The Experts below are selected from a list of 282 Experts worldwide ranked by ideXlab platform
Maurice Ptito - One of the best experts on this subject based on the ideXlab platform.
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neural networks mediating perceptual learning in Congenital Blindness
Scientific Reports, 2020Co-Authors: Danielrobert Chebat, Maurice Ptito, F SchneiderAbstract:Despite the fact that complete visual deprivation leads to volumetric reductions in brain structures associated with spatial learning, blind individuals are still able to navigate. The neural structures involved in this function are not fully understood. Our study aims to correlate the performance of Congenitally blind individuals (CB) and blindfolded sighted controls (SC) in a life-size obstacle-course using a visual-to-tactile sensory substitution device, with the size of brain structures (voxel based morphometry-VBM-) measured through structural magnetic resonance Imaging (MRI). VBM was used to extract grey matter volumes within several a-priori defined brain regions in all participants. Principal component analysis was utilized to group brain regions in factors and orthogonalize brain volumes. Regression analyses were then performed to link learning abilities to these factors. We found that (1) both CB and SC were able to learn to detect and avoid obstacles; (2) their learning rates for obstacle detection and avoidance correlated significantly with the volume of brain structures known to be involved in spatial skills. There is a similar relation between regions of the dorsal stream network and avoidance for both SC and CB whereas for detection, SC rely more on medial temporal lobe structures and CB on sensorimotor areas.
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A thalamocortical pathway for fast rerouting of tactile information to occipital cortex in Congenital Blindness
Nature Communications, 2019Co-Authors: Franziska Müller, Maurice Ptito, Guiomar Niso, Soheila Samiee, Sylvain Baillet, Ron KupersAbstract:In Congenitally blind individuals, the occipital cortex responds to various nonvisual inputs. Some animal studies raise the possibility that a subcortical pathway allows fast re-routing of tactile information to the occipital cortex, but this has not been shown in humans. Here we show using magnetoencephalography (MEG) that tactile stimulation produces occipital cortex activations, starting as early as 35 ms in Congenitally blind individuals, but not in blindfolded sighted controls. Given our measured thalamic response latencies of 20 ms and a mean estimated lateral geniculate nucleus to primary visual cortex transfer time of 15 ms, we claim that this early occipital response is mediated by a direct thalamo-cortical pathway. We also observed stronger directed connectivity in the alpha band range from posterior thalamus to occipital cortex in Congenitally blind participants. Our results strongly suggest the contribution of a fast thalamo-cortical pathway in the cross-modal activation of the occipital cortex in Congenitally blind humans. In Congenitally blind people, tactile stimuli can activate the occipital (visual) cortex. Here, the authors show using magnetoencephalography (MEG) that occipital activation can occur within 35 ms following tactile stimulation, suggesting the existence of a fast thalamocortical pathway for touch in Congenitally blind humans.
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Uncertainty about the intensity of impending pain increases ensuing pain responses in Congenital Blindness
Behavioural Brain Research, 2017Co-Authors: S. Holten-rossing, Hocine Slimani, Maurice Ptito, Sabrina Danti, Ron KupersAbstract:Abstract We have shown that Congenitally blind individuals are more sensitive to painful heat compared to their sighted counterparts. This hypersensitivity might be at least partly mediated by psychological and cognitive factors, such as pain expectation and anxiety. Here we investigate whether uncertainty about the intensity of a pending painful stimulus affects pain differently in Congenitally blind and sighted control subjects. We measured pain and anxiety in a group of 11 Congenitally blind and 11 age- and sex-matched normal sighted control participants. Painful stimuli were delivered under two psychological conditions, whereby participants were either certain or uncertain about the intensity of a pending noxious stimuli. Although both blind and sighted participants had increased anxiety ratings in the uncertain condition, pain ratings increased only in the Congenitally blind participants. Our data therefore indicate that increased anxiety levels have a stronger influence on the perceived pain intensity in blind individuals, possibly because they allocate greater attention to signals of external threat.
