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Biomedical subjects

U Halsband

Publications and source records attributed to U Halsband.

13 recordsLinked to original sources
PubMed1997

What is the role of the corpus callosum in intermanual transfer of motor skills? A study of three cases with callosal pathology.

Intermanual transfer for a skilled motor task was studied in two patients with total callosal agenesis, and one with an acquired partial callosal lesion and clinical evidence for disturbed transfer of motor signals. Patients had to draw meaningless figures with one upper extremity (original learning, OL) and to reproduce their mirror-reversals thereafter with the other side (transfer learning, TL). Both directions of intermanual transfer were tested in two conditions, that is, between either proximal or distal muscle groups. Transfer was evaluated by comparing OL and TL performance at the same effector. The main variable of interest was movement time during the first eight trials of OL and TL. All three patients displayed a significant benefit for transfer from the dominant to the non-dominant hand but not vice versa during proximal motor activity. When compared with the performance of healthy subjects tested in almost identical conditions in a previously reported study, the proximal transfer behavior was found to be similar for all patients and the normal group. Although patients exhibited no significant benefit for distal transfer, their non-dominant-to-dominant distal transfer was above the normal range. The similar transfer pattern of the patients and healthy subjects when using proximal musculature suggests that proximal transfer may be subserved by identical extracallosal pathways, most probably by the ipsilaterally descending motor systems. Since non-dominant-to-dominant distal transfer was found to be disadvantageous in healthy subjects, the patients' relative superiority in this condition may reflect missing callosal influences of an inhibitory nature.

Adult↗
PubMed1996

Intermanual transfer of proximal and distal motor engrams in humans.

We studied intermanual motor transfer for right-to-left or left-to-right direction of transfer between either proximal or distal upper extremity muscle groups. The influence of previously acquired motor engrams (original learning, OL) on learning efficiency of the contralateral side (transfer learning, TL) was examined in 26 right-handed healthy subjects. The task consisted of the drawing of meaningless figures. During TL, OL figures had to be reproduced as vertical mirror reversals. Data revealed a benefit for right-to-left but not left-to-right direction of transfer for time to complete a figure as well as a left-to-right transfer benefit for spatial motor precision. Furthermore, a benefit for intermanual transfer of training between proximal but not distal muscle groups was found when movement time to complete a figure was evaluated. Of special interest was the observation of a disadvantage due to prior contralateral learning for performance at right distal effectors. The asymmetrical transfer benefits with respect to side are in line with previous findings and support the proficiency model and the cross-activation model. Results further showed that intermanual transfer of training might differ with respect to muscle group involvement and suggest that, although primarily facilitating, previous opposite hand training may lead to inhibitory influences on subsequent contralateral reproduction.

Adult↗
PubMed1994

Neuronal activity in the primate supplementary, pre-supplementary and premotor cortex during externally and internally instructed sequential movements.

This study recorded the activity of neurons in the (i) supplementary motor area (SMA), (ii) pre-SMA (the motor area immediately rostral to the SMA), (iii) premotor cortex (PMC) and (iv) primary motor cortex (MI), while the monkey performed a conditional sequential motor task that ensures sequencing of multiple movements to the same manipulandum. This paradigm was chosen in order to prevent the participation of spatial cues in prompting the correct motor sequence. Three different movements (turn-push-pull) were performed under two task conditions: (i) internally determined (I): the monkey had to generate a pre-determined sequence from memory and without visual guidance; (ii) externally triggered (E): the correct sequence of movements was performed by following lights illuminated one after the other. Neuronal activity during the following periods were analyzed: instruction (300 ms following the onset of the auditory instruction signal); delay (interval between the end of the instruction period or the termination of the previous movement and the movement trigger); premovement (interval between the trigger signal and the movement onset); movement (interval between the mechanically-sensed movement onset and the completion of the movement) and reward (500 ms period centered at the time of reward delivery). Pre-SMA neurons were generally more active during the delay and premovement as compared to the movement, instruction and reward periods. Activity in the pre-SMA was more related to E during the pre-movement period, but exhibited a preferential relationship to I in the movement period. SMA neurons were more active when the sequential motor task was internally generated.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Motor learning.

