{"id":1513,"date":"2019-01-11T19:36:02","date_gmt":"2019-01-11T19:36:02","guid":{"rendered":"https:\/\/courses.lumenlearning.com\/wm-lifespandevelopment\/?post_type=chapter&#038;p=1513"},"modified":"2024-04-30T19:52:18","modified_gmt":"2024-04-30T19:52:18","slug":"theories-of-aging","status":"publish","type":"chapter","link":"https:\/\/courses.lumenlearning.com\/wm-lifespandevelopment\/chapter\/theories-of-aging\/","title":{"raw":"Theories on Aging","rendered":"Theories on Aging"},"content":{"raw":"<div class=\"textbox learning-objectives\">\r\n<h3>Learning Outcomes<\/h3>\r\n<ul>\r\n \t<li>Describe and compare theories of aging<\/li>\r\n<\/ul>\r\n<\/div>\r\n\r\n[caption id=\"attachment_3549\" align=\"alignright\" width=\"576\"]<img class=\"wp-image-3549\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/3707\/2019\/01\/17154431\/man-person-black-and-white-woman-white-photography-671672-pxhere.com_-1024x683.jpg\" alt=\"older woman smiling\" width=\"576\" height=\"385\" \/> <strong>Figure 1.<\/strong>\u00a0There are several plausible theories as to why aging happens[\/caption]\r\n<h2>Why do we age?<\/h2>\r\nThere are a number of attempts to explain why we age and many factors that contribute to aging.\u00a0The <strong>peripheral slowing hypothesis<\/strong>\u00a0suggests that overall processing speed declines in the\u00a0peripheral\u00a0nervous system,\u00a0affecting\u00a0the\u00a0brain's\u00a0ability to communicate with\u00a0muscles and organs.\u00a0Some of\u00a0the peripheral nervous system (PNS) is under\u00a0a person's voluntary control, such as the nerves\u00a0carrying instructions from\u00a0the\u00a0brain to\u00a0the limbs. As well as controlling\u00a0muscles and joints, the PNS sends all the information from\u00a0\u00a0the\u00a0senses back to\u00a0the\u00a0brain.\r\n\r\nThe <strong>generalized slowing hypothesis<\/strong>\u00a0theory\u00a0suggests that\u00a0processing in all parts of the nervous system, including the brain, are less efficient with age.\u00a0This may be\u00a0why older people have more accidents. Genetics, diet, lifestyle, activity, and exposure to pollutants all play a role in the aging process.[footnote]Plude, D. J., &amp; Doussard-Roosevelt, J. A. (1989). <em>Aging, selective attention, and feature integration. Psychology and Aging, 4(1), 98-105.[\/footnote][footnote]NCBI Bookshelf. A service of the National Library of Medicine, National Institutes of Health. Murray MM, Wallace MT, editors[\/footnote][footnote]The Neural Bases of Multisensory Processes. Boca Raton (FL): CRC Press\/Taylor &amp; Francis; 2012. Chapter 20Multisensory Integration and Aging Authors Jennifer L. Mozolic, Christina E. Hugenschmidt, Ann M. Peiffer, and Paul J. Laurienti.[\/footnote]<\/em>\r\n\r\n<strong>Cell Life\u00a0<\/strong>\r\n\r\nCells divide a limited number of times<span style=\"color: #333333;\"> and then stop. This\u00a0phenomenon, known as the\u00a0<strong>Hayflick limit<\/strong>,\u00a0is evidenced in cells studied in test tubes which divide about 50 times before becoming senescent.\u00a0In 1961, Dr.\u00a0Hayflick\u00a0theorized that\u00a0the human cell's ability to divide is limited to approximately 50-times, after which they simply stop dividing (the\u00a0Hayflick limit theory of aging). According to telomere\u00a0theory, telomeres have experimentally been shown to shorten with each successive cell division.[footnote]Jin K. (2010). Modern Biological Theories of Aging. Aging and disease, 1(2), 72\u201374.[\/footnote]<\/span>\r\n\r\nSenescent cells do not die.\u00a0They simply stop replicating.\u00a0Senescent cells can help limit the growth of other cells which may reduce risk of developing tumors when younger, but can alter genes later in life and result in promoting the growth of tumors as we age (Dollemore, 2006).\u00a0Limited cell growth is attributed to\u00a0telomeres\u00a0which are the tips of the protective coating around chromosomes.