Editing Electrophysiology (section)

==Definition and scope==

===Classical electrophysiological techniques===
====Principle and mechanisms====
Electrophysiology<ref>{{cite web | url=https://www.bmseed.com/extracellular-electrophysiology | title=Explore BMSEED's extracellular electrophysiology solutions. ✓ sensitive signal detection ✓ non-invasive recording ✓ optimized for neural and cardiac cells ➔ Elevate your electrophysiology research! }}</ref> is the branch of physiology that pertains broadly to the flow of ions ([[ion current]]) in biological tissues and, in particular, to the electrical recording techniques that enable the measurement of this flow. Classical electrophysiology techniques involve placing [[electrodes]] into various preparations of biological tissue.  The principal types of electrodes are:
# Simple solid conductors, such as discs and needles (singles or arrays, often insulated except for the tip),
# Tracings on printed circuit boards or flexible polymers, also insulated except for the tip, and
# Hollow, often elongated or 'pulled', tubes filled with an electrolyte, such as glass pipettes filled with [[potassium chloride]] solution or another electrolyte solution.

The principal preparations include:
# living organisms (example [https://www.youtube.com/watch?v=Gav_rJhBfWY&list=PL7949yMfsdqgqEGqHwKeiBWR8aPUkEtuk&index=7 in insects]),
# excised tissue (acute or cultured),
# dissociated cells from excised tissue (acute or cultured),
# artificially grown cells or tissues, or
# hybrids of the above.
Neuronal electrophysiology is the study of electrical properties of biological cells and tissues within the nervous system. With neuronal electrophysiology doctors and specialists can determine how neuronal disorders happen, by looking at the individual's brain activity. Activity such as which portions of the brain light up during any situations encountered.
If an electrode is small enough (micrometers) in diameter, then the [[wikt:Special:Search/electrophysiologist|electrophysiologist]] may choose to insert the tip into a single cell.  Such a configuration allows direct observation and [https://www.youtube.com/playlist?list=PL7949yMfsdqgqEGqHwKeiBWR8aPUkEtuk intracellular recording] of the [[intracellular]] electrical activity of a single cell. However, this invasive setup reduces the life of the cell and causes a leak of substances across the cell membrane.

Intracellular activity may also be observed using a specially formed (hollow) glass pipette containing an electrolyte.  In this technique, the microscopic pipette tip is pressed against the cell membrane, to which it tightly adheres by an interaction between glass and lipids of the cell membrane.  The electrolyte within the pipette may be brought into fluid continuity with the cytoplasm by delivering a pulse of negative pressure to the pipette in order to rupture the small patch of membrane encircled by the pipette rim ([[Patch clamp#Whole-cell recording or whole-cell patch|whole-cell recording]]). Alternatively, ionic continuity may be established by "perforating" the patch by allowing exogenous pore-forming agents within the electrolyte to insert themselves into the membrane patch ([[Patch clamp#Perforated patch|perforated patch recording]]).  Finally, the patch may be left intact ([[Patch clamp|patch recording]]).

The electrophysiologist may choose not to insert the tip into a single cell. Instead, the electrode tip may be left in continuity with the extracellular space. If the tip is small enough, such a configuration may allow indirect observation and recording of [[action potential]]s from a single cell, termed [[single-unit recording]]. Depending on the preparation and precise placement, an extracellular configuration may pick up the activity of several nearby cells simultaneously, termed [[Multielectrode array|multi-unit recording]].

As electrode size increases, the resolving power decreases.  Larger electrodes are sensitive only to the net activity of many cells, termed [[local field potentials]].  Still larger electrodes, such as uninsulated needles and surface electrodes used by clinical and surgical neurophysiologists, are sensitive only to certain types of synchronous activity within populations of cells numbering in the millions.

Other classical electrophysiological techniques include [[Patch clamp|single channel recording]] and [[amperometry]].

