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Floris P. De Lange - One of the best experts on this subject based on the ideXlab platform.

  • no evidence for altered up and downregulation of brain activity in visual cortex during illusory shape perception in autism
    Cortex, 2019
    Co-Authors: Christian Utzerath, Peter Kok, Iris C Schmits, Jan K Buitelaar, Floris P. De Lange
    Abstract:

    Autism spectrum disorder (ASD) may be marked by an altered balance between sensory input and prior expectations. Because many illusions rely on integrating sensory input with prior information such as spatial context, individuals with ASD may therefore be less susceptible to visual illusions than typically developing (TD) individuals. Yet empirical evidence on the matter is rather divergent, varying depending on the type of illusion, study procedure, and population. Visual illusions lead to neural activity alterations in the visual system. In the so-called Kanizsa illusion, these are likely caused by Top-Down Feedback to V1. Here we tested the hypothesis that a reduced susceptibility to illusions in ASD would manifest as diminished modulation of V1 activity by illusions, using functional magnetic resonance imaging (fMRI). We presented 22 adolescents with ASD and 22 age-, gender-, and intelligence-matched TD controls with displays that consisted of three circular inducers. These either formed an illusory triangle (Kanizsa illusion) or not. We identified regions in primary visual cortex (V1) that corresponded to (the visual field locations of) the illusory triangle and its inducers, and recorded their visual response. Previous research in healthy volunteers has shown a specific pattern of up- and down-regulation in regions of V1 that process the shape and inducers, respectively. Here, we replicated this pattern of up- and downregulation in V1, in both the TD and ASD groups, with no differences between groups. This suggests that illusory shape processing in primary visual cortex is equally present in ASD, suggesting unimpaired processing of spatial context.

  • selective activation of the deep layers of the human primary visual cortex by top down Feedback
    Current Biology, 2016
    Co-Authors: Peter Kok, Lauren J Bains, Tim Van Mourik, David G Norris, Floris P. De Lange
    Abstract:

    In addition to bottom-up input, the visual cortex receives large amounts of Feedback from other cortical areas [1, 2 and 3]. One compelling example of Feedback activation of early visual neurons in the absence of bottom-up input occurs during the famous Kanizsa illusion, where a triangular shape is perceived, even in regions of the image where there is no bottom-up visual evidence for it. This illusion increases the firing activity of neurons in the primary visual cortex with a receptive field on the illusory contour [4]. Feedback signals are largely segregated from feedforward signals within each cortical area, with feedforward signals arriving in the middle layer, while Top-Down Feedback avoids the middle layers and predominantly targets deep and superficial layers [1, 2, 5 and 6]. Therefore, the Feedback-mediated activity increase in V1 during the perception of illusory shapes should lead to a specific laminar activity profile that is distinct from the activity elicited by bottom-up stimulation. Here, we used fMRI at high field (7 T) to empirically test this hypothesis, by probing the cortical response to illusory figures in human V1 at different cortical depths [7, 8, 9, 10, 11, 12, 13 and 14]. We found that, whereas bottom-up stimulation activated all cortical layers, Feedback activity induced by illusory figures led to a selective activation of the deep layers of V1. These results demonstrate the potential for non-invasive recordings of neural activity with laminar specificity in humans and elucidate the role of Top-Down signals during perceptual processing.

  • shape perception simultaneously up and downregulates neural activity in the primary visual cortex
    Current Biology, 2014
    Co-Authors: Peter Kok, Floris P. De Lange
    Abstract:

