The following statements all refer to the human brain when mental activity is oc
ID: 2292025 • Letter: T
Question
The following statements all refer to the human brain when mental activity is occurring. Which statement is correct? o a. The electric currents in the brain can be detected outside the brain by detecting the magnetic fields they produce. b. The electric currents in the brain can be mapped by shaving a person's head and dropping iron filings on the head. C. The electric currents in the brain produce an aura that can be detected visually d. In order to detect electrie currents in the brain, you must open the skull and make direct electrical contact with the brain. e. The electric currents in the brain cannot be detected by any means.Explanation / Answer
correct ans for this que is (A)
Exp- measure electrical activity in the brain two ways are possiable
invasive—the ones where you go through the skull and stick things in the brain
Non-invasive—the ones where you measuring the electrical activity of the brain indirectly from outside of the skull.
Invasive-Most people don’t like sticking things into their brain, so usually when we measure electrical activity in humans, we use non-invasive techniques. But in neurosurgical settings we can directly record electrical activity from the human brain—for example, in cases of life-impairing epilepsy that cannot be treated with drugs, we may insert a grid of electrodes onto the surface of the brain to determine what part of the brain is generating the seizure (and then remove that area). Here is a good, albiet woefully dry (because doctors and scientists can even make neurosurgery boring),
These invasive electrophysiological (electro = electricity + physiology = biological function) recordings measure the voltage between the tip of the electrode and a reference electrode. If the tip of the electrode is inside or nearby a neuron, the electrode will measure the electrical activity of that cell. Depending on the impedance (a concept similar to resistance) of the electrode used, we can measure from individual neurons or the activity from a large group of neurons
Non-Invasive
The two most commonly used non-invasive measures of brain activity are functional Magnetic Resonance Imaging (fMRI) and electroencephalography (EEG), but other techniques such as Magnetoencephalography (MEG) and functional Near-Infrared Spectroscopy (fNIRS) are used as well. All of these techniques measure a sum of average activity, so they are best at detecting synchronous activity from large numbers of cells.
fMRI and fNIRs are actually not measuring electrical activity, but rather bloodflow and oxygen consumption (by measuring the oxygenation of hemoglobin). As electrical activity in the brain increases, so does blood flow and oxygen consumption, so these techniques can provide an indirect measure of brain activity, but have a low temporal resolution.
In contrast, EEG directly measures electrical activity from the skin outside of the skull, however these signals are very weak and dependent on the orientation of the cells in interest. It is best for viewing burst of synchronous activity MEG indirectly measures electric signals by measuring the magnetic fields produced by electric currents, and is more dependent on the orientation of cells primarily measuring the magnetic fields from tangential currents.
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