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Neuronal avalanches in acute cortex slices. A, Light microscopic picture of the acute coronal brain slice and position of the microelectrode array. Cx, Cortex. B, Overplot of three different periods in which spontaneous, synchronized LFPs are visible. Three different periods (1-3) are shown (1 sec each) that reveal the occurrence of neuronal avalanches in three different, partially overlapping locations. For spatial location in the slice, see A. C, Raster plot of LFP activity in response to bath application of the NMDA receptor agonist NMDA and the D 1 receptor agonist SKF-38393. Note that synchronized events are visible across the array for 2000 sec after which the activity subsides. D, Individual event size distribution at t IEI avg from each acute slice experiment over plotted (n 9 acute slices). Black, Number of electrodes; gray, summed LFPs; broken line, power law with 3/2). E, Average event size distribution from data shown in D. Inset, Lifetime distributions of avalanches display a power law in initial portion with characteristic slope of 2 and exponential cutoff. Broken line, Power law with exponent of 2.
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Networks of living neurons exhibit diverse patterns of activity, including oscillations, synchrony, and waves. Recent work in physics has shown yet another mode of activity in systems composed of many nonlinear units interacting locally. For example, avalanches, earthquakes, and forest fires all propagate in systems organized into a critical state...
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... slice experiments. Coronal sections from adult rat brains (6 -8 weeks) were cut at 350 -400 m in chilled artificial CSF (ACSF) contain- ing the following (in mM): 124 NaCl, 0.3 NaH 2 PO 4 , 3.5 KCl, 1.2 CaCl 2 , 1 MgSO 4 , 26.2 NaHCO 3 , 10 D-glucose, and 50 M D,L-2-amino-5- phosphonovalerate (APV; Sigma, St. Louis, MO), saturated with 95% O 2 and 5% CO 2 (310 5 mOsm). Slices were stored submerged for 1-2 hr in ACSF without APV at room temperature before recording. For record- ing, slices were gently transferred onto the multielectrode array. The electrode array covered mostly supragranular layers of primary motor and somatosensory cortex. Electrode positions were reconstructed using pictures taken at the end of each recording session (see Fig. 6 A). Slices were submerged in ACSF without APV at 35.5 0.5°C saturated with 95% O 2 and 5% CO 2 and recordings were performed at a flow rate of 2 ...
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... neuronal propagation as described in the above para- graphs might be affected by the specific culture condition, we further examined propagation of synchronized, negative LFPs in mature, acute slices from rat primary motor and somatosensory cortex. Spontaneous activity was induced pharmacologically by increasing the NMDA-mediated sustained excitation in the cor- tical networks ( Seamans et al., 2001) through bath application of the glutamate receptor agonist NMDA and the dopamine D 1 - receptor agonist SKF-38393, which robustly induced spontane- ous LFP activity (Fig. 6). Similarly as in the organotypic cortex cultures, LFPs had a typical time course of a negative peak fol- lowed by a longer-lasting depolarization. Many electrodes initi- ated spontaneous LFPs in the acute slices, and neuronal ava- lanches typically encompassed a spatial extent of up to 10 -15 neighboring electrodes (Fig. 6 B). Spontaneous activity lasted on average for 1780 448 sec (n 9 acute slices) and correlation between LFPs declined sharply within 50 -80 msec, resulting in an IEI avg 3.73 0.467. At the closest integer of t 4 msec, this activity had a contiguity index of 28 9% and was composed of on average 505 420 avalanches (rate, 966 590 avalanches/ hr) (Fig. 6C). The event size distributions for spontaneous activ- ity in the acute slices clearly revealed the initial signature of the same power law as was described for the cultured networks (Fig. 6 D,E). The average initial slope values for acute slices were 1.50 0.08 for LFP (r 0.95; 10 -80 V) and 1.58 0.04 for electrode data (r 0.999; 1-8 electrodes). Thus, neuronal ava- lanches also exist in acute, mature cortex slices and display a characteristic exponent of 3/2. However, neuronal avalanches in acute slices are more compact and spatially restricted to fewer electrodes compared with the neuronal culture. This is indicated by the exponential cutoff of the power law (Fig. 6 E) and most likely reflects the severed long-range cortical connectivity in the acute slice. Finally, the lifetime distribution for neuronal avalanches in acute slices was also characterized by an initial slope close to 2 and an exponential cutoff, as was described for neuronal ava- lanches in organotypic cortex cultures (Fig. 6 E, ...
