INTRODUCTION Gaining insight to the brain is at the very core of understanding what it is that makes us human, but as Watson (1996, p. 544) points out, "Bridging the gap between understanding the brain and understanding themind and behaviour continues to elude us." Throughout history many methods to study the brain have developed. Although, with all of the advances someof the methods have quickly been dropped while others still remain accepted and are still used. Some techniques such as the autopsy, which looks afterdeath at the brain directly, have been around for many years and are still major techniques used today. Other techniques came along which attemptedto make a connection between the living brain and behavior. One of these was phrenology. The idea behind phrenology was that certain behavioralcharacteristics of people could be linked to the bumps and depressions on their skulls (Morse, 1997). Phrenology was quickly disproved by thescientific community, and today, when people think of phrenology, it is laughed at. Now, like phrenology attempted there are brain imaging techniques which are used to study the living brain. Some of the techniques that are in use today are computed tomography (CT), positron emission tomography (PET), and magnetic resonance imaging (MRI). Brainimaging techniques can provide pictures that in some ways can be linked to the functioning of the brain. However, it is possible that with time, science may prove these imaging techniques provide no more insight than phrenology did. People might be laughing at these techniques a hundred years down the road like phrenology is laughed at today.
Phrenology To understand how the imaging techniques which are currently in use might be like phrenology a basic background in to this pseudo science is needed. Phrenology was, for a brief period of time, accepted as a method of linking the brain and behavior. Obviously, phrenology is not accepted in the scientific community today. Phrenology was developed by a German born physician, Franz-Josef Gall. Gall first lectured on the topic in 1796 (Spitz, 1998). Phrenology attempted to look at the brain in an indirect manner. The belief of phrenology is that a person`s personality and abilities can be deduced from the sizes and shapes of various bumps and depressions on the skull (Morse, 1997). Specifically, the brain could be separated into 37 different faculties at different distinct locations in the brain (Bank, 1996). Today, it seems obvious that studying bumps on the head and inferring things about the brain under it seems silly. This would mean that the soft tissue of the brain would have, in some way, shaped the hard bone of the skull. However, the impact that this idea had on the 19th century was tremendous. According to Morse (1997) it was an extreme hunger for insight into the human mind that spun phrenology into acceptance.Phrenology found its way into everything, from employers to women`s hairstyles, and all of this was happening without in-depth scientific research on phrenology. When research began the flaws of phrenology immediately began to show, and their findings spread from the scientific community to the general public. People soon began to realize theerroneous assumptions of this science called phrenology. For all that it was not, phrenology did provide psychology with some insights into studying the brain. Most importantly it began to get peoplethinking about the living brain. This is an idea which is still worked with today. The scientific community showed that the assumptions of phrenology were incorrect by the end of the 19th century. According to Morse (1997) there was not a thread of scientific authority behind phrenology by the beginning of the 20th century. However, people still had hunger to acquire more knowledge of the link between the brain and behavior. Today, there are techniques like MRI and PET to study the livingbrain. These technologies are driven by that same hunger for insight into the human brain. Like phrenology imaging techniques use indirect orsecondary techniques to look at the living brain. What is the difference between phrenology and the imaging techniques in use today? What are thesepictures generated by them really showing? Possibly new technologies will come along that prove the imaging techniques in use today are not showingthe link between behavior and the brain which they are believed to be showing. In other words, have these great imaging techniques truly brought more insight into the functioning of the brain or are they creatingcolorful pictures which are comparable to the bumps of phrenology?
