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PubMed1996

Thermography of hands after a radial forearm flap has been raised.

To evaluate possible circulatory changes in the donor hand 18 patients underwent cold stress testing and thermography of both hands a mean of 13 months after a radial forearm flap had been harvested. Temperatures were measured with a computed Inframetrics 600L infrared thermocamera, and the images were videotaped at room temperature and after a cold challenge (immersion in a water bath at 15 degrees C for five minutes). Temperatures were measured on the volar aspect of each fingertip, and rewarming curves were plotted for both hands. The patients could be divided into three groups according to the rewarming pattern: mean temperature of the donor hand was more than 0.5 degree C warmer than that of the other hand (n = 7), rewarming was similar in both hands (n = 6), and the mean temperature of the donor hand was less than 0.5 degree C colder than that of the other hand (n = 5). Patients with a colder donor hand had significantly wider (Pearson's r = 0.62, p = 0.005) and longer (r = 0.71, p = 0.001) defects. The rewarming pattern did not correlate with subjective cold intolerance, but the temperature of the donor hand was a mean of 0.5 degree C less than that of the other hand in room temperature in subjects who experienced cold intolerance (p = 0.019). We conclude that the raising of a radial forearm flap, particularly a large one, affects the thermoregulatory system of the donor hand, results in abnormal rewarming, and can cause subjective cold intolerance.

Adult↗
PubMed2004

Hand hygiene: a frequently missed lifesaving opportunity during patient care.

Health care-associated infections constitute one of the greatest challenges of modern medicine. Despite compelling evidence that proper hand washing can reduce the transmission of pathogens to patients and the spread of antimicrobial resistance, the adherence of health care workers to recommended hand-hygiene practices has remained unacceptably low. One of the key elements in improving hand-hygiene practice is the use of an alcohol-based hand rub instead of washing with soap and water. An alcohol-based hand rub requires less time, is microbiologically more effective, and is less irritating to skin than traditional hand washing with soap and water. Therefore, alcohol-based hand rubs should replace hand washing as the standard for hand hygiene in health care settings in all situations in which the hands are not visibly soiled. It is also important to change gloves between each patient contact and to use hand-hygiene procedures after glove removal. Reducing health care-associated infections requires that health care workers take responsibility for ensuring that hand hygiene becomes an everyday part of patient care.

Anti-Infective Agents, Local↗
PubMed1989

Grip strength and hand dominance: challenging the 10% rule.

The purpose of this study was to test the utility of the 10% rule in hand rehabilitation. The 10% rule states that the dominant hand possesses a 10% greater grip strength than the nondominant hand. This rule has been used for many years to assist therapists in setting strength goals for patients with injured hands. The sample for this study consisted of 310 male and female students, faculty, and staff from a small, private liberal arts college located in Pennsylvania. Grip strength was measured with a factory-calibrated Jamar dynamometer. Results showed an overall 10.74% grip strength difference between dominant and nondominant hands. This finding verified the 10% rule. However, when the data were separated into left-handed and right-handed subjects, a 12.72% difference for right-handed subjects and a -0.08% difference for left-handed subjects was found. In conclusion, this study showed that the 10% rule is valid for right-handed persons only; for left-handed persons, grip strength should be considered equivalent in both hands.

Adolescent↗
PubMed1990

Shoulder shrug--a prognostic sign for recovery of hand movement after stroke.

A new clinical sign with prognostic significance for recovery of hand movements after stroke is described. Thirty-two patients with hemispheric cerebrovascular accident were assessed to determine whether the ability to shrug the hemiplegic shoulder at initial assessment correlated with the recovery of hand movements. The results of 29 of these patients with poor hand movements at initial assessment were analysed. Of 18 patients with absent shoulder shrug, only two patients (11%) showed return of good active movements in the involved hand at final evaluation, whereas eight (73%) of 11 patients who could shrug the hemiplegic shoulder at initial assessment went on to recover good movements in the hand (P = 0.00). In a subgroup of patients who demonstrated only synergistic flexion of fingers in the hemiplegic hand, one of five patients with absent shoulder shrug showed good hand movements at the final assessment in contrast to six of seven patients who initially could shrug the hemiplegic shoulder. Only one of 15 patients who showed total absence of hand movements at the initial assessment had a return of good hand movements. The data suggest that clinical assessment of shoulder shrug is a good prognostic indicator for recovery of voluntary movements in the hemiplegic hand especially when any hand movement, even if it is only synergistic finger flexion, is present at initial assessment. Total absence of hand movements at initial assessment is a poor prognostic sign.

