What we perceive might sometimes reflect the outcome of a value-based decision-making process, a new analysis of the literature suggests
Although visual perception might seem as easy as just opening our eyes and reporting what is out there, the underlying computations are surprisingly complex. One of the more revealing ways to study these computations is by using inputs that are ambiguous or even impossible under normal circumstances (for instance with radically different pictures seen by the two eyes). Faced with these unreasonable inputs, the brain tends to switch between potential interpretations – where the switching (known as perceptual multistability) obeys some striking rules. Neuroscientists from the Max Planck Institute for Biological Cybernetics in Tübingen and the University of Tübingen have assessed a broad literature on aspects of perceptual multistability, suggesting in a paper published in Neuron. They state that it is appropriate to consider switches as internal actions whose choices are determined by forms of internal value (e.g., emotional content of the image).
Max Planck and University of Tübingen scientists Shervin Safavi and Peter Dayan draw on centuries of empirical research and reflection in this field, providing computational and algorithmic interpretations. A venerable idea in the field which comes originally from Helmholtz is that the brain continuously interprets the image on our retinas in terms of the real contents of a scene that might have generated such inputs. This is a computational challenge, since there is an overwhelming wealth of possible contents of the scene; and a statistical challenge, because the inputs from the two eyes from a particular viewpoint only report on a fraction of the actual contents of the 3D visual world. The statistical challenge is only partially mitigated by our ability to move our eyes to look at a different portion of the scene.
The phenomenon of multistable perception
Sometimes, input signals are such that no single interpretation in terms of a particular content of the scene is credible. Safavi and Dayan note famous examples of this, including the Necker cube (a ‘flat’ representation of a solid cube that can be interpreted in two structurally different ways, as pointing left or right). In these cases, our brains then switch between the possible interpretations in characteristic patterns. Although we can sometimes try hard to control our perceptual switches, such conscious processes are often overwhelmed by apparently unconscious ones.
“Multistable perception is a straight-forward and non-invasive way to get a more integrative picture of the link between internal neural operations and conscious reports. We suggest that in case of perceived ambiguity, the brain treats the choice of a dominant interpretation as an internal action, which then, like all other actions, is determined by some form of value. Thus, just as when foraging for food, an animal might successively switch between patches because of the value of the victuals that are available, when processing an image with multiple possible interpretations, we might successively switch between alternative interpretations because of the value that is available from them. Thus, the brain areas, such as the anterior cingulate cortex, believed to be involved in switching between different external behaviours, might equally be involved in switching between different interpretations,” says Shervin Safavi.
Value-based decisions of the brain
What then are the sources of internal value? Examples given by Safavi include aesthetic value – the subjective beauty of an interpretation; and information value – the way that we can benefit from the interpretation in terms of the external actions that we then might need to choose (as in traffic lights); along with special conditions in which particular interpretations are associated with explicit rewards determined by an experimenter.
“Perceptual multistability is a very rich test case for studying neural processing, and so it has been investigated for a very long time, and has given rise to numerous and diverse results. It also has been investigated in context of psychiatric disease, for example schizophrenia, where interpretations can be malformed, and depression and anxiety, where different aspects of value are apparently decreased and increased. We intend to test whether particular aspects of perceptual multistability could be used as a non-invasive tool for understanding psychiatric dysfunction,” Peter Dayan adds.
In sum, the authors hope that their value-based view on perceptual multistability will contribute to a more cohesive understanding of the phenomenon. By involving sensory, decision-making and value-processing systems, it should help neuroscientists paint a clearer picture about what we understand as perceived consciousness, and also provide a new window onto aspects of pathology.