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Pain hypersensitivity in Congenital Blindness is associated with faster central processing of C-fibre input
European Journal of Pain, 2016Co-Authors: Hocine Slimani, Léon Plaghki, Maurice Ptito, Ron KupersAbstract:Background We have recently shown that visual deprivation from birth exacerbates responses to painful thermal stimuli. However, the mechanisms underlying pain hypersensitivity in Congenital Blindness are unclear. Methods To study the contribution of Aδ- and C-fibres in pain perception, we measured thresholds and response times to selective C- and Aδ-fibre activation in Congenitally blind, late blind and normally sighted participants. Ultrafast constant-temperature heat pulses were delivered to the hand with a CO2 laser using an interleaved adaptive double staircase procedure. Participants were instructed to respond as quickly as possible when detecting a laser-induced sensation. We used a 650 ms cut-off criterion to distinguish fast Aδ- from slow C-fibre–mediated sensations. Results Congenitally blind participants showed significantly faster reaction times to C- but not to Aδ-fibre–mediated sensations. In contrast, thresholds for Aδ- and C-fibre stimulation did not differ between groups. Late blind individuals did not differ from sighted controls in any aspect. A follow-up experiment using only suprathreshold stimuli for Aδ- and C-fibre activation confirmed these findings and further showed that Congenitally blind individuals detected significantly more C-fibre–mediated stimuli than sighted controls. A decomposition analysis of the reaction times indicated that the faster response times in the Congenitally blind are due to more efficient central processing of C-fibre–mediated sensations. Conclusion The increased sensitivity to painful thermal stimulation in Congenital Blindness may be due to more efficient central processing of C-fibre–mediated input, which may help to avoid impending dangerous encounters with stimuli that threaten the bodily integrity. What does this study add? Hypersensitivity to heat pain in Congenital Blindness is associated with faster responses to C-fibre activation, likely caused by more efficient central processing of C-fibre–mediated input.
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Congenital Blindness affects diencephalic but not mesencephalic structures in the human brain
Brain Structure & Function, 2016Co-Authors: Luca Cecchetti, Maurice Ptito, Emiliano Ricciardi, Giacomo Handjaras, Ronny Clement F Kupers, Pietro PietriniAbstract:While there is ample evidence that the structure and function of visual cortical areas are affected by early visual deprivation, little is known of how early Blindness modifies subcortical relay and association thalamic nuclei, as well as mesencephalic structures. Therefore, in the present multicenter study, we used MRI to measure volume of the superior and inferior colliculi, as well as of the thalamic nuclei relaying sensory and motor information to the neocortex, parcellated according to atlas-based thalamo-cortical connections, in 29 individuals with Congenital Blindness of peripheral origin (17 M, age 35.7 ± 14.3 years) and 29 sighted subjects (17 M, age 31.9 ± 9.0). Blind participants showed an overall volume reduction in the left (p = 0.008) and right (p = 0.007) thalami, as compared to the sighted individuals. Specifically, the lateral geniculate (i.e., primary visual thalamic relay nucleus) was 40 % reduced (left: p = 4 × 10−6, right: p < 1 × 10−6), consistent with findings from animal studies. In addition, associated thalamic nuclei that project to temporal (left: p = 0.005, right: p = 0.005), prefrontal (left: p = 0.010, right: p = 0.014), occipital (left: p = 0.005, right: p = 0.023), and right premotor (p = 0.024) cortical regions were also significantly reduced in the Congenitally blind group. Conversely, volumes of the relay nuclei directly involved in auditory, motor, and somatosensory processing were not affected by visual deprivation. In contrast, no difference in volume was observed in either the superior or the inferior colliculus between the two groups. Our findings indicate that visual loss since birth leads to selective volumetric changes within diencephalic, but not mesencephalic, structures. Both changes in reciprocal cortico-thalamic connections or modifications in the intrinsic connectivity between relay and association nuclei of the thalamus may contribute to explain these alterations in thalamic volumes. Sparing of the superior colliculi is in line with their composite, multisensory projections, and with their not exclusive visual nature.
