Attention is critical to perception, serving to select behaviorally relevant information for privileged processing. To understand the neural mechanisms of attention, we must discern how attentional ...modulation varies by cell type and across cortical layers. Here, we test whether attention acts non-selectively across cortical layers or whether it engages the laminar circuit in specific and selective ways. We find layer- and cell-class-specific differences in several different forms of attentional modulation in area V4. Broad-spiking neurons in the superficial layers exhibit attention-mediated increases in firing rate and decreases in variability. Spike count correlations are highest in the input layer and attention serves to reduce these correlations. Superficial and input layer neurons exhibit attention-dependent decreases in low-frequency (<10 Hz) coherence, but deep layer neurons exhibit increases in coherence in the beta and gamma frequency ranges. Our study provides a template for attention-mediated laminar information processing that might be applicable across sensory modalities.
•Attention engages the V4 laminar circuit in selective ways•Superficial broad-spiking cells show increased rate and reliability with attention•Low-frequency coherence decreases with attention in superficial and input layers•Correlations in V4 are highest in the input layer
Attention is a critical component of perception. Here, Nandy et al. examine the laminar organization of attentional modulation in sensory cortex. They find layer- and cell-class-specific differences in the laminar cortical circuit in area V4.
The Fine Structure of Shape Tuning in Area V4 Nandy, Anirvan S.; Sharpee, Tatyana O.; Reynolds, John H. ...
Neuron (Cambridge, Mass.),
06/2013, Letnik:
78, Številka:
6
Journal Article
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Previous studies have shown that neurons in area V4 are involved in the processing of shapes of intermediate complexity and are sensitive to curvature. These studies also suggest that curvature-tuned ...neurons are position invariant. We sought to examine the mechanisms that endow V4 neurons with these properties. Consistent with previous studies, we found that response rank order to the most- and least-preferred stimuli was preserved throughout the receptive field. However, a fine-grained analysis of shape tuning revealed a surprising result: V4 neurons tuned to highly curved shapes exhibit very limited translation invariance. At a fine spatial scale, these neurons exhibit local variation in orientation. In contrast, neurons that prefer straight contours exhibit spatially invariant orientation-tuning and homogenous fine-scale orientation maps. Both of these patterns are consistent with a simple orientation-pooling model, with tuning for straight or curved shapes resulting, respectively, from pooling of homogenous or heterogeneous orientation signals inherited from early visual areas.
•Organization of V4 receptive fields using dual-scale reverse correlation•Curvature-tuned cells show limited spatial invariance and heterogenous fine-scale maps•Straight-tuned cells exhibit spatial invariance and homogenous fine-scale maps•Simple local pooling of fine-scale orientation signals explains contour tuning
Nandy et al. investigate the detailed microstructure of receptive fields in macaque V4, an area important for shape perception. They find a trade-off between tuning complexity and translation invariance and describe a simple model to account for this trade-off.
The central region of the human retina, the fovea, provides high-acuity vision. The oculomotor system continually brings targets of interest into the fovea via ballistic eye movements (saccades). ...Thus, the fovea serves both as the locus for fixations and as the oculomotor reference for saccades. This highly automated process of foveation is functionally critical to vision and is observed from infancy 1, 2. How would the oculomotor system adjust to a loss of foveal vision (central scotoma)? Clinical observations of patients with central vision loss 3, 4 suggest a lengthy adjustment period 5, but the nature and dynamics of this adjustment remain unclear. Here, we demonstrate that the oculomotor system can spontaneously and rapidly adopt a peripheral locus for fixation and can rereference saccades to this locus in normally sighted individuals whose central vision is blocked by an artificial scotoma. Once developed, the fixation locus is retained over weeks in the absence of the simulated scotoma. Our data reveal a basic guiding principle of the oculomotor system that prefers control simplicity over optimality. We demonstrate the importance of a visible scotoma on the speed of the adjustment and suggest a possible rehabilitation regimen for patients with central vision loss.
•Fast (∼hours) emergence of eccentric fixation locus following occluded central vision•Rapid rereferencing of saccades to the eccentric fixation locus•Learned oculomotor plan is retained for weeks with normal (unoccluded) central vision
Attention selectively enhances neural responses to low contrast stimuli in visual area V4, a critical hub that sends projections both up and down the visual hierarchy. Veridical encoding of contrast ...information is a key computation in early visual areas, while later stages encoding higher level features benefit from improved sensitivity to low contrast. How area V4 meets these distinct information processing demands in the attentive state is unknown. We found that attentional modulation in V4 is cortical layer and cell-class specific. Putative excitatory neurons in the superficial layers show enhanced boosting of low contrast information, while those of deep layers exhibit contrast-independent scaling. Computational modeling suggested the extent of spatial integration of inhibitory neurons as the mechanism behind such laminar differences. Considering that superficial neurons are known to project to higher areas and deep layers to early visual areas, our findings suggest that the interactions between attention and contrast in V4 are compartmentalized, in alignment with the demands of the visual processing hierarchy.
Abstract Spatial attention is critical for recognizing behaviorally relevant objects in a cluttered environment. How the deployment of spatial attention aids the hierarchical computations of object ...recognition remains unclear. We investigated this in the laminar cortical network of visual area V4, an area strongly modulated by attention. We found that deployment of attention strengthened unique dependencies in neural activity across cortical layers. On the other hand, shared dependencies were reduced within the excitatory population of a layer. Surprisingly, attention strengthened unique dependencies within a laminar population. Crucially, these modulation patterns were also observed during successful behavioral outcomes that are thought to be mediated by internal brain state fluctuations. Successful behavioral outcomes were also associated with phases of reduced neural excitability, suggesting a mechanism for enhanced information transfer during optimal states. Our results suggest common computation goals of optimal sensory states that are attained by either task demands or internal fluctuations.
