scholarly journals Contributions of magno- and parvocellular channels to conscious and non-conscious vision

2014 ◽  
Vol 369 (1641) ◽  
pp. 20130213 ◽  
Author(s):  
Bruno G. Breitmeyer
Keyword(s):  
Prefrontal Cortex ◽  
Neural Activity ◽  
Visual Information ◽  
Masked Priming ◽  
The Other ◽  
Future Research ◽  
Top Down ◽  
Pathway Activity ◽  
Feed Forward ◽  
Conscious Processing

The dorsal and ventral cortical pathways, driven predominantly by magnocellular (M) and parvocellular (P) inputs, respectively, assume leading roles in models of visual information processing. Although in prior proposals, the dorsal and ventral pathways support non-conscious and conscious vision, respectively, recent modelling and empirical developments indicate that each pathway plays important roles in both non-conscious and conscious vision. In these models, the ventral P-pathway consists of one subpathway processing an object's contour features, e.g. curvature, the other processing its surface attributes, e.g. colour. Masked priming studies have shown that feed-forward activity in the ventral P-pathway on its own supports non-conscious processing of contour and surface features. The dorsal M-pathway activity contributes directly to conscious vision of motion and indirectly to object vision by projecting to prefrontal cortex, which in turn injects top-down neural activity into the ventral P-pathway and there ‘ignites’ feed-forward–re-entrant loops deemed necessary for conscious vision. Moreover, an object's shape or contour remains invisible without the prior conscious registration of its surface properties, which for that reason are taken to comprise fundamental visual qualia. Besides suggesting avenues for future research, these developments bear on several recent and past philosophical issues.

scholarly journals Causal manipulation of feed-forward and recurrent processing differentially affects measures of consciousness

2020 ◽  
Vol 2020 (1) ◽  
Author(s):  
Christopher Allen ◽  
Tommaso Viola ◽  
Elizabeth Irvine ◽  
Jemma Sedgmond ◽  
Heidi Castle ◽  
...  
Keyword(s):  
Cognitive Processes ◽  
Neural Activity ◽  
Magnetic Stimulation ◽  
Conscious Perception ◽  
Top Down ◽  
Feed Forward ◽  
Cortical Dynamics ◽  
Recurrent Processing ◽  
Early Effects ◽  
Initial Processing

Abstract It has been theorized that cortical feed-forward and recurrent neural activity support unconscious and conscious cognitive processes, respectively. Here we causally tested this proposition by applying event-related transcranial magnetic stimulation (TMS) at early and late times relative to visual stimuli, together with a pulse designed to suppress conscious detection. Consistent with pre-registered hypotheses, early TMS affected residual, reportedly ‘unseen’ capacity. However, conscious perception also appeared critically dependent upon feed-forward processing to a greater extent than the later recurrent phase. Additional exploratory analyses suggested that these early effects dissociated from top-down criterion measures, which were most affected by later TMS. These findings are inconsistent with a simple dichotomy where feed-forward and recurrent processes correspond to unconscious and conscious mechanisms. Instead, different components of awareness may correspond to different phases of cortical dynamics in which initial processing is broadly perceptual whereas later recurrent processing might relate to decision to report.

scholarly journals Connectional architecture of the prefrontal cortex in the marmoset brain

2021 ◽  
Author(s):  
Akiya Watakabe ◽  
Henrik Skibbe ◽  
Ken Nakae ◽  
Hiroshi Abe ◽  
Noritaka Ichinohe ◽  
...  
Keyword(s):  
Prefrontal Cortex ◽  
Neuropsychiatric Disorders ◽  
The Other ◽  
Cortical Layers ◽  
Top Down ◽  
Corticostriatal Projections

The primate prefrontal cortex (PFC) has greatly expanded to evolve specialized architecture, but its roles in top-down brain control remain enigmatic. Based on connectomics mapping of the marmoset PFC, we characterized two contrasting features of corticocortical and corticostriatal projections. One is the "focalness" of projections, exemplified by multiple columnar axonal terminations in the cortical layers and the other is the "widespreadness" of weaker projections, whose patterns consisted of several common motifs representing the framework of PFC connectivity. We clarified the topographic rules of distribution for these features, which should constrain how PFC neurons can coordinate to control the target regions as populations. These features are observed only primitively in rodents and are considered critical in understanding the roles of the PFC in neuropsychiatric disorders.

