{"id":190,"date":"2023-02-17T22:37:16","date_gmt":"2023-02-17T22:37:16","guid":{"rendered":"https:\/\/content.one.lumenlearning.com\/introductiontopsychology\/chapter\/1993\/"},"modified":"2023-07-07T14:36:46","modified_gmt":"2023-07-07T14:36:46","slug":"1993","status":"publish","type":"chapter","link":"https:\/\/content.one.lumenlearning.com\/introductiontopsychology\/chapter\/1993\/","title":{"raw":"Studying the Brain: Learn It 3\u2014Brain Imaging","rendered":"Studying the Brain: Learn It 3\u2014Brain Imaging"},"content":{"raw":"
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You have learned how brain injury can provide information about the functions of different parts of the brain. Increasingly, however, we are able to obtain that information using brain imaging<\/strong> techniques on individuals who have not suffered a brain injury.\u00a0<\/section>
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Studying the Brain: Techniques Involving Radiation<\/h2>\r\n
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CT scan<\/h3>\r\nA computerized tomography (CT) scan <\/strong>(also called a cat scan) involves taking a number of x-rays of a particular section of a person\u2019s body or brain (Figure 1). The x-rays pass through tissues of different densities at different rates, allowing a computer to construct an overall image of the area of the body being scanned. A CT scan is often used to determine whether someone has a tumor, or significant brain atrophy.\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"396\"]\"Image Figure 1<\/strong>. A CT scan can be used to show brain tumors. (a) The image on the left shows a healthy brain, whereas (b) the image on the right indicates a brain tumor in the left frontal lobe. (credit a: modification of work by \"Aceofhearts1968\"\/Wikimedia Commons; credit b: modification of work by Roland Schmitt et al)[\/caption]\r\n\r\n<\/section>
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PET scan<\/h3>\r\nPositron emission tomography (PET) scans<\/strong> create pictures of the living, active brain. An individual receiving a PET scan drinks or is injected with a mildly radioactive substance, called a tracer. Once in the bloodstream, the amount of tracer in any given region of the brain can be monitored. As a brain area becomes more active, more blood flows to that area. A computer monitors the movement of the tracer and creates a rough map of active and inactive areas of the brain during a given behavior.\r\n\r\nPET scans can detect various diseases and are useful in studying neurotransmitter activity. They show little detail, are unable to pinpoint events precisely in time, and require that the brain be exposed to radiation; therefore, this technique has been replaced by the fMRI as an alternative diagnostic tool. However, when combined with CT (cat scans), PET technology can still be helpful in imaging of the activity of neurotransmitter receptors and open new avenues in schizophrenia research. In this hybrid CT\/PET technology, CT contributes clear images of brain structures, while PET shows the brain\u2019s activity.\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"222\"]\"A Figure 2<\/strong>. A PET scan is helpful for showing activity in different parts of the brain. (credit: Health and Human Services Department, National Institutes of Health)[\/caption]\r\n\r\nSimilar to PET, Single-photon Emission Computed Tomography (SPECT)<\/strong> uses gamma ray-emitting radioisotopes to create images of active brain regions. It is commonly used for epilepsy imaging and dementia diagnosis.\r\n\r\n<\/section>\r\n
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Studying the Brain: Techniques Involving Magnetic Fields or Electrical Activity<\/h2>\r\n
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MRI<\/h3>\r\nIn magnetic resonance imaging (MRI)<\/strong>, a person is placed inside a machine that generates a strong magnetic field. The magnetic field causes the hydrogen atoms in the body\u2019s cells to move. When the magnetic field is turned off, the hydrogen atoms emit electromagnetic signals as they return to their original positions. Tissues of different densities give off different signals, which a computer interprets and displays on a monitor.\r\nThe result produces detailed 2D or 3D images of brain structures without radiation. It provides high-quality images but is relatively expensive.\r\n\r\n<\/section><\/section>
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fMRI<\/h3>\r\nFunctional magnetic resonance imaging (fMRI)<\/strong>\u00a0operates on the same principles as MRI but focuses on changes in brain activity over time by tracking blood flow and oxygen levels. It enables researchers to observe brain activation patterns by analyzing the associated changes in blood flow. fMRI is widely employed in cognitive and behavioral studies and offers more detailed images of brain structure and better temporal accuracy compared to PET scans.\r\n\r\n \r\n\r\nWith their high level of detail, MRI and fMRI are often used to compare the brains of healthy individuals to the brains of individuals diagnosed with psychological disorders. This comparison helps determine what structural and functional differences exist between these populations.\r\n\r\n \r\n\r\nBoth PET scans and fMRIs have good spatial resolution (showing where<\/em> things happen), but because it takes at least several seconds for the blood to arrive to the active areas of the brain, PET and fMRI have poor temporal resolution; that is, they do not tell us very precisely when<\/em> the activity occurred.\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"197\"]\"A Figure 3<\/strong>. An fMRI shows activity in the brain over time. This image represents a single frame from an fMRI. (credit: modification of work by Kim J, Matthews NL, Park S.) Areas of brain activation are determined by the amount of blood flow to a certain area \u2013 the more blood flow, the higher the activation of that area of the brain.[\/caption]\r\n\r\n<\/section><\/section>
[ohm2_question height=\"400\"]3948[\/ohm2_question]<\/section><\/section>
In some situations, it is helpful to gain an understanding of the overall activity of a person\u2019s brain, without needing information on the actual location of the activity. In this case, the technology can rely on measuring electrical activity to record brainwaves.\r\n\r\n
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EEG<\/h3>\r\nElectroencephalography (EEG)<\/strong> provides a measure of a brain\u2019s electrical activity. EEG measures a brain's electrical activity by placing an array of electrodes around a person's head. The signals received by the electrodes provide a printout of the brain's electrical activity, displaying brainwaves' frequency and amplitude with millisecond accuracy.\r\n\r\nEEG is particularly helpful in studying sleep patterns among individuals with sleep disorders, although its spatial resolution is limited. Because the electrical activity picked up at any particular electrode can be coming from anywhere in the brain, EEG has poor spatial resolution; that is, we have only a rough idea of which part of the brain generates the measured activity.\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"488\"]\"A Figure 4<\/strong>. Using caps with electrodes, modern EEG research can study the precise timing of overall brain activities. (credit: SMI Eye Tracking)[\/caption]\r\n\r\n<\/section>This is not an exhaustive list of brain imaging techniques; there are also methods such as Diffuse Optical Imaging (DOI)<\/strong>, Event-related Optical Signal (EROS)<\/strong>, and Magnetoencephalography (MEG)<\/strong>. DOI and EROS employ near-infrared light to measure changes in optical properties or scattering of active brain areas. MEG measures magnetic fields produced by brain electrical activity, offering high temporal resolution but lower spatial resolution compared to fMRI. The newer technology of Quantum Optically-pumped Magnetometer<\/strong> enhances MEG's accuracy and detail by utilizing quantum sensors.\r\n