Ron Kupers - One of the best experts on this subject based on the ideXlab platform.
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A thalamocortical pathway for fast rerouting of tactile information to occipital cortex in Congenital Blindness
Nature Communications, 2019Co-Authors: Franziska Müller, Maurice Ptito, Guiomar Niso, Soheila Samiee, Sylvain Baillet, Ron KupersAbstract:In Congenitally blind individuals, the occipital cortex responds to various nonvisual inputs. Some animal studies raise the possibility that a subcortical pathway allows fast re-routing of tactile information to the occipital cortex, but this has not been shown in humans. Here we show using magnetoencephalography (MEG) that tactile stimulation produces occipital cortex activations, starting as early as 35 ms in Congenitally blind individuals, but not in blindfolded sighted controls. Given our measured thalamic response latencies of 20 ms and a mean estimated lateral geniculate nucleus to primary visual cortex transfer time of 15 ms, we claim that this early occipital response is mediated by a direct thalamo-cortical pathway. We also observed stronger directed connectivity in the alpha band range from posterior thalamus to occipital cortex in Congenitally blind participants. Our results strongly suggest the contribution of a fast thalamo-cortical pathway in the cross-modal activation of the occipital cortex in Congenitally blind humans. In Congenitally blind people, tactile stimuli can activate the occipital (visual) cortex. Here, the authors show using magnetoencephalography (MEG) that occipital activation can occur within 35 ms following tactile stimulation, suggesting the existence of a fast thalamocortical pathway for touch in Congenitally blind humans.
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Uncertainty about the intensity of impending pain increases ensuing pain responses in Congenital Blindness
Behavioural Brain Research, 2017Co-Authors: S. Holten-rossing, Hocine Slimani, Maurice Ptito, Sabrina Danti, Ron KupersAbstract:Abstract We have shown that Congenitally blind individuals are more sensitive to painful heat compared to their sighted counterparts. This hypersensitivity might be at least partly mediated by psychological and cognitive factors, such as pain expectation and anxiety. Here we investigate whether uncertainty about the intensity of a pending painful stimulus affects pain differently in Congenitally blind and sighted control subjects. We measured pain and anxiety in a group of 11 Congenitally blind and 11 age- and sex-matched normal sighted control participants. Painful stimuli were delivered under two psychological conditions, whereby participants were either certain or uncertain about the intensity of a pending noxious stimuli. Although both blind and sighted participants had increased anxiety ratings in the uncertain condition, pain ratings increased only in the Congenitally blind participants. Our data therefore indicate that increased anxiety levels have a stronger influence on the perceived pain intensity in blind individuals, possibly because they allocate greater attention to signals of external threat.
