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Role of thalamo-cortical interactions in visual awareness
Abstracts SY2-B1-2 Motion Induced Blindness: The more you attend the less you see Olivia Carter 1,2 , Robert Luedeman 2 , Stephen Mitroff 3 , Ken Nakayama 2 1
S17
ing of chick spinal cord commissural axons in vivo. Draxin knockout mice showed defasciculation of spinal cord commissural axons and absence of all forebrain commissures. Thus, Draxin is a novel chemorepulsive axon guidance molecule required for the development of spinal cord and forebrain commissures.
Dept Psychology, Univ of Melbourne, Australia; 2 Dept Psychology, Harvard University, USA; 3 Center for Cognitive Neuroscience, Duke University, USA
doi:10.1016/j.neures.2009.09.1576
During motion induced blindness (MIB), visually salient objects vanish from awareness when presented on a background of motion. We conducted 3 psychophysical experiments looking at the effect of increasing target number, directed attention toward one target and reducing the amount of attention with a demanding secondary task at fixation. Together the results from all three experiments indicate that, awareness is indeed influenced by the same factors associated with attention. In every case, however, the relationship was seen to be in a negative direction. The more attention available for each target during MIB, the more it was suppressed from awareness. For all 3 experiments, a simulated MIB condition, ruled out the effect of task difficulty or response inaccuracy. A number of mechanisms are considered to explain this surprising effect.
SY2-C1-2 Identification of a novel axon guidance molecule serving for formation of lateral olfactory tract Kohtaro Takei 1 , Yasufumi Sato 1,2 , Megumi Yamaguchi 1 , Masumi Iketani 1 , Yuko Arie 1 , Yuji Kurihara 1 , Fumio Nakamura 1 , Takahiko Kawasaki 3 , Tatsumi Hirata 3 , Yoshio Goshima 1
doi:10.1016/j.neures.2009.09.1573
SY2-B1-3 Role of thalamo-cortical interactions in visual awareness Melanie Wilke 1,2 , Kai-Markus Mueller 2 , Janita Turchi 2 , Katy Smith 2 , Charles Zhu 2 , David A. Leopold 2 1
Caltech, USA
2
NIMH, USA
Little is known about the role of thalamo-cortical interactions in conscious perception. Here we studied thalamo-cortical activity related to visual awareness by combining behavioral measurements, electrophysiology, neuropharmacology and fMRI in monkeys. We first applied a paradigm which renders salient visual stimuli perceptually invisible. Our neurophysiological recordings revealed widespread perceptual modulation of local field potentials (LFP) in cortical areas V1, V2, V4 and LGN/pulvinar, accompanied by spiking rate changes in V4 and the pulvinar. Comparison of V4 and pulvinar latencies suggests that perceptual modulation of pulvinar neurons follows cortical input. Lastly, reversible inactivation of the pulvinar resulted in awareness-related behavioral deficits, and led to modest spiking and BOLD signal changes in visual areas, sparing V1. Based on these results, we speculate that a well coordinated thalamo-cortical interplay is a necessary condition for creating a visual percept. doi:10.1016/j.neures.2009.09.1574
SY2-B1-4 Intracranial recordings during continuous flash suppression and backward masking Naotsugu Tsuchiya Department HSS, Caltech, California, USA Intracranial recordings during epilepsy monitoring offer valuable experimental situations, where we can record direct neurophysiological responses from awake humans, with excellent spatiotemporal resolution from many brain sites simultaneously. With such an opportunity, we can investigate a specific hypothesis about the causal role of large-scale neuronal activity in producing subjective conscious feelings while subjects are performing a perceptual task. Here, we report the results of intracranial recording studies using two psychophysical techniques: backward masking and continuous flash suppression. In both tasks, we used faces as target stimuli. While subjects performed the tasks, we recorded intracranial EEG from 64–256 sites, including the primary visual cortex, the fusiform gyrus, the superior temporal sulcus, the amygdala. Applying a multivariate decoding techniques (Tsuchiya et al PLOS ONE 2008), we characterize those processing which are correlated with conscious visibility and those which are not available to consciousness, in terms of space (anatomical areas), time, and frequency bands. doi:10.1016/j.neures.2009.09.1575