OLDER METHODS OF STUDYING THE BRAIN Phrenology is not the only method that has been developed to study the brain. Fortunately, there are many other techniques which are more scientifically based. Before looking at the new technologies used to look at the brain it is necessary to have an understanding of the techniques which provided the base knowledge for the new techniques.Autopsies For many years people have been studying the human body after death, a technique known as the autopsy. This was one of the first ways in which the human brain was studied, and for many years was the only way to look at the human brain. Autopsies are still used extensively today for studying the brain, but this can only take place after someone dies.Autopsies look directly at the brain unlike phrenology which attempts to infer aspects of the brain through secondary methods. Studying the brain in this context can tell us many things. For example, if someone suffered a brain injuring blow to the head during their lifetime, which had noticeable effects, an autopsy could pinpoint the damage. After the autopsy was done, a correlation, not a cause, could be drawn between the changed behavior or personality and the location of the damage to the brain. Two areas where this is used quite often today are in the study of Alzheimer`s Disease and alcoholism. Autopsies are currently the onlydiagnostic technique for Alzheimer`s Disease. There is no way to tell if a living brain has the disease because the sulci and gyri must be looked atfor a correct diagnosis. Currently the only effective way to do this is through autopsy. Moore (1995) writes about a study which involves this very issue. It was done to look at the prevalence of Alzheimer`s in later life, but to confirm whether or not the patients had the disease they had to wait until the participants died to diagnose them correctly. One hopeof the scientific community is that advances in the techniques used in studying the brain will create methods which are capable of diagnosing thedisease in the living. This would create the ability to treat patients properly. Alcoholism is another type of disease which is heavily studied with the use of autopsies. Alcohol, like any other drug, has obvious effects on the brain when it is in a person`s system, but it also has many long term effects. In the article "Heavy Drinking" (1994) it is reported that autopsies have shown that the brains of severe alcoholics can shrink. Theeffect alcoholism has on the brain is also a hot topic with many of the newer methods of studying the brain.Studying the Brain under the Microscope Observing the brain with the naked eye is a great way to look at the brain on a large scale, but to truly gain an understanding of the brain scientists needed something on a smaller scale to look at. This first became possible with the invention of the microscope. On the large scale things such as size, shape, and position can be studied, but the smallerscale opens up a whole new world. In order to study the brain on this small scale, the brain must be carefully prepared and slides of the tissue must me made (Gardner, 1968). This can become quite complicated.Obviously the tissue will have to be dead, but it needs to resemble living tissue as much as possible. To accomplish this the tissue is placed in a chemical which simultaneously kills and preserves the cells. Then the water must be removed from the tissue, and this is done with alcohol. The tissue is then in a hardened state and it can be sliced very thin. Most ofthe brain tissue when left alone looks just like all of the tissue around it. Because of this the tissue must be stained. There are a variety of different stains that are used. Which stain is used in each particular case is determined by which structures need to be studied. The prepared tissue is then encased in a glass slide for protection. The development ofthe electron microscope only furthered the amount of information that could be gathered through this method (Gardner, 1968).
Electroencephalograph (EEG) The autopsy and the use of microscopes are still widely in use today. However, it involves the studying of dead tissue. This approach is essential to gaining an understanding of the human brain, but it is limited in the fact that it is hard to draw conclusions between the brain and behavior without looking at the living brain. To understand how thebrain controls behavior there must be an understanding of how and where cognitive, sensory, and motor performance tasks are handled in the brain (Horwitz, 1994). In order to do this the brain must be studied as it is performing these functions, and that simply can not be done by looking at the brain after death. The basic function of an autopsy is to help bringabout an understanding of the physical make up of the brain and it`s many structures. This comes with many limitations, and because of these limitations other techniques have developed which revolve around the living brain. One of these is the EEG. The EEG is based on studying the brain through the action potential of the neurons in the brain. It is stillwidely in use today. The idea for the EEG has roots back in the 18th century with the relationship between electric shock and living organisms. It was seen thatelectrical stimulation could produce large effects, but advances towards actually studying the brain did not evolve until the technologies were available to record the small