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PubMed1996

Visual perceptions of head-fixed and trunk-fixed anterior/posterior axes.

The purpose of the present experiment was to determine the preferred visual "straight ahead" or anterior/posterior (a/p) axis at the perceptual level. The ability of 12 neurologically normal, young adult subjects to position a rod parallel to the head and trunk a/p axes while viewing eccentrically located visual targets were studied under six conditions: 1. fixed-subjects stood erect with the head aligned to the trunk and viewed a central target while visually aligning a hand-held rod to the head and trunk a/p axis. 2. eyes-subjects moved only their eyes to view eccentric targets and aligned the rod to the head and trunk a/p axis. 3. head-trunk-subjects viewed the eccentric targets by rotating the head about a vertical axis and aligned the rod to the trunk a/p axis. 4. head-head-subjects viewed the targets as in 3 and positioned the rod parallel to the head a/p axis. 5. trunk-head-subjects viewed the targets by rotating the trunk and head as a unit about the vertical axis and aligned the rod parallel to the head a/p axis (note that the head and trunk a/p axes were misaligned by the experimenter prior to target viewing). 6. trunk-trunk-subjects viewed targets as in 5 and positioned the rod parallel to the trunk a/p axis. Subjects performed 25-35 consecutive trials within each condition. Perceptual errors were similar for aligning the rod to the trunk and head a/p axes; however, moving the trunk produced much larger constant and variable perceptual errors than moving the head. In a second experiment, four subjects controlled the position of a lighted rod held by a robot arm in complete darkness. They were instructed to align the rod to either the head or trunk a/p axis under conditions similar to the fixed, head-trunk, and head-head tasks described above. Perceptual errors were much larger when aligning the rod to the head a/p axis than to trunk a/p axis when the head was moved. This shows that the trunk a/p axis is clearly preferred at the perceptual level when visual background cues are not present. These data strongly suggest that the visual coordinate system uses a trunk-fixed a/p axis to define the subjective straight-ahead direction and right/left position of a target. Implications of these findings for sensorimotor transformations in control of upper limb movements to visual targets are discussed.

Adult↗

PubMed2004

The influence of artificially increased hip and trunk stiffness on balance control in man.

Lightweight corsets were used to produce mid-body stiffening, rendering the hip and trunk joints practically inflexible. To examine the effect of this artificially increased stiffness on balance control, we perturbed the upright stance of young subjects (20-34 years of age) while they wore one of two types of corset or no corset at all. One type, the "half-corset", only increased hip stiffness, and the other, the "full-corset", increased stiffness of the hips and trunk. The perturbations consisted of combined roll and pitch rotations of the support surface (7.5 deg, 60 deg/s) in one of six different directions. Outcome measures were biomechanical responses of the legs, trunk, arms and head, and electromyographic (EMG) responses from leg, trunk, and upper arm muscles. With the full-corset, a decrease in forward stabilising trunk pitch rotation compared to the no-corset condition occurred for backward pitch tilts of the support surface. In contrast, the half-corset condition yielded increased forward trunk motion. Trunk backward pitch motion after forwards support-surface perturbations was the same for all corset conditions. Ankle torques and lower leg angle changes in the pitch direction were decreased for both corset conditions for forward pitch tilts of the support-surface but unaltered for backward tilts. Changes in trunk roll motion with increased stiffness were profound. After onset of a roll support-surface perturbation, the trunk rolled in the opposite direction to the support-surface tilt for the no-corset and half-corset conditions, but in the same direction as the tilt for the full-corset condition. Initial head roll angular accelerations (at 100 ms) were larger for the full-corset condition but in the same direction (opposite platform tilt) for all conditions. Arm roll movements were initially in the same direction as trunk movements, and were followed by large compensatory arm movements only for the full-corset condition. Leg muscle (soleus, peroneus longus, but not tibialis anterior) balance-correcting responses were reduced for roll and pitch tilts under both corset conditions. Responses in paraspinals were also reduced. These results indicate that young healthy normals cannot rapidly modify movement strategies sufficiently to account for changes in link flexibility following increases in hip and trunk stiffness. The changes in leg and trunk muscle responses failed to achieve a normal roll or pitch trunk end position at 700 ms (except for forward tilt rotations), even though head accelerations and trunk joint proprioception seemed to provide information on changed trunk movement profiles over the first 300 ms following the perturbation. The major adaptation to stiffness involved increased use of arm movements to regain stability. The major differences in trunk motion for the no-corset, half-corset and full-corset conditions support the concept of a multi-link pendulum with different control dynamics in the pitch and roll planes as a model of human stance. Stiffening of the hip and trunk increases the likelihood of a loss of balance laterally and/or backwards. Thus, these results may have implications for the elderly and others, with and without disease states, who stiffen for a variety of reasons.

