Biomedical subjects

K Y Haaland

Publications and source records attributed to K Y Haaland.

At least 19 recordsLinked to original sources

PubMed1997

Distributed neural systems underlying the timing of movements.

Timing is essential to the execution of skilled movements, yet our knowledge of the neural systems underlying timekeeping operations is limited. Using whole-brain functional magnetic resonance imaging, subjects were imaged while tapping with their right index finger in synchrony with tones that were separated by constant intervals [Synchronization (S)], followed by tapping without the benefit of an auditory cue [Continuation (C)]. Two control conditions followed in which subjects listened to tones and then made pitch discriminations (D). Both the S and the C conditions produced equivalent activation within the left sensorimotor cortex, the right cerebellum (dorsal dentate nucleus), and the right superior temporal gyrus (STG). Only the C condition produced activation of a medial premotor system, including the caudal supplementary motor area (SMA), the left putamen, and the left ventrolateral thalamus. The C condition also activated a region within the right inferior frontal gyrus (IFG), which is functionally interconnected with auditory cortex. Both control conditions produced bilateral activation of the STG, and the D condition also activated the rostral SMA. These results suggest that the internal generation of precisely timed movements is dependent on three interrelated neural systems, one that is involved in explicit timing (putamen, ventrolateral thalamus, SMA), one that mediates auditory sensory memory (IFG, STG), and another that is involved in sensorimotor processing (dorsal dentate nucleus, sensorimotor cortex).

Adolescent↗

PubMed1997

Cognitive-motor learning in Parkinson's disease.

Procedural learning deficits are common in Parkinson's disease (PD), but contradictory results have been reported in rotary pursuit learning. This article compared rotary pursuit learning in 2 nondemented PD groups and 2 normal control (NC) groups, using a between-subjects group design in which 3 rotation speeds were presented either randomly or in blocks. The pattern of learning differed between the randomized and the blocked conditions in the NC, but not in the PD groups. Learning was impaired in the PD group in the random condition only. Memory, visuospatial, or executive skills were not associated with the PD group's poorer learning in the randomized context. Results show that procedural learning deficits are not universal with basal ganglia abnormalities but rather depend on the specific cognitive requirements of the learning context.

Aged↗

PubMed1997

Nutritional status and cognitive functioning in a normally aging sample: a 6-y reassessment.

Associations between nutritional status and cognitive performance were examined in 137 elderly (aged 66-90 y) community residents. Participants were well-educated, adequately nourished, and free of significant cognitive impairment. Performance on cognitive tests in 1986 was related to both past (1980) and concurrent (1986) nutritional status. Several significant associations (P < 0.05) were observed between cognition and concurrent vitamin status, including better abstraction performance with higher biochemical status and dietary intake of thiamine, riboflavin, niacin, and folate (rs = 0.19-0.29) and better visuospatial performance with higher plasma ascorbate (r = 0.22). Concurrent dietary protein in 1986 correlated significantly (rs = 0.25-0.26) with memory scores, and serum albumin or transferrin with memory, visuospatial, or abstraction scores (rs = 0.18-0.22). Higher past intake of vitamins E, A, B-6, and B-12 was related to better performance on visuospatial recall and/or abstraction tests (rs = 0.19-0.28). Use of self-selected vitamin supplements was associated with better performance on a difficult visuospatial test and an abstraction test. Although associations were relatively weak in this well-nourished and cognitively intact sample, the pattern of outcomes suggests some direction for further research on cognition-nutrition associations in aging.

Aged↗

PubMed1997

Profiles of cognitive functioning in chronic spinal cord injury and the role of moderating variables.

A traumatic spinal cord injury (SCI) is accompanied by a documented moderate to severe head injury in significant numbers of SCI patients. In a previous study (Dowler et al., 1995), cognitive deficits were found in 41% of the SCI individuals who were studied with a chronic injury from a traumatic event. The present study investigated whether clinically useful subtypes of normal and impaired cognition could be identified in a chronic (M = 17 years postinjury) SCI sample using a cluster analysis of neuropsychological test performance. A battery of 16 neuropsychological tests was administered to 91 SCI patients and 75 control participants. Composite scores, reflecting performance in different cognitive domains, were derived from a factor analysis of the battery, and these scores were then used in the cluster analysis. A six-cluster solution generated the most distinct and clinically relevant SCI group profiles. Two of the cognitive profiles were characterized by normal functioning in all cognitive domains, but they were distinguished by differences in performance levels. The remaining four SCI groups (60% of the sample) showed clinically significant deficits in one or more cognitive domains, with different groups showing moderate attention and processing speed deficits, mild deficits in processing speed, executive processing difficulties, or moderate memory impairments. Though age and premorbid intellectual ability were strong predictors of the cognitive profiles of some SCI groups, when these factors were controlled, the findings suggested that the patterns of cognitive impairment were likely due to a potential concomitant head injury.

