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Behavioral/Systems/Cognitive Brain Oscillations Control Timing of Single-Neuron Activity in Humans
"... Agrowing body of animal research suggests that neurons represent information not only in terms of their firing rates but also by varying the timing of spikes relative to neuronal oscillations. Although researchers have argued that this temporal coding is critical in human memory and perception, no s ..."
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Agrowing body of animal research suggests that neurons represent information not only in terms of their firing rates but also by varying the timing of spikes relative to neuronal oscillations. Although researchers have argued that this temporal coding is critical in human memory and perception, no supporting data from humans have been reported. This study provides the first analysis of the temporal relationship between brain oscillations and single-neuron activity in humans. Recording from 1924 neurons, we find that neuronal activity in various brain regions increases at specific phases of brain oscillations. Neurons inwidespread brain regionswere phase locked tooscillations in the theta- (4–8Hz)andgamma- (30–90Hz) frequencybands. Inhippocampus,phase lockingwasprevalent in thedelta-(1–4 Hz) and gamma-frequency bands. Individual neurons were phase locked to various phases of theta and delta oscillations, but they only were active at the trough of gamma oscillations. These findings provide support for the temporal-coding hypothesis in humans. Specifically, they indicate that theta and delta oscillations facilitate phase coding and that gamma oscillations help to decode combina-tions of simultaneously active neurons. Key words: phase locking; theta; gamma; intracranial EEG; navigation; local field potential
Neuron Article Theta Oscillations Provide Temporal Windows for Local Circuit Computation
"... Theta oscillations are believed to play an important role in the coordination of neuronal firing in the ento-rhinal (EC)-hippocampal system but the underlying mechanisms are not known. We simultaneously re-corded from neurons in multiple regions of the EC-hippocampal loop and examined their temporal ..."
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Theta oscillations are believed to play an important role in the coordination of neuronal firing in the ento-rhinal (EC)-hippocampal system but the underlying mechanisms are not known. We simultaneously re-corded from neurons in multiple regions of the EC-hippocampal loop and examined their temporal rela-tionships. Theta-coordinated synchronous spiking of EC neuronal populations predicted the timing of current sinks in target layers in the hippocampus. However, the temporal delays between population activities in successiveanatomical stageswere longer (typically by a half theta cycle) than expected from axon conduction velocities and passive synaptic inte-gration of feed-forward excitatory inputs. We hypoth-esize that the temporal windows set by the theta cycles allow for local circuit interactions and thus a considerable degree of computational indepen-dence in subdivisions of the EC-hippocampal loop.
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All in-text references underlined in blue are linked to publications on ResearchGate, letting you access and read them immediately.
For additional information about this publication click this link.
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SUPPLEMENTARY EXPERIMENTAL PROCEDURES Correlation between Oscillation Amplitude and Interevent Interval
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Learning in human neural networks on microelectrode arrays
, 2006
"... This paper describes experiments involving the growth of human neural networks of stem cells on a MEA (microelectrode array) support. The microelectrode arrays (MEAs) are constituted by a glass support in which a set of tungsten electrodes are inserted. The artificial neural network (ANN) paradigm w ..."
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This paper describes experiments involving the growth of human neural networks of stem cells on a MEA (microelectrode array) support. The microelectrode arrays (MEAs) are constituted by a glass support in which a set of tungsten electrodes are inserted. The artificial neural network (ANN) paradigm was used by stimulating the neurons in parallel with digital patterns distributed on eight channels, then by analyzing a parallel multichannel output. In particular, the microelectrodes were connected following two different architectures, one inspired by the Kohonen’s SOM, the other by the Hopfield network. The output signals have been analyzed in order to evaluate the possibility of organized reactions by the natural neurons. The results show that the network of human neurons reacts selectively to the subministered digital signals, i.e., it produces similar output signals referred to identical or similar patterns, and clearly differentiates the outputs coming from different stimulations. Analyses performed with a special artificial neural network called ITSOM show the possibility to codify the neural responses to different patterns, thus to interpret the signals coming from the network of biological neurons, assigning a code to each output. It is straightforward to verify that identical codes are generated by the neural reactions to similar patterns. Further experiments are to be designed that improve the hybrid neural networks ’ capabilities and to test the possibility of utilizing the organized answers of the neurons in several ways.
The Coherence Theory: A Unifying Framework for Visual Processing
"... This paper presents the preliminary results of an extensive research that aims at finding the powerful mechanisms used by the brain to achieve complex visual processing tasks. We mainly focus on a completely new theory stating that neural processes detect, enhance and infer coherence of the stimulus ..."
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This paper presents the preliminary results of an extensive research that aims at finding the powerful mechanisms used by the brain to achieve complex visual processing tasks. We mainly focus on a completely new theory stating that neural processes detect, enhance and infer coherence of the stimulus and of the neural activity by the means of two mechanisms (correlation and decorrelation). We backup our theory by using the new paradigm of temporal coding and show that simple, yet very powerful effects like synchrony and asynchrony can be estimated in an ultra-rapid fashion. Also we state that our coherence principle can account for Gestalt effects, perceptual grouping, detection of illusory contours, contour integration, border ownership, visual attention and maybe object recognition.
