Protracted neuronal recruitment in the temporal lobes of young children.

The temporal lobe of the human brain contains the entorhinal cortex (EC). This region of the brain is a highly interconnected integrative hub for sensory and spatial information; it also has a key role in episodic memory formation and is the main source of cortical hippocampal inputs1-4. The human EC continues to develop during childhood5, but neurogenesis and neuronal migration to the EC are widely considered to be complete by birth. Here we show that the human temporal lobe contains many young neurons migrating into the postnatal EC and adjacent regions, with a large tangential stream persisting until the age of around one year and radial dispersal continuing until around two to three years of age. By contrast, we found no equivalent postnatal migration in rhesus macaques (Macaca mulatta). Immunostaining and single-nucleus RNA sequencing of ganglionic eminence germinal zones, the EC stream and the postnatal EC revealed that most migrating cells in the EC stream are derived from the caudal ganglionic eminence and become LAMP5+RELN+ inhibitory interneurons. These late-arriving interneurons could continue to shape the processing of sensory and spatial information well into postnatal life, when children are actively interacting with their environment. The EC is one of the first regions of the brain to be affected in Alzheimer's disease, and previous work has linked cognitive decline to the loss of LAMP5+RELN+ cells6,7. Our investigation reveals that many of these cells arrive in the EC through a major postnatal migratory stream in early childhood.

ERK signaling expands mammalian cortical radial glial cells and extends the neurogenic period.

The molecular basis for cortical expansion during evolution remains largely unknown. Here, we report that fibroblast growth factor (FGF)-extracellular signal-regulated kinase (ERK) signaling promotes the self-renewal and expansion of cortical radial glial (RG) cells. Furthermore, FGF-ERK signaling induces bone morphogenic protein 7 (Bmp7) expression in cortical RG cells, which increases the length of the neurogenic period. We demonstrate that ERK signaling and Sonic Hedgehog (SHH) signaling mutually inhibit each other in cortical RG cells. We provide evidence that ERK signaling is elevated in cortical RG cells during development and evolution. We propose that the expansion of the mammalian cortex, notably in human, is driven by the ERK-BMP7-GLI3R signaling pathway in cortical RG cells, which participates in a positive feedback loop through antagonizing SHH signaling. We also propose that the relatively short cortical neurogenic period in mice is partly due to mouse cortical RG cells receiving higher SHH signaling that antagonizes ERK signaling.

Dlx1/2-dependent expression of Meis2 promotes neuronal fate determination in the mammalian striatum.

The striatum is a central regulator of behavior and motor function through the actions of D1 and D2 medium-sized spiny neurons (MSNs), which arise from a common lateral ganglionic eminence (LGE) progenitor. The molecular mechanisms of cell fate specification of these two neuronal subtypes are incompletely understood. Here, we found that deletion of murine Meis2, which is highly expressed in the LGE and derivatives, led to a large reduction in striatal MSNs due to a block in their differentiation. Meis2 directly binds to the Zfp503 and Six3 promoters and is required for their expression and specification of D1 and D2 MSNs, respectively. Finally, Meis2 expression is regulated by Dlx1/2 at least partially through the enhancer hs599 in the LGE subventricular zone. Overall, our findings define a pathway in the LGE whereby Dlx1/2 drives expression of Meis2, which subsequently promotes the fate determination of striatal D1 and D2 MSNs via Zfp503 and Six3.

Generation of a terahertz quasi-Pearcey beam and its investigation in ptychography.

The terahertz structured beams played a significant role in imaging. We utilized the transmitter with 0.1 THz to generate the quasi-Pearcey beam. The beam is produced by combining the self-designed parabola-slit modulated plate and Fourier lens, showing stripe-shaped pattern and self-focusing property. Based on that, introducing it into the testing of ptychography, we discovered there are decent effects in field reconstruction of the probe and sample with this beam by comparisons both in the simulations and the experiments. The beam has good spatial coherence through the analysis of the spatial frequency spectrums. It suggests that the beam with such features can take advantage of rapid reconstruction in full-field imaging.

