38 7 JANUARY 2022 • VOL 375 ISSUE 6576 science.org SCIENCE
RESEARCH | IN OTHER JOURNALS
of novel objects, showed that
this behavior was not regulated
by the dopamine reward-seeking
circuitry. This work provides
evidence for a clear dissociation
in the brain circuitry between
reward seeking and novelty
seeking. —PRS
Nat. Neurosci. 10.1038/
s41593-021-00950-1 (2021).
DECISION MAKING
Diagnosing heart attacks
A machine-learning algorithm for
heart attack risk that draws upon
patients’ health data suggests
that physicians substantially mis-
allocate tests for heart attacks.
Mullainathan and Obermeyer
studied 246,265 visits to a
large urban hospital emergency
department. Compared with
doctors’ aggregated decisions,
a preferred allocation informed
by the risk model would have
cut 62% of total tests, added
61% of new tests, and reduced
cost per life year by 34%. Three
limitations in physicians’ decision
making were identified: Their
model of risk is too simple, they
over-weight salient risks (e.g.,
demographics and symptoms),
and they over-weight symptoms
that are stereotypical of heart
attack (e.g., chest pain). —BW
Q. J. Econ. 10.1093/
qje/qjab046 (2021).MICROBIOLOGY
Keeping host cell
death at bay
The agent that causes
Legionnaire’s disease, Legionella
pneumophila, takes up residencein human macrophages and
hijacks their machinery to set
up a replicative niche. They are
helped in this task by injecting
more than 300 effector proteins
into the host cell using a so-called
type IV secretion system. One
intracellular target of some of
these effectors is the host cell
mitochondrion. Escoll et al. found
that infected macrophages, while
exhibiting reduced mitochondrial
oxidative phosphorylation, still
maintained a healthy mitochon-
drial membrane potential. Within
infected cells L. pneumophila
effectively reversed the activity of
the mitochondrial F0F1-ATPase
using cytosolic ATP to preserve
the mitochondrial membrane
potential. Blocking this activ-
ity collapsed the mitochondrial
membrane potential and the
infected cells then died. Thus, L.pneumophila puts its host cells on
a form of life support to preserve
its own replicative niche. —SMH
eLife 10 , e71978 (2021).QUANTUM OPTICS
Coupling quantum
emitters
Single photons from quantum
emitters can encode quan-
tum information across long
distances using optic fibers
and free space. For integrated
on-chip quantum optical
processing, arrays of quantum
emitters would form a local
network that could process the
single photons propagating
through the network. Yu et al.
present a photonic crystal-based
platform in which two quantum
emitters placed in nanocavities
spaced several micrometers
apart can be coupled. Their
photonic structure was designed
and fabricated so that the nano-
cavities are in resonance, which
enhances the coupling between
the two remote emitters. By
demonstrating mutual excitation
and the possibility of synchroni-
zation between the two emitters,
the scalable approach provides
a route to realize larger on-chip
quantum networks. —ISO
Optica 8 , 1605 (2021).GEOPHYSICS
A powerful cloth
Ferropericlase, one of the primary
mantle minerals, is known to
have an electronic spin transi-
tion. However, evidence of this
transition in the Earth’s mantle
has been challenging to find.
Shephard et al. found changes
in seismic wave speeds at two
depth ranges that correspond to
the iron spin transition in ferro-
periclase. The authors compared
compressional and sheer-wave
velocities in tomographic models,
finding relative changes between
the two types of waves that they
could attribute to the transition.
Using tomographic models is
important because nonuniform
thermochemical variations wash
the signal out in global, one-
dimensional models. —BG
Nat. Commun. 12 , 5905 (2021).NEURODEVELOPMENTHighways into the retina
M
icroglia, the macrophages in the brain, consume cellular debris and remove unnecessary
synapses. These handy cells do not originate from the neuroectoderm but rather are
generated through hematopoiesis. How, then, do they get into the brain? Ranawat and
Masai tracked fluorescently labeled cells through transparent zebrafish larva to follow
ingress of microglia during development. In zebrafish, the retina is among the first brain
tissues to be populated by microglia. The microglia are encouraged to migrate by cytokine
signals, use the surfaces of blood vessels as a pathway through the choroid fissure, and invade
the neurogenic region of the developing retina. —PJH eLife 10 , e70550 (2021).Fluorescence microscopy
image showing ocular
microglial precursors
(green) colonizing
the zebrafish
retinaIMAGE:ELIFE10, E70550 (2021