Adult↗

PubMed1996

Hemispheric asymmetry of movement.

Studies in brain-damaged patients indicate that the left hemisphere in right-handers is specialized for controlling cognitive-motor tasks in both arms. Recent functional imaging data support this conclusion, with the finding that ipsilateral, as well as contralateral, movements activate the left, but not the right, motor cortex or association areas of either hemisphere. Future studies must aspire to identify the mechanisms for this asymmetry.

Animals↗

PubMed1994

Methylmercury poisoning: long-term clinical, radiological, toxicological, and pathological studies of an affected family.

For 3 months in 1969 a family in the United States that included a pregnant mother consumed pork containing methylmercury. Children, aged 20, 13, and 8 years and a neonate, developed severe neurological signs. Twenty-two years later, the 2 oldest had cortical blindness or constricted visual fields, diminished hand proprioception, choreoathetosis, and attentional deficits. Magnetic resonance images showed tissue loss in the calcarine and parietal cortices and cerebellar folia. The youngest had quadriplegia, blindness, and severe mental retardation until their deaths. The brain of the 8-year-old who died at age 30 showed cortical atrophy, neuronal loss, and gliosis, most pronounced in the paracentral and parietooccipital regions. The total mercury level in formalin-fixed, left occipital cortex was 1,974 ng/gm as measured by atomic absorption. Regional brain mercury levels correlated with extent of brain damage. A control patient had 38.5 ng of mercury/gm in the occipital cortex. Systemic organs in the patient and a control subject had comparable mercury levels. In mercury-intoxicated rats, we found that only 5 to 10% of total brain mercury was lost by formalin fixation. Brain inorganic mercury in the patient ranged from 82 to 100%. Since inorganic mercury crosses the blood-brain barrier poorly, biotransformation of methyl to inorganic mercury may have occurred after methylmercury crossed the blood-brain barrier, accounting for its persistence in brain and causing part of the brain damage.

Adolescent↗

PubMed1994

Limb-sequencing deficits after left but not right hemisphere damage.

The performance of right and left hemisphere stroke patients was compared to normal control groups on a task where subjects alternately hit two targets which varied in size from 0.5 to 6.5 cm. The stroke patients used the arm ipsilateral to damage, and the control groups used the same arm as their respective stroke group. Lesion size and location were similar for the two stroke groups. No deficits were found for the right hemisphere stroke group. The left stroke group's tapping speed was not slower at the smallest target, but became progressively slower relative to the control group's as target size increased. Variability in tapping speed increased as target size increased for all except the left stroke group. While the entire left stroke group was as accurate as their controls, the apraxic, but not nonapraxic, patients made more errors on smaller targets only. Two explanations for these findings both emphasize the left hemisphere's special role in motor programming; one focuses upon its dominance for movements which are independent of sensory feedback and the other emphasizes its specialization for processing rapid temporal information.

Aged↗

PubMed1994

Recovery of simple motor skills after head injury.

The performance of 40 head-injured patients (HI) without peripheral upper body injuries and 88 normal controls were compared on finger tapping and grip strength 1 month and 1 year after injury. The HI group demonstrated deficits on both tasks 1 month after injury, but only finger tapping was impaired 1 year postinjury. While grip strength differentially improved in the HI group from 1 month to 1 year, finger tapping improved similarly in both groups. The pattern of results was similar when a subset of 25 HI patients without any evidence of focal lesions were examined. These results demonstrate (1) motor deficits are present 1 year after injury even in a sample of predominantly mild head-injury patients, (2) grip strength is more sensitive to recovery in the first year after head injury, and (3) finger tapping continues to be impaired 1 year after head injury possibly due to its speed requirements.

Adolescent↗

PubMed1993

Effects of aging on planning and implementing arm movements.

In Experiments 1 and 2, aiming movements were performed with and without visual feedback in young and elderly adults. The initial (acceleration and deceleration phases) and secondary movement components were analyzed. Although deceleration phase accuracy decreased without visual feedback in both age groups, accuracy diminished as movement amplitude increased only in the elderly. This suggested that the elderly were more dependent on visual feedback to modify motor programs for longer duration movements. Velocity also increased less with increasing amplitude and target size in the elderly, which was related to impaired preprogramming (acceleration phase) and implementation (deceleration phase) of higher forces. This conclusion was confirmed directly in Experiment 2 because only the deceleration phase was affected by the removal of visual feedback of arm position when availability of visual information could not be predicted before movement.

