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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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Cooccurring waves in Breach effects

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Dr. Rishabh Pathak


In the context of breach effects in EEG recordings, several co-occurring waves and patterns may be observed.


1.      Focal Slowing:

o Focal slowing may co-localize with breach effect rhythms, especially when the underlying tissue near the skull defect is abnormal.

o Trauma-induced or surgically produced skull defects may exhibit higher amplitude slowing with a sharp contour within the breach effect region, indicating potential cerebral injury or dysfunction.

2.     Paroxysmal Fast Activity (PFA):

o Paroxysmal fast activity (PFA) may be present alongside breach effects, characterized by bursts of fast activity interspersed with normal rhythms.

o PFA can co-localize with independent focal slowing, suggesting underlying abnormalities or dysfunction in the cerebral tissue near the skull defect.

3.     Epileptiform Discharges:

o  Epileptiform discharges (IEDs) may occur within a region affected by breach effects, potentially related to the cause of the skull defect.

o  Normal brain activity may exhibit spike-like, epileptiform appearances within breach effect regions, requiring careful analysis to differentiate between epileptic spikes and normal rhythms.

4.    Eye Movement Artifact Reduction:

o  In cases where the skull defect is within the frontal bone, the breach effect may reduce ipsilateral eye movement artifact by shunting the eye's electrical field through the defect, affecting the distribution of the artifact across the frontal aspect of the head.

5.     Clinical Significance:

o  While breach effects are not indicative of brain abnormalities and are related to bone abnormalities, the presence of abnormal slowing or low amplitude within breach effect regions may signal cerebral pathology.

o Recognizing and documenting breach effects is crucial for accurate EEG interpretation, as they can prevent misidentification of activity as abnormal by future readers of the EEG.

By understanding the co-occurring waves and patterns associated with breach effects in EEG recordings, clinicians can better interpret and differentiate between postoperative changes near skull defects, abnormal brain activity, and artifacts. Identifying these co-occurring features is essential for accurate diagnosis and management of patients undergoing EEG evaluations in the presence of skull defects or surgical interventions.

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