Cortical hierarchy

Hierarchical cortical organization is found in all sensory systems, in the reward system, and in the memory systems.

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.

Cortical hierarchy

Thank you for visiting nature. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser or turn off compatibility mode in Internet Explorer. In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript. Brains are composed of anatomically and functionally distinct regions performing specialized tasks, but regions do not operate in isolation. Orchestration of complex behaviors requires communication between brain regions, but how neural dynamics are organized to facilitate reliable transmission is not well understood. Here we studied this process directly by generating neural activity that propagates between brain regions and drives behavior, assessing how neural populations in sensory cortex cooperate to transmit information. We achieved this by imaging two densely interconnected regions—the primary and secondary somatosensory cortex S1 and S2 —in mice while performing two-photon photostimulation of S1 neurons and assigning behavioral salience to the photostimulation. We found that the probability of perception is determined not only by the strength of the photostimulation but also by the variability of S1 neural activity. Therefore, maximizing the signal-to-noise ratio of the stimulus representation in cortex relative to the noise or variability is critical to facilitate activity propagation and perception. 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. Activity is transformed at each stage of its journey, and circuits often perform multiple tasks in parallel 1 , 2 , so it is challenging to disambiguate which facets of neural activity contribute to a specific behavior or process.

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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. This revealed a strong negative relationship between localized task activity and distributed FC across cortical regions that was associated with the previously reported principal gradient of macroscale organization. Moreover, this dissociation corresponded to hierarchical cortical differences in the intrinsic timescale estimated from resting-state fMRI and region myelin content estimated from structural MRI.

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Cortical hierarchy

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Tarneit house and land

A non-canonical feedback circuit for rapid interactions between somatosensory cortices. The methods section describing the analysis is not entirely clear. Business and the Environment. Theoretical work has also highlighted the potential role of feedback connections in information processing 62 , 63 , and it is known that S2 also projects back to S1 directly and indirectly 31 , Each volume contained 32 axial slices acquired in descending order , with slice thickness of 3. A The estimates of the HRF peak delays for all searchlights are shown in a histogram. This was observed particularly in the middle and superior temporal gyri, extending into the inferior frontal gyrus see Figure 2C , but also in the precuneus and medial prefrontal cortex. USA , — This shows that neural activity underpinning perceived stimulation persisted both locally in S1 and downstream in S2 for several seconds. Cortex 4, 78—

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We found a clear correlation between the fraction of excited and inhibited cells for both hit and miss trials in S1 and S2 Fig. Grosso, A. We now also discuss much more extensively what our findings can tell us about the mechanisms underlying event segmentation in both the introduction and Discussion sections. King, A. This divergence was supported by the overall limited similarity with the previously identified networks by Power et al. In contrast, the population variance across S1 neurons strongly predicted whether the upcoming stimulus would be a hit or a miss trial. This reveals an organizing principle of the cortex that explains how inhibition-stabilized circuits can remain susceptible to behaviorally relevant stimuli. Biological and Medical Physics. Computer Architecture and Logic Design. Wolff, S.