Talk:Electrophysiology

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I
I agree with Dan. The current definition of electrophysiology at the top of the article excludes all extracellular techniques. I would reccommend adding mention of single-channel recordings. This is, after all, the reason why patch-clamping was developed, and it would permit lots of nice cross-indexing with the ion-channel article. -- Mattv May 6, 2006

I find the definition of electrophysiology in this article to be a little restrictive. How about broadening the definition to include the "studing electrical properties of biological systems" be they cells, tissues, and even organs. Some people may consider methods such as EKG and EOG to be electrophysiology as well. What do you guys think? -- Dan

I know that this is getting too long. I think the next big task is to break it up onto sub-pages. I need to put more topic headings in first. Synaptidude


 * That's exactly what I was going to suggest, rather than delete the old, incorporate it into your text. -Purkinje 23:36, 23 Jun 2005 (UTC)


 * Hey Purkinje,


 * ITA. I'm basically rewriting the whole thing (I'm an electrophysiologist), but there are good things in the old article, and I'm incorperating them as I go.  So I've not deleted them.  Things will get more organized as I work on the article, but, as I ssid, I want to respect the work of the original authors, so I'm leaving it for now, but will incorperate it into the overall structure before I'm done.


 * -Synaptidude


 * P.S. Do you exist mostly in a 2-dimentional plane? ;-)


 * I really like the major edits added recently by Synaptitude and the anonymous user, however the article now has a large amount of redundancy regarding techniques. It might be helpful to re-organize the entire thing so that it has a more logical integration of the old article and the new editsPurkinje 02:09, 23 Jun 2005 (UTC)

Re: request for cleanup
I'm working on this when I can. I have a lot of content to add, but I'll try to clean it up a bigt

Well, I think you should know that cardiologist who study and treat arrhythmias by radiofrequency ablation call our field Electrophysiology and ourselves Electrophysiologists. Silvia


 * Sylvia is correct that cardiological MDs who specialize in the electrical conductivity of the heart are called Electrophysioloists. This article mentions "Electrophysiologist" twice, but offers no definition of them nor link to an article about them (they seem to be referred to as general researchers here). Thank you for your time and upcoming corrections and additions, Wordreader (talk) 12:38, 25 July 2014 (UTC)

Separate pages
I agree with Purkinje and Synaptitude above that the page should be broken into more pages. What about separate pages for voltage and current clamp? delldot | talk 16:25, 23 November 2005 (UTC)
 * I'm going to go ahead and move the voltage clamp material to a new page. If you have concerns about this, you can move it back or discuss it with me here or on my talk page. delldot | talk 02:55, 25 November 2005 (UTC)

Old text (to be incorporated)
I'm moving this text here from the article itself so the article will look more professional. delldot | talk 16:58, 23 November 2005 (UTC)

_____________________________ Text below here is "old" and has not yet been incorperated into the new structure. Feel free to do so, I will get to it soon if someone else doesn't Synaptidude 23:02, 15 August 2005 (UTC) _____________________________

Current clamp
At the cellular level, these techniques include so-called passive recordings, sometimes referred to as "current clamp". Current clamp is used to record a cell's membrane potential. "Current clamp" is something of a misnomer, because nothing is "clamped" while using this technique. Unlike voltage clamp recording where the cell's membrane voltage is held, or "clamped", at a particular value, in current clamp recording, the current flow across the cell's membrane is not controlled. The misnaming derives from two sources. First current clamp is perceived as the "opposite" of voltage clamp, and second, when using current clamp, the experimenter has the opportunity to inject specificed current offsets into a cell. However, even with such offsets, the cell is still free to vary its membrane current in response to other stimuli. The experimenter has no direct control over the current flow across the cell's membrane. Current clamp is nothing more than a method of passively recording a cell's trans-membrane voltage with the added ability to produce voltage offsets by injecting current into the cell through the recording electrode. Current clamp is useful anytime the experimenter needs to record the voltage across a cell's membrane such as during studies of cell excitability by analyzing the action potentials under conditions more consistent with the cell's natural environment. Though most scientists understand that "current clamp" involves no clamping of anything, they still use the term as it has become the vernacular to describe voltametry.

