scholarly journals Locomotor Hand Postures, Carpal Kinematics During Wrist Extension, and Associated Morphology in Anthropoid Primates

2016 ◽  
Vol 300 (2) ◽  
pp. 382-401 ◽  
Author(s):  
Caley M. Orr
Keyword(s):  
Wrist Extension ◽  
Carpal Kinematics ◽  
Anthropoid Primates

scholarly journals Carpal Kinematics following Sequential Scapholunate Ligament Sectioning

2019 ◽  
Vol 08 (02) ◽  
pp. 124-131 ◽  
Author(s):  
Clare Padmore ◽  
Helen Stoesser ◽  
G. Daniel Langohr ◽  
James Johnson ◽  
Nina Suh
Keyword(s):  
Treatment Strategies ◽  
Biomechanical Study ◽  
Wrist Flexion ◽  
Scapholunate Ligament ◽  
Wrist Extension ◽  
Intact State ◽  
Carpal Kinematics ◽  
Significant Change ◽  
Flexion And Extension

Background The scapholunate ligament (SLL) is the most commonly injured intercarpal ligament of the wrist. It is the primary stabilizer of the scapholunate (SL) joint, but the scaphotrapeziotrapezoid (STT) and radioscaphocapitate (RSC) ligaments may also contribute to SL stability. The contributions of SL joint stabilizers have been reported previously; however, this study aims to examine their contributions to SL stability using a different methodology than previous studies. Purpose The purpose of this in vitro biomechanical study was to quantify changes in SL kinematics during wrist flexion and extension following a previously untested sequential sectioning series of the SL ligament and secondary stabilizers. Methods Eight cadaveric upper extremities underwent active wrist flexion and extension in a custom motion wrist simulator. SL kinematics were captured with respect to the distal radius. A five-stage sequential sectioning protocol was performed, with data analyzed from 45-degree wrist flexion to 45-degree wrist extension. Results Wrist flexion and extension caused the lunate to adopt a more extended posture following sectioning of the SLL and secondary stabilizers compared with the intact state (p < 0.009). The isolated disruption to the dorsal portion of the SLL did not result in significant change in lunate kinematics compared with the intact state (p > 0.05). Scaphoid kinematics were altered in wrist flexion following sequential sectioning (p = 0.013). Additionally, disruption of the primary and secondary stabilizers caused significant change to SL motion in both wrist flexion and wrist extension (p < 0.03). Conclusions The SLL is the primary stabilizer of the SL articulation, with the STT and RSC ligaments playing secondary stabilization roles. Clinical Relevance Understanding the role primary and secondary SL joint stabilizers may assist in the development of more effective treatment strategies and patient outcomes following SLL injuries.

scholarly journals Inhibitory interneurons of the human prefrontal cortex display conserved evolution of the phenotype and related genes

2009 ◽  
Vol 277 (1684) ◽  
pp. 1011-1020 ◽  
Author(s):  
Chet C. Sherwood ◽  
Mary Ann Raghanti ◽  
Cheryl D. Stimpson ◽  
Muhammad A. Spocter ◽  
Monica Uddin ◽  
...  
Keyword(s):  
Prefrontal Cortex ◽  
Calcium Binding ◽  
Amino Acid Level ◽  
Primate Evolution ◽  
Inhibitory Interneurons ◽  
Cognitive Domains ◽  
Inhibitory Circuitry ◽  
Show Evidence ◽  
Anthropoid Primates ◽  
And Migration

Inhibitory interneurons participate in local processing circuits, playing a central role in executive cognitive functions of the prefrontal cortex. Although humans differ from other primates in a number of cognitive domains, it is not currently known whether the interneuron system has changed in the course of primate evolution leading to our species. In this study, we examined the distribution of different interneuron subtypes in the prefrontal cortex of anthropoid primates as revealed by immunohistochemistry against the calcium-binding proteins calbindin, calretinin and parvalbumin. In addition, we tested whether genes involved in the specification, differentiation and migration of interneurons show evidence of positive selection in the evolution of humans. Our findings demonstrate that cellular distributions of interneuron subtypes in human prefrontal cortex are similar to other anthropoid primates and can be explained by general scaling rules. Furthermore, genes underlying interneuron development are highly conserved at the amino acid level in primate evolution. Taken together, these results suggest that the prefrontal cortex in humans retains a similar inhibitory circuitry to that in closely related primates, even though it performs functional operations that are unique to our species. Thus, it is likely that other significant modifications to the connectivity and molecular biology of the prefrontal cortex were overlaid on this conserved interneuron architecture in the course of human evolution.

