naming and other verbal skills tests, but similar findings with Hispanic patients are limited. Thirty-nine Spanish-speaking patients were administered a comprehensive battery of neuropsychological tests in Spanish. LH-onset patients performed significantly worse than RH-onset patients on verbal comprehension (P=0.006), visual matching (P=0.047), the Ponton-Satz Boston Naming Test (P=0.001), and the dominant hand trial of the Grooved Pegboard Test (P=0.012). A stepwise regression model to predict seizure laterality from these tests was significant (F=12.10, P=0.001), but only the Ponton-Satz Boston Naming Test was retained. This comprehensive battery of neuropsychological tests in Spanish proved useful in predicting lateralization in patients with partial epilepsy.

Ipsilesional motor deficits following stroke reflect hemispheric specializations for movement control

Recent reports of functional impairment in the 'unaffected' limb of stroke patients have suggested that these deficits vary with the side of lesion. This not only supports the idea that the ipsilateral hemisphere contributes to arm movements, but also implies that such contributions are lateralized. We have previously suggested that the left and right hemispheres are specialized for controlling different features of movement. In reaching movements, the non-dominant arm appears better adapted for achieving accurate final positions and the dominant arm for specifying initial trajectory features, such as movement direction and peak acceleration. The purpose of this study was to determine whether different features of control could characterize ipsilesional motor deficits following stroke. Healthy control subjects and patients with either left- or right-hemisphere damage performed targeted single-joint elbow movements of different amplitudes in their ipsilateral hemispace. We predicted that left-hemisphere damage would produce deficits in specification of initial trajectory features, while right-hemisphere damage would produce deficits in final position accuracy. Consistent with our predictions, patients with left, but not right, hemisphere damage showed reduced modulation of acceleration amplitude. However, patients with right, but not left, hemisphere damage showed significantly larger errors in final position, which corresponded to reduced modulation of acceleration duration. Neither patient group differed from controls in terms of movement speed. Instead, the mechanisms by which speed was specified, through modulation of acceleration amplitude and modulation of acceleration duration, appeared to be differentially affected by left- and right-hemisphere damage. These findings support the idea that each hemisphere contributes differentially to the control of initial trajectory and final position, and that ipsilesional deficits following stroke reflect this lateralization in control.

Possibilities of newer ALAD polymorphism influencing human susceptibility to effects of inorganic lead on the neurobehavioral functions

OBJECTIVE

A cross-sectional study was conducted to study the association between some new ALAD polymorphism and susceptibility to effects of inorganic lead on the neurobehavioral functions.

METHOD

We recruited 120 healthy male workers with lead exposure in a factory which manufacture lead stabilizer. The ALAD SNPs studied were HpyCH4, HpyIV RFLP in intron 6, Rsa and Msp RFLP in exon 4, Sau3A in intron 12 and Rsa39488 in exon 5. The World Health Organization Neurobehavioral Core Test Battery (WHO-NCTB) and a few other tests were used. General linear model (GLM) was applied to compare outcome scores between subgroups of each ALAD SNP while controlling for possible confounders.

RESULTS

The mean age of the workers was 39.7 years (S.D. 10.7), mean exposure duration of 10.2 years (S.D. 7.9) and mean blood lead of 22.1 microg/dl (S.D. 9.4). Among the 6 SNPs studied, Rsa and Rsa39488 appear to be the main candidate SNPs. Workers with Rsa and Rsa39488 ALAD 2-2 genotypes fare significantly better in the Aiming Pursue Test Correct (AC), Groove Peg Board non-preferred hand (GPNP), Groove Peg Board Mean (GPM), San Ana Preferred Hand (SAP), San Ana Both Hands (SAB) and AC, GPNH, GPM, Digit Symbol (DIS) tests; respectively compared to Rsa and Rsa39488 ALAD 1-1/1-2 genotypes adjusted for age, race, exposure duration and blood lead levels.

CONCLUSION

The presence of the homozygote Rsa and Rsa39488 ALAD 2-2 seems to offer some protection against the effect of lead on motor dexterity function. While it may appear that newer ALAD polymorphism other than the commonly reported Msp SNP might influence human susceptibility to effects of inorganic lead on the neurobehavioral functions further study involving a larger cohort of workers with Rsa and Rsa39488 ALAD2 allele would be needed to confirm this inference.

