scholarly journals Lost in time: rethinking duration estimation outside the brain.

2021 ◽  
Author(s):  
david robbe

Our perception of the passage of time can suffer from significant distortions as time flies when we are busy and drags when we are bored. A prominent mechanistic model proposes that this perceptual volatility reflects changes in the activity dynamics of distributed neuronal ensembles referred to as population clocks because they encode time. In this framework, time is understood similarly to space (both can be segmented in seconds or centimeters) and duration estimation is primarily internal (the brain tells time). Here, I challenge this framework from the angle of Bergson’s proposal that the inner experience of time is unlike space because it is ever-changing and indivisible (2 successive seconds are not experienced equivalently). Quantifying and communicating this inner experience requires its externalization and immobilization through distance measurements derived from stereotyped movements and spatial metaphors (“short/long” durations; time “flies/drags”), which explains the habit of thinking time like space. In support of Bergson’s proposal, humans and animals heavily rely on movements in a variety of duration estimation tasks and the neural underpinnings of duration estimates overlap those of motor control and spatial navigation. Thus, philosophical and empirical arguments question whether duration estimation is fundamentally internal. Rather than being explained by ad hoc changes in the speed of population clocks, the puzzle of the volatility of time perception might resolve itself by considering that living beings lack the ability to internally measure time, which they compensate through interactions with regularities afforded by the world and symbolic representation drawn from space.

Molecules ◽  
2020 ◽  
Vol 25 (9) ◽  
pp. 2104 ◽  
Author(s):  
Eleonora Ficiarà ◽  
Shoeb Anwar Ansari ◽  
Monica Argenziano ◽  
Luigi Cangemi ◽  
Chiara Monge ◽  
...  

Magnetic Oxygen-Loaded Nanobubbles (MOLNBs), manufactured by adding Superparamagnetic Iron Oxide Nanoparticles (SPIONs) on the surface of polymeric nanobubbles, are investigated as theranostic carriers for delivering oxygen and chemotherapy to brain tumors. Physicochemical and cyto-toxicological properties and in vitro internalization by human brain microvascular endothelial cells as well as the motion of MOLNBs in a static magnetic field were investigated. MOLNBs are safe oxygen-loaded vectors able to overcome the brain membranes and drivable through the Central Nervous System (CNS) to deliver their cargoes to specific sites of interest. In addition, MOLNBs are monitorable either via Magnetic Resonance Imaging (MRI) or Ultrasound (US) sonography. MOLNBs can find application in targeting brain tumors since they can enhance conventional radiotherapy and deliver chemotherapy being driven by ad hoc tailored magnetic fields under MRI and/or US monitoring.


2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Florian Bitsch ◽  
Philipp Berger ◽  
Andreas Fink ◽  
Arne Nagels ◽  
Benjamin Straube ◽  
...  

AbstractThe ability to generate humor gives rise to positive emotions and thus facilitate the successful resolution of adversity. Although there is consensus that inhibitory processes might be related to broaden the way of thinking, the neural underpinnings of these mechanisms are largely unknown. Here, we use functional Magnetic Resonance Imaging, a humorous alternative uses task and a stroop task, to investigate the brain mechanisms underlying the emergence of humorous ideas in 24 subjects. Neuroimaging results indicate that greater cognitive control abilities are associated with increased activation in the amygdala, the hippocampus and the superior and medial frontal gyrus during the generation of humorous ideas. Examining the neural mechanisms more closely shows that the hypoactivation of frontal brain regions is associated with an hyperactivation in the amygdala and vice versa. This antagonistic connectivity is concurrently linked with an increased number of humorous ideas and enhanced amygdala responses during the task. Our data therefore suggests that a neural antagonism previously related to the emergence and regulation of negative affective responses, is linked with the generation of emotionally positive ideas and may represent an important neural pathway supporting mental health.


2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Bob Jacobs ◽  
Heather Rally ◽  
Catherine Doyle ◽  
Lester O’Brien ◽  
Mackenzie Tennison ◽  
...  