Effect of Computer Keyboard Slope on Upper Limb Postures at Sitting and Standing ComputerWorkstations : A Pilot Study

2021 ◽  
Vol 65 (1) ◽  
pp. 1235-1239
Author(s):  
Howraa Nash ◽  
Gourav Kumar Nayak ◽  
Jashwant Thota ◽  
Mohammed Alsowaidi ◽  
Hashem Alsowaidi ◽  
...  
Keyword(s):  
Upper Limb ◽  
User Preference ◽  
Positive Slope ◽  
Standing Posture ◽  
Support Design ◽  
Wrist Extension ◽  
Sitting Posture ◽  
Working Postures ◽  
Computer Workstation ◽  
Computer Keyboard

A user’s posture at a computer workstation, especially wrist posture, is determined by the keyboard angle. Most commercially available computer keyboards have a built-in positive slope that requires the user to extend their wrist approximately 20° when typing. The purpose of this study is to find the negative keyboard angles that minimize wrist extension for both sitting and standing workstations. In this study, we compared upper limb working postures, including those of the wrist, elbow and shoulder, at 5 different keyboard angles between −16° and +6° in sitting and standing postures. Based on our results, we can conclude that the optimal range of keyboard slope is from −4° to −12° in sitting posture and −8° to −12° in the standing posture in terms of minimum wrist extension, typing performance, and user preference. We also propose a universal keyboard support design as an attachment to currently available keyboards.

Wrist Action Affects Precision Grip Force

1997 ◽  
Vol 78 (1) ◽  
pp. 271-280 ◽  
Author(s):  
Mary M. Werremeyer ◽  
Kelly J. Cole
Keyword(s):  
Grip Force ◽  
Precision Grip ◽  
Load Force ◽  
Myoelectric Activity ◽  
Resistive Load ◽  
Wrist Flexion ◽  
Wrist Extension ◽  
Hand Muscles ◽  
Force Pulse ◽  
Grasp Stability

Werremeyer, Mary M. and Kelly J. Cole. Wrist action affects precision grip force. J. Neurophysiol. 78: 271–280, 1997. When moving objects with a precision grip, fingertip forces normal to the object surface (grip force) change in parallel with forces tangential to the object (load force). We investigated whether voluntary wrist actions can affect grip force independent of load force, because the extrinsic finger muscles cross the wrist. Grip force increased with wrist angular speed during wrist motion in the horizontal plane, and was much larger than the increased tangential load at the fingertips or the reaction forces from linear acceleration of the test object. During wrist flexion the index finger muscles in the hand and forearm increased myoelectric activity; during wrist extension this myoelectric activity increased little, or decreased for some subjects. The grip force maxima coincided with wrist acceleration maxima, and grip force remained elevated when subjects held the wrist in extreme flexion or extension. Likewise, during isometric wrist actions the grip force increased even though the fingertip loads remained constant. A grip force “pulse” developed that increased with wrist force rate, followed by a static grip force while the wrist force was sustained. Subjects could not suppress the grip force pulse when provided visual feedback of their grip force. We conclude that the extrinsic hand muscles can be recruited to assist the intended wrist action, yielding higher grip-load ratios than those employed with the wrist at rest. This added drive to hand muscles overcame any loss in muscle force while the extrinsic finger flexors shortened during wrist flexion motion. During wrist extension motion grip force increases apparently occurred from eccentric contraction of the extrinsic finger flexors. The coactivation of hand closing muscles with other wrist muscles also may result in part from a general motor facilitation, because grip force increased during isometric knee extension. However, these increases were related weakly to the knee force. The observed muscle coactivation, from all sources, may contribute to grasp stability. For example, when transporting grasped objects, upper limb accelerations simultaneously produce inertial torques at the wrist that must be resisted, and inertial loads at the fingertips from the object that must be offset by increased grip force. The muscle coactivation described here would cause similarly timed pulses in the wrist force and grip force. However, grip-load coupling from this mechanism would not contribute much to grasp stability when small wrist forces are required, such as for slow movements or when the object's total resistive load is small.

Resultant Carpal Kinematics With Respect to Muscle Force Application

2007 ◽  
Author(s):  
Rita M. Patterson ◽  
William L. Buford ◽  
Clark L. Andersen ◽  
Steven F. Viegas
Keyword(s):  
Muscle Force ◽  
Carpal Bones ◽  
Force Application ◽  
Carpal Kinematics

Purpose: The purpose of this study was to investigate the kinematics of seven carpal bones during a simulated active (tendon-driven) and passive (externally-assisted) motion of the wrist.

scholarly journals A search for evidence of a remote human past in Africa

1984 ◽  
Vol 3 (2) ◽  
pp. 93-100
Author(s):  
A. Spies
Keyword(s):  
Half Life ◽  
Foramen Magnum ◽  
Anthropoid Primates

The changes that primate skulls have undergone are of utmost importance regarding teeth, volume of braincase and position of the foramen magnum. Should the foramen magnum face directly downward, the head would have been carried over the spine, proving erectness and bipedalism. The knowledge of the half-life of certain radio-active isotopes is the key for calculating the age of a fossil. Changes of any part of an animal becoming fossilized are very slight. Chances of finding it are so much more slight. In Oligocene times the anthropoid primates were successful tree-dwellers. The Fayum was heavily wooded, a fine place for proto-monkeys to live - and evolve. Evolve they did, for the Fayum contains a uniquely rich deposit of primate fossils.

Sign in / Sign up

Export Citation Format

Share Document