SY2-C1-1 Draxin, a novel chemorepulsive axon guidance protein Md. Shahidul Islam Division of Developmental Neurobiology, Kumamoto University, Japan Axon guidance proteins are critical for the correct wiring of the nervous system during development. Several axon guidance cues and their family members have been well characterized. More unidentified axon guidance cues are assumed to participate in the formation of the extremely complex nervous system. We have identified a secreted protein, Draxin, that shares no homology with known guidance cues. Draxin inhibited or repelled neurite outgrowth from dorsal spinal cord and cortical explants in vitro. Ectopically expressed Draxin inhibited growth or caused misrout-
1
Dept. Mol. Pharmacol & Neurobiol, Yokohama City Univ, Yokohama, Japan; Brain Stroke Res Group, Mitsubishi Kagaku Inst Life Sci, Tokyo, Japan; 3 Div Brain Function, Nat Inst Genetics, Mishima, Japan
2
Lateral olfactory tract usher substance (LOTUS) is a newly identified, axon guidance molecule serving for the LOT formation in developing mouse brain, by functional screening using a fluorophore-assisted light inactivation (FALI) method. LOTUS was found on the plasma membrane surface of olfactory bulb neuron axons. We also identified Nogo-66 receptor (NgR1) as a LOTUS binding protein. FALI of LOTUS and/or NgR1 resulted in defasiculation of LOT axonal bundles. Molecular interaction between LOTUS and NgR1 induced cell-cell contract and promoted neurite outgrowth. Furthermore, binding of NgR1 ligands to NgR1 was completely inhibited by cis-binding of LOTUS to NgR1. Collectively, LOTUS may function as a promoting factor of neurite outgrowth and axonal bundle formation and also function as a negative regulator of Nogo signaling in LOT development. doi:10.1016/j.neures.2009.09.1577
SY2-C1-3 Axon guidance mediated by lysophosphatidylglucoside Hiroyuki Kamiguchi Lab for Neuronal Growth Mechanisms, RIKEN Brain Science Institute, Saitama, Japan During development, growing axons find their correct path by recognizing environmental cues. While many axon-guiding proteins and their receptors have been identified, much less attention has been paid to the importance of lipid molecules. Here I demonstrate an example of lipid-mediated axon guidance. Phosphatidylglucoside (PtdGlc), a phospholipid synthesized predominantly by immature astroglia in the nervous system, can be released into the extracellular space as lysophosphatidylglucoside (Lyso-PtdGlc) after enzymatic cleavage by phospholipase A2. PtdGlc expression is confined to several specific locations in the nervous system. Axons of TrkA-positive dorsal root ganglion (DRG) neurons are repelled by LysoPtdGlc presented as a gradient in vitro and do not invade the PtdGlc-positive areas in the spinal cord. In contrast, TrkC-positive DRG axons are insensitive to the LysoPtdGlc gradient in vitro and invade the PtdGlc-positive areas in vivo. Perturbation of Lyso-PtdGlc causes guidance errors of TrkA-positive axons in the spinal cord. These results indicate the critical role of this lipid molecule in neuronal circuit formation. doi:10.1016/j.neures.2009.09.1578
SY2-C1-4 Identification and characterization of molecules directing axon growth and target field innervation of somatosensory neurons Kenji Mandai, David D. Ginty Dept Neuroscience, HHMI, Johns Hopkins University, Baltimore, USA Genome-wide screens were performed to identify genes that mediate axon growth, guidance, and target innervation of distinct populations of developing somatosensory neurons, using dorsal root ganglia obtained from Ngf- or Nt3-null mice. These screens revealed the presence of a large number of genes expressed exclusively in TrkA+ or TrkC+ neurons. A novel gene, Linx, a member of a family of transmembrane proteins was identified as being highly expressed in TrkA+ neurons. Linx and its family members are found in unique subsets of sensory and motor neurons where they physically interact with TrkA and Ret. Interestingly, Linx mutant mice display axon projection defects, which resemble those found in mice lacking Ngf, TrkA and Ret. Moreover, sensory and motor neurons obtained from Linx mutant mice respond poorly to NGF and GDNF, respectively. These findings show that Linx and its family members form complexes with receptor tyrosine kinases in unique populations of developing neurons and modulate their activities to control axon growth, guidance and target innervation. doi:10.1016/j.neures.2009.09.1579
S17
ing of chick spinal cord commissural axons in vivo. Draxin knockout mice showed defasciculation of spinal cord commissural axons and absence of all forebrain commissures. Thus, Draxin is a novel chemorepulsive axon guidance molecule required for the development of spinal cord and forebrain commissures.
