J. Buldú - Academia.edu (original) (raw)
Papers by J. Buldú
Scientific Reports, 2020
We investigated the ability of football teams to develop a particular playing style by looking at... more We investigated the ability of football teams to develop a particular playing style by looking at their passing patterns. Using the information contained in the pass sequences during matches, we constructed the pitch passing networks of teams, whose nodes are the divisions of the pitch for a given spatial scale and links account for the number of passes from region to region. We translated football passings networks into their corresponding adjacency matrices. We calculated the correlations between matrices of the same team to quantify how consistent the passing patterns of a given team are. Next, we quantified the differences with other teams’ matrices and obtained an identifiability parameter that indicates how unique are the passing patterns of a given team. Consistency and identifiability rankings were calculated during a whole season, allowing to detect those teams of a league whose passing patterns are different from the rest. Furthermore, we found differences between teams pl...
Scientific Reports, 2019
The application of Network Science to social systems has introduced new methodologies to analyze ... more The application of Network Science to social systems has introduced new methodologies to analyze classical problems such as the emergence of epidemics, the arousal of cooperation between individuals or the propagation of information along social networks. More recently, the organization of football teams and their performance have been unveiled using metrics coming from Network Science, where a team is considered as a complex network whose nodes (i.e., players) interact with the aim of overcoming the opponent network. Here, we combine the use of different network metrics to extract the particular signature of the F.C. Barcelona coached by Guardiola, which has been considered one of the best teams along football history. We have first compared the network organization of Guardiola’s team with their opponents along one season of the Spanish national league, identifying those metrics with statistically significant differences and relating them with the Guardiola’s game. Next, we have f...
Coherence resonance occurring in semiconductor lasers with optical feedback is studied via the La... more Coherence resonance occurring in semiconductor lasers with optical feedback is studied via the Lang-Kobayashi model with external non-white noise in the pumping current. The temporal correlation and the amplitude of the noise have a highly relevant influence in the system, leading to an optimal coherent response for suitable values of both the noise amplitude and correlation time. This phenomenon is quantitatively characterized by means of several statistical measures.
Physical Review E, 2002
We show that the natural pulsed behavior, in the form of sudden power dropouts, exhibited by semi... more We show that the natural pulsed behavior, in the form of sudden power dropouts, exhibited by semiconductor lasers subject to optical feedback can be entrained by the joint action of external noise and weak periodic driving. These power dropouts, which in the absence of forcing do not occur periodically, acquire the periodicity of the harmonic driving for an optimal amount of external noise, in what constitutes a form of stochastic resonance. This phenomenon is analyzed by means of a generalized Lang-Kobayashi model with external nonwhite noise in the modulated pump current, in terms of both the temporal correlation and the amplitude of the noise.
Physical Review Letters, 2006
We show that simultaneous synchronization between two delay-coupled oscillators can be achieved b... more We show that simultaneous synchronization between two delay-coupled oscillators can be achieved by relaying the dynamics via a third mediating element, which surprisingly lags behind the synchronized outer elements. The zero-lag synchronization thus obtained is robust over a considerable parameter range. We substantiate our claims with experimental and numerical evidence of these synchronization solutions in a chain of three coupled semiconductor lasers with long inter-element coupling delays. The generality of the mechanism is validated in a neuronal model with the same coupling architecture. Thus, our results show that synchronized dynamical states can occur over long distances through relaying, without restriction by the amount of delay.
Physical Review E, 2004
We study the influence of the delay time in the response of a delayed feedback system to external... more We study the influence of the delay time in the response of a delayed feedback system to external periodic driving. The nonlinear system we consider is a semiconductor laser with optical feedback operating in the low-frequency fluctuation regime. We numerically examine the consequences of varying the external cavity length of the system when a weak modulation is introduced through the laser's pump current. The harmonic modulation is seen to lead to a partial periodic entrainment of power dropouts, and the distribution of time intervals between the dropouts exhibits resonances with certain delay times. In other words, the response of the system to the external modulation is enhanced for particular values of the external cavity length. The same effect can be observed in the presence of noise, indicating that stochastic resonance can be enhanced or degraded depending on the feedback time.
