Evidence for a Functional Hierarchy of Association Networks

Abstract

Patient lesion and neuroimaging studies have identified a rostral-to-caudal functional gradient in the lateral frontal cortex (LFC) corresponding to higher-order (complex or abstract) to lower-order (simple or concrete) cognitive control. At the same time, monkey anatomical and human functional connectivity studies show that frontal regions are reciprocally connected with parietal and temporal regions, forming parallel and distributed association networks. Here, we investigated the link between the functional gradient of LFC regions observed during control tasks and the parallel, distributed organization of association networks. Whole-brain fMRI task activity corresponding to four orders of hierarchical control [Badre, D., & D'Esposito, M. Functional magnetic resonance imaging evidence for a hierarchical organization of the prefrontal cortex. Journal of Cognitive Neuroscience, 19, 2082-2099, 2007] was compared with a resting-state functional connectivity MRI estimate of cortical networks [Yeo, B. T., Krienen, F. M., Sepulcre, J., Sabuncu, M. R., Lashkari, D., Hollinshead, M., et al. The organization of the human cerebral cortex estimated by intrinsic functional connectivity. Journal of Neurophysiology, 106, 1125-1165, 2011]. Critically, at each order of control, activity in the LFC and parietal cortex overlapped onto a common association network that differed between orders. These results are consistent with a functional organization based on separable association networks that are recruited during hierarchical control. Furthermore, corticostriatal functional connectivity MRI showed that, consistent with their participation in functional networks, rostral-to-caudal LFC and caudal-to-rostral parietal regions had similar, order-specific corticostriatal connectivity that agreed with a striatal gating model of hierarchical rule use. Our results indicate that hierarchical cognitive control is subserved by parallel and distributed association networks, together forming multiple localized functional gradients in different parts of association cortex. As such, association networks, while connectionally organized in parallel, may be functionally organized in a hierarchy via dynamic interaction with the striatum.

Integrative Frontal-Parietal Dynamics Supporting Cognitive Control

“…In the lateral PFC, activations progressed in a caudal to rostral fashion as a function of abstraction of cognitive control from sensory-motor control, to contextual control, to temporal control 25,26 . In the PPC, activations progressed in a rostral to caudo-lateral fashion as a function of abstraction of cognitive control 27 . That is, in both the lateral PFC and PPC, increasingly abstract control was associated with activations increasingly distant from sensory-motor cortices of the pre/post-central gyri.…”

Traveling cortical netwaves compose a mindstream

“…The cognitive demands of the paradigm used here are poor. It is a compelling question as to which vectors will represent the sophisticated reflecting task positive brain, as in chess-playing paradigms, where you would expect even simple vector-sets running along the hierarchical-functional gradients described within the default mode network 41 , within the three networks dorsal attention, executive control and default 51 or over the rostral-caudal gradient in the lateral frontal cortex 48 .…”

“…The dorsal attention network 37,45,47,48,51,[54][55][56][57] , including Spreng 51 's nodes MT, SOG, SPL, FEF and daCC (see tab. II), follows parietal and ultimately the medial-precentral part of the sensory motor network 55 originates with the latter.…”

“…The executive control network is positioned between default mode and attention 51 . A hierarchical (rostro-caudal and caudal-rostral) order also exists within the prefrontal networks 48 i -The ventral stream of the human extrastriate visual cortex shows a considerable functional heterogeneity from early visual processing (posterior) to higher, domain-specific processing (anterior) 68 . This stream comprises an ascending hierarchy with the sequence VI -V2 (V3) -V4inferior temporal cortex (IT), starting with simpler features posteriorly (TEO/PIT) that increase in complexity as processing moves anteriorly (TE/AIT) to perform object recognition 69 .…”

“…Examples of the architecture of a traveling netwave.i -Contrast of delayed and speeded responses, phase images. The unique hierarchical position of the complex made of the parietal Brodmann area 7, a core area of the dorsal attention network37,45,47,48,51,[54][55][56][57] , becomes clear in contrast imaging of speeded and delayed-response tasks. The speeded responses (the right-hand phase images) activate all of the same regions as the delayed responses (the visual phase image on the left, next to it both motor phase images)with the exception of the high-association superior parietal regions (precuneus and parietalis superior, BA 7, pink rings).…”