\u00a0Each time cells replicate, the telomere is shortened.\u00a0Eventually, loss of telomere length is thought to create damage to chromosomes and produce cell senescence.\r\n<div class=\"textbox exercises\">\r\n<h3>Link to Learning<\/h3>\r\nWatch this Ted talk by molecular biologist Elizabeth Blackburn on \"<a href=\"https:\/\/www.ted.com\/talks\/elizabeth_blackburn_the_science_of_cells_that_never_get_old\" target=\"_blank\" rel=\"noopener\">The Science of Cells That Never Get Old<\/a>.\" Blackburn won a Nobel Prize for her pioneering work on telomeres and telomerase, which may play central roles in how we age.\r\n\r\n<\/div>\r\n<h2><strong>Biochemistry and Aging<\/strong><\/h2>\r\n<h3>Free Radical Theory of Aging<\/h3>\r\n<span style=\"color: #333333;\">The\u00a0<b>free radical <\/b><\/span><b>theory of aging<\/b>\u00a0(<b>FRTA<\/b>) states that organisms\u00a0age\u00a0because cells accumulate\u00a0free radical\u00a0damage over time.\u00a0A free radical is any atom or moleculewhich\u00a0has a single unpaired electron in an outer shell.\u00a0This means that as\u00a0oxygen is\u00a0metabolized, mitochondria in the cells convert the\u00a0oxygen to adenosine triphosphate (ATP) which provides energy to the cell.\u00a0Unpaired electrons are a byproduct of this process and these unstable electrons cause cellular damage as they find other electrons with which to bond.\u00a0These free radicals have some benefits and are used by the immune system to destroy bacteria.\u00a0However, cellular\u00a0damage accumulates and eventually reduces functioning of organs and systems.\u00a0Many food products and vitamin supplements are promoted as age-reducing.\u00a0Antioxidant drugs have been shown to increase the longevity in nematodes (small worms), but the ability to slow the aging process by introducing antioxidants in the diet is still controversial.\r\n\r\n[caption id=\"attachment_2782\" align=\"aligncenter\" width=\"479\"]<img class=\"wp-image-2782\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/3707\/2019\/01\/27032936\/Free-radicals-oxygen-1.jpg\" alt=\"A free radical diagram showing the nucleus with surrounding electrons. The electrons are in pairs on the orbital, and one election is missing a paired partner.\" width=\"479\" height=\"382\" \/> <strong>Figure 2<\/strong>. In chemistry, a\u00a0free radical\u00a0is any atom, molecule, or ion with an unpaired valence electron[\/caption]\r\n<h3>Protein Crosslinking<\/h3>\r\nThis theory focuses on the role blood sugar, or glucose, plays in the aging of cells.\u00a0Glucose molecules attach themselves to proteins and form chains or crosslinks.\u00a0These crosslinks reduce the flexibility of tissue and\u00a0thus it\u00a0becomes stiff and loses functioning.\u00a0The\u00a0circulatory system becomes less efficient as the tissue of the heart, arteries and lungs lose flexibility.\u00a0Joints grow stiff as glucose combines with collegen.\r\n<h3>DNA Damage<\/h3>\r\nThrough the normal\u00a0growth and aging process, DNA is damaged by environmental factors such as toxic agents, pollutants, and sun exposure (Dollemore, 2006). This results in deletions of genetic material, and mutations in the DNA duplicated in new cells.\u00a0The\u00a0accumulation of these errors results in reduced functioning in cells and tissues.\u00a0Theories that suggest that the body\u2019s DNA genetic code contains a built-in time limit for the reproduction of human cells are called the genetic programming theories of aging. These theories promote the view that the cells of the body can only duplicate a certain number of times and that the genetic instructions for running the body can be read only a certain number of times before they become illegible.