scholarly journals Estimating null and potent modes of feedforward communication in a computational model of cortical activity

2022 ◽  
Vol 12 (1) ◽  
Author(s):  
Jean-Philippe Thivierge ◽  
Artem Pilzak
Keyword(s):  
Visual Processing ◽  
Null Space ◽  
Motor Processes ◽  
Cortical Areas ◽  
Pairwise Correlations ◽  
Neural Interactions ◽  
Modes Of Interaction ◽  
Systematic Control ◽  
The Brain

AbstractCommunication across anatomical areas of the brain is key to both sensory and motor processes. Dimensionality reduction approaches have shown that the covariation of activity across cortical areas follows well-delimited patterns. Some of these patterns fall within the "potent space" of neural interactions and generate downstream responses; other patterns fall within the "null space" and prevent the feedforward propagation of synaptic inputs. Despite growing evidence for the role of null space activity in visual processing as well as preparatory motor control, a mechanistic understanding of its neural origins is lacking. Here, we developed a mean-rate model that allowed for the systematic control of feedforward propagation by potent and null modes of interaction. In this model, altering the number of null modes led to no systematic changes in firing rates, pairwise correlations, or mean synaptic strengths across areas, making it difficult to characterize feedforward communication with common measures of functional connectivity. A novel measure termed the null ratio captured the proportion of null modes relayed from one area to another. Applied to simultaneous recordings of primate cortical areas V1 and V2 during image viewing, the null ratio revealed that feedforward interactions have a broad null space that may reflect properties of visual stimuli.

The Cerebellum Generates Motor-to-Auditory Predictions: ERP Lesion Evidence

2012 ◽  
Vol 24 (3) ◽  
pp. 698-706 ◽  
Author(s):  
Franziska Knolle ◽  
Erich Schröger ◽  
Pamela Baess ◽  
Sonja A. Kotz
Keyword(s):  
Cognitive Processes ◽  
Sensory Input ◽  
Forward Model ◽  
Motor Action ◽  
Suppression Effect ◽  
Motor Processes ◽  
Cortical Areas ◽  
Internal Forward Model ◽  
Cerebellar Lesions

Forward predictions are crucial in motor action (e.g., catching a ball, or being tickled) but may also apply to sensory or cognitive processes (e.g., listening to distorted speech or to a foreign accent). According to the “internal forward model,” the cerebellum generates predictions about somatosensory consequences of movements. These predictions simulate motor processes and prepare respective cortical areas for anticipated sensory input. Currently, there is very little evidence that a cerebellar forward model also applies to other sensory domains. In the current study, we address this question by examining the role of the cerebellum when auditory stimuli are anticipated as a consequence of a motor act. We applied an N100 suppression paradigm and compared the ERP in response to self-initiated with the ERP response to externally produced sounds. We hypothesized that sensory consequences of self-initiated sounds are precisely predicted and should lead to an N100 suppression compared with externally produced sounds. Moreover, if the cerebellum is involved in the generation of a motor-to-auditory forward model, patients with focal cerebellar lesions should not display an N100 suppression effect. Compared with healthy controls, patients showed a largely attenuated N100 suppression effect. The current results suggest that the cerebellum forms not only motor-to-somatosensory predictions but also motor-to-auditory predictions. This extends the cerebellar forward model to other sensory domains such as audition.

A new look at the potential of the brain to change as a result of early experience: The possible role of glutamate in early learning and retardation

1993 ◽  
Vol 10 (2) ◽  
pp. 31-38
Author(s):  
Amy N. Johnston
Keyword(s):  
Neural Plasticity ◽  
Early Learning ◽  
Close Link ◽  
Early Brain Development ◽  
Neural Interactions ◽  
Early Memory ◽  
The Times ◽  
The Brain ◽  
Neurochemical Investigation

AbstractLateralized brain function was originally thought to be unique to humans, but it has now been demonstrated to occur in many animal species, including primates, rats, dogs, and birds. Memory consolidation and retrieval in chicks is lateralized in neuroanatomical areas used and also in the times these areas are active. As the general patterns of memory encoding, elucidated in chicks, might also occur in humans, chicks are used as a model system for studying learning and memory. In addition, the detailed neurochemical investigation of imprinting has shown that the neurotransmitter glutamate plays an important role in the consolidation of early learning. Glutamate is also known to be important in neural plasticity, and a close link is now seen between early memory formation and the neural plastic events of early brain development. Behavioural testing using chicks has shown that glutamate intake can cause retardation of visual discrimination learning. This is of some concern given the common use of glutamate as a food additive. Clearly the role and indeed the presence of glutamate in the brain are finely balanced. This information is leading us to a greater understanding of the brain and its dynamic interaction with its environment. It also reinforces the increasing concerns regarding neural interactions with environmental roxins.