Bilateral damage of the medial temporal lobe system prevents the formation of new declarative memories but leaves intact knowledge that was acquired before damage. For motor learning, no structure has been identified that plays a comparable role for the consolidation of motor memories. The deficits of motor learning are focal and show a similar allocation to the various sensorimotor subsystems, as do the corresponding non-mnemonic functions. The involvement of sensorimotor circuitries changes during motor learning so that association areas are preferentially activated in the early stages, and cerebello- and striato-motor-cortical loops are preferentially activated in the late stages of motor learning. Recent neuroanatomical and neurophysiological findings on the effects of brain lesions in human and non-human primates are discussed.

Animals↗
PubMed1993

The role of premotor cortex and the supplementary motor area in the temporal control of movement in man.

In the present study temporal control of movement was systematically analysed in patients with unilateral lesions of the lateral or medial premotor cortex (PMC) or supplementary motor area (SMA) and in age-matched controls. The ability to learn new temporal adjustments was evaluated by examining rhythm reproduction using either the left or right hand or both hands in an alternating manner. A severe impairment in rhythm reproduction was found after lateral or medial PMC lesions; the deficit was most pronounced when our patients were required to use both hands in an alternating manner. The impairment occurred in the absence of difficulties in manual dexterity or impairments in discriminating the rhythm patterns. In a second series of experiments the contribution of the SMA in organizing movements in the time domain was examined. In this series, two patients with left-sided lesions, including the SMA but sparing tissue from the lateral hemispheric surface, and seven age-matched controls were requested to reproduce rhythm constellations in the presence of a sound signal and from memory. Results reveal that patients with left medial lesions involving the SMA had most severe difficulties to produce any rhythms from memory, though they were able to produce the rhythms under auditory pacing. This deficit in programming sequential patterns from memory in the time domain should be interpreted in the context of a decline in the ability to benefit from previous stimulus presentation, which prevents an effective later programming of these sequences when they have to be rehearsed from memory. It was found that patients with left SMA lesions had an increase in reaction time on a sequential digit task when sequences had to be produced under delayed conditions; by contrast, the controls showed a decrease of reaction time after previous stimulus presentation. The present findings extend previous knowledge on sequential motor tasks and argue for a critical role for both the SMA and the premotor cortex in the generation of sequences from memory that fit into a precise timing plan.

Adult↗
PubMed1992

Left hemisphere preponderance in trajectorial learning.

The present study examines the organisational principle of a trajectorial storage mechanism for isochronically controlled overlearned movements. 48 right-handed subjects were trained on new ideograms at five different sizes. After the trajectory had been overtrained with one hand, learning transfer to the contralateral hand was analysed. Results indicate a significant transfer of trajectorial information after training with the right hand towards the left hand which points to a preponderance of the dominant left hemisphere in generalizing storage of learned trajectories to either upper extremity. The trajectorial storage system has clear geometrical restraints.

Female↗
PubMed1990

Hemispheric specialization in visual, tactile and crossmodal assembling tasks.

There is ample evidence that the right or non-language related hemisphere of the brain is superior in processing of spatial information. This issue appears less clear when a task involves elaborate mental operations that require the integration of spatial information at a stage beyond mere perceptual discrimination. Examples are block design tasks, which are frequently used as estimates of general intelligence. Results of these tests have been contradictory as to whether there is a right hemispheric advantage for their execution. This study was aimed to look at a possible hemispheric preponderance in block design tasks comparing visual, tactile and crossmodal spatial performance. A two-dimensional template had to be reproduced by arranging cubes with surfaces different in both colour and texture. In the visual condition the template was given in the visual modality and the cube arrangement was under visual control. In the tactile condition the template was presented tactually and the cube assembly had to be done under entirely tactual control. In the crossmodal condition the template was presented visually and the assembly was restricted to tactual control. Task completion time (TCT) and number of correct responses (NCR) were compared between right hand and left hand responses. Only in the crossmodal condition a constant left hand superiority of performance was found. Non-crossmodal tasks did not show a constant hemispheric preponderance. In the tactile condition allowing for easy differentiation of input to one or the other hemisphere TCTs varied only according to the compatibility of side of afferent input and side of assembling action irrespective of the hemisphere engaged. It is concluded that mental operations requiring spatial assembling not necessarily engage the non-dominant hemisphere to a larger extent than the language dominant hemisphere. For crossmodal information processing, however, the non-dominant hemisphere appears to be superior.

