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BOLD fMRI dynamics in monkeys reflects spatial decisions in free-choice and reward context tasks
S60
Abstracts
the location of the FOE. A computational model of saliency-based attention that includes the FOE well describes observers scan paths. Our study has implications for filming and for everyday life.
O2-I4-2 Cantor coding in a model of hippocampal CA1 Yutaka Yamaguti, Shigeru Kuroda, Ichiro Tsuda
doi:10.1016/j.neures.2009.09.163
Based on the theory that the hippocampus is responsible for formation of episodic memory, we proposed a mathematical model for the hippocampus. The Cantor coding hypothesis in CA1 has been proposed, which provides a scheme for encoding temporal sequences of events. Here, in order for investigating the Cantor coding in detail, we constructed a model for the CA1 network which consists of conductancebased model neurons. We examined dependencies of output patterns of CA1 neurons on input temporal sequences of spatial patterns produced by CA3. It was shown that the output patterns of CA1 were hierarchically clustered in a self-similar manner according to the similarity of input time-series. Furthermore, linear discriminant analysis clarified that the performance of the Cantor coding sensitively depends on the input strength and the time interval of input sequence. NMDA synaptic connections enhanced the performance of the coding of input sequences with long (100–200 mses) intervals. These results suggest that Cantor set-like structure encoding time-series is formed in state space of neural dynamics.
O2-I3-3 BOLD fMRI dynamics in monkeys reflects spatial decisions in free-choice and reward context tasks Igor Kagan, Melanie Wilke, Richard A. Andersen Caltech, USA We investigated voluntary decision-making and motor planning in monkeys with time-resolved event-related high-field fMRI. We previously found strong contralateral tuning of frontoparietal BOLD activity during a memory saccade task. Here we used a spatial decision task to assess the dynamics of response selection. Two equally rewarded targets were presented and after a delay monkeys could select either location. The contralateral build-up of BOLD activity during the delay reflected the monkeys’ choices, and different areas signaled the decision at different times. Internal spatial preferences were reflected in the inter-hemispheric imbalance of left/right spatial representations. These patterns imply mutually suppressive interactions between two response options. Next, we introduced a reward context associated with target colors. The behavioral preference for large expected rewards was paralleled by a stronger delay period activity, supporting prospective evaluation of goal-directed actions. We suggest a common mechanism integrating internal and external variables during oculomotor decisions. doi:10.1016/j.neures.2009.09.164
O2-I3-4 Spatial working memory after V1 lesion Kana Takaura 1,2 , Masatoshi Yoshida 1,2 , Tadashi Isa 1,2,3 1
Sch. Life Sci., Grad. University Adv. Stud., Hayama, Japan; Dev. Physiol., NIPS, Japan; 3 CREST, Kawaguchi, Japan
2
Department
Blindsight is a phenomenon in which patients with damages to the primary visual cortex (V1) exhibit residual ability of visuomotor transformation without visual awareness. Visual awareness has been proposed to be tightly linked to working memory. Previously we reported that monkeys with unilateral V1 lesion, which have been used as an animal model of the blindsight, can retain spatial memory of cues briefly presented for at least 2 seconds. To investigate neural mechanisms for spatial memory in the visual field affected by lesion, we recorded neuronal activities in the superior colliculus (SC). We found that most of the neurons in the ipsilesional SC exhibited sustained activities throughout the delay period when cues were presented inside the receptive fields. In naive brain, such kind of activity has been reported in the cerebral cortex. Our results challenge the prevailing hypothesis about the relationship between visual awareness and working memory, and indicate that the SC could compensate for some functional roles of the cerebral cortices after cerebral damages. doi:10.1016/j.neures.2009.09.165
O2-I4-1 Iterated function systems in the hippocampal CA1 Shigeru Kuroda 1 , Yasuhiro Fukushima 2 , Yutaka Yamaguti 1 , Minoru Tsukada 2 , Ichiro Tsuda 1,3 1
RIES, Hokkaido Univ., Hokkaido, Japan; 2 Brain Sci. Inst., Tamagawa Univ., Tokyo, Japan; 3 Dept. Sci., Hokkaido Univ., Hokkaido, Japan
How does the information of spatiotemporal sequence stemming from the hippocampal CA3 area affect the postsynaptic membrane potentials of the hippocampal CA1 neurons? In (Fukushima et al., 2007), we observed hierarchical clusters of the distribution of membrane potentials of CA1 neurons, arranged according to the history of input sequences. In this study, to clarify the dynamical mechanism generating such a hierarchical distribution, we investigated the recording data using return map analysis (Kuroda et al., in press). A return map of the response sequence of CA1 pyramidal cells was well approximated by a set of contractive affine transformations, where the transformations represent self-organized rules by which the input pattern sequences are encoded. These findings provide direct evidence that the information of temporal sequences generated in CA3 can be self-similarly represented in the membrane potentials of CA1 pyramidal cells.
