scholarly journals Reading positional codes with fMRI: Problems and solutions

2016 ◽  
Author(s):  
Kristjan Kalm ◽  
Dennis Norris
Keyword(s):  
Memory Load ◽  
Large Body ◽  
Neural Mechanisms ◽  
Neural Representation ◽  
Sensory Adaptation ◽  
Neural Data ◽  
Problems And Solutions ◽  
Consistent Manner ◽  
Human Experiments ◽  
Human Neuroimaging

Neural mechanisms which bind items into sequences have been investigated in a large body of research in animal neurophysiology and human neuroimaging. However, a major problem in interpreting this data arises from a fact that several unrelated processes, such as memory load, sensory adaptation, and reward expectation, also change in a consistent manner as the sequence unfolds. In this paper we show that the problem of extracting neural data about the structure of a sequence is especially acute for fMRI, which is almost exclusively the modality used in human experiments. We show that such fMRI results must be treated with caution and in many cases the assumed neural representation might actually reflect unrelated processes.

scholarly journals Mice are not automatons; subjective experience in premotor circuits guides behavior

2021 ◽  
Author(s):  
Drew C. Schreiner ◽  
Christian Cazares ◽  
Rafael Renteria ◽  
Christina M Gremel
Keyword(s):  
Decision Making ◽  
Motor Cortex ◽  
Adaptive Behavior ◽  
Subjective Experience ◽  
Contextual Factors ◽  
Neural Mechanisms ◽  
Neural Representation ◽  
Recent Experience ◽  
Checking Behavior ◽  
Corticostriatal Circuits

Subjective experience is a powerful driver of decision-making and continuously accrues. However, most neurobiological studies constrain analyses to task-related variables and ignore how continuously and individually experienced internal, temporal, and contextual factors influence adaptive behavior during decision-making and the associated neural mechanisms. We show mice rely on learned information about recent and longer-term subjective experience of variables above and beyond prior actions and reward, including checking behavior and the passage of time, to guide self-initiated, self-paced, and self-generated actions. These experiential variables were represented in secondary motor cortex (M2) activity and its projections into dorsal medial striatum (DMS). M2 integrated this information to bias strategy-level decision-making, and DMS projections used specific aspects of this recent experience to plan upcoming actions. This suggests diverse aspects of experience drive decision-making and its neural representation, and shows premotor corticostriatal circuits are crucial for using selective aspects of experiential information to guide adaptive behavior.

Perception and Imagery

Brain-Mind ◽  
2019 ◽  
pp. 50-71
Author(s):  
Paul Thagard
Keyword(s):  
Neural Mechanisms ◽  
Neural Representation ◽  
Sensory Inputs ◽  
General Account ◽  
Binding Competition ◽  
Mental Operations

This chapter provides a general account of imagery that applies to both external senses such as vision and internal senses such as pain. It identifies five mental operations that occur in all kinds of imagery: intensification, focusing, combination, juxtaposition, and decomposition. Each of these operations results from neural mechanisms that are part of the Semantic Pointer Architecture, including storage, retrieval, neural representation, binding, competition, and transformation. There is abundant psychological and neural evidence that imagery is real and that the brain’s computations employ special patterns of neural representation that develop from sensory inputs. This development requires binding into semantic pointers that are susceptible to symbol-like manipulation that exploits the different sensory characters of visual, auditory, and other sorts of representation.

scholarly journals On the methods for reactivation and replay analysis

2020 ◽  
Vol 375 (1799) ◽  
pp. 20190231 ◽  
Author(s):  
David Tingley ◽  
Adrien Peyrache
Keyword(s):  
Neural Activity ◽  
Temporal Structure ◽  
Activity Patterns ◽  
Large Body ◽  
Neural Data ◽  
History Of ◽  
Methodological Approaches ◽  
Neuronal Patterns ◽  
External Stimuli ◽  
The Brain

A major task in the history of neurophysiology has been to relate patterns of neural activity to ongoing external stimuli. More recently, this approach has branched out to relating current neural activity patterns to external stimuli or experiences that occurred in the past or future. Here, we aim to review the large body of methodological approaches used towards this goal, and to assess the assumptions each makes with reference to the statistics of neural data that are commonly observed. These methods primarily fall into two categories, those that quantify zero-lag relationships without examining temporal evolution, termed reactivation , and those that quantify the temporal structure of changing activity patterns, termed replay . However, no two studies use the exact same approach, which prevents an unbiased comparison between findings. These observations should instead be validated by multiple and, if possible, previously established tests. This will help the community to speak a common language and will eventually provide tools to study, more generally, the organization of neuronal patterns in the brain. This article is part of the Theo Murphy meeting issue ‘Memory reactivation: replaying events past, present and future’.

