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Frontal lobe injury

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File:Four lobes animation small2.gif
This image shows the four lobes of the human brain: the frontal lobe (red), the parietal lobe (orange), the temporal lobe (green), and the occipital lobe (yellow). Also shown are the insular cortex (purple), the brain stem (black), and the cerebellum (blue).
File:Frontal lobe animation.gif
This image shows a midsagittal cross-section of a human brain. The portion colored red is the left frontal lobe; the famous railroad worker, Phineas Gage, injured the frontmost part of this lobe.[1]

Frontal lobe injury is an aspect of brain damage.

The frontal lobe of the human brain is both relatively large in mass and less restricted in movement than the posterior portion of the brain.[2] It is a component of the cerebral system, which supports goal directed behavior.[3] This lobe is often cited as the part of the brain responsible for the ability to decide between good and bad choices, as well as recognize the consequences of different actions. Because of its location in the anterior part of the head, the frontal lobe is arguably more susceptible to injuries. Following a frontal lobe injury, an individual’s abilities to make good choices and recognize consequences are often impaired. Memory impairment is another common effect associated with frontal lobe injuries, but this effect is less documented and may or may not be the result of flawed testing.[4] Damage to the frontal lobe can cause increased irritability, which may include a change in mood and an inability to regulate behavior.[2] Particularly, an injury of the frontal lobe could lead to deficits in executive function, such as anticipation, goal selection, planning, initiation, sequencing, monitoring (detecting errors), and self-correction (initiating novel responses).[5] Perhaps the most famous case of executive function impairment following a frontal lobe injury is Phineas Gage, the railroad worker impaled through the frontal lobe by a rail spike in the 1800s.[2]

Phineas GageEdit

File:PhineasPGage.jpg
A cabinet-card portrait of Phineas P. Gage (1823–1860) holding the tamping iron that shot through his left frontal lobe.
Phineas Gage CGI
A computer-generated image (CGI) of the rod piercing Phineas Gage's skull.
PhloxBotAdded by PhloxBot

Only 25 years old in the year 1848, a construction worker by the name of Phineas Gage experienced a terrible, yet intriguing brain injury. In an accidental explosion, a 13-pound iron rod shot into his cheek (under the left zygomatic arch) and out of the top of his head, (left of the midline).[6][7] Despite speculation and folklore about the location of Gage’s cerebral injury, damage was limited specifically to the left frontal lobe.[1] While he amazingly survived, the impalement led to changes in his behavior/personality. The details of the resulting changes that have been reported over the years differ, but what remains clear is that Gage’s behavior changed after his accident.[7] Gage’s friends simply described him as “no longer Gage,” and he was subsequently fired from his railroad job for his inability to “work with others,” even though he was still physically capable of doing the work; this coincides with a found correlation of poor employment outcomes associated with injuries involving an object striking the head.[6][8] Phineas Gage is one of the most famous cases of survival after a substantial brain injury, and assuredly the most famous case of resulting personality changes.

A moral man, Phineas Gage,

Tamping powder down holes for his wage,

Blew the last of his probes

Through his two frontal lobes;

Now he drinks, swears, and flies in a rage. (Unknown Author)

Neuropsychological EffectsEdit

Memory/AttentionEdit

Patients with damaged frontal lobes often complain of minimal to substantial memory loss. Because of this, frontal lobe lesions (injuries) have long been associated with memory problems, despite little evidence actually showing this relation to be true. In fact, when patients with such injuries are tested using standard memory tests, they often score within normal. Close relatives of these same patients, however, may describe substantial “everyday memory problems.” Why does this disparity occur? When the memory of some such patients has been looked at more closely, it is not the memory system itself that is afflicted, but the "functions" of the frontal lobe that ‘’facilitate memory’’.[4] It is important to note that the memory referred to here is working memory. Working memory is closely involved with the ability to hold attention; or put another way, maintain goals.[9] Working memory is not simply how much information you can maintain in a brief period of time; this describes primary memory, and a small part of working memory relates to it. The important part of working memory is secondary memory, in which an individual retrieves information. Those with high working memory are able to perform this retrieval even when distracted by another task. Patients with damaged frontal lobes show lower working memory and, therefore, a lessened ability to retrieve information from their secondary memory.[10]

