Today we have the plea­sure to have Dr. Pas­cale Mich­e­lon, one of our new Expert Con­trib­u­tors, write her first arti­cle here. Enjoy, and please com­ment so we hear your thoughts and engage in a nice conversation.

(Btw, if you notice some sim­i­lar­ity between the col­ors in the fMRI scan below and the look & feel of this site…well, the rea­son is that those orange-grey fMRI col­ors were our inspi­ra­tion! the orange color denotes the most brain activation).

- Alvaro

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You have prob­a­bly heard about CAT and MRI scans (pro­duced thanks to machines like the one to the top right). So you know that these are tech­niques that doc­tors and sci­en­tists use to look inside the brain.

You have prob­a­bly also heard about brain fit­ness and how impor­tant it is to keep a healthy brain to be pro­tected against age-related and disease-related brain damages.

The ques­tion we ask here is the fol­low­ing: Can we use brain scans to eval­u­ate how fit the brain is? Before we try to answer this ques­tion let’s start with the basics and try to under­stand how brain scans work.

Brain imag­ing, also called neu­roimag­ing, allows one to pro­duce images of the brain. There are dif­fer­ent types of brain imag­ing: struc­tural and func­tional. Struc­tural imag­ing pro­vides infor­ma­tion about the shape and vol­ume of the brain (CAT and MRI scans). Func­tional imag­ing shows the brain cells that are active when one per­forms a spe­cific task (fMRI and PET scans).

CT or CAT scans. Com­puted tomog­ra­phy or com­puted axial tomog­ra­phy is a tech­nique that takes a large num­ber of two-dimensional X-rays images. These images are used to dig­i­tally com­pute 3D images of the inside of the brain. The most fre­quent rea­son for a head CT is to diag­nose cere­brovas­cu­lar acci­dents and intracra­nial hem­or­rhage. It is also often use to eval­u­ate facial and skull fractures.

MRI scans. MRI stands for Mag­netic Res­o­nance Imag­ing. This tech­nique uses mag­netic fields and radio waves to gen­er­ate 2– or 3-D images of the brain. MRI is used to detect tumors and other patholo­gies that affect the tis­sues of the brain (e.g., mul­ti­ple scle­ro­sis). Com­pared to CT, it is more pre­cise and harm­less to the patient (no poten­tially dan­ger­ous X-rays). How­ever, CT is much cheaper and more widely used.

PET scans. PET stands for Positron Emis­sion Tomog­ra­phy. It mea­sures the emis­sion gen­er­ated by a short-lived radioac­tive tracer injected to the patient (using the blood­stream). The 2– or 3-D images pro­duced show brain activ­ity. PET is used to detect tumors and for the diag­no­sis of brain dis­eases. Since the 1990s, fMRI has sup­planted PET due to its low inva­sive­ness, lack of radi­a­tion expo­sure, and rel­a­tively wide availability.

fMRI scans. Func­tional Mag­netic Res­o­nance Imag­ing relies on the mag­netic prop­er­ties of oxy­genated and deoxy­genated hemo­glo­bin. This tech­nique pro­duces images of chang­ing blood flow in the brain asso­ci­ated with neural activ­ity. The images show the brain struc­tures acti­vated dur­ing per­for­mance of dif­fer­ent tasks. fMRI is used to detect early changes in the brain fol­low­ing strokes or other brain diseases.

What is brain reserve?

Now you know about imag­ing tech­niques. Our goal was to see whether we could use these tech­niques to eval­u­ate whether a brain is fit or not. Fit brains are brains that have what sci­en­tists call cog­ni­tive brain reserve. It is more or less the capac­ity of the brain to resist the expres­sion of symp­toms in the face of exist­ing neu­ropathol­ogy. In other words, peo­ple with more cog­ni­tive brain reserve can tol­er­ate more patho­logic changes before they show any symp­toms. If you have healthy brain, that is if you have cog­ni­tive reserve, you will still get older and you may still get Alzheimer dis­ease. But brain reserve will help delay­ing the effects of age and the onset of demen­tia. You may be won­der­ing: “What can I do to get some cog­ni­tive reserve? Here are 2 fac­tors that seem crucial:

- Edu­ca­tion (see Snow­don et al., 1989 or Katz­man, 1993)

- Level of intel­lec­tual stim­u­la­tion (through your job or your leisure activ­i­ties) (see Scarmeas et al., 2001; Vergh­ese et al., 2003)

It looks like edu­ca­tion or intel­lec­tual stim­u­la­tion may increase brain reserve by increas­ing the den­sity of the con­nec­tions between brain cells (that is by increas­ing synapses between neu­rons). For more info about cog­ni­tive reserve see Alvaro inter­view with researcher Dr. Yaakov Stern.

Can you image brain reserve in the brain?

In a recent study, Perneczky and col­leagues (2006) used PET to explore the effect of cog­ni­tive reserve on Alzheimer’s dis­ease. They scanned the brain of 93 patients with mild Alzheimer’s dis­ease and 16 healthy controls.

It was expected that peo­ple with the more severe Alzheimer’s dis­ease pathol­ogy would show less cere­bral blood flow, that is less activ­ity, in the regions affected by the dis­ease. Remem­ber that blood flow in the brain is what PET measures.

Perneczky hypoth­e­sized that patients with more years of school­ing would have more pro­nounced deficits in regions typ­i­cally affected by the pathol­ogy of Alzheimer’s disease.

How could this be? Didn’t I tell you ear­lier that edu­ca­tion con­tributes to brain reserve?

Here is the rea­son­ing: say that Ms A. has a low level of brain reserve. She has devel­oped Alzheimer’s 2 years ago. She doesn’t have much pathol­ogy in her brain yet and her symp­toms (mem­ory prob­lems, etc.) cor­re­spond to a mild stage of Alzheimer’s dis­ease. Ms B. has a high level of brain reserve. She has devel­oped Alzheimer’s 5 years ago. She has a high level of pathol­ogy in her brain. How­ever, thanks to her brain reserve, she only shows symp­toms cor­re­spond­ing to a mild stage of Alzheimer’s disease.

Results of this PET study show that indeed patients with more edu­ca­tion (such as Ms B.) con­sis­tently had more pro­nounced deficits in regions typ­i­cally affected by the pathol­ogy of Alzheimer’s dis­ease com­pared to patients with less years of school­ing (such as Ms A.)

These find­ings sug­gest that edu­ca­tion is asso­ci­ated with brain reserve and that peo­ple with higher edu­ca­tion can cope with brain dam­age for a longer time.

What if one doesn’t have higher education…Is it too late to build cog­ni­tive brain reserve? The good news is that it is NOT too late! Edu­ca­tion is not the only fac­tor. One can always find ways to get enough men­tal stim­u­la­tion by choos­ing our jobs and engag­ing in leisure activ­i­ties such as read­ing, learn­ing new things, going to muse­ums, etc.

— This arti­cle was writ­ten by Pas­cale Mich­e­lon, Ph. D., for SharpBrains.com. Dr. Mich­e­lon has a Ph.D. in Cog­ni­tive Psy­chol­ogy and has worked as a Research Sci­en­tist at Wash­ing­ton Uni­ver­sity in Saint Louis, in the Psy­chol­ogy Depart­ment. She con­ducted sev­eral research projects to under­stand how the brain makes use of visual infor­ma­tion and mem­o­rizes facts. She is now an Adjunct Fac­ulty at Wash­ing­ton Uni­ver­sity, and teaches Mem­ory Work­shops in numer­ous retire­ment com­mu­ni­ties in the St Louis area.

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