Abstract The present review assesses the potential neural impact of impoverished, captive environments on large-brained mammals, with a focus on elephants and cetaceans. These species share several characteristics, including being large, wide-ranging, long-lived, cognitively sophisticated, highly social, and large-brained mammals. Although the impact of the captive environment on physical and behavioral health has been well-documented, relatively little attention has been paid to the brain itself. Here, we explore the potential neural consequences of living in captive environments, with a focus on three levels: (1) The effects of environmental impoverishment/enrichment on the brain, emphasizing the negative neural consequences of the captive/impoverished environment; (2) the neural consequences of stress on the brain, with an emphasis on corticolimbic structures; and (3) the neural underpinnings of stereotypies, often observed in captive animals, underscoring dysregulation of the basal ganglia and associated circuitry. To this end, we provide a substantive hypothesis about the negative impact of captivity on the brains of large mammals (e.g., cetaceans and elephants) and how these neural consequences are related to documented evidence for compromised physical and psychological well-being.


2010 ◽  
Author(s):  
Αικατερίνη Χαραλαμποπούλου

In this study I have attempted to present a linguistic investigation into the nature and structure of time, based on proposals developed in Evans (2004). Accordingly, as linguistic structure and particularly patterns of elaboration reflect conceptual structure conventionalized into a format encodable in language, this study presents an examination of the human conceptual system for time. Indeed, an examination of the ways in which language lexicalizes time provides important insights into the nature and organization of time. That is, given the widely held assumption that semantic structure derives from and reflects, at least partially, conceptual structure, language offers a direct way of investigating the human conceptual system. However, how time is realized at the conceptual level, that is, how we represent time as revealed by the way temporal concepts are encoded in language, does not tell the whole story, if we are to uncover the nature and structure of time. Research in cognitive science suggests that phenomenological experience and the nature of the external world of sensory experience to which subjective experience constitutes a response, give rise to our pre- conceptual experience of time. In other words, as Evans (2004) says, time is not restricted to one particular layer of experience but it rather “constitutes a complex range of phenomena and processes which relate to different levels and kinds of experience” (ibid.: 5). Accordingly, while my focus in this study is on the temporal structure, which is to say the organization and structuring of temporal concepts, at the conceptual level, I have also attempted to present an examination of the nature of temporal experience at the pre-conceptual level (prior to representation in conceptual structure). In this regard, I have examined the results of research from neuroscience, cognitive psychology and social psychology. More specifically and with respect to evidence from neuroscience, it is suggested that temporal experience is ultimately grounded in neurological mechanisms necessary for regulating and facilitating perception (e.g., Pöppel 1994). That is, perceptual processing is underpinned by the occurrence of neurologically instantiated temporal intervals, the perceptual moments, which facilitate the integration of sensory information into coherent percepts. As we have seen, there is no single place in the brain where perceptual input derived from different modalities, or even information from within the same modality, can be integrated. In other words, there is no one place where spatially distributed sensory information associated with the distinct perceptual processing areas of the brain, are integrated in order to produce a coherent percept. Rather, what seems to be the case is that the integration of sensory information into coherent percepts is enabled by the phenomena of periodic perceptual moments. Such a mechanism enables us to perceive, in that the nature of our percepts are in an important sense ‘constructed’. Put another way, perception is a kind of constructive process which updates successive perceptual information to which an organism has access. The updating occurs by virtue of innate timing mechanisms, the perceptual moments, which occur at all levels of neurological processing and range from a fraction of second up to an outer limit of about three seconds. It is these timing mechanisms which form the basis of our temporal experience. As Gell says, “perception is intrinsically time-perception, and conversely, time-perception, or internal time-consciousness, is just perception itself...That is to say, time is not something we encounter as a feature of contingent reality, as if it lay outside us, waiting to be perceived along with tables and chairs and the rest of the perceptible contents of the universe. Instead, subjective time arises as inescapable feature of the perceptual process itself, which enters into the perception of anything whatsoever” (1992: 231). In other words, our experience of time is a consequence of the various innate ‘timing mechanisms' in the brain which give rise to a range of perceptual moments, which are in turn necessary for and underpin perceptual processing. In this way, time exists into the experience of everything as it is fundamental to the way in which perceptual process operates. […]


