ABSTRACT
Because of a limited capacity of information processing in the brain, the efficient processing of visual information requires selecting only a very small fraction of visual inputs at any given moment in time. Attention is the main mechanism that controls this selection process, namely selective attention. Selective attention is the mechanism by which the subset of incoming information is preferentially processed from the complex external environment. Research on selective attention has two key issues. One is what targets (inputs) are selected by attention. There are three different types of selective attention according to its selected target: space-based, feature-based, and object-based attention. Another issue is how selective attention is generated. There are two different types of selective attention according to its generating source: top-down and bottom-up attention. In this review, these two issues are introduced to systematically discuss the neural mechanism of visual selective attention.
Subject(s)
Humans , Attention , Brain , Physiology , Cognition , Visual PerceptionABSTRACT
Objective To explore the biomechanical mechanisms of correlation between lumbar disc degeneration and sacroiliac joint disorder though investigating the biomechanical characteristics of lumbar disc degeneration with sacroiliac joint disorders.Methods One normal healthy volunteer and two patients with lumbar disc herniation and sacroiliac joint disorders (one was with sacrum disorders and the other was with ilium disorders) were selected.Their CT data were collected to establish three corresponding lumbar-pelvis finite-element models,and their gait data were also simultaneously collected to drive the AnyBody musculoskeletal model.The muscle force around the lumbar and pelvis as well as the hip joint force were acquired as loading condition for finite element analysis.The stress changes in L4 and L5 intervertebral discs and sacroiliac joints of the patients and normal volunteer were compared.Results There was no significant difference in the stress of the two sides of L4,L5 disc and two sacroiliac joints in normal model,with a bimodal stress curve.However,in the models of sacrum disorders and ilium disorders,the bimodal stress curve peaks changed,even disappeared.The peak stress differences in left and right side of L4 disc were 0.55 MPa and 0.80 MPa,respectively,the peak stress differences in left and right side of L5 disc were 4.05 MPa and 2.08 MPa,respectively,and the peak stress differences in left and right side of sacroiliac joints were 0.96 MPa and 3.32 MPa,respectively.Conclusions The lumbar disc degeneration with sacroiliac joint disorder leads to the tilt of the body loading line,and sacroiliac joint disorder can aggravate the imbalances of stress on the body sides.The impact of sacroiliac joint dysfunction cannot be ignored in the treatment of lumbar disc herniation.
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Objective To explore the biomechanical mechanisms of correlation between lumbar disc degeneration and sacroiliac joint disorder though investigating the biomechanical characteristics of lumbar disc degeneration with sacroiliac joint disorders.Methods One normal healthy volunteer and two patients with lumbar disc herniation and sacroiliac joint disorders (one was with sacrum disorders and the other was with ilium disorders) were selected.Their CT data were collected to establish three corresponding lumbar-pelvis finite-element models,and their gait data were also simultaneously collected to drive the AnyBody musculoskeletal model.The muscle force around the lumbar and pelvis as well as the hip joint force were acquired as loading condition for finite element analysis.The stress changes in L4 and L5 intervertebral discs and sacroiliac joints of the patients and normal volunteer were compared.Results There was no significant difference in the stress of the two sides of L4,L5 disc and two sacroiliac joints in normal model,with a bimodal stress curve.However,in the models of sacrum disorders and ilium disorders,the bimodal stress curve peaks changed,even disappeared.The peak stress differences in left and right side of L4 disc were 0.55 MPa and 0.80 MPa,respectively,the peak stress differences in left and right side of L5 disc were 4.05 MPa and 2.08 MPa,respectively,and the peak stress differences in left and right side of sacroiliac joints were 0.96 MPa and 3.32 MPa,respectively.Conclusions The lumbar disc degeneration with sacroiliac joint disorder leads to the tilt of the body loading line,and sacroiliac joint disorder can aggravate the imbalances of stress on the body sides.The impact of sacroiliac joint dysfunction cannot be ignored in the treatment of lumbar disc herniation.
ABSTRACT
Objective To explore the biomechanical mechanisms of correlation between lumbar disc degeneration and sacroiliac joint disorder though investigating the biomechanical characteristics of lumbar disc degeneration with sacroiliac joint disorders. Methods One normal healthy volunteer and two patients with lumbar disc herniation and sacroiliac joint disorders (one was with sacrum disorders and the other was ilium disorders) were selected. Their CT data were collected to establish three corresponding lumbar-pelvis finite-element models, and their gait data were also simultaneously collected to drive the AnyBody musculoskeletal model. The muscle force around the lumbar and pelvis as well as the hip joint force were acquired as loading condition for finite element analysis. The stress changes in L4 and L5 intervertebral discs and sacroiliac joints of the patients and normal volunteer were compared. Results There was no significant difference in the stress of the two sides of L4, L5 disc and two sacroiliac joints in normal model, with a bimodal stress curve. However, in the models of sacrum disorders and ilium disorders, the bimodal stress curve peaks changed, even disappeared. The peak stress differences in left and right side of L4 disc were 0.55 MPa and 0.80 MPa, respectively, the peak stress differences in left and right side of L5 disc were 4.05 MPa and 2.08 MPa, respectively, and the peak stress differences in left and right side of sacroiliac joints were 0.96 MPa and 3.32 MPa, respectively. Conclusions The lumbar disc degeneration with sacroiliac joint disorder leads to the tilt of the body loading line, and sacroiliac joint disorder can aggravate the imbalances of stress on the body sides. The impact of sacroiliac joint dysfunction cannot be ignored in the treatment of lumbar disc herniation.