electrical potentials in the brain (Walter, 1953). By the late 19th century some of those techniques were becoming available. It was a man by the name of Richard Caton working in Liverpoolwho first recorded electrical activity in the brain. Using the technologies of the day he made recordings from the exposed surfaces of living rabbit and monkey brains (Empson, 1986). The modern machines used are far different from those used in the late 19th and early 20th centuries, but the basic ideas remain the same.What the EEG measures is essentially electricity. Electricity is found in certain waveforms depending on the intensity of the specific charge. Specifically, what the EEG is measuring is the electricity in the brain which is coming from the action potentials of the neurons in the brain. When there are more action potentials there will be more positive voltageand the EEG output will peak, and when there are less action potentials, and consequently lower voltage, the output will be lower (Milnarich, 1958). The theory of what the levels of voltage in the brain mean toward the study of behavior is that when certain areas of the brain are functioning the neurons of that area are firing at greater rates. If the neurons are firing at greater rates, then there will be more positive voltage coming from that part of the brain, in contrast, when they are firing at lower levels the voltage will be more negative (Empson, 1986). Another way in which information gathered from an EEG is the event related brain potential (ERP) (Mangun, Hopfinger, and Heinze, 1998). What an ERP is, is the average number of EEG waveforms that go along with a specific event (Empson, 1986). In other words repeated presentations of a stimulus will be made and the EEG activity of all of them will be averaged. This is an attempt to help filter out the desired components of the EEG from other noise. The average is more closely related to the specificevent being studied than just one recording because of all the other electrical noise (Empson, 1986). The other electrical noise may come from support cells or other neurons not related to the specific task beingstudied. Using ERPs is a more precise way to study brain activity as it is related to specific behavioral events. The ERPs advantages come primarily from the many trials performed to make the average. What the EEG offers is a bridge between behavior and electrical activity into the brain, like phrenology correlated certain mental abilities with bumps. Unlike phrenology the EEG readings can be correlated to an actual physical property of the brain, neuron activity. This provides certain types of information. From this technique ideas can begenerated for the general areas where events are happening in the brain, and it gives insight into the timing and order of things that are occurring. What it lacks is the ability to locate more precise locations and the ability to be correlated to specific structures. Complications of EEG readings result from the depth of the electrical source, and otherconfounding electrical activity in the brain ("brain imaging part I", 1997; Mangun, Hopfinger, & Heinze, 1998).
MORE RECENT METHODS OF STUDYING THE BRAIN Along with EEG there are currently a handful of different techniques available for studying the living brain. Techniques such as computed tomography (CT), positron emission tomography (PET), single photonemission computed tomography (SPECT or sometimes just SPET), magnetic resonance imaging (MRI), and functional magnetic resonance imaging (fMRI).Computed Tomography (CT) One of the first techniques used to gain pictures of the brain for studying was x-ray CT. According to Pfefferbaum and Rosenbloom (1990), aCT image is done by projecting x-ray beams at multiple angels through horizontal sections of the brain. The beams are reduced as they travel through the head and they come into contact with different substances withdifferent densities. For example, brain tissue is much more dense than cerebrospinal fluid (CSF), therefore the x-ray beams will be reduced moreby the brain tissue than the CSF. The different amount of x-rays from the two different densities will result in a difference when analyzed by thecomputer. The computer analyzes the x-ray projections according to certain mathematical rules and generates a picture. When CT pictures first came out the pictures were poorly defined and had very poor resolution, but more current scanners are providing better quality pictures. In studies CT pictures are largely used to look at the spaces in the brain which is occupied by CSF. Because of the physical make-up of brain tissue, it is very hard to see smaller differences in different parts of the brain withCT, but there is a significant difference in brain tissue and CSF that shows up on these pictures (Pfefferbaum & Rosenbloom, 1990). So what manystudies use CT generated pictures for is to show that increased CSF and decreased brain tissue can be seen in specific brain regions. CT scans have many limitations, the biggest of these being the fact that the subject of the scan is exposed to radiation. Others include things such as poor resolution and contrast. Resolution and contrast refer to the ability to clearly distinguish the differences in the separate parts of the brain. These types of scans are very similar to autopsies in what they are studying, and that is brain anatomy. Unlike autopsies though they can look at living brains.
