Here are two images of a house. There’s one obvious difference, but to this patient, P.S., they looked completely identical.
Tukaj sta dve sliki hiše. Obstaja ena očitna razlika, ampak pacientki P.S. sta obe videti popolnoma enaki.
P.S. had suffered a stroke that damaged the right side of her brain, leaving her unaware of everything on her left side. But though she could discern no difference between the houses, when researchers asked her which she would prefer to live in, she chose the house that wasn’t burning— not once, but again and again.
P. S. je utrpela možgansko kap, ki je poškodovala desno stran njenih možganov, zato se več ne zaveda ničesar na svoji levi strani. Toda čeprav med hišama ni opazila razlike, je, ko so jo raziskovalci vprašali, v kateri bi raje živela, izbrala hišo, ki ne gori - – ne enkrat, ampak znova in znova.
P.S.’s brain was still processing information from her whole field of vision. She could see both images and tell the difference between them, she just didn’t know it. If someone threw a ball at her left side, she might duck. But she wouldn’t have any awareness of the ball, or any idea why she ducked.
Njeni možgani so še naprej obdelovali podatke iz celotnega vidnega polja. Videla je obe sliki, zaznala razliko, vendar ni vedela, zakaj. Če bi ji kdo vrgel žogo na njeno levo stran, bi se morda sklonila. Vendar se ne bi zavedala žoge ali tega, zakaj se je sklonila.
P.S.’s condition, known as hemispatial neglect, reveals an important distinction between the brain’s processing of information and our experience of that processing. That experience is what we call consciousness. We are conscious of both the external world and our internal selves— we are aware of an image in much the same way we are aware of ourselves looking at an image, or our inner thoughts and emotions. But where does consciousness come from? Scientists, theologians, and philosophers have been trying to get to the bottom of this question for centuries— without reaching any consensus.
Stanje P.S., imenovano enostransko prostorsko zanemarjanje, razkriva pomembno razliko med možgansko obdelavo informacije in našo izkušnjo te obdelave. Tej izkušnji pravimo zavest. Zavedamo se zunanjega sveta in samih sebe, podobe se zavedamo na enak način, kot se zavedamo tega, da gledamo to podobo ali svojih misli in čustev. Toda od kod prihaja zavest? Znanstveniki, teologi in filozofi že več stoletij poskušajo priti do dna temu vprašanju, ne da bi dosegli kakršno koli soglasje.
One recent theory is that consciousness is the brain’s imperfect picture of its own activity.
Ena zadnjih teorij pravi, da je zavest nepopolna možganska slika lastne dejavnosti.
To understand this theory, it helps to have a clear idea of one important way the brain processes information from our senses. Based on sensory input, it builds models, which are continuously updating, simplified descriptions of objects and events in the world. Everything we know is based on these models. They never capture every detail of the things they describe, just enough for the brain to determine appropriate responses. For instance, one model built deep into the visual system codes white light as brightness without color. In reality, white light includes wavelengths that correspond to all the different colors we can see. Our perception of white light is wrong and oversimplified, but good enough for us to function. Likewise, the brain’s model of the physical body keeps track of the configuration of our limbs, but not of individual cells or even muscles, because that level of information isn’t needed to plan movement. If it didn’t have the model keeping track of the body’s size, shape, and how it is moving at any moment, we would quickly injure ourselves.
Da bi razumeli to teorijo, nam je v pomoč jasna predstava o pomembnem načinu, kako možgani predelujejo informacije na podlagi naših čutov. Na osnovi čutnih zaznav gradijo modele, ki se nenehno posodabljajo in so poenostavljeni opisi predmetov in dogodkov v svetu. Vse, kar vemo, temelji na teh modelih. Nikoli ne zajamejo vseh podrobnosti stvari, ki jih opisujejo, zajamejo samo toliko, da lahko možgani določijo ustrezne odzive. Na primer, model, vgrajen globoko v sistem vida, kodira belo svetlobo kot svetlobo brez barve. V resnici pa bela svetloba vključuje valovne dolžine, ki ustrezajo vsem različnim barvam, ki jih lahko vidimo. Naše dojemanje bele svetlobe je napačno in preveč poenostavljeno, vendar dovolj dobro, da lahko delujemo. Prav tako možganski model fizičnega telesa spremlja obliko naših okončin, ne pa posameznih celic ali celo mišic, saj ta raven informacij ni potrebna za načrtovanje gibanja. Če možgani ne bi imeli modela, ki bi spremljal velikost in obliko telesa ter kako se giblje v vsakem trenutku, bi se hitro poškodovali.