Weight modulation in top–down computational model for target search

2021 ◽  
pp. 1-13
Author(s):  
R. Aarthi ◽  
J. Amudha
Keyword(s):  
Visual Information ◽  
Computational Models ◽  
Target Identification ◽  
The Other ◽  
Visual Features ◽  
Biological Models ◽  
Top Down ◽  
Target Search ◽  
Optimal Weights ◽  
Building Models

Computer vision research aims at building models which mimic human systems. The recent development in visual information have been used to derive computational models which address a variety of applications. Biological models help to identify the salient objects in the image. But, the identification of non-salient objects in a heterogeneous environment is a challenging task that requires a better understanding of the visual system. In this work, a weight modulation based top-down model is proposed that integrates the visual features that depend on its importance for the target search application. The model is designed to learn the optimal weights such that it biases the features of the target from the other surrounding regions. Experimental analysis is performed on various scenes on a standard dataset with the selected object in the scene. Metrics such as area under curve, average hit number and correlation reveal that the method is more suitable in target identification, by suppressing the other region.

scholarly journals Awake suppression after brief exposure to a familiar stimulus

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Ji Won Bang ◽  
Dobromir Rahnev
Keyword(s):  
Neural Activity ◽  
Activity Patterns ◽  
Visual Task ◽  
The Other ◽  
Familiar Stimulus ◽  
The Novel ◽  
Prior Training ◽  
Top Down ◽  
Other Hand ◽  
Familiar Stimuli

AbstractNewly learned information undergoes a process of awake reactivation shortly after the learning offset and we recently demonstrated that this effect can be observed as early as area V1. However, reactivating all experiences can be wasteful and unnecessary, especially for familiar stimuli. Therefore, here we tested whether awake reactivation occurs differentially for new and familiar stimuli. Subjects completed a brief visual task on a stimulus that was either novel or highly familiar due to extensive prior training on it. Replicating our previous results, we found that awake reactivation occurred in V1 for the novel stimulus. On the other hand, brief exposure to the familiar stimulus led to ‘awake suppression’ such that neural activity patterns immediately after exposure to the familiar stimulus diverged from the patterns associated with that stimulus. Further, awake reactivation was observed selectively in V1, whereas awake suppression had similar strength across areas V1–V3. These results are consistent with the presence of a competition between local awake reactivation and top-down awake suppression, with suppression becoming dominant for familiar stimuli.

scholarly journals Causal manipulation of feed-forward and recurrent processing differentially affects measures of consciousness

2019 ◽  
Author(s):  
Christopher P G Allen ◽  
Tommaso Viola ◽  
Elizabeth Irvine ◽  
Jemma Sedgmond ◽  
Heidi Castle ◽  
...  
Keyword(s):  
Cognitive Processes ◽  
Neural Activity ◽  
Magnetic Stimulation ◽  
Unconscious Perception ◽  
Top Down ◽  
Feed Forward ◽  
Cortical Dynamics ◽  
Recurrent Processing ◽  
Early Effects ◽  
Initial Processing

It has been theorised that cortical feed-forward and recurrent neural activity support unconscious and conscious cognitive processes, respectively. Here we causally tested this by applying event-related transcranial magnetic stimulation (TMS) at early and late times relative to visual stimuli, within the context of TMS-induced blindsight where consciousness and unconscious perception dissociate. Consistent with pre-registered hypotheses, early TMS affected residual, reportedly “unseen” capacity. However, conscious perception also appeared critically dependent upon feed-forward processing to a greater extent than the later recurrent phase. Additional exploratory analyses suggested that these early effects dissociated from top-down criterion measures, which were most affected by later TMS. These findings are inconsistent with a simple dichotomy where feed-forward and recurrent processes correspond to unconscious and conscious mechanisms. Instead, different aspects of awareness may correspond to different phases of cortical dynamics in which initial processing is broadly perceptual whereas later recurrent processing might relate to decision to report.

scholarly journals The integration of visual and target signals in V4 and IT during visual object search

2018 ◽  
Author(s):  
Noam Roth ◽  
Nicole C. Rust
Keyword(s):  
Visual Information ◽  
Visual Pathway ◽  
Target Object ◽  
Visual Object ◽  
Neural Responses ◽  
Top Down ◽  
Feed Forward ◽  
Object Search ◽  
Ventral Visual Pathway ◽  
Background Context

ABSTRACTSearching for a specific visual object requires our brain to compare the items in view with a remembered representation of the sought target to determine whether a target match is present. This comparison is thought to be implemented, in part, via the combination of top-down modulations reflecting target identity with feed-forward visual representations. However, it remains unclear whether top-down signals are integrated at a single locus within the ventral visual pathway (e.g. V4) or at multiple stages (e.g. both V4 and inferotemporal cortex, IT). To investigate, we recorded neural responses in V4 and IT as rhesus monkeys performed a task that required them to identify when a target object appeared across variation in position, size and background context. We found non-visual, task-specific signals in both V4 and IT. To evaluate whether V4 was the only locus for the integration of top-down signals, we evaluated several feed-forward accounts of processing from V4 to IT, including a model in which IT preferentially sampled from the best V4 units and a model that allowed for nonlinear IT computation. IT task-specific modulation was not accounted for by any of these feed-forward descriptions, suggesting that during object search, top-down signals are integrated directly within IT.NEW & NOTEWORTHYTo find specific objects, the brain must integrate top-down, target-specific signals with visual information about objects in view. However, the exact route of this integration in the ventral visual pathway is unclear. In the first study to systematically compare V4 and IT during an invariant object search task, we demonstrate that top-down signals found in IT cannot be described as being inherited from V4, but rather must be integrated directly within IT itself.

