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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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International 10-20 System Rules

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Dr. Rishabh Pathak

The International 10-20 System is a standardized method for electrode placement in EEG recordings. The system is based on specific rules for positioning electrodes on the scalp relative to anatomical landmarks. Here are some key rules of the International 10-20 System:


1.Measurement Method: Electrode placement is determined by measuring distances between specific landmarks on the head. The nasion (bridge of the nose) and inion (bump at the back of the head) define the sagittal midline, while the preauricular points (above the ears) define the coronal midline.


2.Incremental Measurements: Electrodes are positioned at specific percentages along the sagittal and coronal midlines. The 10-20 System uses 10% and 20% increments along these lines to determine electrode locations.


3.Letter Prefix and Number Suffix: Electrode locations are named using a letter prefix indicating the region of the head (e.g., F for frontal, C for central) and a number suffix indicating the exact location within the region. Odd numbers typically represent the left side, even numbers the right side, and "z" indicates the midline.


4.Consistency in Naming: The naming convention ensures consistency in electrode location identification across different EEG recordings and interpretations. For example, Fp1 represents the left frontal pole, F4 is over the right frontal lobe, and Cz is at the vertex.


5.10-10 System: A revised version of the 10-20 System, known as the 10-10 System, addresses inconsistencies in electrode naming, especially for midtemporal electrodes. It provides a more precise naming scheme for electrode locations.


6.Standardization and Accuracy: The 10-20 System promotes standardization in EEG electrode placement, minimizing variations in electrode positioning across different individuals and ensuring accurate correspondence between electrodes and brain structures.


By following these rules and guidelines of the International 10-20 System, EEG technicians and clinicians can accurately and consistently place electrodes on the scalp for EEG recordings, facilitating proper interpretation and analysis of EEG data.

 

Electrode Location Names according to the International 10-20 System

The International 10-20 System is a standardized method for electrode placement in EEG recordings. Here are the electrode location names according to the International 10-20 System:

1.      Fp1, Fp2: Frontopolar (Prefrontal)

2.     F7, F8: Frontal

3.     F3, F4: Frontal

4.    C3, C4: Central

5.     P3, P4: Parietal

6.    O1, O2: Occipital

7.     T3, T4: Temporal

8.    T5, T6: Temporal

These electrode locations are crucial for standardizing EEG electrode placement across individuals and institutions, ensuring consistency in recording and interpretation of EEG data.

 

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