Abdomen↗

PubMed2004

Head-trunk coordination in elderly subjects during linear anterior-posterior translations.

This study examined whether the head of elderly subjects was less stable in space when the trunk was free to move than when the trunk was fixed to a linearly moving platform. Fourteen healthy elderly subjects were seated on a linear sled with their trunk either fixed to the seat or free to move. Subjects received 10 cm, 445 cm/s2 anterior-posterior ramps and 0.35-4.05 Hz sum-of-sines translations while performing a mental distraction task in the dark. Kinematics of the head and trunk were derived from an Optotrak motion analysis system and a linear accelerometer placed on the head. Electromyographic (EMG) signals were collected for neck and paraspinal muscles. Data were tested for significance with paired t-tests corrected for multiple testing and compared (Mann-Whitney U-test) with previously published data from 12 healthy young adults (Keshner 2003). Linear acceleration trajectories of the head corresponded to the direction of sled linear acceleration when the trunk was fixed and countered the direction of the sled when the trunk was free. Angular head accelerations countered the sled or the trunk when the trunk was fixed or free, respectively. Peak amplitudes of head angular acceleration in space were greater with a fixed trunk. With the trunk free, amplitudes of head linear peak acceleration, angular accelerations, and response gains exceeded those of the young adults. Muscle EMG response latencies did not vary with the timing of head acceleration onset but the neck muscles were activated more frequently in a direction consistent with a vestibulocollic or cervicocollic reflex. Differences in angular motion of the head could be explained by the biomechanical constraints of the two tasks having one freely moving mass (head) with the trunk fixed and two freely moving masses (head and trunk) with the trunk free. These data suggest that elderly subjects rely upon active trunk mechanics in order to coordinate their head and trunk motion; however, a contribution by vestibular and ascending segmental inputs cannot be completely ruled out. A less flexible trunk in the elderly could explain why they were not as successful as young adults in stabilizing their heads in space when the trunk was free to move.

Abdomen↗

PubMed2001

Hand trajectory invariance in reaching movements involving the trunk.

Movements of different body segments may be combined in different ways to achieve the same motor goal. How this is accomplished by the nervous system was investigated by having subjects make fast pointing movements with the arm in combination with a forward bending of the trunk that was unexpectedly blocked in some trials. Subjects moved their hand above the surface of a table without vision from an initial position near the midline of the chest to remembered targets placed within the reach of the arm in either the ipsi- or contralateral workspace. In experiment 1, subjects were instructed to make fast arm movements to the target without corrections whether or not the trunk was arrested. Only minor changes were found in the hand trajectory and velocity profile in response to the trunk arrest, and these changes were seen only late in the movement. In contrast, the patterns of the interjoint coordination substantially changed in response to the trunk arrest, suggesting the presence of compensatory arm-trunk coordination minimizing the deflections from the hand trajectory regardless of whether the trunk is recruited or mechanically blocked. Changes in the arm interjoint coordination in response to the trunk arrest could be detected kinematically at a minimal latency of 50 ms. This finding suggests a rapid reflex compensatory mechanism driven by vestibular and/or proprioceptive afferent signals. In experiment 2, subjects were required, as soon as they perceived the trunk arrest, to change the hand motion to the same direction as that of the trunk. Under this instruction, subjects were able to initiate corrections only after the hand approached or reached the final position. Thus, centrally mediated compensatory corrections triggered in response to the trunk arrest were likely to occur too late to maintain the observed invariant hand trajectory in experiment 1. In experiment 3, subjects produced similar pointing movements, but to a target that moved together with the trunk. In these body-oriented pointing movements, the hand trajectories from trials in which the trunk was moving or arrested were substantially different. The same trajectories represented in a relative frame of reference moving with the trunk were virtually identical. We conclude that hand trajectory invariance can be produced in an external spatial (experiment 1) or an internal trunk-centered (experiment 3) frame of reference. The invariance in the external frame of reference is accomplished by active compensatory changes in the arm joint angles nullifying the influence of the trunk motion on the hand trajectory. We suggest that to make a transition to the internal frame of reference, control systems suppress this compensation. One of the hypotheses opened to further experimental testing is that the integration of additional (trunk) degrees of freedom into movement is based on afferent (proprioceptive, vestibular) signals stemming from the trunk motion and transmitted to the arm muscles.

Abdomen↗

PubMed2002

Sequential control signals determine arm and trunk contributions to hand transport during reaching in humans.