Adult↗
PubMed2006

Effect of two different sized hand paddles on the front crawl stroke kinematics.

AIM: The purpose of the present study was to determine the effect of two different sized hand paddles on the three-dimensional underwater stroke pattern of front crawl swimming at a fixed stroke rate. METHODS: Nine male adolescent competitive freestyle swimmers participated in the study. Each subject swam a series of 25 m trials at a constant stroke rate, without and with hand paddles of two different cross sectional areas (small paddles: 116 cm(2), large paddles: 311 cm(2)). An acoustic metronome connected with a sound amplifier was used to help the subject keep the stroke rate constant. Stroke rate was calculated for each subject using the time for 3 complete right arm stroke cycles. The underwater motion of each subject's right arm was filmed using two S-VHS cameras, operating at 60 fields/s, which were located behind two underwater viewing windows. The spatial coordinates of selected points on the right arm and the hip were calculated using the DLT procedure with 30 control points and after the digital filtering of the raw data with a cut-off frequency of 6 Hz, the hand's linear displacements and velocities, as well as the mean swimming velocity, were calculated. Moreover, the displacement of the hip in the direction of propulsion, from the right hand's entry to the next entry of the same hand, was calculated in order to determine the stroke length. For the statistical treatment of the data the analysis of variance for dependent samples was used. RESULTS: The analysis of the data revealed that when hand paddles were worn, the stroke length (F(2,16)=10.329; P<0.05) and the mean swimming velocity (F(2),16=5.076; P<0.05) were significantly increased, while the temporal characteristics of the underwater stroke and the displacement of the hand were not significantly altered. On the other hand, the peak backward hand speeds during the insweep (F(2,16)=4.794; P<0.05) and the push phase (F(2,16)=5.827; P<0.05) were greatly reduced. These modifications were greater when large paddles were worn. CONCLUSIONS: From the results of the present study it was concluded that the movement pattern was not significantly modified when swimmers swam with hand paddles, at a constant stroke rate. However, large hand paddles caused a decrease in their hand velocities during the underwater stroke.

Adolescent↗
PubMed1986

Individual and environmental risk factors for hand eczema in hospital workers.

Individual and environmental risk factors in hand eczema have been investigated in a prospective cohort study of 2452 newly employed hospital workers with a follow-up time of 20 months. Current hand eczema was analyzed in 142 wet hospital workers from this cohort with respect to the etiologic importance of irritants, allergens and contact urticants. The density of the microflora and the effect on the microflora of topical treatment with a potent corticosteroid were studied in 20 patients with hand eczema. 'Wet' hospital work was found to increase the odds of developing hand eczema only twice compared to 'dry' office work. Nursing children under four years old and the lack of a dish-washing machine significantly increased the risk of contracting hand eczema. Unfavourable combinations of these domestic factors increased the risk as much as wet work. A history of atopic dermatitis approximately tripled the odds both in wet as well as in dry work. Histories of earlier hand eczema (HHE), metal dermatitis (HMD) and of atopy were analyzed as risk factors for hand eczema in 1857 women in wet work. HHE increased the odds by a factor of 12.9 and created a subdivision of the population into high risk individuals and normal risk individuals. HHE was found in half of the subjects with atopic dermatitis, in one quarter of the subjects with atopic mucosal symptoms and in one fifth of the non-atopics. A HMD increased the odds by a factor of 1.8. This increase was seen as a high risk level in subjects with HHE and as a normal risk level in subjects with no HHE. A history of atopic disease as a complement to information about HHE and HMD increased the odds by another 1.3 times. The predicted probability of developing hand eczema ranged from 91% in subjects with a combination of HHE, HMD and atopy to 24% in subjects with none of these risk factors. Subjects with AD were found to suffer a more severe form of hand eczema with significantly higher figures for medical consultation, sick-leave, termination due to hand eczema, early debut, permanent symptoms and vesicular lesions. Amongst the patients investigated for current hand eczema high risk individuals were overrepresented. It was claimed in 92.3% of the cases that trivial irritant factors had elicited the current episodes of hand eczema. In 35% of the cases the exposure to the irritant took place largely at home.(ABSTRACT TRUNCATED AT 400 WORDS)

Dermatitis, Occupational↗
PubMed1997

Sampling arterialised-venous blood from a dorsal-hand vein during exercise without compromising a competitive cycling position.