A new method of administering the Grooved Pegboard Test: Performance as a function of handedness and sex

The purpose of the present study was twofold: first to examine the influences of sex and handedness on manual performance on the Grooved Pegboard Test; and secondly to provide normative data for two versions (Place and Remove tasks) of the Grooved Pegboard Test, as previous work (Bryden & Roy, 1999) had suggested that the Remove task of the Grooved pegboard may provide a purer measure of motor speed of the two hands than the standard administration of the Grooved Pegboard Test. One hundred and fifty-three (47 males and 106 females) participants completed the Grooved Pegboard Test. Individuals performed the standard version of the Grooved Pegboard Test (Place task) and a novel version of the test (Remove task). In the standard version, participants were timed on their speed for placing the pegs, while in the novel version they were timed on their speed for removing the pegs. Results confirmed previously noted hand and sex differences in the Place task of the Grooved Pegboard Test, as well as the lack of effect of handedness on performance (Bornstein, 1995; Ruff & Parker, 1993). Significant performance differences between the hands were also noted for the Remove task. Findings also indicated that the Remove task was sensitive to sex and handedness effects.

Delta-aminolevulinic acid dehydratase (ALAD) polymorphism and susceptibility of workers exposed to inorganic lead and its effects on neurobehavioral functions

We carried out a cross-sectional study on a group of male workers to determine the frequency of delta-aminolevulinic acid dehydratase (ALAD) polymorphisms among Chinese, Malays and Indians workers who were exposed to low to medium levels of inorganic lead. Also, the association between ALAD1 and ALAD2 genotypes and neurobehavioral functions among these workers were investigated. A total of 120 male workers were studied. Blood and urine were collected for each worker to determine the ALAD genotypes, blood lead levels, ALAD, and urinary delta-aminolevulinic acid (ALAU). ALAD1-1 was the predominant genotype for all three ethnic groups while ALAD2-2 was the rarest. The distribution of ALAD1-2 was higher among Malays (16.7%) and Indians (14.3%), compared to Chinese (3.6%). Selected tests from the World Health Organization Neurobehavioral Core Test Battery (WHO-NCTB) were used. Although workers in the ALAD1-1 and ALAD1-2/2-2 groups had comparable blood lead levels, the 106 workers with ALAD1-1 genotypes have significantly higher urinary ALA and significantly poorer neurobehavioral scores involving motor dexterity compared with those who have ALAD1-2/2-2 genotypes (13 workers). It is postulated that the ALAD2 allele may exert protective measures against the neurotoxic effects of lead. Further study involving a larger cohort of workers with the ALAD2 allele would be needed to confirm this hypothesis.

Interlimb differences in control of movement extent

The current study was designed to examine potential interlimb asymmetries in controlling movement extent. Subjects made repetitive single-joint elbow extension movements while the arm was supported on a horizontal, frictionless, air-jet system. Four targets of 10, 20, 35, and 45 degrees excursions were randomly presented over the course of 150 trials. For both arms, peak tangential hand velocity scaled linearly with movement distance. There was no significant difference between either peak velocities or movement accuracies for the two arms. However, the mechanisms responsible for achieving these velocities and extents were quite distinct for each arm. For the dominant arm, peak tangential finger acceleration varied systematically with movement distance. In contrast, nondominant-arm peak tangential acceleration varied little across targets and, as such, was a poor predictor of movement distance. Instead the velocities of the nondominant arm were determined primarily by variation in the duration of the initial acceleration impulse, which corresponds to the time of peak velocity. These different strategies reflect previously identified mechanisms in controlling movement distance: pulse-height control and pulse-width control. The former is characterized by a variation in peak acceleration and has been associated with preplanning mechanisms. The latter occurs after peak acceleration and has been shown to depend on peripheral sensory feedback. Our findings indicate that the dominant-arm system controls movement extent largely through planning mechanisms that specify pulse-height control, whereas the nondominant system does so largely through feedback mediated pulse-width control.