Processing of shape information in human peripheral visual fields is impeded beyond what can be expected by poor spatial resolution. Visual crowding, the inability to identify objects in clutter, has ...been shown to be the primary factor limiting shape perception in peripheral vision. Despite the well-documented effects of crowding, its underlying causes remain poorly understood. Given that spatial attention both facilitates learning of image statistics and directs saccadic eye movements, we propose that the acquisition of image statistics in peripheral visual fields is confounded by eye-movement artifacts. Specifically, the image statistics acquired under a peripherally deployed spotlight of attention are systematically biased by saccade-induced image displacements. These erroneously represented image statistics lead to inappropriate contextual interactions in the periphery and cause crowding.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Very little is known about the neural circuitry guiding anger, angry rumination, and aggressive personality. In the present fMRI experiment, participants were insulted and induced to ruminate. ...Activity in the dorsal anterior cingulate cortex was positively related to self-reported feelings of anger and individual differences in general aggression. Activity in the medial prefrontal cortex was related to self-reported rumination and individual differences in displaced aggression. Increased activation in the hippocampus, insula, and cingulate cortex following the provocation predicted subsequent self-reported rumination. These findings increase our understanding of the neural processes associated with the risk for aggressive behavior by specifying neural regions that mediate the subjective experience of anger and angry rumination as well as the neural pathways linked to different types of aggressive behavior.
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Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Saccadic eye movements are known to cause saccadic suppression, a temporary reduction in visual sensitivity and visual cortical firing rates. While saccadic suppression has been well characterized at ...the level of perception and single neurons, relatively little is known about the visual cortical networks governing this phenomenon. Here we examine the effects of saccadic suppression on distinct neural subpopulations within visual area V4. We find subpopulation-specific differences in the magnitude and timing of peri-saccadic modulation. Input-layer neurons show changes in firing rate and inter-neuronal correlations prior to saccade onset, and putative inhibitory interneurons in the input layer elevate their firing rate during saccades. A computational model of this circuit recapitulates our empirical observations and demonstrates that an input-layer-targeting pathway can initiate saccadic suppression by enhancing local inhibitory activity. Collectively, our results provide a mechanistic understanding of how eye movement signaling interacts with cortical circuitry to enforce visual stability.
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•Saccadic suppression is mediated by an input-layer-targeting pathway in area V4•Input-layer putative inhibitory neurons are facilitated during spontaneous saccades in dark•Input-layer-targeting pathway can initiate saccadic suppression via local inhibitory neurons•E-I network model operating at the cusp of ISN regime explains saccadic suppression
Denagamage et al. investigate peri-saccadic neural dynamics in the laminar cortical microcircuit of visual area V4 and uncover an input-layer-targeting pathway that mediates saccadic suppression via local inhibitory neurons. An E-I network model at the cusp of inhibition-stabilized network regime explains saccadic suppression.
•A decision-circuit model has traditionally explained the function of OFC.•A cognitive map model explains complex representations of task space in OFC.•Social and non-social functions of the OFC may ...be holistically explained.•OFC may represent a goal-directed cognitive map for social and non-social domains.
The orbitofrontal cortex (OFC) is regarded as one of the core brain areas in a variety of value-based behaviors. Over the past two decades, tremendous knowledge about the OFC function was gained from studying the behaviors of single subjects. As a result, our previous understanding of the OFC’s function of encoding decision variables, such as the value and identity of choices, has evolved to the idea that the OFC encodes a more complex representation of the task space as a cognitive map. Accumulating evidence also indicates that the OFC importantly contributes to behaviors in social contexts, especially those involved in cooperative interactions. However, it remains elusive how exactly OFC neurons contribute to social functions and how non-social and social behaviors are related to one another in the computations performed by OFC neurons. In this review, we aim to provide an integrated view of the OFC function across both social and non-social behavioral contexts. We propose that seemingly complex functions of the OFC may be explained by its role in providing a goal-directed cognitive map to guide a wide array of adaptive reward-based behaviors in both social and non-social domains.
To deepen our understanding of object recognition, it is critical to understand the nature of transformations that occur in intermediate stages of processing in the ventral visual pathway, such as ...area V4. Neurons in V4 are selective to local features of global shape, such as extended contours. Previously, we found that V4 neurons selective for curved elements exhibit a high degree of spatial variation in their preference. If spatial variation in curvature selectivity was also marked by distinct temporal response patterns at different spatial locations, then it might be possible to untangle this information in subsequent processing based on temporal responses. Indeed, we find that V4 neurons whose receptive fields exhibit intricate selectivity also show variation in their temporal responses across locations. A computational model that decodes stimulus identity based on population responses benefits from using this temporal information, suggesting that it could provide a multiplexed code for spatio-temporal features.
•V4 neurons show complex spatio-temporal tuning dynamics•Neurons with heterogeneous shape selectivity have diverse temporal response kernels•Population shape decoding models benefit from this temporal information•Temporal information could provide a multiplexed code for spatio-temporal features
Neurons in area V4 play a critical role in object recognition. Here, Nandy et al. show that V4 neurons exhibit variation in their temporal response profiles across spatial locations, suggesting a multiplexed code for spatio-temporal features.
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