Thalamocortical Interactions for Sensory Processing

2017 ◽  
Author(s):  
Jose M. Alonso ◽  
Harvey A. Swadlow
Keyword(s):  
Cerebral Cortex ◽  
Sensory Modality ◽  
Sensory Information ◽  
Main Stream ◽  
Axon Terminals ◽  
Sensory Maps ◽  
Corticothalamic Feedback ◽  
The Brain ◽  
High Firing ◽  
Thalamocortical Pathway

The thalamocortical pathway is the main route of sensory information to the cerebral cortex. Vision, touch, hearing, taste, and balance all depend on the integrity of this pathway that connects the thalamic structures receiving sensory input with the cortical areas specialized in each sensory modality. Only the ancient sense of smell is independent of the thalamus, gaining access to cortex through more anterior routes. While the thalamocortical pathway targets different layers of the cerebral cortex, its main stream projects to the middle layers and has axon terminals that are dense, spatially restricted, and highly specific in their connections. The remarkable specificity of these thalamocortical connections allows for a precise reconstruction of the sensory dimensions that need to be most finely sampled, such as spatial acuity in vision and sound frequency in hearing. The thalamic axon terminals also segregate topographically according to their stimulus preferences, providing a simple principle to build cortical sensory maps: neighboring values in sensory space are represented by neighboring points within the cortex. Thalamocortical processing is not static. It is continuously modulated by the brain stem and corticothalamic feedback based on the level of attention and alertness, and during sleep or general anesthesia. When alert, visual thalamic responses become stronger, more reliable, more sustained, more effective at sampling fast changes in the scene, and more linearly related to the stimulus. The high firing rates of the alert state make thalamocortical synapses chronically depressed and excitatory synaptic potentials less dependent on temporal history, improving even further the linear relation between stimulus and response. In turn, when alertness wanes, the thalamus reduces its firing rate, and starts generating spike bursts that drive large postsynaptic responses and keep the cortex responsive to sudden stimulus changes.

scholarly journals Widespread inhibition, antagonism, and synergy in mouse olfactory sensory neurons in vivo

2019 ◽  
Author(s):  
Shigenori Inagaki ◽  
Ryo Iwata ◽  
Masakazu Iwamoto ◽  
Takeshi Imai
Keyword(s):  
Sensory Neurons ◽  
Calcium Imaging ◽  
Odorant Receptor ◽  
Sensory Information ◽  
Olfactory Sensory Neurons ◽  
Axon Terminals ◽  
Two Photon ◽  
Odor Mixtures ◽  
The Brain

SUMMARYSensory information is selectively or non-selectively inhibited and enhanced in the brain, but it remains unclear whether this occurs commonly at the peripheral stage. Here, we performed two-photon calcium imaging of mouse olfactory sensory neurons (OSNs) in vivo and found that odors produce not only excitatory but also inhibitory responses at their axon terminals. The inhibitory responses remained in mutant mice, in which all possible sources of presynaptic lateral inhibition were eliminated. Direct imaging of the olfactory epithelium revealed widespread inhibitory responses at OSN somata. The inhibition was in part due to inverse agonism toward the odorant receptor. We also found that responses to odor mixtures are often suppressed or enhanced in OSNs: Antagonism was dominant at higher odor concentrations, whereas synergy was more prominent at lower odor concentrations. Thus, odor responses are extensively tuned by inhibition, antagonism, and synergy, at the early peripheral stage, contributing to robust odor representations.

scholarly journals Human Development XI: The Structure of the Cerebral Cortex. Are There Really Modules in the Brain?

2007 ◽  
Vol 7 ◽  
pp. 1922-1929 ◽  
Author(s):  
Tyge Dahl Hermansen ◽  
Søren Ventegodt ◽  
Isack Kandel
Keyword(s):  
Cerebral Cortex ◽  
Brain Activity ◽  
Sensory Cortex ◽  
Biological Information ◽  
Human Consciousness ◽  
Primary Sensory Cortex ◽  
Sensory Maps ◽  
The World ◽  
The Brain ◽  
The Universe

