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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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Near Infrared Spectroscopy

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Dr. Rishabh Pathak

Near Infrared Spectroscopy (NIRS) is a non-invasive optical imaging technique that measures changes in blood oxygenation levels in the brain by detecting near-infrared light absorption. 

1.     Principle:

    • Near Infrared Spectroscopy (NIRS) is based on the principle that near-infrared light can penetrate biological tissues, including the human skull, allowing for the measurement of changes in blood oxygen levels in the brain.
    • NIRS utilizes near-infrared light sources and detectors placed on the scalp to monitor changes in light absorption, which are indicative of variations in oxygenated and deoxygenated hemoglobin concentrations in the brain.

2.     Applications:

    • NIRS is commonly used in neuroscience research to study brain activity, cognitive functions, and hemodynamic responses during various tasks and stimuli.
    • NIRS has applications in studying cognitive processes, language processing, motor functions, emotional responses, and developmental changes in the brain, particularly in infants and young children.

3.     Advantages:

    • Non-Invasive: NIRS is a non-invasive imaging technique that does not require exposure to ionizing radiation, making it safe for use in various populations, including infants, children, and clinical populations.
    • Portable and Flexible: NIRS systems are portable and adaptable for use in different settings, such as laboratories, hospitals, and research facilities, allowing for flexible data collection and monitoring.

4.     Limitations:

    • Depth of Penetration: NIRS has limited depth penetration compared to other neuroimaging techniques like fMRI, restricting its ability to measure brain activity in deeper brain regions.
    • Signal Contamination: NIRS signals can be affected by scalp blood flow, motion artifacts, and signal contamination from superficial tissues, requiring careful data processing and artifact correction.

5.     Research and Clinical Use:

    • NIRS is used in cognitive neuroscience research to investigate brain function, neural correlates of behavior, and developmental changes in brain activity.
    • In clinical settings, NIRS is employed to study neurological disorders, brain injuries, stroke rehabilitation, and cognitive impairments, providing valuable insights into brain function and hemodynamic responses in patient populations.

In summary, Near Infrared Spectroscopy (NIRS) is a valuable non-invasive optical imaging technique used in neuroscience research and clinical settings to study brain activity, cognitive functions, and hemodynamic responses. NIRS offers advantages such as portability, safety, and flexibility, making it a versatile tool for investigating brain function and neural processes in various populations and experimental conditions.

 

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