We examined the validity and reliability of a short robotic test of upper limb proprioception, the Arm Movement Detection (AMD) test, which yields a ratio-scaled, objective outcome measure to be used ...for evaluating the impact of sensory deficits on impairments of motor control, motor adaptation and functional recovery in stroke survivors.
Subjects grasped the handle of a horizontal planar robot, with their arm and the robot hidden from view. The robot applied graded force perturbations, which produced small displacements of the handle. The AMD test required subjects to respond verbally to queries regarding whether or not they detected arm motions. Each participant completed ten, 60s trials; in five of the trials, force perturbations were increased in small increments until the participant detected motion while in the others, perturbations were decreased until the participant could no longer detect motion. The mean and standard deviation of the 10 movement detection thresholds were used to compute a Proprioceptive Acuity Score (PAS). Based on the sensitivity and consistency of the estimated thresholds, the PAS quantifies the likelihood that proprioception is intact. Lower PAS scores correspond to higher proprioceptive acuity. Thirty-nine participants completed the AMD test, consisting of 25 neurologically intact control participants (NIC), seven survivors of stroke with intact proprioception in the more affected limb (HSS+P), and seven survivors of stroke with impaired or absent proprioception in the more affected limb (HSS-P).
Significant group differences were found, with the NIC and HSS+P groups having lower (i.e., better) PAS scores than the HSS-P group. A subset of the participants completed the AMD test multiple times and the AMD test was found to be reliable across repetitions.
The AMD test required less than 15 min to complete and provided an objective, ratio-scaled measure of proprioceptive acuity in the upper limb. In the future, this test could be utilized to evaluate the contributions of sensory deficits to motor recovery following stroke.
Motor sequence learning is abnormal in presymptomatic Huntington's disease (p‐HD). The neural substrates underlying this early manifestation of HD are poorly understood. To study the mechanism of ...this cognitive abnormality in p‐HD, we used positron emission tomography to record brain activity during motor sequence learning in these subjects. Eleven p‐HD subjects (age, 45.8 ± 11.0 years; CAG repeat length, 41.6 ± 1.8) and 11 age‐matched control subjects (age, 45.3 ± 13.4 years) underwent H215O positron emission tomography while performing a set of kinematically controlled motor sequence learning and execution tasks. Differences in regional brain activation responses between groups and conditions were assessed. In addition, we identified discrete regions in which learning‐related activity correlated with performance. We found that sequence learning was impaired in p‐HD subjects despite normal motor performance. In p‐HD, activation responses during learning were abnormally increased in the left mediodorsal thalamus and orbitofrontal cortex (OFC; BA 11/47). Impaired learning performance in these subjects was associated with increased activation responses in the precuneus (BA 18/31). These data suggest that enhanced activation of thalamocortical pathways during motor learning can compensate for caudate degeneration in p‐HD. Nonetheless, this mechanism may not be sufficient to sustain a normal level of task performance, even during the presymptomatic stage of the disease. Ann Neurol 2006
Clinical improvement with levodopa therapy for PD is associated with specific regional changes in cerebral glucose metabolism. However, it is unknown how these effects of treatment in the resting ...state relate to alterations in brain function that occur during movement. In this study, the authors used PET to assess the effects of levodopa on motor activation responses and determined how these changes related to on-line recordings of movement speed and accuracy.
Seven right-handed PD patients were scanned with H(2)15O/PET while performing a predictable paced sequence of reaching movements and while observing the same screen displays and tones. PET studies were performed during "on" and "off" states with an individually titrated constant rate levodopa infusion; movements were kinematically controlled across treatment conditions.
Levodopa improved "off" state UPDRS motor ratings (34%; p < 0.006) and movement time (18%; p = 0.001). Spatial errors worsened during levodopa infusion (24%; p = 0.02). Concurrent regional cerebral blood flow (rCBF) recordings revealed significant enhancement of motor activation responses in the posterior putamen bilaterally (p < 0.001), left ventral thalamus (p < 0.002), and pons (p < 0.005). Movement time improvement with treatment correlated with rCBF increases in the left globus pallidus and left ventral thalamus (p < 0.01). By contrast, the increase in spatial errors correlated with rCBF increases in the cerebellar vermis (p < 0.01).
These results suggest that levodopa infusion may improve aspects of motor performance while worsening others. Different components of the motor cortico-striato-pallido-thalamo-cortical loop and related pathways may underlie motor improvement and adverse motoric effects of levodopa therapy for PD.
