Öğrenme Esnasında Oluşan Dentritik Spine Yapısal Değişiminin Kısa -ve Uzun Dönem Bellek Davranışı Açısından Modellenmesi

Year 2018, Volume: 8 Issue: 1, 1 - 15, 15.06.2018

Ahmet Turan

Abstract

Canlılarda öğrenme ve bellek konusunda yapılan çalışmalar, teknolojik gelişmelerle önemli hız kazanmıştır.
Beyindeki sinir hücrelerinin oluşturduğu büyük ağ ortamında yapılan görüntülemeler hücreler arası
bağlantıların öğrenme sürecinde değişimlerini göstermektedir. Özellikle sinaptik bölgede, dendritik spine
yapısal değişimleri gözlenmektedir. Genç canlı beyninde sıkça görülen bu değişimler, sinaptik uyarı süresince,
yeni dendritik spine’lerin oluşması veya var olanların büyümesi şeklindedir. Sinaptik uyarılara bağlı olarak
oluşan bu değişim, kalıcı ya da önceki durumuna geri dönme şeklinde olmaktadır. Bu durumlar çeşitli
çalışmalarda yapısal ve biyofiziksel olarak yorumlanmış ve modellenmiştir. Çalışmamızda spine yapısal
değişiminin hesapsal yöntemlerle modellenmesi için bir yöntem önerilmiştir. Modelimizde öğrenme esnasında
gerçekleşen dendritik spine yapısal değişimi: Sinaptik iletkenlik fonksiyonunun zaman sabiti parametresi ile
modellenmiştir. Bu noktada dendritik spine’da büyüme, kalıcı olma, küçülme veya yok olma durumlarını
modellemek amacıyla sinaptik iletkenlik zaman sabitine değişen değerler verildi. Dendritik spine büyümesi,
uyarı geldikçe gerçekleşmekte, zaman sabiti değerine bu olayı modellemek için artan değerler verildi. Uyarım
kesildiğinde spine yapısı kalıcı olmuş ise, zaman sabiti değeri de sabit tutuldu. Bu durumda belleği oluşturan
motifler uzun dönem bellek gibi davrandı. Spine tekrar küçülmüşse, zaman sabiti değeri de küçültüldü. Bu
durumda belleği oluşturan motifler, kısa dönem bellek gibi davrandı. Sonuç olarak bizim modelimizde
dendritik spine büyümesinin zaman sabiti değerlerinin değişimiyle modellenebileceği gösterilmiştir.

Keywords

Sinir Hücresi, Dentritik spine, Sinaptik uyarı, Uzun dönem bellek, Kısa dönem bellek, Hodgkin-Huxley model

Modeling of Dendritic Spine Structural Change During Learning in Terms of Shortand Long-Term Memory Behavior

Abstract

Studies on learning and memory in life have gained a significant boost in technological developments. The
images made in the large network environment created by the nerve cells of the brain show the changes in the
learning process of the intercellular connections. Structural changes of the dendritic spine are observed,
especially in the synaptic region. These changes frequently seen in the young living brain are the formation of
new dendritic spines or the growth of existing ones during the synaptic stimulation. This change, which occurs
due to synaptic stimulation, is in the form of a permanent or return to the previous state. These cases are
structured and biophysically interpreted and modeled in various studies. In our work, a method is proposed
for modeling the structural change of spine by computational methods. Structural change of dendritic spine
during learning in our model: It is modeled by the time constant parameter of the synaptic conductivity
function. At this point, the values of the synaptic conductivity time constant are given to model the growth,
persistence, shrinkage or extinction of dendritic spines. Dendritic spine growth occurs as the stimulus arrives,
increasing the time constant value to model this event. If the spine structure was permanent when the
stimulation was interrupted, the time constant value was kept constant. In this case, the motifs that make up the memory behave like long term memory. If the spine has shrunk again, the time constant value has also
shrunk. In this case, the motifs that make up the memory behave like short term memory. As a result, it has
been shown in our model that dendritic spine growth can be modeled by changing the time constants.

Keywords

Nerve cell, Dentritic spine, Sinaptic stimulation, Long term memory, Short term memory, Hodgkin-Huxley model

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