Journal of Optics B: Quantum and Semiclassical Optics, 2002
We study the multimode dynamics of a semiconductor laser with optical feedback operating in the l... more We study the multimode dynamics of a semiconductor laser with optical feedback operating in the low-frequency fluctuation regime. A multimode extension of the Lang-Kobayashi (LK) model shows, in agreement with experimental observations, that the low-frequency power dropouts exhibited by the main modes are accompanied by sudden, asymmetric, activations of dormant longitudinal side modes. Furthermore, these activations are delayed with respect to the dropouts of the active modes. In order to satisfactorily reproduce both the asymmetric activation of side modes and their delay with respect to the dropouts, the generalized LK model has to include a parabolic gain profile, together with a frequency shift of the gain curve with carrier population.
Journal of Optics B: Quantum and Semiclassical Optics, 2002
The dynamics of power distribution between longitudinal modes of a multimode semiconductor laser ... more The dynamics of power distribution between longitudinal modes of a multimode semiconductor laser subjected to external optical feedback is experimentally analysed in the low-frequency fluctuation regime. Power dropouts in the total light intensity are invariably accompanied by sudden activations of several longitudinal modes. These activations are seen not to be simultaneous to the dropouts, but to occur after them. The phenomenon is statistically analysed in a systematic way, and the corresponding delay is estimated.
Fluctuation and Noise Letters, 2003
The control of the low-frequency fluctuations exhibited by two mutually coupled semiconductor las... more The control of the low-frequency fluctuations exhibited by two mutually coupled semiconductor lasers is studied experimentally and numerically. We observe that coupling enhances the response of the system to a weak periodic modulation of the injection current of one of the lasers, leading to a highly efficient entrainment of the synchronized low-frequency power dropouts to the external periodic driving. We compare the quality of the entrainment with the one obtained in a single semiconductor laser with optical feedback, showing the beneficial role of coupling in this pursuit. The experimental observations are satisfactorily reproduced by numerical simulations of a set of coupled delay-differential rate equations.
Europhysics Letters (EPL), 2003
We show both experimentally and numerically a ghost resonance in the sudden power dropouts exhibi... more We show both experimentally and numerically a ghost resonance in the sudden power dropouts exhibited by a semiconductor laser subject to optical feedback driven by two simultaneous weak periodic signals. The small signal modulation conspires with the complex internal dynamics of the system to produce a resonance at a ghost frequency, i.e. a frequency that is not present in the driving signals. This is an eminently nonlinear effect not reported before and agrees with the recent theoretical predictions by Chialvo et al. (Phys. Rev. E, 65 (2002) 050902(R)). The response of dynamical systems to external driving is a far-reaching problem, with implications ranging from signal detection by sensory systems [1] to information encoding through diode laser modulation in communication systems [2]. In the former context, for instance, recent research efforts have been addressed to understand the perception of complex sounds in auditory systems. To that end, the response of excitable threshold devices to multifrequency signals has been theoretically shown to exhibit a resonance at a frequency which is absent in the input driving [3]. The present letter reports an experimental realization of this ghost resonance in a different type of complex dynamical system, namely a semiconductor laser subject to optical feedback. This system has attracted much attention of the researchers for more than three decades. One of its most interesting characteristic regimes is the lowfrequency fluctuation regime (LFF), in which the output power of the laser suffers sudden dropouts to almost zero power at irregular time intervals when biased close to threshold [4]. Although the LFF behavior was already observed at the end of the seventies, its dynamics is not fully understood yet. Recent experimental [5] and numerical [6, 7] reports show the conditions for which a laser subject to optical feedback and biased close to threshold is able to operate in an excitable
Electronics Letters, 2000
A bidirectional lightwave 100 km transmission system capable of delivering 80 cable television (C... more A bidirectional lightwave 100 km transmission system capable of delivering 80 cable television (CATV) analogue video signals using conventional singlemode fibre (SMF) or large effective area fibre (LEAF) has been demonstrated experimentally for the first time. Elimination of both Rayleigh backscattered crosstalk from the opposite-direction signal and amplified spontaneous emission noise is required to improve the system carrier-to-noise ratio. Satisfactory system performance can be achieved regardless of whether an SMF or LEAF 100 km link is used. However, the composite second-order quality of the LEAF link is superior to that of the SMF link. This technology should play an important role in leased fibre links for trunk delivery between any two multiple system operators across another CATV-operator system.