scholarly journals Neural, functional, and aesthetic impacts of spatially heterogeneous flicker: A potential role of natural flicker

2019 ◽  
Author(s):  
Melisa Menceloglu ◽  
Marcia Grabowecky ◽  
Satoru Suzuki
Keyword(s):  
Visual System ◽  
Visual Processing ◽  
Top Down ◽  
Aesthetic Responses ◽  
Beta Power ◽  
Neural Interactions ◽  
The Aesthetic ◽  
Sensory Activation ◽  
Motion Detectors

AbstractSpatially heterogeneous flicker, characterized by probabilistic and locally independent luminance modulations, abounds in nature. It is generated by flames, water surfaces, rustling leaves, and so on, and it is pleasant to the senses. It affords spatiotemporal multistability that allows sensory activation conforming to the biases of the visual system, thereby generating the perception of spontaneous motion and likely facilitating the calibration of motion detectors. One may thus hypothesize that spatially heterogeneous flicker might potentially provide restoring stimuli to the visual system that engage fluent (requiring minimal top-down control) and self-calibrating processes. Here, we present some converging behavioral and electrophysiological evidence consistent with this idea. Spatially heterogeneous (multistable) flicker (relative to controls matched in temporal statistics) reduced posterior EEG (electroencephalography) beta power implicated in long-range neural interactions that impose top-down influences on sensory processing. Further, the degree of spatiotemporal multistability, the amount of posterior beta-power reduction, and the aesthetic responses to flicker were closely associated. These results are consistent with the idea that the pleasantness of natural flicker may derive from its spatiotemporal multistability that affords fluent and self-calibrating visual processing.

scholarly journals Indication of Disrupted Temporal Structure in the Case of Thought Blocks in Schizophrenia: The Role of the Metastable Balance

2018 ◽  
Vol 2018 ◽  
pp. 1-8
Author(s):  
Elias Koutsoukos ◽  
Elias Angelopoulos
Keyword(s):  
Metastable State ◽  
Temporal Structure ◽  
Mental Processes ◽  
Brain Areas ◽  
Specific Symptom ◽  
Auditory Verbal Hallucinations ◽  
Cortical Areas ◽  
The Brain

This study is aimed at investigating probable disruption of the metastable balance relevant to a disruption of the mental processes observed in the neurophenomenal level. This disruption was found to occur under dense auditory verbal hallucinations (AVHs) which are accompanied by thought blocking (TB) phenomena. The entropy that quantifies the complexity of the spontaneous coupling has been used to describe the observed transitions. According to our findings, the high synchrony-derived entropy (SE) defines a metastable state, where formations of cortical areas are able to coordinate transiently under the demands of stimulus-oriented processes or other internal cognitive associations. It was also found that the disruption of the sensitive balance to the side of oversynergy (overconnectedness) rather than the side of independence (coincidental coupling) is relevant with functional fixations under the specific symptom of schizophrenia. An introduced measure relative to the persistence of coupling indicated that the overcoupled brain areas exhibit a kind of “stiffness” in processing incoherent phasic components. Our consideration enhances the understanding of the role the metastability plays in the interpretation of deeply subjective phenomena, such as AVHs and TBs that affect the normal information routing in the brain.

scholarly journals Turning the Stimulus On and Off Dynamically Changes the Direction of Alpha Traveling Waves

2020 ◽  
Author(s):  
Zhaoyang Pang ◽  
Andrea Alamia ◽  
Rufin VanRullen
Keyword(s):  
Traveling Waves ◽  
Visual Processing ◽  
Visual Stimulation ◽  
Visual Inputs ◽  
Eeg Recordings ◽  
The Moment ◽  
Task Conditions ◽  
The Waves ◽  
The Brain

AbstractTraveling waves have been studied to characterize the complex spatiotemporal dynamics of the brain. Several studies have suggested that the propagation direction of alpha traveling waves can be task-dependent. For example, a recent EEG study from our group found that forward waves (i.e. occipital to frontal, FW waves) were observed during visual processing, whereas backward waves (i.e. frontal to occipital, BW waves) mostly occurred in the absence of sensory input. These EEG recordings, however, were obtained from different experimental sessions and different groups of subjects. To further examine how the waves’ direction changes between task conditions, 13 participants were tested on a target detection task while EEG signals were recorded simultaneously. We alternated visual stimulation (5 s display of visual luminance sequences) and resting state (5 s of black screen) within each single trial, allowing us to monitor the moment-to-moment progression of traveling waves. As expected, the direction of alpha waves was closely linked with task conditions. First, FW waves from occipital to frontal regions, absent during rest, emerged as a result of visual processing, while BW waves in the opposite direction dominated in the absence of visual inputs, and were reduced (but not eliminated) by external visual inputs. Second, during visual stimulation (but not rest), both waves coexisted on average, but were negatively correlated. In summary, we conclude that the functional role of alpha traveling waves is closely related with their propagating direction, with stimulus-evoked FW waves supporting visual processing and spontaneous BW waves involved more in top-down control.

