Busebenza Kanjani Ubuchopho Bakho?
“Ubuchopho buyingxenye yomzimba okunzima kakhulu ukuyicwaninga,” kuphawula u-E. Fuller Torrey, udokotela wezifo zengqondo e-U.S. National Institute of Mental Health. “Buhlala kulolu gebhezi olusemahlombe ethu okunzima kakhulu ukulucwaninga.”
NOMA KUNJALO, ososayensi bathi kakade sebefundé okuningi ngendlela ubuchopho obusebenzisa ngayo ukwaziswa obukunikezwa izinzwa zethu ezinhlanu. Ngokwesibonelo, cabangela indlela obusebenzelana ngayo nenzwa yokubona.
Amehlo Engqondo Yakho
Ukukhanya kungena ehlweni lakho kuthinte i-retina, enezinhlu ezintathu zamangqamuzana ngemva kwembulunga yeso lakho. Ukukhanya kungena ohlwini lwesithathu. Lolu hlu lunamangqamuzana abizwa ngokuthi ama-rod, asheshe azwele ukukhanya okuxhophayo, nama-cone, amukela ukukhanya okuza ngamazinga amaza angafani okuhambisana nombala obomvu, oluhlaza okotshani noluhlaza okwesibhakabhaka. Ukukhanya kugqamisa imibala kula mangqamuzana. Enye yawo ithumela umyalezo emangqamuzaneni asohlwini lwesibili, usuke lapho uye kwamanye amangqamuzana asohlwini olungaphezulu. Ama-axon ala mangqamuzana ayahlangana akhe inzwa yokubona.
Izigidi zamangqamuzana enzwa yokubona zifika emgamanxweni osebuchosheni owaziwa ngokuthi i-optic chiasma. Lapha, amangqamuzana ezinzwa athwele umbiko ovela engxenyeni engakwesobunxele ye-retina yeso ngalinye manje ayahlangana alandele imigudu eya engxenyeni yobuchopho engakwesobunxele. Ngokufanayo, imibiko evela engxenyeni engakwesokudla ye-retina yeso ngalinye nayo iyahlangana iye engxenyeni engakwesokudla. Ngokulandelayo lezi zithunywa zifika kuyi-thalamus, indawo ezinikezelana kuyo nezinye, kamuva amangqamuzana ezinzwa alandelayo adlulisela umbiko endaweni engemuva yobuchopho ebizwa ngokuthi i-visual cortex.
Izici ezihlukene ezithwele ukwaziswa ngaloko okubonwayo zihamba emigudwini elinganisene. Abacwaningi manje sebeyazi ukuthi indawo yokuqala ye-visual cortex kanye nendawo eseduze kusebenza njengeposi ekuhlungeni, ekuthumeleni nasekuhlanganiseni ukwaziswa okuningi okulethwa amangqamuzana ezinzwa. Indawo yesithathu ihlola isimo sokwakheka, njengonqenqema lwento nokunyakaza. Indawo yesine ibheka kokubili isimo nombala, kuyilapho eyesihlanu ihlale ibheka amabalazwe ezinto ezibonwayo ukuze iphawule imigudu ezihamba kuyo. Ucwaningo lwamanje lubonisa ukuthi zingafinyelela ku-30 izindawo zobuchopho ezisebenzisa ukwaziswa kwento ebonwa iso! Kodwa zihlangana kanjani ukuze zikunikeze isithombe? Yebo, ingqondo yakho “ibona” kanjani?
“Ukubona” Ngengqondo
Iso liqoqela ubuchopho ukwaziswa, kodwa ngokusobala yi-cortex esebenzisa ukwaziswa okutholwa ubuchopho. Thatha isithombe ngekhamera, isithombe esiphumayo sembula izici zaso sonke isenzakalo. Kodwa uma uzibukela ngawakho amehlo sona leso senzakalo, ubona ingxenye yesenzakalo ogxile kuyo kuphela. Ukuthi ubuchopho bukwenza kanjani lokhu, akekho owaziyo. Abanye bakholelwa ukuthi kuwumphumela wokuhlangana kancane kancane kokwaziswa kwento ebonwayo ezindaweni ezibizwa ngokuthi ama-convergence zone, okukusiza ukuba uqhathanise lokho okubonayo nalokho osukwazi kakade. Abanye basikisela ukuthi uma uhluleka ukubona into ethile ngaphandle kokuphazamiseka, kumane nje kungenxa yokuthi amangqamuzana ezinzwa aqondisa ukubona okudinga unake, awayithumeli imibiko.