RIES, Hokkaido Univ., Japan
doi:10.1016/j.neures.2009.09.167
O2-I4-3 Trade-off between cell-to-cell synchronization and trial-totrial reliability in recurrent networks of neurons Jun-nosuke Teramae, Tomoki Fukai Neural Circuit Theory, Brain Science Institute, RIKEN, Saitama, Japan Reliable information processing in the brain requires that neurons can generate a precise and reliable spike trains in response to injecting currents. Reliable responses to repeated applications of a fluctuating current have been measured by in vitro experiments of isolated cortical neurons. However, these studies are still incomplete as they only treated reliability of single neurons and did not treat networks of neurons. Neurons in the network can show synchronous activities. It remains unclear how correlation among cortical neurons affects trial-to-trial variability of spike trains. Here, combining a theory of stochastic processes and numerical simulation using realistic neuron models, we study the response reliability of networks of neurons. The result shows clear trade-off between synchrony among neurons and their response reliability; the reliability always decreases with increasing cell-to-cell synchrony. The result is consistent with recent experimental findings on attention and may explain why strong synchrony was not observed in the cortex. doi:10.1016/j.neures.2009.09.168
O2-I4-4 Theta oscillations provide temporal windows for local circuit computation in the entorhinal-hippocampal loop Kenji Mizuseki, Gyorgy Buzsaki Rutgers University, USA Theta oscillations are believed to play an important role in the coordination of neuronal firing in the entorhinal (EC)-hippocampal system but the underlying mechanisms are not known. We simultaneously recorded from neurons in all regions of the EC-hippocampal loop and examined their temporal (theta phase) relationships. While population synchrony of upstream regions correctly predicted the timing of current sinks in target downstream layers, the temporal delays between population activities in successive anatomical stages were longer (typically by a half theta cycle) than expected from axon conduction velocities and synaptic integration of feedforward excitatory inputs. These findings demonstrate that during theta oscillations most spikes are generated by local circuit interactions, reflecting a considerable degree of computational independence in subdivisions of the EC-hippocampal loop. We hypothesize that EC inputs select a subset of hippocampal neurons at the late phase of the theta cycle and the interactions among the selected members sustain activity during subsequent cycles. doi:10.1016/j.neures.2009.09.169
O2-I5-1 Mesh electrode arrays applied to record visual cortical activities in hooded rats Hirohito Sawahata 1 , Haruo Toda 1 , Takafumi Suzuki 2 , Isao Hasegawa 1 1
Further reading Fukushima, et al., 2007. Cogn. Neurodyn. 1, 169. Kuroda et al. Cogn. Neurodyn., in press. doi:10.1016/j.neures.2009.09.166
Department Physiol., Niigata University, Niigata, Japan; Sci. Tech., Tokyo University, Tokyo, Japan
2
Grad. Sch. Inf.
To record the electrocorticograms (ECoGs) from a wide area of cortical surface, we have newly designed a flexible, mesh electrode array. It consists of 36 gold recording sites within a very thin Parylene-C mesh. The recording sites are aligned in a 6 × 6 square grid on the mesh with 1 mm spacing. An anesthetized hooded (Long-
Abstracts
the location of the FOE. A computational model of saliency-based attention that includes the FOE well describes observers scan paths. Our study has implications for filming and for everyday life.