    Donders Institute for Brain, Cognition and Behaviour,Radboud University Nijmegen, Kapittelweg 29, 6525 ENNijmegen, the NetherlandsSummaryAnessentialpartofvisualperceptionisthegroupingoflocalelements (such as edges and lines) into coherent shapes.Previous studies have shown that this grouping processmodulates neural activity in the primary visual cortex (V1)that is signaling the local elements [1–4]. However, thenature of this modulation is controversial. Some studiesfind that shape perception reduces neural activity in V1 [2,5, 6], while others report increased V1 activity during shapeperception [1, 3, 4, 7–10]. Neurocomputational theories thatcast perception as a generative process [11–13] proposethat Feedback connections carry predictions (i.e., the gener-ative model), while feedforward connections signal themismatch between Top-Down predictions and bottom-upinputs.Withinthisframework,theeffectofFeedbackonearlyvisual cortex may be either enhancing or suppressive, de-pendingonwhethertheFeedbacksignalismetbycongruentbottom-up input. Here, we tested this hypothesis by quanti-fying the spatial profile of neural activity in V1 during theperception of illusory shapes using population receptivefield mapping. We find that shape perception concurrentlyincreases neural activity in regions of V1 that have a recep-tive field on the shape but do not receive bottom-up inputand suppresses activity in regions of V1 that receivebottom-upinputthatispredictedbytheshape.Theseeffectswere not modulated by task requirements. Together, thesefindingssuggestthatshapeperceptionchangeslower-ordersensory representations in a highly specific and automaticmanner, in line with theories that cast perception in termsof hierarchical generative models.ResultsThe role of early visual regions during shape perception is illunderstood, with some studies reporting activity suppressiondue to grouping [2, 5, 6] while others report enhancement[1, 3, 4, 7–10]. According to theories that cast perception intermsofhierarchicalgenerativemodels[11–13],neuralactivityinlower-ordersensoryregionsisdependentbothonwhetheritisdrivenbysensorystimulationandwhetherthisstimulationispredicted on the basis of Top-Down Feedback signals. In thisframework, early visual neurons that do not receive anybottom-up input, but that are predicted to be active becausea shape is inferred at their receptive field location, are ex-pected to show relatively enhanced neural activity [3, 4, 8, 9].On the other hand, early visual neurons that receive bottom-up input that is congruent with the shape prediction are ex-pected to show a relatively suppressed response [2, 6, 14].Here, we directly test this framework within the context ofillusory shape perception.Illusory shape perception provides an ideal test bed, as theillusory shape results in both unexpected absence of visualinput (at the location where the shape is perceived but retinalinput is absent) and expected presence of visual input(at the location where the shape provides an explanation forthe bottom-up input). We made use of the well-known illusory‘‘Kanizsa’’ shapes [15], wherein circles with missing wedges(‘‘Pac-Man’’ inducers) are aligned such that they can inducethe perception of an illusory figure (Figure 1A). Using fMRIand population receptive field mapping [16], we quantifiedthe spatial profile of neural activity in early visual cortex whilesubjects (n = 20) were presented with stimuli that either did(Figure 1A) or did not (Figure 1B) induce an illusory figure.Moreover, to examine whether effects of shape perceptionwere dependent on attention, we manipulated the focus ofsubjects’ attention. In half of the trials, subjects had to detectthe presence of an occasional illusory diamond (‘‘figure task’’;Figure 1C), placing their attentional focus on the location ofthe illusory shapes. In the other half of the trials, subjectshadtodetecttwotargetletters(XandZ)inarapidlypresentedletter stream at fixation, drawing their attention away from theillusory shapes (‘‘letter task’’).Below, we present the spatially specific responses to thesestimuliinearlyvisualcortexintwodifferentways.First,weesti-mated the population receptive field (pRF) [16] of every voxelin early visual cortex (see Figures S1A–S1C and SupplementalExperimental Procedures available online) and used thisinformation to transform the blood oxygen-level-dependent(BOLD) signal into the reference frame of subjects’ visual fieldof view (Figure S1D; Supplemental Experimental Procedures).Second, we selected groups of voxels based on the locationof their receptive field and averaged over the BOLD signalmeasured in such voxels. In this way, we obtained separateestimates of neural activity in regions of primary visual cortex(V1) corresponding to the area of the visual field where theillusory triangles were presented (‘‘figure region’’) and regionscorresponding to the Pac-Man inducers (‘‘inducer region’’;seeSupplementalExperimentalProceduresfordetailsofvoxelselection).Theseanalysisstrategiesarecomplementary:whilethe first method allows for a characterization and visualizationof neural activity concurrently for all parts of visual space, thesecond approach is more standard and more easily allowsfor statistical quantification of the experimental effects.Reconstruction of Neural Response to Illusory FiguresWe reconstructed the neural response evoked by illusory fig-ures (Figure 1A), compared to control stimuli with the samelow-level features but that did not induce an illusory figure(Figure 1B). The results showed a striking spatial dissociation(Figure 2A): neural activity for regions of V1 that correspondedto the illusory figure (but not the Pac-Man inducers; figure re-gion) was enhanced when an illusory triangle was present,compared to when the inducers did not form an illusory figure(Figure3A;p<0.001).Inotherwords,theseV1regionsshowedan increased response to the illusory figures, despite the

Peter Kok - One of the best experts on this subject based on the ideXlab platform.

