Space and Time in the Brain

2019 ◽  
pp. 241-278
Author(s):  
György Buzsáki
Keyword(s):  
Special Problem ◽  
Measuring Instruments ◽  
Classical Physics ◽  
Cell Assemblies ◽  
Space And Time ◽  
Episodic Memories ◽  
The Brain

The science of space and time began with the invention of measuring instruments, which changed these dimensionless concepts into distance and duration with precise units. This process created a special problem for neuroscience. If space and time correspond to their measured variants, we may wonder what space and time mean without such instruments, including for non-human animals who cannot read those instruments. Nonetheless, contemporary neuroscience still lives within the framework of the classical physics view. Our episodic memories are defined as “what happened to me, where, and when.” This is a typical outside-in approach: assume the concepts and search for their homes in the brain. Yet I argue in this chapter that almost everything that we attribute to space and time in the brain can be accomplished by sequential cell assemblies or neuronal trajectories.

scholarly journals Harmonic Brain Modes: A Unifying Framework for Linking Space and Time in Brain Dynamics

2017 ◽  
Vol 24 (3) ◽  
pp. 277-293 ◽  
Author(s):  
Selen Atasoy ◽  
Gustavo Deco ◽  
Morten L. Kringelbach ◽  
Joel Pearson
Keyword(s):  
Neural Activity ◽  
Brain Activity ◽  
Activity Patterns ◽  
Structural Connectivity ◽  
Building Blocks ◽  
Mental States ◽  
Brain Dynamics ◽  
Space And Time ◽  
Wide Range ◽  
The Brain

A fundamental characteristic of spontaneous brain activity is coherent oscillations covering a wide range of frequencies. Interestingly, these temporal oscillations are highly correlated among spatially distributed cortical areas forming structured correlation patterns known as the resting state networks, although the brain is never truly at “rest.” Here, we introduce the concept of harmonic brain modes—fundamental building blocks of complex spatiotemporal patterns of neural activity. We define these elementary harmonic brain modes as harmonic modes of structural connectivity; that is, connectome harmonics, yielding fully synchronous neural activity patterns with different frequency oscillations emerging on and constrained by the particular structure of the brain. Hence, this particular definition implicitly links the hitherto poorly understood dimensions of space and time in brain dynamics and its underlying anatomy. Further we show how harmonic brain modes can explain the relationship between neurophysiological, temporal, and network-level changes in the brain across different mental states ( wakefulness, sleep, anesthesia, psychedelic). Notably, when decoded as activation of connectome harmonics, spatial and temporal characteristics of neural activity naturally emerge from the interplay between excitation and inhibition and this critical relation fits the spatial, temporal, and neurophysiological changes associated with different mental states. Thus, the introduced framework of harmonic brain modes not only establishes a relation between the spatial structure of correlation patterns and temporal oscillations (linking space and time in brain dynamics), but also enables a new dimension of tools for understanding fundamental principles underlying brain dynamics in different states of consciousness.

scholarly journals Space and time in the brain

Science ◽  
2017 ◽  
Vol 358 (6362) ◽  
pp. 482-485 ◽  
Author(s):  
György Buzsáki ◽  
Rodolfo Llinás
Keyword(s):  
Space And Time ◽  
The Brain

scholarly journals Space and time in the brain

IBRO Reports ◽  
2019 ◽  
Vol 7 ◽  
pp. 52
Author(s):  
Edvard Moser
Keyword(s):  
Space And Time ◽  
The Brain

Re-assembling the brain: Are cell assemblies the brain's language for recovery of function?

1999 ◽  
Vol 22 (2) ◽  
pp. 284-284 ◽  
Author(s):  
Chris Code
Keyword(s):  
Cognitive Functions ◽  
Recovery Of Function ◽  
Cell Assembly ◽  
Connectionist Models ◽  
Cell Assemblies ◽  
The Brain

Holistically ignited Hebbian models are fundamentally different from the serially organized connectionist implementations of language. This may be important for the recovery of language after injury, because connectionist models have provided useful insights into recovery of some cognitive functions. I ask whether cell assembly modelling can make an important contribution and whether the apparent incompatibility with successful connectionist modelling is a problem.

Gravity in the Brain as a Reference for Space and Time Perception

2015 ◽  
Vol 28 (5-6) ◽  
pp. 397-426 ◽  
Author(s):  
Francesco Lacquaniti ◽  
Gianfranco Bosco ◽  
Silvio Gravano ◽  
Iole Indovina ◽  
Barbara La Scaleia ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Relative Weight ◽  
Visual Images ◽  
Gravitational Acceleration ◽  
Time Stamp ◽  
Space And Time ◽  
Visual Vertical ◽  
Ancient Times ◽  
Behavioral Evidence ◽  
The Brain