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... neuronal propagation as described in the above para- graphs might be affected by the specific culture condition, we further examined propagation of synchronized, negative LFPs in mature, acute slices from rat primary motor and somatosensory cortex. Spontaneous activity was induced pharmacologically by increasing the NMDA-mediated sustained excitation in the cor- tical networks ( Seamans et al., 2001) through bath application of the glutamate receptor agonist NMDA and the dopamine D 1 - receptor agonist SKF-38393, which robustly induced spontane- ous LFP activity (Fig. 6). Similarly as in the organotypic cortex cultures, LFPs had a typical time course of a negative peak fol- lowed by a longer-lasting depolarization. Many electrodes initi- ated spontaneous LFPs in the acute slices, and neuronal ava- lanches typically encompassed a spatial extent of up to 10 -15 neighboring electrodes (Fig. 6 B). Spontaneous activity lasted on average for 1780 448 sec (n 9 acute slices) and correlation between LFPs declined sharply within 50 -80 msec, resulting in an IEI avg 3.73 0.467. At the closest integer of t 4 msec, this activity had a contiguity index of 28 9% and was composed of on average 505 420 avalanches (rate, 966 590 avalanches/ hr) (Fig. 6C). The event size distributions for spontaneous activ- ity in the acute slices clearly revealed the initial signature of the same power law as was described for the cultured networks (Fig. 6 D,E). The average initial slope values for acute slices were 1.50 0.08 for LFP (r 0.95; 10 -80 V) and 1.58 0.04 for electrode data (r 0.999; 1-8 electrodes). Thus, neuronal ava- lanches also exist in acute, mature cortex slices and display a characteristic exponent of 3/2. However, neuronal avalanches in acute slices are more compact and spatially restricted to fewer electrodes compared with the neuronal culture. This is indicated by the exponential cutoff of the power law (Fig. 6 E) and most likely reflects the severed long-range cortical connectivity in the acute slice. Finally, the lifetime distribution for neuronal avalanches in acute slices was also characterized by an initial slope close to 2 and an exponential cutoff, as was described for neuronal ava- lanches in organotypic cortex cultures (Fig. 6 E, ...
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... neuronal propagation as described in the above para- graphs might be affected by the specific culture condition, we further examined propagation of synchronized, negative LFPs in mature, acute slices from rat primary motor and somatosensory cortex. Spontaneous activity was induced pharmacologically by increasing the NMDA-mediated sustained excitation in the cor- tical networks ( Seamans et al., 2001) through bath application of the glutamate receptor agonist NMDA and the dopamine D 1 - receptor agonist SKF-38393, which robustly induced spontane- ous LFP activity (Fig. 6). Similarly as in the organotypic cortex cultures, LFPs had a typical time course of a negative peak fol- lowed by a longer-lasting depolarization. Many electrodes initi- ated spontaneous LFPs in the acute slices, and neuronal ava- lanches typically encompassed a spatial extent of up to 10 -15 neighboring electrodes (Fig. 6 B). Spontaneous activity lasted on average for 1780 448 sec (n 9 acute slices) and correlation between LFPs declined sharply within 50 -80 msec, resulting in an IEI avg 3.73 0.467. At the closest integer of t 4 msec, this activity had a contiguity index of 28 9% and was composed of on average 505 420 avalanches (rate, 966 590 avalanches/ hr) (Fig. 6C). The event size distributions for spontaneous activ- ity in the acute slices clearly revealed the initial signature of the same power law as was described for the cultured networks (Fig. 6 D,E). The average initial slope values for acute slices were 1.50 0.08 for LFP (r 0.95; 10 -80 V) and 1.58 0.04 for electrode data (r 0.999; 1-8 electrodes). Thus, neuronal ava- lanches also exist in acute, mature cortex slices and display a characteristic exponent of 3/2. However, neuronal avalanches in acute slices are more compact and spatially restricted to fewer electrodes compared with the neuronal culture. This is indicated by the exponential cutoff of the power law (Fig. 6 E) and most likely reflects the severed long-range cortical connectivity in the acute slice. Finally, the lifetime distribution for neuronal avalanches in acute slices was also characterized by an initial slope close to 2 and an exponential cutoff, as was described for neuronal ava- lanches in organotypic cortex cultures (Fig. 6 E, ...
