Assignment Biopsychology MA (Applied Psychology)

 

METHODS OF VISUALIZING AND STIMULATING THE LIVING HUMAN BRAIN

INTRODUCTION

Remember Paul Broca (1824-1880), Patient Tan, Carl Wernicke (1848-1904), John Harlow (1819-1907), Phineas Gage (1823-1860)??  It was in mid-1800’s when Physician Paul Broca came across a 30-year-old French citizen named Louis Victor Leborgne, a patient who had lost his speech. His speaking ability was restricted to one single word “tan.” However, his other cognitive abilities like understanding instructions and words and intelligence were intact.

John Harlow’s rise to fame was his association as a physician with Phineas Gage. Gage who is also recognized as the “man who began neuro science.”

Carl Wernicke too had patients with language problems but quite different than the patients of Paul Broca. They had no problem in speaking but the words were disjointed and conveyed no meaning. Also, their understanding of instructions was severely restricted. They were unable to do even minor cognitive related tasks.

All the above cases have one common theme. The patients turned out to be bigger attraction and were thus instrumental in catapulting the concerned the Physicians to immortality. This, though, is still not the reason why these names have been thrown in. The special bond between these famous couples (Doctor-Patient) was steeped into a dark fact. All three Physicians had to wait for their patients to die to become aware of the disease and the path they were taking for the treatment. That sounds interesting. The patient must die to be diagnosed properly (autopsy) and treated. Just imagine a doctor waiting for the patient to die to know about his disease. This deathly wait extended to 12 years in case of Phineas Gage and patient Tan too lived 21 years since his condition was recognized. Autopsy was the only way to investigate brain.

Fortunately, such a dichotomy is not likely to take place with us, as there are enough techniques and machines to look inside the brain without a need to cut it open as was the case in olden times when technology did not offer this option.

Let us try and visualize (no pun intended) our journey of visualizing human living brain from the point when a doctor must wait for the patient to die to see the trouble spot in the brain to the present times when a three D image of the neural activity associated with any part of the brain can be captured or shown real time in color as if we are watching a film (movie) where everything comes alive.

VISUALISING THE HUMAN LIVING BRAIN

Prior to 1970s, Biopsychological research was handicapped by the inability to obtain images of the area of primary interest to the subject i.e. the living human brain. X-ray photos were in vogue but were suitable only for areas which had marked contrast in the ability to absorb X-rays. Like bones which absorb most of the X-ray and give a clear picture of fractured or damaged bone as the muscle areas that surround the bones are poor absorbers of X-rays. The brain structure is different in the sense there is not much contrast in in the areas inside the brain. The X-rays will therefore not be able to distinguish a brain part from the other.

This restriction resulted in a smart innovation called the ‘Contrast X-ray techniques.’ The technique involved injecting a substance in the target part of the body. The substance could have the quality of either absorbing more or less than the surrounding tissues which are not affected by the substance. It is like highlighting an interesting line in a book to create sharp contrast from other lines thus making it stand out. The technique was of limited use and could be employed only for limited number of cases, that too with lot of subjective interpretations.

X-Ray Computed Tomography (CT) is a computer assisted X-ray procedure used effectively to visualise the brain and other internal structures of the living body. Tomographic imaging consists of directing X-rays at the target area from multiple orientations and measuring the decrease in intensity along a series of linear paths. The process involves putting the patient into a large cylinder. On one side of the cylinder is an X-ray tube that projects an X-ray beam through the head to an X-ray detector mounted on the other side. The X-ray tube and detector automatically rotate around the head of the patient at one level of the brain, taking many individual X-ray photographs as they rotate. The information in each photo is combined by a computer to generate a CT scan of one horizontal section of the brain. In this manner scans of eight or nine horizontal brain sections are obtained from a patient. When combined, they provide a three-dimensional representation of the brain. The procedure revolutionized the study of neuroscience but posed the risk associated with exposure to radiation. Multiple shots of X-rays exposed human to more radiations. Such exposure can mean danger for certain special cases like pregnant ladies. It was found that radiation exposure was much more harmful for children than to adults.

Magnetic Resonance Imaging (MRI) was a technological jump in eliminating the harmful effects of radiation exposure. MRI is a type of diagnostic test that can create detailed images of the organs inside the body. It uses magnets and radio waves to produce images on a computer. It does not produce any harmful radiation like X-rays. The MRI machine is a large, cylindrical shaped (like CT scan capsule) that creates a strong magnetic field around the patient and sends pulses of radio waves from a scanner. The strong magnetic field created by the MRI scanner causes the atoms in our body to align in the same direction. Radio waves are then sent from the MRI machine to move these atoms out of the original place. As the radio waves are turned off, the atoms return to their original position and send back radio signals. These signals are received by a computer and converted into an image of the part of the body being examined. This image can be seen on a viewing mirror. MRI provides clearer images of the brain than does CT. It can also produce pictures in three dimensions.

Positron Emission tomography (PET) – PET was the first brain imaging technique to provide images of the brain activity (functional brain images). The PET scan uses a radioactive drug called a tracer into an artery of the neck that feeds the ipsilateral cerebral hemisphere (in case the brain is the target area). The drug injected is similar to glucose, which also happens to be the primary metabolic fuel of the brain. Now this drug is rapidly taken up by active cells thinking that it is glucose. However, unlike glucose, this drug cannot be metabolized and therefore it accumulates in active neurons. This accumulation of radioactive drugs in the area associated with active cells can be captured as an image. Thus, we can say that each PET scan is an image of the levels of radioactivity in various parts of one horizontal level of brain. As an example, if a PET scan is taken of a patient who engages in an activity like reading for about 30 seconds after injecting the radio active drug, the resulting scan will indicate the areas at that brain level that were most active during the 30 seconds of activity.

Functional MRI (fMRI)- fMRI is advanced version of MRI in the sense that it measures brain activity by detecting changes in blood flow. This allows the researcher to visualize which areas of the brain are most active during specific tasks or at rest. The functioning is based on the principle that when brain cells are active, they require more oxygen resulting in increased blood flow to these areas. The fMRI image shows which brain regions are active during a particular task or at rest, thereby providing insights into brain functioning. It is used to study and investigate as to how the  brain processes information, makes decisions and experiences emotions. Functional MRI has many advantages over PET scan. It can produce three dimensional images of activity over the entire brain with better spatial resolution.

Magnetoencephalography (MEG)- It is a non-invasive neuroimaging technique that measure the magnetic fields generated by neuronal activity in the brain. It’s major advantage over fMRI is its temporal resolution: it can record fast changes in neural activity.

Transcranial Magnetic Stimulation (TMS) This technique is used for temporarily activating or inhibiting specific regions. In effect, the magnetic stimulation temporarily turns off part of the brain while the effects of the disruption on cognition and behaviour are assessed. Used in research aimed at determining causation.

REFERENCES

1.   Pinel, J.P.J. (2018). Biopsychology (8^th edition).

2.   MRI Scan -what happens on You Tube