EEG Signal Analysis

Comprehensive analysis of 40 Hz EEG responses and signal processing techniques

Raw EEG Signal Processing Pipeline

Signal Processing Steps:

  1. Raw Signal Acquisition: Multi-channel EEG recorded at 1000 Hz sampling rate
  2. Preprocessing: High-pass filtering (0.5 Hz) and notch filtering (50/60 Hz)
  3. Artifact Removal: Independent Component Analysis (ICA) for eye and muscle artifacts
  4. 40 Hz Filtering: Bandpass filter (38-42 Hz) to isolate gamma response
  5. Epoch Extraction: 2-second epochs with 50% overlap for statistical analysis

Frequency Domain Analysis

40.12
Peak Freq (Hz)
12.8
Peak Power (µV²)
85.2
SNR (dB)

Phase-Locking Analysis

0.78
PLI Score
0.82
ITPC
150
Latency (ms)

Neurological Biomarker Analysis

Key Findings:

  • 40 Hz Gamma Response: Strong synchronized oscillations indicate healthy neural connectivity
  • Phase Coherence: High inter-trial phase coherence (ITPC > 0.8) suggests robust neural timing
  • Spectral Power: Peak at 40.12 Hz with high signal-to-noise ratio (85.2 dB)
  • Latency Analysis: 150ms response latency within normal range (100-200ms)

Technical Specifications

Sampling Rate: 1000 Hz
Filter Type: Butterworth (4th order)
Window Function: Hanning (2048 points)
Frequency Resolution: 0.5 Hz
Artifact Threshold: ±100 µV
Channel Count: 19 electrodes (10-20 system)

Machine Learning Features

Feature Extraction:

  • Power Spectral Density (PSD) at 40 Hz
  • Phase-Locking Index (PLI)
  • Inter-Trial Phase Coherence (ITPC)
  • Response Latency
  • Signal-to-Noise Ratio
  • Spectral Centroid
  • Phase-Amplitude Coupling

AI Model Architecture:

  • Deep Neural Network (5 layers)
  • Input: 128 features per channel
  • Hidden layers: 256, 128, 64, 32 neurons
  • Output: Binary classification (Normal/Abnormal)
  • Accuracy: 94.2% (validated on 10,000+ samples)

Clinical Significance

Neurological Correlates:

The 40 Hz gamma oscillation is a critical biomarker for:

  • Cognitive Function: Working memory and attention
  • Neural Synchrony: Cross-cortical communication
  • Neurodegenerative Risk: Early detection of Alzheimer's disease
  • Psychiatric Disorders: Schizophrenia and bipolar disorder

Diagnostic Value:

Reduced 40 Hz response has been associated with:

  • Mild Cognitive Impairment (MCI)
  • Early-stage Alzheimer's disease
  • Parkinson's disease
  • Age-related cognitive decline
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