  • no evidence for altered up and downregulation of brain activity in visual cortex during illusory shape perception in autism
    Cortex, 2019
    Co-Authors: Christian Utzerath, Peter Kok, Iris C Schmits, Jan K Buitelaar, Floris P. De Lange
    Abstract:

    Autism spectrum disorder (ASD) may be marked by an altered balance between sensory input and prior expectations. Because many illusions rely on integrating sensory input with prior information such as spatial context, individuals with ASD may therefore be less susceptible to visual illusions than typically developing (TD) individuals. Yet empirical evidence on the matter is rather divergent, varying depending on the type of illusion, study procedure, and population. Visual illusions lead to neural activity alterations in the visual system. In the so-called Kanizsa illusion, these are likely caused by Top-Down Feedback to V1. Here we tested the hypothesis that a reduced susceptibility to illusions in ASD would manifest as diminished modulation of V1 activity by illusions, using functional magnetic resonance imaging (fMRI). We presented 22 adolescents with ASD and 22 age-, gender-, and intelligence-matched TD controls with displays that consisted of three circular inducers. These either formed an illusory triangle (Kanizsa illusion) or not. We identified regions in primary visual cortex (V1) that corresponded to (the visual field locations of) the illusory triangle and its inducers, and recorded their visual response. Previous research in healthy volunteers has shown a specific pattern of up- and down-regulation in regions of V1 that process the shape and inducers, respectively. Here, we replicated this pattern of up- and downregulation in V1, in both the TD and ASD groups, with no differences between groups. This suggests that illusory shape processing in primary visual cortex is equally present in ASD, suggesting unimpaired processing of spatial context.

  • selective activation of the deep layers of the human primary visual cortex by top down Feedback
    Current Biology, 2016
    Co-Authors: Peter Kok, Lauren J Bains, Tim Van Mourik, David G Norris, Floris P. De Lange
    Abstract:

    In addition to bottom-up input, the visual cortex receives large amounts of Feedback from other cortical areas [1, 2 and 3]. One compelling example of Feedback activation of early visual neurons in the absence of bottom-up input occurs during the famous Kanizsa illusion, where a triangular shape is perceived, even in regions of the image where there is no bottom-up visual evidence for it. This illusion increases the firing activity of neurons in the primary visual cortex with a receptive field on the illusory contour [4]. Feedback signals are largely segregated from feedforward signals within each cortical area, with feedforward signals arriving in the middle layer, while Top-Down Feedback avoids the middle layers and predominantly targets deep and superficial layers [1, 2, 5 and 6]. Therefore, the Feedback-mediated activity increase in V1 during the perception of illusory shapes should lead to a specific laminar activity profile that is distinct from the activity elicited by bottom-up stimulation. Here, we used fMRI at high field (7 T) to empirically test this hypothesis, by probing the cortical response to illusory figures in human V1 at different cortical depths [7, 8, 9, 10, 11, 12, 13 and 14]. We found that, whereas bottom-up stimulation activated all cortical layers, Feedback activity induced by illusory figures led to a selective activation of the deep layers of V1. These results demonstrate the potential for non-invasive recordings of neural activity with laminar specificity in humans and elucidate the role of Top-Down signals during perceptual processing.

  • shape perception simultaneously up and downregulates neural activity in the primary visual cortex
    Current Biology, 2014
    Co-Authors: Peter Kok, Floris P. De Lange
    Abstract:

    Donders Institute for Brain, Cognition and Behaviour,Radboud University Nijmegen, Kapittelweg 29, 6525 ENNijmegen, the NetherlandsSummaryAnessentialpartofvisualperceptionisthegroupingoflocalelements (such as edges and lines) into coherent shapes.Previous studies have shown that this grouping processmodulates neural activity in the primary visual cortex (V1)that is signaling the local elements [1–4]. However, thenature of this modulation is controversial. Some studiesfind that shape perception reduces neural activity in V1 [2,5, 6], while others report increased V1 activity during shapeperception [1, 3, 4, 7–10]. Neurocomputational theories thatcast perception as a generative process [11–13] proposethat Feedback connections carry predictions (i.e., the gener-ative model), while feedforward connections signal themismatch between Top-Down predictions and bottom-upinputs.Withinthisframework,theeffectofFeedbackonearlyvisual cortex may be either enhancing or suppressive, de-pendingonwhethertheFeedbacksignalismetbycongruentbottom-up input. Here, we tested this hypothesis by quanti-fying the spatial profile of neural activity in V1 during theperception of illusory shapes using population receptivefield mapping. We find that shape perception concurrentlyincreases neural activity in regions of V1 that have a recep-tive field on the shape but do not receive bottom-up inputand suppresses activity in regions of V1 that receivebottom-upinputthatispredictedbytheshape.Theseeffectswere not modulated by task requirements. Together, thesefindingssuggestthatshapeperceptionchangeslower-ordersensory representations in a highly specific and automaticmanner, in line with theories that cast perception in termsof hierarchical generative models.ResultsThe role of early visual regions during shape perception is illunderstood, with some studies reporting activity suppressiondue to grouping [2, 5, 6] while others report enhancement[1, 3, 4, 7–10]. According to theories that cast perception intermsofhierarchicalgenerativemodels[11–13],neuralactivityinlower-ordersensoryregionsisdependentbothonwhetheritisdrivenbysensorystimulationandwhetherthisstimulationispredicted on the basis of Top-Down Feedback signals. In thisframework, early visual neurons that do not receive anybottom-up input, but that are predicted to be active becausea shape is inferred at their receptive field location, are ex-pected to show relatively enhanced neural activity [3, 4, 8, 9].On the other hand, early visual neurons that receive bottom-up input that is congruent with the shape prediction are ex-pected to show a relatively suppressed response [2, 6, 14].Here, we directly test this framework within the context ofillusory shape perception.Illusory shape perception provides an ideal test bed, as theillusory shape results in both unexpected absence of visualinput (at the location where the shape is perceived but retinalinput is absent) and expected presence of visual input(at the location where the shape provides an explanation forthe bottom-up input). We made use of the well-known illusory‘‘Kanizsa’’ shapes [15], wherein circles with missing wedges(‘‘Pac-Man’’ inducers) are aligned such that they can inducethe perception of an illusory figure (Figure 1A). Using fMRIand population receptive field mapping [16], we quantifiedthe spatial profile of neural activity in early visual cortex whilesubjects (n = 20) were presented with stimuli that either did(Figure 1A) or did not (Figure 1B) induce an illusory figure.Moreover, to examine whether effects of shape perceptionwere dependent on attention, we manipulated the focus ofsubjects’ attention. In half of the trials, subjects had to detectthe presence of an occasional illusory diamond (‘‘figure task’’;Figure 1C), placing their attentional focus on the location ofthe illusory shapes. In the other half of the trials, subjectshadtodetecttwotargetletters(XandZ)inarapidlypresentedletter stream at fixation, drawing their attention away from theillusory shapes (‘‘letter task’’).Below, we present the spatially specific responses to thesestimuliinearlyvisualcortexintwodifferentways.First,weesti-mated the population receptive field (pRF) [16] of every voxelin early visual cortex (see Figures S1A–S1C and SupplementalExperimental Procedures available online) and used thisinformation to transform the blood oxygen-level-dependent(BOLD) signal into the reference frame of subjects’ visual fieldof view (Figure S1D; Supplemental Experimental Procedures).Second, we selected groups of voxels based on the locationof their receptive field and averaged over the BOLD signalmeasured in such voxels. In this way, we obtained separateestimates of neural activity in regions of primary visual cortex(V1) corresponding to the area of the visual field where theillusory triangles were presented (‘‘figure region’’) and regionscorresponding to the Pac-Man inducers (‘‘inducer region’’;seeSupplementalExperimentalProceduresfordetailsofvoxelselection).Theseanalysisstrategiesarecomplementary:whilethe first method allows for a characterization and visualizationof neural activity concurrently for all parts of visual space, thesecond approach is more standard and more easily allowsfor statistical quantification of the experimental effects.Reconstruction of Neural Response to Illusory FiguresWe reconstructed the neural response evoked by illusory fig-ures (Figure 1A), compared to control stimuli with the samelow-level features but that did not induce an illusory figure(Figure 1B). The results showed a striking spatial dissociation(Figure 2A): neural activity for regions of V1 that correspondedto the illusory figure (but not the Pac-Man inducers; figure re-gion) was enhanced when an illusory triangle was present,compared to when the inducers did not form an illusory figure(Figure3A;p<0.001).Inotherwords,theseV1regionsshowedan increased response to the illusory figures, despite the

Shihab A Shamma - One of the best experts on this subject based on the ideXlab platform.

