I apol­o­gize for the long delay in get­ting back to this col­umn but I have a good excuse. We just recently had a baby, and boy, that takes care right there of the phys­i­cal exer­cise need. Between car­ry­ing the baby upstairs and down­stairs, run­ning to get the baby, get­ting out of the bed and pick­ing the baby up and putting the baby down a cou­ple of times a night no you need not worry about get­ting your daily exer­cise dose in…Now, the major­ity of the answers to my post on the brain virtues of phys­i­cal exer­cise sug­gests that most peo­ple think that the brain ben­e­fits of phys­i­cal exer­cise are mostly to be under­stood as com­ple­men­tary effects of a healthy life style.

Is this cor­rect? In my post today I will attempt to answer this question.

First, while gen­er­ally health­ier peo­ple seem to have health­ier brains, the phys­i­cal exer­cise effect on the brain seems to be inde­pen­dent of other things. One of the most impor­tant devel­op­ment in neu­ro­science was when the offi­cial dogma claim­ing that there was no neu­ro­ge­n­e­sis (pro­duc­tion of new brain cells) in the adult brain was top­pled. Now we know that the brain is “plas­tic” mean­ing that, under the right cir­cum­stances, the brain can change in terms of both pro­duc­ing new cells and get­ting more cells con­nected to each other.

One of the places where neu­ro­ge­n­e­sis has been shown to occur in the adult brain is the den­tate gyrus, a strip of grey mat­ter placed deep down in the brain. The den­tate gyrus is a part of the hip­pocam­pus, the main mem­ory struc­ture, and has been shown to play a role in the form­ing of new mem­o­ries. What can the den­tate gyrus teach us with regards to phys­i­cal exercise?

Fol­low­ing a series of extremely thought pro­vok­ing exper­i­ments researchers from the Gage lab­o­ra­tory at UCSD con­cluded that exer­cise leads to the pro­duc­tion of new brain cells in the den­tate. First the researchers found that mice housed in an enriched envi­ron­ment (a larger cage with toys, tun­nels, and more oppor­tu­nity for phys­i­cal activ­ity, learn­ing, and social inter­ac­tion than in stan­dard bare cage) have an increased num­ber of new neu­rons in the den­tate gyrus.

The enriched envi­ron­ment is a mice equiv­a­lent of not only healthy but good liv­ing: leisurely enjoy­ing life, get­ting both phys­i­cal and intel­lec­tual stim­u­la­tion, social­iz­ing with friends. Now, the fact that new neu­rons were pro­duced was a big enough news in itself but the Gage group did not stop there. Their next goal was to fig­ure out if neu­ro­ge­n­e­sis was the result of a sum of fac­tors act­ing together (i.e. the enriched envi­ron­ment) ver­sus a spe­cific effect of indi­vid­ual fac­tor. So, they first dis­sected the enriched envi­ron­ment in a num­ber of “sub” envi­ron­ments. In their next exper­i­ment they placed the mice in a “learn­ing envi­ron­ment” where they had access to a maze, a “phys­i­cal exer­cise envi­ron­ment” where mice had unlim­ited access to a run­ning wheel, in addi­tion to enriched and stan­dard (empty cage) envi­ron­ments. Then they com­pared the groups in terms of behav­ioral per­for­mance and even­tu­ally looked at their brains.

Their con­clu­sion was any­thing but expected: while both enrich­ment and wheel run­ning led to improved spa­tial mem­ory func­tion only phys­i­cal exer­cise in a run­ning wheel also pro­moted neu­ro­ge­n­e­sis and enhanced the sur­vival of new­born neu­rons in the den­tate gyrus.

Bot­tom line: exer­cis­ing seems to lit­er­ally mean “exer­cis­ing the brain”.

So, in lieu of con­clu­sion, till next I wish you all happy trails (and I don’t mean it as just trails on the paper in a paper and pen­cil mem­ory task)!

Adrian Preda, M.D. is an Asso­ciate Pro­fes­sor of Psy­chi­a­try and Human Behav­ior in the UC Irvine School of Medicine’s Depart­ment of Psy­chi­a­try and Human Behav­ior. His exper­tise in human behav­ior, psy­chol­ogy and spir­i­tu­al­ity is based on years of expe­ri­ence work­ing as a psy­chi­a­trist, psy­chother­a­pist, teacher and researcher in a vari­ety of aca­d­e­mic clin­i­cal and non-clinical set­tings. He also teaches the UC Irvine Exten­sion class The Mind that Changes the Brain: Well­ness in the Sec­ond Mil­len­nium.
References:

van Praag H, Christie BR, Sejnowski TJ, Gage FH (1999) Run­ning enhances neu­ro­ge­n­e­sis, learn­ing, and long-term poten­ti­a­tion in mice. Proc Natl Acad Sci USA 96: 13427–13431

van Praag H, Kem­per­mann G, Gage FH (1999) Run­ning increases cell pro­lif­er­a­tion and neu­ro­ge­n­e­sis in the adult mouse den­tate gyrus. Nat Neu­rosci 2: 266–270.

Farmer J, Zhao X, van Praag H, Wodtke K, Gage FH, Christie BR (2004) Effects of vol­un­tary exer­cise on synap­tic plas­tic­ity and gene expres­sion in the den­tate gyrus of adult male Sprague-Dawley rats in vivo. Neu­ro­science 124: 71–79

Related read­ing:

- Phys­i­cal Exer­cise and Brain Health

- Art Kramer on Why we Need Walk­ing Book Clubs

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