Related Experiment Video
Updated: May 20, 2026
07:52
Multiscale Investigations of Cortical Processing by Integrating Laminar Polytrodes and Optogenetics with Micro Electrocorticography in Rodents
Published on: May 23, 2025
Hierarchical transformations in sound envelope encoding differ across cortical layers
Chase A Mackey1, Yoshinao Kajikawa1,2
1Center for Biomedical Imaging and Neuromodulation, Nathan Kline Institute for Psychiatric Research, 140 Old Orangeburg Rd, Orangeburg, NY 10962, United States.
Cerebral Cortex (New York, N.Y. : 1991)
|May 19, 2026
Summary
Nonhuman primates reveal how brain circuits transform amplitude-modulation (AM) encoding across cortical areas and hemispheres. This study highlights differences in temporal sensitivity and hemispheric specialization in auditory processing.
Area of Science:
- Neuroscience
- Auditory Neuroscience
- Primate Neurobiology
Background:
- Amplitude-modulation (AM) is crucial for complex sound perception.
- Understanding AM encoding transformations is key to primate-specific auditory processing.
- Nonhuman primates (NHPs) offer a model to study hierarchical and interhemispheric AM encoding.
Purpose of the Study:
- Investigate AM signal encoding across cortical layers and hemispheres in primary auditory cortex (A1) and parabelt (PB) areas of NHPs.
- Characterize the circuit mechanisms underlying AM encoding transformations.
- Identify differences in temporal sensitivity and hemispheric specialization.
Main Methods:
- Recorded neural activity from awake NHPs using linear array multielectrodes spanning cortical layers.
- Presented amplitude-modulated noise and click trains to measure AM encoding.
- Analyzed AM encoding as a function of cortical layer and hemisphere in A1 and PB.
Main Results:
- A1 encoded all AM frequencies (1.6-200 Hz) with high accuracy; PB encoded lower frequencies (1.6-25 Hz).
- A1 showed a Granular > Infragranular > Supragranular laminar gradient, inverted in PB (Supragranular > Infragranular > Granular).
- Both areas exhibited enhanced AM encoding in the left hemisphere's supragranular layers.
Conclusions:
- Identified distinct temporal sensitivities in auditory circuits across the cortical hierarchy.
- The parabelt (PB) area shows unique AM encoding properties compared to A1.
- Local supragranular neuronal populations may contribute to hemispheric specialization in auditory processing.
Related Concept Videos
01:15Auditory Pathway
Auditory pathways constitute the complex neural circuits responsible for transmitting and interpreting auditory information from the peripheral auditory system to the brain. Sound waves are initially captured by the outer ear, funneled through the ear canal, and reach the tympanic membrane (eardrum). These vibrations are transmitted via the middle ear's ossicles to the inner ear's cochlea.
When viewed cross-sectionally, the cochlea reveals the scala vestibuli and scala tympani flanking the...
When viewed cross-sectionally, the cochlea reveals the scala vestibuli and scala tympani flanking the...
01:13The Cochlea
The cochlea is a coiled structure in the inner ear that contains hair cells—the sensory receptors of the auditory system. Sound waves are transmitted to the cochlea by small bones attached to the eardrum called the ossicles, which vibrate the oval window that leads to the inner ear. This causes fluid in the chambers of the cochlea to move, vibrating the basilar membrane.
01:31Hearing
When we hear a sound, our nervous system is detecting sound waves—pressure waves of mechanical energy traveling through a medium. The frequency of the wave is perceived as pitch, while the amplitude is perceived as loudness.
01:21Perceiving Loudness, Pitch, and Location
The human brain perceives pitch through two primary mechanisms reflected in place theory and frequency theory. Each mechanism describes how sound waves are interpreted as specific pitches by the brain, offering insights into the intricate processes of auditory perception.
Place theory, or place coding, suggests that different pitches are heard because various sound waves activate specific locations along the cochlea's basilar membrane. The brain determines the pitch of a sound by identifying...
Place theory, or place coding, suggests that different pitches are heard because various sound waves activate specific locations along the cochlea's basilar membrane. The brain determines the pitch of a sound by identifying...
01:22Hair Cells
Hair cells are the sensory receptors of the auditory system—they transduce mechanical sound waves into electrical energy that the nervous system can understand. Hair cells are located in the organ of Corti within the cochlea of the inner ear, between the basilar and tectorial membranes. The actual sensory receptors are called inner hair cells. The outer hair cells serve other functions, such as sound amplification in the cochlea, and are not discussed in detail here.
01:16Anatomy of the Ear
Auditory sensation, commonly called hearing, involves the transformation of sonic waves into neural impulses facilitated by the structures of the auditory organ. The prominent, flesh-like structure on the side of the head, called the auricle, directs sound waves towards the auditory canal. The auricle is often mislabeled as the pinna, a term more aligned with mobile structures like a feline's external ear. The auditory canal penetrates the cranium via the external auditory meatus of the...