  • laminar profile of task related plasticity in ferret primary auditory cortex
    Scientific Reports, 2018
    Co-Authors: Nikolas A Francis, Diego Elgueda, Bernhard Englitz, Jonathan B Fritz, Shihab A Shamma
    Abstract:

    Rapid task-related plasticity is a neural correlate of selective attention in primary auditory cortex (A1). Top-Down Feedback from higher-order cortex may drive task-related plasticity in A1, characterized by enhanced neural representation of behaviorally meaningful sounds during auditory task performance. Since intracortical connectivity is greater within A1 layers 2/3 (L2/3) than in layers 4–6 (L4–6), we hypothesized that enhanced representation of behaviorally meaningful sounds might be greater in A1 L2/3 than L4–6. To test this hypothesis and study the laminar profile of task-related plasticity, we trained 2 ferrets to detect pure tones while we recorded laminar activity across a 1.8 mm depth in A1. In each experiment we analyzed high-gamma local field potentials (LFPs) and multi-unit spiking in response to identical acoustic stimuli during both passive listening and active task performance. We found that neural responses to auditory targets were enhanced during task performance, and target enhancement was greater in L2/3 than in L4–6. Spectrotemporal receptive fields (STRFs) computed from both high-gamma LFPs and multi-unit spiking showed similar increases in auditory target selectivity, also greatest in L2/3. Our results suggest that activity within intracortical networks plays a key role in the underlying neural mechanisms of selective attention.

  • laminar profile of task related plasticity in ferret primary auditory cortex
    bioRxiv, 2018
    Co-Authors: Nikolas A Francis, Diego Elgueda, Bernhard Englitz, Jonathan B Fritz, Shihab A Shamma
    Abstract:

    Rapid task-related plasticity is a neural correlate of selective attention in primary auditory cortex (A1). Top-Down Feedback from higher-order cortex may drive task-related plasticity in A1, characterized by enhanced neural representation of behaviorally meaningful sounds during auditory task performance. Since intracortical connectivity is greater within A1 layers 2/3 (L2/3) than in layers 4-6 (L4-6), we hypothesized that enhanced representation of behaviorally meaningful sounds might be greater in A1 L2/3 than L4-6. To test this hypothesis and study the laminar profile of task-related plasticity, we trained 2 ferrets to detect pure tones while we recorded laminar activity across a 1.8 mm depth in A1. In each experiment, we analyzed currentsource densities (CSDs), high-gamma local field potentials (LFPs), and multi-unit spiking in response to identical acoustic stimuli during both passive listening and active task performance. We found that neural responses to auditory targets were enhanced during task performance, and target enhancement was greater in L2/3 than in L4-6. Spectrotemporal receptive fields(STRFs) computed from CSDs, high-gamma LFPs, and multi-unit spiking showed similar increases in auditory target selectivity, also greatest in L2/3. Our results suggest that activity within intracortical networks plays a key role in shaping the underlying neural mechanisms of selective attention.

Alessandra Angelucci - One of the best experts on this subject based on the ideXlab platform.

  • top down Feedback controls spatial summation and response amplitude in primate visual cortex
    Nature Communications, 2018
    Co-Authors: Lauri Nurminen, Sam Merlin, Maryam Bijanzadeh, Frederick Federer, Alessandra Angelucci
    Abstract:

    Sensory information travels along feedforward connections through a hierarchy of cortical areas, which, in turn, send Feedback connections to lower-order areas. Feedback has been implicated in attention, expectation, and sensory context, but the mechanisms underlying these diverse Feedback functions are unknown. Using specific optogenetic inactivation of Feedback connections from the secondary visual area (V2), we show how Feedback affects neural responses in the primate primary visual cortex (V1). Reducing Feedback activity increases V1 cells’ receptive field (RF) size, decreases their responses to stimuli confined to the RF, and increases their responses to stimuli extending into the proximal surround, therefore reducing surround suppression. Moreover, stronger reduction of V2 Feedback activity leads to progressive increase in RF size and decrease in response amplitude, an effect predicted by a recurrent network model. Our results indicate that Feedback modulates RF size, surround suppression and response amplitude, similar to the modulatory effects of visual spatial attention. Feedback modulation of V1 is implicated in functions such as attention yet the precise neural mechanisms are not known. Here the authors report that optogenetic inactivation of V2 projections leads to modulation of V1 receptive field properties such as size, surround suppression and response amplitude.

