scholarly journals Analysis of Spatial Patterns of Phase in Neocortical Gamma EEGs in Rabbit

2000 ◽  
Vol 84 (3) ◽  
pp. 1266-1278 ◽  
Author(s):  
Walter J. Freeman ◽  
John M. Barrie
Keyword(s):  
Spatial Coherence ◽  
Sensory Information ◽  
State Transitions ◽  
Wave Form ◽  
Conditioned Stimuli ◽  
Phase Gradient ◽  
Gamma Range ◽  
Sensory Cortices ◽  
Half Power

Arrays of 64 electrodes (8 × 8, 7 × 7 mm) were implanted epidurally on the surface of the visual, auditory or somatosensory cortex of rabbits trained to discriminate conditioned stimuli in the corresponding modality. The 64 electroencephalographic (EEG) traces at all times displayed a high degree of spatial coherence in wave form, averaging >90% of the variance in the largest principal components analysis component. The EEGs were decomposed with the fast Fourier transform (FFT) to give the spatial distributions of amplitude and phase modulation (AM and PM) in segments 128 ms in duration. Spatial (2-dimensional) and temporal (1-dimensional) filters were designed to optimize classification of the spatial AM patterns in the gamma range (20–80 Hz) with respect to discriminative conditioned stimuli. No evidence was found for stimulus-dependent classification of the spatial PM patterns. Instead some spatial PM distributions conformed to the pattern of a cone. The location and sign (maximal lead or lag) of the conic apex varied randomly with each recurrence. The slope of the phase gradient varied in a range corresponding to that of the conduction velocities reported of axons to extend parallel to the cortical surfaces. The durations and times of recurrence of the phase cones corresponded to those of the optimally classified spatial AM patterns. The interpretation is advanced that the phase cones are manifestations of state transitions in the mesoscopic dynamics of sensory cortices by which the intermittent AM patterns are formed. The phase cones show that the gamma EEG spatial coherence is not due to volume conduction from a single deep-lying dipole generator nor to activity at the site of the reference lead on monopolar recording. The random variation of the apical sign shows that gamma AM patterns are self-organized and are not imposed by thalamic pacemakers. The half-power radius of the phase gradient provides a useful measure of the soft boundary condition for the formation and read-out of cooperative cortical domains responsible for binding sensory information into the context of prior experience in the process of perception.

A Neurobiological Theory of Meaning in Perception Part II: Spatial Patterns of Phase in Gamma EEGs from Primary Sensory Cortices Reveal the Dynamics of Mesoscopic Wave Packets

2003 ◽  
Vol 13 (09) ◽  
pp. 2513-2535 ◽  
Author(s):  
Walter J. Freeman
Keyword(s):  
Spatial Patterns ◽  
Neural Activity ◽  
Action Potentials ◽  
Wave Packets ◽  
Power Level ◽  
Sensory Information ◽  
State Transitions ◽  
Electrode Arrays ◽  
Phase Gradient ◽  
Information Carrier

Domains of cooperative neural activity called "wave packets" have been discovered in the visual, auditory, and somatomotor cortices of rabbits that were trained to discriminate conditioned stimuli in these modalities. Each domain forms by a first order state transition, which strongly resembles a phase transition from vapor to liquid. In this view, raw sense data injected into cortex by sensory axons drive cortical action potentials in swarms like water molecules in steam. The increased activity destabilizes the cortex. Within 3 to 7 milliseconds of transition onset, the activity binds together into a state resembling a scintillating rain drop, which lasts ~80 to 100 milliseconds, then dissolves. Wave packets form at rates of 2 to 7/second in all sensory areas, overlapping in space and time. Results of sensory information processing are seen in spatial patterns of amplitude modulation (AM) of wave packets with carrier waves in the gamma range (20 to 80 Hz in rabbits). The AM patterns correspond to categories of CSs that the rabbits can discriminate. The patterns are found in electroencephalographic (EEG) potentials generated by dendrites and recorded with high-density electrode arrays. The state transitions by which AM patterns form are manifested in the spatial pattern of phase modulation (PM), which have the radial symmetry of a cone. The apex of a PM cone marks the site of nucleation of an AM pattern. The phase gradient gives a soft boundary condition, where the axonal delay in spread gives sufficient phase dispersion to reach the half-power level. The size of the wave packets (10 to 30 mm in diameter in rabbits) is determined largely by the conduction velocities of intracortical axons through which the neural cooperation is maintained. The findings show that significant cortical activity takes the form of mesoscopic interactions of millions of neurons in broad areas of cortex, which are more clearly detected in graded dendritic potentials than in action potentials. The distinction is analogous to the difference between statistical mechanical and thermodynamic descriptions of particle behavior. Both types of neural activity show spatial and temporal discontinuities but at distinctive scales of microns and msec versus mm and tenths of a second. The aim of measurement here is to establish the wave packet as the information carrier at the mesoscopic level in brain dynamics, comparable to the role of the action potential as the information carrier at the microscopic level in neuron dynamics.

