scholarly journals Top-Down Feedback Controls Spatial Summation and Response Gain in Primate Visual Cortex

2016 ◽  
Author(s):  
Lauri Nurminen ◽  
Sam Merlin ◽  
Maryam Bijanzadeh ◽  
Frederick Federer ◽  
Alessandra Angelucci

ABSTRACTIn the cerebral cortex, sensory information travels along feedforward connections through a hierarchy of areas, which, in turn, send a denser network of feedback connections to lower-order areas. Feedback has been implicated in attention, expectation, and sensory context, but the cellular mechanisms underlying these diverse feedback functions are unknown. Using specific optogenetic inactivation of feedback connections in the primate visual cortex, we have identified the cellular mechanisms of feedback-mediated modulations of early sensory processing. Specifically, we found that feedback modulates receptive field size, surround suppression and response gain, similar to the modulatory effects of visual spatial attention. A recurrent network model captured these effects. These feedback-mediated modulations allow higher-order cortical areas to dynamically regulate spatial resolution, sensitivity to image features, and efficiency of coding natural images in lower-order cortical areas.

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Caitlin Siu ◽  
Justin Balsor ◽  
Sam Merlin ◽  
Frederick Federer ◽  
Alessandra Angelucci

AbstractThe mammalian sensory neocortex consists of hierarchically organized areas reciprocally connected via feedforward (FF) and feedback (FB) circuits. Several theories of hierarchical computation ascribe the bulk of the computational work of the cortex to looped FF-FB circuits between pairs of cortical areas. However, whether such corticocortical loops exist remains unclear. In higher mammals, individual FF-projection neurons send afferents almost exclusively to a single higher-level area. However, it is unclear whether FB-projection neurons show similar area-specificity, and whether they influence FF-projection neurons directly or indirectly. Using viral-mediated monosynaptic circuit tracing in macaque primary visual cortex (V1), we show that V1 neurons sending FF projections to area V2 receive monosynaptic FB inputs from V2, but not other V1-projecting areas. We also find monosynaptic FB-to-FB neuron contacts as a second motif of FB connectivity. Our results support the existence of FF-FB loops in primate cortex, and suggest that FB can rapidly and selectively influence the activity of incoming FF signals.


2018 ◽  
Vol 9 (1) ◽  
Author(s):  
Lauri Nurminen ◽  
Sam Merlin ◽  
Maryam Bijanzadeh ◽  
Frederick Federer ◽  
Alessandra Angelucci

Author(s):  
Caitlin Siu ◽  
Justin Balsor ◽  
Frederick Federer ◽  
Alessandra Angelucci

Abstract The mammalian sensory neocortex consists of hierarchically organized areas reciprocally connected via feedforward (FF) and feedback (FB) circuits. Several theories of hierarchical computation ascribe the bulk of the computational work of the cortex to looped FF-FB circuits between pairs of cortical areas. However, whether such corticocortical loops exist remains unclear. In higher mammals, FF projections send afferents almost exclusively to a single higher-level area. However, it is unclear whether FB projections show similar area-specificity, and whether they influence FF-projection neurons directly or indirectly. Using viral-mediated monosynaptic circuit tracing in macaque visual cortex, we find that neurons sending FF projections to a higher-level area receive monosynaptic FB inputs exclusively from that area. We also find monosynaptic FB-to-FB neuron contacts as a second motif of FB connectivity. Our results support the existence of FF-FB loops in primate cortex, and suggest that FB can rapidly and selectively influence the activity of incoming FF signals.


Author(s):  
Caitlin Siu ◽  
Justin Balsor ◽  
Frederick Federer ◽  
Alessandra Angelucci

ABSTRACTThe mammalian sensory neocortex consists of hierarchically organized areas reciprocally connected via feedforward (FF) and feedback (FB) circuits. Several theories of hierarchical computation ascribe the bulk of the computational work of the cortex to looped FF-FB circuits between pairs of cortical areas. However, whether such corticocortical loops exist remains unclear. In higher mammals, FF projections send afferents almost exclusively to a single higher-level area. However, it is unclear whether FB projections show similar area-specificity, and whether they influence FF-projection neurons directly or indirectly. Using viral-mediated monosynaptic circuit tracing in macaque visual cortex, we find that neurons sending FF projections to a higher-level area receive monosynaptic FB inputs exclusively from that area. We also find monosynaptic FB-to-FB neuron contacts as a second motif of FB connectivity. Our results support the existence of FF-FB loops in primate cortex, and suggest that FB can rapidly and selectively influence the activity of incoming FF signals.


2021 ◽  
pp. 1-14
Author(s):  
Jie Huang ◽  
Paul Beach ◽  
Andrea Bozoki ◽  
David C. Zhu

Background: Postmortem studies of brains with Alzheimer’s disease (AD) not only find amyloid-beta (Aβ) and neurofibrillary tangles (NFT) in the visual cortex, but also reveal temporally sequential changes in AD pathology from higher-order association areas to lower-order areas and then primary visual area (V1) with disease progression. Objective: This study investigated the effect of AD severity on visual functional network. Methods: Eight severe AD (SAD) patients, 11 mild/moderate AD (MAD), and 26 healthy senior (HS) controls undertook a resting-state fMRI (rs-fMRI) and a task fMRI of viewing face photos. A resting-state visual functional connectivity (FC) network and a face-evoked visual-processing network were identified for each group. Results: For the HS, the identified group-mean face-evoked visual-processing network in the ventral pathway started from V1 and ended within the fusiform gyrus. In contrast, the resting-state visual FC network was mainly confined within the visual cortex. AD disrupted these two functional networks in a similar severity dependent manner: the more severe the cognitive impairment, the greater reduction in network connectivity. For the face-evoked visual-processing network, MAD disrupted and reduced activation mainly in the higher-order visual association areas, with SAD further disrupting and reducing activation in the lower-order areas. Conclusion: These findings provide a functional corollary to the canonical view of the temporally sequential advancement of AD pathology through visual cortical areas. The association of the disruption of functional networks, especially the face-evoked visual-processing network, with AD severity suggests a potential predictor or biomarker of AD progression.


2014 ◽  
Vol 34 (22) ◽  
pp. 7575-7579 ◽  
Author(s):  
S. Huang ◽  
C. Rozas ◽  
M. Trevino ◽  
J. Contreras ◽  
S. Yang ◽  
...  

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