Brain Stimulation<\/h3>\r\nIn addition to using technology to scan the brain, similar technologies can also be used to stimulate specific areas of the brain.\r\n\r\n
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TMS<\/h3>\r\nTranscranial magnetic stimulation (TMS)<\/strong> refers to a technique whereby a brief magnetic pulse is applied to the head that temporarily induces a weak electrical current in the brain. Although effects of TMS are sometimes referred to as temporary virtual lesions, it is more appropriate to describe the induced electricity as interference with neurons\u2019 normal communication with each other. TMS allows very precise study of when events in the brain happen so it has a good\u00a0temporal resolution, but its application is limited only to the surface of the cortex and cannot extend to deep areas of the brain.\r\n\r\nTranscranial direct current stimulation (tDCS)<\/strong> is similar to TMS except that it uses electrical current directly, rather than inducing it with magnetic pulses, by placing small electrodes on the skull. A brain area is stimulated by a low current (equivalent to an AA battery) for a more extended period of time than TMS. When used in combination with cognitive training, tDCS has been shown to improve performance of many cognitive functions such as mathematical ability, memory, attention, and coordination (e.g., Brasil-Neto, 2012; Feng, Bowden, & Kautz, 2013; Kuo & Nitsche, 2012).\r\n\r\n<\/section>Because the spatial and temporal resolution of each brain imaging tool varies, the strongest evidence for what role a certain brain area serves comes from converging evidence. For example, we are more likely to believe that the hippocampal formation is involved in memory if multiple studies using a variety of tasks and different neuroimaging tools provide evidence for this hypothesis. The brain is a complex system, and only advances in brain research will show whether the brain can ever really understand itself.\r\n\r\n<\/section>\r\n
[ohm2_question height=\"600\"]3949[\/ohm2_question]<\/section><\/div>","rendered":"
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You have learned how brain injury can provide information about the functions of different parts of the brain. Increasingly, however, we are able to obtain that information using brain imaging<\/strong> techniques on individuals who have not suffered a brain injury.\u00a0<\/section>\n
\n