POSITRON EMISSION TOMOGRAPHY (PET)
Currently PET is a widely used technique for brain research. PET scans were the first to provide pictures of the living brain at work ("brain imaging part I", 1997). According to Krasuski, Horwitz, and Rumsey (1996) PET became readily available for studies in the early 1980s. The way that PET scans work is by injecting a person with a radio active isotope. This isotope is usually placed in a type of glucose which can not be burned by the cells in the body. The glucose travels through the blood to all parts of the body, including the brain. Once in the cells, theglucose decays because it can not be used in the cell. What a PET scan is, is a measure of the levels of radio activity in different parts of the brain. After the information is gathered, computers are used to analyze the data and gather the information needed about the physiological process being studied. There are different types of physiological processes whichcan be looked at by these measurements. For instance, researchers use PET scans to gather data on glucose metabolism, oxygen utilization, blood flow, and neurotransmitter concentrations (Krasuski, et. al., 1996). In plain terms, a PET scan is measuring the levels of glucose in different parts of the brain. So what researchers do is take these levels and interpret them by making different types of assumptions. The most basic assumption is that more active parts of the brain will use more blood. In turn, this means that there will be more of the glucose with the radioactive isotope in those parts of the brain. This assumption is not without it`s weakness though. One of the major weaknesses of PET scans is the time period available to produce scans. Because of the isotopes used, the amount of time available for scanning usually runs between 15 seconds to 2 minutes (Mangun, Hopfinger, & Heinze, 1998). Further weaknesses of all of thebrain imaging techniques will be addressed later.
SINGLE PHOTON EMISSION COMPUTED TOMOGRAPHY (SPECT)
SPECT is another technique which can be used in generating pictures of the brain, and is closely related to PET. SPECT first became availablein the 1980s, but it was not until the 1990s that this technique was refined enough for use in brain imaging (Krasuski, Horwitz, and Rumsey, 1996). SPECT scans are well suited for collecting measures of regionalcerebral blood flow (rCBF). SPECT scans utilize radioisotopes that decay by emitting a single gamma ray. These types of radioisotopes have lowerenergy than the photons used in PET scans. This lower energy results in lower sensitivity. The differences that result are basically a longer duration of time in which scans can be made. The amount of time can be upto 40 times longer than with a PET scan (Kuikka & Tiihonen, 1998). However, this longer period of time is traded of for less spatial resolution (Krasuski, et al., 1996). Spatial resolution refers to the ability to perceive detail in the pictures. This technique also comes at a far less cost than PET scanning. Finally, according to Kuikka and Tiihonen (1998) in recent years many receptor and transmitter-specific radioisotopes have been developed. This means that specific receptors can be studied. With this development the areas which are looked at in the brain can become more specific. Rather than just looking at the blood flow of different parts of the brain, the actual substances being used by the neurons in thebrain can be traced. This allows for a link between the brain and behavior other than just rCBF. Both the PET and SPECT make certain assumptions which allow them to be correlated to behavior, like Gall made withphrenology. Although the assumptions made between rCBF and behavior have more scientific backing than Gall had.
MAGNETIC RESONANCE IMAGING (MRI)
Nuclear magnetic resonance has given rise to different tools used in the neuropsychology world: MRI and fMRI. MRI scans werefirst introduced as a clinical tool in the 1970s ("brain imaging part I" 1997). First MRI is a technique which is limited to the study of brain anatomy (Krasuski et al., 1996). Simply stated this is how MRI images are created:First it is essential to know that all protons and neutrons in atomic nuclei have a property called spin. This property of spin causes the atoms to have what is called magnetic moment. All tissue is made up of many millions of atoms and within all of these the proton`s magnetic moment is random, and this causes all of the individual magnetic moments to be canceled out (Bushberg, 1994). The protons of a specific element in a particular magnetic field have a specific frequency called the Larmor frequency. MRI scanners give off a radiofrequency (RF) which creates a magnetic field and causes the protons to resonate at this frequency. When the RF from the MRI scanner is shut off the protons return to their original state of random frequency and spin. As this happens the protonsgive off an RF signal which is equal to the frequency given off by the MRI scanner. The signal given off is called the free induction decay signal and is picked up by an antenna in the MRI scanner (Bushberg, 1994).Computers use the recorded information to construct images of brain structure. According to Liddle (1997) MRI offers these important advantages; there is better soft tissue contrast and no exposure to ionizing radiation. As stated above though, MRI images are limited because they are simply pictures of the brain at a specific moment which are only useful for studying brain anatomy.