Adult↗

PubMed1992

Introduction to the special section on the emotional concomitants of brain damage.

The purpose of this introduction is to emphasize the theoretical and clinical implications of studying emotion after brain damage. Theoretically, it is one way of elucidating critical neural substrates of emotion and the interaction of cognitive and noncognitive determinants. Clinically, the cognitive and other behavioral changes associated with certain types of brain damage may make traditional methods of assessing emotion inaccurate. This special section is designed to review current knowledge regarding these issues and to emphasize their theoretical and clinical importance.

Adult↗

PubMed1992

Skill learning in the elderly: diminished implicit and explicit memory for a motor sequence.

Explicit and implicit memory for a cognitive-motor sequence was studied in elderly and young adults. Implicit memory was examined in a serial reaction-time paradigm in which sequences of hand postures repeated cyclically, then shifted to random sequences. Two control groups received random sequences throughout. Movement times (MTs) across the first 4 blocks did not improve more in the elderly-repeated than in the elderly-random group. In contrast, the young-repeated group showed greater improvement in MT across these blocks than the young-random group. MT was less affected in the elderly than in the young by shifts between repeated and random sequences, indicating impaired implicit memory. Explicit memory, which was assessed by free recall and cued recall, also was impaired in the elderly. Diminished implicit memory in the elderly could not be explained solely by the possible intrusion of conscious recollection strategies.

Adult↗

PubMed1992

Motor sequencing with left hemisphere damage. Are some cognitive deficits specific to limb apraxia?

Sixteen left-hemisphere stroke patients, who were apraxic or nonapraxic, and 17 control subjects performed sequences of hand postures that varied in the number of different postures (repetitive and heterogeneous) and sequence length (one to five). Performance of the left hand (ipsilateral to stroke) was compared with a control group using the left hand. All stroke patients had slower reaction times and were slower to execute single hand postures, but the apraxic group was not slower than the nonapraxic group. Both the apraxic and the nonapraxic groups had similar problems scheduling or timing motor programs for both sequence types such that inter-response times were more affected by sequence length than the control group. However, only the apraxic group showed abnormalities in preprogramming heterogeneous sequences. The apraxic group also made more errors and had longer movement times (MTs) than for the other groups, but only for heterogeneous sequences containing more than three hand postures. The nonapraxic group did not show slower MTs or greater errors, regardless of the type or the length of sequences. These results suggested deficits in encoding, generating single movements and in scheduling or timing a series of actions which generally attributable to left hemisphere damage. However, abnormalities in temporal organization processes prior to and during movement were specific to apraxia. The dissociation between the two stroke groups on some but not all aspects of sequencing has implications for different cognitive mechanisms supporting motor sequencing.

Aged↗

PubMed1991

Hemispheric specialization for motor sequencing: abnormalities in levels of programming.

Left and right hemisphere stroke patients and control subjects performed sequences of hand postures which varied in complexity (repetitive and heterogeneous) and length (one to five). Performance in the hand ipsilateral to the stroke was compared to a control group using the same hand. Neither stroke group had problems preprogramming sequences prior to movement. The only deficit seen for the right hemisphere group was a greater difference in movement time (MT) between heterogeneous and repetitive sequences relative to controls, regardless of sequence length. This suggested right hemisphere damage results in subtle timing but not error deficits on more complex movements, perhaps due to increased external spatial demands. The left hemisphere group was slower to execute single postures, and had difficulty scheduling motor programs for repetitive and heterogeneous movements such that inter-response times (IRTs) were more affected by sequence length than for controls. Left hemisphere patients also made more errors on heterogeneous sequences as they increased in length, and the difference in MTs between repetitive and heterogeneous sequences increased more with increasing length relative to their control group. These results suggested the left hemisphere plays a role in controlling single postures, in scheduling motor programs during repetitive and heterogeneous movements, and in processes related to sequential ordering.

Aged↗

PubMed1991

Hearing and cognition in the elderly. New findings and a review of the literature.

The purpose of this study was to determine the relationship between hearing status and cognitive status initially and at 5-year follow-up in a cohort of healthy elderly men and women and to relate the results to published reports on this topic. Volunteers older than 60 years with no major illnesses and taking no long-term prescription medications were examined. Baseline testing of hearing and cognition was performed in 224 subjects; 112 subjects underwent cognitive testing at 5-year follow-up. Hearing was measured by the Speech Perception in Noise test; cognition was measured by two parts of the Wechsler Memory Scale and by the Jacobs Cognitive Screening Test, an oral screening instrument. At baseline there were small correlations between hearing acuity and memory scores, but these disappeared after adjustment for age and gender. Analysis of follow-up memory and cognitive screening test scores in relation to baseline hearing ability showed no correlation between hearing at entry and cognitive function at 5 years. In addition, baseline hearing level did not predict change in memory or cognitive screening test scores during the follow-up period. The power of the study was 90% to detect a correlation of .30 between measures of hearing and cognition. There was no evidence for a major effect of hearing acuity on cognitive function over time in this group of healthy elderly. Review of published studies suggests that hearing ability is related to cognitive status in demented subjects, but there is little to suggest that in the normal elderly, hearing impairment leads to cognitive decline.