The most common electrophysiological recording techniques establish electrical contact with the inside of a cell or tissue with a "glass electrode." Such an electrode is fashioned by the experimenter from a fine capillary glass tube, which is then pulled to an even finer (but still hollow of about 1 micrometer diameter for patch-clamp, 0.1 micrometer for intracellular "sharp electrode" recording) tip under heat and allowed to cool. This glass "micropipette" is then filled with a salt solution, and a silver chloride-coated silver wire is inserted to establish an electrochemical junction with the pipet fluid and the tissue or cell into which the pipet is inserted (typically with the aid of a microscope and finely adjustable pipet holders, known as micromanipulators). This salt electrode filling solution varies widely depending on the planned experiment. For sharp microelectrode intracellular recording, high concentration (2-3 molar) salt is used. Potassium chloride, potassium acetate, potassium methylsulfate are salts commonly used to fill shart microelectrode. Note that all contain potassium to match the predominant intracellular ion (although in special circumstance, cesium salts may be used instead of potassium). While a filling solution of potassium chloride gives the smallest and most stable electrochemical "junction potential" when in contact with silver chloride, care must be taken when using chloride as the counter ion to potassium. Injection of chloride ions into the cell will raise the chloride concentration and thus reverse the direction of the cell's choride currents (this characteristic is often used as an easy way to identify chloride currents). The chloride-coated silver wire connects back to the amplifier. Classically, electrophysiologists watched biological currents/voltages on an oscilloscope and recorded them onto chart paper/screen, but now the vast majority use computers. Other requirements are an air or sand table to reduce vibration, and a Faraday cage to eliminate outside interference from the tiny measured currents.

Where experiments require low impedance measurements and no ionic contribution from the microelectrode, the chloride solution is replaced with cerralow, a low melting temperature alloy. The tip is electroplated with soft gold and platinum black, from chloroplatinic acid. Electrodes of this type are used to measure electrical pulses in unmyelinated axons down to 100 nm.

There are four main types of cellular electrophysiological recordings:

1. Intracellular recording. This technique entails impaling a cell, usually a neuron, with a sharp glass electrode and recording either the voltage (current-clamp) or the current (voltage-clamp) across the membrane. This technique is widely used when recording from brain slices or when performing "in-vivo" recording from live animals. While sharp electrode recordings are typically used for recording voltage, voltage-clamp recordings can be performed by impaling larger cells with two sharp electrodes. This is the original voltage-clamp method, which has been superceeded by the superior patch-clamp recording (see below). The two-electrode voltage clamp was used by Alan Lloyd Hodgkin and Andrew Fielding Huxley to describe the ionic-basis of the action potential. This work won them the Nobel Prize in 1963.

2. Extracellular recording. In this technique an electrode is placed on the extracellular medium and field-potentials contributed by the action potentials of many neurons are recorded. Some popular clinical applications of extracellular recording are the electrocardiogram (ECG) and the electroencephalogram (EEG).

3. The patch-clamp technique. With this technique it is possible to clamp the cell potential (voltage-clamp) or the cell current (current-clamp) using a glass micropipette as explained previously. Current-clamp recordings allow the detection and measurement of action potentials in excitable cells such as neurons and the beta cells of the pancreas. Voltage-clamp recordings are very popular for measuring macroscopic currents in which the activity of many ion channels is occurring at the same time. However with this powerful technique it is also possible to measure the current flowing through a single ion channel and study its behavior. There are different modalities of the patch-clamp technique. This technique was developed by Erwin Neher and Bert Sakmann who received the Nobel Prize in 1991.
 * Cell attached mode.
 * Advantages: Single channels can be recorded and channel properties are not changed.
 * Disadvantages: Poor pharmacology.