The arterialisation of dorsal-hand venous blood, using a new hand-heating sleeve that did not disrupt a normal competitive cycling position, was evaluated in 10 male cyclists. Hand-heating was achieved by pumping heated water through a rubberised panel which rested against the dorsal and ventral surfaces of the right hand. Subjects were cannulated near the dorsal venous arch in both hands and blood samples were collected simultaneously at rest under normothermic conditions for 9 subjects, and at rest and after 10, 20 and 30 min of exercise at 50% of the anaerobic threshold for 10 subjects, when only the right hand was heated. No bilateral differences for PO2, PCO2 or pH were observed between normothermic hands at rest (p > 0.05). The heating sleeve increased the hand temperature (p < 0.05) and produced a significant (p < 0.05) arterialisation of blood samples collected from a dorsal-hand vein, compared to values observed in the non-heated hand, at rest and during 30 min of exercise. PO2 and pH were about 10 mm Hg and 0.01 units higher, and PCO2 was about 1.5 mm Hg lower, for samples collected from the heated compared to the non-heated hand. This new method of hand-heating was effective in arterialising venous blood and minimised the need for variation to a normal, competitive cycling position.

Acid-Base Equilibrium↗
PubMed2005

Dyslexia and across-hands finger localization deficits.

Two experiments on finger localization are reported. Experiment 1 compared children who were poor readers with two groups of children matched to poor readers for sex and either age (CA controls) or reading age (RA controls). The participant's hands were kept out of his or her sight in a semi-open box while the fingers of one hand were lightly touched by the experimenter. The participant's task was to indicate, using the thumb of either the same hand (within-hand condition) or the opposite hand (across-hands condition) to respond, the finger(s) which had been touched by the experimenter. Performance was significantly impaired in the across-hands condition compared with the within-hand condition. Experiment 2 was carried out with dyslexic adults and a control group of normal readers. Using the same method of responding as in Experiment 1, a significant deficit in the across-hands condition compared to the within-hand condition was found for both groups. The effect was also obtained for both groups when participants were required to point to the relevant fingers on a photograph of a hand rather than use the thumb of the opposite hand to respond. The results are discussed in relation to the hypothesis of a deficit in inter-hemispheric transfer of tactile information in dyslexia.

Adult↗
PubMed2001

Lateral preference patterns as possible correlates of successfully switched left hand writing: data and a theory.

Left-handers often have had to contend with pressure to switch their preferred writing hand and shift attempt reports are common, especially among older adult left-handers. Three groups of left-handers can be defined by combining two variables, writing hand side and the report of a rightward hand preference shift attempt. The three groups are, first, right hand writers who report a rightward shift (successfully shifted left-handers); second, left hand writers who report a rightward shift attempt (unsuccessfully shifted left-handers); and, finally, left hand writers who do not report a rightward shift attempt. The underlying mechanisms that determine the success or failure of a handwriting shift attempt remain unclear. The present study examined the history of attempts to switch the preferred writing hand in a sample of 1277 adults aged 65 to 100 years of age. Older adults are well suited to participate in such a study because pressure to switch hand preference was especially severe for those who grew up in the early part of the 20th century; reports of rightward shift attempts are more common in this age group than among younger adults. Our results suggest that the three groups of left-handers, distinguished by the presence or absence of a shift history report and writing hand side, can also be distinguished from each other on the basis of their overall lateral preference profiles (the sides of hand, foot, eye, and ear preferences). Left hand writers, with and without reports of a rightward shift history, showed stronger left side lateralisation patterns when compared to right hand writers who reported a rightward switch (the successfully shifted left-handers).

Journal Article↗
PubMed2000

Left tactile extinction following visual stimulation of a rubber hand.

In close analogy with neurophysiological findings in monkeys, neuropsychological studies have shown that the human brain constructs visual maps of space surrounding different body parts. In right-brain-damaged patients with tactile extinction, the existence of a visual peripersonal space centred on the hand has been demonstrated by showing that cross-modal visual-tactile extinction is segregated mainly in the space near the hand. That is, tactile stimuli on the contralesional hand are extinguished more consistently by visual stimuli presented near the ipsilesional hand than those presented far from it. Here, we report the first evidence in humans that this hand-centred visual peripersonal space can be coded in relation to a seen rubber replica of the hand, as if it were a real hand. In patients with left tactile extinction, a visual stimulus presented near a seen right rubber hand induced strong cross-modal visual-tactile extinction, similar to that obtained by presenting the same visual stimulus near the patient's right hand. Critically, this specific cross-modal effect was evident when subjects saw the rubber hand as having a plausible posture relative to their own body (i.e. when it was aligned with the subject's right shoulder). In contrast, cross-modal extinction was strongly reduced when the seen rubber hand was arranged in an implausible posture (i. e. misaligned with respect to the subject's right shoulder). We suggest that this phenomenon is due to the dominance of vision over proprioception: the system coding peripersonal space can be 'deceived' by the vision of a fake hand, provided that its appearance looks plausible with respect to the subject's body.

