Biology subjects

Lee, T.-S.

Publications and source records attributed to Lee, T.-S..

3 recordsLinked to original sources

bioRxiv2024

Computational constraints underlying theemergence of functional domains in thetopological map of Macaque V4

V4, an intermediate visual area in the ventral visual stream of primates, is known to contain neurons tuned to color, complex local patterns, shape, and texture. Neurons with similar visual attribute preferences are closely positioned on the cortical surface, forming a topological map. Recent studies based on multielectrode arrays and calcium imaging revealed the macaque V4 has neuronal columns tuned to specific natural image features, and these columns are clustered into various functional domains. There are domains tuned to attributes generally associated with object surface properties such as texture or color, as well as domains associated with the shape and form of object boundaries reminiscent of the blobs and inter-blobs in the primary visual cortex. Here, we explored the computational constraints underlying the development of the V4 topological map. We found that the map learned based on self-organizing principles constrained by neuronal columns tuning and retinotopy position can account for many characteristics of the observed V4 map, including the interwoven organization of texture and shape processing clusters. These anatomical clustering, with the implied local recurrent connectivity, might facilitate a modular parallel processing of surfaces and boundaries of objects along the ventral visual system.

neuroscience↗

bioRxiv2023

Cue-Invariant Geometric Structure of the Population Codes in Macaque V1 and V2

AO_SCPLOWBSTRACTC_SCPLOWOur ability to recognize objects and scenes, whether they appear in photographs, cartoons, or simple line drawings, is striking. Studies have shown that infants, members of isolated Stone Age tribes, and non-human primates can readily identify objects from line drawings. These findings suggest that the brain may inherently generate neural representations that align across different rendering cues, enabling abstraction. To test this hypothesis, we investigated the representational invariance of complex patterns of surface boundaries found in natural scenes. We tested whether individual neurons in V1 and V2 of the macaque monkey responded similarly to the presentation of these patterns across different renderings (i.e., as contours, luminance-defined patches, and segments of natural images). We found that individual neurons exhibit some degree of tuning invariance, stronger in V1 than in V2. At the population level, as a means to assess cue-invariant abstract representation, we measured decoding accuracy across cues ( cue-transfer decoding). We found that this decoding is greatly enhanced when a geometric transformation (Procrustes Transformation) is first performed to align the population activities across cues. It is also effective when applied to different populations of neurons within or across visual areas. These results were compared with populations of artificial neurons from models of the ventral visual streams, further indicating that cue-invariance stabilizes with population size. In summary, we found that while individual neurons exhibit some cue-invariance properties, the stability of the population geometry emerges as a more robust candidate for supporting a cue-invariant representation of visual information in the early visual areas. SIGNIFICANT STATEMENTHow can we easily recognize objects and scenes in a wide range of renderings, such as photographs, cartoons, or line drawings? One possibility is that our visual system processes information using an invariant representation. To investigate this hypothesis, we designed a stimulus set made of boundary patterns extracted from natural scenes, and displayed using three distinct renderings. We found that, while the tuning preference of individual V1 and V2 neurons displayed some correlation across renderings, a more robust invariant representation could be achieved when analyzing neural population geometry. Overall, we found that a cue-invariant representation of visual elements in the early visual areas may rest primarily on the geometry of the population responses, rather than individual neurons tuning characteristics.

neuroscience↗

bioRxiv2019

Unveiling the crucial role of type IV secretion system and motility of Helicobacter pylori in IL-1β production via NLRP3 inflammasome activation in neutrophils

Helicobacter pylori is a gram-negative, microaerophilic, and spiral-shaped bacterium and causes gastrointestinal diseases in human. IL-1{beta} is a representative cytokine produced in innate immune cells and is considered to be a key factor in the development of gastrointestinal malignancies. However, the mechanism of IL-1{beta} production by neutrophils during H. pylori infection is still unknown. We designed this study to identify host and bacterial factors involved in regulation of H. pylori-induced IL-1{beta} production in neutrophils. We found that H. pylori-induced IL-1{beta} production is abolished in NLRP3-, ASC-, and caspase-1/11-deficient neutrophils, suggesting essential role for NLRP3 inflammasome in IL-1{beta} response against H. pylori. Host TLR2, but not TLR4 and Nod2, was also required for transcription of NLRP3 and IL-1{beta} as well as secretion of IL-1{beta}. H. pylori lacking cagL, a key component of the type IV secretion system (T4SS), induced less IL-1{beta} production in neutrophils than did its isogenic WT strain, whereas vacA and ureA were dispensable. Moreover, T4SS was involved in caspase-1 activation and IL-1{beta} maturation in H. pylori-infected neutrophils. We also found that FlaA is essential for H. pylori-mediated IL-1{beta} production in neutrophils, but not dendritic cells. TLR5 and NLRC4 were not required for H. pylori-induced IL-1{beta} production in neutrophils. Instead, bacterial motility is essential for the production of IL-1{beta} in response to H. pylori. In conclusion, our study shows that host TLR2 and NLRP3 inflammasome and bacterial T4SS and motility are essential factors for IL-1{beta} production by neutrophils in response to H. pylori.\n\nIMPORTANCEIL-1{beta} is a representative pro-inflammatory cytokine and is considered to be a central host factor for the development of gastric cancers. Although neutrophils have been considered to be involved in H. pylori-induced gastric inflammation, the underlying mechanism by which H. pylori triggers IL-1{beta} production in neutrophils remains to be defined. In this study, our data suggested a critical role for the host TLR2 and NLRP3 inflammasome in IL-1{beta} production by neutrophil during H. pylori infection. Moreover, we found the bacterial factors, T4SS and FlaA, to be essential for IL-1{beta} production and NLRP3 activation during the course of H. pylori infection. Our current findings provide detailed molecular genetic mechanisms associated with IL-1{beta} production in neutrophils in response to H. pylori infection, which can serve as innovative anti-inflammatory targets to reduce H. pylori-induced gastric malignancies.

immunology↗