105 Incorporating Newly Learned with Established Information within the Prefrontal Cortical Network

Neurosurgery ◽  
2017 ◽  
Vol 64 (CN_suppl_1) ◽  
pp. 221-221
Author(s):  
Matthew Luchette ◽  
Ziv Williams
Keyword(s):  
Learning Disabilities ◽  
Prefrontal Cortex ◽  
Neural Activity ◽  
Rhesus Macaques ◽  
The Other ◽  
Transitive Relation ◽  
Prefrontal Cortical ◽  
New Information ◽  
New Association ◽  
Foraging Task

Abstract INTRODUCTION Learning does not occur in isolation, but often requires us to incorporate newly acquired information with previously established knowledge. To investigate the neural process by which this may occur, we trained macaques to learn the transitive relation between items and then subsequently incorporate new transitive relations across various branched paths, while recording from their ventral (vlPFC) and lateral (dlPFC) prefrontal cortices. METHODS We designed a foraging task, in which Rhesus macaques learned the transitive relationship between different presented items (e.g., A>B>C>D>E). The monkeys began by learning initial B-C associations, called the ‘Stem’. After learning the “Stem, ” the monkeys learned one of two “Branch” associations. In “Branch: Related trials, in which the learned associations built upon the ”Stem" (eg C>D or A>B). In the other, termed “Branch: Unrelated, ” the new association was novel and did not build upon the stem (eg D>E). RESULTS >We find that both the vlPFC and dlPFC displayed changes in neural activity that correlated with learning. However, only changes in dlPFC activity distinctly responded to the incorporation of new information. At the network level, interaction between the two areas gradually increased when incorporating new information but decreased when acquiring new but unrelated information. CONCLUSION These findings reveal a ventral-dorsal functional circuit in the prefrontal cortex that may allow for the integration of new and old information. These findings are an important step in characterizing the pathology of learning disabilities, such as Autism and Executive Function Disorder.

scholarly journals The integration of visual and target signals in V4 and IT during visual object search

2019 ◽  
Vol 122 (6) ◽  
pp. 2522-2540 ◽  
Author(s):  
Noam Roth ◽  
Nicole C. Rust
Keyword(s):  
Visual Information ◽  
Visual Pathway ◽  
Target Object ◽  
Visual Object ◽  
Neural Responses ◽  
Inferotemporal Cortex ◽  
Top Down ◽  
Feed Forward ◽  
Object Search ◽  
Ventral Visual Pathway

Searching for a specific visual object requires our brain to compare the items in view with a remembered representation of the sought target to determine whether a target match is present. This comparison is thought to be implemented, in part, via the combination of top-down modulations reflecting target identity with feed-forward visual representations. However, it remains unclear whether top-down signals are integrated at a single locus within the ventral visual pathway (e.g., V4) or at multiple stages [e.g., both V4 and inferotemporal cortex (IT)]. To investigate, we recorded neural responses in V4 and IT as rhesus monkeys performed a task that required them to identify when a target object appeared across variation in position, size, and background context. We found nonvisual, task-specific signals in both V4 and IT. To evaluate whether V4 was the only locus for the integration of top-down signals, we evaluated several feed-forward accounts of processing from V4 to IT, including a model in which IT preferentially sampled from the best V4 units and a model that allowed for nonlinear IT computation. IT task-specific modulation was not accounted for by any of these feed-forward descriptions, suggesting that during object search, top-down signals are integrated directly within IT. NEW & NOTEWORTHY To find specific objects, the brain must integrate top-down, target-specific signals with visual information about objects in view. However, the exact route of this integration in the ventral visual pathway is unclear. In the first study to systematically compare V4 and inferotemporal cortex (IT) during an invariant object search task, we demonstrate that top-down signals found in IT cannot be described as being inherited from V4 but rather must be integrated directly within IT itself.

Masked Translation Priming Effects With Highly Proficient Simultaneous Bilinguals

2010 ◽  
Vol 57 (2) ◽  
pp. 98-107 ◽  
Author(s):  
Jon Andoni Duñabeitia ◽  
Manuel Perea ◽  
Manuel Carreiras
Keyword(s):  
Lexical Decision ◽  
Hierarchical Model ◽  
Priming Effect ◽  
Masked Priming ◽  
The Other ◽  
Memory Organization ◽  
Priming Effects ◽  
Bilingual Memory ◽  
Translation Priming ◽  
Masked Translation Priming

One essential issue for models of bilingual memory organization is to what degree the representation from one of the languages is shared with the other language. In this study, we examine whether there is a symmetrical translation priming effect with highly proficient, simultaneous bilinguals. We conducted a masked priming lexical decision experiment with cognate and noncognate translation equivalents. Results showed a significant masked translation priming effect for both cognates and noncognates, with a greater priming effect for cognates. Furthermore, the magnitude of the translation priming was similar in the two directions. Thus, highly fluent bilinguals do develop symmetrical between-language links, as predicted by the Revised Hierarchical model and the BIA+ model. We examine the implications of these results for models of bilingual memory.

Sign in / Sign up

Export Citation Format

Share Document