When reaching towards objects placed outside the arm workspace, the trunk assumes an active role in transport of the hand by contributing to the extent of movement while simultaneously maintaining the direction of reach. We investigated the spatial-temporal aspects of the integration of the trunk motion into reaching. Specifically, we tested the hypothesis that the efficiency ('gain') of the arm-trunk co-ordination determining the contribution of the trunk to the extent of hand movement may vary substantially with the phase of reaching. Sitting subjects made fast pointing movements towards ipsi- and a contralateral targets placed beyond the reach of the right arm so that a forward trunk motion was required to assist in transporting the hand to the target. Sight of the arm and target was blocked before the movement onset. In randomly selected trials, the trunk motion was unexpectedly prevented by an electromagnet. Subjects were instructed to make stereotypical movements whether or not the trunk was arrested. In non-perturbed trials, most subjects began to move the hand and trunk simultaneously. In trunk-blocked trials, it was impossible for the hand to cover the whole pointing distance but the hand trajectory and velocity profile initially matched those from the trials in which the trunk motion was free, approximately until the hand reached its peak velocity. The arm inter-joint co-ordination substantially changed in response to the trunk arrest at a minimal latency of 40 ms after the perturbation onset. The results suggest that when the trunk was free, the influence of the trunk motion on the hand trajectory and velocity profile was initially neutralized by appropriate changes in the arm joint angles. Only after the hand had reached its peak velocity did the trunk contribute to the extent of pointing. Previous studies suggested that the central commands underlying the transport component of arm movements are completed when the hand reaches peak velocity. These studies, together with the present finding that the trunk only begins to contribute to the hand displacement at peak hand velocity, imply that the central commands that determine the contributions of the arm and the trunk to the transport of the hand are generated sequentially, even though the arm and trunk move in parallel.

Adult↗

PubMed2000

The effects of motion on trunk biomechanics.

OBJECTIVE: To review the literature that evaluates the influence of trunk motion on trunk strength and structural loading. BACKGROUND: In recent years, trunk dynamics have been identified as potential risk factors for developing low-back disorders. Consequently, a better understanding of the underlying mechanisms involved in trunk motion is needed. METHODS: This review summarizes the results of 53 studies that have evaluated trunk motion and its impact on several biomechanical outcome measures. The biomechanical measures consisted of trunk strength, intra-abdominal pressure, muscle activity, imposed trunk moments, and spinal loads. Each of these biomechanical measures was discussed in relation to the existing knowledge within each plane of motion (extension, flexion, lateral flexion, twisting, and asymmetric extension). RESULTS: Trunk strength was drastically reduced as dynamic motion increased, and males were impacted more than females. Intra-abdominal pressure seemed to only be affected by trunk dynamics at high levels of force. Trunk moments were found to increase monotonically with increased trunk motion. Both agonistic and antagonistic muscle activities were greater as dynamic characteristics increased. As a result, the three-dimensional spinal loads increase significantly for dynamic exertions as compared to isometric conditions. CONCLUSIONS: Trunk motion has a dramatic affect on the muscle coactivity, which seems to be the underlying source for the decrease strength capability as well as the increased muscle force, IAP, and spinal loads. This review suggests that the ability of the individual to perform a task "safely" might be significantly compromised by the muscle coactivity that accompanies dynamic exertions. It is also important to consider various workplace and individual factors when attempting to reduce the impact of trunk motions during dynamic exertions. Relevance This review provides insight as to why trunk motions are important risk factors to consider when attempting to control low-back disorders in the workplace. It is apparent that trunk motion increases the risk of low-back disorders. To better control low-back disorders in industry, more comprehensive knowledge about the impact of trunk motion is needed. A better understanding of muscle coactivity may ultimately lead to reducing the risk associated with dynamic exertions.

Abdomen↗

PubMed2006

Trunk performance after stroke and the relationship with balance, gait and functional ability.

OBJECTIVE: To evaluate trunk performance in non-acute and chronic stroke patients by means of the Trunk Control Test and Trunk Impairment Scale and to compare the Trunk Control Test with the Trunk Impairment Scale and its subscales in relation to balance, gait and functional ability after stroke. SUBJECTS: Fifty-one stroke patients, attending a rehabilitation programme, participated in the study. MAIN MEASURES: SUBJECTS were evaluated with the Trunk Control Test, Trunk Impairment Scale, Tnetti balance and gait subscales, Functional Ambulation Category, 10-m walk test, Timed Up and Go Test and motor part of the Functional Independence Measure. RESULTS: Participants obtained a median score of 61 out of 100 on the Trunk Control Test and 11 out of 23 for the Trunk Impairment Scale. Twelve participants (24%) obtained the maximum score on the Trunk Control Test; no subject reached the maximum score on the Trunk Impairment Scale. Measures of trunk performance were significantly related with values of balance, gait and functional ability. Multivariate linear regression analysis showed an additional, significant contribution of the dynamic sitting balance subscale of the Trunk Impairment Scale in addition to the Trunk Control Test total score for measures of gait and functional ability (model R2 = 0.55-0.62). CONCLUSIONS: This study clearly indicates that trunk performance is still impaired in non-acute and chronic stroke patients. When planning future follow-up studies, use of the Trunk Impairment Scale has the advantage that it has no ceiling effect.

