Stimulus-driven competition in a cholinergic midbrain nucleus

Asadollahi, Ali; Mysore, Shreesh P.; Knudsen, Eric I.

doi:10.1038/nn.2573

Cited by 65 publications

(78 citation statements)

References 39 publications

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“…This result suggests a mechanism that suppresses goal-irrelevant visual inputs in SCi to prioritize which salient signals gain access to the downstream gaze control system. Taken together, these results support a simple, intuitive framework for the formation of the saliency map in the primate midbrain, echoing earlier studies in the premammalian optic tectum (16)(17)(18).…”

Section: Discussionsupporting

confidence: 86%

“…Certainly, it would seem advantageous for primitive species to have a mechanism that allows one to rapidly engage the orienting system toward stimuli defined by conspicuous features, and the evolutionarily old visual system in the midbrain seems to have solved this biological problem long before the elaboration of visual cortex (16)(17)(18). A potential functional advantage of a saliency mechanism in SC is that it would reside close to the gaze-orienting circuity.…”

Section: Discussionmentioning

confidence: 99%

“…To date, most studies have reported evidence of saliency and/or priority maps in a distributed network of cortical brain areas [e.g., primary visual cortex (V1) (6)(7)(8)(9), visual area 4 (V4) (10), lateral intraparietal area (LIP) (11)(12)(13), and frontal eye fields (14,15)]. However, there is mounting evidence for a subcortical saliency mechanism in the premammalian optic tectum (16)(17)(18) or superior colliculus (SC) in primates (Fig. 1B).…”

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confidence: 99%

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Superior colliculus encodes visual saliency before the primary visual cortex

White

Kan

Lévy

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

114

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Models of visual attention postulate the existence of a bottom-up saliency map that is formed early in the visual processing stream. Although studies have reported evidence of a saliency map in various cortical brain areas, determining the contribution of phylogenetically older pathways is crucial to understanding its origin. Here, we compared saliency coding from neurons in two early gateways into the visual system: the primary visual cortex (V1) and the evolutionarily older superior colliculus (SC). We found that, while the response latency to visual stimulus onset was earlier for V1 neurons than superior colliculus superficial visual-layer neurons (SCs), the saliency representation emerged earlier in SCs than in V1. Because the dominant input to the SCs arises from V1, these relative timings are consistent with the hypothesis that SCs neurons pool the inputs from multiple V1 neurons to form a feature-agnostic saliency map, which may then be relayed to other brain areas.M ost theories and computational models of saliency postulate that visual input is transformed into a topographic representation of visual conspicuity (Fig. 1A, red), whereby certain stimuli stand out from others based on low-level features of the input image (Fig. 1A, blue) (1-3). The concept of a priority map describes a combined representation of visual saliency and behavioral relevancy (Fig. 1A, yellow), which is thought to be the core determinant of attention and gaze (4, 5). To date, most studies have reported evidence of saliency and/or priority maps in a distributed network of cortical brain areas [e.g., primary visual cortex (V1) (6-9), visual area 4 (V4) (10), lateral intraparietal area (LIP) (11-13), and frontal eye fields (14, 15)]. However, there is mounting evidence for a subcortical saliency mechanism in the premammalian optic tectum (16-18) or superior colliculus (SC) in primates (Fig. 1B). The primate SC, which has received a lot of attention for its role as an oculomotor hub, might be considered an unlikely candidate for a visual salience map, but there is a rich history of research on visual attention in the SC (a recent review is in ref. 19), which has broadened our perspective of its role in processes previously thought to be the domain of neocortex.The SC (Fig. 1B) is multilayered but is often described as having two dominant functional layers, a superior colliculus superficial layer (SCs) associated exclusively with visual processing and a superior colliculus multisensory-cognitive-motor intermediate layer (SCi) linked to the control of attention and gaze (19)(20)(21)(22). Because SCs is interconnected with multiple visual areas (23-25), it is in an ideal location to pool diverse visual inputs to form a feature-agnostic saliency representation. Recently (26), it has been shown that the activity of SCs neurons, with dominant inputs that arise from the retina and V1 (Fig. 1B) (24, 25), is well-predicted by a computational saliency model that has been validated on the free viewing behavior of humans (27) and nonhuman prima...