The structure of human consciousness is thought to be closely connected to the structure of cerebral cortex. One of the most appreciated concepts in this regard is the Szanthagothei model of a modular building of neo-cortex. The modules are believed to organize brain activity pretty much like a computer. We looked at examples in the literature and argue that there is no significant evidence that supports Szanthagothei's model. We discuss the use of the limited genetic information, the corticocortical afferents termination and the columns in primary sensory cortex as arguments for the existence of the cortex-module. Further, we discuss the results of experiments with Luminization Microscopy (LM) colouration of myalinized fibres, in which vertical bundles of afferent/efferent fibres that could support the cortex module are identified. We conclude that sensory maps seem not to be an expression for simple specific connectivity, but rather to be functional defined. We also conclude that evidence for the existence of the postulated module or column does not exist in the discussed material. This opens up for an important discussion of the brain as functionally directed by biological information (information-directed self-organisation), and for consciousness being closely linked to the structure of the universe at large. Consciousness is thus not a local phenomena limited to the brain, but a much more global phenomena connected to the wholeness of the world.

scholarly journals Hand size underestimation grows during childhood

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Lucilla Cardinali ◽  
Andrea Serino ◽  
Monica Gori
Keyword(s):  
Motor Behavior ◽  
Sensory Modality ◽  
The Body ◽  
Typically Developing ◽  
Cognitive Representations ◽  
Hand Size ◽  
Infancy And Childhood ◽  
Sensory Modalities ◽  
Sensory Maps ◽  
The Brain

Abstract Cortical body size representations are distorted in the adult, from low-level motor and sensory maps to higher levels multisensory and cognitive representations. Little is known about how such representations are built and evolve during infancy and childhood. Here we investigated how hand size is represented in typically developing children aged 6 to 10. Participants were asked to estimate their hand size using two different sensory modalities (visual or haptic). We found a distortion (underestimation) already present in the youngest children. Crucially, such distortion increases with age and regardless of the sensory modality used to access the representation. Finally, underestimation is specific for the body as no bias was found for object estimation. This study suggests that the brain does not keep up with the natural body growth. However, since motor behavior nor perception were impaired, the distortion seems functional and/or compensated for, for proper interaction with the external environment.

scholarly journals Cortical mechanisms of action selection: the affordance competition hypothesis

2007 ◽  
Vol 362 (1485) ◽  
pp. 1585-1599 ◽  
Author(s):  
Paul Cisek
Keyword(s):  
Cerebral Cortex ◽  
Action Plan ◽  
Sensory Information ◽  
Natural World ◽  
Mechanisms Of Action ◽  
Competition Hypothesis ◽  
The World ◽  
Neurophysiological Data ◽  
Single Response ◽  
The Brain

At every moment, the natural world presents animals with two fundamental pragmatic problems: selection between actions that are currently possible and specification of the parameters or metrics of those actions. It is commonly suggested that the brain addresses these by first constructing representations of the world on which to build knowledge and make a decision, and then by computing and executing an action plan. However, neurophysiological data argue against this serial viewpoint. In contrast, it is proposed here that the brain processes sensory information to specify, in parallel, several potential actions that are currently available. These potential actions compete against each other for further processing, while information is collected to bias this competition until a single response is selected. The hypothesis suggests that the dorsal visual system specifies actions which compete against each other within the fronto-parietal cortex, while a variety of biasing influences are provided by prefrontal regions and the basal ganglia. A computational model is described, which illustrates how this competition may take place in the cerebral cortex. Simulations of the model capture qualitative features of neurophysiological data and reproduce various behavioural phenomena.

scholarly journals The neural computations for stimulus presence and modal identity diverge along a shared circuit

2020 ◽  
Author(s):  
David A. Tovar ◽  
Jean-Paul Noel ◽  
Yumiko Ishizawa ◽  
Shaun R. Patel ◽  
Emad N. Eskandar ◽  
...  
Keyword(s):  
Sensory Modality ◽  
Sensory Information ◽  
Tactile Stimuli ◽  
Neural Computations ◽  
Stimulus Identity ◽  
Time Courses ◽  
And Function ◽  
Core Characteristics ◽  
The Brain ◽  
Spiking Activity

