Cortical hierarchy

Cortical information processing is structurally and functionally organized into hierarchical pathways, cortical hierarchy, with primary cortical hierarchy cortical regions providing modality specific information and associative cortical regions playing a more integrative role. Historically, there has been debate as to whether primary cortical regions mature earlier than associative cortical regions, or whether both primary and associative cortical regions mature simultaneously. Identifying whether primary and associative cortical regions mature hierarchically or simultaneously will not only deepen our understanding of the mechanisms that regulate brain maturation, but it will also provide fundamental insight into aspects of adolescent behavior, learning, cortical hierarchy, neurodevelopmental disorders and computational models of neural processing. This mini-review article summarizes the current evidence supporting the sequential and hierarchical nature of cortical maturation, and then proposes a new cellular model underlying this process.

Hierarchical cortical organization is found in all sensory systems, in the reward system, and in the memory systems. Adjacent cortical areas in the hierarchy are connected by strong forward connections, and weaker backprojections which have synapses in cortical layer 1. There is convergence from cortical area to cortical area, in that neurons in a cortical area receive inputs from a limited region topologically of the preceding cortical area. This enables neurons to operate with the number of synapses from the preceding cortical area received by a neuron limited to in the order of 10, synapses. This is a major cortical principle of operation, for if each processing system consisted of only an input and an output cortical area, any neuron in the output area would need to receive the biologically implausible number of tens of millions of synapses to cover the whole space of the input cortical area. The convergence from cortical area to cortical area is such that after approximately at most four areas or stages of cortical processing, the convergence is sufficient to enable a single neuron at the top of the hierarchy to receive input from anywhere in the first cortical area, as illustrated in Fig.

Cortical hierarchy

A fundamental aspect of human experience is that it is segmented into discrete events. This may be underpinned by transitions between distinct neural states. Using an innovative data-driven state segmentation method, we investigate how neural states are organized across the cortical hierarchy and where in the cortex neural state boundaries and perceived event boundaries overlap. Our results show that neural state boundaries are organized in a temporal cortical hierarchy, with short states in primary sensory regions, and long states in lateral and medial prefrontal cortex. State boundaries are shared within and between groups of brain regions that resemble well-known functional networks. Perceived event boundaries overlap with neural state boundaries across large parts of the cortical hierarchy, particularly when those state boundaries demarcate a strong transition or are shared between brain regions. Taken together, these findings suggest that a partially nested cortical hierarchy of neural states forms the basis of event segmentation. This article addresses the question of how the brain segments naturalistic events and the relationship between perceived event boundaries and neural pattern shifts. By applying an innovative analysis to a large, publicly available dataset, they observe evidence of different timescales of neural state shifts that correspond with perceived event bounds. These results will be of interest to cognitive neuroscientists investigating the relationship between neural states and event segmentation. Segmentation of information into meaningful units is a fundamental feature of our conscious experience in real-life contexts. Spatial information processing is characterized by segmenting spatial regions into objects e. In a similar way, temporal information processing is characterized by segmenting our ongoing experience into separate events Kurby and Zacks, ; Newtson et al. Segmentation improves our understanding of ongoing perceptual input Zacks et al.

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Many studies have identified the role of localized and distributed cognitive functionality by mapping either local task-related activity or distributed functional connectivity FC. However, few studies have directly explored the relationship between a brain region's localized task activity and its distributed task FC. Here we systematically evaluated the differential contributions of task-related activity and FC changes to identify a relationship between localized and distributed processes across the cortical hierarchy. We found that across multiple tasks, the magnitude of regional task-evoked activity was high in unimodal areas, but low in transmodal areas. In contrast, we found that task-state FC was significantly reduced in unimodal areas relative to transmodal areas.

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Cortical hierarchy

Federal government websites often end in. The site is secure. Preview improvements coming to the PMC website in October Learn More or Try it out now. Concepts shape the interpretation of facts. However, this concept has been interpreted in many different ways, which are not well aligned. This observation suggests that the concept is ill defined. Hierarchy is one of the most popular terms in current network and systems neuroscience. Failure to do so is bound to result in confusion.

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Figure 3 visualizes for each voxel which functional network label occurs most frequently for the searchlights overlapping that voxel. Nature , 78—84 The first row a-c shows the mean off-diagonal correlation: for a all activity, b shared activity, and c non-shared activity. Supply Chain Management. Public Administration. Asian Economics. Oral and Maxillofacial Surgery. By applying an innovative analysis to a large, publicly available dataset, they observe evidence of different timescales of neural state shifts that correspond with perceived event bounds. Art Forms. Key to the orchestration of behavior by neural systems is that information, in the form of neural activity, is reliably and accurately transmitted between anatomically distinct brain regions performing specialized tasks. Human Behaviour and the Social Environment. Instead, the cortical backprojections are used for gentle influences on earlier cortical stages, such as top-down attention, and memory recall if there is not a strong bottom-up input.

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In line with this hypothesis, we observed that neural state boundaries throughout the entire hierarchy overlap with perceived event boundaries, but this overlap is particularly strong for transmodal regions such as the dorsal medial prefrontal cortex, anterior cingulate cortex, left superior and middle frontal gyrus, and anterior insula. A simple view of the brain through a frequency-specific functional connectivity measure. Fixating the eyes would result in a very unnatural mode of information processing which might bias neural activity in very different ways. Social Psychology. Computer Architecture and Logic Design. Mante, V. Descending projections from the auditory cortex to the inferior colliculus in the gerbil, Meriones unguiculatus. Cardiothoracic Surgery. Molecular and Cell Biology. Thus, we developed a preparation in which activity that causally drives behavior can be recorded, with single-cell resolution, both locally and after propagation downstream.