Network-level Processes Research Articles

The role of social networks in the self-management support foryoung women recently diagnosed with breast cancer.

It is widely acknowledged that social network support plays an important role in the quality of life and illness management of breast cancer survivors. However, the factors and processes that enable and sustain such support are less well understood. This paper reports baseline findings from a prospective UK national cohort of 1,202 women with breast cancer (aged <50 years at diagnosis), recruited before starting treatment, conducted in 2016-2019. Descriptive, univariate and multivariate regression analyses explored associations between the individual, and network member characteristics, and the type of support provided. Social network members provided a substantial level of illness-related, practical and emotional support. Highest contribution was provided by friends, followed by close family members. The social network members of women who did not have a partner provided a higher level of support than those in networks with a partner. Women without higher education were more reliant on close family members than those with higher education, and this was more so for women without a partner. Women with higher education without a partner were more reliant on friends and were overall best supported. Women without higher education who did not have a partner were overall least well supported. They had much smaller networks, were highly reliant on close family members, and on high level contributions from all network members. There is a need to develop network-based interventions to support people with a cancer diagnosis, prioritising support for the groups identified as most at risk. Interventions that support engagement with existing network members during treatment, and those that help extend such networks after treatment, are likely to be of benefit. A network perspective can help to develop tailored support and interventions by recognising the interactions between network and individual level processes.

Interplay between biochemical processes and network properties generates neuronal up and down states at the tripartite synapse.

Neuronal up and down states have long been known to exist both in vitro and in vivo. A variety of functions and mechanisms have been proposed for their generation, but there has not been a clear connection between the functions and mechanisms. We explore the potential contribution of cellular-level biochemistry to the network-level mechanisms thought to underlie the generation of up and down states. We develop a neurochemical model of a single tripartite synapse, assumed to be within a network of similar tripartite synapses, to investigate possible function-mechanism links for the appearance of up and down states. We characterize the behavior of our model in different regions of parameter space and show that resource limitation at the tripartite synapse affects its ability to faithfully transmit input signals, leading to extinction-down states. Recovery of resources allows for "reignition" into up states. The tripartite synapse exhibits distinctive "regimes" of operation depending on whether ATP, neurotransmitter (glutamate), both, or neither, is limiting. Our model qualitatively matches the behavior of six disparate experimental systems, including both in vitro and in vivo models, without changing any model parameters except those related to the experimental conditions. We also explore the effects of varying different critical parameters within the model. Here we show that availability of energy, represented by ATP, and glutamate for neurotransmission at the cellular level are intimately related, and are capable of promoting state transitions at the network level as ignition and extinction phenomena. Our model is complementary to existing models of neuronal up and down states in that it focuses on cellular-level dynamics while still retaining essential network-level processes. Our model predicts the existence of a "final common pathway" of behavior at the tripartite synapse arising from scarcity of resources and may explain use dependence in the phenomenon of "local sleep." Ultimately, sleeplike behavior may be a fundamental property of networks of tripartite synapses.

Nosotros mismos nos estamos matando/We are the ones killing ourselves: Unraveling individual and network characteristics associated with negative dietary acculturation among Mexican Americans in New York City

BackgroundResearch on negative dietary acculturation among Mexican-Americans has mostly focused on individual-level processes and has largely ignored the role of social networks. MethodsThis mixed-method study used an egocentric network approach and derived 1620 personal ties of self-identified Mexican adults in New York. 24-hour dietary recalls were used to derive a total Healthy Eating Index (HEI) and subscores. The qualitative portion generated narratives around who helps or hinders their efforts to eat healthfully. ResultsAt the individual level, age at which participants migrated to the U.S. was negatively associated with total HEI (β = −0.39, p < .01). An annual income below $30,000 was positively associated with total HEI (β = 0.25, p < .05) and with HEI fruit subscores (β = 0.25, p < .05). Acculturative stress was negatively associated with HEI fruit (β = −0.29, p < .05) and refined grain subscores (β = −0.34, p < .01). At the network level, the proportion of network members who consumed traditional Latino diets was negatively associated with total HEI and HEI refined grains subscores (β = −0.39, p < .001; and β = −0.23, p < .05; respectively). In contrast, the proportion of alters who lived in another country was positively associated with HEI dairy subscores (β = 0.25, p < .05). Juxtaposing qualitative participants’ visual representation of their total HEI scores with their lay interpretations of healthy and unhealthy eating matched public health messages of reducing sugar, red meat intake, and processed foods. However, participants felt that this could only be achieved through restriction rather than balance. Qualitative narratives also elucidated how dietary acculturation and income could help shape dietary quality in unexpected ways. ConclusionsThis study found evidence of negative dietary acculturation and showcases the complex ways in which both individual- and network-level processes help shape dietary choices for Mexican-Americans.