Dept Psychology, Univ of Melbourne, Australia; 2 Dept Psychology, Harvard University, USA; 3 Center for Cognitive Neuroscience, Duke University, USA
doi:10.1016/j.neures.2009.09.1576
During motion induced blindness (MIB), visually salient objects vanish from awareness when presented on a background of motion. We conducted 3 psychophysical experiments looking at the effect of increasing target number, directed attention toward one target and reducing the amount of attention with a demanding secondary task at fixation. Together the results from all three experiments indicate that, awareness is indeed influenced by the same factors associated with attention. In every case, however, the relationship was seen to be in a negative direction. The more attention available for each target during MIB, the more it was suppressed from awareness. For all 3 experiments, a simulated MIB condition, ruled out the effect of task difficulty or response inaccuracy. A number of mechanisms are considered to explain this surprising effect.
SY2-C1-2 Identification of a novel axon guidance molecule serving for formation of lateral olfactory tract Kohtaro Takei 1 , Yasufumi Sato 1,2 , Megumi Yamaguchi 1 , Masumi Iketani 1 , Yuko Arie 1 , Yuji Kurihara 1 , Fumio Nakamura 1 , Takahiko Kawasaki 3 , Tatsumi Hirata 3 , Yoshio Goshima 1
doi:10.1016/j.neures.2009.09.1573
SY2-B1-3 Role of thalamo-cortical interactions in visual awareness Melanie Wilke 1,2 , Kai-Markus Mueller 2 , Janita Turchi 2 , Katy Smith 2 , Charles Zhu 2 , David A. Leopold 2 1
Caltech, USA
2
NIMH, USA
Little is known about the role of thalamo-cortical interactions in conscious perception. Here we studied thalamo-cortical activity related to visual awareness by combining behavioral measurements, electrophysiology, neuropharmacology and fMRI in monkeys. We first applied a paradigm which renders salient visual stimuli perceptually invisible. Our neurophysiological recordings revealed widespread perceptual modulation of local field potentials (LFP) in cortical areas V1, V2, V4 and LGN/pulvinar, accompanied by spiking rate changes in V4 and the pulvinar. Comparison of V4 and pulvinar latencies suggests that perceptual modulation of pulvinar neurons follows cortical input. Lastly, reversible inactivation of the pulvinar resulted in awareness-related behavioral deficits, and led to modest spiking and BOLD signal changes in visual areas, sparing V1. Based on these results, we speculate that a well coordinated thalamo-cortical interplay is a necessary condition for creating a visual percept. doi:10.1016/j.neures.2009.09.1574
SY2-B1-4 Intracranial recordings during continuous flash suppression and backward masking Naotsugu Tsuchiya Department HSS, Caltech, California, USA Intracranial recordings during epilepsy monitoring offer valuable experimental situations, where we can record direct neurophysiological responses from awake humans, with excellent spatiotemporal resolution from many brain sites simultaneously. With such an opportunity, we can investigate a specific hypothesis about the causal role of large-scale neuronal activity in producing subjective conscious feelings while subjects are performing a perceptual task. Here, we report the results of intracranial recording studies using two psychophysical techniques: backward masking and continuous flash suppression. In both tasks, we used faces as target stimuli. While subjects performed the tasks, we recorded intracranial EEG from 64–256 sites, including the primary visual cortex, the fusiform gyrus, the superior temporal sulcus, the amygdala. Applying a multivariate decoding techniques (Tsuchiya et al PLOS ONE 2008), we characterize those processing which are correlated with conscious visibility and those which are not available to consciousness, in terms of space (anatomical areas), time, and frequency bands. doi:10.1016/j.neures.2009.09.1575
