Related Experiment Video
Updated: May 29, 2026
10:31
In Vitro Wedge Slice Preparation for Mimicking In Vivo Neuronal Circuit Connectivity
Published on: August 18, 2020
The sound of silence: ionic mechanisms encoding sound termination
Cornelia Kopp-Scheinpflug1, Adam J B Tozer, Susan W Robinson
1MRC Toxicology Unit, Hodgkin Building, University of Leicester, Leicester LE1 9HN, UK.
Neuron
|September 10, 2011
Summary
Scientists discovered how auditory neurons in the brainstem generate rapid offset responses. This involves specific ionic mechanisms converting sound-induced inhibition into precise neural firing, crucial for detecting gaps in communication.
Area of Science:
- Neuroscience
- Auditory Neuroscience
- Cellular Electrophysiology
Background:
- Offset responses to stimulus termination are vital for perceptual grouping and gap detection.
- Auditory gaps are critical in vocal communication, yet the ionic mechanisms for fast offset responses remain unclear.
- The superior paraolivary nucleus (SPN) in the brainstem exhibits offset firing, converting sound-induced inhibition into action potentials (APs).
Purpose of the Study:
- To elucidate the ionic mechanisms underlying fast offset firing in the superior paraolivary nucleus (SPN).
- To understand how inhibitory postsynaptic potentials (IPSPs) trigger precise action potential firing upon sound cessation.
Main Methods:
- Whole-cell patch recordings were performed in vitro on brainstem slices.
- Electrophysiological techniques were used to analyze membrane potential changes and ionic currents.
- Investigated the roles of chloride reversal potential (E(Cl)), hyperpolarization-activated nonspecific cationic current (I(H)), and T-type calcium conductance (I(TCa)).
Main Results:
- Offset firing in the SPN is triggered by inhibitory postsynaptic potentials (IPSPs), not excitatory postsynaptic potentials (EPSPs).
- A combination of large IPSPs (driven by a negative E(Cl)) and a significant I(H) generates offset APs.
- I(H) accelerates the membrane time constant, enabling rapid repolarization and precise offset firing upon stimulus termination.
Conclusions:
- Action potential firing can emerge from strong inhibition through the integration of specific ionic currents.
- The identified ionic mechanism involving E(Cl) and I(H) explains the fast and precise offset responses in the SPN.
- This mechanism provides a basis for detecting critical temporal gaps in auditory signals, including vocalizations.
More Related Videos
Related Concept Videos
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.
01:22Hair 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.
01:11The Auditory Ossicles
The auditory ossicles of the middle ear transmit sounds from the air as vibrations to the fluid-filled cochlea. The auditory ossicles consist of two malleus (hammer) bones, two incus (anvil) bones, and two stapes (stirrups), one on each side. These bones develop during the fetal stage and are the ones to ossify first. They are fully mature at birth and do not grow afterward.
The aptly named stapes look very much like a stirrup. The three ossicles are unique to mammals, and each plays a role in...
The aptly named stapes look very much like a stirrup. The three ossicles are unique to mammals, and each plays a role in...
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...
01:15Auditory 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...
01:31Hearing
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.