The role of ventral medial wall motor areas in bimanual co-ordination. A combined lesion and activation study.
(9/3335)
Two patients with midline tumours and disturbances of bimanual co-ordination as the presenting symptoms were examined. Both reported difficulties whenever the two hands had to act together simultaneously, whereas they had no problems with unimanual dexterity or the use of both hands sequentially. In the first patient the lesion was confined to the cingulate gyrus; in the second it also invaded the corpus callosum and the supplementary motor area. Kinematic analysis of bimanual in-phase and anti-phase movements revealed an impairment of both the temporal adjustment between the hands and the independence of movements between the two hands. A functional imaging study in six volunteers, who performed the same bimanual in-phase and anti-phase tasks, showed strong activations of midline areas including the cingulate and ventral supplementary motor area. The prominent activation of the ventral medial wall motor areas in the volunteers in conjunction with the bimanual co-ordination disorder in the two patients with lesions compromising their function is evidence for their pivotal role in bimanual co-ordination. (+info)
The effects of age on human venous responsiveness to neuropeptide Y.
(10/3335)
AIMS: Neuropeptide Y (NPY) is a sympathetic neurotransmitter released with noradrenaline during sympathetic stimulation. Ageing has been shown to be associated with a reduction in alpha2 and beta-adrenoceptor mediated responses in veins, but it is not known whether NPY responsiveness is also altered with increasing age. METHODS: Using a dorsal hand vein technique, we examined NPY receptor responsiveness in 24 normal, healthy subjects (20-72 years; 10 males, 14 females). Graded infusions of NPY (25-2000 pmol min(-1)) were administered (5 min at each dose) into a dorsal hand vein. Venous distension at 45 mmHg was measured at 3-5 min of each infusion. Dose-response curves to NPY were constructed and the peak venoconstriction was calculated. RESULTS: Dose-dependent venoconstriction was seen in all but one subject. The peak venoconstriction observed with NPY was significantly and negatively correlated with the age of the normal subjects (r=-0.63, P<0.01). When subjects were ranked from youngest to oldest and divided into tertiles, (20-40 years, n = 8; 41-55 years, n = 8; 56-72 years, n = 8), mean dose-response curves were different with the oldest tertile being significantly less responsive (P<0.05). The peak venoconstriction observed (% of control) was 65.1+/-7.0, 46.5+/-9.4, and 24.4+/-4.8%, respectively. The oldest tertile had a significantly decreased peak venoconstriction compared with the youngest tertile (P<0.01). Infusion of NPY into a dorsal hand vein had no systemic effects on heart rate or blood pressure in any of the subjects studied. CONCLUSIONS: Hand vein responsiveness to exogenously infused NPY in normal subjects is decreased as age increases. The reduction of NPY-receptor-mediated responses with age may influence sympathetic nervous system control of the venous system with advancing age. (+info)
Role of nitric oxide in isoprenaline and sodium nitroprusside-induced relaxation in human hand veins.
(11/3335)
AIMS: Recent reports, largely in animal models, have suggested that either inhibition of nitric oxide (NO) synthase or endothelium removal in arteries inhibits the response to isoprenaline, a beta-adrenoceptor agonist, and also enhances the response to sodium nitroprusside, a nitrovasodilator. This in vivo study was designed to determine whether N(G)-monomethyl-L-arginine (L-NMMA), an inhibitor of NO synthesis, influences relaxation of human hand veins mediated by isoprenaline or by sodium nitroprusside. METHODS: Using the dorsal hand vein technique, full dose-response curves to bradykinin (0.27-278 ng min(-1), n=6), isoprenaline (2.12-271 ngmin(-1), n=8) and sodium nitroprusside (0.01-634 ng min(-1) n=7) were generated on separate occasions before and after L-NMMA co-infusion (50 microg min(-1)). RESULTS: In veins preconstricted with the alpha1-adrenoceptor-selective agonist phenylephrine, the three vasodilators induced maximal responses (Emax) of 119+/-35, 72+/-18 and 103+/-17%, respectively. L-NMMA inhibited relaxation to bradykinin by 64% (P=0.014) but did not influence relaxation induced by isoprenaline. The sensitivity to sodium nitroprusside was significantly enhanced by L-NMMA co-infusion (concentration shift of 2.3, P=0.031). CONCLUSIONS; We conclude that in human veins, spontaneously released NO does not play a major role in isoprenaline-induced relaxation. Our results also suggest that the effects of sodium nitroprusside in this vascular bed may be attenuated by endothelium-derived NO. (+info)
Task-dependent modulation of 15-30 Hz coherence between rectified EMGs from human hand and forearm muscles.