 * Whole cell mode.
 * Advantages: Good pharmacology, large current is recorded because it is the whole cell.
 * Disadvantages: The cell is perforated so some cell contents are diluted.


 * Excised patch (inside-out or outside-out patch).
 * Advantages: Recordings can be taken from individual channels, good pharmacology and the inside/outside solutions can be changed.
 * Disadvantages: Risk that channel properties are changed.


 * Perforated patch.
 * Advantages: It is possible to obtain large, whole cell currents without washing out the intracellular medium.
 * Disadvantages: Impossible to record from single channels.

4. Axon recording.
 * Advantages: Chemistry of cell is unchanged, axon pulses are discriminated from the less frequent retrograde cell action potentials.
 * Disadvantages: Experimental protocol requirements are strict.


 * OK I should have looked at the talk page first before trying to salvage the present article; the above is great. There should probably be a section on contemporary multi-unit recording techniques (tetrodes etc) if anyone has the energy, and optical recording techniques Gleng 23:22, 23 February 2006 (UTC)

Having (now) looked at the structure of related articles, it seems perhaps sensible to leave details of the techniques to their respective specialised articles, while leaving this page as an overview of the different approaches, mentioning some highlights of their application. I have deleted the technical account of extracellular recording theory though not for this reason alone, but because I do not think that it is correct as far as single unit recording is concerned (though I think it is correct for field potential recording); most obviously, the action potentials recorded extracellularly from cell bodies are not generally inverted w.r.t. intracellular recordings, and there is no reversal when moving from extrcellular recording activity just outside a cell and penetrating that cell. Gleng 23:20, 25 February 2006 (UTC)

missing links, explanations
relation to photobiomodulation and photobiology?

Metals
Some IP editors keep trying to add a section to this page about electrical conduction in metals. It seems to me that this is clearly out of scope of this article, unless one has come to think that metals are living organisms! This is, after all, a page about an area of physiology. --Tryptofish (talk) 15:44, 4 January 2011 (UTC)


 * Are they talking about the electrical conductivity of specific metals, such as silver, that are used in electrophysiology? Or are they talking about the metals themselves? mezzaninelounge (talk) 16:32, 4 January 2011 (UTC)
 * Oh, would that it were the use of metals for electrophysiology. No, it's this: . Basically arguing that metals are part of a continuum with living things. It's obviously fringe science. The only reason I raised it in this talk is that they keep adding it back after I revert it, and I don't want to keep reverting without an explanation. --Tryptofish (talk) 22:49, 4 January 2011 (UTC)
 * I agree. Fringe science indeed. mezzaninelounge (talk) 23:09, 4 January 2011 (UTC)

Solid-supported membrane (SSM)-based electrophysiology
We are considering expanding the article with a section about the solid-supported membrane (SSM)-based electrophysiology. With this electrophysilogical approach, proteoliposomes, membrane vesicles or membrane fragments containing the channel or transporter of interest are adsorbed to a lipid monolayer painted over a functionalized electrode. This electrode consists on a glass support, a chromium layer, a gold layer, and an octadecyl mercaptane monolayer. As the painted membrane is supported by the electrode it is called a solid-supported membrane. Importantly, mechanical perturbations, which usually destroy a BLM, do not influence the life-time of a SSM. Indeed, the capacitive electrode (composed of the SSM and the absorbed vesicles) is mechanically so stable that solutions may be rapidly exchanged at its surface. This key property allows the application of rapid substrate/ligand concentration jumps to investigate the electrogenic activity of the protein of interest measured via capacitive coupling between the vesicles and the electrode. Jugarcel (talk) 06:54, 2 May 2011 (UTC)
 * Thanks for asking about this on the talk page! The key issues for you to think about are the need for sourcing to show that this method is being used sufficiently widely to justify inclusion here (see WP:RS and WP:UNDUE), and also that it isn't a commercial mention (see WP:COI). --Tryptofish (talk) 20:26, 2 May 2011 (UTC)