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... neuronal propagation as described in the above para- graphs might be affected by the specific culture condition, we further examined propagation of synchronized, negative LFPs in mature, acute slices from rat primary motor and somatosensory cortex. Spontaneous activity was induced pharmacologically by increasing the NMDA-mediated sustained excitation in the cor- tical networks ( Seamans et al., 2001) through bath application of the glutamate receptor agonist NMDA and the dopamine D 1 - receptor agonist SKF-38393, which robustly induced spontane- ous LFP activity (Fig. 6). Similarly as in the organotypic cortex cultures, LFPs had a typical time course of a negative peak fol- lowed by a longer-lasting depolarization. Many electrodes initi- ated spontaneous LFPs in the acute slices, and neuronal ava- lanches typically encompassed a spatial extent of up to 10 -15 neighboring electrodes (Fig. 6 B). Spontaneous activity lasted on average for 1780 448 sec (n 9 acute slices) and correlation between LFPs declined sharply within 50 -80 msec, resulting in an IEI avg 3.73 0.467. At the closest integer of t 4 msec, this activity had a contiguity index of 28 9% and was composed of on average 505 420 avalanches (rate, 966 590 avalanches/ hr) (Fig. 6C). The event size distributions for spontaneous activ- ity in the acute slices clearly revealed the initial signature of the same power law as was described for the cultured networks (Fig. 6 D,E). The average initial slope values for acute slices were 1.50 0.08 for LFP (r 0.95; 10 -80 V) and 1.58 0.04 for electrode data (r 0.999; 1-8 electrodes). Thus, neuronal ava- lanches also exist in acute, mature cortex slices and display a characteristic exponent of 3/2. However, neuronal avalanches in acute slices are more compact and spatially restricted to fewer electrodes compared with the neuronal culture. This is indicated by the exponential cutoff of the power law (Fig. 6 E) and most likely reflects the severed long-range cortical connectivity in the acute slice. Finally, the lifetime distribution for neuronal avalanches in acute slices was also characterized by an initial slope close to 2 and an exponential cutoff, as was described for neuronal ava- lanches in organotypic cortex cultures (Fig. 6 E, ...
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... neuronal propagation as described in the above para- graphs might be affected by the specific culture condition, we further examined propagation of synchronized, negative LFPs in mature, acute slices from rat primary motor and somatosensory cortex. Spontaneous activity was induced pharmacologically by increasing the NMDA-mediated sustained excitation in the cor- tical networks ( Seamans et al., 2001) through bath application of the glutamate receptor agonist NMDA and the dopamine D 1 - receptor agonist SKF-38393, which robustly induced spontane- ous LFP activity (Fig. 6). Similarly as in the organotypic cortex cultures, LFPs had a typical time course of a negative peak fol- lowed by a longer-lasting depolarization. Many electrodes initi- ated spontaneous LFPs in the acute slices, and neuronal ava- lanches typically encompassed a spatial extent of up to 10 -15 neighboring electrodes (Fig. 6 B). Spontaneous activity lasted on average for 1780 448 sec (n 9 acute slices) and correlation between LFPs declined sharply within 50 -80 msec, resulting in an IEI avg 3.73 0.467. At the closest integer of t 4 msec, this activity had a contiguity index of 28 9% and was composed of on average 505 420 avalanches (rate, 966 590 avalanches/ hr) (Fig. 6C). The event size distributions for spontaneous activ- ity in the acute slices clearly revealed the initial signature of the same power law as was described for the cultured networks (Fig. 6 D,E). The average initial slope values for acute slices were 1.50 0.08 for LFP (r 0.95; 10 -80 V) and 1.58 0.04 for electrode data (r 0.999; 1-8 electrodes). Thus, neuronal ava- lanches also exist in acute, mature cortex slices and display a characteristic exponent of 3/2. However, neuronal avalanches in acute slices are more compact and spatially restricted to fewer electrodes compared with the neuronal culture. This is indicated by the exponential cutoff of the power law (Fig. 6 E) and most likely reflects the severed long-range cortical connectivity in the acute slice. Finally, the lifetime distribution for neuronal avalanches in acute slices was also characterized by an initial slope close to 2 and an exponential cutoff, as was described for neuronal ava- lanches in organotypic cortex cultures (Fig. 6 E, ...