Abdomen↗

PubMed2002

Hemispheric specialization in the co-ordination of arm and trunk movements during pointing in patients with unilateral brain damage.

During pointing movements involving trunk displacement, healthy subjects perform stereotypically, selecting a strategy in which the movement is initiated with either the hand or trunk, and where the trunk continues after the end of the hand movement. In a previous study, such temporal co-ordination was not found in patients with left-hemispheric brain lesions reaching with either their dominant paretic or with their non-dominant non-paretic arm. This co-ordination deficit may be associated in part with the presence of a lesion in the dominant left hemisphere. If so, then no deficit should be observed in patients with stroke-related damage in their non-dominant right hemisphere moving with their ipsilesional arm. To verify this, 21 right-hand dominant adults (7 who had had a stroke in the right hemisphere, 7 who had had a stroke in the left hemisphere and 7 healthy subjects) pointed to two targets located on a table in front of them in the ipsilateral and contralateral workspace. Pointing was done under three movement conditions: while not moving the trunk, while bending the trunk forward and while bending the trunk backwards. The experiment was repeated with the non-paretic arm of patients with stroke and for the right and left arms of healthy subjects. Kinematic data were recorded (Optotrak). Results showed that, compared to healthy subjects, arm-trunk timing was disrupted in patients with stroke for some conditions. As in patients with lesions in the dominant hemisphere, arm-trunk timing in those with lesions in the non-dominant hemisphere was equally more variable than movements in healthy subjects. However, patients with dominant hemisphere lesions used significantly less trunk displacement than those with non-dominant hemisphere lesions to accomplish the task. The deficit in trunk displacement was not due to problems of trunk control or sitting balance since, in control experiments, all subjects were able to move the trunk the required distance, with and without the added weight of the limb. Results support the hypothesis that the temporal co-ordination of trunk and arm recruitment during pointing movements is mediated bilaterally by each hemisphere. However, the difference in the range of trunk displacement between patients with left and right brain lesions suggests that the left (dominant) hemisphere plays a greater role than the right in the control of movements involving complex co-ordination between the arm and trunk.

Adult↗

PubMed2002

Differences between trunk sway characteristics on a foam support surface and on the Equitest ankle-sway-referenced support surface.

Clinicians have sought ways to increase trunk sway so that it is easily observed and a balance deficit more easily identified. One technique often used for this purpose is to reduce the efficacy of ankle proprioceptive inputs on sway. To achieve this reduction either a foam mat is used as an unstable support surface or the subject stands on a surface made unstable with servo-driven ankle-sway-referencing. The purpose of the current study was to investigate differences in trunk pitch and roll sway characteristics using these techniques. Trunk sway while standing quietly on two legs was measured in 25 normal subjects in the age range 20-35 years for three support-surface conditions. Each condition was tested twice for 20 s, once with eyes open and once with eyes closed. The three conditions were standing on a foam support surface, standing on a support surface with pitch (fore-aft) ankle-sway-referencing as used for the standard Sensory Organization Test (SOT) of the Neurocom Equitest System (SOT 4 and 5), and standing with roll (lateral) ankle-sway-referencing. The latter was achieved by having the subjects stand turned 90 degrees to the standard SOT position. Two angular velocity sensors mounted on a belt measured trunk sway in the pitch and roll directions. Trunk roll angle and angular velocity amplitudes for pitch sway-referencing were reduced compared to either the foam or roll sway-referencing conditions, but trunk pitch angle and angular velocities amplitudes were greater. For roll sway-referencing, the trunk roll angle was greater than for the other stimulus conditions. Analyses of the trunk sway velocity in the frequency domain indicated that ankle-sway-referencing in the pitch direction increased trunk pitch sway at 1 Hz and decreased trunk roll sway between 2 and 5 Hz compared to foam support frequency spectra. Roll ankle-sway-referencing decreased trunk roll between 2 and 4 Hz only. These results indicate that using a foam support surface provides multidirectional trunk sway with velocity content across all frequencies in the range 0.8-5.2 Hz. Roll ankle-sway-referencing, but not pitch ankle-sway-referencing, yields trunk sway with similar characteristics to those with foam. Pitch ankle-sway-referencing forces pitch trunk resonance to be around 1 Hz and yields very different trunk sway from that obtained with a foam support surface. Roll sway-referencing is an alternative means to test multidirectional control of sway. Clinically though, foam is simpler to use and provides a more difficult balance task for the patient.