Kungakhathaliseki ukuthi yikuphi, ubunzima ososayensi ababhekana nabo ekuchazeni ukuthi iso libona kanjani, buncane uma buqhathaniswa nezinkinga ababhekana nazo ekutholeni nje ukuthi “ukunaka” kanye “nengqondo” ngempela kuhilelani. Izindlela zokuhlola, njenge-magnetic resonance imaging ne-positron-emission tomography, ziye zanikeza ososayensi indlela entsha yokuthola ukwaziswa ngobuchopho bomuntu. Futhi ngokuphawula ukugelezela kwegazi ezingxenyeni ezithile zobuchopho ngesikhathi umuntu ecabanga, baye baqiniseka ukuthi izindawo ezihlukene ze-cortex ngokusobala zisiza umuntu ukuba ezwe amazwi, awabone futhi awakhulume. Nokho, njengoba omunye umbhali ephetha, “ingqondo nokunaka kuyinkimbinkimbi kakhulu . . . kunokuba noma ubani ake acabanga.” Yebo, okuningi okungaziwa ngobuchopho kusamelwe kwembulwe.
Ubuchopho—Ingabe Bumane Nje Buyi-computer Eyisimangaliso?
Ukuze siqonde ubuchopho bethu obuyinkimbinkimbi, kungase kusisize ukuqhathanisa. Ekuqaleni kwenguquko yezezimboni, phakathi nekhulu le-18, kwakuvamile ukuqhathanisa ubuchopho nomshini. Kamuva, lapho ucingo luba uphawu lwentuthuko, abantu baqhathanisa ubuchopho nocingo olumatasa olunomuntu oluphendulayo owenza izinqumo. Manje njengoba i-computer isisingatha imisebenzi enzima, abanye baqhathanisa ubuchopho ne-computer. Ingabe loku kuqhathanisa kuyichaza ngokugcwele indlela ubuchopho obusebenza ngayo?
Kunomehluko omkhulu ngokuphawulekayo owenza ubuchopho ne-computer kungafani. Ngokuyinhloko ubuchopho buyisimiso samakhemikhali, hhayi sikagesi. Kwenzeka izinguquko zamakhemikhali eziningi phakathi kwengqamuzana ngayinye, futhi loku kuhluke ngokuphelele endleleni i-computer esebenza ngayo. Futhi, njengoba uDkt. Susan Greenfield ephawula, “akukho muntu owenza izinhlelo zokusebenza kobuchopho: buyisicubu esizenzela ngokwaso izinhlelo, esisebenza ngokwemvelo.” Abufani ne-computer okufanele yenzelwe izinhlelo.
Amangqamuzana ezinzwa axhumana wodwa ngendlela eyinqaba. Amangqamuzana ezinzwa amaningi asabela emiyalezweni yokuxhumana eyinkulungwane noma ngaphezulu. Ukuze uqonde ukuthi lokhu kuhilelani, cabangela ukucwaninga okwenziwa esinye isazi sokusebenza kwezinzwa. Sacwaninga indawo yobuchopho engezansi, ethé ukuba ngenhla naseceleni kwekhala ukuze sithole ukuthi siwezwa kanjani amaphunga. Siyaphawula: “Ngisho nalo msebenzi obonakala ulula—obonakala uwubala uma kuqhathaniswa nokuxazulula inkinga ezibalweni noma ukuqonda indlela uBeethoven ayedlala ngayo izinsimbi ezine zomculo—udinga cishe izigidi eziyisithupha zamangqamuzana ezinzwa, ngayinye imukela cishe imiyalezo eyizinkulungwane eziyishumi evela kwamanye.”
Nokho, ubuchopho bungaphezu nje kokuba iqoqo lamangqamuzana ezinzwa. Engqamuzaneni yezinzwa ngayinye kunama-neuroglia amaningana. Ngaphezu kokugcina ubuchopho bundawonye, ahlukanisa amangqamuzana ezinzwa ukuze angathintani ngogesi, alwe nezifo ezithathelwanayo futhi ahlangane ndawonye ukuze abe umgoqo ovikela igazi lobuchopho. Abacwaningi bakholelwa ukuthi kungenzeka ama-neuroglia aneminye imisebenzi esazotholakala. “Loku kuqhathanisa okunganembile, okuqhathanisa [ubuchopho] nama-computer enziwe umuntu aguqula ukwaziswa kwama-electron kube izinombolo, kungokungaphelele kangangokuthi kuyadukisa,” kuphetha umagazini i-Economist.
Loku kusasishiya nenye imfihlakalo okusamelwe sixoxe ngayo.
Zakhiwa Yini Izinkumbulo?