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Pain hypersensitivity in Congenital Blindness is associated with faster central processing of C-fibre input
European Journal of Pain, 2016Co-Authors: Hocine Slimani, Léon Plaghki, Maurice Ptito, Ron KupersAbstract:Background We have recently shown that visual deprivation from birth exacerbates responses to painful thermal stimuli. However, the mechanisms underlying pain hypersensitivity in Congenital Blindness are unclear. Methods To study the contribution of Aδ- and C-fibres in pain perception, we measured thresholds and response times to selective C- and Aδ-fibre activation in Congenitally blind, late blind and normally sighted participants. Ultrafast constant-temperature heat pulses were delivered to the hand with a CO2 laser using an interleaved adaptive double staircase procedure. Participants were instructed to respond as quickly as possible when detecting a laser-induced sensation. We used a 650 ms cut-off criterion to distinguish fast Aδ- from slow C-fibre–mediated sensations. Results Congenitally blind participants showed significantly faster reaction times to C- but not to Aδ-fibre–mediated sensations. In contrast, thresholds for Aδ- and C-fibre stimulation did not differ between groups. Late blind individuals did not differ from sighted controls in any aspect. A follow-up experiment using only suprathreshold stimuli for Aδ- and C-fibre activation confirmed these findings and further showed that Congenitally blind individuals detected significantly more C-fibre–mediated stimuli than sighted controls. A decomposition analysis of the reaction times indicated that the faster response times in the Congenitally blind are due to more efficient central processing of C-fibre–mediated sensations. Conclusion The increased sensitivity to painful thermal stimulation in Congenital Blindness may be due to more efficient central processing of C-fibre–mediated input, which may help to avoid impending dangerous encounters with stimuli that threaten the bodily integrity. What does this study add? Hypersensitivity to heat pain in Congenital Blindness is associated with faster responses to C-fibre activation, likely caused by more efficient central processing of C-fibre–mediated input.
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prevalence of increases in functional connectivity in visual somatosensory and language areas in Congenital Blindness
Frontiers in Neuroanatomy, 2015Co-Authors: Lizette Heine, Maurice Ptito, Mohamed Ali Bahri, Carlo Cavaliere, Andrea Soddu, Steven Laureys, Ron KupersAbstract:There is ample evidence that Congenitally blind individuals rely more strongly on non-visual information compared to sighted controls when interacting with the outside world. Although brain imaging studies indicate that Congenitally blind individuals recruit occipital areas when performing various non-visual and cognitive tasks, it remains unclear through which pathways this is accomplished. To address this question, we compared resting state functional connectivity in a group of Congenitally blind and matched sighted control subjects. We used a seed-based analysis with a priori specified regions-of-interest (ROIs) within visual, somato-sensory, auditory and language areas. Between-group comparisons revealed increased functional connectivity within both the ventral and the dorsal visual streams in blind participants, whereas connectivity between the two streams was reduced. In addition, our data revealed stronger functional connectivity in blind participants between the visual ROIs and areas implicated in language and tactile (Braille) processing such as the inferior frontal gyrus (Broca’s area), thalamus, supramarginal gyrus and cerebellum. The observed group differences underscore the extent of the cross-modal reorganisation in the brain and the supra-modal function of the occipital cortex in Congenitally blind individuals.
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superior orthonasal but not retronasal olfactory skills in Congenital Blindness
PLOS ONE, 2015Co-Authors: Maurice Ptito, Ron Kupers, Lea Gagnon, Abd Rahman Alaoui IsmailiAbstract:Sight is undoubtedly important for finding and appreciating food, and cooking. Blind individuals are strongly impaired in finding food, limiting the variety of flavours they are exposed to. We have shown before that compared to sighted controls, Congenitally blind individuals have enhanced olfactory but reduced taste perception. In this study we tested the hypothesis that Congenitally blind subjects have enhanced orthonasal but not retronasal olfactory skills. Twelve Congenitally blind and 14 sighted control subjects, matched in age, gender and body mass index, were asked to identify odours using grocery-available food powders. Results showed that blind subjects were significantly faster and tended to be better at identifying odours presented orthonasally. This was not the case when odorants were presented retronasally. We also found a significant group x route interaction, showing that although both groups performed better for retronasally compared to orthonasally presented odours, this gain was less pronounced for blind subjects. Finally, our data revealed that blind subjects were more familiar with the orthonasal odorants and used the retronasal odorants less often for cooking than their sighted counterparts. These results confirm that orthonasal but not retronasal olfactory perception is enhanced in Congenital Blindness, a result that is concordant with the reduced food variety exposure in this group.
Albert M Maguire - One of the best experts on this subject based on the ideXlab platform.