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... neuronal propagation as described in the above para- graphs might be affected by the specific culture condition, we further examined propagation of synchronized, negative LFPs in mature, acute slices from rat primary motor and somatosensory cortex. Spontaneous activity was induced pharmacologically by increasing the NMDA-mediated sustained excitation in the cor- tical networks ( Seamans et al., 2001) through bath application of the glutamate receptor agonist NMDA and the dopamine D 1 - receptor agonist SKF-38393, which robustly induced spontane- ous LFP activity (Fig. 6). Similarly as in the organotypic cortex cultures, LFPs had a typical time course of a negative peak fol- lowed by a longer-lasting depolarization. Many electrodes initi- ated spontaneous LFPs in the acute slices, and neuronal ava- lanches typically encompassed a spatial extent of up to 10 -15 neighboring electrodes (Fig. 6 B). Spontaneous activity lasted on average for 1780 448 sec (n 9 acute slices) and correlation between LFPs declined sharply within 50 -80 msec, resulting in an IEI avg 3.73 0.467. At the closest integer of t 4 msec, this activity had a contiguity index of 28 9% and was composed of on average 505 420 avalanches (rate, 966 590 avalanches/ hr) (Fig. 6C). The event size distributions for spontaneous activ- ity in the acute slices clearly revealed the initial signature of the same power law as was described for the cultured networks (Fig. 6 D,E). The average initial slope values for acute slices were 1.50 0.08 for LFP (r 0.95; 10 -80 V) and 1.58 0.04 for electrode data (r 0.999; 1-8 electrodes). Thus, neuronal ava- lanches also exist in acute, mature cortex slices and display a characteristic exponent of 3/2. However, neuronal avalanches in acute slices are more compact and spatially restricted to fewer electrodes compared with the neuronal culture. This is indicated by the exponential cutoff of the power law (Fig. 6 E) and most likely reflects the severed long-range cortical connectivity in the acute slice. Finally, the lifetime distribution for neuronal avalanches in acute slices was also characterized by an initial slope close to 2 and an exponential cutoff, as was described for neuronal ava- lanches in organotypic cortex cultures (Fig. 6 E, ...
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Background: Neural circuits can spontaneously generate complex spatiotemporal firing patterns during development. This spontaneous activity is thought to help guide development of the nervous system. In this study, we had two aims. First, to characterise the changes in spontaneous activity in cultures of developing networks of either hippocampal or...
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... beta bursts) (Brown et al. 2004;Kuhn et al. 2008;Oswal et al. 2016b;Trager et al. 2016;Tinkhauser et al. 2017;Wang et al. 2018). More recently, a new perspective has focused on the scale-free properties of large-scale activities (Beggs et Plenz 2003;Shriki et al. 2013). Aperiodic, spontaneous bursts spreading across a range of spatial and temporal scales ("neuronal avalanches") have been consistently observed across different imaging modalities and spatio-temporal scales (Priesemann et al. 2013;Palva et al. 2013;Tagliazucchi et al. 2012). ...
... When a brain signal has a z-score above this threshold, it is classified as active (assigned a value of 1), while all other time points are considered inactive (assigned a value of 0). A neuronal avalanche initiates when, in a sequence of consecutive time bins, at least one channel becomes active (|z| > 2) and concludes when all channels return to an inactive state (Beggs et Plenz 2003;Shriki et al. 2013). ...
... Then, we conducted the K-S test to compare the distributions of these features between ON and OFF conditions. The reason behind choosing the K-S test earlier in the manuscript is its lack of assumptions of gaussianity, given the non-linear, fat-tailed nature of avalanche dynamics (Beggs et Plenz 2003). ...