O2-I4-2 Cantor coding in a model of hippocampal CA1 Yutaka Yamaguti, Shigeru Kuroda, Ichiro Tsuda
doi:10.1016/j.neures.2009.09.163
Based on the theory that the hippocampus is responsible for formation of episodic memory, we proposed a mathematical model for the hippocampus. The Cantor coding hypothesis in CA1 has been proposed, which provides a scheme for encoding temporal sequences of events. Here, in order for investigating the Cantor coding in detail, we constructed a model for the CA1 network which consists of conductancebased model neurons. We examined dependencies of output patterns of CA1 neurons on input temporal sequences of spatial patterns produced by CA3. It was shown that the output patterns of CA1 were hierarchically clustered in a self-similar manner according to the similarity of input time-series. Furthermore, linear discriminant analysis clarified that the performance of the Cantor coding sensitively depends on the input strength and the time interval of input sequence. NMDA synaptic connections enhanced the performance of the coding of input sequences with long (100–200 mses) intervals. These results suggest that Cantor set-like structure encoding time-series is formed in state space of neural dynamics.
O2-I3-3 BOLD fMRI dynamics in monkeys reflects spatial decisions in free-choice and reward context tasks Igor Kagan, Melanie Wilke, Richard A. Andersen Caltech, USA We investigated voluntary decision-making and motor planning in monkeys with time-resolved event-related high-field fMRI. We previously found strong contralateral tuning of frontoparietal BOLD activity during a memory saccade task. Here we used a spatial decision task to assess the dynamics of response selection. Two equally rewarded targets were presented and after a delay monkeys could select either location. The contralateral build-up of BOLD activity during the delay reflected the monkeys’ choices, and different areas signaled the decision at different times. Internal spatial preferences were reflected in the inter-hemispheric imbalance of left/right spatial representations. These patterns imply mutually suppressive interactions between two response options. Next, we introduced a reward context associated with target colors. The behavioral preference for large expected rewards was paralleled by a stronger delay period activity, supporting prospective evaluation of goal-directed actions. We suggest a common mechanism integrating internal and external variables during oculomotor decisions. doi:10.1016/j.neures.2009.09.164
O2-I3-4 Spatial working memory after V1 lesion Kana Takaura 1,2 , Masatoshi Yoshida 1,2 , Tadashi Isa 1,2,3 1
Sch. Life Sci., Grad. University Adv. Stud., Hayama, Japan; Dev. Physiol., NIPS, Japan; 3 CREST, Kawaguchi, Japan
2
Department
Blindsight is a phenomenon in which patients with damages to the primary visual cortex (V1) exhibit residual ability of visuomotor transformation without visual awareness. Visual awareness has been proposed to be tightly linked to working memory. Previously we reported that monkeys with unilateral V1 lesion, which have been used as an animal model of the blindsight, can retain spatial memory of cues briefly presented for at least 2 seconds. To investigate neural mechanisms for spatial memory in the visual field affected by lesion, we recorded neuronal activities in the superior colliculus (SC). We found that most of the neurons in the ipsilesional SC exhibited sustained activities throughout the delay period when cues were presented inside the receptive fields. In naive brain, such kind of activity has been reported in the cerebral cortex. Our results challenge the prevailing hypothesis about the relationship between visual awareness and working memory, and indicate that the SC could compensate for some functional roles of the cerebral cortices after cerebral damages. doi:10.1016/j.neures.2009.09.165
O2-I4-1 Iterated function systems in the hippocampal CA1 Shigeru Kuroda 1 , Yasuhiro Fukushima 2 , Yutaka Yamaguti 1 , Minoru Tsukada 2 , Ichiro Tsuda 1,3 1
RIES, Hokkaido Univ., Hokkaido, Japan; 2 Brain Sci. Inst., Tamagawa Univ., Tokyo, Japan; 3 Dept. Sci., Hokkaido Univ., Hokkaido, Japan
How does the information of spatiotemporal sequence stemming from the hippocampal CA3 area affect the postsynaptic membrane potentials of the hippocampal CA1 neurons? In (Fukushima et al., 2007), we observed hierarchical clusters of the distribution of membrane potentials of CA1 neurons, arranged according to the history of input sequences. In this study, to clarify the dynamical mechanism generating such a hierarchical distribution, we investigated the recording data using return map analysis (Kuroda et al., in press). A return map of the response sequence of CA1 pyramidal cells was well approximated by a set of contractive affine transformations, where the transformations represent self-organized rules by which the input pattern sequences are encoded. These findings provide direct evidence that the information of temporal sequences generated in CA3 can be self-similarly represented in the membrane potentials of CA1 pyramidal cells.