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Section: Discussionsupporting

confidence: 86%

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

See 1 more Smart Citation

Superior colliculus encodes visual saliency before the primary visual cortex

White

Kan

Lévy

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

114

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“…This suppression operates even for stimuli located far from the RF center, at distances up to 90 deg of visual angle (Asadollahi et al, 2010(Asadollahi et al, , 2011. We repeated this experiment during simultaneous recordings of the Ipc and SLu, finding that when a second moving spot was presented while the first stimulus was in the middle of its trajectory, the responses recorded in both nuclei were simultaneously suppressed.…”

Section: Simultaneous Recording In the Ipc And Slumentioning

confidence: 91%

“…Here, we describe feedback signals from the isthmic region to the optic tectum (TeO) of the pigeon that selectively boost the propagation of visual inputs from selected tectal locations to higher visual areas. Because the feedback signal's location in the tectal visual map is controlled by suppressive interactions (Marín et al, 2007, Asadollahi et al, 2010, only the strongest visual inputs reach higher brain areas.…”

Section: Introductionmentioning

confidence: 99%

Attentional Capture? Synchronized Feedback Signals from the Isthmi Boost Retinal Signals to Higher Visual Areas

Marı́n

Durán²,

Morales³

et al. 2012

J. Neurosci.

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When a salient object in the visual field captures attention, the neural representation of that object is enhanced at the expense of competing stimuli. How neural activity evoked by a salient stimulus evolves to take precedence over the neural activity evoked by other stimuli is a matter of intensive investigation. Here, we describe in pigeons (Columba livia) how retinal inputs to the optic tectum (TeO, superior colliculus in mammals), triggered by moving stimuli, are selectively relayed on to the rotundus (Rt, caudal pulvinar) in the thalamus, and to its pallial target, the entopallium (E, extrastriate cortex). We show that two satellite nuclei of the TeO, the nucleus isthmi parvocelullaris (Ipc) and isthmi semilunaris (SLu), send synchronized feedback signals across tectal layers. Preventing the feedback from Ipc but not from SLu to a tectal location suppresses visual responses to moving stimuli from the corresponding region of visual space in all Rt subdivisions. In addition, the bursting feedback from the Ipc imprints a bursting rhythm on the visual signals, such that the visual responses of the Rt and the E acquire a bursting modulation significantly synchronized to the feedback from Ipc. As the Ipc feedback signals are selected by competitive interactions, the visual responses within the receptive fields in the Rt tend to synchronize with the tectal location receiving the "winning" feedback from Ipc. We propose that this selective transmission of afferent activity combined with the cross-regional synchronization of the areas involved represents a bottom-up mechanism by which salient stimuli capture attention.

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Controlling glycation of recombinant antibody in fed‐batch cell cultures

Yuk¹,

Zhang²,

Yang³

et al. 2011

Biotech & Bioengineering

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Protein glycation is a non-enzymatic glycosylation that can occur to proteins in the human body, and it is implicated in the pathogenesis of multiple chronic diseases. Glycation can also occur to recombinant antibodies during cell culture, which generates structural heterogeneity in the product. In a previous study, we discovered unusually high levels of glycation (>50%) in a recombinant monoclonal antibody (rhuMAb) produced by CHO cells. Prior to that discovery, we had not encountered such high levels of glycation in other in-house therapeutic antibodies. Our goal here is to develop cell culture strategies to decrease rhuMAb glycation in a reliable, reproducible, and scalable manner. Because glycation is a post-translational chemical reaction between a reducing sugar and a protein amine group, we hypothesized that lowering the concentration of glucose--the only source of reducing sugar in our fed-batch cultures--would lower the extent of rhuMAb glycation. When we decreased the supply of glucose to bioreactors from bolus nutrient and glucose feeds, rhuMAb glycation decreased to below 20% at both 2-L and 400-L scales. When we maintained glucose concentrations at lower levels in bioreactors with continuous feeds, we could further decrease rhuMAb glycation levels to below 10%. These results show that we can control glycation of secreted proteins by controlling the glucose concentration in the cell culture. In addition, our data suggest that rhuMAb glycation occurring during the cell culture process may be approximated as a second-order chemical reaction that is first order with respect to both glucose and non-glycated rhuMAb. The basic principles of this glycation model should apply to other recombinant proteins secreted during cell culture.

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Stimulus-driven competition in a cholinergic midbrain nucleus

Cited by 65 publications

References 39 publications

Superior colliculus encodes visual saliency before the primary visual cortex

Superior colliculus encodes visual saliency before the primary visual cortex

Attentional Capture? Synchronized Feedback Signals from the Isthmi Boost Retinal Signals to Higher Visual Areas

Controlling glycation of recombinant antibody in fed‐batch cell cultures

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