Adult↗
PubMed1990

Premotor cortex and conditional motor learning in man.

The role of premotor cortex (PMC) in conditional motor learning tasks in man was investigated. Patients with PMC lesions had to learn to associate 6 different visual, tactile or auditory stimuli with 6 different arm movements which were previously rehearsed (Task A). A comparative task involved an association between the same set of sensory stimuli and 6 spatial locations (Task B). Patients with PMC lesions were only impaired when they had to recall a movement from memory on the basis of a sensory cue (Task A), but not for an association involving spatial location (Task B). This indicates that the PMC plays a role in sensory conditional motor learning.

Adult↗
PubMed1987

Responses of sacral visceral afferents from the lower urinary tract, colon and anus to mechanical stimulation.

The discharge characteristics of sacral visceral afferents supplying the urinary bladder, urethra, colon and anus to mechanical stimuli were analyzed in the anaesthetized cat. The stimuli used were passive distension (urinary bladder, colon), isovolumetric contraction (urinary bladder), movements of the urethral catheter and mechanical shearing stimuli (mucosal skin of the anal canal). (1) In total 245 afferent units which projected in the pelvic nerve were isolated from the sacral dorsal roots. From one of the following organs, urinary bladder, colon, urethra and anus 117 afferent units were activated. By these stimuli from the bladder, urethra and anus 122 afferent units could not be activated, and as far as tested also not from the colon; in 6 afferent units the classification was unclear. (2) Afferent units from the urinary bladder and the colon responded consistently to passive distension of the respective organ. The units from the urinary bladder showed graded responses at intraluminal pressures of about 10-70 mmHg and responded also to isovolumetric contractions of the organ. The thresholds of the units from the bladder to passive distension and contraction varied from about 5 to 20 mmHg intravesical pressure. (3) The afferent units from the urethra and the anus did not react or showed some weak phasic and irregular responses to distension and contraction applied to the urinary bladder or to distension of the colon. They were consistently excited by low threshold mechanical stimulation of the urethra and anus, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Afferent Pathways↗
PubMed1985

Premotor cortex and the conditions for movement in monkeys (Macaca fascicularis).

Cortical association areas direct their influence on motor cortex via premotor and supplementary motor cortex. In the present experiment premotor cortex was removed bilaterally in monkeys. The monkeys were unable to relearn a visual conditional motor task on which the correct action is specified by visual cues. It was shown that the same monkeys were unable to learn a non motor visual conditional task on which the visual cues specified which object should be chosen. It is concluded that the monkeys are only impaired when they must recall a movement from memory on the basis of a visual cue.

Animals↗
PubMed1985

Unilateral spatial neglect and defective performance in one half of space.

The performance of 80 unselected patients with unilateral cerebral lesions (verified by CT scan) was compared with that of 34 control subjects on 6 "screening" tests for visual, auditory, tactile, kinaesthetic, motor and conceptual neglect. The performance of all 114 patients was tested comparably on the left and right sides, and (except for motor neglect) also centrally. Cut-off scores were determined so that performance inferior to 95% of the control range could be identified. The criterion for neglect was contralateral defect in the absence of ipsilateral and of central defect. With this procedure 30 patients were identified as showing neglect (5 visual, 6 auditory, 5 tactile and 4 motor--all 20 patients showing only one form of neglect; 10 with various combinations of neglect). In 27 of these 30 patients the lesion was found to be right-sided. The performance of various groups of patients with neglect was then compared with that of the 50 patients without neglect on 26 "evaluative" tests, designed to characterize the different varieties of neglect. For this comparison discriminant analysis was used. The outcome of two discriminant analyses instance a patient with visual and auditory neglect is not similar to a patient either with exclusively visual or with exclusively auditory neglect; (2) mixed, tactile and motor neglect are easy to discriminate from other kinds of neglect, whereas visual and auditory neglect are less easy to discriminate, particularly from patients without neglect; (3) the discriminant functions seem to reflect general spatial defect not confined to one side of space; differential spatial performance to the contralateral/ipsilateral sides; and manipulation. The findings are discussed in relation to previous interpretations of neglect; the defect is regarded as one of local attention.

Adolescent↗