Brain activation during the fist-edge-palm test: a functional MRI study

The purpose of our study is to clarify, using functional MRI, brain regions activated during the fist-edge-palm task (FEP) compared to relatively simple hand motor tasks using either the right or the left hand in right-handed normal volunteers. The FEP was introduced to detect a disorder of voluntary movement, and it is believed to be closely related to contralateral frontal lobe damage. However, this assumption still remains controversial. Ten subjects participated in this study. Hand motor tasks were as follows: (1) the FEP, in which the subjects were requested to place their hand in three different positions sequentially: a fist resting horizontally, a palm resting vertically, and a palm resting horizontally; (2) a fist-palm task (FP), in which the subjects were asked to clench and unclench their fist alternately; and (3) a control task requiring the subjects to knock lightly with their clenched fist. The contralateral sensomotor and premotor areas were activated in the FP with the right hand and the contralateral sensorimotor, premotor, and supplementary motor areas (SMA) were activated in the FP with the left hand. In the FEP with either hand, bilateral premotor and left parietal areas and ipsilateral cerebellum were also activated as well as contralateral sensorimotor area and SMA. Our results suggest that successful performance of the FEP requires the participation of more brain areas than FP, which may explain why some patients without frontal lobe damage failed to perform the FEP.

The role of the left hemisphere in motor control of touch: a functional magnetic resonance imaging analysis

Previous research using a simple finger-touching task has shown greater blood oxygenation level dependent (BOLD) activation volume in the motor cortex of the right hemisphere for contralateral finger touching compared to ipsilateral finger touching, but no significant contralateral advantage for the left hemisphere. Such equal involvement of the left hemisphere for both contralateral and ipsilateral finger touching suggests a special role of the left hemisphere for finger touching. In contrast, we found a contralateral advantage in the motor cortex of both hemispheres in a majority of participants (14/16) when consistently activated BOLD volumes were examined. However, participants who did not show a clear contralateral advantage for the left hemisphere did show activation in the left inferior frontal gyrus (IFG; Broca's Area) and in the left insular cortex, which suggests that verbally mediated sequencing of finger movements can account for our less frequent result.

Motor impairment in patients with parietal lesions: disturbances of meaningless arm movement sequences

The execution of meaningless movement sequences was studied in 12 patients with lesions of the parietal cortex in comparison to the performance of age- and sex-matched controls. Five sequences of increasing complexity had to be performed by imitation and after verbal instruction. The performance errors were qualitatively scored by means of four error categories (temporal or spatial error, addition or omission of movement components). This study examined whether the error scores depended on instruction modality, movement complexity or lesion side. Patients with left parietal lesions produced more errors than those with right parietal lesions and control subjects. While additions or omissions of movement components occurred almost equally in all groups, temporal and spatial errors were more frequent in patients with left parietal lesions only. In addition, only the latter group showed a significant increase of error rates with increasing movement complexity. There were no significant differences between the contra- and ipsilesional hand in any group. These results demonstrate that lesions in the left parietal lobe lead to a disturbed spatio-temporal organisation of movement that becomes increasingly prominent for more complex movements.

Associations of blood lead, dimercaptosuccinic acid-chelatable lead, and tibia lead with neurobehavioral test scores in South Korean lead workers

The authors performed a cross-sectional study to evaluate associations between blood lead, tibia lead, and dimercaptosuccinic acid (DMSA)-chelatable lead and measures of neurobehavioral and peripheral nervous system function among 803 lead-exposed workers and 135 unexposed controls in South Korea. The workers and controls were enrolled in the study between October 1997 and August 1999. Central nervous system function was assessed with a modified version of the World Health Organization Neurobehavioral Core Test Battery. Peripheral nervous system function was assessed by measuring pinch and grip strength and peripheral vibration thresholds. After adjustment for covariates, the signs of the beta coefficients for blood lead were negative for 16 of the 19 tests and blood lead was a significant predictor of worse performance on eight tests. On average, for the eight tests that were significantly associated with blood lead levels, an increase in blood lead of 5 microg/dl was equivalent to an increase of 1.05 years in age. In contrast, after adjustment for covariates, tibia lead level was not associated with neurobehavioral test scores. Associations with DMSA-chelatable lead were similar to those for blood lead. In these currently exposed workers, blood lead was a better predictor of neurobehavioral performance than was tibia or DMSA-chelatable lead, mainly in the domains of executive abilities, manual dexterity, and peripheral motor strength.