AbstractThe brain is comprised of neural circuits that are able to flexibly represent the complexity of the external world. In accomplishing this feat, one of the first attributes the brain must code for is whether a stimulus is present and subsequently what sensory information that stimulus contains. One of the core characteristics of that information is which sensory modality(ies) are being represented. How information regarding both the presence and modal identity of a given stimulus is represented and transformed within the brain remains poorly understood. In this study, we investigated how the brain represents the presence and modal identity of a given stimulus while tactile, audio, and audio-tactile stimuli were passively presented to non-human primates. We recorded spiking activity from primary somatosensory (S1) and ventral pre-motor (PMv) cortices, two areas known to be instrumental in transforming sensory information into motor commands for action. Using multivariate analyses to decode stimulus presence and identity, we found that information regarding stimulus presence and modal identity were found in both S1 and PMv and extended beyond the duration of significant evoked spiking activity, and that this information followed different time-courses in these two areas. Further, we combined time-generalization decoding with cross-area decoding to demonstrate that while signaling the presence of a stimulus involves a feedforward-feedback coupling between S1-PMv, the processing of modal identity is largely restricted to S1. Together, these results highlight the differing spatiotemporal dynamics of information flow regarding stimulus presence and modal identity in two nodes of an important cortical sensorimotor circuit.Significance StatementIt is unclear how the structure and function of the brain support differing sensory functions, such as detecting the presence of a stimulus in the environment vs. identifying it. Here, we used multivariate decoding methods on monkey neuronal data to track how information regarding stimulus presence and modal identity flow within a sensorimotor circuit. Results demonstrate that while neural patterns in both primary somatosensory (S1) and ventral pre-motor (PMv) cortices can be used to detect and discriminate between stimuli, they follow different time-courses. Importantly, findings suggest that while information regarding the presence of a stimulus flows reciprocally between S1 and PMv, information regarding stimulus identity is largely contained in S1.

scholarly journals Embryonic Brain’s Spontaneous Activity Promote Synesthesia?

2019 ◽  
Author(s):  
J. Shashi Kiran Reddy ◽  
Georg Northoff
Keyword(s):  
Neural Network ◽  
Embryonic Development ◽  
Brain Development ◽  
Spontaneous Activity ◽  
Sensory Information ◽  
Neural Connectivity ◽  
Neural Pathway ◽  
Sensory Maps ◽  
The Brain

Antón-Bolaños et al. (2019) report a newly identified neural pathway mechanism, where the patterned spontaneous activity regulates the excitability of a neural network essential for the formation and maintenance of functional sensory maps in the brain. Findings from the study suggest that the patterned spontaneous activity prevalent during the embryonic development of the brain; at the early stages of innervation to the cortex, contributes to the formation of these sensory maps. Synesthesia is a neural phenomenon caused by the unusual links between sensory information, where synesthetic subjects demonstrate atypical functional and neural connectivity caused by the differences in cortical wiring during brain development. So, based on the findings from Antón-Bolaños et al. (2019), one can anticipate the role of spontaneous activity in promoting synesthetic condition. Thus, it will be interesting to study, if the intrinsic spontaneous activity influences the differential cortical wiring and the formation of sensory maps in synesthesia.

scholarly journals Stop signals delay synchrony more for finger tapping than vocalization: a dual modality study of rhythmic synchronization in the stop signal task

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e5242 ◽  
Author(s):  
Leidy J. Castro-Meneses ◽  
Paul F. Sowman
Keyword(s):  
Response Times ◽  
Sensory Modality ◽  
Sensory Information ◽  
Reaction Times ◽  
Proactive Inhibition ◽  
Stop Signal ◽  
Finger Tapping ◽  
Stop Signal Task ◽  
Auditory Modality ◽  
The Brain

Background A robust feature of sensorimotor synchronization (SMS) performance in finger tapping to an auditory pacing signal is the negative asynchrony of the tap with respect to the pacing signal. The Paillard–Fraisse hypothesis suggests that negative asynchrony is a result of inter-modal integration, in which the brain compares sensory information across two modalities (auditory and tactile). The current study compared the asynchronies of vocalizations and finger tapping in time to an auditory pacing signal. Our first hypothesis was that vocalizations have less negative asynchrony compared to finger tapping due to the requirement for sensory integration within only a single (auditory) modality (intra-modal integration). However, due to the different measurements for vocalizations and finger responses, interpreting the comparison between these two response modalities is problematic. To address this problem, we included stop signals in the synchronization task. The rationale for this manipulation was that stop signals would perturb synchronization more in the inter-modal compared to the intra-modal task. We hypothesized that the inclusion of stop signals induce proactive inhibition, which reduces negative asynchrony. We further hypothesized that any reduction in negative asynchrony occurs to a lesser degree for vocalization than for finger tapping. Method A total of 30 participants took part in this study. We compared SMS in a single sensory modality (vocalizations (or auditory) to auditory pacing signal) to a dual sensory modality (fingers (or tactile) to auditory pacing signal). The task was combined with a stop signal task in which stop signals were relevant in some blocks and irrelevant in others. Response-to-pacing signal asynchronies and stop signal reaction times were compared across modalities and across the two types of stop signal blocks. Results In the blocks where stopping was irrelevant, we found that vocalization (−61.47 ms) was more synchronous with the auditory pacing signal compared to finger tapping (−128.29 ms). In the blocks where stopping was relevant, stop signals induced proactive inhibition, shifting the response times later. However, proactive inhibition (26.11 ms) was less evident for vocalizations compared to finger tapping (58.06 ms). Discussion These results support the interpretation that relatively large negative asynchrony in finger tapping is a consequence of inter-modal integration, whereas smaller asynchrony is associated with intra-modal integration. This study also supports the interpretation that intra-modal integration is more sensitive to synchronization discrepancies compared to inter-modal integration.