Studying the Brain: Techniques Involving Radiation<\/h2>\n
\n

CT scan<\/h3>\n

A computerized tomography (CT) scan <\/strong>(also called a cat scan) involves taking a number of x-rays of a particular section of a person\u2019s body or brain (Figure 1). The x-rays pass through tissues of different densities at different rates, allowing a computer to construct an overall image of the area of the body being scanned. A CT scan is often used to determine whether someone has a tumor, or significant brain atrophy.<\/p>\n

\"Image
Figure 1<\/strong>. A CT scan can be used to show brain tumors. (a) The image on the left shows a healthy brain, whereas (b) the image on the right indicates a brain tumor in the left frontal lobe. (credit a: modification of work by “Aceofhearts1968″\/Wikimedia Commons; credit b: modification of work by Roland Schmitt et al)<\/figcaption><\/figure>\n<\/section>\n
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PET scan<\/h3>\n

Positron emission tomography (PET) scans<\/strong> create pictures of the living, active brain. An individual receiving a PET scan drinks or is injected with a mildly radioactive substance, called a tracer. Once in the bloodstream, the amount of tracer in any given region of the brain can be monitored. As a brain area becomes more active, more blood flows to that area. A computer monitors the movement of the tracer and creates a rough map of active and inactive areas of the brain during a given behavior.<\/p>\n

PET scans can detect various diseases and are useful in studying neurotransmitter activity. They show little detail, are unable to pinpoint events precisely in time, and require that the brain be exposed to radiation; therefore, this technique has been replaced by the fMRI as an alternative diagnostic tool. However, when combined with CT (cat scans), PET technology can still be helpful in imaging of the activity of neurotransmitter receptors and open new avenues in schizophrenia research. In this hybrid CT\/PET technology, CT contributes clear images of brain structures, while PET shows the brain\u2019s activity.<\/p>\n

\"A
Figure 2<\/strong>. A PET scan is helpful for showing activity in different parts of the brain. (credit: Health and Human Services Department, National Institutes of Health)<\/figcaption><\/figure>\n

Similar to PET, Single-photon Emission Computed Tomography (SPECT)<\/strong> uses gamma ray-emitting radioisotopes to create images of active brain regions. It is commonly used for epilepsy imaging and dementia diagnosis.<\/p>\n<\/section>\n

<\/figure>\n<\/section>\n
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Studying the Brain: Techniques Involving Magnetic Fields or Electrical Activity<\/h2>\n
\n

MRI<\/h3>\n

In magnetic resonance imaging (MRI)<\/strong>, a person is placed inside a machine that generates a strong magnetic field. The magnetic field causes the hydrogen atoms in the body\u2019s cells to move. When the magnetic field is turned off, the hydrogen atoms emit electromagnetic signals as they return to their original positions. Tissues of different densities give off different signals, which a computer interprets and displays on a monitor.
\nThe result produces detailed 2D or 3D images of brain structures without radiation. It provides high-quality images but is relatively expensive.<\/p>\n<\/section>\n<\/section>\n

\n
\n

fMRI<\/h3>\n

Functional magnetic resonance imaging (fMRI)<\/strong>\u00a0operates on the same principles as MRI but focuses on changes in brain activity over time by tracking blood flow and oxygen levels. It enables researchers to observe brain activation patterns by analyzing the associated changes in blood flow. fMRI is widely employed in cognitive and behavioral studies and offers more detailed images of brain structure and better temporal accuracy compared to PET scans.<\/p>\n

 <\/p>\n

With their high level of detail, MRI and fMRI are often used to compare the brains of healthy individuals to the brains of individuals diagnosed with psychological disorders. This comparison helps determine what structural and functional differences exist between these populations.<\/p>\n

 <\/p>\n

Both PET scans and fMRIs have good spatial resolution (showing where<\/em> things happen), but because it takes at least several seconds for the blood to arrive to the active areas of the brain, PET and fMRI have poor temporal resolution; that is, they do not tell us very precisely when<\/em> the activity occurred.<\/p>\n

\"A
Figure 3<\/strong>. An fMRI shows activity in the brain over time. This image represents a single frame from an fMRI. (credit: modification of work by Kim J, Matthews NL, Park S.) Areas of brain activation are determined by the amount of blood flow to a certain area \u2013 the more blood flow, the higher the activation of that area of the brain.<\/figcaption><\/figure>\n<\/section>\n<\/section>\n
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