Nondestructive measurement of terahertz optical thin films by machine learning based on physical consistency.

Optical scattering measurement is one of the most commonly used methods for non-contact online measurement of film properties in industrial film manufacturing. Terahertz photons have low energy and are non-ionizing when measuring objects, so combining these two methods can enable online nondestructive testing of thin films. In the visible light band, some materials are transparent, and their thickness and material properties cannot be measured. Therefore, a method based on physical consistency modeling and machine learning is proposed in this paper, which realizes the method of obtaining high-precision thin film parameters through single-frequency terahertz wave measurement, and shows good performance. Through the experimental measurement of organic material thin films, it is proved that the proposed method is an effective terahertz online detection technology with high precision and high throughput.

Terahertz fan-beam computed tomography.

A terahertz (THz) fan-beam computed tomography (CT) system using a 0.3 THz continuous-wave sheet beam is proposed. The diffraction-free sheet beam expands in a fan shape in only one direction and provides propagation-invariant focal lines and extended the depth-of-field. The fan-beam CT based on this beam is the second-generation THz CT. It breaks the conventional 4-f symmetric structure of THz CT using the parallel beam. The fan-beam THz CT allows for use with a linear array detector, which reduces the time required to collect data. To demonstrate its feasibility for three-dimensional (3D) imaging, the 3D structure of a metal rod packed in a carton is reconstructed with the support of the system. The results show that the object's internal structure can be obtained by this new THz CT system while retaining the geometrically magnified features of the cross-sectional structure. The results of our research provide a template for the second-generation THz CT system, which provides an additional method for nondestructive testing.

Human hippocampal neurogenesis drops sharply in children to undetectable levels in adults.

New neurons continue to be generated in the subgranular zone of the dentate gyrus of the adult mammalian hippocampus. This process has been linked to learning and memory, stress and exercise, and is thought to be altered in neurological disease. In humans, some studies have suggested that hundreds of new neurons are added to the adult dentate gyrus every day, whereas other studies find many fewer putative new neurons. Despite these discrepancies, it is generally believed that the adult human hippocampus continues to generate new neurons. Here we show that a defined population of progenitor cells does not coalesce in the subgranular zone during human fetal or postnatal development. We also find that the number of proliferating progenitors and young neurons in the dentate gyrus declines sharply during the first year of life and only a few isolated young neurons are observed by 7 and 13 years of age. In adult patients with epilepsy and healthy adults (18-77 years; n = 17 post-mortem samples from controls; n = 12 surgical resection samples from patients with epilepsy), young neurons were not detected in the dentate gyrus. In the monkey (Macaca mulatta) hippocampus, proliferation of neurons in the subgranular zone was found in early postnatal life, but this diminished during juvenile development as neurogenesis decreased. We conclude that recruitment of young neurons to the primate hippocampus decreases rapidly during the first years of life, and that neurogenesis in the dentate gyrus does not continue, or is extremely rare, in adult humans. The early decline in hippocampal neurogenesis raises questions about how the function of the dentate gyrus differs between humans and other species in which adult hippocampal neurogenesis is preserved.

A fluorescence detection method for postharvest tomato epidermal defects based on improved YOLOv5m.

BACKGROUND: Tomato quality visual grading is greatly affected by the problems of smooth skin, uneven illumination and invisible defects that are difficult to identify. The realization of intelligent detection of postharvest epidermal defects is conducive to further improving the economic value of postharvest tomatoes. RESULTS: An image acquisition device that utilizes fluorescence technology has been designed to capture a dataset of tomato skin defects, encompassing categories such as rot defects, crack defects and imperceptible defects. The YOLOv5m model was improved by introducing Convolutional Block Attention Module and replacing part of the convolution kernels in the backbone network with Switchable Atrous Convolution. The results of comparison experiments and ablation experiments show that the Precision, Recall and mean Average Precision of the improved YOLOv5m model were 89.93%, 82.33% and 87.57%, which are higher than YOLOv5m, Faster R-CNN and YOLOv7, and the average detection time was reduced by 47.04 ms picture-1. CONCLUSION: The present study utilizes fluorescence imaging and an improved YOLOv5m model to detect tomato epidermal defects, resulting in better identification of imperceptible defects and detection of multiple categories of defects. This provides strong technical support for intelligent detection and quality grading of tomatoes. © 2024 Society of Chemical Industry.

