Episodic memory retrieval is thought to rely on the replay of past experiences, yet it remains unknown how human single-unit activity is temporally organized during episodic memory encoding and ...retrieval. We found that ripple oscillations in the human cortex reflect underlying bursts of single-unit spiking activity that are organized into memory-specific sequences. Spiking sequences occurred repeatedly during memory formation and were replayed during successful memory retrieval, and this replay was associated with ripples in the medial temporal lobe. Together, these data demonstrate that human episodic memory is encoded by specific sequences of neural activity and that memory recall involves reinstating this temporal order of activity.
A
bstract
We present a calculation of the hadronic vacuum polarization contribution to the muon anomalous magnetic moment,
a
μ
hvp
, in lattice QCD employing dynamical up and down quarks. We focus on ...controlling the infrared regime of the vacuum polarization function. To this end we employ several complementary approaches, including Padé fits, time moments and the time-momentum representation. We correct our results for finite-volume effects by combining the Gounaris-Sakurai parameterization of the timelike pion form factor with the Lüscher formalism. On a subset of our ensembles we have derived an upper bound on the magnitude of quark-disconnected diagrams and found that they decrease the estimate for
a
μ
hvp
by at most 2%. Our final result is
a
μ
h
v
p
=
654
±
32
−
23
+
21
·10
−10
, where the first error is statistical, and the second denotes the combined systematic uncertainty. Based on our findings we discuss the prospects for determining
a
μ
hvp
with sub-percent precision.
Sequences of spiking activity have been heavily implicated as potential substrates of memory formation and retrieval across many species. A parallel line of recent evidence also asserts that ...sequential activity may arise from and be constrained by pre-existing network structure. Here we reconcile these two lines of research in the human brain by measuring single unit spiking sequences in the temporal lobe cortex as participants perform an episodic memory task. We find the presence of an average backbone spiking sequence identified during pre-task rest that is stable over time and different cognitive states. We further demonstrate that these backbone sequences are composed of both rigid and flexible sequence elements, and that flexible elements within these sequences serve to promote memory specificity when forming and retrieving new memories. These results support the hypothesis that pre-existing network dynamics serve as a scaffold for ongoing neural activity in the human cortex.
We present results for the isovector electromagnetic form factors of the nucleon computed on the coordinated lattice simulations ensembles with Nf=2+1 flavors of O(a)-improved Wilson fermions and an ...O(a)-improved vector current. The analysis ncludes ensembles with four lattice spacings and pion masses ranging from 130 up o 350 MeV and mainly targets the low-Q2 region. In order to remove any bias rom nsuppressed excited-state contributions, we investigate several source-sink eparations between 1.0 and 1.5 fm and apply the summation method as well as xplicit two-state fits. The chiral interpolation is performed by applying covariant hiral perturbation theory including vector mesons directly to our form factor data, hus avoiding an auxiliary parametrization of the Q2 dependence. At the physical oint, we obtain μ=4.71(11)stat(13)sys for the nucleon isovector magnetic moment, in good agreement with the experimental value and ⟨r2M⟩=0.661(30)stat(11)sys fm2 for the corresponding square radius, again in good agreement with the alue inferred from the ep-scattering determination Bernauer et al., Phys. Rev. ett. 105, 242001 (2010) of the proton radius. Our estimate for the isovector electric charge radius, ⟨r2E⟩=0.800(25)stat(22)sys fm2, however, is in slight tension with the larger value inferred from the aforementioned ep-scattering data, while being in agreement with the value derived from the 2018 CODATA average for the proton charge radius.
We present results for the strange contribution to the electromagnetic form factors of the nucleon computed on the coordinated lattice simulation ensembles with Nf=2+1 flavors of O(a)-improved Wilson ...fermions and an O(a)-improved vector current. Several source-sink separations are investigated in order to estimate the excited-state contamination. We calculate the form factors on six ensembles with lattice spacings in the range of a=0.049–0.086 fm and pion masses in the range of mπ=200–360 MeV, which allows for a controlled chiral and continuum extrapolation. In the computation of the quark-disconnected contributions, we employ hierarchical probing as a variance-reduction technique.
Mitofusins reside on the outer mitochondrial membrane and regulate mitochondrial fusion, a physiological process that impacts diverse cellular processes. Mitofusins are activated by conformational ...changes and subsequently oligomerize to enable mitochondrial fusion. Here, we identify small molecules that directly increase or inhibit mitofusins activity by modulating mitofusin conformations and oligomerization. We use these small molecules to better understand the role of mitofusins activity in mitochondrial fusion, function, and signaling. We find that mitofusin activation increases, whereas mitofusin inhibition decreases mitochondrial fusion and functionality. Remarkably, mitofusin inhibition also induces minority mitochondrial outer membrane permeabilization followed by sub-lethal caspase-3/7 activation, which in turn induces DNA damage and upregulates DNA damage response genes. In this context, apoptotic death induced by a second mitochondria-derived activator of caspases (SMAC) mimetic is potentiated by mitofusin inhibition. These data provide mechanistic insights into the function and regulation of mitofusins as well as small molecules to pharmacologically target mitofusins.