The brain also needs models of itself. For example, the brain has the ability to pay attention to specific objects and events. It also controls that focus, shifting it from one thing to another, internal and external, according to our needs. Without the ability to direct our focus, we wouldn’t be able to assess threats, finish a meal, or function at all. To control focus effectively, the brain has to construct a model of its own attention. With 86 billion neurons constantly interacting with each other, there’s no way the brain’s model of its own information processing can be perfectly self-descriptive. But like the model of the body, or our conception of white light, it doesn’t have to be. Our certainty that we have a metaphysical, subjective experience may come from one of the brain’s models, a cut-corner description of what it means to process information in a focused and deep manner.
Možgani prav tako potrebujejo modele samih sebe. Na primer, možgani so zmožni biti pozorni na določene objekte in dogodke. Nadzirajo tudi to osredotočenost ter jo prenašajo z ene stvari na drugo, notranjo in zunanjo, glede na naše potrebe. Brez možnosti nadzorovanja osredotočenosti ne bi mogli oceniti nevarnosti, pojesti obroka ali sploh delovati. Za natančen nadzor osredotočenosti morajo možgani sestaviti model svoje zbranosti. S 86 milijardami nevronov, ki neprestano vzajemno delujejo, model v možganih, ki opisuje to obdelavo informacij, ne more biti popolnoma natančen. Toda tako kot za model telesa ali našo idejo bele svetlobe ta popolnost ni potrebna. Naše prepričanje, da imamo metafizično subjektivno izkušnjo, lahko izvira iz enega izmed možganskih modelov, kar je skrčen opis za obdelovanje informacij na osredotočen in globok način.
Scientists have already begun trying to figure out how the brain creates that self model. MRI studies are a promising avenue for pinpointing the networks involved. These studies compare patterns of neural activation when someone is and isn’t conscious of a sensory stimulus, like an image. The results show that the areas needed for visual processing are activated whether or not the participant is aware of the image, but a whole additional network lights up only when they are conscious of seeing the image. Patients with hemispatial neglect, like P.S., typically have damage to one particular part of this network. More extensive damage to the network can sometimes lead to a vegetative state, with no sign of consciousness.
Znanstveniki že raziskujejo, kako možgani ustvarijo lasten model. Raziskave z uporabo magnetne resonance so obetaven način za natančno določanje vpletenih omrežij. Te raziskave primerjajo vzorce nevronskih aktivacij ob zavedanju in nezavedanju čutnih dražljajev, kot je slika. Rezultati kažejo, da se območja, potrebna za vizualno obdelavo, aktivirajo ne glede na to, ali se oseba zaveda slike ali ne, vendar se celotna dodatna mreža prižge, kadar se slike zaveda. Bolniki z enostranskim prostorskim zanemarjanjem, kot je P.S., imajo ponavadi poškodbo na določenem delu omrežja. Večja poškodba omrežja lahko včasih privede do vegetativnega stanja, brez znakov zavesti.
Evidence like this brings us closer to understanding how consciousness is built into the brain, but there’s still much more to learn. For instance, the way neurons in the networks related to consciousness compute specific pieces of information is outside the scope of our current technology. As we approach questions of consciousness with science, we’ll open new lines of inquiry into human identity.
Dokazi, kot je ta, nam pomagajo bolje razumeti, kako je zavest vgrajena v možgane, vendar se moramo še veliko naučiti. Na primer, način, na katerega nevroni v omrežjih, povezanih z zavestjo, izračunajo določene informacije, je izven dosega današnje tehnologije. S tem ko na vprašanja o zavesti odgovarjamo z znanostjo, odpiramo nove možnosti raziskovanja človeške identitete.