The first observation of the decay ηc(2S)→pp¯ is reported using proton–proton collision data corresponding to an integrated luminosity of 3.0 fb−1 recorded by the LHCb experiment at centre-of-mass ...energies of 7 and 8 TeV. The ηc(2S) resonance is produced in the decay B+→cc¯K+. The product of branching fractions normalised to that for the J/ψ intermediate state, Rηc(2S), is measured to beRηc(2S)≡B(B+→ηc(2S)K+)×B(ηc(2S)→pp¯)B(B+→J/ψK+)×B(J/ψ→pp¯)=(1.58±0.33±0.09)×10−2, where the first uncertainty is statistical and the second systematic. No signals for the decays B+→X(3872)(→pp¯)K+ and B+→ψ(3770)(→pp¯)K+ are seen, and the 95% confidence level upper limits on their relative branching ratios are found to be RX(3872)<0.25×10−2 and Rψ(3770)<0.10. In addition, the mass differences between the ηc(1S) and the J/ψ states, between the ηc(2S) and the ψ(2S) states, and the natural width of the ηc(1S) are measured asMJ/ψ−Mηc(1S)=110.2±0.5±0.9 MeV,Mψ(2S)−Mηc(2S)=52.5±1.7±0.6 MeV,Γηc(1S)=34.0±1.9±1.3 MeV.
A
bstract
The first observation of
Z
boson production in proton-lead collisions at a centre-of-mass energy per proton-nucleon pair of
s
N
N
= 5 TeV is presented. The data sample corresponds to an ...integrated luminosity of 1
.
6 nb
−1
collected with the LHCb detector. The
Z
candidates are reconstructed from pairs of oppositely charged muons with pseudorapidities between 2.0 and 4.5 and transverse momenta above 20 GeV
/
c. The invariant dimuon mass is restricted to the range 60 − 120 GeV
/
c. The
Z
production cross-section is measured to be
σ
Z
→
μ
+
μ
−
fwd
=
13.5
−
4.0
+
5.4
stat
.
±
1.2
syst
.
nb
in the direction of the proton beam and
σ
Z
→
μ
+
μ
−
bwd
=
10.7
−
5.1
+
8.4
stat
.
±
1.0
syst
.
nb
in the direction of the lead beam, where the first uncertainty is statistical and the second systematic.
The B0, B0s, B+ and Λ0b hadron production asymmetries are measured using a data sample corresponding to an integrated luminosity of 3.0 fb−1, collected by the LHCb experiment in proton-proton ...collisions at centre-of-mass energies of 7 and 8 TeV. The measurements are performed as a function of transverse momentum and rapidity of the b hadrons within the LHCb detector acceptance. The overall production asymmetries, integrated over transverse momentum and rapidity, are also determined.
The production cross-section of J/ψ pairs is measured using a data sample of pp collisions collected by the LHCb experiment at a centre-of-mass energy of s√=13TeV, corresponding to an integrated ...luminosity of 279±11pb−1. The measurement is performed for J/ψ mesons with a transverse momentum of less than 10GeV/c in the rapidity range 2.0<y<4.5. The production cross-section is measured to be 13.5±0.9±0.8nb. The first uncertainty is statistical, and the second is systematic. The differential cross-sections as functions of several kinematic variables of the J/ψ pair are measured and compared to theoretical predictions.
A
bstract
The ratio of branching fractions and the difference in
CP
asymmetries of the decays
B
+
→
J/ψπ
+
and
B
+
→
J/ψK
+
are measured using a data sample of
pp
collisions collected by the LHCb ...experiment, corresponding to an integrated luminosity of 3 fb
−1
at centre-of-mass energies of 7 and 8 TeV. The results are
ℬ
B
+
→
J
/
ψ
π
+
ℬ
B
+
→
J
/
ψ
K
+
=
3.83
±
0.03
±
0.03
×
10
−
2
,
A
C
P
B
+
→
J
/
ψ
π
+
−
A
C
P
B
+
→
J
/
ψ
K
+
=
1.82
±
0.86
±
0.14
×
10
−
2
,
where the first uncertainties are statistical and the second are systematic. Combining this result with a recent LHCb measurement of
A
C
P
B
+
→
J
/
ψ
K
+
provides the most precise estimate to date of
CP
violation in the decay
B
+
→
J/ψπ
+
,
A
C
P
B
+
→
J
/
ψ
π
+
=
1.91
±
0.89
±
0.16
×
1
0
−
2
.
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