# Tag Info

## Hot answers tagged electrophysiology

13

Short answer Brain waves are not electromagnetic waves. Long answer Measured brain activity, as you already mentioned, is the result of individual neurons firing. The activity exists, in fact, of two parts. First of all, there are the action potentials (APs). APs are current flow within a neuron from one end to the other. The magnitude of these APs (and ...

12

The OpenEEG project has some information for building your own EEG system. Instructables has a "simple" EEG circuit you can build. Note that this is going to be somewhat costly and time consuming because you are dealing with tiny voltages and high impedances. OpenBCI has some hardware for sale (still expensive but not as bad as research-grade equipment) and ...

11

Short answer Brainwaves are typically associated with the electroencephalogram, which is a signal mainly composed of potential differences generated in the superficial layers of the brain. Potential differences represent electric fields and do not represent electromagnetic (EM) radiation. EM radiation is build up of packets of energy (photons). EM radiation ...

6

If "brain waves" produce a time-varying electric potential as shown on the EEG, then as far as I know electromagnetic waves are present. I was taught that you cannot have a time varying electric potential without creating an electromagnetic wave. You can try browsing wiki explanation https://en.wikipedia.org/wiki/Maxwell%27s_equations, but the main idea is ...

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Confocal Fluorescence Microscopy and 2-photon Fluorescence Microscopy are two techniques commonly used in neuroscience to image only one plane of the sample and thus increase resolution. However, how they achieve this technically is distinct. Confocal (confocal laser scanning microscopy (CLSM)) In confocal microscopy the sample is scanned with a laser in ...

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As in the ideal gas law, the universal gas constant allows for calculation of amount of energy associated with a certain group of molecules (see https://en.wikipedia.org/wiki/Gas_constant). As the Nernst equation compares the "osmotic pressure" to "electrical pressure", the universal gas constant is needed to convert amount of an ion on the two sides of a ...

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If there is literature that you are building off of or comparing your approach to, I would look in their papers to see what values they used and use the same. This is the standard approach, as it yields easily comparable experimental results. If you are just looking for some ballpark numbers for less formal research, these guys used 1 mΩ, these guys did the ...

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I found that dF/F0 stands for the relative difference in fluorescence at a certain wavelength.

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The P300 wave is a positive deflection in the human event-related potential (ERP). A common experiment in which it is analyzed is the "oddball" paradigm, where a subject detects an occasional target stimulus in a regular train of standard stimuli. The P300 wave only occurs if the subject is actively engaged in the task of detecting the targets and its ...

5

I take it you want to use eye movements for data input (rather than reading people's thoughts, which would be silly to consider). It's not the greatest idea, efficiency wise, but may have its strengths in terms of convenience. From a fairly recent (2014) review of eye based HCI: It should be noted, though, that gaze control of WIMP is noticeably slower ...

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I see your confusion is caused by $u_{rest}$. Indeed that diagram is somewhat confusing because $u_{rest}$ is not the main source relative to which to consider the topology of the circuit. The main source is actually a current source designated by $I(t)$ in your diagram. With respect to that source R and C are in parallel. If that's not convincing enough, ...

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The general biological term for this kind of mechanism is synaptic plasticity. Synapses are the biological structure that allow neurons to communicate via the exchange of neurotransmitters. The strength of the synapse (the effectiveness of the link between the neurons) can be modified over time. One important kind of modification is long-term potentiation, ...

4

The main cell of the brain is the neuron. The neuron has a semipermeable membrane that under specific circumstances lets potassium through. Another common cell is the glia cell, which only has potassium channels. Potassium, K+, has a positive charge and it can pass across the membrane at specific channels, depending on their state (open/closed). The channels ...

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Short answer The peak polarity of an EEG is arbitrary. Background Positive and negative in an EEG measure is arbitrary. If you measure the EEG between two electrodes and you flip the wires, the polarity of the signal will reverse too. Only when standard EEG montages are used, in which the active and reference electrodes are strictly defined, then signal ...

3

Short answer Electrophysiological responses in general often come in waveforms. These are characterized by a number of peaks and troughs. Dependent on the specific response, arbitrary naming conventions are used. Generally something along the lines of P1 (positive peak #1), N1 (negative peak #1), P2 etc. Sometimes latencies are used as a subscript too to ...