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amelioration of neurosensory structure and function in animal and cellular models of a Congenital Blindness
Molecular Therapy, 2018Co-Authors: Ji Yun Song, Jeannette L Bennicelli, Arkady Lyubarsky, Puya Aravand, Sergei S Nikonov, Ivan Shpylchak, Pamela S Herrera, Daniel J Bennett, Nicoletta Commins, Albert M MaguireAbstract:Most genetically distinct inherited retinal degenerations are primary photoreceptor degenerations. We selected a severe early onset form of Leber Congenital amaurosis (LCA), caused by mutations in the gene LCA5, in order to test the efficacy of gene augmentation therapy for a ciliopathy. The LCA5-encoded protein, Lebercilin, is essential for the trafficking of proteins and vesicles to the photoreceptor outer segment. Using the AAV serotype AAV7m8 to deliver a human LCA5 cDNA into an Lca5 null mouse model of LCA5, we show partial rescue of retinal structure and visual function. Specifically, we observed restoration of rod-and-cone-driven electroretinograms in about 25% of injected eyes, restoration of pupillary light responses in the majority of treated eyes, an ∼20-fold decrease in target luminance necessary for visually guided behavior, and improved retinal architecture following gene transfer. Using LCA5 patient-derived iPSC-RPEs, we show that delivery of the LCA5 cDNA restores lebercilin protein and rescues cilia quantity. The results presented in this study support a path forward aiming to develop safety and efficacy trials for gene augmentation therapy in human subjects with LCA5 mutations. They also provide the framework for measuring the effects of intervention in ciliopathies and other severe, early-onset blinding conditions.
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in utero gene therapy rescues vision in a murine model of Congenital Blindness
Molecular Therapy, 2004Co-Authors: Nadine S Dejneka, Enrico Maria Surace, Tomas S Aleman, Artur V Cideciyan, Arkady Lyubarsky, Andrey B Savchenko, Michael T Redmond, Waixing Tang, Ernest Glover, Albert M MaguireAbstract:Abstract The Congenital retinal Blindness known as Leber Congenital amaurosis (LCA) can be caused by mutations in the RPE65 gene. RPE65 plays a critical role in the visual cycle that produces the photosensitive pigment rhodopsin. Recent evidence from human studies of LCA indicates that earlier rather than later intervention may be more likely to restore vision. We determined the impact of in utero delivery of the human RPE65 cDNA to retinal pigment epithelium cells in a murine model of LCA, the Rpe65 −/− mouse, using a serotype 2 adeno-associated virus packaged within an AAV1 capsid (AAV2/1). Delivery of AAV2/1-CMV- hRPE65 to fetuses (embryonic day 14) resulted in efficient transduction of retinal pigment epithelium, restoration of visual function, and measurable rhodopsin. The results demonstrate AAV-mediated correction of the deficit and suggest that in utero retinal gene delivery may be a useful approach for treating a variety of blinding Congenital retinal diseases.
Olaf B Paulson - One of the best experts on this subject based on the ideXlab platform.
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crossmodal recruitment of the ventral visual stream in Congenital Blindness
Neural Plasticity, 2012Co-Authors: Maurice Ptito, Olaf B Paulson, Hartwig R Siebner, Isabelle Matteau, Arthur Zhi Wang, Ron KupersAbstract:We used functional MRI (fMRI) to test the hypothesis that blind subjects recruit the ventral visual stream during nonhaptic tactile-form recognition. Congenitally blind and blindfolded sighted control subjects were scanned after they had been trained during four consecutive days to perform a tactile-form recognition task with the tongue display unit (TDU). Both groups learned the task at the same rate. In line with our hypothesis, the fMRI data showed that during nonhaptic shape recognition, blind subjects activated large portions of the ventral visual stream, including the cuneus, precuneus, inferotemporal (IT), cortex, lateral occipital tactile vision area (LOtv), and fusiform gyrus. Control subjects activated area LOtv and precuneus but not cuneus, IT and fusiform gyrus. These results indicate that Congenitally blind subjects recruit key regions in the ventral visual pathway during nonhaptic tactile shape discrimination. The activation of LOtv by nonhaptic tactile shape processing in blind and sighted subjects adds further support to the notion that this area subserves an abstract or supramodal representation of shape. Together with our previous findings, our data suggest that the segregation of the efferent projections of the primary visual cortex into a dorsal and ventral visual stream is preserved in individuals blind from birth.