Parkinson's disease (PD) is a neurodegenerative disease primarily characterized by severe motor symptoms that can be transiently relieved by medication (e.g. levodopa). These symptoms are mirrored by widespread alterations of neuronal activities across the whole brain, whose characteristics at the large scale level are still poorly understood. To address this issue, we measured the resting state activities of 11 PD patients utilizing different devices, i.e deep brain stimulation (DBS) contacts placed within the subthalamic nucleus area, and EEG electrodes placed above the motor areas. Data were recorded in each patient before drug administration (OFF-condition) and after drug administration (ON-condition). Neuronal avalanches, i.e. brief bursts of activity with widespread propagation, were detected and quantified on both types of contacts, and used to characterize differences in both conditions. Of particular interest, we noted a larger number of shorter and smaller avalanches in the OFF-condition, and a lesser number of wider and longer avalanches in the ON-condition. This difference turned out to be statistically significant at the group level. Then, we computed the avalanche transition matrices (ATM) to track the contact-wise patterns of avalanche spread. We compared the two conditions and observed a higher probability that an avalanche would spread within and between STN and motor cortex in the ON-state, with highly significant differences at the group level. Furthermore, we discovered that the increase in overall propagation of avalanches was correlated to clinical improvement after levodopa administration. Our results provide the first cross-modality assessment of aperiodic activities in PD patients, and the first account of the changes induced by levodopa on cross-regional aperiodic bursts at the individual level, and could open new avenues toward developing biomarkers of PD electrophysiological alterations.
... Fields of physical phenomena that exhibit these behaviors include turbulence in fluid mechanics, non-equilibrium thermodynamics, biology, vision, finance and imagery [8,44,45]. In these domains, an history of studies has demonstrated the coherence between concepts such as fractal behavior, pattern orientation, the 1/ spectral response of continuous models and Self-Organized Criticality [15,46,47]. The following simulations are inspired by those studies and aim at best reproduce the described behavior of images [48]. ...
Distribution of colors and patterns in images is observed through cascades that adjust spatial resolution and dynamics. Cascades of colors reveal the emergent universal property that Fully Colored Images (FCIs) of natural scenes adhere to the debated continuous linear log-scale law (slope $-2.00 \pm 0.01$) (L1). Cascades of discrete $2 \times 2$ patterns are derived from pixel squares reductions onto the seven unlabeled rotation-free textures (0000, 0001, 0011, 0012, 0101, 0102, 0123). They exhibit an unparalleled universal entropy maximum of $1.74 \pm 0.013$ at some dynamics regardless of spatial scale (L2). Patterns also adhere to the Integral Fluctuation Theorem ($1.00 \pm 0.01$) (L3), pivotal in studies of chaotic systems. Images with fewer colors exhibit quadratic shift and bias from L1 and L3 but adhere to L2. Randomized Hilbert fractals FCIs better match the laws than basic-to-AI-based simulations. Those results are of interest in Neural Networks, out of equilibrium physics and spectral imagery.
... Network Topology of Real World Systems Many complex real-world systems have a characteristic network topology (Watts & Strogatz, 1998;, for instance, a small-world topology shared by many biological and social systems (Kleinberg, 2000;Amaral et al., 2000;Bassett & Bullmore, 2006;Rubinov et al., 2009;Muldoon et al., 2016), or a scale-free topology observed in brain anatomy and dynamics (Beggs & Plenz, 2003;Eguiluz et al., 2005;van den Heuvel et al., 2008;Rubinov et al., 2009). Scale-free networks are characterized by the existence of central nodes or 'hubs', possibly linked to a hierarchical organization in the system (Ravasz & Barabási, 2003). ...
In dynamical systems reconstruction (DSR) we seek to infer from time series measurements a generative model of the underlying dynamical process. This is a prime objective in any scientific discipline, where we are particularly interested in parsimonious models with a low parameter load. A common strategy here is parameter pruning, removing all parameters with small weights. However, here we find this strategy does not work for DSR, where even low magnitude parameters can contribute considerably to the system dynamics. On the other hand, it is well known that many natural systems which generate complex dynamics, like the brain or ecological networks, have a sparse topology with comparatively few links. Inspired by this, we show that geometric pruning, where in contrast to magnitude-based pruning weights with a low contribution to an attractor's geometrical structure are removed, indeed manages to reduce parameter load substantially without significantly hampering DSR quality. We further find that the networks resulting from geometric pruning have a specific type of topology, and that this topology, and not the magnitude of weights, is what is most crucial to performance. We provide an algorithm that automatically generates such topologies which can be used as priors for generative modeling of dynamical systems by RNNs, and compare it to other well studied topologies like small-world or scale-free networks.
... Resting state activity throughout the brain shows strong coherent spontaneous fluctuations driven by the coordinated activity patterns of many cells (Pachitariu et al., 2015;Stringer et al., 2016). Multiple studies have suggested neural dynamics is "critical" (Beggs and Plenz, 2003;Chialvo, 2004) and resides in a regime close to losing stability. Our work suggests that pathology like PD may move the network out of an optimal regime for computation, and while L-DOPA normalizes activity to some degree by normalizing inhibition, it can also "overshoot" and generate too much excitation. ...