====Electrographic modalities by body part====

Electrophysiological recording in general is sometimes called electrography (from ''[[wikt:electro-#Prefix|electro-]]'' + ''[[wikt:-graphy#Suffix|-graphy]]'', "electrical recording"), with the record thus produced being an electrogram. However, the word ''electrography'' has other [[word sense|senses]] (including [[Kirlian photography|electrophotography]]), and the specific types of electrophysiological recording are usually called by specific names, constructed on the pattern of ''electro-'' + [body part [[classical compound|combining form]]] + ''-graphy'' (abbreviation ExG). Relatedly, the word ''electrogram'' (not being needed for those other [[word sense|senses]]) often carries the specific meaning of intracardiac electrogram, which is like an electrocardiogram but with some invasive leads (inside the heart) rather than only noninvasive leads (on the skin). Electrophysiological recording for clinical [[medical diagnosis|diagnostic]] purposes is included within the category of [[electrodiagnostic testing]]. The various "ExG" modes are as follows:

{| class="wikitable sortable"
! Modality !! Abbreviation !! Body part !! Prevalence in clinical use
|-
| [[electrocardiography]] || ECG or EKG || [[heart]] (specifically, the [[cardiac muscle]]), with cutaneous electrodes (noninvasive) || 1—very common
|-
| electroatriography || EAG || [[atrium (heart)|atrial]] cardiac muscle || 3—uncommon
|-
| electroventriculography || EVG || [[ventricle (heart)|ventricular]] cardiac muscle || 3—uncommon
|-
| intracardiac electrogram || EGM || [[heart]] (specifically, the [[cardiac muscle]]), with intracardiac electrodes (invasive) || 2—somewhat common
|-
| [[electroencephalography]] || EEG || [[brain]] (usually the [[cerebral cortex]]), with extracranial electrodes || 1—very common
|-
| [[electrocorticography]] || ECoG or iEEG || [[brain]] (specifically the cerebral cortex), with intracranial electrodes || 2—somewhat common
|-
| [[electromyography]] || EMG || [[muscle]]s throughout the body (usually [[skeletal muscle|skeletal]], occasionally [[smooth muscle tissue|smooth]]) || 1—very common
|-
| [[electrooculography]] || EOG || [[eye]]—entire globe || 2—somewhat common
|-
| [[electroretinography]] || ERG || [[eye]]—[[retina]] specifically || 2—somewhat common
|-
| [[electronystagmography]] || ENG || [[eye]]—via the corneoretinal potential || 2—somewhat common
|-
| [[electro-olfactography|electroolfactography]] || EOG || [[olfactory epithelium]] in mammals || 3—uncommon
|-
| [[electroantennography]] || EAG || [[olfactory receptor]]s in arthropod antennae || 4—not applicable clinically
|-
| [[electrocochleography]] || ECOG or ECochG || [[cochlea]] || 2—somewhat common
|-
| [[electrogastrogram|electrogastrography]] || EGG || [[stomach]] smooth muscle || 2—somewhat common
|-
| [[electrogastroenterogram|electrogastroenterography]] || EGEG || stomach and bowel smooth muscle || 2—somewhat common
|-
| [[electroglottograph]]y || EGG || [[glottis]] || 3—uncommon
|-
| [[electropalatography]] || EPG || [[palate|palatal]] contact of tongue || 3—uncommon
|-
| electroarteriography || EAG || [[artery|arterial]] flow via streaming potential detected through skin<ref>{{US patent|4425922A}}</ref> || 3—uncommon
|-
| electroblepharography || EBG || [[eyelid]] muscle || 3—uncommon
|-
| [[biofeedback#Electrodermograph|electrodermography]] || EDG || [[skin]] || 3—uncommon
|-
| electropancreatography || EPG || [[pancreas]] || 3—uncommon
|-
| electrohysterography || EHG || [[uterus]] || 3—uncommon
|-
| [[electroneuronography]] || ENeG or ENoG || [[nerve]]s || 3—uncommon
|-
| [[pneumograph#Electrical|electropneumography]] || EPG || [[lung]]s (chest movements) || 3—uncommon
|-
| electrospinography || ESG || [[spinal cord]] || 3—uncommon
|-
| electrovomerography || EVG || [[vomeronasal organ]] || 3—uncommon
|-
|}

===Optical electrophysiological techniques===

Optical electrophysiological techniques were created by scientists and engineers to overcome one of the main limitations of classical techniques. Classical techniques allow observation of electrical activity at approximately a single point within a volume of tissue. Classical techniques singularize a distributed phenomenon.  Interest in the spatial distribution of bioelectric activity prompted development of molecules capable of emitting light in response to their electrical or chemical environment.  Examples are [[voltage sensitive dye]]s and fluorescing proteins.
After introducing one or more such compounds into tissue via perfusion, injection or gene expression, the 1 or 2-dimensional distribution of electrical activity may be observed and recorded.{{cn|date=August 2024}}