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Activation of the hippocampal complex during tactile maze solving in Congenitally blind subjects
Neuropsychologia, 2012Co-Authors: Lea Gagnon, Ron Kupers, Olaf B Paulson, Hartwig R Siebner, F. Schneider, Maurice PtitoAbstract:Abstract Despite their lack of vision, Congenitally blind subjects are able to build and manipulate cognitive maps for spatial navigation. It is assumed that they thereby rely more heavily on echolocation, proprioceptive signals and environmental cues such as ambient temperature and audition to compensate for their lack of vision. Little is known, however, about the neural mechanisms underlying spatial navigation in blind individuals in settings where these cues are absent. We therefore measured behavioural performance and blood oxygenation-level dependant (BOLD) responses using functional magnetic resonance imaging (fMRI) in Congenitally blind and blindfolded sighted participants while they navigated through a tactile multiple T-maze. Both groups learned the maze task at a similar pace. In blind participants, tactile maze navigation was associated with increased BOLD responses in the right hippocampus and parahippocampus, occipital cortex and fusiform gyrus. Blindfolded sighted controls did not show increased BOLD responses in these areas; instead they activated the caudate nucleus and thalamus. Both groups activated the precuneus during tactile maze navigation. We conclude that cross-modal plastic processes allow for the recruitment of the hippocampal complex and visual cortex in Congenital Blindness.
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neural correlates of olfactory processing in Congenital Blindness
Neuropsychologia, 2011Co-Authors: Ron Kupers, Maurice Ptito, M Beaulieulefebvre, F Schneider, Tanja Kassuba, Olaf B Paulson, Hartwig R SiebnerAbstract:Adaptive neuroplastic changes have been well documented in Congenitally blind individuals for the processing of tactile and auditory information. By contrast, very few studies have investigated olfactory processing in the absence of vision. There is ample evidence that the olfactory system is highly plastic and that blind individuals rely more on their sense of smell than the sighted do. The olfactory system in the blind is therefore likely to be susceptible to cross-modal changes similar to those observed for the tactile and auditory modalities. To test this hypothesis, we used functional magnetic resonance imaging to measure changes in the blood-oxygenation level-dependent signal in Congenitally blind and blindfolded sighted control subjects during a simple odor detection task. We found several group differences in taskrelated activations. Compared to sighted controls, Congenitally blind subjects more strongly activated primary (right amygdala) and secondary (right orbitofrontal cortex and bilateral hippocampus) olfactory areas. In addition, widespread task-related activations were found throughout the whole extent of the occipital cortex in blind but not in sighted participants. The stronger recruitment of the occipital cortex during odor detection demonstrates a preferential access of olfactory stimuli to this area when vision is lacking from birth. This finding expands current knowledge about the supramodal function of the visually deprived occipital cortex in Congenital Blindness, linking it also to olfactory processing in addition to tactile and auditory processing.
