Hockenbury Discovering Psychology 5th txtbk

Enhancing Well-Being with Psychology81ENHANCING WELL-BEING WITH PSYCHOLOGYMaximizing Your Brain's PotentialIt was 1962 when a group of neuroscientists led by psychologistMark Rosenzweig published the unexpected finding thatthe brains of rats raised in enriched environments were significantlydifferent from the brains of rats raised in impoverishedenvironments.For lab rats, an enriched environment is spacious, houses severalrats, and has assorted wheels, ladders, tunnels, and objects to explore.The environment is also regularly changed for further variety.Some enriched environments have been designed to mimic ananimal’s natural environment (see Heyman, 2003). In the impoverishedenvironment, a solitary rat lives in a small, bare laboratorycage with only a water bottle and food tray to keep it company.Decades of research have shown that enrichment increasesthe number and length of dendrites and dendritic branches, increasesthe number of glial cells, and enlarges the size of neurons(Cohen, 2003). Enrichment produces more synaptic connectionsbetween brain neurons, while impoverishmentdecreases synaptic connections. With more synapses, the brainhas a greater capacity to integrate and process information andto do so more quickly. In young rats, enrichment increases thenumber of synapses in the cortex by as much as 20 percent. Buteven the brains of extremely old rats respond to enriched environments.In fact, no matter what the age of the rats studied,environmental enrichment or impoverishment had a significantimpact on brain structure (Kempermann & others, 1998).Enrichment has also been shown to increase the rate ofneurogenesis in many different species, from rodents to monkeys(Fan & others, 2007; Nithianantharajah & Hannan, 2006).Both the number and the survival time of new neurons increasein response to enrichment (Gould & Gross, 2002; van Praag &others, 2000). Interestingly, while enriched environments can increaseneurogenesis, social isolation and a stressful environmentdecrease neurogenesis (Ming & Song, 2005).Collectively, these changes result in increased processing andcommunication capacity in the brain. Behaviorally, enrichmenthas been shown to enhance performance on tasks designed tomeasure learning and memory, such as performance in differenttypes of mazes (van Praag & others, 2000).Who Moved My Exercise Wheel?Neuroscientists have identified an additional factor that improvesbrain function, even in aging mammals: exercise (see Hillman &others, 2008). In one study, just a month of daily exercise helpedreverse cognitive declines associated with aging in previouslysedentary, elderly mice (van Praag & others, 2005). After havingaccess to an exercise wheel for 30 days, mice that were the rodentequivalent of 70 years old learned to navigate a maze muchfaster than mice of the same age that did not exercise. They alsohad better memories of maze locations. Finally, the physically activeelderly mice had a greatly increased rate of neurogenesis,and the new neurons functioned as well as new neurons generatedin the brains of young mice. As study co-author Henriettevan Praag (2005) points out, “Our findings show that it is nevertoo late in life to start to exercise, and that doing so will likelydelay the onset of aging-associated memory loss.”An Enriched Environment Primates in the wild live in complex,challenging, and ever-changing environments. At psychologistElizabeth Gould’s Princeton lab, marmosets are housed in largeenclosures with natural vegetation and novel objects that arechanged frequently. To encourage naturalistic foraging, brancheswith holes are filled with dried fruit and live worms. In oneexperiment, synaptic and dendritic connections increased dramaticallyin marmosets who lived in the enriched environmentfor just four weeks after being raised in standard laboratorycages (Kozorovitskiy & others, 2004).From Animal Studies to HumansEnrichment studies have been carried out with many otherspecies, including monkeys, cats, birds, honeybees, and evenfruit flies. In all cases, enriched environments are associated withstriking changes in the brain, however primitive.Can the conclusions drawn from studies on rats, monkeys, andother animals be applied to human brains? Obviously, researcherscannot directly study the effects of enriched or impoverished environmentson human brain tissue as they can with rats.Consider a study conducted by Ana Pereira and her colleagues(2007). Male and female participants, aged 21 to 45, were assessedfor their overall level of fitness. Using MRI scans, eachparticipant’s brain was also mapped for amount of blood flowinginto the hippocampus. Over the next three months, theparticipants worked out for one hour four times a week. Finally,the same physical and brain measurements were taken again.As you probably anticipated, all of the participants had significantlyimproved their overall level of aerobic fitness. More importantly,they had also substantially increased the blood flow totheir hippocampuses, in some cases doubling the blood flow asmeasured prior to the exercise program. In general, the greaterthe increase in a participant’s aerobic fitness, the greater the increasein blood flow to the hippocampus.