Applied Physics Letters, 2002
We examine the effect of current modulation in the irregular dropout dynamics exhibited by two mu... more We examine the effect of current modulation in the irregular dropout dynamics exhibited by two mutually coupled semiconductor lasers. Our experimental results show that a weak periodic modulation in the injection current of one of the lasers entrains the power dropouts in a very efficient way. It is also observed that the laser with the highest frequency leads the dynamics independently of which laser is modulated. As a result, the entrainment is anticipative when modulation is applied to the laser with lowest frequency. Numerical simulations of a model based on delay-coupled rate equations successfully reproduce the observed behavior.
Frontiers in Human Neuroscience, 2014
Frontiers in Human Neuroscience, 2016
Nature Communications, 2019
A wide variety of social, biological or technological systems can be described as processes takin... more A wide variety of social, biological or technological systems can be described as processes taking place on networked structures in continuous interaction with other networks. We propose here a new methodology to describe, anticipate and manage, in real time, the out-of-equilibrium dynamics of processes that evolve on interconnected networks. This goal is achieved through the full analytical treatment of the phenomenology and its reduction to a two-dimensional flux diagram, allowing us to predict at every time step the dynamical consequences of modifying the links between the different ensembles. Our results are consistent with real data and the methodology can be translated to clustered networks and/or interconnected networks of any size, topology or origin, from the struggle for knowledge on innovation structures to international economic relations or disease spreading on social groups.
Data in Brief, 2019
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Chaos: An Interdisciplinary Journal of Nonlinear Science, 2017
We investigate the existence of an optimal interplay between the natural frequencies of a group c... more We investigate the existence of an optimal interplay between the natural frequencies of a group chaotic oscillators and the topological properties of the network they are embedded in. We identify the conditions for achieving phase synchronization in the most effective way, i.e., with the lowest possible coupling strength. Specifically, we show by means of numerical and experimental results that it is possible to define a synchrony alignment function J(ω, L) linking the natural frequencies ω i of a set of non-identical phase-coherent chaotic oscillators with the topology of the Laplacian matrix L, the latter accounting for the specific organization of the network of interactions between oscillators. We use the classical Rössler system to show that the synchrony alignment function obtained for phase oscillators can be extended to phase-coherent chaotic systems. Finally, we carry out a series of experiments with nonlinear electronic circuits to show the robustness of the theoretical predictions despite the intrinsic noise and parameter mismatch of the electronic components.
Frontiers in Human Neuroscience, 2015
In this study we used graph theory analysis to investigate age-related reorganization of function... more In this study we used graph theory analysis to investigate age-related reorganization of functional networks during the active maintenance of information that is interrupted by external interference. Additionally, we sought to investigate network differences before and after averaging network parameters between both maintenance and interference windows. We compared young and older adults by measuring their magnetoencephalographic recordings during an interference-based working memory task restricted to successful recognitions. Data analysis focused on the topology/temporal evolution of functional networks during both the maintenance and interference windows. We observed that: (a) Older adults require higher synchronization between cortical brain sites in order to achieve a successful recognition, (b) The main differences between age groups arise during the interference window, (c) Older adults show reduced ability to reorganize network topology when interference is introduced, and (d) Averaging network parameters leads to a loss of sensitivity to detect age differences.
Chaos, Solitons & Fractals, 2015
Increased variability in performance has been associated with the emergence of several neurologic... more Increased variability in performance has been associated with the emergence of several neurological and psychiatric pathologies. However, whether and how consistency of neuronal activity may also be indicative of an underlying pathology is still poorly understood. Here we propose a novel method for evaluating consistency from non-invasive brain recordings. We evaluate the consistency of the cortical activity recorded with magnetoencephalography in a group of subjects diagnosed with Mild Cognitive Impairment (MCI), a condition sometimes prodromal of dementia, during the execution of a memory task. We use metrics coming from nonlinear dynamics to evaluate the consistency of cortical regions. A representation known as parenclitic networks is constructed, where atypical features are endowed with a network structure, the topological properties of which can be studied at various scales. Pathological conditions correspond to strongly heterogeneous networks, whereas typical or normative conditions are characterized by sparsely connected networks with homogeneous nodes. The analysis of this kind of networks allows identifying the extent to which consistency is affected in the MCI group and the focal points where MCI is especially severe. To the best of our knowledge, these results represent the first attempt at evaluating the consistency of brain functional activity using complex networks theory.