Aged↗

PubMed1991

Sequencing in Parkinson's disease. Abnormalities in programming and controlling movement.

Central programming deficits in Parkinson's disease (PD) were studied in two reaction time (RT) experiments. In Experiment 1, PD patients and controls performed sequences of hand postures that varied in length, the number of different postures (repetitive vs heterogeneous), and the delay interval before movement. Before movement, the PD group planned repetitive movements like controls whereas for heterogeneous sequences RT increased less with sequence length for the PD group, implying less preprogramming. The interresponse time (IRT) data from repetitive sequences showed that the PD group had difficulty controlling movement such that IRTs were faster when sequences were longer, thus allowing more time to schedule the termination of the sequence during the course of movement. For heterogeneous sequences, the PD group made more errors and were slower than controls when changing hand postures, suggesting a deficit in switching between different responses. While RT decreased with a longer delay similarly for both groups, IRT1 continued to improve only for the PD group but similarly for both types of sequences, suggesting a deficit specific to programming the first response. In Experiment 2, subjects made decisions about the number of different hand postures contained within a sequence. PD patients' decision times improved more with a longer delay only for heterogeneous sequences, suggesting a problem in identifying the number of different hand postures. The results have implications for levels of motor dysfunction in PD which emphasize the influence of sequence length and complexity.

Aged↗

PubMed1990

Procedural memory in Parkinson's disease: impaired motor but not visuoperceptual learning.

A current model proposes that memory consists of two functionally separate systems that have different neurological substrates. Declarative memory appears to be dependent on the diencephalic medial temporal lobe system whereas some speculate that the basal ganglia may be a neurological substrate for procedural memory. This study tested the role of the basal ganglia in regulating different types of procedural skills by comparing performance on a motor and a visuoperceptual skill learning task. Twenty Parkinson's (PD) patients and 20 normal control subjects performed two procedural learning tasks (rotary pursuit and mirror reading) and one declarative learning task (paired associates) over 3 days. The results showed that PD patients were not impaired on mirror reading or paired associate learning. On rotary pursuit, performance levels on day 1 were similar between groups, but the PD group showed less improvement across days than controls. However, only patients with more advanced symptoms of PD showed impaired rotary pursuit learning, and this could not be attributed directly to deficits in primary motor or general cognitive function. These findings suggest that the underlying processes/procedures for procedural learning are specific to the task, and are supported by different neuroanatomical systems.

Attention↗

PubMed1989

Hemispheric control of the initial and corrective components of aiming movements.

This study examined whether the left and right hemispheres play differential roles in controlling the initial and corrective components of aiming movements. A simple aiming task was administered to 31 normal control subjects and 29 unilateral stroke patients (14 with right hemisphere damage and 15 with left hemisphere damage). Movement amplitude was varied (25, 64 and 100 mm) and reaction time, movement time and accuracy were measured. Through a trajectory analysis, initial and corrective movements were separated. The stroke patients performed the task with their ipsilateral arm which was compared to the normal controls' right or left are performance. Regardless of the movement amplitude the left hemisphere group's reaction time was slower, and the execution of the initial movement component was less accurate than controls. No performance deficits were found on corrective movements. Performance was not impaired for the right hemisphere group on any measures. These results are discussed in terms of the hemispheres' possible roles in controlling movements which are largely open or closed loop.

Aged↗

PubMed1989

The role of the hemispheres in closed loop movements.

The purpose of these experiments was to determine if the two hemispheres play different roles in controlling closed loop movements. Subjects were asked to move to a narrow or wide target in the left or right hemispace. Reaction time (RT) was faster for the left arm of normals, only in the right hemispace, but there were no differences between arms in movement execution. Right but not left hemisphere stroke (CVA) patients showed longer RTs for the contralateral but not ipsilateral arm. The right CVA group's ipsilateral movement, especially to narrow targets was less accurate. The left CVA group's RT did not benefit from advanced information, but ipsilateral movement execution was normal. These results were discussed in terms of inter- as well as intrahemispheric control of programming and execution of closed loop movements.

Brain Damage, Chronic↗