Slide 2 Notes
The human race has come a long way in our understanding of the brain since the time of lobotomies and blood-letting. We can now use computers to digitally capture a picture of the brain or we can experiment with animals in various ways to better understand our own brain functions. Furthermore, there are five basic ways that we study the brain these days: stereotaxic surgery, conventional lesion, stimulation, and recording methods; pharmacological methods, brain imaging and genetic engineering (Pinel, 2007). Lets take a good look at each of these methods one at a time…
Slide 3 Notes
I saw Fern Gully for the first time when it was released in 1992. Batty, one of the main characters, was the product of human experiments gone wrong. He had an electrode protruding from his head and wires in his body. In the movie the bat is actually able to pick up radio signals from the visible electrode. This is of course not how stereotaxic surgery works. Furthermore, the point of stereotaxic surgery is to implant a device in the brain of a subject, almost always an animal, that can measure neural activity or be used to stimulate neural activity. A stereotaxic atlas is used to find the precise position where the device should be implanted, and the stereotaxic instrument is used to implant the device. Above is a classic example of stereotaxic surgery: inserting an electrode into a rat’s amygdala. As you can see the directions for insertion of a device are very precise, measured down to the millimeter. This is of course a very invasive procedure and is generally reserved for animal research. Now let’s turn to an even more invasive set of procedures…lesion, stimulation, and recording methods….
Slide 4 Notes
The most conventional and invasive methods of brain study are the lesion, stimulation, and recording methods. A lesion is used in the study of the brain by destroying an area of the brain and then observing the effects to the subject’s behavior. There are three main methods of destroying an area of the brain. The first is to simple lower a needle which has been retrofitted with an internal knife down into the subject’s brain and then severing the section of the brain of interest without damaging much surrounding tissue. The second is to lower an electrode into the brain and pass sufficient electrical current through a section of the brain in an attempt to lesion that section. The last is to simply use a suction hose to suck away the surface matter of the brain. As you can see all of these procedures are extremely invasive and reserved, except in extreme cases, for animal research. Next, is the stimulation method which sort of mirrors stereotaxic surgery except that the electrode is used exclusively to stimulate certain areas in order to ascertain their function. One final conventional method is recording, which utilizes an implanted electrode in order to measure brain activity either in one unit or multiple-unit recordings. However, one form of recording, electroencephalographic recording or EEG, is used to place electrodes on the surface of the skull to measure brain activity. This type of recording is less invasive but less telling at the same time, because the EEG picks up so many electrical signals from the brain that it is really only used to measure overall brain activity. Next is a much less invasive method…pharmacological methods…
Slide 5 Notes
Unlike some of the other methods discussed so far pharmacological methods can be widely administered on humans and non-humans alike. This type of research employs two different types of drugs that affect neurotransmitters: agonists and antagonists. Agonists increase the effects of a particular neurotransmitter, and antagonists decrease the affects of a particular neurotransmitter. Listed above are the seven steps in neurotransmitter action that agonists and antagonists can affect. For instance, cocaine is a highly addictive catecholamine agonist that “…increases the activity of both dopamine and norepinephrine by blocking their re-uptake from the synapse into the presynaptic button” (Pinel, 2007, 86). On the other hand, curare works in an entire different capacity. This is an extract derived from a type of woody vine which can cause paralysis and eventually death by blocking receptors at neuromuscular junctions. Next we explore some well-known acronyms such as CT and MRI….
Slide 6 Notes
Up until the 1970’s brain imaging was halted by the limitations of the x-ray. A standard x-ray can not readily distinguish between the different sections of the brain, because they are not of sufficiently different density. However, the technique of contrast x-rays was developed which uses injected substances to bring out the contrast in certain areas of the brain. One particular technique, the cerebral angiography, is used to map the 2-d circulatory system in the brain. These type of scans are not used to map the brain but rather to identity areas of vascular damage or the presence of a tumor. Next is an x-ray computed tomography (CT), which utilizes many x-ray scans to map a 3-d model of a human brain. Further up the ladder is magnetic resonance imaging (MRI), which makes use of a magnetic field and the waves hydrogen atoms emit in order to draw a color coordinated map of the brain. This type of scan is more useful than a CT scan because it gives doctors the ability to detect differences in spatial location. One of the most telling methods of brain imaging is positron emission tomography (PET). This type of scan exploits radioactive 2-deoxyglucose (2-DG) in order to map brain activity rather than brain structure. Finally a cross between the MRI and the PET scan is the functional MRI (fMRI). This type of scan detects oxygen flow of blood in the brain. This type of MRI can be used to map both brain structure and brain activity. Now to the last method of studying the brain…genetic engineering….
Slide 7 Notes
There are two main sections of genetic engineering when it comes to brain studies: gene knockout techniques and gene replacement techniques. Gene knockout is just what is sounds like. A subject, always an animal subject, is bioengineered without a particular gene, and then the resulting behavioral effects are observed. On the other hand, gene replacement is where a gene is replaced with another gene such as a human pathological gene. Mice that have had another species’ genetic material injected into its own is call a transgenic mouse. Another adaptation of gene replacement is to replace a known gene with an identical gene that has an additional couple of bases which can be used as a switch. This type of gene replacement can be used to activate or suppress a gene and then observe its affects on the subject’s behavior.
Slide 8 Notes
In conclusion, the various methods of brain studies can be leveraged in an attempt to better understand the brain and its function in the human body. Some of the methods are reserved for specific uses and narrow applications while others can be used for a wide variety of purposes. In the end, all of these methods help us better comprehend the structure and function of the organ which best differentiates us from our evolutionary ancestors: the brain.
Pinel, J.J. (2007). Basics of biopsychology. Boston, MA: Allyn & Bacon.