Scientific Reports, 2020
We investigated the ability of football teams to develop a particular playing style by looking at... more We investigated the ability of football teams to develop a particular playing style by looking at their passing patterns. Using the information contained in the pass sequences during matches, we constructed the pitch passing networks of teams, whose nodes are the divisions of the pitch for a given spatial scale and links account for the number of passes from region to region. We translated football passings networks into their corresponding adjacency matrices. We calculated the correlations between matrices of the same team to quantify how consistent the passing patterns of a given team are. Next, we quantified the differences with other teams’ matrices and obtained an identifiability parameter that indicates how unique are the passing patterns of a given team. Consistency and identifiability rankings were calculated during a whole season, allowing to detect those teams of a league whose passing patterns are different from the rest. Furthermore, we found differences between teams pl...
Scientific Reports, 2019
The application of Network Science to social systems has introduced new methodologies to analyze ... more The application of Network Science to social systems has introduced new methodologies to analyze classical problems such as the emergence of epidemics, the arousal of cooperation between individuals or the propagation of information along social networks. More recently, the organization of football teams and their performance have been unveiled using metrics coming from Network Science, where a team is considered as a complex network whose nodes (i.e., players) interact with the aim of overcoming the opponent network. Here, we combine the use of different network metrics to extract the particular signature of the F.C. Barcelona coached by Guardiola, which has been considered one of the best teams along football history. We have first compared the network organization of Guardiola’s team with their opponents along one season of the Spanish national league, identifying those metrics with statistically significant differences and relating them with the Guardiola’s game. Next, we have f...
Coherence resonance occurring in semiconductor lasers with optical feedback is studied via the La... more Coherence resonance occurring in semiconductor lasers with optical feedback is studied via the Lang-Kobayashi model with external non-white noise in the pumping current. The temporal correlation and the amplitude of the noise have a highly relevant influence in the system, leading to an optimal coherent response for suitable values of both the noise amplitude and correlation time. This phenomenon is quantitatively characterized by means of several statistical measures.
Physical Review E, 2002
We show that the natural pulsed behavior, in the form of sudden power dropouts, exhibited by semi... more We show that the natural pulsed behavior, in the form of sudden power dropouts, exhibited by semiconductor lasers subject to optical feedback can be entrained by the joint action of external noise and weak periodic driving. These power dropouts, which in the absence of forcing do not occur periodically, acquire the periodicity of the harmonic driving for an optimal amount of external noise, in what constitutes a form of stochastic resonance. This phenomenon is analyzed by means of a generalized Lang-Kobayashi model with external nonwhite noise in the modulated pump current, in terms of both the temporal correlation and the amplitude of the noise.
Physical Review Letters, 2006
We show that simultaneous synchronization between two delay-coupled oscillators can be achieved b... more We show that simultaneous synchronization between two delay-coupled oscillators can be achieved by relaying the dynamics via a third mediating element, which surprisingly lags behind the synchronized outer elements. The zero-lag synchronization thus obtained is robust over a considerable parameter range. We substantiate our claims with experimental and numerical evidence of these synchronization solutions in a chain of three coupled semiconductor lasers with long inter-element coupling delays. The generality of the mechanism is validated in a neuronal model with the same coupling architecture. Thus, our results show that synchronized dynamical states can occur over long distances through relaying, without restriction by the amount of delay.
Physical Review E, 2004
We study the influence of the delay time in the response of a delayed feedback system to external... more We study the influence of the delay time in the response of a delayed feedback system to external periodic driving. The nonlinear system we consider is a semiconductor laser with optical feedback operating in the low-frequency fluctuation regime. We numerically examine the consequences of varying the external cavity length of the system when a weak modulation is introduced through the laser's pump current. The harmonic modulation is seen to lead to a partial periodic entrainment of power dropouts, and the distribution of time intervals between the dropouts exhibits resonances with certain delay times. In other words, the response of the system to the external modulation is enhanced for particular values of the external cavity length. The same effect can be observed in the presence of noise, indicating that stochastic resonance can be enhanced or degraded depending on the feedback time.