FUNCTIONAL MAGNETIC RESONANCE IMAGING (FMRI)
Scientists and neuropsychologists have attempted many different ways to use MRI scans in ways that are applicable to studying brain activity. One of the most prevalent developments that has come about in the 90s is fMRI. Other names for the technique include real-time, fast or dynamic MRI. With fMRIs blood-flow and volume can be studied in the brain,and thus indirectly so can brain activity (Krasuski, Horwitz, and Rumsey, 1996). What an fMRI does is it takes many quickly repeated pictures of the brain and then the blood-flow to different regions can be observed through the changes in the sizes of blood vessels. The major assumption being made here is that the areas of the brain which are in use will use more blood, and if they are using more blood the blood vessels will be larger. Researchers use this technique to look at changing sizes of the bloodvessels and use this data to infer that particular regions of the brain are being used at particular times. This holds advantages over other functional techniques in that there is no need for exposure to radiation or radioactive substances, so it can be used repeatedly on the same subject (Kolata, 1992).
EXAMPLES OF STUDIES WHICH USE THE NEW TECHNOLOGIES The newer indirect methods of studying the brain are widely in use in psychological studies today. Studies have been done on the techniquesthemselves. Many more studies are done for other reasons with brain imaging techniques being the basis of data collection for the study. Some studies use only one technique, while others use different techniques and compare the findings of each. The studies done with these techniques have produced a variety of findings.
CHILDREN STUDIES WITH IMAGING TECHNIQUES
Many studies have been conducted about brain functioning in children. A lot of the studies center around some type of dysfunction in the brains of children. Many types of neurological disorders in children can be quite troublesome, therefore insight into the brain and what might be causing the dysfunction is quite necessary. Learning disorders andattention deficit hyperactivity disorder (ADHD) are a couple of the types of dysfunctions which are quite commonly looked at in studies involving children and brain imaging techniques. According to Bigler, Lajiness-O`Neil, & Howes (1998) dyslexia is the most widely studied learning disorder which is studied through the use of imaging techniques. Also, many of the early neurological studies involving CT were studies done on childhood dyslexia. The first CT studies on dyslexia began in the 1970s and ran through the 80s. After the development and wide acceptance of MRI scans, the CT was replaced by the newer technique. According to Krasuski, Horwitz, and Rumsey (1996) the MRI is the best technique to be used with children because there is no need for the use of radioactive substances. The studies with CT and MRI scans have revealed some interesting findings. Some studies have revealed a possible reversal of the usual brain asymmetry (Leisman & Ashkenazi, 1980; Rosenberger & Hier, 1980). In many brains there is a noticeable level of brain asymmetry between the two hemispheres. What these findings show is that the normal asymmetry is reversed on the two hemispheres. Another finding is an increased ratio of symmetry, which has been seen in some children with learning disorders (Haslam, Dalby, Johns, & Rademaker, 1981). Rosenberger and Hier found that the reversed cerebral asymmetry was found in conjunction with verbal deficits. Many of the findings with both the CT and MRI studies ondyslexia center around the symmetry of the brain. This is an aspect which is well suited for these techniques which focus on anatomy rather thanfunction. The findings of the studies using the imaging techniques are not without discrepancies. According to Galaburda, Sherman, Rosen, Aboitiz,and Geshwind (1985) some discrepancies have been seen between MRI studies and previous autopsy results. Some previously noted structural changes orabnormalities which were seen in dyslexia patients autopsies were not seen on MRI scans. In all of the studies mentioned above anatomy is what is being looked, and in many cases that simply is not enough. Other aspects which are more closely related to behavior must be looked at with the use oftechniques such as fMRI, PET and SPECT. The most promising of these techniques for use with learning disabilities is the fMRI. To date there have not been an extensive amount of studies on this topic using thistechnique, although preliminary studies show that this technique could be exceptionally useful in looking at functional differences in people with learning disorders (Bigler, Lajiness-O`Neil, & Howes, 1998). The other functional techniques mentioned earlier (PET and SPECT) have not been used very extensively in learning disability studies.