Aged↗
PubMed2005

Saying 'goodbye' to single-handed practices; what do patients and staff lose or gain?

BACKGROUND: The practice setting is, next to the GP and staff, an important determinant of the quality of care. Differences between single-handed practices and group practices in practice management and organization could therefore provide clues for improvement. An explorative, cross sectional survey was conducted in 766 general practices in The Netherlands comparing single-handed practices with group practices. OBJECTIVE: The study is looking for answers on aspects of the organization and management that are lost or gained when single-handed GPs and practices are replaced by group practices. METHODS: Between 1999 and 2003 GPs and their practices were assessed using a validated practice visit method (VIP) consisting of 303 indicators describing 56 dimensions of practice management. Instruments used consisted of questionnaires for patients, GPs, practice assistant and a direct observer in the practice. Single-handed practices (1 GP) were compared to group practices or health centres (>2.0 GPs) comparing raw scores on dimensions of practice management. In addition, data were analysed in a regression model with specific aspects of practice management as dependent variables using a general linear model procedure. Independent variables included 'single-handed/group practice', 'rural/ urban' 'part-time/full-time' and 'male/female'. RESULTS: Group practices scored better on nearly all aspects of infrastructure except those rated by patients. Patients gave single-handed practices higher marks for service, accessibility and even for the facilities. In single-handed practices GPs reported that they worked more and experienced higher levels of job stress. They delegated less of the medical technical tasks but there is no difference in delegation of preventive tasks/treatment of chronic diseases. Group practices had more computerized medical information and more quality assurance activities, but gave less patient information. Single-handed practices spent more hours on continuous medical education. DISCUSSION AND CONCLUSION: The quality of the practice infrastructure and the team scored better in group practices, but patients appreciated the single-handed practice better. The advantages of single-handed practices could be a challenge for group practices to give better personal, continuous care and to put the patient perspective before organizational considerations. This is underlined by the better score on patient information of single-handed practices. Single-handed practices can reduce their vulnerability and openness to high demand by opening up to the requirements of organised primary care.

Family Practice↗
PubMed1984

Development of motor co-ordination by normal left-handed children.

Ninety-six normal left-handed children were tested for motor co-ordination on a series of timed repetitive tasks, alternating left and right hands, feet and fingers. Preferred hand advantage could be demonstrated to the same degree for the left hand of these children as it had been for the preferred right hand in previously studied groups of the same age (Denckla 1973, 1974). The only test (finger to thumb successive opposition) that failed to show a preferred hand advantage in left-handers also had failed to show such an advantage among right-handers. This same test was performed more rapidly by left-handed girls than boys, as it had been by right-handed girls. However, left-foot superiority appeared to be less well established among left-handers than superiority of the right foot among right-handers, and at a later age. Left-handed children were less likely than their right-handed counterparts to choose their preferred hand when trying out a new task. Writing posture, i.e. whether inverted or straight, could not be established unambiguously for the left-handed children up to the age of 10, and often differed for writing and printing.

Child↗
PubMed2003

Hand rolling cigarette papers as the reference point for regulating cigarette fire safety.