\u00a0Such theories also promote the existence of a \u201cdeath gene\u201d\u00a0which is programmed to direct the body to deteriorate and die, and\u00a0the idea that a long life after the reproductive years is unnecessary for the survival of the species.[footnote]Kunlin, Jin. (2010). Modern Biological Theories Of Aging. Aging Dis. 2010 Oct; 1(2): 72\u201374. Published online 2010 Aug 1. PMCID: PMC2995895 NIHMSID: NIHMS248183 PMID: 21132086.[\/footnote]\r\n<h3><strong>Decline in the Immune System<\/strong><\/h3>\r\nAs we age, B-lymphocytes and T-lymphocytes become less active.\u00a0These cells are crucial to\u00a0the immune system as they secrete antibodies and directly attack infected cells.\u00a0The\u00a0thymus, where T-cells are manufactured, shrinks as aging progresses. This reduces our body's ability to fight infection (Berger, 2005).\r\n<div class=\"textbox tryit\">\r\n<h3>Try It<\/h3>\r\nhttps:\/\/assess.lumenlearning.com\/practice\/c2b4d4b2-9178-45ed-a95b-e2a5ad3e1016\r\n\r\n<\/div>\r\n<div class=\"textbox key-takeaways\">\r\n<h3>Glossary<\/h3>\r\n[glossary-page]\r\n[glossary-term]free radical theory of aging (FRTA):[\/glossary-term]\r\n[glossary-definition]theory that organisms age because cells accumulate free radical damage over time[\/glossary-definition]\r\n\r\n[glossary-term]generalized slowing hypothesis:[\/glossary-term]\r\n[glossary-definition]the theory that processing in all parts of the nervous system, including the brain, is less efficient[\/glossary-definition]\r\n\r\n[glossary-term]Hayflick limit:[\/glossary-term]\r\n[glossary-definition]the number of times a normal human cell population will divide before cell division stops[\/glossary-definition]\r\n\r\n[glossary-term]peripheral slowing hypothesis:[\/glossary-term]\r\n[glossary-definition]the theory that overall processing speed declines with age in the peripheral nervous system[\/glossary-definition]\r\n[\/glossary-page]\r\n\r\n<\/div>","rendered":"<div class=\"textbox learning-objectives\">\n<h3>Learning Outcomes<\/h3>\n<ul>\n<li>Describe and compare theories of aging<\/li>\n<\/ul>\n<\/div>\n<div id=\"attachment_3549\" style=\"width: 586px\" class=\"wp-caption alignright\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-3549\" class=\"wp-image-3549\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/3707\/2019\/01\/17154431\/man-person-black-and-white-woman-white-photography-671672-pxhere.com_-1024x683.jpg\" alt=\"older woman smiling\" width=\"576\" height=\"385\" \/><\/p>\n<p id=\"caption-attachment-3549\" class=\"wp-caption-text\"><strong>Figure 1.<\/strong>\u00a0There are several plausible theories as to why aging happens<\/p>\n<\/div>\n<h2>Why do we age?<\/h2>\n<p>There are a number of attempts to explain why we age and many factors that contribute to aging.\u00a0The <strong>peripheral slowing hypothesis<\/strong>\u00a0suggests that overall processing speed declines in the\u00a0peripheral\u00a0nervous system,\u00a0affecting\u00a0the\u00a0brain&#8217;s\u00a0ability to communicate with\u00a0muscles and organs.\u00a0Some of\u00a0the peripheral nervous system (PNS) is under\u00a0a person&#8217;s voluntary control, such as the nerves\u00a0carrying instructions from\u00a0the\u00a0brain to\u00a0the limbs. As well as controlling\u00a0muscles and joints, the PNS sends all the information from\u00a0\u00a0the\u00a0senses back to\u00a0the\u00a0brain.<\/p>\n<p>The <strong>generalized slowing hypothesis<\/strong>\u00a0theory\u00a0suggests that\u00a0processing in all parts of the nervous system, including the brain, are less efficient with age.\u00a0This may be\u00a0why older people have more accidents. Genetics, diet, lifestyle, activity, and exposure to pollutants all play a role in the aging process.<a class=\"footnote\" title=\"Plude, D. J., &amp; Doussard-Roosevelt, J. A. (1989). Aging, selective attention, and feature integration. Psychology and Aging, 4(1), 98-105.