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RISS 인기검색어
- 검색키워드
- 저자 : Koch Christof (검색결과 4 건)
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Ephaptic coupling of cortical neurons
Anastassiou, Costas A,Perin, Rodrigo,Markram, Henry,Koch, Christof Nature Publishing Group, a division of Macmillan P 2011 NATURE NEUROSCIENCE Vol.14 No.2
The electrochemical processes that underlie neural function manifest themselves in ceaseless spatiotemporal field fluctuations. However, extracellular fields feed back onto the electric potential across the neuronal membrane via ephaptic coupling, independent of synapses. The extent to which such ephaptic coupling alters the functioning of neurons under physiological conditions remains unclear. To address this question, we stimulated and recorded from rat cortical pyramidal neurons in slices with a 12-electrode setup. We found that extracellular fields induced ephaptically mediated changes in the somatic membrane potential that were less than 0.5 mV under subthreshold conditions. Despite their small size, these fields could strongly entrain action potentials, particularly for slow (<8 Hz) fluctuations of the extracellular field. Finally, we simultaneously measured from up to four patched neurons located proximally to each other. Our findings indicate that endogenous brain activity can causally affect neural function through field effects under physiological conditions.
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Transcranial electric stimulation entrains cortical neuronal populations in rats.
Ozen, Simal,Sirota, Anton,Belluscio, Mariano A,Anastassiou, Costas A,Stark, Eran,Koch, Christof,Buzsá,ki, Gyö,rgy The Society 2010 The Journal of neuroscience Vol.30 No.34
<P>Low intensity electric fields have been suggested to affect the ongoing neuronal activity in vitro and in human studies. However, the physiological mechanism of how weak electrical fields affect and interact with intact brain activity is not well understood. We performed in vivo extracellular and intracellular recordings from the neocortex and hippocampus of anesthetized rats and extracellular recordings in behaving rats. Electric fields were generated by sinusoid patterns at slow frequency (0.8, 1.25 or 1.7 Hz) via electrodes placed on the surface of the skull or the dura. Transcranial electric stimulation (TES) reliably entrained neurons in widespread cortical areas, including the hippocampus. The percentage of TES phase-locked neurons increased with stimulus intensity and depended on the behavioral state of the animal. TES-induced voltage gradient, as low as 1 mV/mm at the recording sites, was sufficient to phase-bias neuronal spiking. Intracellular recordings showed that both spiking and subthreshold activity were under the combined influence of TES forced fields and network activity. We suggest that TES in chronic preparations may be used for experimental and therapeutic control of brain activity.</P>
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On-line, voluntary control of human temporal lobe neurons
Cerf, Moran,Thiruvengadam, Nikhil,Mormann, Florian,Kraskov, Alexander,Quiroga, Rodrigo Quian,Koch, Christof,Fried, Itzhak Nature Publishing Group, a division of Macmillan P 2010 Nature Vol.467 No.7319
Daily life continually confronts us with an exuberance of external, sensory stimuli competing with a rich stream of internal deliberations, plans and ruminations. The brain must select one or more of these for further processing. How this competition is resolved across multiple sensory and cognitive regions is not known; nor is it clear how internal thoughts and attention regulate this competition. Recording from single neurons in patients implanted with intracranial electrodes for clinical reasons, here we demonstrate that humans can regulate the activity of their neurons in the medial temporal lobe (MTL) to alter the outcome of the contest between external images and their internal representation. Subjects looked at a hybrid superposition of two images representing familiar individuals, landmarks, objects or animals and had to enhance one image at the expense of the other, competing one. Simultaneously, the spiking activity of their MTL neurons in different subregions and hemispheres was decoded in real time to control the content of the hybrid. Subjects reliably regulated, often on the first trial, the firing rate of their neurons, increasing the rate of some while simultaneously decreasing the rate of others. They did so by focusing onto one image, which gradually became clearer on the computer screen in front of their eyes, and thereby overriding sensory input. On the basis of the firing of these MTL neurons, the dynamics of the competition between visual images in the subject??s mind was visualized on an external display.
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A category-specific response to animals in the right human amygdala
Mormann, Florian,Dubois, Julien,Kornblith, Simon,Milosavljevic, Milica,Cerf, Moran,Ison, Matias,Tsuchiya, Naotsugu,Kraskov, Alexander,Quiroga, Rodrigo Quian,Adolphs, Ralph,Fried, Itzhak,Koch, Christof Nature Publishing Group, a division of Macmillan P 2011 NATURE NEUROSCIENCE Vol.14 No.10
The amygdala is important in emotion, but it remains unknown whether it is specialized for certain stimulus categories. We analyzed responses recorded from 489 single neurons in the amygdalae of 41 neurosurgical patients and found a categorical selectivity for pictures of animals in the right amygdala. This selectivity appeared to be independent of emotional valence or arousal and may reflect the importance that animals held throughout our evolutionary past.
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