Apical amplification-a cellular mechanism of conscious perception?

We present a theoretical view of the cellular foundations for network-level processes involved in producing our conscious experience. Inputs to apical synapses in layer 1 of a large subset of neocortical cells are summed at an integration zone near the top of their apical trunk. These inputs come from diverse sources and provide a context within which the transmission of information abstracted from sensory input to their basal and perisomatic synapses can be amplified when relevant. We argue that apical amplification enables conscious perceptual experience and makes it more flexible, and thus more adaptive, by being sensitive to context. Apical amplification provides a possible mechanism for recurrent processing theory that avoids strong loops. It makes the broadcasting hypothesized by global neuronal workspace theories feasible while preserving the distinct contributions of the individual cells receiving the broadcast. It also provides mechanisms that contribute to the holistic aspects of integrated information theory. As apical amplification is highly dependent on cholinergic, aminergic, and other neuromodulators, it relates the specific contents of conscious experience to global mental states and to fluctuations in arousal when awake. We conclude that apical dendrites provide a cellular mechanism for the context-sensitive selective amplification that is a cardinal prerequisite of conscious perception.

Syngap1 regulates experience-dependent cortical ensemble plasticity by promoting in vivo excitatory synapse strengthening

A significant proportion of autism risk genes regulate synapse function, including plasticity, which is believed to contribute to behavioral abnormalities. However, it remains unclear how impaired synapse plasticity contributes to network-level processes linked to adaptive behaviors, such as experience-dependent ensemble plasticity. We found that Syngap1, a major autism risk gene, promoted measures of experience-dependent excitatory synapse strengthening in the mouse cortex, including spike-timing-dependent glutamatergic synaptic potentiation and presynaptic bouton formation. Synaptic depression and bouton elimination were normal in Syngap1 mice. Within cortical networks, Syngap1 promoted experience-dependent increases in somatic neural activity in weakly active neurons. In contrast, plastic changes to highly active neurons from the same ensemble that paradoxically weaken with experience were unaffected. Thus, experience-dependent excitatory synapse strengthening mediated by Syngap1 shapes neuron-specific plasticity within cortical ensembles. We propose that other genes regulate neuron-specific weakening within ensembles, and together, these processes function to redistribute activity within cortical networks during experience.

Resilience in interorganizational networks: dealing with day-to-day disruptions in critical infrastructures

Purpose Critical infrastructures (CIs) for essential services such as water supply and electricity delivery are notoriously vulnerable to disruptions. While extant literature offers important insights into the resilience of CIs following large-scale disasters, our understanding of CI resilience to the more typical disruptions that affect CIs on a day-to-day basis remains limited. The present study investigates how the interorganizational (supply) network that uses and manages the CI can mitigate the adverse consequences of day-to-day disruptions. Design/methodology/approach Longitudinal archival data on 277 day-to-day disruptions within the Dutch national railway CI were collected and analyzed using generalized estimating equations. Findings The empirical results largely support the study’s predictions that day-to-day disruptions have greater adverse effects if they co-occur or are relatively unprecedented. The findings further show that the involved interorganizational network can enhance CI resilience to these disruptions, in particular, by increasing the overall level of cross-boundary information exchange between organizations inside the network. Practical implications This study helps managers to make well-informed choices regarding the target and intensity of their cross-boundary information-exchange efforts when dealing with day-to-day disruptions affecting their CI. The findings illustrate the importance of targeting cross-boundary information exchange at the complete interorganizational network responsible for the CI and to increase the intensity of such efforts when CI disruptions co-occur and/or are unprecedented. Originality/value This study contributes to our academic understanding of how network-level processes (i.e. cross-boundary information exchange) can be managed to ensure interorganizational (supply) networks’ resilience to day-to-day disruptions in a CI context. Subsequent research may draw from the conceptual framework advanced in the present study for examining additional supply network-level processes that can influence the effectiveness of entire supply networks. As such, the present research may assist scholars to move beyond a simple dyadic context and toward examining complete supply networks