Inkumbulo—“mhlawumbe isici esiyingqayizivele kakhulu ezweni,” ngokukaProfesa Richard F. Thompson—ihlanganisa imisebenzi yobuchopho eminingana engafani. Abaningi abafundi abafunda ngobuchopho bahlukanisa inkumbulo ngezinhlobo ezimbili, echazayo neyenqubo. Eyenqubo ihlanganisa amakhono nemikhuba. Ngakolunye uhlangothi, echazayo ihlanganisa ukugcina izenzakalo. Incwadi ethi The Brain—A Neuroscience Primer ihlukanisa inkumbulo ngokwesikhathi esithathayo: inkumbulo emfushane kakhulu, ehlala cishe imizuzwana eyizingxenyana zezinkulungwane eziyikhulu; inkumbulo yesikhashana, ehlala imizuzwana emibalwa; inkumbulo esebenzayo, egcina izenzakalo zamuva nenkumbulo ehlala isikhathi eside, egcina ukwaziswa okukhulunywayo okuye kwalungiselelwa namakhono okunyakaza aye afundwa.
Inkumbulo ehlala isikhathi eside ingachazwa nangokuthi iqala igxile engxenyeni engaphambili yobuchopho. Ukwaziswa okukhethelwe ukugcinwa isikhathi eside kudlula njengombiko kagesi kuye engxenyeni yobuchopho ebizwa ngokuthi i-hippocampus. Lapha, inqubo ebizwa ngokuthi i-potentiation yesikhathi eside ithuthukisa ikhono lamangqamuzana ezinzwa lokudlulisa imiyalezo.—Bheka ibhokisi elithi “Ukuvala Igebe.”
Inkolelo-mbono ehlukile ngenkumbulo ivela embonweni wokuthi amaza asebuchosheni afeza indima ebalulekile. Abashisekeli bayo bakholelwa ukuthi ukushintshashintsha kokusebenza kukagesi ebuchosheni, njengokushaywa kwesigubhu, kusiza ekuhlanganiseni izinkumbulo ndawonye futhi kulawule isikhathi amangqamuzana obuchopho ahlukene ashukunyiswa ngaso.
Abacwaningi bakholelwa ukuthi ubuchopho bugcina izici ezihlukahlukene zenkumbulo ezindaweni ezihlukene, umqondo ngamunye uxhunywa nendawo yobuchopho eqonda wona ngokukhethekile. Ngokuqinisekile nezinye izingxenye zobuchopho ziyahlanganyela ekugcineni inkumbulo. I-amygdala, iqoqwana lamangqamuzana ezinzwa elincane, elingange-alimondi, eliseduze nesiqu sobuchopho, isebenza ngezinkumbulo zokwesaba. I-basal ganglia igxila emikhubeni nasemakhonweni omzimba, bese kuthi i-cerebellum, ingxenye yobuchopho engezansi, igxile ezintweni ozifunda ngokuzenza nasezintweni ezizenzakalelayo ezibangelwa ukushukunyiswa okuthile. Kukholelwa ukuthi lapha sigcina amakhono okuzimela—ngokwesibonelo, lawo esiwadingayo ukuze sigibele ibhayisikili.
Ukuhlola kwethu kafushane indlela ubuchopho obusebenza ngayo kuye kwayeqa eminye imisebenzi emikhulu, njengokugcina kwabo isikhathi, ukufunda ulimi, ubunkimbinkimbi bokunyakaza kwabo okuqondiswayo, nendlela yabo yokulawula isimiso sezinzwa somzimba kanye nezicubu ezibalulekile nokubhekana nezinhlungu. Kanti okunye okusacutshungulwa, izithunywa zamakhemikhali ezixhumana nesimiso sokuzivikela komzimba. “Indlela obuyinkimbinkimbi ngayo ayikholeki kangangokuthi uyazibuza ukuthi likhona yini ithemba lokukusombulula,” kuphawula usosayensi wezinzwa uDavid Felten.
Nakuba izimfihlakalo eziningi zobuchopho zisala zingaziwa, lesi sitho esivelele sisinikeza ikhono lokucabanga, lokuzindla nelokukhumbula esesikufundile. Kodwa singabusebenzisa kanjani ubuchopho ngokunenzuzo? Isihloko sokugcina kulolu chungechunge sisinika impendulo.
[Ibhokisi/Izithombe ekhasini 8]
UKUVALA IGEBE
Lapho ingqamuzana yezinzwa ishukunyiswa, umbiko uhamba kuyi-axon yengqamuzana yezinzwa. Lapho ufika esigaxeni segebe eliwumxhumanisi, ubangela ukuba izimbulungana ezincane (ama-vesicle aleli gebe) zihlangane nengxenye ephezulu yesigaxa bese zidedela umbiko osuka kuleli gebe, loku kwenzeka nje imbulungana ngayinye ibambe izinkulungwane zama-molecule ezithunywa zezinzwa ezingaphakathi kwalesi sigaxa.