\" id=\"return-footnote-1513-1\" href=\"#footnote-1513-1\" aria-label=\"Footnote 1\"><sup class=\"footnote\">[1]<\/sup><\/a><a class=\"footnote\" title=\"NCBI Bookshelf. A service of the National Library of Medicine, National Institutes of Health. Murray MM, Wallace MT, editors\" id=\"return-footnote-1513-2\" href=\"#footnote-1513-2\" aria-label=\"Footnote 2\"><sup class=\"footnote\">[2]<\/sup><\/a><a class=\"footnote\" title=\"The Neural Bases of Multisensory Processes. Boca Raton (FL): CRC Press\/Taylor &amp; Francis; 2012. Chapter 20Multisensory Integration and Aging Authors Jennifer L. Mozolic, Christina E. Hugenschmidt, Ann M. Peiffer, and Paul J. Laurienti.\" id=\"return-footnote-1513-3\" href=\"#footnote-1513-3\" aria-label=\"Footnote 3\"><sup class=\"footnote\">[3]<\/sup><\/a><\/em><\/p>\n<p><strong>Cell Life\u00a0<\/strong><\/p>\n<p>Cells divide a limited number of times<span style=\"color: #333333;\"> and then stop. This\u00a0phenomenon, known as the\u00a0<strong>Hayflick limit<\/strong>,\u00a0is evidenced in cells studied in test tubes which divide about 50 times before becoming senescent.\u00a0In 1961, Dr.\u00a0Hayflick\u00a0theorized that\u00a0the human cell&#8217;s ability to divide is limited to approximately 50-times, after which they simply stop dividing (the\u00a0Hayflick limit theory of aging). According to telomere\u00a0theory, telomeres have experimentally been shown to shorten with each successive cell division.<a class=\"footnote\" title=\"Jin K. (2010). Modern Biological Theories of Aging. Aging and disease, 1(2), 72\u201374.\" id=\"return-footnote-1513-4\" href=\"#footnote-1513-4\" aria-label=\"Footnote 4\"><sup class=\"footnote\">[4]<\/sup><\/a><\/span><\/p>\n<p>Senescent cells do not die.\u00a0They simply stop replicating.\u00a0Senescent cells can help limit the growth of other cells which may reduce risk of developing tumors when younger, but can alter genes later in life and result in promoting the growth of tumors as we age (Dollemore, 2006).\u00a0Limited cell growth is attributed to\u00a0telomeres\u00a0which are the tips of the protective coating around chromosomes.\u00a0Each time cells replicate, the telomere is shortened.\u00a0Eventually, loss of telomere length is thought to create damage to chromosomes and produce cell senescence.<\/p>\n<div class=\"textbox exercises\">\n<h3>Link to Learning<\/h3>\n<p>Watch this Ted talk by molecular biologist Elizabeth Blackburn on &#8220;<a href=\"https:\/\/www.ted.com\/talks\/elizabeth_blackburn_the_science_of_cells_that_never_get_old\" target=\"_blank\" rel=\"noopener\">The Science of Cells That Never Get Old<\/a>.&#8221; Blackburn won a Nobel Prize for her pioneering work on telomeres and telomerase, which may play central roles in how we age.<\/p>\n<\/div>\n<h2><strong>Biochemistry and Aging<\/strong><\/h2>\n<h3>Free Radical Theory of Aging<\/h3>\n<p><span style=\"color: #333333;\">The\u00a0<b>free radical <\/b><\/span><b>theory of aging<\/b>\u00a0(<b>FRTA<\/b>) states that organisms\u00a0age\u00a0because cells accumulate\u00a0free radical\u00a0damage over time.\u00a0A free radical is any atom or moleculewhich\u00a0has a single unpaired electron in an outer shell.\u00a0This means that as\u00a0oxygen is\u00a0metabolized, mitochondria in the cells convert the\u00a0oxygen to adenosine triphosphate (ATP) which provides energy to the cell.\u00a0Unpaired electrons are a byproduct of this process and these unstable electrons cause cellular damage as they find other electrons with which to bond.\u00a0These free radicals have some benefits and are used by the immune system to destroy bacteria.\u00a0However, cellular\u00a0damage accumulates and eventually reduces functioning of organs and systems.\u00a0Many food products and vitamin supplements are promoted as age-reducing.