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Unveiling Hidden Neural Codes: SIMPL – A Scalable and Fast Approach for Optimizing Latent Variables and Tuning Curves in Neural Population Data

Dr. Rishabh Pathak
This research paper presents SIMPL (Scalable Iterative Maximization of Population-coded Latents), a novel, computationally efficient algorithm designed to refine the estimation of latent variables and tuning curves from neural population activity. Latent variables in neural data represent essential low-dimensional quantities encoding behavioral or cognitive states, which neuroscientists seek to identify to understand brain computations better. Background and Motivation Traditional approaches commonly assume the observed behavioral variable as the latent neural code. However, this assumption can lead to inaccuracies because neural activity sometimes encodes internal cognitive states differing subtly from observable behavior (e.g., anticipation, mental simulation). Existing latent variable models face challenges such as high computational cost, poor scalability to large datasets, limited expressiveness of tuning models, or difficulties interpreting complex neural network-based functio...
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Microscopic Structure of Bone

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Dr. Rishabh Pathak

The microscopic structure of bone tissue reveals a hierarchical organization that contributes to its strength, flexibility, and functionality. The key components of the microscopic structure of bone include:


1.    Osteon (Haversian System):

o    The basic structural unit of compact bone tissue.

o    Consists of concentric lamellae (layers) of bone matrix surrounding a central Haversian canal.

o    The Haversian canal contains blood vessels, nerves, and lymphatics that supply nutrients and remove waste products from bone cells.

o    Osteocytes are housed in lacunae within the lamellae and communicate with each other and with blood vessels through canaliculi (tiny channels).

2.    Lamellae:

o    Layers of bone matrix that make up the concentric rings within an osteon.

o    Collagen fibers in the lamellae provide tensile strength and flexibility to bone tissue.

o    Lamellae are arranged in different orientations to resist mechanical stresses and distribute loads effectively.

3.    Interstitial Lamellae:

o    Fill the spaces between intact osteons or remnants of old osteons.

o    Represent areas where bone remodeling has occurred or where new osteons are being formed.

4.    Circumferential Lamellae:

o    Encircle the outer and inner surfaces of compact bone, providing structural support and strength to the bone.

o    Help resist torsional forces and maintain the cylindrical shape of long bones.

5.    Trabeculae:

o    Found in spongy (cancellous) bone, forming a network of interconnected bony struts.

o    Trabeculae provide structural support, help distribute forces, and contain red bone marrow for hematopoiesis.

o    Spaces between trabeculae are filled with bone marrow and blood vessels.

6.    Bone Marrow:

o    Red bone marrow within trabecular spaces is the site of hematopoiesis, producing blood cells.

o    Yellow bone marrow in the medullary cavity of long bones stores fat and serves as an energy reserve.

7.    Periosteum and Endosteum:

o    The periosteum covers the outer surface of bones, providing a protective and nourishing layer.

o    The endosteum lines the inner surfaces of bones and contains osteoprogenitor cells involved in bone remodeling and repair.

8.    Cement Lines:

o    Thin, mineralized lines that mark the boundaries between adjacent osteons or lamellae.

o    Represent sites of previous bone deposition and remodeling.

The intricate microscopic structure of bone tissue, including osteons, lamellae, trabeculae, bone marrow, and connective tissues, reflects its adaptation to withstand mechanical stresses, support metabolic functions, and maintain skeletal integrity. Understanding the microscopic organization of bone is crucial for comprehending its biomechanical properties, remodeling processes, and role in overall musculoskeletal health.

 

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