I would like to re-post a question originally asked on Twitter by @Cian O'Donnell @cian_neuro on May 10.
The original question was why MRI is considered an imaging modality while EEG isn't.
I think this question should become a topic of serious scientific discourse to clarify why EEG might or might not be considered an imaging method.
IMO EEG clearly is an imaging method as both magnetic resonance imaging (tomography) and electroencephalography graphically depict different dimensions of brain structure and function. Eventually, neuroscience has to overcome scale chauvinism and allow focusing on the synergistic use of different imaging methods (from single cell to macroscopic hemodynamic and electrical brain activtiy) to gain a better understanding of brain structure and function. Only then will we be able to understand the brain and thus it should be our task to do so as scientists.
Looking forward to answers and lively discussions to calrify what constitutes an imaging method.
I think that tomography is an imaging technique and electroencephalography is not because the former provides direct information regarding structure and its location while the latter provides information only about functional output of some area. And moreover, the area in question is not well defined either as on different people information will travel slightly different distances. Hence, no space/shape/form/size info is provided by EEG.
However, I think this does not dismiss EEG as an important tool for gathering info on a particular topic, dedicated to functional outputs
Thanks Klaus and @Cian O'Donnell for bringing up this topic. This is rather a controversial but quite fascinating discussion.
Well, I completely concur with the second part of your opinion, stating that neurosciences like many other fields of multidisciplinary studies should lose the myopic or biased view and get rid of fetters of what you call it chauvinism! This is still bothering those who are trying to introduce new grounds in neurosciences or are willing to expand its circle of conception.
Regarding the dispute over what’s been considered imaging and what’s not, both structural and functional imaging are approaches to acquire and interpret the data of modalities, and this cannot be considered as a criterion to demarcate what is imaging and what’s not.
As we all know, we have functional, structural, pharmacological and neurochemical approaches to imaging and this list can go on.
I think micro-scale approaches like calcium imaging as well as macro-scale modalities such as MRI, fMRI, PET, CT, SPECT, even x-ray are celebrated to have the very characteristics of imaging tools because of a series of assumptions:
1. Although I think that scientific terminology regarding the imaging techniques are getting outdated a bit in some aspects, and may need revision, the mentioned modalities truly act like cameras, enabling us to almost directly (forthright or after applying certain transformations, calculations, pre- and postprocessing steps) see what is happening in the brain itself and the nervous system, no matter what approach we aim to (structure or function). If not a real time, live imaging, we will have our processed results overlaid on brain regions as if it is a single shot, not a set of time series, waves and rendering.
2. This is a very popular and general nomenclature accessible to all people, not just scientists! Those who take a glimpse at an MRI or PET or x-ray call it as an image of that tissue, namely the brain. But imagine if there is a unanimous name for what an EEG would show! Show epileptic wave discharge in temporal lobe to an epileptic and ask him or her what is that?! Expect anything but “an image”!
3. I assume that you underscored “-graphy” as a suffix which can adequately fulfill the goal of imaging. Whereas, in my opinion “-graphy” was firstly coined as in the meaning of “writing” in protoscientific era, and then traversed to “imaging”. It is a mere fruit of scientific terminology which may need revision at some point (in order to not to lose the function of the word pushing it to be vacuous).
4. I agree that remarkable temporal resolution of EEG which can be comparable to MEG is a good measure for millisecond brain activity, but they do have low spatial resolution and this can be a possible criterion to prioritize the list of neuroimaging methods in favor of other modalities like MRI.
5. There is still a line between imaging and electrophysiology, no matter how their data are intertwined and may complement each other. We all know that ERP for instance is a common ground and a single concept in both electrophysiology and imaging. But the interpretation of the results of an ERP in EEG is different with that of the MRI because of the disparate acquisition technique and physics behind each of these modalities. Such nuances even if theoretically congruent can lead to different interpretations and potentially different functions (but ironically supplemental!).
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