Journal of Optics B: Quantum and Semiclassical Optics, 2002
We study the multimode dynamics of a semiconductor laser with optical feedback operating in the l... more We study the multimode dynamics of a semiconductor laser with optical feedback operating in the low-frequency fluctuation regime. A multimode extension of the Lang-Kobayashi (LK) model shows, in agreement with experimental observations, that the low-frequency power dropouts exhibited by the main modes are accompanied by sudden, asymmetric, activations of dormant longitudinal side modes. Furthermore, these activations are delayed with respect to the dropouts of the active modes. In order to satisfactorily reproduce both the asymmetric activation of side modes and their delay with respect to the dropouts, the generalized LK model has to include a parabolic gain profile, together with a frequency shift of the gain curve with carrier population.
Journal of Optics B: Quantum and Semiclassical Optics, 2002
The dynamics of power distribution between longitudinal modes of a multimode semiconductor laser ... more The dynamics of power distribution between longitudinal modes of a multimode semiconductor laser subjected to external optical feedback is experimentally analysed in the low-frequency fluctuation regime. Power dropouts in the total light intensity are invariably accompanied by sudden activations of several longitudinal modes. These activations are seen not to be simultaneous to the dropouts, but to occur after them. The phenomenon is statistically analysed in a systematic way, and the corresponding delay is estimated.
Fluctuation and Noise Letters, 2003
The control of the low-frequency fluctuations exhibited by two mutually coupled semiconductor las... more The control of the low-frequency fluctuations exhibited by two mutually coupled semiconductor lasers is studied experimentally and numerically. We observe that coupling enhances the response of the system to a weak periodic modulation of the injection current of one of the lasers, leading to a highly efficient entrainment of the synchronized low-frequency power dropouts to the external periodic driving. We compare the quality of the entrainment with the one obtained in a single semiconductor laser with optical feedback, showing the beneficial role of coupling in this pursuit. The experimental observations are satisfactorily reproduced by numerical simulations of a set of coupled delay-differential rate equations.
Europhysics Letters (EPL), 2003
We show both experimentally and numerically a ghost resonance in the sudden power dropouts exhibi... more We show both experimentally and numerically a ghost resonance in the sudden power dropouts exhibited by a semiconductor laser subject to optical feedback driven by two simultaneous weak periodic signals. The small signal modulation conspires with the complex internal dynamics of the system to produce a resonance at a ghost frequency, i.e. a frequency that is not present in the driving signals. This is an eminently nonlinear effect not reported before and agrees with the recent theoretical predictions by Chialvo et al. (Phys. Rev. E, 65 (2002) 050902(R)). The response of dynamical systems to external driving is a far-reaching problem, with implications ranging from signal detection by sensory systems [1] to information encoding through diode laser modulation in communication systems [2]. In the former context, for instance, recent research efforts have been addressed to understand the perception of complex sounds in auditory systems. To that end, the response of excitable threshold devices to multifrequency signals has been theoretically shown to exhibit a resonance at a frequency which is absent in the input driving [3]. The present letter reports an experimental realization of this ghost resonance in a different type of complex dynamical system, namely a semiconductor laser subject to optical feedback. This system has attracted much attention of the researchers for more than three decades. One of its most interesting characteristic regimes is the lowfrequency fluctuation regime (LFF), in which the output power of the laser suffers sudden dropouts to almost zero power at irregular time intervals when biased close to threshold [4]. Although the LFF behavior was already observed at the end of the seventies, its dynamics is not fully understood yet. Recent experimental [5] and numerical [6, 7] reports show the conditions for which a laser subject to optical feedback and biased close to threshold is able to operate in an excitable
Electronics Letters, 2000
A bidirectional lightwave 100 km transmission system capable of delivering 80 cable television (C... more A bidirectional lightwave 100 km transmission system capable of delivering 80 cable television (CATV) analogue video signals using conventional singlemode fibre (SMF) or large effective area fibre (LEAF) has been demonstrated experimentally for the first time. Elimination of both Rayleigh backscattered crosstalk from the opposite-direction signal and amplified spontaneous emission noise is required to improve the system carrier-to-noise ratio. Satisfactory system performance can be achieved regardless of whether an SMF or LEAF 100 km link is used. However, the composite second-order quality of the LEAF link is superior to that of the SMF link. This technology should play an important role in leased fibre links for trunk delivery between any two multiple system operators across another CATV-operator system.