Autoconfiguration with Global Addresses Using IEEE 802.15.4 Standard in Multi-hop Networks

Wireless sensor networks continue to attract a lot of attention from academia and industry promoting large-scale deployments in applications related to the Internet of Things (IoT). Unfortunately, a network containing a large number of sensor nodes also leads to difficulty in the configuring process and assignment of identifiers to nodes. Various approaches have been proposed to solve problems of auto-configuration in Wireless sensor networks, however, still, there are some issues remaining related to automatic assign identifiers A cluster-based hierarchical global address allocation scheme is proposed for a wireless sensor network. The proposal uses the IEEE 802.15.4 protocol and aims to reduce the latency of the identifier assignments and reduce the network level processes to be performed at the node. The address allocation process assigns each node a unique global address, which allows the node to have end-to-end connectivity without network-level involvement. The scenario of adding new nodes to the network or nodes that leave it is contemplated. Finally, the proposed scheme is evaluated experimentally, verifying the correct operation of the algorithm proposed in the implemented prototype.

The Effects of a TMS Double Perturbation to a Cortical Network.

Transcranial magnetic stimulation (TMS) is often used to understand the function of individual brain regions, but this ignores the fact that TMS may affect network-level rather than nodal-level processes. We examine the effects of a double perturbation to two frontoparietal network nodes, compared with the effects of single lesions to either node. We hypothesized that Bayesian evidence for the absence of effects that build upon one another indicates that a single perturbation is consequential to network-level processes. Twenty-three humans performed pro-saccades (look toward) and anti-saccades (look away) after receiving continuous theta-burst stimulation (cTBS) to right frontal eye fields (FEFs), dorsolateral prefrontal cortex (DLPFC), or somatosensory cortex (S1; the control region). On a subset of trials, a TMS pulse was applied to right posterior parietal cortex (PPC). FEF, DLPFC, and PPC are important frontoparietal network nodes for generating anti-saccades. Bayesian t tests were used to test hypotheses for enhanced double perturbation effects (cTBS plus TMS pulse) on saccade behaviors, against the alternative hypothesis that double perturbation effects to a network are not greater than single perturbation effects. In one case, we observed strong evidence [Bayes factor (BF10) = 325] that PPC TMS following DLPFC cTBS enhanced impairments in ipsilateral anti-saccade amplitudes over DLPFC cTBS alone, and not over the effect of the PPC pulse alone (BF10 = 0.75), suggesting that double perturbation effects do not augment one another. Rather, this suggests that computations are distributed across the network, and in some cases there can be compensation for cTBS perturbations.

Preventing Adolescent Substance Use: A Content Analysis of Peer Processes Targeted Within Universal School-Based Programs.

Universal school-based substance use prevention programs are widely disseminated and often include a focus on peer relationships. Network theory and social network analysis (SNA) have emerged as useful theoretical and methodological frameworks for examining the role of peer relationships in prevention and intervention research. We used content analysis to systematically code the peer processes targeted by three universal school based prevention programs. We found that programs focused on peer socialization more than peer selection, and programs focused about evenly on descriptive and injunctive norms. Programs varied in their focus on positive and negative peer processes and behaviors, but most references to peer processes focused on positive processes and negative behaviors. The focus on peer processes at the dyadic, subgroup, and network levels varied across the three programs, with the heaviest focus on network level processes. When peer processes were targeted, it was rare that lessons focused on peer processes for an extended (> 50%) amount of the lesson content. However, when peer processes were a focus, discussion and reflection were commonly encouraged. These patterns are considered in the context of non-intervention research on adolescent peer relations, which highlights the importance of peer selection and dyad-level processes, and the existence of positive peer processes that promote adolescent development. In doing so, we provide a framework that can be used to (1) examine the extent to which a particular program focuses on the different peer processes, and (2) inform systematic experimental studies of the extent to which particular peer processes are malleable in response to intervention efforts.

Identifying the processes of change and engagement from using a social network intervention for people with long-term conditions. A qualitative study.

