Brain Imaging Techniques: Limitations

Yashant Sharma

We have read how brain imaging techniques have a crucial role in helping mental health professionals. Most commonly read techniques by prospective students are fMRI’s, PET or Positron Emission Tomography, Electroencephalography (EEG), Optical Imaging, and Diffusion Tensor Imaging etc. MRi’s are the most widely used technique in studying the brain. Since Brin is made up of millions of neurons, and each of these neurons communicate with each other using electrical signals, it Creates a magnetic field which is measured in Teslas. The Magnetic Resonance Imaging (MRI) relies on this principle and forms an image of the brain using the data and helps scientists and doctors understand the patient’s brain, in both longitudinal and transverse section which the antenna in the scanner helps generate. The question thus arises, that what happens when a person is not capable of producing enough magnetic field, how would MRI’s help then? Similarly, studies (D'Esposito, Zarahn, Aguirre, and Rypma, 1999) show most of the imaging techniques are based on indirect measures of blood flow response properties, though there are various physical structures like weakening or capillaries, or reduction of grey matter in older people, which may directly or indirectly influence physiological properties and even in some cases may not adhere to the fundamental on which these techniques are based on, take for example a person whose brain is not responding at all? Comas (“Is A Brain Dead Person Actually Dead?", 2019) for instance, when brain is at its minimum interaction level, with no stem reflexes. 

Studies also claim that Vascular system also differ in young adults versus old people. If a patient is exhibiting symptoms hypertension eventually, their brain imaging won’t be as factual as someone who is not, all these differences in arteries and capillaries caused by aging, can affect the end product of our image, and may be misleading. Studies show thatIt is important to remember that neuroimaging techniques are based on indirect measures of blood flow response properties. There are many physical and physiological differences between the images obtained from a young adult in comparison to an old patient. Imaging techniques like PET or positron Emission Tomography are also widely talked about, but despite giving such a clear resolution not all patients can undergo this process, like for instance an infant. Also, the very thought of a radio-active material being injected inside one’s body, makes the patient vulnerable to even opt for something so undesirable. fMRI’s or the Functional magnetic resonance imaging relies on the blood oxygen consumption pattern of the brain, although the principle of functioning remains the same to that of an MRI. MRI measures differences in signal intensity between grey matter, white matter and CSF, and hence, it makes it difficult to retrieve the clear picture of an old person’s brain, since there is a loss of grey and white matter due to aging. On the other hand, fMRI’s measures intensity of haemoglobin, that carries oxygen to the blood. fMRI are an indirect measure of neural activities, to which some neuroscientists, also disagree because it is a delayed version of the actual Brain processing. Doctors who want to study the real time brain activities find a delay in the fMRI , since it is only capable of working at a speed o 1 second, where as the brain is capable of generating an impulse in less than 10 milliseconds, and hence, it is approximately 1000 Times slower (Stephan Schleim, "Understanding the possibilities and limitations of brain imaging", 2009).  fMRI also gives a very bad temporal resolution. Another concern with fMRI techniques that Stephan claims is that fMRI, gives connections between changes in the neural processing and blood flow, but they are still not well understood, and hence it still requires advance tests to to understand this complex machine of ours,- The Brain. Studies show that cognitive neuroscience experiments have proved that younger individuals have different activation patterns in the brain than older participants, and older individuals, show conspicuous bilateral activation under conditions that produce highly lateralised activity in younger adults(Reuter-Lorenz, 2002)

We might have had the most advanced machines to help us decode the way our brain works, but most of these techniques have their own sets of limitations, and since the patient doesn’t come from a factory that manufactures exactly the same models of iPad like creatures, I thus argue that since each person- including people with intellectual disabilities, different cognitive mappings, different brain shortcuts, socio-economic backgrounds, different dietary and nutritional intake; and even age-group, should not be assessed on a pre-designed softwares Since we as psychologists know that all these factors can have psychosomatic or notable physiological effects on the way processing happens.