Many drugs have pow­er­ful ef­fect on brain

The Prince George Citizen - - Science - TODD WHITCOMBE

Our bod­ies are equipped with a mul­ti­tude of sen­sors al­low­ing us to dis­cern dif­fer­ent tem­per­a­tures, feel pain, hear sounds, and dis­tin­guish sub­tle shades of blue, etc. We are con­stantly bom­barded with sen­sory in­for­ma­tion but we only pay at­ten­tion to a small frag­ment of the to­tal in­for­ma­tion. Some philoso­phers, psy­chol­o­gists, and oth­ers study­ing the mind-body prob­lem ar­gue the role of the mind is to sort through the mil­lions of bits of in­for­ma­tion we gen­er­ate with our senses ev­ery se­cond and fig­ure out which are im­por­tant.

In this in­ter­pre­ta­tion, the mind is a sort­ing mech­a­nism which ren­ders in­for­ma­tion such as the touch of your pants leg on the back of your calf as unim­por­tant whereas the shoot­ing pain in your ab­domen means there is some­thing wrong that needs ad­dress­ing.

Per­haps more to the point, the only thing we would no­tice is the shoot­ing pain as our mind races through pos­si­ble al­ter­na­tives and ex­pla­na­tions for its source. Ap­pen­dici­tis? Cramps? Bowel dis­ease? The hot, spicy sausage you had for lunch? While the pain is dom­i­nat­ing our sen­sory in­put it will also be dom­i­nat­ing our thoughts.

Is this a good view of the mind? Per­haps. But it does point out the con­nec­tion we have be­tween our body and our mind. Our sense of our­selves comes from our in­ter­ac­tion with all of the var­i­ous nerves feed­ing in­for­ma­tion into our brain.

Var­i­ous sci­en­tists have ex­per­i­mented with iso­lat­ing a brain from its body.

In­deed, dis­em­bod­ied brains have been fea­tured in sci­ence fic­tion movies since the early 1960s. Un­for­tu­nately, brains with­out bod­ies do not sur­vive. With­out so­matic in­put, the brain shuts down and withers away.

We are in con­stant need of in­put through our sen­sory net­work. But what hap­pens if this sen­sory in­for­ma­tion gets dis­torted or deleted?

Many drugs – le­gal and il­le­gal, nat­u­ral and syn­thetic – al­ter the bio­chem­istry in our brains. For ex­am­ple, se­lec­tive sero­tonin re-up­take in­hibitors (SSRI) do ex­actly what their name im­plies – they se­lec­tively pre­vent the send­ing neu­ron from re­ab­sorb­ing the sero­tonin re­leases into the synap­tic cleft.

That is, a sig­nal trav­els down the axon to the send­ing end of neu­ron. Within the cell, small pack­ages of the neu­ro­trans­mit­ter sero­tonin are bun­dled into vesi­cles. When the sig­nal ar­rives, these sacks com­bine with the cell mem­brane and re­lease their con­tent into the synap­tic cleft. The mol­e­cules dif­fuse across the synapse and trig­ger a re­sponse in the re­ceiv­ing neu­ron – much like in­sert­ing a key into a lock.

The sero­tonin is then re­ab­sorbed by the send­ing neu­ron to be re­cy­cled in a new vesi­cle to await the next sig­nal com­ing down the neu­ron. What SSRI drugs do is to slow or pre­vent the re-up­take of the sero­tonin thereby main­tain­ing ar­ti­fi­cially high lev­els in the space be­tween the neu­rons which then keep ac­ti­vat­ing the re­ceiv­ing neu­ron caus­ing it to send sig­nals.

This is one of sev­eral path­ways by which drugs can mod­ify the pro­cess­ing of sig­nals in our brains. How, when, and where these sorts of in­ter­ac­tions hap­pen can have pro­found ef­fects on our minds.

SSRIs treat de­pres­sion as do monoamine ox­i­dase in­hibitors. The opi­oids mod­ify the sen­sa­tion of pain. Am­phetamines fid­dle with our abil­ity to pay at­ten­tion.

Some drugs, such as LSD and pey­ote, have pro­found ef­fects on many ar­eas of our brain re­sult­ing in hal­lu­ci­na­tions.

The abil­ity to see things which are not ac­tu­ally there is a tes­ta­ment to just how much our minds de­pend on the chem­i­cal clues pro­vided by our senses.

Hal­lu­ci­na­tions re­sult from the hi­jack­ing of neu­ral path­ways.

While some of the in­for­ma­tion on the in­ter­ac­tion of drugs with the hu­man brain has been ob­tained through in­ten­tional and un­in­ten­tional ex­per­i­ments with hu­mans, neuro-sci­en­tists also use an­i­mal mod­els to ex­am­ine the in­ter­ac­tions. How­ever as an­i­mals lack the ca­pac­ity to ar­tic­u­late the ef­fects of the drug, the sci­en­tists ob­serve other phys­i­o­log­i­cal re­sponses such as brain wave pat­terns and res­pi­ra­tory rates.

An­i­mals can also be ob­served solv­ing amaz­ing com­plex prob­lems. Their abil­ity to en­gage in prob­lem solv­ing be­hav­iour while un­der the in­flu­ence of a par­tic­u­lar drug can be mon­i­tored and re­veal some­thing about the com­pound’s ef­fects.

For ex­am­ple, sci­en­tists at John Hop­kins have been study­ing the ef­fect of MDMA, known as ec­stasy, on oc­to­puses. Oc­to­puses have a com­plex ner­vous sys­tem and are able to use tools or nav­i­gate mazes while solv­ing in­tri­cate prob­lems. But they are not very cud­dly an­i­mals in­clined to close phys­i­cal con­tact.

How­ever, know­ing we share sim­i­lar bio­chem­i­cal hard­ware, the sci­en­tists were in­ter­ested in see­ing the ef­fects of the drug on these soli­tary an­i­mals. The drugged oc­to­puses were much more in­clined to spend time with other oc­to­puses in­stead of solv­ing prob­lems, reach­ing out mul­ti­ple arms to en­gage in phys­i­cal con­tact. Non-drugged oc­to­puses avoid con­tact and typ­i­cally only use one arm to make con­tact when nec­es­sary.

The mind’s per­cep­tion of the world is for­mu­lated by the in­for­ma­tion pro­vided by the brain through its sen­sory net­work. Drugs can have a pro­found ef­fect on this in­for­ma­tion.

AP FILE PHOTO

A po­lice of­fi­cer shows seized MDMA tablets, also known as ec­stasy, dur­ing a me­dia pre­sen­ta­tion at the El Do­rado Air­port in Bogota, Colom­bia. Sci­en­tists found ex­po­sure to MDMA made oc­to­puses more in­clined to touch each other.

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