BackgroundPersonal and community networks are recognized as influencing and shaping self‐management activities and practices. An acceptable intervention which facilitates self‐management by mobilizing network support and improves network engagement has a positive impact on health and quality of life. This study aims to identify the processes through which such changes and engagement take place.MethodsThe study was conducted in the south of England in 2016‐2017 and adopted a longitudinal case study of networks design. Purposive sample of respondents with long‐term conditions (n = 15) was recruited from local groups. Barriers and facilitators to implementation were explored in interviews with key stakeholders (5).ResultsIntervention engagement leads to a deepening of relationships within networks, adding new links and achieving personal objectives relevant for improving the health and well‐being of users and network members. Such changes are supported through two pathways: the mobilization of network capabilities and by acting as a nudge. The first is a gradual process where potentially relevant changes are further contemplated by forefronting immediate concerns and negotiating acceptable means for achieving change, prioritizing objective over subjective valuations of support provided by network members and rehearsing justifications for keeping the status quo or adopting change. The second pathway changes are enacted through the availability of a potential fit between individual, network and environmental conditions of readiness.ConclusionsThe two pathways of network mobilization identified in this study illuminate the individual, network and environmental level processes involved in moving from cognitive engagement with the intervention to adopting changes in existing practice.

Basal Forebrain and Brainstem Cholinergic Neurons Differentially Impact Amygdala Circuits and Learning-Related Behavior

The central cholinergic system and the amygdala are important for motivation and mnemonic processes. Different cholinergic populations innervate the amygdala, but it is unclear how these projections impact amygdala processes. Using optogenetic circuit-mapping strategies in choline acetyltransferase (ChAT)-cre mice, we demonstrate that amygdala-projecting basal forebrain and brainstem ChAT-containing neurons can differentially affect amygdala circuits and behavior. Photo-activating ChAT terminals invitro revealed the underlying synaptic impact of brainstem inputs to the central lateral division to be excitatory, mediated via the synergistic glutamatergic activation of AMPA and NMDA receptors. Incontrast, stimulating basal forebrain inputs to thebasal nucleus resulted in endogenous acetylcholine (ACh) release, resulting in biphasic inhibition-excitation responses onto principal neurons. Such response profiles are physiological hallmarks of neural oscillations and could thus form the basis of ACh-mediated rhythmicity in amygdala networks. Consistent with this, invivo basal forebrain ChAT+ activation strengthened amygdala basal nucleus theta and gamma frequency rhythmicity, both of which continued for seconds afterstimulation and were dependent on local muscarinic and nicotinic receptor activation, respectively. Activation of brainstem ChAT-containing neurons, however, resulted in a transient increase in central lateral amygdala activity that was independent of cholinergic receptors. In addition, driving these respective inputs inbehaving animals induced opposing appetitive and defensive learning-related behavioral changes. Because learning and memory are supported by both cellular and network-level processes in central cholinergic and amygdala networks, these results provide a route by which distinct cholinergic inputs can convey salient information to the amygdala and promote associative biophysical changes that underlie emotional memories.

A framework for understanding strategic network performance: Exploring efficiency and effectiveness at the network level

There are currently limits in our understanding of strategic network performance due to the complexity of the underlying processes involved. Improving our understanding of performance is critical if we are to improve network functioning, an important managerial problem. This paper addresses a research gap in strategic network performance by investigating: efficiency and effectiveness at the network level of analysis. A multiple case study methodology is used to investigate two Australian agri-business strategic networks. The cases suggest that processes relating to building actor webs and collective sensemaking are crucial for improving strategic network effectiveness, whereas network efficiency is influenced by developing activity patterns and utilizing resource constellations. The cases also highlight potential trade-offs between network effectiveness and efficiency in relation to performance at the network level. The paper contributes an empirically informed theoretical framework for understanding how network level processes influence network performance.

Generalizable knowledge outweighs incidental details in prefrontal ensemble code over time.

Memories for recent experiences are rich in incidental detail, but with time the brain is thought to extract latent rules and structures common across past experiences. We show that over weeks following the acquisition of two distinct associative memories, neuron firing in the rat prelimbic prefrontal cortex (mPFC) became less selective for perceptual features unique to each association and, with an apparently different time-course, became more selective for common relational features. We further found that during exposure to a novel experimental context, memory expression and neuron selectivity for relational features immediately generalized to the new situation. These neural patterns offer a window into the network-level processes by which the mPFC develops a knowledge structure of the world that can be adaptively applied to new experiences.

Modeling of Cerebral Oxygen Transport Based on In vivo Microscopic Imaging of Microvascular Network Structure, Blood Flow, and Oxygenation.