Neurotoxicity in young adults 20 years after childhood exposure to lead: the Bunker Hill experience

OBJECTIVES

An epidemiological study of young adults was conducted to determine whether environmental exposure to lead during childhood was associated with current adverse neurobehavioural effects.

METHODS

The exposed group consisted of 281 young adults who had been exposed environmentally to lead as children and the unexposed referent group consisted of 287 age and sex frequency matched subjects. Information on demographics, past and current health, and past exposures to neurotoxicants, and responses to the Swedish Q16 questionnaire were collected by interview. Standard neurobehavioural and neurophysiological tests were administered by computer or trained technicians. K x ray fluorescence was used to estimate tibial bone lead concentrations among the exposed and unexposed groups. Associations were examined between the exposed group and referents and tibial bone lead concentration and the neurobehavioural and neurophysiological outcomes of interest.

RESULTS

Among the measures of peripheral nerve function, after controlling for confounders, sural sensory nerve evoked response amplitude, peroneal motor nerve compound motor action potential amplitude, vibrotactile thresholds of fingers and toes, and standing steadiness were significantly associated with exposure group. Among the neurobehavioural tests, hand-eye coordination, simple reaction time latency, trails B latency, symbol digit latency, serial digit, and learning error score were also significantly associated with exposure group after controlling for confounders. Exposed subjects had significantly more neuropsychiatric symptoms than the referents. Associations between tibial bone lead concentration and scores for vocabulary, vibrotactile thresholds of the fingers, and vibrotactile thresholds of the toes approached significance.

CONCLUSIONS

Significant adverse central and peripheral neurological effects were found in a group of young adults 20 years after childhood environmental exposure to lead when compared with non-exposed controls. The absence of a significant association between neurological outcomes and tibial bone lead concentration, and the presence of significant associations between neurological outcomes and exposure group may be due to either the magnitude of measurement uncertainty in K x ray films relative to the actual tibial bone lead concentration in these young non-occupationally exposed subjects, or uncontrolled confounding of the exposure group.

Comparison of ipsilateral activation between right and left handers: a functional MR imaging study

We used fMRI to compare the ipsilateral activation in the sensorimotor region (SMR) during dominant and non-dominant hand motor tasks between right and left handers. In right handers, the ipsilateral activation was significantly greater during non-dominant (left) hand task than dominant (right) hand task, while in left handers, it showed no significant difference. The ipsilateral activation was most pronounced in the precentral subregion (presumably corresponding to the premotor area) during either hand task in both groups. We conclude that the different patterns of ipsilateral activation might be mainly explained by the hemispheric dominance. The skill of the hand and complexity of tasks may be related to the predominant activation of the premotor area.

Motor dysfunction profiles in traumatic brain injury and postconcussion syndrome

Motor measures are sensitive to central lesions, but they are also affected by peripheral injury and motivation. The motor skills profiles of proven brain injury clients were compared with the profiles of healthy postconcussion patients. The chief result was a double dissociation: The traumatic brain injury (TBI) group produced a motor dysfunction gradient consistent with upper motor neuron disease, while the compensation-seeking postconcussion group produced a nonphysiologic pattern. Objective measures of behavioral pain and emotional distress did not correlate with the findings. Motor skill deficiencies in postconcussion syndrome (PCS) are probably functional in nature.

Tactile sensory impairments and prehensile function in subjects with left-hemisphere cerebral lesions

The relation between tactile sensory impairments and functional activity of the hand was studied in a group of 10 subjects with cerebrovascular accidents (CVAs) that involved the left hemisphere. Pressure sensitivity and static and moving two-point discrimination thresholds were measured on the thumbs and index fingers of both hands of these subjects and on a group of 14 control subjects. Functional use of the hand was assessed using object and material recognition tests and the Jebsen test of hand function. Prehensile capacity was evaluated with a pinch-force test that examined the influence of load force and surface texture on the forces used to grasp an object. For this group of subjects with left-hemisphere CVAs, elevated sensory thresholds were associated with slower performance on the recognition tests, but not with the Jebsen test. The ability to control the forces used to grasp an object was also found to be deficient in these subjects, although the forces were still adapted to the loads being supported and the surface properties of the object being held.