scholarly journals Fine Temporal Resolution of Analytic Phase Reveals Episodic Synchronization by State Transitions in Gamma EEGs

2002 ◽  
Vol 87 (2) ◽  
pp. 937-945 ◽  
Author(s):  
Walter J. Freeman ◽  
Linda J. Rogers
Keyword(s):  
Time Series ◽  
Spatial Patterns ◽  
Temporal Resolution ◽  
Phase Locking ◽  
State Transitions ◽  
Phase Lag ◽  
Gamma Range ◽  
Sensory Cortices ◽  
Fixed Distribution ◽  
Theta Range

The analytic signal given by the Hilbert transform applied to an electroencephalographic (EEG) trace is a vector of instantaneous amplitude and phase at the temporal resolution of the digitizing interval (here 2 ms). The transform was applied after band-pass filtering for extracting the gamma band (20–80 Hz in rabbits) to time series from up to 64 EEG channels recorded simultaneously from high-density arrays giving spatial “windows” of 4 × 4 to 6 × 6 mm onto the visual, auditory, or somatosensory cortical surface. The time series of the analytic phase revealed phase locking for brief time segments in spatial patterns of nonzero phase values from multiple EEG that was punctuated by episodic phase decoherence. The derivative of the analytic phase revealed spikes occurring not quite simultaneously (within ±4 ms) across arrays aperiodically at mean rates in and below the theta range (3–7 Hz). Two measures of global synchronization over a group of channels were derived from analytic phase differences between pairs of channels on the same area of cortex. One was a synchronization index expressing phase locking. The other was a decoherence index estimating the variance in phase among multiple channels. Spectral analyses of the indices indicated that decoherence events recurred aperiodically at rates in and below the theta range of the EEGs. The results provide support for the hypothesis that neurons in mesoscopic neighborhoods in sensory cortices self-organize their activity by synaptic interactions into wave packets that have spatial patterns of amplitude (AM) and phase (PM) modulation of their spatially coherent carrier waves in the gamma range and that form and dissolve aperiodically at rates in and below the theta range. Each AM pattern is formed by a nonlinear state transition in the cortical dynamics, as shown by spikes in the derivative. Phase locking within each PM pattern is not at zero phase lag but over a fixed distribution of phase values that is consistent with the radially symmetric phase gradients already reported called “phase cones” detected by Fourier-based methods. The insight is suggested that sensory cortices are bistable comparably to cardiac dynamics, with a diastolic state that accepts sensory input and an abrupt transition to a systolic state that transmits perceptual output. Further support for this inference will require improvements in methods for temporal resolution of the times of onset of spatial patterns of phase modulation.

scholarly journals Towards Odor-Sensitive Mobile Robots

2018 ◽  
pp. 244-263 ◽  
Author(s):  
Javier Monroy ◽  
Javier Gonzalez-Jimenez
Keyword(s):  
Mobile Robots ◽  
Gas Sensing ◽  
Laser Scanner ◽  
Sensory Information ◽  
Current Status ◽  
Electronic Noses ◽  
Gas Dispersion ◽  
Gas Source ◽  
Sparse Measurements

Out of all the components of a mobile robot, its sensorial system is undoubtedly among the most critical ones when operating in real environments. Until now, these sensorial systems mostly relied on range sensors (laser scanner, sonar, active triangulation) and cameras. While electronic noses have barely been employed, they can provide a complementary sensory information, vital for some applications, as with humans. This chapter analyzes the motivation of providing a robot with gas-sensing capabilities and also reviews some of the hurdles that are preventing smell from achieving the importance of other sensing modalities in robotics. The achievements made so far are reviewed to illustrate the current status on the three main fields within robotics olfaction: the classification of volatile substances, the spatial estimation of the gas dispersion from sparse measurements, and the localization of the gas source within a known environment.

STUDIES OF DISTAL COLONIC MOTILITY IN CHILDREN

PEDIATRICS ◽  
1956 ◽  
Vol 17 (6) ◽  
pp. 820-833
Author(s):  
Murray Davidson ◽  
Marvin H. Sleisenger ◽  
Thomas P. Almy ◽  
Samuel Z. Levine
Keyword(s):  
Ulcerative Colitis ◽  
Bowel Movement ◽  
Colonic Motility ◽  
Distal Colon ◽  
Wave Form ◽  
Spontaneous Bowel Movement ◽  
Normal Individuals ◽  
Iced Water ◽  
Wave Forms