Under normal conditions the principal cells of the striatum, medium spiny neurons (MSNs), show structured cell assembly activity patterns which alternate sequentially over exceedingly long timescales of many minutes. It is important to understand this activity since it is characteristically disrupted in multiple pathologies, such as Parkinson's disease and dyskinesia, and thought to be caused by alterations in the MSN to MSN lateral inhibitory connections and in the strength and distribution of cortical excitation to MSNs. To understand how these long timescales arise we extended a previous network model of MSN cells to include synapses with short-term plasticity, with parameters taken from a recent detailed striatal connectome study. We first confirmed the presence of sequentially switching cell clusters using the non-linear dimensionality reduction technique, Uniform Manifold Approximation and Projection (UMAP). We found that the network could generate non-stationary activity patterns varying extremely slowly on the order of minutes under biologically realistic conditions. Next we used Simulation Based Inference (SBI) to train a deep net to map features of the MSN network generated cell assembly activity to MSN network parameters. We used the trained SBI model to estimate MSN network parameters from ex-vivo brain slice calcium imaging data. We found that best fit network parameters were very close to their physiologically observed values. On the other hand network parameters estimated from Parkinsonian, decorticated and dyskinetic ex-vivo slice preparations were different. Our work may provide a pipeline for diagnosis of basal ganglia pathology from spiking data as well as for the design pharmacological treatments.
... Our data provide the first evidence in support of this 372 hypothesis by revealing that caffeine induces a flattening of the 1/f slope and a drop in 373 the scaling exponent. Indeed, both modeling and experimental studies have shown that 374 reductions in the 1/f slope (or the related scaling exponent and Hurst exponent) reflect 375 an increase in E:I ratio [49,50,[52][53][54][55]. 376 Interestingly, the link we make here between caffeine's antagonistic effect on 377 adenosine receptors and the observed shift in criticality is conceptually consistent with 378 previous research showing that by blocking GABA receptors and reducing inhibitory 379 synaptic transmission, an artificial upward shift in excitation can occur, leading to a 380 supercritical state with larger-than-expected neuronal avalanches [56,57]. ...
Caffeine is the most widely consumed psychoactive stimulant worldwide. Yet important gaps persist in understanding its effects on the brain, especially during sleep. We analyzed sleep EEG in 40 subjects, contrasting 200mg of caffeine against a placebo condition, utilizing inferential statistics and machine learning. We found that caffeine ingestion led to an increase in brain complexity, a widespread flattening of the power spectrum's 1/f-like slope, and a reduction in long-range temporal correlations. Being most prominent during non-REM sleep, these results suggest that caffeine shifts the brain towards a critical regime and more diverse neural dynamics. Interestingly, this was more pronounced in younger adults (20-27 years) compared to middle-aged participants (41-58 years) whose sleep brain dynamics were less affected by caffeine. Interpreting these data in the light of modeling and empirical work on EEG-derived measures of excitation-inhibition balance provides novel insights into the effects caffeine has on the sleeping brain.
... Our analysis of spatiotemporal clusters of frequencies associated with desynchronization suggests desynchronization spreads heterogeneously in space and time with no characteristic scale (i.e., scale-free), reminiscent of a critical mean-field directed percolation (MFDP) spreading process. This reframes REM-like dynamics as a scale-free perturbation away from a synchronized state (nREM), providing strong evidence for neural dynamics operating between a totally synchronized and desynchronized phase-i.e., an "edge-of-synchronization" phase transition-opening a novel perspective on collective neural dynamics in the form of desynchronization avalanches, and complementing ongoing research into brain criticality and critical neuronal avalanches [23,24]. ...
Sleep is characterized by nonrapid eye movement sleep, originating from widespread neuronal synchrony, and rapid eye movement sleep, with neuronal desynchronization akin to waking behavior. While these were thought to be global brain states, recent research suggests otherwise. Using time-frequency analysis of mesoscopic voltage-sensitive dye recordings of mice in a urethane-anesthetized model of sleep, we find transient neural desynchronization occurring heterogeneously across the cortex within a background of synchronized neural activity, in a manner reminiscent of a critical spreading process and indicative of an “edge-of-synchronization” phase transition.