SY2-C1-1 Draxin, a novel chemorepulsive axon guidance protein Md. Shahidul Islam Division of Developmental Neurobiology, Kumamoto University, Japan Axon guidance proteins are critical for the correct wiring of the nervous system during development. Several axon guidance cues and their family members have been well characterized. More unidentified axon guidance cues are assumed to participate in the formation of the extremely complex nervous system. We have identified a secreted protein, Draxin, that shares no homology with known guidance cues. Draxin inhibited or repelled neurite outgrowth from dorsal spinal cord and cortical explants in vitro. Ectopically expressed Draxin inhibited growth or caused misrout-
1
Dept. Mol. Pharmacol & Neurobiol, Yokohama City Univ, Yokohama, Japan; Brain Stroke Res Group, Mitsubishi Kagaku Inst Life Sci, Tokyo, Japan; 3 Div Brain Function, Nat Inst Genetics, Mishima, Japan
2
Lateral olfactory tract usher substance (LOTUS) is a newly identified, axon guidance molecule serving for the LOT formation in developing mouse brain, by functional screening using a fluorophore-assisted light inactivation (FALI) method. LOTUS was found on the plasma membrane surface of olfactory bulb neuron axons. We also identified Nogo-66 receptor (NgR1) as a LOTUS binding protein. FALI of LOTUS and/or NgR1 resulted in defasiculation of LOT axonal bundles. Molecular interaction between LOTUS and NgR1 induced cell-cell contract and promoted neurite outgrowth. Furthermore, binding of NgR1 ligands to NgR1 was completely inhibited by cis-binding of LOTUS to NgR1. Collectively, LOTUS may function as a promoting factor of neurite outgrowth and axonal bundle formation and also function as a negative regulator of Nogo signaling in LOT development. doi:10.1016/j.neures.2009.09.1577
SY2-C1-3 Axon guidance mediated by lysophosphatidylglucoside Hiroyuki Kamiguchi Lab for Neuronal Growth Mechanisms, RIKEN Brain Science Institute, Saitama, Japan During development, growing axons find their correct path by recognizing environmental cues. While many axon-guiding proteins and their receptors have been identified, much less attention has been paid to the importance of lipid molecules. Here I demonstrate an example of lipid-mediated axon guidance. Phosphatidylglucoside (PtdGlc), a phospholipid synthesized predominantly by immature astroglia in the nervous system, can be released into the extracellular space as lysophosphatidylglucoside (Lyso-PtdGlc) after enzymatic cleavage by phospholipase A2. PtdGlc expression is confined to several specific locations in the nervous system. Axons of TrkA-positive dorsal root ganglion (DRG) neurons are repelled by LysoPtdGlc presented as a gradient in vitro and do not invade the PtdGlc-positive areas in the spinal cord. In contrast, TrkC-positive DRG axons are insensitive to the LysoPtdGlc gradient in vitro and invade the PtdGlc-positive areas in vivo. Perturbation of Lyso-PtdGlc causes guidance errors of TrkA-positive axons in the spinal cord. These results indicate the critical role of this lipid molecule in neuronal circuit formation. doi:10.1016/j.neures.2009.09.1578
SY2-C1-4 Identification and characterization of molecules directing axon growth and target field innervation of somatosensory neurons Kenji Mandai, David D. Ginty Dept Neuroscience, HHMI, Johns Hopkins University, Baltimore, USA Genome-wide screens were performed to identify genes that mediate axon growth, guidance, and target innervation of distinct populations of developing somatosensory neurons, using dorsal root ganglia obtained from Ngf- or Nt3-null mice. These screens revealed the presence of a large number of genes expressed exclusively in TrkA+ or TrkC+ neurons. A novel gene, Linx, a member of a family of transmembrane proteins was identified as being highly expressed in TrkA+ neurons. Linx and its family members are found in unique subsets of sensory and motor neurons where they physically interact with TrkA and Ret. Interestingly, Linx mutant mice display axon projection defects, which resemble those found in mice lacking Ngf, TrkA and Ret. Moreover, sensory and motor neurons obtained from Linx mutant mice respond poorly to NGF and GDNF, respectively. These findings show that Linx and its family members form complexes with receptor tyrosine kinases in unique populations of developing neurons and modulate their activities to control axon growth, guidance and target innervation. doi:10.1016/j.neures.2009.09.1579