3

Ohm's law famously states V=IR, the voltage change (V) across a resistor generated by a current (I) equals the current multiplied by the resistance (R). The resistor in this case is the cell membrane. When an experimenter injects a known amount of current through an electrode, the voltage change that occurs is related to that current by the resistance of ...

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Short answer Mostly Cl- is disregarded in calculations of the resting membrane potential and action potential voltage changes, because it is less important for the neural membrane characteristics than Na+ and K+. Background In some neurons Cl- is not actively transported. In terms of the resting membrane potential, Cl- hence settles its gradient passively ...

3

In normal neurons, Chloride's reversal potential is near the resting potential for the neuron and also happens to be near the leak conductance reversal potential for the neuron. While not exactly the same these three are sometimes confused. The difference between these three reversal potentials is subtle. Chloride Reversal Potential: is the potential ...

3

This seems to be a rather painful terminology issue. "Pooling" is used in statistics to describe combining data / different sources of information in a single model. It's of particular interest in hierarchical modelling approaches (e.g. mixed-effects modelling), and partial pooling -- broadly, the sharing of information between groups in a model without ...

3

Autocorrelation is calculated between the spikes-histogram and itself. The experiment is carried out while the activity of a specific neuron is recorded. Histogram - An animal runs in a circular arena which we divide into multiple squared bins, whenever the cell fires (i.e. generate an action potential) 1 counter is added to the location (the bin) in ...

3

I wouldn't know why multi-site cortical extracellular recordings would not be feasible? What would the practical experimental or technical limitation be in your opinion? As long as you have a multichannel amplifier suitable for extracellular recording and you consider the choice between using a common reference, i.e., monopolar recordings (Ludwig et al., ...

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Medscape defines diffuse as generalized, in the context of EEG. Generalized means activity recorded across large portions of the cortex. This opposes focal patterns, that occur locally. In turn this is reflected in generalized epilepsy and focal epilepsy. Generalized epilepsias are characterized by gross paroxysmal activity across the cortex, associated with ...

3

For auditory brain stem responses (ABRs) the click rate can be really high, as the auditory system is exceptionally fast, in the order of tens of stimuli per second (e.g., Rodriguez et al (2010. This will still yield a good ABR. At around 40 ms, the transient ABR shifts toward a steady state response, in which peaks of the previous ABR start to overlap with ...

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The recorded signal are spike responses (action potentials) (p.2 Method section), the different states are spike rates (p.4), and the calculated correlation is determined between spike rates and maze coordinates (p.5).

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Short answer Mimicking action potentials is possible, but not the most practical approach. Background In general, stimulation of neural tissues occurs through placing electrodes in the vicinity of the target tissue and applying short current pulses, e.g. think cardiac pace makers, cochlear implants, retinal implants (Rao & Chiao, 2015), as well as ...

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The Utah array is a multi-electrode array for intracortical recordings. In one of many publications on this device, the authors show some sample traces that reveal amplitudes generally between 5 and 40 microVolts. However, measured voltage will depend on the vigilance state of the brain, recording area, time on the millisecond scale, time on the macro scale (...

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The ideal impedance of any electrode aimed at recording low-amplitude neural signals (barred suction glass-pipette electrodes for patch clamping) is simply: as low as possible. In case of tetrodes, i.e., electrodes consisting of a bundle of four microwires that can record from multiple neurons simultaneously in the brain of freely moving animal, they are ...

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Short answer I haven't been able to find studies on EEG correlates of antidepressant discontinuation syndrome. Background 'Brain zap' is a colloquial term for antidepressant discontinuation syndrome. Note that the sensations you mention in the arms, neck and lips etc are likely caused by central effects (i.e., in the brain) that evoke sensory perceptions ...

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The resistor is the conductance of the ion channels in the membrane. The capacitor is the membrane itself, which acts as a capacitor (a non-conductive center sandwiched between electrically active materials). There are two ways for "current" to flow between the outside and inside of the cell. One is through ion channels (the resistor), and one is for ...

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For the unipolar configuration, why can't we just use Earth ground as our reference instead of having a reference electrode or performing an average of measurements on all the electrodes? The ground has a different function than the reference. The reference is the electrode that the voltage is recorded against; a voltage is a potential difference so you ...

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