(12/3335)
1. Recent reports have shown task-related changes in oscillatory activity in the 15-30 Hz range in the sensorimotor cortex of human subjects and monkeys during skilled hand movements. In the monkey these oscillations have been shown to be coherent with oscillatory activity in the electromyographic activity of hand and forearm muscles. 2. In this study we investigated the modulation of oscillations in the electromyogram (EMG) of human volunteers during tasks requiring precision grip of two spring-loaded levers. 3. Two tasks were investigated: in the 'hold' task, subjects were required to maintain a steady grip force (ca 2.1 N or 2.6 N) for 8 s. In the 'ramp' task, there was an initial hold period for 3 s (force ca 2.1 N) followed by a linear increase in grip force over a 2 s period. The task ended with a further steady hold for 3 s at the higher force level (ca 2.6 N). 4. Surface EMGs were recorded from five hand and forearm muscles in 12 subjects. The coherence of oscillatory activity was calculated between each muscle pair. Frequencies between 1 and 100 Hz were analysed. 5. Each subject showed a peak in the coherence spectra in the 15-30 Hz bandwidth during the hold task. This coherence was absent during the initial movement of the levers. During the ramp task the coherence in the 15-30 Hz range was also significantly reduced during the movement phase, and significantly increased during the second hold period, relative to the initial hold. 6. There was coherence between the simultaneously recorded magnetoencephalogram (MEG) and EMG during steady grip in the hold task; this coherence disappeared during the initial lever movement. Using a single equivalent current dipole source model, the coherent cortical activity was localized to the hand region of the contralateral motor cortex. This suggests that the EMG-EMG coherence was, therefore, at least in part, of cortical origin. 7. The results are discussed in terms of a possible role for synchrony in the efficient recruitment of motor units during maintained grip. (+info)
The associations of bone mineral density and bone turnover markers with osteoarthritis of the hand and knee in pre- and perimenopausal women.
(13/3335)
OBJECTIVE: To determine whether Caucasian women ages 28-48 years with newly defined osteoarthritis (OA) would have greater bone mineral density (BMD) and less bone turnover over time than would women without OA. METHODS: Data were derived from the longitudinal Michigan Bone Health Study. Period prevalence and 3-year incidence of OA were based on radiographs of the dominant hand and both knees, scored with the Kellgren/Lawrence (K/L) scale. OA scores were related to BMD, which was measured by dual-energy x-ray absorptiometry, and to serum osteocalcin levels, which were measured by radioimmunoassay. RESULTS: The period prevalence of OA (K/L grade > or =2 in the knees or the dominant hand) was 15.3% (92 of 601), with 8.7% for the knees and 6.7% for the hand. The 3-year incidence of knee OA was 1.9% (9 of 482) and of hand OA was 3.3% (16 of 482). Women with incident knee OA had greater average BMD (z-scores 0.3-0.8 higher for the 3 BMD sites) than women without knee OA (P < 0.04 at the femoral neck). Women with incident knee OA had less change in their average BMD z-scores over the 3-year study period. Average BMD z-scores for women with prevalent knee OA were greater (0.4-0.7 higher) than for women without knee OA (P < 0.002 at all sites). There was no difference in average BMD z-scores or their change in women with and without hand OA. Average serum osteocalcin levels were lower in incident cases of hand OA (>60%; P = 0.02) or knee OA (20%; P not significant). The average change in absolute serum osteocalcin levels was not as great in women with incident hand OA or knee OA as in women without OA (P < 0.02 and P < 0.05, respectively). CONCLUSION: Women with radiographically defined knee OA have greater BMD than do women without knee OA and are less likely to lose that higher level of BMD. There was less bone turnover among women with hand OA and/or knee OA. These findings suggest that bone-forming cells might show a differential response in OA of the hand and knee, and may suggest a different pathogenesis of hand OA and knee OA. (+info)
The neural consequences of conflict between intention and the senses.