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Objective To analyze mechanical properties of cervical spine manipulation with fine adjustment, so as to provide mechanical data for popularization of such manipulation in clinic. Methods The founder, a skilled practitioner and a beginner of fine-adjusting manipulation operated the spinal fine-adjusting manipulation on two cervical vertebral segments of healthy subjects, respectively. The force data of thumbs were collected by FingerTPS Wireless System to analyze force differences between two thumbs while the force of right thumb was in its peak value, as well as regular pattern of the thumb force in relation with time. Results Significant differences were found between the maximum force of two thumbs in each subject (P＜0.001). The process of force application (from trough to peak, T1) was longer than that of force reduction (from peak to trough, T2) when all the subjects operated spinal fine-adjusting manipulation, showing significant differences (P＜0.001). Conclusions There exists the main and auxiliary hand during cervical spine manipulation with fine adjustment, which is actually a process of slow force application and rapid force reduction.
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Objective To study the mechanisms of vertebrae semi-dislocation of Tuina manipulation for treating patients with lumbar intervertebral disc protrusion (LIDP) by observing the three-dimensional (3D) displacement of lumbar before and after Tuina manipulation. Methods Ten LIDP patients were selected and evenly divided into two groups: Group 1 as tendon-smoothing manipulation group (relaxing group), Group 2 as tendon-smoothing plus adjusting manipulation group (adjusting group). Besides, Group 3 as control group was established by 5 healthy volunteers treated with tendon-smoothing manipulation. Before and after manipulation intervention, all subjects were scanned from L1 to L5 segment by using Philips 64 spiral CT under equal conditions for accessing the volume data. ITK reconstruction software was used to reconstruct each lumbar skeleton for finite element analysis. The 3D displacements and angular displacements among three groups were compared. Results 3D displacement from L1 to L5 segment all changed in three groups. For adjusting group, the angular displacements at X-axis in L3 segment was (1.77±0.46)°, and that in L4 segment at X-axis and Y-axis was (1.78±0.53)° and (1.89±0.75)°, respectively, which was significantly larger than relaxing group and control group (P<0.05); the angular displacements at X-axis from L1 to L5 segment were (1.50±0.47)°, (1.55±0.57)°, (1.77±0.46)°, (1.78±0.53)°, (1.61±0.39)°, respectively, which were significantly larger than control group (P<0.05); displacement at Y-axis in L3 segment was (2.87±0.74) mm, and that at X-axis in L4 segment was (1.68±0.64) mm, which were significantly larger than relaxing group and control group (P<0.05); displacement at X-axis in L1, L4 and L5 segment was (1.28±0.21),（1.68±0.64）, (1.30±0.51） mm, and that at Y-axis in L1 to L3 segment was (1.92±0.42), (2.25±0.61), (2.87±0.74) mm, which was significantly larger than control group (P<0.05). The angular displacements and displacements of L1 to L5 segment in relaxing group were larger than those in control group, but without any significant differences. Conclusions Compared with relaxing manipulation, adjusting manipulation played a more obvious adjusting role in instability and degenerative lumbar vertebra, especially for angular displacements in X-axis, and displacements in X-axis and Y-axis. Namely, the mechanisms of vertebrae semi-dislocation of adjusting manipulation were to make horizontal and rotational displacements at lumbar vertebra other than upper and lower displacement. The effect of relaxing manipulation was not so obvious on lumbar structure of LIDP patients.
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Objective To explore the relationship between hemolymph phenol oxidase and the melanization of Plasmodium yoelii oocysts in Anopheles dirus. Methods An Anopheles dirus-Plasmodium yoelii system was used Anopheles dirus were divided into 3 groups, that is, non-blood-fedding (N), normal-blood-fedding (B) and infected-blood-fedding (I). The activities of MPO and o-DPO in hemolymph from 3 groups were determined with native polyacrylamide gel electrophoresis (PAGE) and density scanning at 5, 7, 11 and 15 d after blood feeding. Results Both MPO and o-DPO activity were significantly higher in group I than group N and B (P<0.05). But with the melanization of Plasmodium yoelii oocysts, both MPO and o-DPO activity in group I were decreased in comparison with group N, especially on the 15 th day after infected-blood feeding. MPO and o-DPO activity in group B were significantly stronger than those of group N. Conclusion Blood feeding and infection of Plasmodium yoelii both can activate the cascade. The heamolymph phenol oxidase may play an important role in the melanization of Plasmodium yoelii oocysts in Anopheles dirus.
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Objective To explore the relationship between hemolymph phenol oxidase and the melanization of Plasmodium yoelii oocysts in Anopheles dirus. Methods An Anopheles dirus-Plasmodium yoelii system was used Anopheles dirus were divided into 3 groups, that is, non-blood-fedding (N), normal-blood-fedding (B) and infected-blood-fedding (I). The activities of MPO and o-DPO in hemolymph from 3 groups were determined with native polyacrylamide gel electrophoresis (PAGE) and density scanning at 5, 7, 11 and 15 d after blood feeding. Results Both MPO and o-DPO activity were significantly higher in group I than group N and B (P<0.05). But with the melanization of Plasmodium yoelii oocysts, both MPO and o-DPO activity in group I were decreased in comparison with group N, especially on the 15 th day after infected-blood feeding. MPO and o-DPO activity in group B were significantly stronger than those of group N. Conclusion Blood feeding and infection of Plasmodium yoelii both can activate the cascade. The heamolymph phenol oxidase may play an important role in the melanization of Plasmodium yoelii oocysts in Anopheles dirus.