scholarly journals Neural signatures of vigilance decrements predict behavioural errors before they occur

2020 ◽  
Author(s):  
Hamid Karimi-Rouzbahani ◽  
Alexandra Woolgar ◽  
Anina N. Rich
Keyword(s):  
Reaction Times ◽  
Neural Correlates ◽  
Neural Representation ◽  
Neural Data ◽  
Active Condition ◽  
Behavioural Performance ◽  
Target Monitoring ◽  
The Brain ◽  
Insight Into ◽  
Over Time

AbstractThere are many monitoring environments, such as railway control, in which lapses of attention can have tragic consequences. Problematically, sustained monitoring for rare targets is difficult, with more misses and longer reaction times over time. What changes in the brain underpin these “vigilance decrements”? We designed a multiple-object monitoring (MOM) paradigm to examine how the neural representation of information varied with target frequency and time performing the task. Behavioural performance decreased over time for the rare target (monitoring) condition, but not for a frequent target (active) condition. This was mirrored in the neural results: there was weaker coding of critical information during monitoring versus active conditions. We developed new analyses that can predict behavioural errors from the neural data more than a second before they occurred. This paves the way for pre-empting behavioural errors due to lapses in attention and provides new insight into the neural correlates of vigilance decrements.

scholarly journals Revitalizing the Concept of Bond Order Through Delocalization Measures in Real Space

2018 ◽  
Author(s):  
Carlos Outeiral Rubiera ◽  
Mark Vincent ◽  
Ángel Martín Pendás ◽  
Paul L. A. Popelier
Keyword(s):  
Ab Initio ◽  
Quantum Chemical ◽  
Bond Order ◽  
Large Body ◽  
Real Space ◽  
Chemical Topology ◽  
Delocalization Index ◽  
Consistent Manner ◽  
Quantum Chemical Topology ◽  
Source Of Information

Ab initio quantum chemistry is an independent source of information supplying an ever widening group of experimental chemists. However, bridging the gap between these ab initio data and chemical insight remains a challenge. In particular, there is a need for a bond order index that characterizes novel bonding patterns in a reliable manner, while recovering the familiar effects occurring in well-known bonds. In this article, through a large body of calculations, we show how the delocalization index derived from Quantum Chemical Topology (QCT) serves as such a bond order. This index is defined in a parameter-free, intuitive and consistent manner, and with little qualitative dependency on the level of theory used. The delocalization index is also able to detect the subtler bonding effects that underpin most practical organic and inorganic chemistry. We explore and connect the properties of this index and open the door for its extensive usage in the understanding and discovery of novel chemistry.

scholarly journals Decoding the Neural Representation of Story Meanings across Languages

2017 ◽  
Author(s):  
Morteza Dehghani ◽  
Reihane Boghrati ◽  
Kingson Man ◽  
Joseph Hoover ◽  
Sarah Gimbel ◽  
...  
Keyword(s):  
Language Processing ◽  
Native Speakers ◽  
Semantic Space ◽  
Brain Regions ◽  
Narrative Comprehension ◽  
Neural Representation ◽  
High Dimensional ◽  
Distributed Representations ◽  
Neural Data ◽  
A New Technique

Drawing from a common lexicon of semantic units, humans fashion narratives whose meaning transcends that of their individual utterances. However, while brain regions that represent lower-level semantic units, such as words and sentences, have been identified, questions remain about the neural representation of narrative comprehension, which involves inferring cumulative meaning. To address these questions, we exposed English, Mandarin and Farsi native speakers to native language translations of the same stories during fMRI scanning. Using a new technique in natural language processing, we calculated the distributed representations of these stories (capturing the meaning of the stories in high-dimensional semantic space), and demonstrate that using these representations we can identify the specific story a participant was reading from the neural data. Notably, this was possible even when the distributed representations were calculated using stories in a different language than the participant was reading. Relying on over 44 billion classifications, our results reveal that identification relied on a collection of brain regions most prominently located in the default mode network. These results demonstrate that neuro-semantic encoding of narratives happens at levels higher than individual semantic units and that this encoding is systematic across both individuals and languages.

scholarly journals Revitalizing the Concept of Bond Order Through Delocalization Measures in Real Space

2018 ◽  
Author(s):  
Carlos Outeiral Rubiera ◽  
Mark Vincent ◽  
Ángel Martín Pendás ◽  
Paul L. A. Popelier
Keyword(s):  
Ab Initio ◽  
Quantum Chemical ◽  
Bond Order ◽  
Large Body ◽  
Real Space ◽  
Chemical Topology ◽  
Delocalization Index ◽  
Consistent Manner ◽  
Quantum Chemical Topology ◽  
Source Of Information