AIM: To compare the burning characteristics of the tobacco and paper of manufactured and hand rolled cigarettes, and set a fire safety standard of manufacture to largely reduce the fire risk from discarded cigarettes. METHODS: (1) Cigarette extinction test of ignition strength: 40 cigarettes per brand, lit and placed on 15 layers of filter paper, in accordance with ASTM test standard E2187-02. (2) Citrate extracted by 0.1N hydrochloric acid from cigarette papers and from tobacco in manufactured cigarettes, the supernatant analysed by high performance liquid chromatography using ultraviolet visual light spectrophotometer. (3) Survey of 750 nationally representative adults age 18 years and over, by telephone, including 184 smokers. MATERIALS: (a) New Zealand made Holiday, and Horizon, and US made Marlboro manufactured cigarettes; (b) US manufactured Merit with banded paper; (c) Holiday, Horizon and Marlboro hand rolling tobaccos, hand rolled in Rizla cigarette papers; (d) manufactured cigarettes as in (a), reconstructed using Rizla hand rolling cigarette papers. RESULTS: 1. (a) For each brand of manufactured cigarettes, 40/40 burnt full length; (b) for Merit banded paper cigarettes 29/40 (73%) burnt full length; (c) for each brand of hand rolled cigarettes 0/40 burnt full length; (d) 0/40 manufactured cigarettes reconstructed with Rizla hand rolling paper burnt full length. 2. Citrate content: (a) In manufactured cigarette papers: 0.3-0.8 mg; in tobacco of manufactured cigarettes: Holiday 0, Horizon 0, Marlboro 8.8 mg; (b) Merit: in banded paper 0.418 mg; in tobacco 10.23 mg; (c) In hand rolled cigarettes: in the papers < 0.08 mg; in hand rolled tobacco 13.3-15.0 mg; (d) In hand rolling papers of reconstructed cigarettes: < 0.018 mg. 3. Requiring manufactured cigarettes to compulsorily self-extinguish when left unattended was supported by 67% of smokers, 61% of manufactured cigarette smokers, 82% of hand rolled smokers, and by 68% of non-smokers. CONCLUSION: The wrapping paper is a key determinant of whether or not unpuffed cigarettes burn their full length. Using international test methods, popular brands of manufactured cigarettes all burnt full length, but none did so when re-wrapped in hand rolling cigarette paper. This provides a ready-to-hand smoker acceptable standard for reducing ignition potential from manufactured cigarettes, as a basis for regulation or litigation.

Adolescent↗
PubMed1994

Interactions between the eye and hand motor systems: disruptions due to cerebellar dysfunction.

1. We tested the hypothesis that interactions occur between eye and hand movements produced in conjunction. This was accomplished by having human subjects with cerebellar dysfunction and age-matched controls perform two tasks: 1) tracking a moving target with the hand and 2) performing a pointing movement to intercept the target. Our prediction was that the inaccuracies that are characteristic of eye and hand movements generated in isolation by cerebellar subjects would be accentuated in each system during combined eye-hand tasks. 2. The cerebellar subjects took longer to respond to the onset of target motion in both tasks. This was true for both the eyes and hand, regardless of whether the eye and hand movements were generated in isolation or in conjunction with each other. 3. The cerebellar subjects also displayed a larger degree of error and/or variability in their hand movements than the control subjects. A significant amount of this increased variability was due to systematic changes in the trajectory of the hand during the critical periods leading up to and after each ocular saccade. These systematic changes were consistent with an overestimation of target velocity in the perifoveal visual field. 4. The increased variability of the cerebellar subjects' hand movements was markedly reduced by restricting eye movements. A similar reduction in variability occurred when vision of the hand was restricted in the tracking task. This effect was accompanied by improved eye movements. 5. For both sets of subjects the eye movements were affected by the hand movements produced in the tracking task. In particular, eye movement accuracy was improved in the controls and degraded in the cerebellar subjects when compared with the eye movements generated in isolation. In contrast, no changes were observed in the interception task. 6. Taken together, these results imply that a reciprocal interaction occurs between the eye and hand motor systems and/or that common "upstream" sites influence each of these systems in a similar manner. The functional anatomy and neurophysiological characteristics of several sites where such interactions may take place are discussed.

Adult↗
PubMed2006

Reaching with alien limbs: visual exposure to prosthetic hands in a mirror biases proprioception without accompanying illusions of ownership.

In five experiments, we investigated the effects of visual exposure to a real hand, arubber hand, or a wooden block on reaching movements made with the unseen left hand behind a parasagittal mirror. Participants reached from one of four starting positions, corresponding to four levels of conflict between the proprioceptively and visually specified positions of the reaching hand. Reaching movements were affected most by exposure to the real hand, intermediately by the rubber hand, and least of all by the wooden block When the posture and/or movement of the visible hand was incompatible with that of the reaching hand, the effect on reaching was reduced. A "rubber hand illusion" questionnaire revealed that illusions of ownership of the rubber hand were not strongly correlated with reaching performance. This research suggests that proprioception is recalibrated following visual exposure to prosthetic hands and that this recalibration is independent of the rubber hand illusion.

Adolescent↗
PubMed1989

[A case of left hand agraphia without callosal apraxia].