RIES, Hokkaido Univ., Japan
doi:10.1016/j.neures.2009.09.167
O2-I4-3 Trade-off between cell-to-cell synchronization and trial-totrial reliability in recurrent networks of neurons Jun-nosuke Teramae, Tomoki Fukai Neural Circuit Theory, Brain Science Institute, RIKEN, Saitama, Japan Reliable information processing in the brain requires that neurons can generate a precise and reliable spike trains in response to injecting currents. Reliable responses to repeated applications of a fluctuating current have been measured by in vitro experiments of isolated cortical neurons. However, these studies are still incomplete as they only treated reliability of single neurons and did not treat networks of neurons. Neurons in the network can show synchronous activities. It remains unclear how correlation among cortical neurons affects trial-to-trial variability of spike trains. Here, combining a theory of stochastic processes and numerical simulation using realistic neuron models, we study the response reliability of networks of neurons. The result shows clear trade-off between synchrony among neurons and their response reliability; the reliability always decreases with increasing cell-to-cell synchrony. The result is consistent with recent experimental findings on attention and may explain why strong synchrony was not observed in the cortex. doi:10.1016/j.neures.2009.09.168
O2-I4-4 Theta oscillations provide temporal windows for local circuit computation in the entorhinal-hippocampal loop Kenji Mizuseki, Gyorgy Buzsaki Rutgers University, USA Theta oscillations are believed to play an important role in the coordination of neuronal firing in the entorhinal (EC)-hippocampal system but the underlying mechanisms are not known. We simultaneously recorded from neurons in all regions of the EC-hippocampal loop and examined their temporal (theta phase) relationships. While population synchrony of upstream regions correctly predicted the timing of current sinks in target downstream layers, the temporal delays between population activities in successive anatomical stages were longer (typically by a half theta cycle) than expected from axon conduction velocities and synaptic integration of feedforward excitatory inputs. These findings demonstrate that during theta oscillations most spikes are generated by local circuit interactions, reflecting a considerable degree of computational independence in subdivisions of the EC-hippocampal loop. We hypothesize that EC inputs select a subset of hippocampal neurons at the late phase of the theta cycle and the interactions among the selected members sustain activity during subsequent cycles. doi:10.1016/j.neures.2009.09.169
O2-I5-1 Mesh electrode arrays applied to record visual cortical activities in hooded rats Hirohito Sawahata 1 , Haruo Toda 1 , Takafumi Suzuki 2 , Isao Hasegawa 1 1
Further reading Fukushima, et al., 2007. Cogn. Neurodyn. 1, 169. Kuroda et al. Cogn. Neurodyn., in press. doi:10.1016/j.neures.2009.09.166
Department Physiol., Niigata University, Niigata, Japan; Sci. Tech., Tokyo University, Tokyo, Japan
2
Grad. Sch. Inf.
To record the electrocorticograms (ECoGs) from a wide area of cortical surface, we have newly designed a flexible, mesh electrode array. It consists of 36 gold recording sites within a very thin Parylene-C mesh. The recording sites are aligned in a 6 × 6 square grid on the mesh with 1 mm spacing. An anesthetized hooded (Long-