Adult↗

PubMed2000

Vulnerability of the sympathetic trunk during the anterior approach to the lower cervical spine.

STUDY DESIGN: Anatomic dissection and measurements of the cervical sympathetic trunk relative to the medial border of the longus colli muscle and lateral angulation of the sympathetic trunk relative to the midline on both sides were performed. OBJECTIVE: To determine the course and location of the sympathetic trunk quantitatively and relate this to the vulnerability of the sympathetic trunk during the anterior approach to the lower cervical spine. SUMMARY OF BACKGROUND DATA: The sympathetic trunk is sometimes damaged during the anterior approach to lower cervical spine, resulting in Horner's syndrome with its associated ptosis, meiosis, and anhydrosis. No quantitative regional anatomy describing the course and location of the sympathetic trunk and its relation to the longus colli muscle is available in the literature. METHODS: In this study, 28 adult cadavers were used for dissection and measurements of the sympathetic trunk. The distance between the sympathetic trunk and the medial borders of the longus colli muscle at C6 and the angle of the sympathetic trunk with respect to the midline were determined bilaterally. The distance between the medial borders of the longus colli muscle from C3 to C6 and the angle between the medial borders of the longus colli muscle also were measured. RESULTS: The sympathetic trunk runs in a superior and lateral direction, with an average angle of 10.4 +/- 3.8 degrees relative to the midline. The average distance between the sympathetic trunk and the medial border of the longus colli muscle is 10.6 +/- 2.6 mm. The average diameter of the sympathetic trunk at C6 is 2.7 +/- 0.6 mm. The length and width of the middle cervical ganglion were 9.7 +/- 2.1 mm and 5.2 +/- 1.3 mm, respectively. The distance between the medial borders of the longus colli muscle was 7.9 +/- 2.2 mm at C3, 10.1 +/- 3.1 mm at C4, 12.3 +/- 3.1 mm at C5, and 13.8 +/- 2.2 mm at C6, and the angle between the medial borders of the longus colli muscle was 12.5 +/- 4. 7 degrees. CONCLUSIONS: The sympathetic trunk may be more vulnerable to damage during anterior lower cervical spine procedures because it is situated closer to the medial border of the the longus colli muscle at C6 than at C3. The longus colli muscles diverge laterally, whereas the sympathetic trunks converge medially at C6. As the transverse foramen or uncovertebral joint is exposed with dissection or transverse severance of the longus colli muscle at the lower cervical levels, the sympathetic trunk should be identified and protected.

Aged↗

PubMed2000

Superposition of independent units of coordination during pointing movements involving the trunk with and without visual feedback.

Previous studies addressing the problem of the control of multiple degrees of freedom have examined the influence of trunk movement on pointing movements within the arm's reach. Such movements may be controlled by two functionally independent units of coordination (synergies): one involving only arm joints and producing the hand trajectory to the target (the transport synergy), and the other coordinating trunk and arm movements leaving the hand trajectory unchanged (the compensatory synergy). The question of whether or not this functional subdivision depends on visual feedback was addressed in the present study. We also tested whether or not the motor effects of different synergies are summated as independent components, a control strategy called "superposition." Finally, we investigated whether or not the relationship between different degrees of freedom within each synergy could be considered linear resulting in proportional changes in different joint angles. Seated subjects produced fast, uncorrected arm movements to an ipsi- or a contralateral target in the direction of +/-45 degrees to the sagittal midline of the trunk. Targets could be reached using the arm alone (control trials) or by combining the arm motion with a forward or backward trunk motion produced by hip flexion or extension (test trials), with and without visual feedback. The shape of the hand trajectory, its direction and tangential velocity, movement precision, joint angles and the sequence of the trunk and hand recruitment and de-recruitment were measured. In both visual conditions, the direction of the hand trajectory observed in control trials was generally preserved in test trials. In terms of sequencing, even in the absence of vision, the trunk movement was initiated before the onset of and outlasted the hand shift, indicating that the potential influence of the trunk on the hand movement was compensated by rotations in the elbow and shoulder joint. The analysis of other variables also implied that the effects of trunk recruitment on the hand trajectory were minor compared to those which could be observed if these effects were not compensated by appropriate changes in the arm joint angles. It was concluded that an arm-trunk compensatory synergy is present in pointing movements regardless of visual feedback. Principal component analysis showed that the relationship between elbow, shoulder and hip joint angles in individual arm and combined arm-trunk movements cannot be considered linear, implying that this relationship is adjusted according to the changing arm geometry. The changes in each arm joint angle (elbow, shoulder) elicited by a forward trunk bending in one block of trials were compared with those elicited by a backward bending in another block, whereas the hand moved to the same target in both blocks. These changes were opposite but of similar magnitude. As a result, for each moment of movement, the mean joint angle obtained by averaging across two directions of trunk motion was practically identical to that in control trials in which the trunk was motionless. It is concluded that the transport and arm-trunk compensatory synergies are combined as independent units, according to the principle of superposition. This principle may simplify the control of the coordination of a redundant number of degrees of freedom.

