scholarly journals A large majority of awake hippocampal sharp-wave ripples feature spatial trajectories with momentum

Neuron ◽  
2021 ◽  
Author(s):  
Emma L. Krause ◽  
Jan Drugowitsch
2018 ◽  
Author(s):  
Alyssa A. Carey ◽  
Youki Tanaka ◽  
Matthijs A. A. van der Meer

AbstractThe rodent hippocampus spontaneously generates bursts of neural activity (“replay”) which can depict spatial trajectories to reward locations, suggesting a role in model-based behavioral control. A largely separate literature emphasizes reward revaluation as the litmus test for such control, yet the content of hippocampal replay under revaluation conditions is unknown. We report that the content of awake hippocampal sharp wave-ripple events is biased away from the preferred outcome following reward revaluation, challenging the idea that such sequences reflect recent experience or trajectories toward the preferred goal.


2021 ◽  
Author(s):  
Emma L Krause ◽  
Jan Drugowitsch

During periods of rest, hippocampal place cells feature bursts of activity called sharp-wave ripples (SWRs). Heuristic approaches to their analysis have revealed that a small fraction of SWRs appear to "simulate" trajectories through the environment - called awake hippocampal replay - while the functional role of a majority of these SWRs remains unclear. Applying a novel probabilistic approach to characterize the spatio-temporal dynamics embedded in SWRs, we instead show that almost all SWRs of foraging rodents simulate such trajectories through the environment. Furthermore, these trajectories feature momentum, that is, inertia in their velocities, that mirrors the animals' natural movement. This stands in contrast to replay events during sleep which seem to follow Brownian motion without such momentum. Lastly, interpreting the replay trajectories in the context of navigational planning revealed that similar past analyses were biased by the heuristic SWR sub-selection. Overall, our approach provides a more complete characterization of the spatio-temporal dynamics within SWRs, highlights qualitative differences between sleep and awake replay, and ought to support future, more detailed, and less biased analysis of the role of awake replay in navigational planning.


2014 ◽  
Vol 73 (3) ◽  
pp. 250-259
Author(s):  
Etienne Verhoeyen

Met dit boek levert Frank Seberechts een nagenoeg volledige studie af van een van de minder fraai kanten van de Belgische samenleving in 1940: de administratieve arrestatie en de wegvoering naar Frankrijk van enkele duizenden personen (de ‘verdachten’), Belgen of in België verblijvende vreemdelingen. De extreem-rechtse en pro-Duitse arrestanten hebben na hun vrijlating dit feit politiek in hun voordeel uitgebaat, waardoor volledig in de schaduw kwam te staan dat de overgrote meerderheid van de weggevoerden joodse mensen waren die in de jaren voor de oorlog naar België waren gevlucht. Dat het beeld van de wegvoeringen niet volledig is, is grotendeels te wijten aan het feit dat de meeste archieven die hierop betrekking hebben tijdens de meidagen van 1940 vernietigd werden. Met name de politieke besluitvorming over de wegvoeringen vertoont nog steeds schemerzones, zodat het vastleggen van verantwoordelijkheden ook vandaag nog een gewaagde onderneming is.________Deportations and the deported during the Maydays in 1940 By means of this book Frank Seberechts provides an almost complete study of one of the less admirable sides of Belgian society in 1940: the administrative arrest and the deportation to France of some thousands of people (‘the suspects’), Belgians or foreigners residing in Belgium. The extreme-right and pro-German detainees politically exploited this fact after they had been freed, but this completely overshadowed the point that the large majority of the deported people were Jews who had fled to Belgium during the years preceding the war. This incomplete portrayal of the deportations is mainly due to the fact that most of the archives relating to the events had been destroyed during the Maydays of 1940. The history of the political decision-making about the deportations in particular still shows many grey areas and it is therefore still a risky business even today to determine which people should be held accountable.


Author(s):  
J.S. Grewal

On Lord Wavell’s initiative, the Simla Conference was held to discuss the proposal of a new executive council and a new constitution for India after the war. Master Tara Singh represented the Sikh community at the Simla Conference. The Conference failed due to Jinnah’s insistence that the Muslim League alone had the right to nominate Muslim representatives on the Executive Council. The failure of the Conference made the general elections of 1945–6 all the more important. The general elections resulted in a large degree of polarization between the Hindus, Muslims, and Sikhs. The Muslim League got Muslim mandate in favour of Pakistan. The Congress got a mandate of Hindus and a considerable proportion of the Sikhs for independence without partition. The Akalis got support of the large majority of the Sikhs for an independent political entity of the Sikhs. This polarization was of crucial importance for the future.


Author(s):  
Benjamin Mako Hill ◽  
Aaron Shaw

While the large majority of published research on online communities consists of analyses conducted entirely within individual communities, this chapter argues for a population-based approach, in which researchers study groups of similar communities. For example, although there have been thousands of papers published about Wikipedia, a population-based approach might compare all wikis on a particular topic. Using examples from published empirical studies, the chapter describes five key benefits of this approach. First, it argues that population-level research increases the generalizability of findings. Next, it describes four processes and dynamics that are only possible to study using populations: community-level variables, information diffusion processes across communities, ecological dynamics, and multilevel community processes. The chapter concludes with a discussion of a series of limitations and challenges.


English Today ◽  
2021 ◽  
pp. 1-16
Author(s):  
Manfred Markus

Given today's general bias towards euphemisms (cf. Arif, 2015), the topic of this paper may seem embarrassing and ill-chosen. However, it makes sense to find out to what extent the spoken language of dialects in former centuries correlated with one of the dark sides of everyday reality. In Britain up to the second half of the 19th century, traditional dialect was the common linguistic medium of the large majority of people (the lower and middle classes), just before the norm of ‘King's English’ and, in linguistics, of système, started playing a dominant role. We may assume that the English dialects of the Late Modern English (LModE) period (1700–1900) were a correlative of people's everyday life.


2021 ◽  
Vol 11 (10) ◽  
pp. 4330
Author(s):  
Andrea Lucchese ◽  
Salvatore Digiesi ◽  
Kübra Akbaş ◽  
Carlotta Mummolo

The ability of an agent to accomplish a trajectory during a certain motor task depends on the fit between external (environment) and internal (agent) constraints, also known as affordance. A model of difficulty for a generalized reaching motor task is proposed as an affordance-related measure, as perceived by a specific agent for a given environment and task. By extending the information-based Index of Difficulty of a trajectory, a stochastic model of difficulty is formulated based on the observed variability of spatial trajectories executed by a given agent during a repetitive motor task. The model is tested on an experimental walking dataset available in the literature, where the repetitive stride movement of differently aged subjects (14 “old” subjects aged 50–73; 20 “young” subjects aged 21–37) at multiple speed conditions (comfortable, ~30% faster, ~30% slower) is analyzed. Reduced trajectory variability in older as compared to younger adults results in a higher Index of Difficulty (slower: +24%, p < 0.0125; faster: +38%, p < 0.002) which is interpreted in this context as reduced affordance. The model overcomes the limits of existing difficulty measures by capturing the stochastic dependency of task difficulty on a subject’s age and average speed. This model provides a benchmarking tool for motor performance in biomechanics and ergonomics applications.


Neuron ◽  
2016 ◽  
Vol 92 (5) ◽  
pp. 968-974 ◽  
Author(s):  
Gido M. van de Ven ◽  
Stéphanie Trouche ◽  
Colin G. McNamara ◽  
Kevin Allen ◽  
David Dupret
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