\u00a0Antioxidant drugs have been shown to increase the longevity in nematodes (small worms), but the ability to slow the aging process by introducing antioxidants in the diet is still controversial.<\/p>\n<div id=\"attachment_2782\" style=\"width: 489px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-2782\" class=\"wp-image-2782\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/3707\/2019\/01\/27032936\/Free-radicals-oxygen-1.jpg\" alt=\"A free radical diagram showing the nucleus with surrounding electrons. The electrons are in pairs on the orbital, and one election is missing a paired partner.\" width=\"479\" height=\"382\" \/><\/p>\n<p id=\"caption-attachment-2782\" class=\"wp-caption-text\"><strong>Figure 2<\/strong>. In chemistry, a\u00a0free radical\u00a0is any atom, molecule, or ion with an unpaired valence electron<\/p>\n<\/div>\n<h3>Protein Crosslinking<\/h3>\n<p>This theory focuses on the role blood sugar, or glucose, plays in the aging of cells.\u00a0Glucose molecules attach themselves to proteins and form chains or crosslinks.\u00a0These crosslinks reduce the flexibility of tissue and\u00a0thus it\u00a0becomes stiff and loses functioning.\u00a0The\u00a0circulatory system becomes less efficient as the tissue of the heart, arteries and lungs lose flexibility.\u00a0Joints grow stiff as glucose combines with collegen.<\/p>\n<h3>DNA Damage<\/h3>\n<p>Through the normal\u00a0growth and aging process, DNA is damaged by environmental factors such as toxic agents, pollutants, and sun exposure (Dollemore, 2006). This results in deletions of genetic material, and mutations in the DNA duplicated in new cells.\u00a0The\u00a0accumulation of these errors results in reduced functioning in cells and tissues.\u00a0Theories that suggest that the body\u2019s DNA genetic code contains a built-in time limit for the reproduction of human cells are called the genetic programming theories of aging. These theories promote the view that the cells of the body can only duplicate a certain number of times and that the genetic instructions for running the body can be read only a certain number of times before they become illegible.\u00a0Such theories also promote the existence of a \u201cdeath gene\u201d\u00a0which is programmed to direct the body to deteriorate and die, and\u00a0the idea that a long life after the reproductive years is unnecessary for the survival of the species.<a class=\"footnote\" title=\"Kunlin, Jin. (2010). Modern Biological Theories Of Aging. Aging Dis. 2010 Oct; 1(2): 72\u201374. Published online 2010 Aug 1. PMCID: PMC2995895 NIHMSID: NIHMS248183 PMID: 21132086.\" id=\"return-footnote-1513-5\" href=\"#footnote-1513-5\" aria-label=\"Footnote 5\"><sup class=\"footnote\">[5]<\/sup><\/a><\/p>\n<h3><strong>Decline in the Immune System<\/strong><\/h3>\n<p>As we age, B-lymphocytes and T-lymphocytes become less active.\u00a0These cells are crucial to\u00a0the immune system as they secrete antibodies and directly attack infected cells.\u00a0The\u00a0thymus, where T-cells are manufactured, shrinks as aging progresses. This reduces our body&#8217;s ability to fight infection (Berger, 2005).<\/p>\n<div class=\"textbox tryit\">\n<h3>Try It<\/h3>\n<p>\t<iframe id=\"assessment_practice_c2b4d4b2-9178-45ed-a95b-e2a5ad3e1016\" class=\"resizable\" src=\"https:\/\/assess.lumenlearning.com\/practice\/c2b4d4b2-9178-45ed-a95b-e2a5ad3e1016?iframe_resize_id=assessment_practice_id_c2b4d4b2-9178-45ed-a95b-e2a5ad3e1016\" frameborder=\"0\" style=\"border:none;width:100%;height:100%;min-height:300px;\"><br \/>\n\t<\/iframe><\/p>\n<\/div>\n<div class=\"textbox key-takeaways\">\n<h3>Glossary<\/h3>\n<div class=\"titlepage\">\n<dl>\n<dt>free radical theory of aging (FRTA):<\/dt>\n<dd>theory that organisms age because cells accumulate free radical damage over time<\/dd>\n<dt>generalized slowing hypothesis:<\/dt>\n<dd>the theory that processing in all parts of the nervous system, including the brain, is