Plasmodium transcription repressor AP2-O3 regulates sex-specific identity of gene expression in female gametocytes.

Male and female gametocytes are sexual precursor cells essential for mosquito transmission of malaria parasite. Differentiation of gametocytes into fertile gametes (known as gametogenesis) relies on the gender-specific transcription program. How the parasites establish distinct repertoires of transcription in the male and female gametocytes remains largely unknown. Here, we report that an Apetala2 family transcription factor AP2-O3 operates as a transcription repressor in the female gametocytes. AP2-O3 is specifically expressed in the female gametocytes. AP2-O3-deficient parasites produce apparently normal female gametocytes. Nevertheless, these gametocytes fail to differentiate into fully fertile female gametes, leading to developmental arrest in fertilization and early development post-fertilization. AP2-O3 disruption causes massive upregulation of transcriptionally dormant male genes and simultaneously downregulation of highly transcribed female genes in the female gametocytes. AP2-O3 targets a substantial proportion of the male genes by recognizing an 8-base DNA motif. In addition, the maternal AP2-O3 is removed after fertilization, which is required for the zygote to ookinete development. Therefore, the global transcriptional repression of the male genes in the female gametocytes is required for safeguarding female-specific transcriptome and essential for the mosquito transmission of Plasmodium.

Transcription factors Bcl11a and Bcl11b are required for the production and differentiation of cortical projection neurons.

The generation and differentiation of cortical projection neurons are extensively regulated by interactive programs of transcriptional factors. Here, we report the cooperative functions of transcription factors Bcl11a and Bcl11b in regulating the development of cortical projection neurons. Among the cells derived from the cortical neural stem cells, Bcl11a is expressed in the progenitors and the projection neurons, while Bcl11b expression is restricted to the projection neurons. Using conditional knockout mice, we show that deficiency of Bcl11a leads to reduced proliferation and precocious differentiation of cortical progenitor cells, which is exacerbated when Bcl11b is simultaneously deleted. Besides defective neuronal production, the differentiation of cortical projection neurons is blocked in the absence of both Bcl11a and Bcl11b: Expression of both pan-cortical and subtype-specific genes is reduced or absent; axonal projections to the thalamus, hindbrain, spinal cord, and contralateral cortical hemisphere are reduced or absent. Furthermore, neurogenesis-to-gliogenesis switch is accelerated in the Bcl11a-CKO and Bcl11a/b-DCKO mice. Bcl11a likely regulates neurogenesis through repressing the Nr2f1 expression. These results demonstrate that Bcl11a and Bcl11b jointly play critical roles in the generation and differentiation of cortical projection neurons and in controlling the timing of neurogenesis-to-gliogenesis switch.

Positive Controls in Adults and Children Support That Very Few, If Any, New Neurons Are Born in the Adult Human Hippocampus.

Adult hippocampal neurogenesis was originally discovered in rodents. Subsequent studies identified the adult neural stem cells and found important links between adult neurogenesis and plasticity, behavior, and disease. However, whether new neurons are produced in the human dentate gyrus (DG) during healthy aging is still debated. We and others readily observe proliferating neural progenitors in the infant hippocampus near immature cells expressing doublecortin (DCX), but the number of such cells decreases in children and few, if any, are present in adults. Recent investigations using dual antigen retrieval find many cells stained by DCX antibodies in adult human DG. This has been interpreted as evidence for high rates of adult neurogenesis, even at older ages. However, most of these DCX-labeled cells have mature morphology. Furthermore, studies in the adult human DG have not found a germinal region containing dividing progenitor cells. In this Dual Perspectives article, we show that dual antigen retrieval is not required for the detection of DCX in multiple human brain regions of infants or adults. We review prior studies and present new data showing that DCX is not uniquely expressed by newly born neurons: DCX is present in adult amygdala, entorhinal and parahippocampal cortex neurons despite being absent in the neighboring DG. Analysis of available RNA-sequencing datasets supports the view that DG neurogenesis is rare or absent in the adult human brain. To resolve the conflicting interpretations in humans, it is necessary to identify and visualize dividing neuronal precursors or develop new methods to evaluate the age of a neuron at the single-cell level.