Microstimulation can modulate the activity of individual neurons to affect behavior, but the effects of stimulation on neuronal spiking are complex and remain poorly understood. This is especially ...challenging in the human brain where the response properties of individual neurons are sparse and heterogeneous. Here we use microelectrode arrays in the human anterior temporal lobe in 6 participants (3 female) to examine the spiking responses of individual neurons to microstimulation delivered through multiple distinct stimulation sites. We demonstrate that individual neurons can be driven with excitation or inhibition using different stimulation sites, which suggests an approach for providing direct control of spiking activity at the single-neuron level. Spiking responses are inhibitory in neurons that are close to the site of stimulation, while excitatory responses are more spatially distributed. Together, our data demonstrate that spiking responses of individual neurons can be reliably identified and manipulated in the human cortex.
One of the major limitations in our ability to interface directly with the human brain is that the effects of stimulation on the activity of individual neurons remain poorly understood. This study examines the spiking responses of neurons in the human temporal cortex in response to pulses of microstimulation. This study finds that individual neurons can either be excited or inhibited depending on the site of stimulation. These data suggest an approach for modulating the spiking activity of individual neurons in the human brain.
FLAG Review 2021 Aoki, Y.; Blum, T.; Colangelo, G. ...
The European physical journal. C, Particles and fields,
10/2022, Letnik:
82, Številka:
10
Journal Article
Recenzirano
Odprti dostop
We review lattice results related to pion, kaon,
D
-meson,
B
-meson, and nucleon physics with the aim of making them easily accessible to the nuclear and particle physics communities. More ...specifically, we report on the determination of the light-quark masses, the form factor
f
+
(
0
)
arising in the semileptonic
K
→
π
transition at zero momentum transfer, as well as the decay constant ratio
f
K
/
f
π
and its consequences for the CKM matrix elements
V
us
and
V
ud
. Furthermore, we describe the results obtained on the lattice for some of the low-energy constants of
S
U
(
2
)
L
×
S
U
(
2
)
R
and
S
U
(
3
)
L
×
S
U
(
3
)
R
Chiral Perturbation Theory. We review the determination of the
B
K
parameter of neutral kaon mixing as well as the additional four
B
parameters that arise in theories of physics beyond the Standard Model. For the heavy-quark sector, we provide results for
m
c
and
m
b
as well as those for the decay constants, form factors, and mixing parameters of charmed and bottom mesons and baryons. These are the heavy-quark quantities most relevant for the determination of CKM matrix elements and the global CKM unitarity-triangle fit. We review the status of lattice determinations of the strong coupling constant
α
s
. We consider nucleon matrix elements, and review the determinations of the axial, scalar and tensor bilinears, both isovector and flavor diagonal. Finally, in this review we have added a new section reviewing determinations of scale-setting quantities.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
FLAG Review 2019 Aoki, S.; Aoki, Y.; Bečirević, D. ...
The European physical journal. C, Particles and fields,
02/2020, Letnik:
80, Številka:
2
Journal Article
Recenzirano
Odprti dostop
We review lattice results related to pion, kaon,
D
-meson,
B
-meson, and nucleon physics with the aim of making them easily accessible to the nuclear and particle physics communities. More ...specifically, we report on the determination of the light-quark masses, the form factor
f
+
(
0
)
arising in the semileptonic
K
→
π
transition at zero momentum transfer, as well as the decay constant ratio
f
K
/
f
π
and its consequences for the CKM matrix elements
V
us
and
V
ud
. Furthermore, we describe the results obtained on the lattice for some of the low-energy constants of
S
U
(
2
)
L
×
S
U
(
2
)
R
and
S
U
(
3
)
L
×
S
U
(
3
)
R
Chiral Perturbation Theory. We review the determination of the
B
K
parameter of neutral kaon mixing as well as the additional four
B
parameters that arise in theories of physics beyond the Standard Model. For the heavy-quark sector, we provide results for
m
c
and
m
b
as well as those for
D
- and
B
-meson decay constants, form factors, and mixing parameters. These are the heavy-quark quantities most relevant for the determination of CKM matrix elements and the global CKM unitarity-triangle fit. We review the status of lattice determinations of the strong coupling constant
α
s
. Finally, in this review we have added a new section reviewing results for nucleon matrix elements of the axial, scalar and tensor bilinears, both isovector and flavor diagonal.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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