Ngesimiso esiyinkimbinkimbi sezingidi nezihluthulelo, izithunywa zezinzwa zivula zibuye zivale imigudu yokungena engqamuzaneni yezinzwa elandelayo. Ngenxa yalokho, izinhlayiya ezinogesi zigelezela engqamuzaneni yezinzwa elandelayo bese zibangela ukushintsha kwamakhemikhali okwengeziwe okufike kushukumise ukukhishwa kukagesi lapho noma kuvimbele ukusebenza kukagesi okwengeziwe.
Isenzakalo esibizwa ngokuthi i-potentiation yesikhathi eside senzeka lapho amangqamuzana ezinzwa eshukunyiswa njalo abese ekhipha izithunywa zezinzwa ezisuka kuleli gebe. Abanye abacwaningi bakholelwa ukuthi le nqubo iwenza ahlangane ndawonye amangqamuzana ezinzwa. Abanye bathi kunobufakazi bokuthi umyalezo ubuyisela impendulo emuva usuka engqamuzaneni yezinzwa eyamukelayo uya engqamuzaneni edlulisayo. Loku, kube sekubangela ukushintsha kwamakhemikhali, okukhiqiza amaprotheni engeziwe azosebenza njengezithunywa zezinzwa. Lezi zithunywa ziqinisa ukuxhumana phakathi kwamangqamuzana ezinzwa.
Ukushintshashintsha kokuxhumana ebuchosheni, ukukwazi kwabo ukuvumelana nezimo, kubangela isiqubulo esithi, “Kuphakathi kokuthi uyabusebenzisa noma buyaphupha.” Ngakho-ke ukuze ugcine inkumbulo kubalulekile ukuhlale uzikhumbuza.
I-“axon”
Umucu othwala umbiko oxhumanisa amangqamuzana ezinzwa
Ama-“dendrite”
Abaxhumanisi abafushane abamagatshagatsha abaxhumanisa amangqamuzana ezinzwa
Ama-“neurite”
Izinto eziphuma engqamuzaneni yezinzwa ezinjengengalo. Kunezinhlobo ezimbili eziyinhloko—ama-axon nama-dendrite
Amangqamuzana ezinzwa
Cishe ubuchopho bunamangqamuzana ezinzwa ayizigidi eziyizinkulungwane eziyishumi kuya kweziyikhulu, “ngayinye ixhumana namakhulu noma ngezinye izikhathi nezinkulungwane zamanye amangqamuzana”
Izithunywa zezinzwa
Amakhemikhali athatha umbiko wenzwa usuka egebeni eliwumxhumanisi phakathi kwengqamuzana yenzwa ethumelayo kanye neyamukelayo
I-“synapse”
Igebe eliphakathi kwengqamuzana yenzwa ethumelayo neyamukelayo
[Imithombo]
Kusekelwe kwethi The Human Mind Explained kaProfesa Susan A. Greenfield, 1996
CNRI/Science Photo Library/PR
[Ibhokisi/Izithombe ekhasini 9]
AMAKHONO OMUNTU AVELELE
Izingxenye ezithile zobuchopho ezaziwa ngokuthi izikhungo zolimi zihlomisa abantu ngamakhono amangalisayo okuxhumana. Lokho esifuna ukukusho kubonakala kuhlelwa ingxenye yobuchopho engakwesobunxele eyaziwa ngokuthi iWernicke’s area (1). Le ngxenye ixhumana neBroca’s area (2), yona esebenzisa imithetho yolimi. Ngokulandelayo imibiko ifika ezindaweni ezinyakazisa izicubu ezilawula izicubu zobuso futhi zisisize sakhe amagama afanelekile. Ngaphezu kwalokho, lezi zindawo zixhumana nesimiso sobuchopho sokubona ukuze sikwazi ukufunda; nesimiso sokuzwa ukuze sikwazi ukuzwa, ukuqonda, nokusabela kulokho esikutshelwa abanye; futhi esingekulibale, inqolobane yenkumbulo yokugcina imicabango efanelekayo. Incwadi ethi Journey to the Centres of the Brain iyaphawula: “Okwenza abantu bahluke ngempela ezilwaneni, ukukwazi kwabo ukufunda amakhono ahlukene ngendlela emangalisayo, amaqiniso nemithetho, hhayi nje kuphela ngezinto zezwe elibazungezile, kodwa ikakhulukazi ngabanye abantu nalokho okubenza baziphathe ngendlela abaziphatha ngayo.”
[Izithombe ekhasini 7]
Izingxenye ezihlukahlukene zobuchopho zinakekela umbala, isimo sokwakheka, umngcele nendlela into emé ngayo kanye nemigudu yokuhamba
[Umthombo]
Parks Canada/J. N. Flynn