Single optical element to generate a meter-scale THz diffraction-free beam.

Diffraction-free electromagnetic beam propagates in free space without change in its two-dimensional transverse profile. Elongating diffraction-free length can benefit the practical application of this beam. Here, we demonstrate that a THz diffraction-free beam with meter-scale length can be achieved by using only one optical element. By circumscribing the line-shape of spherical harmonic function on a traditional axicon, such optical element is designed, and then can be fabricated by 3D-printing technique. Simulated, experimental, and theoretical results all show that the diffraction-free length of generated beam is over 1000 mm. Further analysis based on Fourier optics theory indicates that the spatial frequency of this beam has a comb distribution, which plays a key role during the beam generation process. Moreover, such distribution also demonstrates the beam generated by our invented optical element is not the Bessel beam, but a new diffraction-free beam. It is believed that this meter-scale THz diffraction-free beam can be useful in a non-contact and non-destructive THz imaging system for large objects.

Terahertz ptychography using a long-distance diffraction-free beam as the probe.

We have implemented a terahertz (THz) ptychographic technique using a long-distance diffraction-free beam (DFB) instead of traditional low-energy pinhole-defined illumination as the probe. The DFB generating system containing two lens-axicon doublets is very easily realized. Measured transverse intensities of such a DFB display an Airy-pattern-like distribution. Based on the well-developed extended ptychographic iterative engine, we simultaneously reconstruct a phase object and the DFB probe with both simulated and real data. Further calculation shows that the DFB has abundant spatial high-frequency components that guarantee high coherence of the illuminating probe beam in our THz ptychographic system. In addition, we firmly believe that the proposed approach can be easily transplanted to the ptychography at other frequency bands as both lens and axicon are very common optical elements.

Optical element to generate zero-order quasi-Bessel beam with "focal length".

An optical element has been invented to generate a zero-order quasi-Bessel beam with a certain distance to the element, which does not exist in the zero-order quasi-Bessel beam by using a traditional axicon. The cross section of designed element is an isosceles triangle whose equal sides are circumscribed by two semi-ellipses. Using a well-developed three-dimensional (3D)-printing technique, we have fabricated a series of elements working at terahertz (THz) frequency. Both simulated and experimental results clearly show that there is a certain distance between the generated quasi-Bessel beam and this element. A physical analysis based on geometric optics theory is performed to explain the obtained results. Because it is a refractive transmitted optical element, we propose that it can be also realized at another frequency band if the relevant processing techniques are available.

SP8 and SP9 coordinately promote D2-type medium spiny neuron production by activating Six3 expression.

Dopamine receptor DRD1-expressing medium spiny neurons (D1 MSNs) and dopamine receptor DRD2-expressing medium spiny neurons (D2 MSNs) are the principal projection neurons in the striatum, which is divided into dorsal striatum (caudate nucleus and putamen) and ventral striatum (nucleus accumbens and olfactory tubercle). Progenitors of these neurons arise in the lateral ganglionic eminence (LGE). Using conditional deletion, we show that mice lacking the transcription factor genes Sp8 and Sp9 lose virtually all D2 MSNs as a result of reduced neurogenesis in the LGE, whereas D1 MSNs are largely unaffected. SP8 and SP9 together drive expression of the transcription factor Six3 in a spatially restricted domain of the LGE subventricular zone. Conditional deletion of Six3 also prevents the formation of most D2 MSNs, phenocopying the Sp8/9 mutants. Finally, ChIP-Seq reveals that SP9 directly binds to the promoter and a putative enhancer of Six3 Thus, this study defines components of a transcription pathway in a regionally restricted LGE progenitor domain that selectively drives the generation of D2 MSNs.