... The concept of criticality in living systems has attracted growing interest in recent decades due to its potential to shed light on the behavior of complex biological systems, including the brain [1][2][3][4][5][6]. In particular, since the first observation of power-law-distributed neuronal avalanches in slices of the rat cortex by Beggs and Plenz [2], the critical brain hypothesis [4,5,7,8] has been intensively investigated both theoretically [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] and in diverse experimental setups . ...
... The concept of criticality in living systems has attracted growing interest in recent decades due to its potential to shed light on the behavior of complex biological systems, including the brain [1][2][3][4][5][6]. In particular, since the first observation of power-law-distributed neuronal avalanches in slices of the rat cortex by Beggs and Plenz [2], the critical brain hypothesis [4,5,7,8] has been intensively investigated both theoretically [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] and in diverse experimental setups . ...
... Amongst the brain areas, the cerebral cortex has been the focal point in the exploration of the critical brain hypothesis, mainly the primary sensory cortices [2,4,34,43,48,49]. Such cortical areas play a paramount role in sensory processing from the environmental stimuli [50]. ...
The presumed proximity to a critical point is believed to endow the brain with scale-invariant statistics, which are thought to confer various functional advantages in terms of its information processing, storage, and transmission capabilities. To assess the relationship between scaling and cortical states, we apply a phenomenological renormalization group analysis to 3-h spiking data recordings from the urethane-anesthetized rat's visual cortex. Under this type of anesthesia, cortical states dynamically shift across a spectrum of synchronization levels, defined by population spiking rate variability. By developing a scaling criterion based on the kurtosis of the momentum-space activity distribution, our study combines the coarse-graining method with state-dependent analysis. We find that scaling signatures only appear as spiking variability surpasses a specified threshold. Notably, within this regime, scaling exponents show relative stability. Conversely, subthreshold activity is primarily asynchronous and fails to meet the scaling criterion. Our results suggest that a wide range of cortical states corresponds to small deviations around a critical point, with the system fluctuating in and out of criticality, spending roughly three-quarters of the experiment duration within a scaling regime.
Published by the American Physical Society 2024
... Brain activity displays a plethora of different dynamical states, including bursts, oscillations, and irregular activity. In particular, neural activity exhibits spatiotemporal patterns compatible with the dynamics of a system close to a second-order phase transition, namely the critical point [1][2][3][4][5]. Operating at this regime has been linked to optimal information processing [2,6], efficient coding [7], maximal dynamic range and sensitivity to stimulus [8,9], longer timescales during attention [10], and better stimuli discrimination [11,12]. ...
... To assess whether the brain operates at criticality, the activity propagation between the neurons is often mapped to the branching process [1][2][3][4][5]8,[15][16][17]. This mapping was motivated by the observation of outbursts of neural activity in vitro known as neuronal avalanches [1]. ...
... To assess whether the brain operates at criticality, the activity propagation between the neurons is often mapped to the branching process [1][2][3][4][5]8,[15][16][17]. This mapping was motivated by the observation of outbursts of neural activity in vitro known as neuronal avalanches [1]. Each avalanche consists of periods of activity, separated by quiescence moments. ...
Studies of neural avalanches across different data modalities led to the prominent hypothesis that the brain operates near a critical point. The observed exponents often indicate the mean-field directed-percolation universality class, leading to the fully connected or random network models to study the avalanche dynamics. However, cortical networks have distinct nonrandom features and spatial organization that is known to affect critical exponents. Here we show that distinct empirical exponents arise in networks with different topology and depend on the network size. In particular, we find apparent scale-free behavior with mean-field exponents appearing as quasicritical dynamics in structured networks. This quasicritical dynamics cannot be easily discriminated from an actual critical point in small networks. We find that the local coalescence in activity dynamics can explain the distinct exponents. Therefore, both topology and system size should be considered when assessing criticality from empirical observables.
Published by the American Physical Society 2024
... The Brain Criticality hypothesis states that the critical point is central to the processing of information in the healthy brain. [8][9][10][11] Several studies show the presence of a critical state, with powerlaw-distributed neuronal avalanches and other scaling properties (for reviews, see Refs. [12][13][14][15]. ...