Ab initio quantum chemistry is an independent source of information supplying an ever widening group of experimental chemists. However, bridging the gap between these ab initio data and chemical insight remains a challenge. In particular, there is a need for a bond order index that characterizes novel bonding patterns in a reliable manner, while recovering the familiar effects occurring in well-known bonds. In this article, through a large body of calculations, we show how the delocalization index derived from Quantum Chemical Topology (QCT) serves as such a bond order. This index is defined in a parameter-free, intuitive and consistent manner, and with little qualitative dependency on the level of theory used. The delocalization index is also able to detect the subtler bonding effects that underpin most practical organic and inorganic chemistry. We explore and connect the properties of this index and open the door for its extensive usage in the understanding and discovery of novel chemistry.

Central Neural Mechanisms of Touch and Proprioception

1994 ◽  
Vol 72 (5) ◽  
pp. 542-545 ◽  
Author(s):  
John F. Kalaska
Keyword(s):  
Similar Case ◽  
Mechanical Stimulus ◽  
Muscle Contractions ◽  
Neural Mechanisms ◽  
Neural Representation ◽  
Perceptual Process ◽  
Active Muscle ◽  
Motivational State ◽  
Tactile Discrimination ◽  
Neuronal Mechanisms

The argument is made that somesthesia is not a strictly passive process, and its central neuronal mechanisms cannot be studied in all their complexity and subtlety by applying passive stimuli to uninterested or unconscious animals. The case is clear for kinesthesia. Peripheral proprioceptive signals are altered by active muscle contractions, and the central mechanisms of kinesthetic sensations should be studied during active movements. A similar case can be made for tactile discrimination. Ascending tactile afferents are subject to modulation during movement. Moreover, the generation of a central neural representation of the mechanical stimulus is only part of the tactile perceptual process. It is also influenced by the behavioral, attentive, and motivational state of the animal, whose effects can only be revealed in awake animals actively participating in discrimination tasks.Key words: tactile discrimination, proprioception, gating, attention, active touch.

scholarly journals Neural mechanisms underlying the precision of visual working memory

2018 ◽  
Author(s):  
Yijie Zhao ◽  
Shuguang Kuai ◽  
Theodore P. Zanto ◽  
Yixuan Ku
Keyword(s):  
Working Memory ◽  
Visual Working Memory ◽  
Memory Load ◽  
Neural Mechanisms ◽  
Behavioral Experiment ◽  
Working Memory Load ◽  
Lateral Occipital Complex ◽  
The Individual ◽  
Memory Precision ◽  
The Brain

AbstractThe neural mechanisms associated with the limited capacity of working memory has long been studied, but it is still unclear how the brain maintains the fidelity of representations in working memory. Here, an orientation recall task for estimating the precision of visual working memory was performed both inside and outside an fMRI scanner. Results showed that the trial-by-trial recall error (in radians) was correlated with delay period activity in the lateral occipital complex (LOC) during working memory maintenance, regardless of the memory load. Moreover, delay activity in LOC also correlated with the individual participant’s precision of working memory from a separate behavioral experiment held two weeks prior. Furthermore, a region within the prefrontal cortex, the inferior frontal junction (IFJ), exhibited greater functional connectivity with LOC when the working memory load increased. Together, our findings provide unique evidence that the LOC supports visual working memory precision, while communication between the IFJ and LOC varys with visual working memory load.

scholarly journals Working memory availability affects neural indices of distractor processing during visual search

2018 ◽  
Author(s):  
Dion T. Henare ◽  
Jude Buckley ◽  
Paul M. Corballis
Keyword(s):  
Working Memory ◽  
Visual Search ◽  
Memory Load ◽  
Individual Performance ◽  
Event Related Potential ◽  
Neural Mechanisms ◽  
Human Cognition ◽  
Working Memory Load ◽  
Distractor Processing ◽  
Selective Processing

AbstractWorking memory and selective attention are traditionally viewed as distinct processes in human cognition. However, increasing research demonstrates significant overlap between these constructs such that as working memory availability decreases, individuals perform worse on attention-based tasks. To date, the neural mechanisms involved in this interaction are unknown. We measured three candidate lateralized event-related potential components (N2pc, Ptc, and SPCN) to observe the effects of increased working memory load on selective processing of targets and distractors. We found that increased working memory load impaired the processing of distractors, but not targets, and this was reflected in attentuation of the Ptc to distractors. We also found that individual performance on the task is related to the neural response to both targets and distractors. This study suggests that working memory availability impacts individuals’ ability to disengage from irrelevant stimuli, and that individual differences in visual search ability under load are related to both target and distractor processing.

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