 * Thanks for your reply. You raised several points that I would like to justify:


 * 1) “the need for sourcing to show that this method is being used sufficiently widely to justify inclusion here”
 * The method is being used in only a few labs. Still we think that it could be included here because it has been shown that it is useful in the characterization of primary and secondary active transporters as well as for channels. It was established in 1999 and there are several publications in peer-reviewed journals (reviewed in Schulz, 2008). This method has also proven to be useful in cases where conventional electrophysiology can not be applied, like for bacterial transporters that can not be expressed in eukaryotic cells or for eukaryotic transporters from intracellular membranes. However, I understand this critic and if you think that it has not being used sufficiently widely, I will consider placing it in a different section.


 * 2) No commercial mention.
 * Our aim is just to describe the method and no mention to any company is made.


 * With best regards,
 * Juan Garcia.
 * 130.60.168.172 (talk) 11:15, 4 May 2011 (UTC)
 * Thanks so much for the further information. The review article you provided is fine for establishing notability, as it is a peer reviewed secondary source. Since you appear to be one of the authors of the review, I added the material to the page myself. Basically, I just used a copyedited version of your opening comment in this talk thread. --Tryptofish (talk) 19:56, 4 May 2011 (UTC)

Electrophysiology vs. Electrophysiology
I see that this has been discussed before, but maybe worth rehashing. In the clinical realm "Electrophysiology" is the study of the electrical signals from the heart as measured with external and/or internal electrodes. This is a well-established field with dedicated journals and so forth. In the non-clinical realm "Electrophysiology" refers to the study of electrical responses from any kind of cell or tissue and includes methods such as microelectrodes, patch clamp, voltage clamp, current clamp, etc. Clinical electrophysiology is only vaguely related to research electrophysiology. We should put this on top. Desoto10 (talk) 01:17, 6 June 2016 (UTC)
 * Yes, I agree that's all true. I'm beginning to think that the best approach might be to split this page into two separate pages. Maybe Electrophysiology (biophysics) and Electrophysiology (cardiology)? --Tryptofish (talk) 01:27, 6 June 2016 (UTC)
 * Well, we already have cardiac electrophysiology and electrocardiography. Maybe the best thing to do is make "Electrophysiology" the main article and describe what it is: detecting and recording electrical activity in living things. Then briefly describe the different modalities, such as extracellular, intracellular, etc., including volume recording such as ecg and send the readers off to separate articles that already exist.  Within the ecg article and reflected in the lead we would explain that ecg work is also called electrophysiology for historical reasons (I think).  Desoto10 (talk) 07:03, 10 June 2016 (UTC)
 * Thanks for that info; I didn't know about those existing pages. I just made Electrophysiology (cardiology) a redirect to Cardiac electrophysiology. That way, a reader who starts out by searching under "electrophysiology" will find the cardiac page more easily. I agree with you that the page here should reflect both the cardiology and the biophysics. But I would not want this page to become something that gets too close to just being a disambiguation page, so I feel that the biophysical/neurophys aspects should continue to have significant coverage here. And we could similarly have WP:Summary style treatments of cardiac electrophysiology and electrocardiography. I guess that means a little expansion of the cardiac topics here, with everything treated in something like summary style, but I don't want the descriptions to become too brief. --Tryptofish (talk) 18:37, 10 June 2016 (UTC)
 * Works for me.Desoto10 (talk) 01:20, 11 June 2016 (UTC)

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Clinical application frequency
Am a medical student going into neurology. Surprised to see that EMG is rated as being more frequent than EEG. In my limited experience, EEG is much more frequently used in the inpatient setting. I have rarely seen EMG performed, certainly not at the same frequency as EKG/ECG. Is this frequency supported by any citations? — Preceding unsigned comment added by 108.226.3.121 (talk) 05:15, 19 August 2019 (UTC)