Applied Physics Letters, 2002
We examine the effect of current modulation in the irregular dropout dynamics exhibited by two mu... more We examine the effect of current modulation in the irregular dropout dynamics exhibited by two mutually coupled semiconductor lasers. Our experimental results show that a weak periodic modulation in the injection current of one of the lasers entrains the power dropouts in a very efficient way. It is also observed that the laser with the highest frequency leads the dynamics independently of which laser is modulated. As a result, the entrainment is anticipative when modulation is applied to the laser with lowest frequency. Numerical simulations of a model based on delay-coupled rate equations successfully reproduce the observed behavior.
Frontiers in Human Neuroscience, 2014
Frontiers in Human Neuroscience, 2016
Nature Communications, 2019
A wide variety of social, biological or technological systems can be described as processes takin... more A wide variety of social, biological or technological systems can be described as processes taking place on networked structures in continuous interaction with other networks. We propose here a new methodology to describe, anticipate and manage, in real time, the out-of-equilibrium dynamics of processes that evolve on interconnected networks. This goal is achieved through the full analytical treatment of the phenomenology and its reduction to a two-dimensional flux diagram, allowing us to predict at every time step the dynamical consequences of modifying the links between the different ensembles. Our results are consistent with real data and the methodology can be translated to clustered networks and/or interconnected networks of any size, topology or origin, from the struggle for knowledge on innovation structures to international economic relations or disease spreading on social groups.
Data in Brief, 2019
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Chaos: An Interdisciplinary Journal of Nonlinear Science, 2017
We investigate the existence of an optimal interplay between the natural frequencies of a group c... more We investigate the existence of an optimal interplay between the natural frequencies of a group chaotic oscillators and the topological properties of the network they are embedded in. We identify the conditions for achieving phase synchronization in the most effective way, i.e., with the lowest possible coupling strength. Specifically, we show by means of numerical and experimental results that it is possible to define a synchrony alignment function J(ω, L) linking the natural frequencies ω i of a set of non-identical phase-coherent chaotic oscillators with the topology of the Laplacian matrix L, the latter accounting for the specific organization of the network of interactions between oscillators. We use the classical Rössler system to show that the synchrony alignment function obtained for phase oscillators can be extended to phase-coherent chaotic systems. Finally, we carry out a series of experiments with nonlinear electronic circuits to show the robustness of the theoretical predictions despite the intrinsic noise and parameter mismatch of the electronic components.
Frontiers in Human Neuroscience, 2015
In this study we used graph theory analysis to investigate age-related reorganization of function... more In this study we used graph theory analysis to investigate age-related reorganization of functional networks during the active maintenance of information that is interrupted by external interference. Additionally, we sought to investigate network differences before and after averaging network parameters between both maintenance and interference windows. We compared young and older adults by measuring their magnetoencephalographic recordings during an interference-based working memory task restricted to successful recognitions. Data analysis focused on the topology/temporal evolution of functional networks during both the maintenance and interference windows. We observed that: (a) Older adults require higher synchronization between cortical brain sites in order to achieve a successful recognition, (b) The main differences between age groups arise during the interference window, (c) Older adults show reduced ability to reorganize network topology when interference is introduced, and (d) Averaging network parameters leads to a loss of sensitivity to detect age differences.
Chaos, Solitons & Fractals, 2015
Increased variability in performance has been associated with the emergence of several neurologic... more Increased variability in performance has been associated with the emergence of several neurological and psychiatric pathologies. However, whether and how consistency of neuronal activity may also be indicative of an underlying pathology is still poorly understood. Here we propose a novel method for evaluating consistency from non-invasive brain recordings. We evaluate the consistency of the cortical activity recorded with magnetoencephalography in a group of subjects diagnosed with Mild Cognitive Impairment (MCI), a condition sometimes prodromal of dementia, during the execution of a memory task. We use metrics coming from nonlinear dynamics to evaluate the consistency of cortical regions. A representation known as parenclitic networks is constructed, where atypical features are endowed with a network structure, the topological properties of which can be studied at various scales. Pathological conditions correspond to strongly heterogeneous networks, whereas typical or normative conditions are characterized by sparsely connected networks with homogeneous nodes. The analysis of this kind of networks allows identifying the extent to which consistency is affected in the MCI group and the focal points where MCI is especially severe. To the best of our knowledge, these results represent the first attempt at evaluating the consistency of brain functional activity using complex networks theory.