Adult↗

PubMed2002

[Variations of the celiac trunk branches in the fetus].

The study was performed on 60 human foetuses, aged between 4 to 9 months, using as methods dissection and plastic and contrast substances injection. We studied the celiac trunk in what concerns the division into its terminal branches, insisting on the possible morphological variations, some rare collateral branches starting from the common arterial trunk, the dimensional relations between the branches at their origin and the level of the celiac trunk origin from the aorta, in relation with the vertebral column, the diaphragmatic passage of the aorta and with the superior mesenteric artery. We also assessed the dimensional relations (calibers at origin) between the branches of the celiac trunk. Ass possible variations of the division of the celiac trunk, we assessed: gastro-hepatic trunk, with the splenic artery directly from the aorta or from the hepatic artery; gastro-splenic trunk, with the hepatic artery originating from the aorta; hepato-splenic trunk, with origin of the left gastric artery either directly from the aorta or from the hepatic artery. Rare variations: celiaco-mesenteric trunk; two arterial trunks, hepato-splenic and hepato-gastric; separate aortic origin for all three "classic" branches of the celiac trunk; two hepatic arteries, one from the celiac trunk and the other from the aorta or superior mesenteric artery; celiac trunk that divides into several terminal branches; one or two suprarenal arteries originating from the celiac trunk.

Cadaver↗

PubMed1993

Perception of horizontal head and trunk rotation: modification of neck input following loss of vestibular function.

Chronic loss of vestibular function modifies the role of neck afferents in human perception of self-motion. We characterized this change by comparing the self-motion perception of patients with chronic vestibular loss (Ps) to that of normal subjects (Ns). Stimuli consisted of sinusoidal horizontal rotations (0.025-0.4 Hz) of the trunk relative to the head (neck stimulation) and/or of the head in space (vestibular stimulation). Perception of head rotation relative to the trunk, of trunk rotation in space, or of head rotation in space was assessed in terms of gain and phase (veridical perception, G = 1 and phi = 0 degree) as well as detection threshold using a pointing procedure. (1) Perception of head rotation relative to the trunk (neck proprioception). Ps' detection threshold of head-to-trunk rotation was normal (i.e. similar to that of Ns) across all frequencies tested. Also, with peak angular velocities above 5 degrees/s, the gain of their perception was approximately normal. When peak velocity was decreased below this value, however, either by lowering stimulus frequency with peak displacement kept constant (+/- 8 degrees) or by decreasing peak displacement at constant frequency (0.05 Hz), the gain increased above unity, unlike in Ns. In contrast, the phase remained normal (approximately 0 degree). (2) Perception of trunk rotation in space. Ps perceived their trunks as stationary during neck stimulation and all vestibular-neck combinations at medium to low frequencies. At 0.4 Hz, however, Ps consistently perceived the trunk rotation, conceivably due to somatosensory self-motion cues arising from high body acceleration. In contrast, Ns perceive a trunk-in-space rotation with the neck stimulation and most of the stimulus combinations across the whole frequency range tested. Ns perceived their trunks as stationary only during head rotation on the stationary trunk (presumed to reflect a mutual cancellation of neck and vestibular signals). (3) Perception of head rotation in space. In Ps, unlike Ns, this perception always resembled that of head rotation relative to the trunk. (4) When Ps were presented with a visual or somatosensory space reference (not motion cues), their perception of trunk and head rotation in space became approximately normal. (5) We suggest that there are basically two changes in the neck-induced self-motion perception associated with chronic vestibular loss. First, neck proprioception shows a non-linear gain that overemphasizes low stimulus velocities, for unknown reasons.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗

PubMed1991

Human perception of horizontal trunk and head rotation in space during vestibular and neck stimulation.

