Experimental Brain Research

Learn the new techniques in experimental brain research which are helping scientists to come to terms with how the brain works.

How are Scientists Studying the Brain?

The human brain is a very complex organ. To date, even the most complex, sophisticated computer cannot "˜simulate' this organ, which we, as humans, take for granted. Scientists are constantly seeking new ways by which to study how the brain works and how it is affected by external influences. Brain-behavior relationships have been traditionally studied using three basic approaches:

1. Use of experimental animals

2. Use of human subjects behaving "˜normally'

3. Use of human subjects who have brain damage in specific regions

Various experimental methods have been used to study the functions of specific brain areas. Typically combinations of techniques are used in order to shed light on a specific brain-behavior relationship (e.g. language processing).

A. Lesioning and Surgical Ablation (typically performed on laboratory animals).

~ Lesioning - destroying brain tissue in the specific region of interest via electricity, cold/heat, or with the use of chemicals.

~ Surgical ablation - a specific area of the brain is surgically removed and the resulting behavior studied.

B. Stimulation Method (again performed on lab. animals but has also been performed on humans in the 1950s).

~ the region of interest is stimulated - electrically (via implanted electrodes) or chemically (via an inserted cannula which delivers specific chemicals e.g. opiates to the said region).

C. Electrical Recording Techniques.

~ Scalp electrical recordings are an excellent technique whereby the normally functioning human brain can be studied non-invasively, i.e. they cause no harm to the subject.



Hans Berger (1929) discovered that spontaneous electrical activity could be picked up from the scalp surface. This activity was in the order of microvolts and was referred to as the Electroencephalogram or EEG. It can give us insight into the subjects' level of consciousness (e.g. drowsy or alert) or whether damage is apparent (as in the case of epilepsy).

~ in the 1960s sophistication of technical developments meant that the EEG could be studied in response (time-locked) to specific stimuli (e.g. a simple tone) and averaged over a number of stimulus trials to produce the Event-Related Brain Potential (ERP).

ERPs to one type of stimulus (e.g. slides of spiders - phobic) could then be compared to other types of stimuli (e.g. slides of landscapes) and the resulting differences in brain-response measured. This type of research has been used extensively in the past 40 or so years and has been instrumental in showing the time-course of stimulus processing. Possibly the most important discovery has been that the human brain often processes stimuli in our environments long before an overt response is required.

D. New Scanning Techniques.

~ the principal problem with scalp recordings soon became apparent - they were useful for mapping the timing of processing a stimulus but were poor for their spatial resolution - i.e. which specific region of the brain was responsible for a given cognitive, emotional or behavioral response. New techniques were developed to address this question:

~ CAT scans (Computerized Axial Tomography) - developed by Allan Cormack and Godfrey Hounsfield who were awarded the 1979 Nobel Prize for medicine for their pioneering work. This technique uses X-Rays, but is 100x more sensitive than standard X-Ray procedures. Can detect brain damage in the "˜living' brain and has also been used to highlight local changes in cerebral blood flow (a measure of underlying neuronal activity) as human subjects perform a task.

~ PET scans (Positron Emission Tomography) - developed by Louis Sokoloff and his colleagues in 1977. Subjects are injected with very small doses of radioactive deoxyglucose, and the principal behind this technique is that if brain cells (neurons) are more active they will consume more of the radioactive glucose, therefore the rate/absorption of deoxyglucose reflects neuronal activity.

PET scans the absorption of radioactivity from outside the scalp and the data is fed to a computer, which maps the activity onto a color-coded brain map, which can be observed on a monitor or as a printout. More activity is colored red, least - blue. Sophisticated computer programs allow researchers to observe "˜slices' of the brain and therefore observe deeper brain structures like the hippocampal formation which ERP techniques are not capable of doing.

~ MRI scans (Magnetic Resonance Imaging) - first developed by Shulman, 1983. This technique works on the principal of very strong magnetic fields being applied to the outside of the head which must be kept still and is therefore generally encased in a brace. Allows for very clear pictures of the brain (again the programs can provide "˜slices' - see above), and can pinpoint any damage extremely quickly and accurately.

A spin-off of this technique - fMRI (Functional Magnetic Resonance Imaging) uses the principals of MRI but can also measure brain activity to specific stimuli too - thus now we have a technique which allows for terrific spatial AND temporal resolution, thereby allowing researchers to pinpoint where activity to specific environmental cues are occurring in the brain, and their time-course.

Conclusion

This field will only become more and more sophisticated with time. Currently the machines used to measure human brain activity "˜in situ' are expensive, and typically housed in hospitals and universities. The future will see a drop in costs, a further sophistication of techniques and the day will come when scientists can observe specific brain cells one at a time as they "˜function' in the living human.

Gone will be the need to implant electrodes into brain tissue and gone will be the complications which can arise when foreign substances (e.g. electrodes and chemicals) are introduced into the delicate brain tissue. Our understanding of how the brain functions can only be useful - in the treatment of brain diseases (like Alzheimer's, Stroke, Epilepsy, Parkinson's etc), and in ultimately preventing or curing such illnesses.

© High Speed Ventures 2011