Neurophysiological disturbances of cognitive processing in Alzheimer and multi-infarct dementia. An evoked potential study

1994 ◽  
Vol 6 (4) ◽  
pp. 69-73
Author(s):  
E.J. Colon
Keyword(s):  
Cerebral Cortex ◽  
Information Processing ◽  
Evoked Potentials ◽  
Cognitive Processing ◽  
Glial Cells ◽  
Evoked Potential ◽  
Sensory Information ◽  
Short Latency ◽  
And Storage ◽  
The Brain

SummaryDisturbances in information processing can be established by means of evoked potentials (EP). Sensory information is transported over the white myelinated fibers towards the brain. Classification and storage will take place in the cortical grey. This kind of information processing can be made visible by means of EP's.In 9 patients with dementia. Alzheimer's type and 7 patients with multi-infarct dementia a delay in information processing has been established by means of EP's. In multi-infarct dementia also a delay in short latency components was determined. The generators of various parts of the information processing in the cerebral cortex have been delayed and distorted. We speculate that, beside loss of neurons in the cerebral cortex, an alteration in cortical glial cells might be the cause of some disturbances in patients with dementia.

scholarly journals Effects of auditory reliability and ambiguous visual stimuli on auditory spatial discrimination

2020 ◽  
Author(s):  
Madeline S. Cappelloni ◽  
Sabyasachi Shivkumar ◽  
Ralf M. Haefner ◽  
Ross K. Maddox
Keyword(s):  
Causal Inference ◽  
Correct Response ◽  
Visual Information ◽  
Discrimination Task ◽  
Sensory Modality ◽  
Visual Stimuli ◽  
Sensory Information ◽  
Spatial Discrimination ◽  
Auditory Information ◽  
The Brain

ABSTRACTThe brain combines information from multiple sensory modalities to interpret the environment. Multisensory integration is often modeled by ideal Bayesian causal inference, a model proposing that perceptual decisions arise from a statistical weighting of information from each sensory modality based on its reliability and relevance to the observer’s task. However, ideal Bayesian causal inference fails to describe human behavior in a simultaneous auditory spatial discrimination task in which spatially aligned visual stimuli improve performance despite providing no information about the correct response. This work tests the hypothesis that humans weight auditory and visual information in this task based on their relative reliabilities, even though the visual stimuli are task-uninformative, carrying no information about the correct response, and should be given zero weight. Listeners perform an auditory spatial discrimination task with relative reliabilities modulated by the stimulus durations. By comparing conditions in which task-uninformative visual stimuli are spatially aligned with auditory stimuli or centrally located (control condition), listeners are shown to have a larger multisensory effect when their auditory thresholds are worse. Even in cases in which visual stimuli are not task-informative, the brain combines sensory information that is scene-relevant, especially when the task is difficult due to unreliable auditory information.

scholarly journals The role of the odorant receptors in the formation of the sensory map

BMC Biology ◽  
2021 ◽  
Vol 19 (1) ◽  
Author(s):  
Simona Francia ◽  
Claudia Lodovichi
Keyword(s):  
Olfactory System ◽  
Odorant Receptors ◽  
Axon Terminals ◽  
Sensory Axons ◽  
Sensory Maps ◽  
And Function ◽  
Sensory Map ◽  
Target Locations ◽  
The Brain

AbstractIn the olfactory system, odorant receptors (ORs) expressed at the cell membrane of olfactory sensory neurons detect odorants and direct sensory axons toward precise target locations in the brain, reflected in the presence of olfactory sensory maps. This dual role of ORs is corroborated by their subcellular expression both in cilia, where they bind odorants, and at axon terminals, a location suitable for axon guidance cues. Here, we provide an overview and discuss previous work on the role of ORs in establishing the topographic organization of the olfactory system and recent findings on the mechanisms of activation and function of axonal ORs.

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