IMAGING TECHNIQUES USED IN SCHIZOPHRENIC STUDIES
Another major use of imaging techniques is with patients who suffer from schizophrenia. Schizophrenia is arguably the most serious common psychological disorder. It is also the most extensively studied of any of the disorders. By using the MRI and CT scans, it has been shown numeroustimes that the ventricles in the brains of schizophrenics are larger than those in healthy brains ("brain imaging part II", 1997). The implicationof the ventricles being larger is that this could be a sign that there is less tissue in other parts of the brain. Other studies have also shown that there may possibly be abnormalities in some specific parts of thebrain such as the prefrontal lobe (Begley, 1995). The MRI and CT scans are sufficient for these kinds of studies when all that is being looked at is the major physical differences. This poses a problem because only a correlation can be made. Correlations are made between the areas seen to have activity in the scans and the behaviors which are taking place. Because of the nature of a correlational studies no causal conclusions can be made. The functional techniques (PET, SPECT, and fMRI) are what are being used to help make a closer tie between the behavior associated with schizophrenia and the areas of the brain which are being affected.According to Begley (1995) some studies done with PET scans have actually shown activity in the brains of schizophrenic patients as they are hearing voices and having other hallucinations. Hearing unexplainable voices and having hallucinations are some symptoms of schizophrenia (Sarason & Sarason, 1996). Some of the regions in which the activity was seen during these studies are the thalamus, hippocampus, and the striatum (Begley, 1995). So the information which these studies are providing is some of the locations where some of the symptoms of schizophrenia might be originating. What these studies and scans do not provide is insight about the timing or the sequencing of the events that might lead to the symptoms.
LIMITATIONS OF THE NEW TECHNIQUES Some of the limitations of the specific techniques have been covered as those techniques were discussed. There are more limitations which in some cases are general in the fact that they effect all of the imaging techniques, and others are more technique specific. The following section covers some of these techniques which fall into both groups. The most obvious and pressing limitation is the fact that these techniques, like phrenology, use secondary techniques to study the brain. They do not directly look at the brain. This is true of all of the newer techniques. The images created by CT scans are based on differing levels of radiation passing through the tissue which then creates a picture whichshows contrasts in tissue by varying darkness on the picture (Pfefferbaum and Rosenbloom, 1990). The PET and SPECT scans are based on rCBF. Specifically, a radioactive substance which is carried through the blood with a form of glucose which cannot be used by the brain ("brain imaging part I", 1997). Lastly, with either of the magnetic resonance imaging techniques (MRI & fMRI) the information that is gathered is numerical data, not actual visual pictures. The images are then generated by computers from the numerical data through a series of mathematical calculations done by a computer (Leonard, 1997). Then, in the case of fMRI, the connection between the picture and behavior is made by looking at blood flow. This is done by analyzing the size changes of blood vessels in different parts of the brain (Krasuski, Horwitz, and Rumsey, 1996). The similarity with all of these techniques is they do not look at the brain directly. The pictures generated from these techniques do allow an indirect way see the brain, but this is not the same as looking at the actual tissue. With the MRI and CT the objective is to look at the living brain with least evasive procedures necessary. But as some research has pointed out these discrepancies have been found between these techniques and data from autopsies, which look directly at the brain tissue ( Galaburda, Sherman, Rosen, Aboitiz, & Geshwind, 1985), and from study to study using the same imaging techniques(Schultz, Cho, Staib, Kier, Fletcher, Shaywitz, Shankweiler, Katz, Gore, Duncan, & Shaywitz, 1994). With the functional techniques the link betweenthe brain and behavior is being made through secondary measures as phrenology did. "Blood flow and other measures are not always correlated with nerve cell activity" ("brain imaging part 1", 1997, p. 4). It is the activity in the nerve cells of the brain which needs to be studied more closely, and these techniques do not allow for this to be done. Other limitations to these techniques have to do with how the techniques are done and some of the factors which can have profound influences as to the turn out of the images. In this case each of thedifferent techniques have their own specific limitations. The MRI and the fMRI share some of the same limitations due to the fact that how the imagesare created is the same. Both of these techniques can bring a high cost, have a tendency to pick up anatomic abnormalities that can be misinterpreted, and a great need for patient cooperation ("what is", 1994).The patient`s cooperation is needed as any type of head movement can effect the outcome of the image (Bookheimer & Dapretto, 1997). A problem that isspecific to the fMRI has to do with the amount of activity that one can do during the test. Obviously the fMRI is trying to make a connection betweenbehavior and brain activity. Because of the nature of the test the type of behavior which can be exhibited will be greatly limited. It is clear