Oxygen is delivered to brain tissue by a dense network of microvessels, which actively control cerebral blood flow (CBF) through vasodilation and contraction in response to changing levels of neural activity. Understanding these network-level processes is immediately relevant for (1) interpretation of functional Magnetic Resonance Imaging (fMRI) signals, and (2) investigation of neurological diseases in which a deterioration of neurovascular and neuro-metabolic physiology contributes to motor and cognitive decline. Experimental data on the structure, flow and oxygen levels of microvascular networks are needed, together with theoretical methods to integrate this information and predict physiologically relevant properties that are not directly measurable. Recent progress in optical imaging technologies for high-resolution in vivo measurement of the cerebral microvascular architecture, blood flow, and oxygenation enables construction of detailed computational models of cerebral hemodynamics and oxygen transport based on realistic three-dimensional microvascular networks. In this article, we review state-of-the-art optical microscopy technologies for quantitative in vivo imaging of cerebral microvascular structure, blood flow and oxygenation, and theoretical methods that utilize such data to generate spatially resolved models for blood flow and oxygen transport. These “bottom-up” models are essential for the understanding of the processes governing brain oxygenation in normal and disease states and for eventual translation of the lessons learned from animal studies to humans.

Large-scale network-level processes during entrainment

Visual rhythmic stimulation evokes a robust power increase exactly at the stimulation frequency, the so-called steady-state response (SSR). Localization of visual SSRs normally shows a very focal modulation of power in visual cortex and led to the treatment and interpretation of SSRs as a local phenomenon. Given the brain network dynamics, we hypothesized that SSRs have additional large-scale effects on the brain functional network that can be revealed by means of graph theory. We used rhythmic visual stimulation at a range of frequencies (4–30Hz), recorded MEG and investigated source level connectivity across the whole brain. Using graph theoretical measures we observed a frequency-unspecific reduction of global density in the alpha band “disconnecting” visual cortex from the rest of the network. Also, a frequency-specific increase of connectivity between occipital cortex and precuneus was found at the stimulation frequency that exhibited the highest resonance (30Hz). In conclusion, we showed that SSRs dynamically re-organized the brain functional network. These large-scale effects should be taken into account not only when attempting to explain the nature of SSRs, but also when used in various experimental designs.

The application of a mathematical model linking structural and functional connectomes in severe brain injury.

Following severe injuries that result in disorders of consciousness, recovery can occur over many months or years post-injury. While post-injury synaptogenesis, axonal sprouting and functional reorganization are known to occur, the network-level processes underlying recovery are poorly understood. Here, we test a network-level functional rerouting hypothesis in recovery of patients with disorders of consciousness following severe brain injury. This hypothesis states that the brain recovers from injury by restoring normal functional connections via alternate structural pathways that circumvent impaired white matter connections. The so-called network diffusion model, which relates an individual's structural and functional connectomes by assuming that functional activation diffuses along structural pathways, is used here to capture this functional rerouting. We jointly examined functional and structural connectomes extracted from MRIs of 12 healthy and 16 brain-injured subjects. Connectome properties were quantified via graph theoretic measures and network diffusion model parameters. While a few graph metrics showed groupwise differences, they did not correlate with patients' level of consciousness as measured by the Coma Recovery Scale — Revised. There was, however, a strong and significant partial Pearson's correlation (accounting for age and years post-injury) between level of consciousness and network diffusion model propagation time (r = 0.76, p < 0.05, corrected), i.e. the time functional activation spends traversing the structural network. We concluded that functional rerouting via alternate (and less efficient) pathways leads to increases in network diffusion model propagation time. Simulations of injury and recovery in healthy connectomes confirmed these results. This work establishes the feasibility for using the network diffusion model to capture network-level mechanisms in recovery of consciousness after severe brain injury.

Spatiotemporal oscillatory dynamics during the encoding and maintenance phases of a visual working memory task

