Effects Of Adult Aging On Inhibitory Functions And Divided Attention

Aging is a biological process that results in developmental changes throughout a person’s life. During adolescence for example, neurons in the frontal lobe undergo a period of increased myelination resulting in enhanced attentional abilities and greater control over impulsive behavior (Giedd, 1999).

However, later in life, such as during late adulthood, aging can have the opposite effect on the frontal lobes by decreasing neuronal tissue and causing cognitive decline (Arbuckle and Gold, 1993).

Inhibitory Deficit And Divided Attention

Older adults tend to find it more difficult focusing their attention on stimuli which are significant to them and ignoring stimuli which are not significant to them than younger adults do (Butler and Zacks, 2006).

The inhibitory deficit model proposes that this may occur due to inefficient inhibition of non relevant information entering working memory, which subsequently causes interference with relevant information (Erber, 2010).

This can result in a deterioration of cognitive abilities such as language comprehension. For example, older adults tend to find it more difficult to focus on one voice when many are speaking (Pichora-Fuller, Schneider and Daneman, 1995) or to focus on the words in a book when there are other surrounding distractions, which may in turn decrease the speed at which they process information (Connelly, Hasher and Zacks, 1991).

However, such effects tend to occur predominantly during periods of intense mental activity when there are lots of surrounding distractions, but less so during periods of lower mental activity and when there are not many distractions present (Gazzaley, Sheridan, Cooney and D’Esposito, 2007).

In the later scenario, research carried out by Somberg and Salthouse (1982) on divided attention abilities which involve focusing on or processing two or more stimuli at the same time, has shown that older adults perform just as well as younger adults on such tasks.

Reducing distractions and presenting stimuli one at a time may therefore help to overcome this inhibitory deficit and enhance the information processing abilities of older adults (Lustig, 2006).

Furthermore, studies have also shown that older adults are no worse off when it comes to the recall of episodic memory than younger adults are (Aslan, Bauml and Pastotter, 2007), and that it is possible to improve attention in older adults by changing the way stimuli are focused upon (Levy, Jennings and Langer, 2001).

Such evidence further seems to suggest that age related attentional decline may in fact be due to a lack of inhibitory control.

Frontal Lobe Degeneration

One biological explanation which may account for these findings is the decreased neuronal tissue found in the frontal lobe of the older adult brain.

This is significant because in adults, frontal lobe activation tends to maximally occur when there are many stimuli to process (Durston, Thomas, Yang, Zimmerman and Casey, 2002).

Therefore, if the older adult frontal lobe is functionally impaired as a result of neuronal decline, this may explain why older adults tend to perform poorly on complex divided attention tasks.

Studies carried out on individuals with frontal lobe damage do seem to support this assertion (Floden and Stuss, 2006).

However, the fact that older adults are able to perform complex divided attention activities, such as driving a car whilst speaking on a phone, suggests that the plasticity of the brain allows new brain regions to be used for such tasks (Fassbender and Schweitzer, 2006).

Although, since this “rewiring” of the brain does not occur instantly, older adults will most likely experience a longer adaptation period before they are able to perform simultaneous complex tasks proficiently.

References

Arbuckle, T.Y., & Gold, D.P. (1993). Aging, inhibition, and verbosity. Journal of Gerontology: Psychological Sciences 48, 225-232.

Aslan, A., Bauml, K.H., & Pastotter, B. (2007). No inhibitory deficit in older adults’ episodic memory. Psychological Science 18, 72-78.

Butler, M.K., & Zacks, R.T. (2006). Age Deficits in the control of prepotent responses: Evidence for an inhibitory decline. Psychology and Aging 21, 638–643.

Connelly, S.L., Hasher, L., & Zacks, R.T. (1991). Age and reading: The impact of distraction. Psychology and Aging 6, 533–541.

Durston, S., Thomas, K.M., Yang, Y.A.M., Zimmerman, R.D., & Casey, B.J. (2002). A neural basis for the development of inhibitory control. Developmental Science 5, 9–16.

Erber, J.T. (2010). Aging and Older Adulthood (2nd edition). Wiley-Blackwell.

Fassbender, C., & Schweitzer, J.B. (2006). Is there evidence for neural compensation in attention deficit hyperactivity disorder? Clinical Psychology 26, 445-465.

Floden, D., & Stuss, D.T. (2006). Inhibitory control is slowed in patients with right superior medial frontal damage. Journal of Cognitive Neuroscience 18, 1843-1849.

Gazzaley, A., Sheridan, M.A., Cooney, J.W., & D’Esposito, M. (2007). Age-related deficits in component processes of working memory. Neuropsychology 21, 532–539.

Giedd, J.N. (1999). Brain Development during childhood and adolescence: a longitudinal MRI study. Nature Neuroscience 2, 861–863.

Levy, B.R., Jennings, P., & Langer, E.J. (2001). Improving Attention in Old Age. Journal of Adult Development 8, 189-192.

Lustig, C. (2006). Distraction as a determinant of processing speed. Psychonomic Bulletin & Review 13, 619-625.

Pichora-Fuller, M.K., Schneider, B.A., & Daneman, M. (1995). How young and old adults listen to and remember speech in noise. Journal of the Acoustical Society of America 97, 593–608.

Somberg, B.L., & Salthouse, T.A. (1982). Divided attention abilities in young and old adults. Journal of Experimental Psychology: Human Perception and Performance 8, 651-663.