Slowly progressive limb-kinetic apraxia with a decrease in unilateral cerebral blood flow

We report two patients with slowly progressive motor disorders, whose principal manifestations were asymmetric limb-kinetic apraxia and muscle rigidity. In both patients MRI revealed no responsible lesion, whereas single photon emission computed tomography (SPECT) showed a decrease in cerebral blood flow (CBF) in the unilateral hemisphere. One patient with mainly right-sided apraxia had a decreased CBF in the left central region between the frontal and parietal cortices, and the other patient with left-sided apraxia in the right parietal cortex. In agreement with asymmetric clinical symptoms, the regional CBF decrease in the unilateral cortical areas including the frontal and parietal cortices may suggest a degenerative disease, presumably diagnosed as having cortico-basal degeneration.

Force matching by patients with unilateral focal cerebral lesions

The performance of patients with unilateral frontal-, temporal- or fronto-temporal excisions was examined on an isometric force-matching task involving the coordination of forces generated by flexing the fingers. Patients with excisions from the right fronto-temporal cortex were significantly slower with both hands when performing this task using either two or three fingers, whereas the other patient groups tested were not impaired. This deficit in force coordination may result from an impairment in monitoring proprioceptive feedback or an inefficiency in programming the appropriate amount of force output.

The dual task paradigm: speech dominance or manual dominance?

Two hundred and sixty monolinguals divided into subgroups based on gender, handedness, and familial left-handedness, were given a concurrent task, verbal-manual interference paradigm. The primary purpose of the study was to test whether the dual task interference effects were more related to hemispheric speech or manual dominance factors. The dominant hand, regardless of handedness, underwent relatively more tapping interference than the nondominant hand. The obtained results seriously question the basic assumptions underlying the interpretation of the dual task paradigm as an assessment index for hemispheric language lateralization. A possible explanation of this result that is in keeping with known hemispheric language representation proportions in left-handers is offered based on left hemisphere ipsilateral control of the left hand.

Effects of left-hand preference on postinjury measures of distal motor ability

The relationship of preinjury left-hand dominance for motor performance to postinjury distal motor skills following penetrating brain wounds in patients without overt hemiplegia was examined. We studied 13 controls, 13 right-hemisphere brain-damaged patients, and 11 left-hemisphere brain-damaged patients on motor tasks measuring reaction time, strength, and coordination. Our results indicated that no persistent deficits were seen on distal motor tasks in left-handed adults who suffered a penetrating brain wound. These findings are compatible with the relative sparing of persistent neuropsychological deficits in left-handers following brain damage.

Multiple, single-dose naltrexone administrations fail to effect overall cognitive functioning and plasma cortisol in individuals with probable Alzheimer's disease

A double-blind placebo-controlled study was conducted in 10 individuals with probable Alzheimer's disease to assess the effects of varying doses of Naltrexone (0, 25, 50 and 100 mg) on cognitive functioning and on plasma cortisol. Each individual participated in four separate sessions at least three days apart. Naltrexone was found to improve performance in only one of the six psychometric tasks employed (Token Test). However, enhancement of Token Test performance was limited to the 25 mg Naltrexone dose and was mainly the result of an improvement on the part of the two most severely impaired patients. In contrast to the previous reports of elevations of plasma cortisol following administration of opiate antagonists to younger, non-demented subjects, Naltrexone administration failed to produce any significant increase in plasma cortisol in Alzheimer's patients.

Processing of symbolic and nonsymbolic events: a review of comparisons in selected cognitive activities

The cognitive processing of symbolic and nonsymbolic events was compared. Evidence was drawn from the clinical and experimental literature on normal processing, on hemispheric asymmetry and on brain damage sequelae. It was concluded that several basic cognitive activities were manifest both symbolically and nonsymbolically. The cognitive activities included analysis of rapidly changing stimuli, categorical perception, categorical production, hierarchical organization and the production of complex movements. Damage to subcortical as well as cortical structures may contribute to the covariation of symbolic and nonsymbolic deficits. Suggestions were made for future research and the implications for the understanding of aphasia were described.