Risk TakingEdit

An increase in impulsivity and/or risk taking is often seen in individuals following frontal lobe damage. While these two concepts may seem to have the same meaning, they are indeed different; impulsivity is simply a response disinhibition, while risk taking is related to the reward-based aspects of decision-making.[11] Put more simply, an impulsive person will make a decision quickly, without considering the consequences, leading ultimately to a lack of self-control. Contrarily, risk takers will look at the consequences but not weigh them; they will jump at the opportunity of a reward even if the likelihood of receiving that reward is slim. The increase of risk taking amongst damaged frontal lobe patients can be directly observed during gambling, and gambling tasks have been developed to measure such behavior.

Determining the EffectsEdit

Types of TestsEdit

Before more advanced technology came about, scientists tested individual behavior using more low-tech means. As technology progressed, so did the tests scientists administer to evaluate a person's cognitive function.[12]

In testing the behavioral effects of a frontal lobe injury, however, many of the tests are still very simple and do not involve greatly advanced technology.

Gambling TaskEdit

File:IowaGamblingTask.gif
This is a screenshot from a computerized version of a particular gambling task, called the Iowa gambling task.

While there are variations in carrying out this test, a pure form should show an inverse relationship between the probability of obtaining a reward and the value of the reward itself; that is to say, a low probability but a high reward or a high probability but a low reward.[11] This ensures that actual gambling skills are not being tested, but simply the preference for high reward despite the risks (risk taking). In one of the ways to carry this out, a set of cards will be presented face down to the individual being tested; one of the cards would be the winning card, and all the others, losers. Cards will then be continuously removed from the pile and added back in randomly, during which time the winning card could be anywhere. Subjects being tested are told they can stop the process at any time and have the cards flipped over; if the winning card is present within the pile they win points. The catch, however, is that more points are awarded when less cards are present; but when less cards are present, the probability of the winning card being within the pile is less. Risk takers are those that go for the higher reward (more points), even though they are less likely to actually receive that reward. They choose a higher, less likely award, over a lower, more probable reward. Subjects that have experienced a frontal lobe injury show just such behavior when tested.

Wisconsin Card Sorting TaskEdit

File:WisconsinCardSort.png
This is a screenshot from a computerized version of the Wisconsin Card Sorting Task.

The Wisconsin Card Sorting Task (WCST) is often used to assess any dysfunction of the prefrontal cortex, the front-most area of the frontal lobe. It specifically measures a human’s executive functioning.[13] An individual being tested (the testee) is told to match test cards to reference cards according to shape, color, or number of stimuli on the cards. The administrator of the test gives feedback after each match, allowing the testee to determine the correct rule of classification. Once a fixed number of correct matches is made, the administrator (unbeknownst to the testee) changes this rule. Now the individual being tested must switch to a new (different) mode of classification to receive feedback from the test administrator that the task is being carried out correctly. Therefore, this task specifically measures cognitive flexibility, the ability to modify the way in which one responds when presented with a new goal/objective.

SaccadeEdit

File:Optokinetic nystagmus.gif
In both forms of the saccade test, every eye movement is tracked, even small movements like the ones shown in this animation.

A saccade is a fast movement of the eyes in a certain direction. In the most simplistic form, there are two types of saccade tests administered in which the only requirement is movement of the eye: the prosaccade and the antisaccade.[14] In the prosaccade, participants are required to quickly look toward a point in response to some attention-catching cue, such as a flashing light. Because there are very powerful evolutionary forces that work to automatically focus attention toward prepotent (greater in power) stiumuli, this type of test does not call upon an individual’s executive control; therefore, the prosaccade is not relevant when testing the effects of frontal lobe damage on executive cognitive control and working memory.[14] Conversely, the antisaccade test requires not only ignoring the flashing cue, but looking in the opposite direction. This task calls for inhibition of a prepotent response as well as planning and executing an eye movement that contradicts instinct. In the anti-saccade test, an individual has to set the goal of ignoring these instincts and continue to ‘’maintain’’ this goal. Those with frontal lobe injuries show lower working memory, and therefore typically do not test well in the antisaccade test.