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neural correlates of virtual route recognition in Congenital Blindness
Proceedings of the National Academy of Sciences of the United States of America, 2010Co-Authors: Ron Kupers, Olaf B Paulson, Danielrobert Chebat, Kristoffer Hougaard Madsen, Maurice PtitoAbstract:Despite the importance of vision for spatial navigation, blind subjects retain the ability to represent spatial information and to move independently in space to localize and reach targets. However, the neural correlates of navigation in subjects lacking vision remain elusive. We therefore used functional MRI (fMRI) to explore the cortical network underlying successful navigation in blind subjects. We first trained Congenitally blind and blindfolded sighted control subjects to perform a virtual navigation task with the tongue display unit (TDU), a tactile-to-vision sensory substitution device that translates a visual image into electrotactile stimulation applied to the tongue. After training, participants repeated the navigation task during fMRI. Although both groups successfully learned to use the TDU in the virtual navigation task, the brain activation patterns showed substantial differences. Blind but not blindfolded sighted control subjects activated the parahippocampus and visual cortex during navigation, areas that are recruited during topographical learning and spatial representation in sighted subjects. When the navigation task was performed under full vision in a second group of sighted participants, the activation pattern strongly resembled the one obtained in the blind when using the TDU. This suggests that in the absence of vision, cross-modal plasticity permits the recruitment of the same cortical network used for spatial navigation tasks in sighted subjects.
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Alterations of the visual pathways in Congenital Blindness
Experimental Brain Research, 2008Co-Authors: Maurice Ptito, Olaf B Paulson, Fabien C. G. Schneider, Ron KupersAbstract:We used whole brain MRI voxel-based morphometry (VBM) to study the anatomical organization of the visual system in Congenitally blind (CB) adults. Eleven CB without a history of visual perception were compared with 21 age- and sex-matched normal-sighted controls (NS). CB showed significant atrophy of the geniculo-striate system, encompassing the optic nerves, the optic chiasm, the optic radiations and the primary visual cortex (BA17). The volume decrease in BA17 reached 25% in both hemispheres. The pulvinar and its projections to the associative visual areas were also dramatically altered, BA18/19 and the middle temporal cortex (MT) showing volume reductions of up to 20%. Additional significant white matter alterations were observed in the inferior longitudinal tract and in the posterior part of the corpus callosum, which links the visual areas of both hemispheres. Our data indicate that the afferent projections to the visual cortex in CB are largely atrophied. Despite the massive volume reductions in the occipital lobes, there is compelling evidence from the literature (reviewed in Noppeney 2007 ; Ptito and Kupers 2005 ) that blind subjects activate their visual cortex when performing tasks that involve somatosensory or auditory inputs, suggesting a reorganization of the neural pathways that transmit sensory information to the visual cortex.
Colette Dehay - One of the best experts on this subject based on the ideXlab platform.
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unique features of subcortical circuits in a macaque model of Congenital Blindness
Cerebral Cortex, 2020Co-Authors: Loic Magrou, Pascal Barone, Nikola T Markov, Gwylan Scheeren, Herbert P Killackey, Pascale Giroud, Michel Berland, Kenneth Knoblauch, Colette DehayAbstract:There is an extensive modification of the functional organization of the brain in the Congenital blind human, although there is little understanding of the structural underpinnings of these changes. The visual system of macaque has been extensively characterized both anatomically and functionally. We have taken advantage of this to examine the influence of Congenital Blindness in a macaque model of developmental anophthalmia. Developmental anophthalmia in macaque effectively removes the normal influence of the thalamus on cortical development leading to an induced "hybrid cortex (HC)" combining features of primary visual and extrastriate cortex. Here we show that retrograde tracers injected in early visual areas, including HC, reveal a drastic reduction of cortical projections of the reduced lateral geniculate nucleus. In addition, there is an important expansion of projections from the pulvinar complex to the HC, compared to the controls. These findings show that the functional consequences of Congenital Blindness need to be considered in terms of both modifications of the interareal cortical network and the ascending visual pathways.