2003 ◽  
Vol 358 (1435) ◽  
pp. 1231-1240 ◽  
Author(s):  
Vittorio Gallese

Abstraction denotes the cognitive process by means of which general concepts are formed. The dominant view of abstraction considers it not only as a complex and sophisticated cognitive activity, but also as a distinctive hallmark of mankind. The distinctiveness of abstract thought has indeed been closely related to another feature peculiar to our species: language. Following this perspective, the possibility to entertain conceptual representations is thus precluded to animals devoid of full–blown language. I challenge this view and propose that the representational dynamic of the brain is conceivable as a type of self–organization, in which action plays a crucial part. My aim will be to investigate whether, and to what extent, conceptual knowledge can be attributed to non–linguistic animal species, with particular emphasis on nonhuman primates. I therefore introduce the notion of semantic content as a type of ‘relational specification’. A review of recent neurophysiological data on the neural underpinnings of action end–states in the macaque monkey brain is presented. On the basis of this evidence, I propose that conceptual representations can be conceived as the expression of a coherent internal world model. This model decomposes the ‘outer’ space inhabited by things in a meaningful way only to the extent that it accords to biologically constrained, embodied invariance. Finally, I discuss how the ‘comparative’ neuroscientific approach to abstraction proposed here may shed some light on its nature and its evolutionary origin.


2021 ◽  
Author(s):  
Carlo Cristiano ◽  
◽  
Marco Pirrone ◽  

Risk-mitigation strategies are most effective when the major sources of uncertainty are determined through dedicated and in-depth studies. In the context of reservoir characterization and modeling, petrophysical uncertainty plays a significant role in the risk assessment phase, for instance in the computation of volumetrics. The conventional workflow for the propagation of the petrophysical uncertainty consists of physics-based model embedded into a Monte Carlo (MC) template. In detail, open-hole logs and their inherent uncertainties are used to estimate the important petrophysical properties (e.g. shale volume, porosity, water saturation) with uncertainty through the mechanistic model and MC simulations. In turn, model parameter uncertainties can be also considered. This standard approach can be highly time-consuming in case the physics-based model is complex, unknown, difficult to reproduce (e.g. old/legacy wells) and/or the number of wells to be processed is very high. In this respect, the aim of this paper is to show how a data-driven methodology can be used to propagate the petrophysical uncertainty in a fast and efficient way, speeding-up the complete process but still remaining consistent with the main outcomes. In detail, a fit-for-purpose Random Forest (RF) algorithm learns through experience how log measurements are related to the important petrophysical parameters. Then, a MC framework is used to infer the petrophysical uncertainty starting from the uncertainty of the input logs, still with the RF model as a driver. The complete methodology, first validated with ad-hoc synthetic case studies, has been then applied to two real cases, where the petrophysical uncertainty has been required for reservoir modeling purposes. The first one includes legacy wells intercepting a very complex lithological environment. The second case comprises a sandstone reservoir with a very high number of wells, instead. For both scenarios, the standard approach would have taken too long (several months) to be completed, with no possibility to integrate the results into the reservoir models in time. Hence, for each well the RF regressor has been trained and tested on the whole dataset available, obtaining a valid data-driven analytics model for formation evaluation. Next, 1000 scenarios of input logs have been generated via MC simulations using multivariate normal distributions. Finally, the RF regressor predicts the associated 1000 petrophysical characterization scenarios. As final outcomes of the workflow, ad-hoc statistics (e.g. P10, P50, P90 quantiles) have been used to wrap up the main findings. The complete data-driven approach took few days for both scenarios with a critical impact on the subsequent reservoir modeling activities. This study opens the possibility to quickly process a high number of wells and, in particular, it can be also used to effectively propagate the petrophysical uncertainty to legacy well data for which conventional approaches are not an option, in terms of time-efficiency.


