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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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Cardiac Artifacts compared to Benign Epileptiform Transients of Sleep

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Dr. Rishabh Pathak

Cardiac artifacts and benign epileptiform transients of sleep (BETS) are distinct patterns that can be observed in EEG recordings. Some of the key points differentiating cardiac artifacts from BETS:

1.     Cardiac Artifacts:

o  Source: Cardiac artifacts, such as ECG artifacts, pacemaker artifacts, and pulse artifacts, result from the electrical or mechanical effects of cardiac activity on EEG electrodes.

o  Characteristics: These artifacts are time-locked to cardiac contractions and may exhibit waveform distortions resembling poorly formed QRS complexes.

o  Location: Cardiac artifacts are often prominent in channels that include electrodes low on the head, such as ear or mastoid electrodes.

o Regular Intervals: Cardiac artifacts may show periodic occurrences with intervals that are multiples of a similar time interval related to the cardiac cycle.

2.   Benign Epileptiform Transients of Sleep (BETS):

o Description: BETS are transient epileptiform discharges that occur during non-REM sleep and are considered benign physiological phenomena.

o Characteristics: BETS typically comprise individual transients of low amplitude, unchanged waveform, and occur in the mid-temporal regions during sleep.

oTemporal Correspondence: The temporal correspondence to simultaneously recorded ECG can help differentiate BETS from other patterns.

o Regular Intervals: BETS may exhibit a regular interval between the waves, but this feature is less consistent compared to cardiac artifacts.

Key Differences:

  • Waveform: Cardiac artifacts often exhibit poorly formed QRS complexes, while BETS show unchanged waveform characteristics during sleep.
  • Location: Cardiac artifacts are more likely to occur in channels with electrodes low on the head, whereas BETS are typically observed in the mid-temporal regions during sleep.
  • Regularity: Cardiac artifacts may demonstrate more regular intervals related to the cardiac cycle, whereas the regularity of BETS intervals can vary.

Understanding these differences is essential for accurate interpretation of EEG recordings, as distinguishing between cardiac artifacts and BETS can help prevent misinterpretations and ensure the reliability of EEG data analysis in clinical and research settings.

 

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