that the behavior could not involve any thing that would involve head movement. The PET and SPECT techniques also share a great deal of limitations. The most prominent being that the brain is exposed to radioactive materials (Krasuski, Horwitz, & Rumsey, 1996). It has alsobeen shown that these techniques can be especially susceptible to drugs in the body, especially some common drugs such as nicotine and caffeine. OnePET study in particular showed a 30% increase in cerebral blood flow after the equivalent of two cups of coffee were given to the patient ("brain imaging part 1", 1997). The use of a radio tracer in glucose is a way to trace the brain`s use of it`s energy source. Kolata (1992, p. C1) says this in regards to this concept, "what people really want to see are thefine details of delicate interactions between nerve cells." Unfortunately, the these techniques do not provide this ability. With these techniquesthe window of opportunity to gain an image is also limited because of the physical properties of the radio tracer substances used. It can take up toten seconds to gain on image and there may only be a window on about two minutes when it is possible to gain images (Mangun, Hopfinger, & Heinze,1998). A severe limitation of the functional techniques is the loss of temporal information. That is the course of time over which the brain functions are taking place. The period of time over which the techniques are required to gather data makes it impossible for the techniques to have temporal information incorporated into them. The PET scans are basically blind to any type of temporal aspects of brain functioning, while fMRI has a limited ability to provide information into this area (Wang, Toro,Wassermann, Zeffiro, Thatcher, & Hallett, (1994). There is one technique which is suited for studying the temporal aspect of the brain, that is theEEG. Currently there are several attempts to combine EEG information with imaging techniques in order to combine the spatial properties on the images with the temporal abilities of the EEG. This combination of these different technologies could provide a great amount of insight into the functioning of the human brain. With the two technologies used togetherthe outcome is spatial resolution greater than that of the EEG alone, and the temporal information which the imaging techniques can not provide (Wieringa, Peters, & Lopes da Silva, 1994). A final limitation to the techniques which are currently in use stems from the lack of understanding of the very techniques themselves. It is very easy to look at technology and just assume that everything shows exactly what it is thought to be showing. People must remember that at one time it was believed by many that the bumps on their heads could lead toinsight into their brains. Watson (1996, p. 547) says this in regards to the new technologies which are widely in use, "we must emphasize evidence-based medicine." There have literally been hundreds of studies on the imaging techniques which are currently available. Many of these studies support the techniques, while others refute them. One thing iscertain though, the techniques will never provide any information beyond the knowledge of those who are using them. Perhaps this means that the techniques we currently have are sufficient to provide insight into the brain and it`s links to behavior. Possibly it is the scientific communities knowledge of these techniques that is lacking. In this way thetechniques of today are much like phrenology was at its inception. Those who accepted it did so without the proper information or knowledge needed.
CONCLUSION Some of the first attempts to think about the living brain came from Gall and phrenology. Phrenology attempted to relate personality andbehavioral traits with bumps on the head. While phrenology is not accepted today the relation between parts of the brain and certain behaviors is. Itis the functional neuroimaging techniques which are attempting to bridge the barrier between the understanding of specific behavior events and thebrain. These techniques try to relate specific events to specific areas and the brain at specific times. EEG, PET, SPECT, MRI, and fMRI are the techniques which are used today and attempt to draw more links between the brain and behavior. Each of these techniques use their own specific properties to study the brain and behavior. The EEG uses electricity togain a pathway into the workings of the brain. PET and SPECT techniques use rCBF as their primary measurement of brain activity (Horwitz, 1994).Similarly fMRI images also measure blood flow. Instead of using a substance which is actually in the blood, the fMRI is used to study the increasing and decreasing size of the blood vessels in the brain (Kolata, 1992). All of these techniques, including the EEG and phrenology, share a common bond in the fact that are trying to look at the brain in a secondary fashion. That is through things such as bumps, electricity, or blood flow. All of these techniques also share similarities in that they look at the brain indirectly. The question is, are these techniques which use indirect methods to view the brain as good or effective as looking at the brain moredirectly. If looking at the brain indirectly is good enough, then which method is the most effective and reliable to look at the brain and behavior? Perhaps blood flow or electricity is not actually any betterthan bumps. It is possible that technology really has not come very far from Gall`s ideas. There truly will not be total insight into the brain and behavior until better methods are developed, or more knowledge isgained about the methods which are currently in use.
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