Moving and interacting with the environment require a reference for orientation and a scale for calibration in space and time. There is a wide variety of environmental clues and calibrated frames at different locales, but the reference of gravity is ubiquitous on Earth. The pull of gravity on static objects provides a plummet which, together with the horizontal plane, defines a three-dimensional Cartesian frame for visual images. On the other hand, the gravitational acceleration of falling objects can provide a time-stamp on events, because the motion duration of an object accelerated by gravity over a given path is fixed. Indeed, since ancient times, man has been using plumb bobs for spatial surveying, and water clocks or pendulum clocks for time keeping. Here we review behavioral evidence in favor of the hypothesis that the brain is endowed with mechanisms that exploit the presence of gravity to estimate the spatial orientation and the passage of time. Several visual and non-visual (vestibular, haptic, visceral) cues are merged to estimate the orientation of the visual vertical. However, the relative weight of each cue is not fixed, but depends on the specific task. Next, we show that an internal model of the effects of gravity is combined with multisensory signals to time the interception of falling objects, to time the passage through spatial landmarks during virtual navigation, to assess the duration of a gravitational motion, and to judge the naturalness of periodic motion under gravity.

scholarly journals Predictability changes what we remember in familiar temporal contexts

2018 ◽  
Author(s):  
Hyojeong Kim ◽  
Margaret L. Schlichting ◽  
Alison R. Preston ◽  
Jarrod A. Lewis-Peacock
Keyword(s):  
Human Brain ◽  
Pattern Classification ◽  
Prediction Error ◽  
Fmri Data ◽  
The Past ◽  
The Future ◽  
Abstract Level ◽  
Episodic Memories ◽  
The Brain

AbstractThe human brain constantly anticipates the future based on memories of the past. Encountering a familiar situation reactivates memory of previous encounters which can trigger a prediction of what comes next to facilitate responsiveness. However, a prediction error can lead to pruning of the offending memory, a process that weakens its representation in the brain and leads to forgetting. Our goal in this study was to evaluate whether memories are spared from pruning in situations that allow for more abstract yet reliable predictions. We hypothesized that when the category, but not the identity, of a new stimulus can be anticipated, this will reduce pruning of existing memories and also reduce encoding of the specifics of new memories. Participants viewed a sequence of objects, some of which reappeared multiple times (“cues”), followed always by novel items. Half of the cues were followed by new items from different (unpredictable) categories, while others were followed by new items from a single (predictable) category. Pattern classification of fMRI data was used to identify category-specific predictions after each cue. Pruning was observed only in unpredictable contexts, while encoding of new items suffered more in predictable contexts. These findings demonstrate that how episodic memories are updated is influenced by the reliability of abstract-level predictions in familiar contexts.

scholarly journals Forgetting Enhances Episodic Control with Structured Memories

2021 ◽  
Author(s):  
Annik Yalnizyan-Carson ◽  
Blake A Richards
Keyword(s):  
Decision Making ◽  
Reinforcement Learning ◽  
Structural Information ◽  
Mammalian Brain ◽  
Capacity Limitations ◽  
Memory Cache ◽  
Learning Agent ◽  
Episodic Memories ◽  
The Brain ◽  
Over Time

Forgetting is a normal process in healthy brains, and evidence suggests that the mammalian brain forgets more than is required based on limitations of mnemonic capacity. Episodic memories, in particular, are liable to be forgotten over time. Researchers have hypothesized that it may be beneficial for decision making to forget episodic memories over time. Reinforcement learning offers a normative framework in which to test such hypotheses. Here, we show that a reinforcement learning agent that uses an episodic memory cache to find rewards in maze environments can forget a large percentage of older memories without any performance impairments, if they utilize mnemonic representations that contain structural information about space. Moreover, we show that some forgetting can actually provide a benefit in performance compared to agents with unbounded memories. Our analyses of the agents show that forgetting reduces the influence of outdated information and states which are not frequently visited on the policies produced by the episodic control system. These results support the hypothesis that some degree of forgetting can be beneficial for decision making, which can help to explain why the brain forgets more than is required by capacity limitations.

scholarly journals Nitric oxide: linking space and time in the brain.

1992 ◽  
Vol 89 (24) ◽  
pp. 11651-11652 ◽  
Author(s):  
G. M. Edelman ◽  
J. A. Gally
Keyword(s):  
Nitric Oxide ◽  
Space And Time ◽  
The Brain

Internally Organized Activity During Offline Brain States

2019 ◽  
pp. 199-218
Author(s):  
György Buzsáki
Keyword(s):  
Trial And Error ◽  
The Past ◽  
Sharp Wave ◽  
Assembly Sequences ◽  
Brain States ◽  
Episodic Memories ◽  
Neuronal Assembly ◽  
Vicarious Trial And Error ◽  
The Brain ◽  
Future Plans

A prime example of internally organized patterns is observed during sleep. The best studied of these is the sharp wave ripple in the hippocampus. Neuronal sequences during ripple events reach back to the past to replay snippets of waking experience at times when the brain is disengaged from the outside world. This process may consolidate episodic memories and stitch together discontiguous experiences, thereby giving rise to creative thoughts. In addition, neuronal assembly sequences during ripples also act as internalized, vicarious, trial-and-error mechanisms that can assist with subconscious optimization of future plans. Because the same neuronal substrate can perform both retrospective and prospective operations, it is not clear whether the traditional separation of postdiction (i.e., memory) from prediction (i.e., planning) is justified.

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