less efficient<\/dd>\n<dt>Hayflick limit:<\/dt>\n<dd>the number of times a normal human cell population will divide before cell division stops<\/dd>\n<dt>peripheral slowing hypothesis:<\/dt>\n<dd>the theory that overall processing speed declines with age in the peripheral nervous system<\/dd>\n<\/dl>\n<\/div>\n<\/div>\n\n\t\t\t <section class=\"citations-section\" role=\"contentinfo\">\n\t\t\t <h3>Candela Citations<\/h3>\n\t\t\t\t\t <div>\n\t\t\t\t\t\t <div id=\"citation-list-1513\">\n\t\t\t\t\t\t\t <div class=\"licensing\"><div class=\"license-attribution-dropdown-subheading\">CC licensed content, Original<\/div><ul class=\"citation-list\"><li>Modification, adaptation, and original content. <strong>Authored by<\/strong>: Sonja Ann Miller for Lumen Learning. <strong>Provided by<\/strong>: Lumen Learning. <strong>License<\/strong>: <em><a target=\"_blank\" rel=\"license\" href=\"https:\/\/creativecommons.org\/licenses\/by-sa\/4.0\/\">CC BY-SA: Attribution-ShareAlike<\/a><\/em><\/li><\/ul><div class=\"license-attribution-dropdown-subheading\">CC licensed content, Shared previously<\/div><ul class=\"citation-list\"><li>Psyc 200 Lifespan Psychology. <strong>Authored by<\/strong>: Laura Overstreet. <strong>Located at<\/strong>: <a target=\"_blank\" href=\"http:\/\/opencourselibrary.org\/econ-201\/\">http:\/\/opencourselibrary.org\/econ-201\/<\/a>. <strong>License<\/strong>: <em><a target=\"_blank\" rel=\"license\" href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/\">CC BY: Attribution<\/a><\/em><\/li><li>Free radical theory of agin. <strong>Provided by<\/strong>: Wikipedia. <strong>Located at<\/strong>: <a target=\"_blank\" href=\"https:\/\/en.wikipedia.org\/wiki\/Free-radical_theory_of_aging\">https:\/\/en.wikipedia.org\/wiki\/Free-radical_theory_of_aging<\/a>. <strong>License<\/strong>: <em><a target=\"_blank\" rel=\"license\" href=\"https:\/\/creativecommons.org\/licenses\/by-sa\/4.0\/\">CC BY-SA: Attribution-ShareAlike<\/a><\/em><\/li><li>Free radicals diagram. <strong>Authored by<\/strong>: Healthvalue. <strong>Provided by<\/strong>: Wikipedia. <strong>Located at<\/strong>: <a target=\"_blank\" href=\"https:\/\/en.wikipedia.org\/wiki\/Free-radical_theory_of_aging#\/media\/File:Free-radicals-oxygen.jpg\">https:\/\/en.wikipedia.org\/wiki\/Free-radical_theory_of_aging#\/media\/File:Free-radicals-oxygen.jpg<\/a>. <strong>License<\/strong>: <em><a target=\"_blank\" rel=\"license\" href=\"https:\/\/creativecommons.org\/licenses\/by-sa\/4.0\/\">CC BY-SA: Attribution-ShareAlike<\/a><\/em><\/li><li><strong>Provided by<\/strong>: pxhere. <strong>Located at<\/strong>: <a target=\"_blank\" href=\"https:\/\/pxhere.com\/en\/photo\/671672\">https:\/\/pxhere.com\/en\/photo\/671672<\/a>. <strong>License<\/strong>: <em><a target=\"_blank\" rel=\"license\" href=\"https:\/\/creativecommons.org\/about\/cc0\">CC0: No Rights Reserved<\/a><\/em><\/li><\/ul><\/div>\n\t\t\t\t\t\t <\/div>\n\t\t\t\t\t <\/div>\n\t\t\t <\/section><hr class=\"before-footnotes clear\" \/><div class=\"footnotes\"><ol><li id=\"footnote-1513-1\">Plude, D. J., &amp; Doussard-Roosevelt, J. A. (1989). <em>Aging, selective attention, and feature integration. Psychology and Aging, 4(1), 98-105. <a href=\"#return-footnote-1513-1\" class=\"return-footnote\" aria-label=\"Return to footnote 1\">&crarr;<\/a><\/li><li id=\"footnote-1513-2\">NCBI Bookshelf. A service of the National Library of Medicine, National Institutes of Health. Murray MM, Wallace MT, editors <a href=\"#return-footnote-1513-2\" class=\"return-footnote\" aria-label=\"Return to footnote 2\">&crarr;<\/a><\/li><li id=\"footnote-1513-3\">The Neural Bases of Multisensory Processes. Boca Raton (FL): CRC Press\/Taylor &amp; Francis; 2012. Chapter 20Multisensory Integration and Aging Authors Jennifer L. Mozolic, Christina E. Hugenschmidt, Ann M. Peiffer, and Paul J. Laurienti. <a