(14/3335)
Normal sensorimotor states involve integration of intention, action and sensory feedback. An example is the congruence between motor intention and sensory experience (both proprioceptive and visual) when we move a limb through space. Such goal-directed action necessitates a mechanism that monitors sensorimotor inputs to ensure that motor outputs are congruent with current intentions. Monitoring in this sense is usually implicit and automatic but becomes conscious whenever there is a mismatch between expected and realized sensorimotor states. To investigate how the latter type of monitoring is achieved we conducted three fully factorial functional neuroimaging experiments using PET measures of relative regional cerebral blood flow with healthy volunteers. In the first experiment subjects were asked to perform Luria's bimanual co-ordination task which involves either in-phase (conditions 1 and 3) or out-of-phase (conditions 2 and 4) bimanual movements (factor one), while looking towards their left hand. In half of the conditions (conditions 3 and 4) a mirror was used that altered visual feedback (factor two) by replacing their left hand with the mirror image of their right hand. Hence (in the critical condition 4) subjects saw in-phase movements despite performing out-of-phase movements. This mismatch between intention, proprioception and visual feedback engendered cognitive conflict. The main effect of out-of-phase movements was associated with increased neural activity in posterior parietal cortex (PPC) bilaterally [Brodmann area (BA) 40, extending into BA 7] and dorsolateral prefrontal cortex (DLPFC) bilaterally (BA 9/46). The main effect of the mirror showed increased neural activity in right DLPFC (BA 9/ 46) and right superior PPC (BA 7) only. Analysis of the critical interaction revealed that the mismatch condition led to a specific activation in the right DLPFC alone (BA 9/46). Study 2, using an identical experimental set-up but manipulating visual feedback from the right hand (instead of the left), subsequently demonstrated that this right DLPFC activation was independent of the hand attended. Finally, study 3 removed the motor intentional component by moving the subjects' hand passively, thus engendering a mismatch between proprioception and vision only. Activation in the right lateral prefrontal cortex was now more ventral than in studies 1 or 2 (BA 44/45). A direct comparison of studies 1 and 3 (which both manipulated visual feedback from the left hand) confirmed that a ventral right lateral prefrontal region is primarily activated by discrepancies between signals from sensory systems, while a more dorsal area in right lateral prefrontal cortex is activated when actions must be maintained in the face of a conflict between intention and sensory outcome. (+info)
Successful replantation of a hand amputated through the metacarpus.
(15/3335)
A successful replantation is reported of a hand completely severed by a circular saw through all five metacarpals. The sequence of primary reconstruction of all important structures beginning three hours after the injury and the functional results eighteen months later are presented. (+info)
Radial club hand with absence of the biceps muscle treated by centralisation of the ulna and triceps transfer. Report of two cases.
(16/3335)
Two children with radial club hand and absence of the biceps muscle were treated by centralisation of the ulna into the carpus and triceps transfer. The two operations were performed only a short time apart so that the period between the procedures could be used to stretch the triceps and to enable the children to adapt to an altered position of the wrist and to mobility of the elbow at one step and following a single period of plaster immobilisation. It is very likely that function is better than it would have been had the condition remained untreated. Before operation the children had only a crude hook function of the hand against the forearm and could not bring the hand to the mouth. Even if function is not much improved, the improvement in appearance is considerable and is by itself sufficient to justify the procedures. (+info)