... [12][13][14][15]. The originally observed critical point was conjectured to separate an inactive state from a synchronous epileptic-like state, 8 although most of the theoretical works that followed relied on absorbing 16 or Ising universality classes 17 (a continuous phase transition between an inactive/disordered and an active/ordered state, where there is no synchronization). In such models, homeostatic mechanisms in synaptic coupling, 18 in firing gain, 19 or in multiple variables [20][21][22] lead to hovering around the critical point. ...
... In the early observation of neuronal avalanches, seizures were hypothesized to correspond to a supercritical state with synchronized spikes and oscillations at the average population voltage. 8 Other authors have also suggested that epilepsy is related to the loss of criticality, [69][70][71] but no mechanism has been proposed. A synchronization transition can be used as a simple model for epileptic seizures. ...
Transient or partial synchronization can be used to do computations, although a fully synchronized network is sometimes related to the onset of epileptic seizures. Here, we propose a homeostatic mechanism that is capable of maintaining a neuronal network at the edge of a synchronization transition, thereby avoiding the harmful consequences of a fully synchronized network. We model neurons by maps since they are dynamically richer than integrate-and-fire models and more computationally efficient than conductance-based approaches. We first describe the synchronization phase transition of a dense network of neurons with different tonic spiking frequencies coupled by gap junctions. We show that at the transition critical point, inputs optimally reverberate through the network activity through transient synchronization. Then, we introduce a local homeostatic dynamic in the synaptic coupling and show that it produces a robust self-organization toward the edge of this phase transition. We discuss the potential biological consequences of this self-organization process, such as its relation to the Brain Criticality hypothesis, its input processing capacity, and how its malfunction could lead to pathological synchronization and the onset of seizure-like activity.
... In preparation for the discussion of the field-theoretical model of cortical dynamics, we draw on empirical evidence supporting the decisive role of neurotransmitters in triggering phase transitions. To start with, the propagation of synchronized activity in cortical networks is shown to manifest as neuronal avalanches with sizes and lifetimes obeying power law scaling, which is indicative of a system operating in the critical regime (Beggs and Plenz, 2003;Lombardi et al., 2014;Arviv et al., 2019;Plenz et al., 2021). These avalanches reflect the collective organization of cortical activity (Arviv et al., 2019), a key finding being that this organization is driven by the neurotransmitters glutamate and gamma-aminobutyric acid (GABA), as well as the presence of neuromodulators, such as dopamine, serotonin, and acetylcholine (Stewart and Plenz, 2006;Plenz et al., 2021). ...
Empirical evidence indicates that conscious states, distinguished by the presence of phenomenal qualities, are closely linked to synchronized neural activity patterns whose dynamical characteristics can be attributed to self-organized criticality and phase transitions. These findings imply that insight into the mechanism by which the brain controls phase transitions will provide a deeper understanding of the fundamental mechanism by which the brain manages to transcend the threshold of consciousness. This article aims to show that the initiation of phase transitions and the formation of synchronized activity patterns is due to the coupling of the brain to the zero-point field (ZPF), which plays a central role in quantum electrodynamics (QED). The ZPF stands for the presence of ubiquitous vacuum fluctuations of the electromagnetic field, represented by a spectrum of normal modes. With reference to QED-based model calculations, the details of the coupling mechanism are revealed, suggesting that critical brain dynamics is governed by the resonant interaction of the ZPF with the most abundant neurotransmitter glutamate. The pyramidal neurons in the cortical microcolumns turn out to be ideally suited to control this interaction. A direct consequence of resonant glutamate-ZPF coupling is the amplification of specific ZPF modes, which leads us to conclude that the ZPF is the key to the understanding of consciousness and that the distinctive feature of neurophysiological processes associated with conscious experience consists in modulating the ZPF. Postulating that the ZPF is an inherently sentient field and assuming that the spectrum of phenomenal qualities is represented by the normal modes of the ZPF, the significance of resonant glutamate-ZPF interaction for the formation of conscious states becomes apparent in that the amplification of specific ZPF modes is inextricably linked with the excitation of specific phenomenal qualities. This theory of consciousness, according to which phenomenal states arise through resonant amplification of zero-point modes, is given the acronym TRAZE. An experimental setup is specified that can be used to test a corollary of the theory, namely, the prediction that normally occurring conscious perceptions are absent under experimental conditions in which resonant glutamate-ZPF coupling is disrupted.
