Steady-State Measurement and Analysis for Profiling Auditory Evoked Potentials from Short- to Long-Latency
This invention measures brain responses to repeated sounds, from basic reflexes to complex thought. Unlike older methods, it analyzes the *rhythm* of these responses, making it more objective and reliable. This helps assess hearing and brain function across all ages, even in sleep, providing a clearer picture of brain activity.
Description
The invention profiles auditory evoked potentials (AEPs) by applying a steady-state response (SSR) approach across a wide range of latencies, from brainstem to cortical activity. It uses repeated tone-burst stimuli with systematically varied envelope parameters (rise/fall times, duration) adjusted according to repetition rate (from 0.625 Hz to 80 Hz) to maintain neural synchrony. Brain electrical activity is measured via sensors and processed using spectral analysis to identify fundamental and harmonic components of the evoked potential. A key technical feature is the calculation of a "harmonic sum" (HS), which quantifies the overall amplitude of the evoked potential by summing the square root of the sum of squares of amplitudes of the fundamental and harmonic spectral components that exceed noise levels, providing a comprehensive measure of total response power. This method allows for objective, quantitative analysis robust to subject state and maturation, and is implemented by a system comprising an auditory signal generator, sensors, a processor for spectral and HS analysis, and an output display.Applications
1. Clinical Diagnosis and Monitoring of Auditory and Neurological Disorders: The invention provides an objective, comprehensive, and robust method for profiling auditory pathway function from brainstem to cortex, enabling accurate diagnosis and monitoring of various auditory and central nervous system conditions, especially in challenging populations like children or sedated patients.2. Auditory Neuroscience Research and Drug Development: The invention offers a precise and objective tool for scientific investigation into auditory processing, brain function, and the effects of interventions, by providing quantitative profiles of evoked potentials across a broad range of latencies and subject conditions.
Advantages
1. Reduced Subjectivity and Ambiguity: Unlike traditional transient AEP methods that rely on subjective peak identification in time-domain waveforms, this invention uses spectral analysis and a harmonic sum metric, providing objective and quantitative measures of auditory evoked potentials.2. Extended Latency Range and Comprehensive Profiling: Existing SSR methods and high-frequency ASSRs typically focus on short- to middle-latency (brainstem) responses. This invention extends analysis to very low repetition rates (down to 0.75 Hz), enabling comprehensive profiling of auditory pathway function from brainstem to cortical levels, offering a more complete assessment of auditory processing.
3. Robustness to Arousal State and Developmental Changes: Traditional transient AEPs and evoked response audiometry are significantly confounded by sleep state and maturation. The invention's steady-state responses remain robust during light sleep and provide clear, quantifiable results in children, addressing a major limitation in assessing uncooperative or developing populations.
4. Improved Signal-to-Noise Separation and Accuracy: Traditional methods struggle to isolate signal from noise and may not capture total response power accurately. The invention's spectral analysis, harmonic sum calculation, and objective noise estimation (e.g., via dual buffers) allow for clearer quantification of response components and more accurately capture total response power, even when the fundamental frequency is not dominant.
5. Broader Clinical Diagnostic Utility: The objective, comprehensive profiling across latency domains and robustness in diverse populations (children, adults, potentially brain-damaged subjects) makes the invention suitable for diagnosing a wider range of central nervous system disorders (developmental, degenerative, traumatic, metabolic, toxic) compared to the more limited applications of traditional AEPs or existing high-frequency ASSRs.
6. Amenability to Automated Analysis: Unlike traditional AEP methods that often require subjective manual interpretation of waveforms, the invention's objective, quantitative spectral measures are amenable to automated scoring and tracking, facilitating clinical and research applications.