Structuring a terahertz beam by using a 3D-printed n-faced pyramid lens.

Using 3D-printed n-faced pyramid lenses, we generate a series of structured diffraction free terahertz (THz) beams. Based on angular spectrum theory, analytical solutions of the output THz beams from these lenses can be obtained. Furthermore, we experimentally realize these non-diffraction THz beams, showing that the measured results are consistent with theory. It is believed that our structured non-diffraction THz beams can be used in THz imaging with large depth of focus.

Nonlinear error correction for Terahertz FMCW System by a new beat frequency estimation method.

Terahertz (THz) frequency modulated continuous wave (FMCW) technology is a means of nondestructive testing. The signal's nonlinearity is an unavoidable problem in the daily application of THz FMCW technology. The signal's nonlinearity will lead to the spectrum broadening of the FMCW's beat frequency (BF) signal, which degrades the range resolution and result in distance-measuring error. Traditional methods require additional hardware or require a lot of computation, which are not conducive to the miniaturization of the system and real-time measurement. A novel method for correcting the nonlinear error of THz FMCW technology has been proposed and demonstrated in this article. In the proposed method, the windowed Fourier transform (WFT) is introduced to estimate the BF corresponding to the measured target, according to the linearity distribution of voltage-controlled oscillator (VCO). In this way, the measured target's BF can be accurately estimated from the unprocessed BF signal with a poor linearity. From the estimated BF of the reference target, the non-linear compensation coefficients are calculated. With the non-linear compensation coefficients, the non-linearity of the output BF signal can be calibrated. The results of simulations and experiments show that the proposed method allows the range resolution of an FMCW system to reach the theoretical limit.

Transcription Factor 4 Safeguards Hippocampal Dentate Gyrus Development by Regulating Neural Progenitor Migration.

The dentate gyrus (DG) of the hippocampal formation plays essential roles in learning and memory. Defective DG development is associated with neurological disorders. Here, we show that transcription factor 4 (Tcf4) is essential for DG development. Tcf4 expression is elevated in neural progenitors of the dentate neuroepithelium in the developing mouse brain. We demonstrate that conditional disruption of Tcf4 in the dentate neuroepithelium leads to abnormal neural progenitor migration guided by disorganized radial glial fibers, which further leads to hypoplasia in the DG. Moreover, we reveal that Wnt7b is a key downstream effector of Tcf4 in regulating neural progenitor migration. Behavioral analysis shows that disruption of integrity of the DG impairs the social memory highlighting the importance of proper development of the DG. These results reveal a critical role for Tcf4 in regulating DG development. As mutations in TCF4 cause Pitt-Hopkins syndrome (PTHS) characterized by severe intellectual disability, our data also potentially provide insights into the basis of neurological defects linked to TCF4 mutations.

Line imaging of a terahertz zero-order Mathieu-Gauss beam.

Thestudy of terahertz (THz) structured beams has become an interesting subject. Here, we use 3D printed diffractive plates to generate a THz zero-order Mathieu-Gauss beam at a frequency of 0.1 THz and simulate its line-imaging effect. According to the nondiffraction property of the beam, we conduct a transmission imaging test by placing the imaging plate at different positions along the direction of beam propagation. The results show that the THz zero-order Mathieu-Gauss beam has a good imaging effect in the depth of field of about 130-380 mm. This can be used in large depth of field THz line imaging.

Generating terahertz perfect optical vortex beams by diffractive elements.

An effective experiment scheme is proposed to generate the terahertz (THz) perfect optical vortex (POV) beams by diffractive elements at the frequency of 0.1THz. Two diffractive elements are designed and fabricated by 3D-printing to form the generation system. The ring radius of the generated beams is independent of the topological charge and positive linear relationship with the radial wave vector. By controlling the radial wave vector, the ring radius can be freely adjusted. The experiment results are shown to corroborate the numerical simulation ones. Such generated beams hold promise for developing the novel THz fiber communication systems.