Inter-areal Balanced Amplification Enhances Signal Propagation in a Large-Scale Circuit Model of the Primate Cortex

Abstract

Understanding reliable signal transmission represents a notable challenge for cortical systems, which display a wide range of weights of feedforward and feedback connections among heterogeneous areas. We re-examine the question of signal transmission across the cortex in a network model based on mesoscopic directed and weighted inter-areal connectivity data of the macaque cortex. Our findings reveal that, in contrast to purely feedforward propagation models, the presence of long-range excitatory feedback projections could compromise stable signal propagation. Using population rate models as well as a spiking network model, we find that effective signal propagation can be accomplished by balanced amplification across cortical areas while ensuring dynamical stability. Moreover, the activation of prefrontal cortex in our model requires the input strength to exceed a threshold, which is consistent with the ignition model of conscious processing. These findings demonstrate our model as an anatomically realistic platform for investigations of global primate cortex dynamics.

Hierarchical disruption in the cortex of anesthetized monkeys as a new signature of consciousness loss

“…Therefore, in order to link intrinsic ignition and mechanistic models, large scale models (Breakspear, 2017) are expected as future steps to give light on part of the neuronal mechanisms involved. It may help to connect our results with other studies on sleep (Jobst et al, 2017) and disorders of consciousness, as well as the simulation and exploration of manipulated brain states using deep brain stimulation (Saenger et al, 2017).…”

Canonical and noncanonical features of the mouse visual cortical hierarchy

“…The existence of such pairs of areas appears to contradict the “no-strong-loops hypothesis”, which proposes that looped interareal circuits comprising only strong, ‘driving’ connections do not exist as they would result in a positive feedback loop resulting in uncontrolled excitation across areas 51 . Possible mechanisms to avoid runaway, epileptic excitation within such ‘strong loops’ involve the differential engagement of inhibition by different pathways 21,37,52 , as well as through dynamically changing, differential levels of input strengths across layers depending on context and visual salience. The latter mechanism can be formalized in the posterior parietal cortex 24 as a coordinate transformation 53 , a process in which one functionally specialized coordinate frame is transformed to another depending on the sensorimotor function that needs to be achieved 54 .…”

Cortical ignition dynamics is tightly linked to the core organisation of the human connectome

“…to a reverberation of enhanced activation followed by propagation toward neighbouring regions [18,19]. Recently, mean-field whole-brain models able to reproduce in certain conditions such as propagation of ignition, thanks to a balanced amplification mechanism, have been introduced [22].…”

“…Growing experimental [18] and modelling [22] evidence stress how cortical ignition is non-linear in nature, with regions able to get ignited only if the inputs they receive -external, but also, notably, recurrent-rise above a minimum threshold. Whether this threshold is crossed or not depends on a variety of factors such as the number of neighbouring regions and the strength of incoming connections but also the simultaneous activity state of the neighbouring regions themselves [20], influenced on its turn by the network collective state.…”