Many electrophysiology studies have examined neural oscillatory activity during the encoding, maintenance, and/or retrieval phases of various working memory tasks. Together, these studies have helped illuminate the underlying neural dynamics, although much remains to be discovered and some findings have not replicated in subsequent work. In this study, we examined the oscillatory dynamics that serve visual working memory operations using high-density magnetoencephalography (MEG) and advanced time-frequency and beamforming methodology. Specifically, we recorded healthy adults while they performed a high-load, Sternberg-type working memory task, and focused on the encoding and maintenance phases. We found significant 9–16 Hz desynchronizations in the bilateral occipital cortices, left dorsolateral prefrontal cortex (DLPFC), and left superior temporal areas throughout the encoding phase. Our analysis of the dynamics showed that the left DLPFC and superior temporal desynchronization became stronger as a function of time during the encoding period, and was sustained throughout most of the maintenance phase until sharply decreasing in the milliseconds preceding retrieval. In contrast, desynchronization in occipital areas became weaker as a function of time during encoding and eventually evolved into a strong synchronization during the maintenance period, consistent with previous studies. These results provide clear evidence of dynamic network-level processes during the encoding and maintenance phases of working memory, and support the notion of a dynamic pattern of functionally-discrete subprocesses within each working memory phase. The presence of such dynamic oscillatory networks may be a potential source of inconsistent findings in this literature, as neural activity within these networks changes dramatically with time.

The contribution of extracurricular activities to adolescent friendships: new insights through social network analysis.

Extracurricular activities are settings that are theorized to help adolescents maintain existing friendships and develop new friendships. The overarching goal of the current investigation was to examine whether coparticipating in school-based extracurricular activities supported adolescents' school-based friendships. We used social network methods and data from the National Longitudinal Study of Adolescent Health to examine whether dyadic friendship ties were more likely to exist among activity coparticipants while controlling for alternative friendship processes, namely dyadic homophily (e.g., demographic and behavioral similarities) and network-level processes (e.g., triadic closure). Results provide strong evidence that activities were associated with current friendships and promoted the formation of new friendships. These associations varied based on school level (i.e., middle vs. high school) and activity type (i.e., sports, academic, arts). Results of this study provide new insight into the complex relations between activities and friendship that can inform theories of their developmental outcomes.

Linking Social Capital to Small-Worlds: A Look at Local and Network-Level Processes and Structure

In the past decade, two topics have generated much interest in the idea of social networks and network analysis. These are social capital, popularised by Robert Putnam, and small-worlds, popularised by Duncan Watts and Albert-Laszlo Barabasi. Social capital highlights local processes and network structures, theorizing the ways in which relations and their patterns link individuals and groups to resources and beneficial outcomes. Small-worlds emphasizes global network structures, describing how large, heterogeneous networks can nonetheless appear small to individual actors, largely as a result of the high clustering and weak, bridging ties that make up these networks' structure. Although social capital and small-worlds share social networks as a common basis, they emphasize different sides of a spectrum: social capital focuses on the local and small-worlds on the global. In addition, both focus on seemingly different social phenomena: social capital emphasizes access to resources, whereas small-worlds emph...

The substrate for long-lasting memory: If not protein synthesis, then what?

The prevailing textbook view that de novo protein synthesis is required for memory (e.g., [ Bear, M. F., Connors, B., & Paradiso, M. 2006. Neuroscience. Lippincott, New York ]) is seriously flawed and an alternative hypothesis has been proposed in which post-translational modification (PTM) of proteins already synthesized and already present within the synapse is ‘the’ substrate for long-lasting memory. Protein synthesis serves a replenishment role. The first part of this review discusses how long-lasting memory can be achieved with ‘only’ PTM of existing synaptic proteins. The second part critically reviews a recent report published in Neuron 2007 that exemplifies the current view of protein synthesis and memory while also illustrating how these results can be understood within this new PTM framework. A necessary yet unexpected conclusion to emerge from consideration of the consequences of a PTM mechanism as the necessary, sufficient and exclusive substrate for long-lasting memory, is that the central Hebbian dogma that cells that ‘fire together, wire together’ is an unlikely mechanism for long-lasting memory. Thus, a unique feature of the PTM model is that longevity of information storage is achieved not by stability of the synaptic mechanism, but by impermanent pseudoredundant circuits. This is so because PTM is a reversible process and thus any permanent connection, any ‘lasting effect’ cannot be in the form of stable synapse formation. We have therefore proposed a solution in which network level processes regulate cellular mechanisms, even as such mechanisms regulate the network. Thus, synapses are ‘meta-stabilized’ by regulated feedback mediated by the circuit in which the synapse is embedded. For example, spontaneous activity is proposed to be a substrate feedback mechanism we term ‘cryptic rehearsal’ to sustain for some period of time after learning an approximation to the state initially created by input. Additionally, because the duplication of these traces is ongoing, this provides a degenerate code for the engram. Stability is thus achieved, not by stabilizing the synapse, but by implementing a pseudo-redundant yet malleable circuitry so that memory can be protected in the face of small catastrophes in network representation.