A 65-year-old male who had agraphia confined to the left hand was reported. The patient was admitted to the neurological department of Kasugai city Hospital because of suddenly-developed mild right-sided hemiparesis with central facial palsy. Computerized tomography of the brain was performed 2 and 14 days after admission. As a result, low-density regions were found in the left cingulate and medial frontal gyri and the trunk of the corpus callosum. Magnetic resonance imaging of the saggital plane more clearly visualized a localized infarction affecting both the trunk of the corpus callosum and its leftward outflow. Neuropsychological findings of the patient were summarized as follows. 1) He had no difficulty in any of the actual use of object, copying the manipulation of objects, and proper use of objects according to verbal commands. 2) With the eyes closed, he could correctly name the objects handed over to the right hand, while he could do only 15 out of 20 objects handed over to the left hand. However, whichever hand an object was handed to, he could explain how to use the object. 3) He could write Hiragana, Katakana, and Kanji correctly with his right hand in accordance with verbal commands, whereas with his left hand he could do only for 20% of Hiragana, 20% of Katakana, and 90% of Kanji. 4) He could copy Kanji, Hiragana, and figures with either right or left hand. 5) He could point out verbally-presented letters using letter cards whether with the right hand or with the left hand, and could also select the letter card corresponding to the letter visually-presented.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed2005

The use of the hand anatomic index to assess deformity and impaired function in systemic sclerosis.

To determine the "hand anatomic index" (HAI--a quantitative measure of hand deformity) in systemic sclerosis (scleroderma) and to compare it with the other measures of hand deformity and functional impairment. The HAI (measure of open hand span minus closed hand span/lateral height of hand) was determined in 30 patients with scleroderma and compared with hand deformity (as assessed by two independent rheumatologists) and with the Health Assessment Questionnaire (mHAQ), hand strength and prehensile gripability data. The HAI was confirmed as a reliable measure which clearly distinguished patients with increasing hand deformity and separated patients with diffuse scleroderma (n=12) from limited scleroderma (n=18), P=0.005. The HAI correlated significantly with measures of global functional impairment (as measured by the mHAQ) r=-0.46, P=0.01, hand strength r=0.51, P=0.0001 and prehensile gripability, r=-0.37, P=0.05 but neither with disease duration r=-0.16, P=NS nor age at disease onset r=0.20, P=NS. It was estimated that the HAI accounts for ~25% of the total global disability (as measured by HAQ). Measurement of the HAI in scleroderma provides a reliable and objective measure reflecting variable degrees of hand deformity and functional impairment and might provide a valid clinical outcome measure in patients with this disabling disorder.

Adult↗
PubMed2003

Neural control of on-line guidance of hand reaching movements.

Orienting one's gaze towards a peripheral target is usually composed of a hypometric primary saccade followed by a secondary 'corrective saccade' triggered automatically (without conscious perception) by the retinal error at the end of the primary saccade and characterised by a short latency. Due to visual suppression during the saccade, the artificial introduction of a random small target jump during that short period remains undetected and triggers after the end of the primary saccade a normal 'corrective saccade'. As a result this procedure simulates an error in the planning of the primary saccade. On the other hand optimum hand pointing (trade-off between movement time and accuracy) is considered classically to involve a natural parallel initiation of saccade and hand response based on a poor peripheral retinal location, and a further amendment of the hand motor response based on the retinal error provided by the simultaneous vision of target and hand during the movement home phase. To test the hypothesis that the retinal feedback at the end of the primary saccade is used to update the visual target position and amend the ongoing hand motor response, we developed a paradigm involving both an optimum hand pointing and an undetected random target perturbation during the orienting saccade. In order to show that the amendments were controlled by a loop comparing the perceived target location with the dynamic hand position signal, vision of the limb was removed at movement onset. Results showed that the movement was smoothly monitored on-line without additional time processing demands. This functional property of flexibility of the ongoing hand motor response, was generalized from movement extent to movement direction. The undetectability of the perturbation at a conscious level was not a prerequisite for motor flexibility, which was further shown to depend on a critical phase of the limb movement beyond which the latter was no longer amendable, even when the limb was visible. The hand pointing flexibility was further generalised from pointing to the more complex hand reaching and grasping process. It was shown that the flexibility of both the transport and the grasp components were closely coupled. A careful analysis of the data suggested the controlled variable to be the general posture of the upper limb, reaching Bernstein's intuitions about redundancy reduction in skeletomotor systems with degrees of freedom in excess. A kinematics study of the motor flexibility of reaching and grasping in a patient with a bilateral optic ataxia favoured the idea of a posterior parietal cortex involvement in the error processing underlying motor flexibility, reaching the same conclusions as other recent studies using either Positron Emission Tomography or Transcranial Magnetic Stimulation.

Hand↗