scholarly journals From Intermodulation Components to Perception and Cognition- a Review

2019 ◽  
Author(s):  
Noam Gordon ◽  
Jakob Hohwy ◽  
Matthew James Davidson ◽  
Jeroen van Boxtel ◽  
Naotsugu Tsuchiya
Keyword(s):  
Visual Processing ◽  
Future Directions ◽  
Complex Interactions ◽  
Visual Processes ◽  
Neural Integration ◽  
Neuroimaging Data ◽  
Neural Interactions ◽  
Integration Mechanisms ◽  
High Level ◽  
The Brain

Perception results from complex interactions among sensory and cognitive processes across hierarchical levels in the brain. Intermodulation (IM) components, used in frequency tagging neuroimaging designs, have emerged as a promising direct measure of such neural interactions. IMs have initially been used in electroencephalography (EEG) to investigate low-level visual processing. In a more recent trend, IMs in EEG and other neuroimaging methods are being used to shed light on mechanisms of mid- and high-level perceptual processes, including the involvement of cognitive functions such as attention and expectation. Here, we provide an account of various mechanisms that may give rise to IMs in neuroimaging data, and what these IMs may look like. We discuss methodologies that can be implemented for different uses of IMs and we demonstrate how IMs can provide insights into the existence, the degree and the type of neural integration mechanisms at hand. We then review a range of recent studies exploiting IMs in perception research, placing an emphasis on high-level visual processes. We conclude by suggesting future directions that can enhance the benefits of IM-methodology in perception research.

The Role of Mitochondria in the Genesis of Neuroaxonal Dystrophy in the Brains of Aging Mice

1975 ◽  
Vol 33 ◽  
pp. 372-373
Author(s):  
J.E. Johnson
Keyword(s):  
Electron Microscopy ◽  
Present Report ◽  
Light And Electron Microscopy ◽  
Dorsal Column ◽  
Neuroaxonal Dystrophy ◽  
Nucleus Gracilis ◽  
Dystrophic Axons ◽  
The Brain ◽  
Nucleus Cuneatus

Although neuroaxonal dystrophy (NAD) has been examined by light and electron microscopy for years, the nature of the components in the dystrophic axons is not well understood. The present report examines nucleus gracilis and cuneatus (the dorsal column nuclei) in the brain stem of aging mice.Mice (C57BL/6J) were sacrificed by aldehyde perfusion at ages ranging from 3 months to 23 months. Several brain areas and parts of other organs were processed for electron microscopy.At 3 months of age, very little evidence of NAD can be discerned by light microscopy. At the EM level, a few axons are found to contain dystrophic material. By 23 months of age, the entire nucleus gracilis is filled with dystrophic axons. Much less NAD is seen in nucleus cuneatus by comparison. The most recurrent pattern of NAD is an enlarged profile, in the center of which is a mass of reticulated material (reticulated portion; or RP).

Top-Down Processing and Visual Reorientation Illusions in a Virtual Reality Environment

2004 ◽  
Vol 63 (3) ◽  
pp. 143-149 ◽  
Author(s):  
Fred W. Mast ◽  
Charles M. Oman
Keyword(s):  
Virtual Reality ◽  
Visual Processing ◽  
Line Length ◽  
Perceptual Cues ◽  
Virtual Reality Environment ◽  
Top Down ◽  
Test Conditions ◽  
The Subject ◽  
Processing Mechanisms

The role of top-down processing on the horizontal-vertical line length illusion was examined by means of an ambiguous room with dual visual verticals. In one of the test conditions, the subjects were cued to one of the two verticals and were instructed to cognitively reassign the apparent vertical to the cued orientation. When they have mentally adjusted their perception, two lines in a plus sign configuration appeared and the subjects had to evaluate which line was longer. The results showed that the line length appeared longer when it was aligned with the direction of the vertical currently perceived by the subject. This study provides a demonstration that top-down processing influences lower level visual processing mechanisms. In another test condition, the subjects had all perceptual cues available and the influence was even stronger.

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