Author(s):  
Jiangling Song ◽  
Jennifer A. Kim ◽  
Aaron Frank Struck ◽  
Rui Zhang ◽  
M. Brandon Westover

Secondary brain injury (SBI) is defined as new or worsening injury to the brain after an initial neurologic insult, such as hemorrhage, trauma, ischemic stroke, or infection. It is a common and potentially preventable complication following many types of primary brain injury (PBI). However, mechanistic details about how PBI leads to additional brain injury and evolves into SBI are poorly characterized. In this work, we propose a mechanistic model for the metabolic supply demand mismatch hypothesis (MSDMH) of SBI. Our model, based on the Hodgkin-Huxley model, supplemented with additional dynamics for extracellular potassium, oxygen concentration and excitotoxity, provides a high-level unified explanation for why patients with acute brain injury frequently develop SBI. We investigate how decreased oxygen, increased extracellular potassium, excitotoxicity, and seizures can induce SBI, and suggest three underlying paths for how events following PBI may lead to SBI. The proposed model also helps explain several important empirical observations, including the common association of acute brain injury with seizures, the association of seizures with tissue hypoxia and so on. In contrast to current practices which assume that ischemia plays the predominant role in SBI, our model suggests that metabolic crisis involved in SBI can also be non-ischemic. Our findings offer a more comprehensive understanding of the complex interrelationship among potassium, oxygen, excitotoxicity, seizures and SBI.


2018 ◽  
Vol 41 (1) ◽  
pp. 389-413 ◽  
Author(s):  
Sheena A. Josselyn ◽  
Paul W. Frankland

Memories for events are thought to be represented in sparse, distributed neuronal ensembles (or engrams). In this article, we review how neurons are chosen to become part of a particular engram, via a process of neuronal allocation. Experiments in rodents indicate that eligible neurons compete for allocation to a given engram, with more excitable neurons winning this competition. Moreover, fluctuations in neuronal excitability determine how engrams interact, promoting either memory integration (via coallocation to overlapping engrams) or separation (via disallocation to nonoverlapping engrams). In parallel with rodent studies, recent findings in humans verify the importance of this memory integration process for linking memories that occur close in time or share related content. A deeper understanding of allocation promises to provide insights into the logic underlying how knowledge is normally organized in the brain and the disorders in which this process has gone awry.


2009 ◽  
Vol 364 (1525) ◽  
pp. 1809-1813 ◽  
Author(s):  
Marc Wittmann ◽  
Virginie van Wassenhove

Time research has been a neglected topic in the cognitive neurosciences of the last decades: how do humans perceive time? How and where in the brain is time processed? This introductory paper provides an overview of the empirical and theoretical papers on the psychological and neural basis of time perception collected in this theme issue. Contributors from the fields of cognitive psychology, psychiatry, neurology and neuroanatomy tackle this complex question with a variety of techniques ranging from psychophysical and behavioural experiments to pharmacological interventions and functional neuroimaging. Several (and some new) models of how and where in the brain time is processed are presented in this unique collection of recent research that covers experienced time intervals from milliseconds to minutes. We hope this volume to be conducive in developing a better understanding of the sense of time as part of complex set of brain–body factors that include cognitive, emotional and body states.


2019 ◽  
Vol 111 (3) ◽  
pp. 419-432
Author(s):  
Annelli Janssen

Abstract The web-model: A new model of explanation for neuroimaging studiesWhat can neuroimaging tell us about the relation between our brain and our mind? A lot, or so I argue. But neuroscientists should update their model of explanation. Currently, many explanations are (implicitly) based on what I call the ‘mapping model’: a model of explanation which centers on mapping relations between cognition and the brain. I argue that these mappings give us very little information, and that instead, we should focus on finding causal relations. If we take a difference-making approach to causation, we can find manipulation patterns between neural and cognitive phenomena and start constructing satisfying explanations in neuroimaging studies: explanations based on what I call the web-model of explanation. This model of explanation not only contrasts with the mapping model, but is also different from Craver’s constitutive mechanistic model of explanation (2007), which takes the constitutive relation to be the main explanatory relation. Taking the difference-making idea of the importance of manipulation and control seriously, means that sometimes, causal relations are preferred over constitutive relations. If we follow the web-model of explanation, we can do justice to the central role that causation should play in neuroscientific explanations.


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