Recently I’ve outlined the history of neuroscience as a discipline, and I’ve brought you right up to the modern day. Now it’s time to focus on the techniques we currently use and how these are still developing. In modern times, there are a great deal of techniques used to visualise brains and to better understand human neuroscience.
The first, and perhaps simplest of these techniques is cell recording. This involves recording the electrical activity of neurons. From doing this, we can tell how neurons work in greater detail, we are able to tell when a neuron is active or not, and we can see differences in the electrical potentials of different neurons. The electrical activity in some animals may be different, since they have neurons which are different in structure. Cell recording enables us to see a very detailed account of the neuron activity over time, but not over a very large area. We can only look at one cell at a time with this method, and so it cannot give us very much information about the spatial mapping of brain functions.
EEGs or electroencephalograms are the next step up in this technology, allowing the detection of electrical potentials in large groups of neurons. Placing electrodes on an individual’s scalp, the electrical potential across the whole brain can be measured. ERPs (event related potentials) are detected, which relate to the amount of brain activity occurring at any one particular moment. Unfortunately, though this allows us to test the whole head at once, it still only gives us very basic spatial measurement and so does not allow us to distinguish between different brain areas. Magnetoencephalography measures ERPs as well, but does so using magnetic fields.
TMS (Transcranial Magnetic Stimulation) is a useful method allowing us to momentarily switch off a part of the brain. By doing this, we can see what changes in functioning occur as a result. Once a change in functioning is visible, it will be clear that the area of the brain that has been switched off is responsible for that function. TMS causes no long term damage to the brain and so is revolutionary, meaning that we no longer need to examine real brain lesions as we can create ‘virtual’ ones. The biggest problem with this technique is that it can only reach the surface layers of the brain, and so it is not useful for studying deeper brain areas.
tDCS (transcranial direct-current stimulation) is almost the opposite of TMS, and involves delivering low-level electrical currents to certain areas across the scalp of the brain to see what the effect is. It can therefore be used in a very similar way to the earlier technique. The different types of stimulation either increase or decrease the excitability of the neurones.
While these techniques are all very useful in understanding the brain, they tend to either give a view based purely on change over time such as EEGs, or based purely on geography of the brain such as TMS or MRI (not discussed here). What scientists are recently developing and only just using are functional techniques, which allow us to see the entire geography of the brain, and how this changes over time. We’ll learn more about these in the next article.
Image from: http://www.magstim.com/img/imagecache/2/3/3/d/cache_233df968da86a6d9cdf69ec7be98e3e6.png
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