  • top down Feedback controls spatial summation and response gain in primate visual cortex
    bioRxiv, 2017
    Co-Authors: Lauri Nurminen, Sam Merlin, Maryam Bijanzadeh, Frederick Federer, Alessandra Angelucci
    Abstract:

    In the cerebral cortex, sensory information travels along feedforward connections through a hierarchy of areas processing increasingly complex stimulus features1. Hierarchical processing, based solely on feedforward connections, has dominated most theories of sensory processing in neuroscience and computer vision over the past 50 years. These theories, however, have disregarded the existence of anatomically more prominent Feedback connections from higher- to lower-order cortical areas1, whose function remains hypothetical. Feedback has been implicated in attention, expectation, and sensory context, but the cellular mechanisms underlying these diverse Feedback functions are unknown. Moreover, it is controversial whether Feedback modulates response gain or surround suppression (the modulatory influence of sensory context on neuronal responses) in lower-order areas. Here we have performed the first specific inactivation of cortical Feedback at millisecond-time resolution, by optogenetically inactivating Feedback connections from the secondary (V2) to the primary visual cortex (V1) in primates. Moderate reduction of V2 Feedback activity increased RF size and reduced surround suppression in V1, while strongly reducing Feedback activity decreased response gain. Our study has identified a small set of fundamental operations as the cellular-level mechanisms of Feedback-mediated top down modulations of early sensory processing. These operations allow the visual system to dynamically regulate spatial resolution, by changing RF size, its sensitivity to image features, by changing response gain, and efficiency of coding natural images, by providing surround suppression.

  • the role of Feedback in shaping the extra classical receptive field of cortical neurons a recurrent network model
    The Journal of Neuroscience, 2006
    Co-Authors: Lars Schwabe, Klaus Obermayer, Alessandra Angelucci, Paul C Bressloff
    Abstract:

    The responses of neurons in sensory cortices are affected by the spatial context within which stimuli are embedded. In the primary visual cortex (V1), orientation-selective responses to stimuli in the receptive field (RF) center are suppressed by similarly oriented stimuli in the RF surround. Surround suppression, a likely neural correlate of perceptual figure–ground segregation, is traditionally thought to be generated within V1 by long-range horizontal connections. Recently however, it has been shown that these connections are too short and too slow to mediate fast suppression from distant regions of the RF surround. We use an anatomically and physiologically constrained recurrent network model of macaque V1 to show how interareal Feedback connections, which are faster and longer-range than horizontal connections, can generate “far” surround suppression. We provide a novel solution to the puzzle of how surround suppression can arise from excitatory Feedback axons contacting predominantly excitatory neurons in V1. The basic mechanism involves divergent Feedback connections from the far surround targeting pyramidal neurons sending monosynaptic horizontal connections to excitatory and inhibitory neurons in the RF center. One of several predictions of our model is that the “suppressive far surround” is not always suppressive, but can facilitate the response of the RF center, depending on the amount of excitatory drive to the local inhibitors. Our model provides a general mechanism of how Top-Down Feedback signals directly contribute to generating cortical neuron responses to simple sensory stimuli.

David G Norris - One of the best experts on this subject based on the ideXlab platform.

  • selective activation of the deep layers of the human primary visual cortex by top down Feedback
    Current Biology, 2016
    Co-Authors: Peter Kok, Lauren J Bains, Tim Van Mourik, David G Norris, Floris P. De Lange
    Abstract:

    In addition to bottom-up input, the visual cortex receives large amounts of Feedback from other cortical areas [1, 2 and 3]. One compelling example of Feedback activation of early visual neurons in the absence of bottom-up input occurs during the famous Kanizsa illusion, where a triangular shape is perceived, even in regions of the image where there is no bottom-up visual evidence for it. This illusion increases the firing activity of neurons in the primary visual cortex with a receptive field on the illusory contour [4]. Feedback signals are largely segregated from feedforward signals within each cortical area, with feedforward signals arriving in the middle layer, while Top-Down Feedback avoids the middle layers and predominantly targets deep and superficial layers [1, 2, 5 and 6]. Therefore, the Feedback-mediated activity increase in V1 during the perception of illusory shapes should lead to a specific laminar activity profile that is distinct from the activity elicited by bottom-up stimulation. Here, we used fMRI at high field (7 T) to empirically test this hypothesis, by probing the cortical response to illusory figures in human V1 at different cortical depths [7, 8, 9, 10, 11, 12, 13 and 14]. We found that, whereas bottom-up stimulation activated all cortical layers, Feedback activity induced by illusory figures led to a selective activation of the deep layers of V1. These results demonstrate the potential for non-invasive recordings of neural activity with laminar specificity in humans and elucidate the role of Top-Down signals during perceptual processing.