The vestibular signal of head motion in space must be complemented by a neck signal of the trunk-to-head excursion in order to provide the individual with information on trunk motion in space. This consideration led us to study psychophysically the role of vestibular-neck interaction for human self-motion perception. Subjects (Ss) were presented with passive horizontal rotations of their trunk and/or head (sinusoidal rotations, f = 0.025 - 0.4 Hz) in the dark for vestibular and neck stimulation, as well as for combinations of both. Ss' perception was evaluated in terms of gain (veridical perception of stimulus magnitude, G = 1), phase, and detection threshold. (1) Perception of trunk rotation in space. During vestibular stimulation (whole-body rotation) and neck stimulation (trunk rotation with the head kept stationary) the frequency-transfer characteristics underlying this perception were very similar. The gain fell short; it was only about 0.7 at 0.4 and 0.2 Hz stimulus frequency and was further attenuated with decreasing frequency. In contrast, the phase was close to that of actual trunk position. The gain attenuation was found to be a function of the peak angular velocity of the stimulus, a fact, which we related to a 'velocity threshold' of the order of 1 deg/s. During the various vestibular-neck combinations used, Ss' perception was again erroneous, reflecting essentially the sum of its two non-ideal constituents. However, there was one noticeable exception; during the combination 'head rotation on stationary trunk', Ss veridically perceived their trunk as stationary (compatible with the notion that the sum yielded 'zero'). (2) Perception of head rotation in space. During vestibular stimulation, Ss' estimates showed the same non-ideal gain-vs.-frequency characteristics as described above for the trunk. Neck stimulation induced an illusion as if the head had been rotated in space. This neck contribution was such that, when it was combined with its vestibular counterpart during head rotation on stationary trunk, the perception became almost veridical. On closer inspection, however, this neck contribution was found to reflect the sum of two components; one was the non-ideal neck signal contributing to the perception of 'trunk in space', the other was an almost ideal neck signal of head-on-trunk rotation. (3) The results could be described by a simple model. In this model, the erroneous vestibular signal 'head in space' is primarily used to create an internal representation of 'trunk in space'.(ABSTRACT TRUNCATED AT 400 WORDS)

Head↗

PubMed2002

Use of the trunk for reaching targets placed within and beyond the reach in adult hemiparesis.

Multijoint movements such as reaching are impaired after brain lesions involving sensorimotor areas and pathways. However, the mechanisms by which such lesions affect motor control are not fully understood. Direct effects of the lesion may be partly compensated by both the system's redundancy and its plasticity. Indeed stroke patients with limited arm movement can reach objects placed within the reach of the arm by using a compensatory strategy involving trunk recruitment. A similar strategy is observed in healthy individuals reaching for objects placed beyond the reach of the arm. Determining the control mechanism(s) governing this compensatory strategy in stroke patients was the goal of this study. Kinematics of reaching movements in hemiparetic and healthy participants to targets placed within and beyond the length of the arm were analysed. Targets were placed sagittally in front of the midline of the body. Two targets (targets 1 and 2) were within reaching distance defined as the length of the stretched arm from axilla to wrist crease. Two others were beyond arm's reach so that one required a forward trunk inclination (target 3) and the other required body raising to a semi-standing position (target 4). Healthy participants used minimal trunk displacement for reaches to targets 1 and 2. For reaches to targets 3 and 4, trunk displacement increased with target distance. Whenever the trunk was involved, there was a stereotyped sequential recruitment of the arm and trunk in that the trunk began moving simultaneously with or before the hand and stopped moving after the end of hand movement. This suggested that the control system predicts that the trunk movement will be needed to extend the reach and includes the trunk, in an anticipatory way, into the reach. In contrast, most hemiparetic participants recruited their trunk for reaches to all four targets, even those placed close to the body. Similar to healthy individuals, the sequence of hand and trunk recruitment was stereotyped, suggesting that temporal planning aspects of the motor program underlying movement coordination were relatively unaffected. In contrast to healthy participants, the contribution of the trunk movement to the endpoint displacement was substantially higher in the hemiparetic group and occurred earlier in the reach. It is suggested that the target distance at which the trunk is integrated into the movement to extend the reach of the arm is attained around the limit of arm extension and that this limit is reduced in hemiparetic individuals.

Adult↗

PubMed2003

Posture-dependent trunk extensor EMG activity during maximum isometrics exertions in normal male and female subjects.

