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A tight relationship between BOLD fMRI activation/deactivation and increase/decrease in single neuron responses in human association cortex

The relationship between Blood-Oxygen-Level-Dependent (BOLD) responses in functional magnetic resonance imaging (fMRI) and increases or decreases in neural firing rate across human brain regions, especially the association cortex, remains largely unknown. Here, we contrast direct measures of neuronal activity in two adjacent brain regions of the fusiform gyrus (FG) associated with fMRI increases (lateral FG portion) or decreases (medial FG portion) of the same category-selective neural activity. In both individual brains tested across multiple recording sessions, a frequency-tagging stimulation objectively identified a substantial proportion (about 70%) of face-selective neurons. While single-units recorded in the lateral FG showed a selective increase to faces, neurons localized in the medial FG decreased spiking activity selectively to faces. Beyond a relative reduction to faces compared to non-face objects, about a third of single neurons found in the medial FG showed genuine suppression of baseline spiking activity upon presentation of a face. These observations clarify the nature of face-selective neural activity in the human brain, which can be expressed both as increases and active suppressions of spiking activity, and, more generally, shed light on the physiological basis of the fMRI signal.

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Open Access Just Published
A tight relationship between BOLD fMRI activation/deactivation and increase/decrease in single neuron responses in human association cortex

The relationship between Blood-Oxygen-Level-Dependent (BOLD) responses in functional magnetic resonance imaging (fMRI) and increases or decreases in neural firing rate across human brain regions, especially the association cortex, remains largely unknown. Here, we contrast direct measures of neuronal activity in two adjacent brain regions of the fusiform gyrus (FG) associated with fMRI increases (lateral FG portion) or decreases (medial FG portion) of the same category-selective neural activity. In both individual brains tested across multiple recording sessions, a frequency-tagging stimulation objectively identified a substantial proportion (about 70%) of face-selective neurons. While single-units recorded in the lateral FG showed a selective increase to faces, neurons localized in the medial FG decreased spiking activity selectively to faces. Beyond a relative reduction to faces compared to non-face objects, about a third of single neurons found in the medial FG showed genuine suppression of baseline spiking activity upon presentation of a face. These observations clarify the nature of face-selective neural activity in the human brain, which can be expressed both as increases and active suppressions of spiking activity, and, more generally, shed light on the physiological basis of the fMRI signal.

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Open Access Just Published
Search for <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi>η</mml:mi></mml:mrow><mml:mrow><mml:mi>c</mml:mi></mml:mrow></mml:msub><mml:mo stretchy="false">(</mml:mo><mml:mn>2</mml:mn><mml:mi>S</mml:mi><mml:mo stretchy="false">)</mml:mo><mml:mo stretchy="false">→</mml:mo><mml:msup><mml:mrow><mml:mi>K</mml:mi></mml:mrow><mml:mrow><mml:mo>+</mml:mo></mml:mrow></mml:msup><mml:msup><mml:mrow><mml:mi>K</mml:mi></mml:mrow><mml:mrow><mml:mo>−</mml:mo></mml:mrow></mml:msup><mml:msup><mml:mrow><mml:mi>η</mml:mi></mml:mrow><mml:mrow><mml:mo>′</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math> decay

Using (2.712±0.014)×109 ψ(2S) events collected with the BESIII detector operating at the BEPCII, we search for the ηc(2S)→K+K−η′ decay. Its decay branching fraction is measured to be (11.11±4.67(stat)±1.82(syst)±4.24(extr))×10−4, where the first uncertainty is statistical, the second is systematic, and the third uncertainty is from the branching fraction of the ψ(2S)→γηc(2S) decay. The statistical significance is 2.8σ. The upper limit on the product branching fraction B[ψ(2S)→γηc(2S)]×B[ηc(2S)→K+K−η′] is set to be 0.94×10−6 at 90% confidence level. In addition, the branching fractions of χc1→K+K−η′ and χc2→K+K−η′ are updated to be (8.48±0.10(stat)±0.47(syst))×10−4 and (1.53±0.04(stat)±0.08(syst))×10−4, respectively. The precision is improved by twofold. Published by the American Physical Society 2025

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Open Access
Symmetry Strategy for Rapid Discovery of Abundant Fractional Quantum Ferroelectrics.

Traditional ferroelectrics are limited by Neumann's principle, which confines exploration of ferroelectrics within polar point groups. Our recent work [Ji etal., Nat. Commun. 15, 135 (2024)NCAOBW2041-172310.1038/s41467-023-44453-y] proposes the concept of fractional quantum ferroelectricity (FQFE) that extends the playground of ferroelectricity to nonpolar point groups. Here, we apply group theory and introduce an efficient symmetry strategy to identify FQFE candidates. Integrated with a high-throughput screening scheme, we go through 171 527 materials and identify 221 potential FQFE candidates, which are already experimentally synthesized. In addition, we point out for the first time that the essence of FQFE is fractional atomic displacements with respect to lattice vectors, which can actually result in both fractional (type I) and integer (type II) quantized polarization, respectively. Through performing first-principles calculations, we verify the symmetry-predicted switchable FQFE properties in bulk AlAgS_{2} and monolayer HgI_{2}. Notably, AlAgS_{2} exhibits an ultralow switching barrier of 22 meV/f.u. and interlocked in-plane/out-of-plane polarization, while HgI_{2} displays large spontaneous polarization of 42 μC/cm^{2}. Our findings not only advance the understanding on FQFE, but also offer guidance for experimental exploration and design of novel ferroelectric materials.

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