href=\"#return-footnote-1513-3\" class=\"return-footnote\" aria-label=\"Return to footnote 3\">&crarr;<\/a><\/li><li id=\"footnote-1513-4\">Jin K. (2010). Modern Biological Theories of Aging. Aging and disease, 1(2), 72\u201374. <a href=\"#return-footnote-1513-4\" class=\"return-footnote\" aria-label=\"Return to footnote 4\">&crarr;<\/a><\/li><li id=\"footnote-1513-5\">Kunlin, Jin. (2010). Modern Biological Theories Of Aging. Aging Dis. 2010 Oct; 1(2): 72\u201374. Published online 2010 Aug 1. PMCID: PMC2995895 NIHMSID: NIHMS248183 PMID: 21132086. <a href=\"#return-footnote-1513-5\" class=\"return-footnote\" aria-label=\"Return to footnote 5\">&crarr;<\/a><\/li><\/ol><\/div>","protected":false},"author":29,"menu_order":7,"template":"","meta":{"_candela_citation":"[{\"type\":\"cc\",\"description\":\"Psyc 200 Lifespan Psychology\",\"author\":\"Laura Overstreet\",\"organization\":\"\",\"url\":\"http:\/\/opencourselibrary.org\/econ-201\/\",\"project\":\"\",\"license\":\"cc-by\",\"license_terms\":\"\"},{\"type\":\"original\",\"description\":\"Modification, adaptation, and original content\",\"author\":\"Sonja Ann Miller for Lumen Learning\",\"organization\":\"Lumen Learning\",\"url\":\"\",\"project\":\"\",\"license\":\"cc-by-sa\",\"license_terms\":\"\"},{\"type\":\"cc\",\"description\":\"Free radical theory of agin\",\"author\":\"\",\"organization\":\"Wikipedia\",\"url\":\"https:\/\/en.wikipedia.org\/wiki\/Free-radical_theory_of_aging\",\"project\":\"\",\"license\":\"cc-by-sa\",\"license_terms\":\"\"},{\"type\":\"cc\",\"description\":\"Free radicals diagram\",\"author\":\"Healthvalue\",\"organization\":\"Wikipedia\",\"url\":\"https:\/\/en.wikipedia.org\/wiki\/Free-radical_theory_of_aging#\/media\/File:Free-radicals-oxygen.jpg\",\"project\":\"\",\"license\":\"cc-by-sa\",\"license_terms\":\"\"},{\"type\":\"cc\",\"description\":\"\",\"author\":\"\",\"organization\":\"pxhere\",\"url\":\"https:\/\/pxhere.com\/en\/photo\/671672\",\"project\":\"\",\"license\":\"cc0\",\"license_terms\":\"\"}]","CANDELA_OUTCOMES_GUID":"6d7e596d-5dd2-4023-9b5f-0157372d4326, 3b1a4160-ffdc-4f78-ba16-3c1e22e5be9f","pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":""},"chapter-type":[],"contributor":[],"license":[],"class_list":["post-1513","chapter","type-chapter","status-publish","hentry"],"part":372,"_links":{"self":[{"href":"https:\/\/courses.lumenlearning.com\/wm-lifespandevelopment\/wp-json\/pressbooks\/v2\/chapters\/1513","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/courses.lumenlearning.com\/wm-lifespandevelopment\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/courses.lumenlearning.com\/wm-lifespandevelopment\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/wm-lifespandevelopment\/wp-json\/wp\/v2\/users\/29"}],"version-history":[{"count":31,"href":"https:\/\/courses.lumenlearning.com\/wm-lifespandevelopment\/wp-json\/pressbooks\/v2\/chapters\/1513\/revisions"}],"predecessor-version":[{"id":7852,"href":"https:\/\/courses.lumenlearning.com\/wm-lifespandevelopment\/wp-json\/pressbooks\/v2\/chapters\/1513\/revisions\/7852"}],"part":[{"href":"https:\/\/courses.lumenlearning.com\/wm-lifespandevelopment\/wp-json\/pressbooks\/v2\/parts\/372"}],"metadata":[{"href":"https:\/\/courses.lumenlearning.com\/wm-lifespandevelopment\/wp-json\/pressbooks\/v2\/chapters\/1513\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/courses.lumenlearning.com\/wm-lifespandevelopment\/wp-json\/wp\/v2\/media?parent=1513"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/wm-lifespandevelopment\/wp-json\/pressbooks\/v2\/chapter-type?post=1513"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/wm-lifespandevelopment\/wp-json\/wp\/v2\/contributor?post=1513"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/wm-lifespandevelopment\/wp-json\/wp\/v2\/license?post=1513"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}