Flaws in TestingEdit

While impulsivity and risk-taking behavior are both commonly observed following a frontal lobe injury, such traits are hard to evaluate and quantify without some degree of subjectivity.[11] The definitions of these traits are themselves not completely straightforward, nor are they always agreed upon. As a result, the methods to measure such behaviors often differ, and this should be taken into consideration when comparing data/results from different sources. Because of this, caution should be taken in how to interpret different results.

It is also important to remember that a single test cannot be used to measure the effects of a frontal lobe injury, or the aspects of cognitive function it may affect, such as working memory; variety of tests must be used. A subject may be good at one task but show dysfunction in executive function overall. Similarly, test results can be made misleading after testing the same individual over a long period of time. The subject may get better at a task, but not because of an improvement in executive cognitive function. He/she may have simply learned some strategies for doing this particular task that made it no longer a good measurement tool.[10]

Patients with damaged frontal lobes often complain of minimal to substantial memory loss, even though when such patients are tested using standard memory tests, they often score within normal. The disparity could be the result of the limits of these standardized tests.[4] Just as likely, the scientific community may not be comparing the right groups of people. Little is understood about frontal lobe functions facilitating memory, but what is clear is that more in-depth research of brain injury patients is needed. Because most research compares those with brain injuries (whether frontal lobe or not) and those without, the scientific community is unsure whether certain memory impairment is specific to frontal lobe injuries, or just traumatic brain injuries in general. There are many factors to consider when examining the effects of a traumatic brain injury, such as the nature of the injury as well as its cause; but the severity of the injury seems to be most important in affecting memory impairment specific to frontal lobe damage. Those patients suffering a mild traumatic brain injury with frontal lobe damage seem to be only slightly affected, if affected at all.

Frontal lobe injuries have been shown to cause decreased ability in combining events that are temporally separated (separated by time), as well as recalling information in its correct context. However, standardized testing, may mask an impairment because the patients are strictly regulated, as are their discretionary behaviors. Many times, these are behaviors thought to be directly related to disorders of the frontal lobe. It could very well be that instead of a memory impairment, these patients are suffering from a different problem entirely, such as paying attention, or vice versa. Therefore, the main conclusion that can be agreed upon is that tests should continuously be scrutinized; as society progresses, better tests should be designed. Without the proper tests to assess traumatic brain injury patients with frontal lobe damage in particular, we may be misrepresenting the functions of the frontal lobe, specifically the role it plays in memory.[4]