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unique features of sub cortical circuits in a macaque model of Congenital Blindness
bioRxiv, 2019Co-Authors: Loic Magrou, Nikola T Markov, Gwylan Scheeren, Herbert P Killackey, Pascale Giroud, Michel Berland, Kenneth Knoblauch, Colette Dehay, Pascale Barone, Henry KennedyAbstract:There is extensive modification of the functional organization of the brain in the Congenital blind human, although there is little understanding of the structural underpinnings of these changes. The visual system of macaque has been extensively characterized both anatomically and functionally. We have taken advantage of this to examine the influence of the Congenital Blindness in macaque resulting from the removal of the retina during in utero development. Developmental anophthalmia in macaque effectively removes the normal influence of the thalamus on cortical development leading to an induced hybrid cortex (HC) combining features of primary visual and extrastriate cortex. Here we show that retrograde tracers injected in early visual areas including hybrid cortex reveals a drastic reduction of cortical projections of the reduced lateral geniculate nucleus. In addition there is an important expansion of projections from the pulvinar complex to the hybrid cortex, compared to the controls. These findings show that the functional consequences of Congenital Blindness need to be considered in terms of both modifications of the inter-areal cortical network and the ascending visual pathways.
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How Areal Specification Shapes the Local and Interareal Circuits in a Macaque Model of Congenital Blindness
Cerebral Cortex, 2018Co-Authors: Loic Magrou, Pascal Barone, Nikola T Markov, Herbert P Killackey, Pascale Giroud, Michel Berland, Kenneth Knoblauch, Colette Dehay, Henry KennedyAbstract:There is little understanding of the structural underpinnings of the functional reorganization of the cortex in the Congenitally blind human. Taking advantage of the extensive characterization of the macaque visual system, we examine in macaque the influence of Congenital Blindness resulting from the removal of the retina during in utero development. This effectively removes the normal influence of the thalamus on cortical development leading to an induced hybrid cortex (HC) combining features of primary visual and extrastriate cortex. Retrograde tracers injected in HC reveal a local, intrinsic connectivity characteristic of higher order areas and show that the HC receives a uniquely strong, purely feedforward projection from striate cortex but no ectopic inputs, except from subiculum, and entorhinal cortex. Statistical modeling of quantitative connectivity data shows that HC is relatively high in the cortical hierarchy and receives a reinforced input from ventral stream areas while the overall organization of the functional streams are conserved. The directed and weighted anophthalmic cortical graph from the present study can be used to construct dynamic and structural models. These findings show how the sensory periphery governs cortical phenotype and reveal the importance of developmental arealization for understanding the functional reorganization in Congenital Blindness.
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cortical connectivity in a macaque model of Congenital Blindness
bioRxiv, 2017Co-Authors: Loic Magrou, Pascal Barone, Nikola T Markov, Herbert P Killackey, Pascale Giroud, Michel Berland, Kenneth Knoblauch, Colette Dehay, Henry KennedyAbstract:Brain-mapping of the Congenitally blind human reveals extensive plasticity. The visual cortex of the blind has been observed to support higher cognitive functions including language and numerical processing. This functional shift is hypothesized to reflect a metamodal cortical function, where computations are defined by the local network. In the case of developmental deafferentation, local circuits are considered to implement higher cognitive functions by accommodating diverse long-distance inputs. However, the extent to which visual deprivation triggers a reorganization of the large-scale network in the cortex is still controversial. Here we show that early prenatal ablation of the retina, an experimental model of anophthalmia in macaque, leads to a major reduction of area V1 and the creation of a default extrastriate cortex (DEC). Anophthalmic and normal macaques received retrograde tracer injections in DEC, as well as areas V2 and V4 post-natally. This revealed a six-fold expansion of the spatial extent of local connectivity in the DEC and a surprisingly high location of the DEC derived from a computational model of the cortical hierarchy. In the anophthalmic the set of areas projecting to the DEC, area V2 and V4 does not differ from that of normal adult controls, but there is a highly significant increase in the relative cumulative weight of the ventral stream areas input to the early visual areas. These findings show that although occupying the territory that would have become primary visual cortex the DEC exhibits features of a higher order area, thus reflecting a combination of intrinsic and extrinsic factors on cortical specification. Understanding the interaction of these contributing factors will shed light on cortical plasticity during primate development and the neurobiology of Blindness.