Posture-dependent trunk function data are important for appropriate normalization of submaximal trunk exertions, and is also necessary to define a more precise and specific use for strength testing in the prevention and diagnosis of spinal disorders. The aim of the current study was to quantify maximal effort trunk muscle extensor activity and trunk isometric extension torque over a functional range of sagittal standing postures. Twenty healthy, young adult male and female subjects performed isometric extension tasks over a sagittal posture range of -20 degrees extension to +50 degrees flexion, in 10 degrees increments. Erector spinae muscle activity was recorded bilaterally at the level of L3 using surface EMG electrodes. Isometric trunk extension torque was measured using a trunk dynamometer. EMG and trunk torque differed significantly between genders, but there were no differences between male and female subjects when the data were normalized with respect to the upright posture. For the combined male and female population, upright posture normalized L3 EMG activity (EMGn) and trunk extension torque (Tn) increased 1.7-fold and 3.5-fold, respectively, over the 70 degrees range of sagittal postures examined. The ratio (Tn/EMGn) increased two-fold (0.83 to 1.67) from -20 degrees extension to +50 degrees flexion, indicating that the neuromuscular efficiency increases with flexion. Trunk extension torque normalized with respect to the upright posture was linearly and positively correlated (r = 0.59, P < 0.001) to similarly normalized L3 EMG activity. This relatively weak correlation suggests that trunk muscle synergism and/or intrinsic muscle length-tension relationships are also modulated by posture. This study provides data that can be used to estimate trunk extensor muscle function over a broad range of sagittal postures. Our findings indicate that appropriate postural normalization of trunk extensor EMG activity is necessary for studies where submaximal trunk exertions are performed over a range of upright postures.

Adult↗

PubMed1996

[Axial (neck and trunk) rigidity in Parkinson's disease, striatonigral degeneration and progressive supranuclear palsy].

Our previous study showed that the alternating knee tilt test in supine position is a useful method to assess the trunk rigidity. We investigated the progression of axial (neck and trunk) rigidity in Parkinson's disease (PD), striatonigral degeneration (SND), and progressive supranuclear palsy (PSP) by using this method. We assessed rigidity on a scale of 0 (absent) to 3 (severe) on five parts of the body: neck, trunk, wrist, elbow and knee in 57 patients with PD, 13 patients with SND and 18 patients with PSP. In PD patients, the degree of neck and trunk rigidity correlated well with the duration of disease and the staging scale. There was neck rigidity in 27% of PD patients with unilateral involvement of the limbs, but the trunk tonus was normal in them. There was rigidity in the neck and trunk of all PD patients with bilateral involvement of the limbs. When the limb rigidity was predominant on one side, the trunk rigidity was predominant on the opposite side. In SND patients, the degree of neck and trunk rigidity roughly correlated with the duration of disease and the staging scale. In SND patients with unilateral involvement of the limbs, tonus of the neck and trunk was normal. In SND patients with bilateral involvement of limbs, there was rigidity in both the neck and the trunk. In PSP patients, the degree of neck rigidity correlated well with the duration of disease and the staging scale, but the degree of rigidity in the trunk and limb remained relatively mild even at the advanced stage. Accordingly, in PSP patients there was a dissociation of the degree of neck rigidity from that of trunk and limb rigidity. In conclusion, the assessment of axial (neck and trunk) rigidity may be useful for the clinical diagnosis of parkinsonism and the staging scale scoring.

Adult↗

PubMed1990

Topographical anatomy of the bronchomediastinal lymph vessels: their relationships and formation of the collecting trunks.

This article aims to clarify the topographical relationships of the bronchomediastinal collecting lymph vessels to other structures, in particular the great vessels, the trachea, the esophagus and the mediastinal pleura. Minute dissection was performed on eight cadavers with special reference to the converging collecting lymph vessels which form the bronchomediastinal trunks. On the right side, the trunks were consistently observed on both the right brachiocephalic vein and the subserous surface of the mediastinal pleura (anterior and posterior mediastinal trunks). The pathway from the right recurrent chain nodes ran laterally behind the carotid sheath and led either into the deep cervical nodes situated on the scalenus anterior or directly into the right venous angle. On the left side, the trunks showed varying courses. The nodes from which the trunks arose were constant, and classifiable into three groups: the uppermost paratracheal nodes near the recurrent chain nodes, the anterior mediastinal nodes (the left phrenic nodes) surrounding the phrenic nerve in front of and inferior to the aortic arch (the origin of the superior mediastinal trunk), and the left tracheobronchial nodes (the origin of the inferior mediastinal trunk). The large transverse superficial communicating vessel between the right and left sides was usually found in front of the trachea above the aortic arch; it was often connected to the nodes of the brachiocephalic angle. Deep communications were also found in front of the carina and behind the trachea. These findings allow the collecting vessels from the thoracic viscera to be divided into two pathways on each side: the anterior and posterior mediastinal trunks on the right side, and the superior and inferior mediastinal trunks on the left side. In addition to the four trunks, the superficial communicating vessel between the right and left sides is also drained from the superior mediastinum. The internal mammary lymph chain, which often emptied directly into the venous angle or into the deep cervical nodes, occasionally joined with the right anterior mediastinal trunk or the left superior mediastinal trunk.

Adult↗