See alsoEdit

ReferencesEdit

  1. 1.0 1.1 Ratiu, P., Talos, I.F., Haker, S., Lieberman, D., & Everett, P. (2004). "Case Report: The Tale of Phineas Gage, Digitally Remastered." Journal of Neurotrauma, 21(5), 637-643. Retrieved from http://xa.yimg.com/kq/groups/17972496/1410518588/name/ct+phineas.pdf
  2. 2.0 2.1 2.2 Lux, W.E. (2007). A neuropsychiatric perspective on traumatic brain injury. Journal of Rehabilitation Research & Development, 44(7), 951-962. Retrieved from http://www.rehab.research.va.gov/jour/07/44/7/pdf/lux.pdf
  3. Badre, D. & D'Esposito, M. (2009). "Is the rostro-caudal axis of the frontal lobe hierarchical?" Nature Reviews Neuroscince, 10, 659-669. Retrieved from http://despolab.berkeley.edu/files/publications/pdf/2009badrenature.pdf
  4. 4.0 4.1 4.2 4.3 Kim, J.S., Kim, O.L., Seo, W.S., Koo, B.H., Joo,Y., & Bai, D.S. (2009). "Memory Dysfunctions after Mild and Moderate Traumatic Brain Injury : Comparison between Patients with and without Frontal Lobe Injury. " Journal of Korean Neurosurgical Society, 46(5), 459-467. Retrieved from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2796352/
  5. Lezak M.D. (1989). Assessment of psychosocial dysfunction resulting from head trauma. In: Lezak MD, editor. Assessment of the behavioral consequences of head trauma. New York (NY): A. R. Liss; 113–43.
  6. 6.0 6.1 Boss, A. (2010). "The Gruesome Story of Phineas Gage." PsychologyDegreeGuide.org, retrieved December 2, 2011 from http://psychologydegreeguide.org/phineas-gage/
  7. 7.0 7.1 Macmillan, Malcolm. (2000). "Restoring Phineas Gage: a 150th Retrospective. " Journal of the History of the Neurosciences, 9(1), 46-66. Retrieved from http://www.tandfonline.com/doi/abs/10.1076/0964-704X(200004)9%3A1%3B1-2%3BFT046
  8. Ownsworth, T. & McKenna, K. (2004). "Investigation of factors related to employment outcome following traumatic brain injury: a critical review and conceptual model." Disability and Rehabilitation, 26(13), 765-784.
  9. Broadway, J.M., Redick, T.S., & Engle, R.W. (2010). “Working memory capacity: Self-control is (in) the goal.” In R. Hassin, K. N. Ochsner, & Y. Trope (Eds.), Oxford University Press: New York, NY. Self-control in society, mind, and brain; 163-173. Retrieved from http://psychology.gatech.edu/renglelab/Publications/2010/Broadway%20Redick%20Engle%202010.pdf
  10. 10.0 10.1 Kane, M.J. & Engle, R.W. (2002). “The role of prefontal cortex in working-memory capacity,executive attention, and general fluid intelligence: An individual-differences perspective.” Psychonomic Bulletin & Review, 9(4), 637-671. Retrieved from http://psychology.gatech.edu/renglelab/Publications/2002/The%20role%20of%20prefrontal%20cortex%20in%20working-memory%20capacity.pdf
  11. 11.0 11.1 11.2 Floden, D., Alexander, M.P., Kubu, C.S., Katz, D., & Stuss, D.T. (2008). “Impulsivity and risk-taking behavior in focal frontal lobe lesions.” Neuropsychologia, 46, 213-223. Retrieved from http://www.psych.yorku.ca/joelab/jc/journalclub/gambling/2008Floden%20et%20al_RaymondMar_GamblingTask%202008.pdf
  12. Purves, D. (2008). ‘’Neuroscience’’ (4th ed.). Sunderland, MA: Sinauer Associates, Inc.
  13. Monchi, O., Petrides, M., Petre, V., Worsley, K., & Dagher, A. (2001). “Wisconsin Card Sorting Revisited: Distinct Neural Circuits Participating in Different Stages of the Task Identified by Event-Related Functional Magnetic Resonance Imaging.” Journal of Neuroscience, 21(19), 7733-7741. Retrieved from http://www.jneurosci.org/content/21/19/7733.full
  14. 14.0 14.1 Unsworth, N., Engle, R.W., & Schrock, J.C. (2004). “Working Memory Capacity and the Antisaccade Task: Individual Differences in Voluntary Saccade Control.” Journal of Experimental Psychology, 30(6), 1302-1321. Retrieved from http://www.interactivemetronome.com/impublic/Research/Temporal%20Processing/MemoryWorkingMemory/Research_Working%20Memory_Unsworth2004.pdf

Further readingEdit

  • Humphreys, G. W. & Riddoch, M. J. (2000) One more cup of coffee for the road: Object-action assemblies, response blocking and response capture after frontal lobe damage. Experimental Brain Research, 133, 81-93

External linksEdit

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