Niuroni Wengi mno Nyara Kumbukumbu

Too Many Neurons Spoil the Memory

Utafiti mpya unaonyesha taratibu za mkononi na ambayo kumbukumbu-encoding mitandao neuronal kuibuka


Powered by Guardian.co.ukMakala hii yenye jina “neurons wengi mno nyara kumbukumbu” iliandikwa na Mo Costandi, kwa theguardian.com siku ya Ijumaa Februari 12 2016 15.15 UTC

Kuniambia ambapo kukaa mawazo, wamesahau hata wewe kuwaita nje? Kuniambia ambapo kukaa furaha ya umri, na ambapo anapenda kale, Na lini wao upya tena, na usiku wa usahaulifu siku za nyuma, Nipate traverse nyakati na mazingira mbali mbali, na kuleta faraja katika huzuni sasa na usiku wa maumivu? Unakwenda wapi, O mawazo? Kwa nini nchi kijijini ni ndege wako? Kama wewe returnest hadi wakati huu wa taabu, Wataka kuleta faraja juu ya mbawa zako, na umande na asali na zeri, Au sumu kutoka wilds jangwa, kutoka macho ya hasidi?

Katika shairi lake Epic, Maono ya kina mama wa Albion, William Blake maajabu juu ya asili ya kumbukumbu, uwezo wake wa kiakili kusafirisha sisi nyakati mbali na maeneo, na hisia nguvu, wote chanya na hasi, kwamba recollections yetu inaweza evoke. shairi ina maswali yaliyosalia yenye muhimu leo, kama vile nini kinatokea kwa kumbukumbu zetu yaliyopotea, na jinsi gani sisi kuvirejesha?

zaidi ya karne mbili baadaye, mifumo ya kuhifadhi kumbukumbu na retrieval ni matukio zaidi wameyachunguza katika sayansi ya ubongo. Ni sana kuamini kwamba kumbukumbu malezi inahusisha kuimarisha uhusiano kati ya mitandao wachache kusambazwa ya neurons katika muundo wa ubongo inayoitwa hipokampasi, na kwamba retrieval baadae unahusisha reactivation ya sawa Ensembles neuronal. Na bado, Wanasayansi bado mapambano kujibu maswali Blake dhahiri.

Sasa, Timu ya watafiti katika Chuo Kikuu cha Geneva kuwa alifanya mapema nyingine muhimu katika uelewa wetu wa taratibu neural msingi kumbukumbu malezi. Kutumia hali ya-ya sanaa njia iitwayo optogenetics, wao kuonyesha jinsi Ensembles neuronal kwamba encode kumbukumbu kuibuka, akifafanua kuwa Ensembles zenye neurons wengi mno - au wachache mno - kutatiza kumbukumbu retrieval.

optogenetics ni mbinu nguvu mno ambayo inahusisha kuanzisha protini mwani inayoitwa channelrhodopsins (ChRs) katika neurons. Hii inaelezea seli nyeti kwa mwanga, kama kwamba makundi maalum yao inaweza kuwa switched juu au mbali, kutumia kunde ya mwanga laser mikononi ndani ya ubongo kupitia nyuzi macho, juu ya tidsperioden ya milliseconds.

Miaka ya hivi karibuni, watafiti wametumia optogenetics studio neurons hippocampal kwamba kuwa hai wakati wa kumbukumbu malezi katika ubongo panya, na kuendesha Ensembles kinachoitwa kwa njia mbalimbali. Kwa njia hii, wanaweza kuianzisha Ensembles sawa na kushawishi kumbukumbu retrieval; kubadili kumbukumbu waoga juu au mbali; kubadilisha kumbukumbu hasi katika wale chanya, au kinyume chake; na hata implant kumbukumbu ya uwongo kabisa katika akili za panya.

utafiti mpya, wakiongozwa na Pablo Mendez na marehemu Dominique Muller, ambao kusikitisha alifariki katika ajali gliding mwezi Aprili mwaka jana, inajenga kazi hii mapema. Wanatengeneza panya jenetiki kuelezea Chr katika seli granule upande mmoja wa ubongo, ndani ya dentate mkoa ya hipokampasi. seli Granule ni neurons kanuni katika mkoa huu wa hipokampasi, ambayo ni wazo kuwa muhimu kwa ajili ya kazi hippocampal kama vile kumbukumbu na urambazaji anga. Waliweka wanyama katika mabwawa kubwa, kuruhusu baadhi yao kuchunguza mazingira yao mpya. Wakati huo huo, wao optogenetically kuanzishwa seli random granule katika baadhi ya panya, lakini si wengine.

Hippocampal granule seli akielezea Channelrhodopsin (katika nyekundu).
Hippocampal granule seli akielezea Channelrhodopsin (katika nyekundu). Image: Pablo Mendez

Wakati wao dissected na kuchunguzwa akili wanyama ' 45 dakika baadaye, watafiti kupatikana anga utafutaji zilionyesha shughuli katika Ensembles ya neurons hippocampal, kama ilivyopangwa na ngazi ya CFOs, wanaoitwa 'haraka mapema' gene kwamba ni kimewashwa haraka wakati neurons kuanza kwa moto. muhimu, panya kuruhusiwa kuchunguza mabwawa yao walikuwa na idadi kubwa ya CFOs-expressing granule cells than those left in their home cages for the duration of the experiment, and those that received optogenetic stimulation during the exploration had significantly higher numbers of CFOs–positive neurons than those that did not.

This showed that spatial exploration evokes activity in ensembles of dentate granule cells, and that randomly altering the activity of these networks with optogenetic stimulation increases the size of the ensembles, or the number of cells within them.

But does manipulating the size of the ensembles have any effect on behaviour? To find out, Mendez and his colleagues placed mice expressing ChR in their hippocampi into another cage, and gave them several mild electric shocks. With repetition of this treatment, the mice quickly learn to fear the cage, and quickly freeze up when returned into it, even when they are not given more shocks.

Wakati huu, the researchers optogenetically stimulated random granule cells in some of the mice, lakini si wengine, during the training, in order to increase the size of the neuronal ensemble that encodes the fearful memory. These mice exhibited less freezing behaviour when returned to the same cage than others who received no stimulation. But the stimulation also created artificial fear memories, such that the animals froze up in other situations, pia.

Inhibition of random granule cells had the same effect, suggesting that merely altering the number of neurons in the ensemble interfered with the animals’ ability to recall the fearful memories. These findings are consistent with those of an earlier study, which also showed that inhibiting or stimulating granule cell activity impairs contextual learning.

To understand why this might be, the researchers performed another series of experiments, using microelectrodes to record the activity of neurons in slices of hippocampal tissue. These experiments showed that optogenetic stimulation of granule cells produces a robust response in neighbouring interneurons, which release the inhibitory neurotransmitter GABA.

Hivyo, the firing of granule cells leads inhibitory interneurons, which dampen adjacent granule cells and prevent them from entering the ensemble. Kwa njia hii, interneurons appear to stabilize newly-formed memories by regulating the number and distribution of granule cells involved in encoding memories. Activating or silencing random granule cells upsets this process and alters the number of granule cells, which may make the new memories unstable.

“In this study, we used a simple form of memory, the memory of a spatial context, but the challenge is studying how more complex experiences are memorized, and how the brain deals with the storage of multiple experiences,” says Mendez. “Understanding these questions could help us to understand the limits of the brain’s storage capacity.”

Reference

Stefanelli, T., et al. (2016). Hippocampal Somatostatin Interneurons Control the Size of Neuronal Memory Ensembles. neuron, 89: 1-12. DOI: 10.1016/j.neuron.2016.01.024 [Abstract]

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