How Memory Conforms to Brain Development

Abstract

Nature exhibits countless examples of adaptive networks , whose topology evolves constantly coupled with the activity due to its function. The brain is an illustrative example of a system in which a dynamic complex network develops by the generation and pruning of synaptic contacts between neurons while memories are acquired and consolidated. Here, we consider a recently proposed brain developing model to study how mechanisms responsible for the evolution of brain structure affect and are affected by memory storage processes. Following recent experimental observations, we assume that the basic rules for adding and removing synapses depend on local synaptic currents at the respective neurons in addition to global mechanisms depending on the mean connectivity. In this way a feedback loop between “form” and “function” spontaneously emerges that influences the ability of the system to optimally store and retrieve sensory information in patterns of brain activity or memories. In particular, we report here that, as a consequence of such a feedback-loop, oscillations in the activity of the system among the memorized patterns can occur, depending on parameters, reminding mind dynamical processes. Such oscillations have their origin in the destabilization of memory attractors due to the pruning dynamics, which induces a kind of structural disorder or noise in the system at a long-term scale. This constantly modifies the synaptic disorder induced by the interference among the many patterns of activity memorized in the system. Such new intriguing oscillatory behavior is to be associated only to long-term synaptic mechanisms during the network evolution dynamics, and it does not depend on short-term synaptic processes, as assumed in other studies, that are not present in our model.

Neuromodulation of Glial Function During Neurodegeneration

“…Throughout this surveillance process, in which they are in contact with axons, synapses, and dendritic spines, they phagocyte disused synapses (Lauterbach and Klein, 2006 ; Paolicelli et al, 2011 ; Hong et al, 2016b ; Diaz-Aparicio et al, 2020 ; Milior et al, 2020 ), and therefore prevent energy and nutrient loss that is much needed at more active synapses. Hence, this synaptic pruning optimizes the effectiveness of neuronal transmission and functional plasticity in the brain and has been postulated to improve learning and memory capability (Millán et al, 2019 ). Indeed, abnormalities in synaptic pruning by microglia have been associated with the cognitive decline that accompanies many neurodegenerative disorders such as Alzheimer’s disease (AD; Hong et al, 2016a ).…”

Structural Insights Into the Dynamic Evolution of Neuronal Networks as Synaptic Density Decreases

“…Recently, a brain developing model, which combines an auto-associative neuronal network with an evolving mechanism for the birth and death of synapses, is proposed to study the relationship between structural and functional properties of neuronal networks (Millán et al, 2018a,b, 2019). Millán's model is similar to ours and also involves network dynamics and generation rules.…”

“…Furthermore, the network generation rules in our model contain some factors that reflect the spatial distance between neurons, which is not considered in Millán's model. The numerical simulation results of Millán's model demonstrate that the appearance of hubs and heterogeneity can greatly improve the stability of the memory patterns (Millán et al, 2019), and the existence of synaptic pruning is critical in providing ordered stationary states and stable memories (Millán et al, 2018a,b). Whereas, our numerical simulation exhibits how the network connectivity and the network efficiency changes during the decline of the synaptic density, and how the spatial distance between neurons affects the appearance of hubs and heterogeneity.…”

FMRP y las neuroliginas: la influencia de la actividad sensorial en las dinámicas del neurodesarrollo

“…A lo largo de la vida de los animales, las sinapsis que no se eliminaron y que, por el contrario, maduraron pueden cambiar la fortaleza de su respuesta eléctrica dependiendo de la experiencia obtenida en la interacción con el ambiente. A esto se le llama plasticidad neuronal (1,11,12). Las dos formas principales de plasticidad sináptica en el cerebro son la potenciación a largo plazo (LTP) y la depresión a largo plazo (LTD) (13).…”

“…Consecuentemente con lo anterior, se ha documentado en la Drosophila melanogaster que las mutaciones en DNlg 2 reducen tanto el árbol axonal como los botones sinápticos y alteran las cantidades de transmisores liberados en las uniones neuromusculares (96,99). También se ha encontrado que las mutaciones en DNlg 1 y 3 llevan a una reducción de la maduración sináptica y de los botones sinápticos en las uniones neuromusculares, así como a problemas en la diferenciación sináptica (11,97,98). Adicionalmente, se ha comprobado que la ausencia de DNlg 2 y 4 altera las interacciones sociales de las moscas (98).…”