Auditory Electrophysiology - part 1 (Basic concepts)

Abstract

Neurons communicate through synapses. Communication between neurons does not occur through direct contact between one neuron and another; rather, communication takes place between neurons in a space called the synaptic space, synaptic cleft, or intersynaptic space (figure 1). A neuron releases neurotransmitters-chemical messengers-that pass on information across the synapse to the next neuron. Synapses can take two different forms: electrical synapses or chemical synapses.

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CENA NEWS - DOI: 10.13140/RG.2.2.23248.17928 - VOL.26, MARCH/2022
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AUDITORY ELECTROPHYSIOLOGY
PART 1 - BASIC CONCEPTS
Electrophysiology is the study of
the electrical properties of cells
and tissues. Electrophysiology
is a science within the area of
neuroscience and physiology
which involves the measurement
of ion flow, more specifically, the
electrical potentials of neurons.
Milaine Dominici Sanfins and Piotr Henryk Skarzynski
Neurons communicate through
synapses. Communication
between neurons does not occur
through direct contact between
one neuron and another; rather,
communication takes place
between neurons in a space called
the synaptic space, synaptic cleft,
or intersynaptic space (figure 1). A
neuron releases neurotransmitters
– chemical messengers – that
pass on information across the
synapse to the next neuron.
Synapses can take two different
forms: electrical synapses or
chemical synapses.

CENA NEWS - DOI: 10.13140/RG.2.2.23248.17928 - VOL.26, MARCH/2022 3
THE ELECTRICAL SYNAPSE
THE CHEMICAL SYNAPSE
Figure 1: Representation of communication
between neurons
works by communicating local
currents. The information
transmitted by a neuron is passed on
fully to the next neuron, so there is
no loss of information. The electrical
synapse allows information to be
passed on quickly, almost instantly;
however, if there is to be no risk of
information loss, the quality of the
operates by communicating
neurotransmitters that are
responsible for transmitting
information. A characteristic of this
synapse model is that it is based
on the most active neurons, that
is, information will be transmitted
faster in the most active synapses.
Consequently, there is a memory
of this synaptic response and,
thus, the nervous system starts to
privilege the activated pathway
in the next stimulations. Briefly,
the chemical synapse response
depends on the frequency of
neuron activation, the intensity of
activation, as well as the effective
participation of neurotransmitters.
presynaptic neuron is extremely
important. Briefly, the effectiveness
of the electrical synapse is related
to the quality of the presynaptic
neuron, the speed of transmission
of neuronal information, as well
as the unimpaired participation of
neurotransmitters.

CENA NEWS - DOI: 10.13140/RG.2.2.23248.17928 - VOL.26, MARCH/2022
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Electrophysiology is based on measuring neuronal responses.
Electrophysiology is widely used in various fields of health science, such
as cardiology, neurology, ophthalmology and audiology.
This bulletin is devoted to the electrophysiology of hearing, whose first
reports appear at the end of the 18th century.
Technological advances and
the cheapening of computer
systems due to production on an
industrial scale made it possible for
electrophysiological assessments
to be available not only in university
centers but also in diagnostic
clinics and, thus, their use is now
widespread.
Furthermore, it should be noted that
electrophysiological procedures
are objective assessments, that is,
they do not require, in most cases,
the active participation of the
patient. Compared to objective
assessment methods such as
magnetic resonance, computed
tomography, and single photon
emission computed tomography
(SPECT), electrophysiological
assessment is, in financial terms, a
more accessible procedure.
Electrophysiological assessment,
unlike MRI, CT, and SPECT
assessments, depends on the
integrity of the molecular systems
and membranes that are responsible
for axon communication and
synaptic transmission. Evaluators
must be aware that each
methodology has its particularities
and, depending on the diagnostic
purpose, the most indicated and
effective procedure should be
chosen.
Electrophysiological tools are
fundamental in diagnosis,
intervention, and monitoring
programs for various pathologies.

CENA NEWS - DOI: 10.13140/RG.2.2.23248.17928 - VOL.26, MARCH/2022 5
The electrophysiology of hearing
enables the analysis of the entire
auditory trajectory. Each type
of procedure allows the analysis
of specific areas of the auditory
nervous system, which can
contribute to understanding the
structures and functions involved
in the processing of auditory
information.
The electrophysiology of
hearing and/or auditory evoked
potential consists of analyzing the
electroencephalogram responses
to sound stimulation (the eliciting
stimulus can be different, such as a
click, tone burst, or speech, among
others) (figure 2).
Stay tuned for our next
newsletters, we will come back
to this topic that is so important
within audiology.
Figure 2: Representation of the electrophysiological
assessment of hearing (electroencephalogram + auditory stimulation)
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CENA NEWS - DOI: 10.13140/RG.2.2.23248.17928 - VOL.26, MARCH/2022
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1) Skarzynski PH, Kolodziejak
A, Sanfins MD. Eletrofisiologia da
Audição. In: Menezes PL; Sanfins
MD; Capra D; Andrade KCL; Frizzo
ACF. Manual de Eletrofisiologia
e Eletroacústica: um guia para
clínicos. Ribeirão Preto: BookToy.
2022.
2) Misulis KE. Spehlmann´s
Evoked Potential Primer: Visual,
Auditory and Somatosensory
Evoked Potentials in Clinical
Diagnosis. Butterworth-Heinemann
Medical. 2003.
3) Wikipedia. https://
pt.wikipedia.org/wiki/
Eletrofisiologia. Day of access:
21/01/2022.
Consulted References:

CENA NEWS - DOI: 10.13140/RG.2.2.23248.17928 - VOL.26, MARCH/2022 7
Authors
DR. MILAINE
DOMINICI SANFINS
- Postdoctoral Fellowship by World Hearing Center.
- Doctorate by School of Medical Sciences, State University of
Campinas (FCM-UNICAMP) and Università degli Studi di Ferrara
- Italy
- Master by School of Medical, University of São Paulo (FMUSP)
- Speech Pathology and Audiologist by School of Medical,
University of São Paulo (FMUSP)
- Audiology Specialist by the Federal Board of Speech
Pathology.
- Researcher of World Hearing Center of Institute of Physiology
and Pathology of Hearing, Institute of Sensory Organs, IPESQ
and Respirare-Ouvire Clinic.
- Founding Partner of Center of Advanced Neuroaudiology and
Electrophysiology/ Centro de Eletrofisiologia e Neuroaudiologia
Avançada (CENA
DR. PIOTR HENRYK
SKARZYNSKI
- Professor, ENT, Master and Doctorate by Medical University of
Warsaw.
- He finished four specializations: Otorhinolaryngology, Pediatric
Otorhinolaryngology, Audiology and Phoniatrics and Public
Health.
- Honorary Member of ORL Danube Society and Société
Française d’Oto-Rhino-Laryngologie, and a member of the
Roster of Experts on Digital Health of WHO.
- Member of Congress and Meeting Department of European
Academy of Otology and Neuro-Otology.
- Vice-President and Institutional Representative of International
Society for Telemedicine and e-Health.
- Regional Representative of Europe of International
Society of Audiology and Board Secretary of the Society of
Otorhinolaryngologists, Phoniatrists and Audiologists.
- Auditor of European Federation of Audiology Societies.
- Member of the FNS (Facial Nerve Stimulation) Steering
Committee.
- Member of Implantable Hearing Devices Committee and
Otology & Neurotology Education Committee by American
Academy of Otolaryngology-Head and Neck Surgery.
- Scientific work in World Hearing Center of Institute of
Physiology and Pathology of Hearing, Institute of Sensory
Organs and Medical University of Warsaw.