"Kila kitu tunachokiona wakati mwingine kinaweza kutafakari matokeo ya mchakato wa kufanya maamuzi ya thamani, ""uchambuzi mpya wa fasihi unaonyesha: Ingawa utambuzi wa kuona unaweza kuonekana rahisi kama kufungua macho yetu na kuripoti kile kilicho nje, hesabu za msingi ni ngumu sana." Njia moja ya kufunua zaidi ya kusoma hesabu hizi ni kwa kutumia pembejeo ambazo ni zisizo wazi au hata haiwezekani chini ya hali ya kawaida (kwa mfano na picha tofauti kabisa zilizoonekana na macho mawili). Kukabiliwa na pembejeo hizi zisizo na sababu, ubongo huwa na kubadilisha kati ya tafsiri zinazowezekana <unk> ambapo kubadili (inajulikana kama multistability ya utambuzi) hutii sheria fulani za kushangaza. Wataalamu wa sayansi ya neva kutoka Taasisi ya Max Planck ya Biolojia ya Cybernetics huko Tübingen na Chuo Kikuu cha Tübingen wamehesabu fasihi pana juu ya mambo ya multistability ya utambuzi, wakipendekeza katika karatasi iliyochapishwa katika Neuroscience. "Wanasema kwamba ni sahihi kuzingatia ""switches"" kama vitendo vya ndani ambavyo chaguzi zinaamuliwa na aina za thamani ya ndani (kwa mfano, maudhui ya hisia ya picha)." Max Planck na wanasayansi wa Chuo Kikuu cha Tübingen Sherwin Safavi na Peter Dayan hutegemea karne za utafiti wa uzoefu na tafakari katika uwanja huu, kutoa tafsiri za hesabu na algorithmic. "Hii ni kwa sababu ya nadharia ya Helmholtz ya ""ubongo unaendelea kutafsiri picha kwenye retina zetu kulingana na yaliyomo halisi ya eneo ambalo linaweza kuzalisha pembejeo kama hizo.""" Hii ni changamoto ya kompyuta, kwa kuwa kuna utajiri mkubwa wa maudhui ya uwezekano wa eneo hilo, na changamoto ya takwimu, kwa sababu pembejeo kutoka kwa macho mawili kutoka kwa mtazamo fulani inaripoti tu sehemu ndogo ya maudhui halisi ya ulimwengu wa kuona wa 3D. Tatizo la takwimu hupunguzwa kwa sehemu tu na uwezo wetu wa kuhamisha macho yetu ili kuangalia sehemu tofauti ya eneo hilo. Mfano wa utambuzi wa multistable: Wakati mwingine, ishara za kuingia ni kama kwamba hakuna tafsiri moja katika suala la maudhui maalum ya eneo la tukio ni ya kuaminika. Safavi na Dayan wanataja mifano maarufu ya hii, ikiwa ni pamoja na kiunzi cha Necker (wakilishi wa "flat" wa kiunzi kigumu ambacho kinaweza kutafsiriwa kwa njia mbili tofauti za muundo, kama kuelekeza kushoto au kulia). Katika visa hivi, ubongo wetu hubadilishana kati ya tafsiri zinazowezekana katika mifumo ya tabia. Ingawa nyakati nyingine tunaweza kujitahidi sana kudhibiti mabadiliko yetu ya utambuzi, mara nyingi michakato hiyo ya fahamu hushindwa na yale yanayoonekana kuwa ya hali ya chini. <unk>Multistable utambuzi ni moja kwa moja na njia isiyo ya uvamizi kupata picha zaidi ya ushirikiano kati ya shughuli za ndani za neva na ripoti za ufahamu. "Tunaonyesha kwamba katika kesi ya utata unaoonekana, ubongo hutumia chaguo la tafsiri inayoongoza kama hatua ya ndani ambayo, kama vitendo vingine vyote, huamuliwa na aina fulani ya thamani.""" Hivyo, kama vile wakati wa kutafuta chakula, mnyama anaweza kubadilisha mfululizo kati ya patches kwa sababu ya thamani ya vyakula ambayo inapatikana, wakati wa usindikaji wa picha na tafsiri nyingi zinazowezekana, tunaweza kubadilisha mfululizo kati ya tafsiri mbadala kwa sababu ya thamani ambayo inapatikana kutoka kwao. Hivyo, maeneo ya ubongo, kama vile anterior cingulate cortex, kuaminiwa kuwa kushiriki katika kubadili kati ya tabia tofauti za nje, inaweza pia kushiriki katika kubadili kati ya tafsiri tofauti, "anasema Shervin Safavi. Uamuzi wa ubongo unaotegemea thamani Ni nini basi chanzo cha thamani ya ndani? Mifano iliyotolewa na Safavi ni pamoja na thamani ya aesthetic - uzuri wa subjective wa tafsiri; na thamani ya habari - njia ambayo tunaweza kufaidika na tafsiri katika suala la vitendo vya nje ambavyo tunaweza kuchagua (kama katika taa za trafiki); pamoja na hali maalum ambazo tafsiri maalum zinahusishwa na tuzo za wazi zilizoamuliwa na mtafiti. <unk>Perceptual multistability ni kesi ya mtihani tajiri sana kwa ajili ya kusoma usindikaji wa neva, na hivyo imekuwa kuchunguzwa kwa muda mrefu sana, na imetoa matokeo mengi na mbalimbali. Pia imetafakariwa katika muktadha wa magonjwa ya akili, kwa mfano schizophrenia, ambapo tafsiri zinaweza kuwa na kasoro, na unyogovu na wasiwasi, ambapo mambo tofauti ya thamani yanaonekana kupungua na kuongezeka. Tuna nia ya kupima kama masuala maalum ya multistability ya utambuzi inaweza kutumika kama chombo cha noninvasive kwa kuelewa dysfunction ya kisaikolojia, "Peter Dayan anaongeza. Kwa muhtasari, waandishi wanatumaini kwamba mtazamo wao wa thamani juu ya multistability ya utambuzi utachangia uelewa wa umoja zaidi wa jambo hilo. Kwa kuhusisha mifumo ya hisia, maamuzi na usindikaji wa thamani, inapaswa kusaidia wanasayansi wa neva kuchora picha wazi zaidi juu ya kile tunachoelewa kama ufahamu wa utambuzi, na pia kutoa dirisha jipya kwenye nyanja za ugonjwa.