A characteristic propulsive wave, previously reported in adults with ulcerative colitis, has been found in infants with acute diarrhea but not in children with ulcerative colitis. The reasons for this are discussed. The induction of propulsive wave forms in normal individuals by administration of magnesium sulfate orally is described and attention is called to its application to therapeutic studies. The relation of this wave form to propulsion of fecal contents and defecation and its role in the production of abdominal discomfort are considered. Observed variations in the responses of individual children to subcutaneous injection of Mecholyl®, to oral administration of iced water, and to rectal distention may explain innate differences in susceptibility to the development of colonic symptoms in different children. A classification of wave forms from the distal colon based on current concepts of their probable physiologic significance is offered. A tracing from the distal colon in a child having a spontaneous bowel movement is presented and commented on.

scholarly journals Classification of auditory selective attention using spatial coherence and modular attention index

2018 ◽  
Vol 166 ◽  
pp. 107-113 ◽  
Author(s):  
Ana Paula de Souza ◽  
Quenaz B. Soares ◽  
Leonardo B. Felix ◽  
Eduardo M.A.M. Mendes
Keyword(s):  
Selective Attention ◽  
Spatial Coherence ◽  
Auditory Selective Attention

Detection and classification of sensory information from acute spinal cord recordings

2006 ◽  
Vol 53 (8) ◽  
pp. 1715-1719 ◽  
Author(s):  
J.F. Borisoff ◽  
L.T. McPhail ◽  
J.T.W. Saunders ◽  
G.E. Birch ◽  
M.S. Ramer
Keyword(s):  
Spinal Cord ◽  
Sensory Information

A NEUROBIOLOGICAL THEORY OF MEANING IN PERCEPTION PART IV: MULTICORTICAL PATTERNS OF AMPLITUDE MODULATION IN GAMMA EEG

2003 ◽  
Vol 13 (10) ◽  
pp. 2857-2866 ◽  
Author(s):  
WALTER J. FREEMAN ◽  
BRIAN C. BURKE
Keyword(s):  
Amplitude Modulation ◽  
Euclidean Distance ◽  
Time Windows ◽  
Gamma Activity ◽  
Moving Window ◽  
Conditioned Stimuli ◽  
Root Mean Square Amplitude ◽  
Gamma Range ◽  
Sensory Area ◽  
Multisensory Convergence

The aim of this study is to find spatial patterns of EEG amplitude in the gamma range of the EEGs from multiple sensory and limbic areas that demonstrate multisensory convergence and integration. 64 electrodes spread in small arrays were fixed on or in the olfactory, visual, auditory, somatomotor and entorhinal areas of cats and rabbits. The subjects were trained to discriminate 2 visual and then 2 auditory conditioned stimuli, one reinforced (CS+), the other not (CS-). A moving window was applied to the 6-s records from 20 trials of each CS including a 3-s prestimulus control (CS0). The root mean square amplitude was calculated for each signal in the gamma range, so each window gave a point in 64-space. EEG patterns from the CS+, CS- and CS0 conditions gave 3 clusters of points in 64-space. The Euclidean distance of each point to the nearest center of gravity of a cluster served for classification and estimation of the probability of correct classification. The results showed that the gamma activity (35–60 Hz in cats, 20–80 Hz in rabbits) in all five areas formed global patterns of amplitude modulation (AM) in time windows lasting ~100–200 ms and recurring at 2–4 Hz, which were correctly classified above chance levels (p<0.01). All areas contributed information to the AM patterns that served to classify the EEG epochs in the windows with respect to the conditioned stimuli. In conclusion, multisensory integration took place over the greater part of the hemisphere, despite lack of phase coherence among the gamma waves. The integration occurred rapidly enough that, within 300 ms of CS onset, activity in every sensory area was modified by what took place in every other sensory area.

Remote acoustic classification of marine sediments with application to offshore Newfoundland

1983 ◽  
Vol 20 (7) ◽  
pp. 1195-1211 ◽  
Author(s):  
N. A. Cochrane ◽  
A. D. Dunsiger
Keyword(s):  
Marine Sediments ◽  
Classification Scheme ◽  
Spatial Coherence ◽  
Unconsolidated Sediments ◽  
Limited Area ◽  
Acoustic Source ◽  
Shallow Marine Sediments ◽  
Correlation Properties ◽  
Acoustic Classification

Shallow marine sediments can be remotely classified by the spatial correlation properties of their seismic reflection signatures provided one uses a highly repetitive broadband acoustic source. A classification scheme defined by three spatial coherence parameters is shown capable of automatically differentiating between several formations of unconsolidated sediments in a limited area of offshore Newfoundland. The consistency and generality of the technique are explored and comparisons with standard echogram interpretation are made.

scholarly journals Evaluative Judgment Across Domains

2021 ◽  
Author(s):  
Ana Clemente ◽  
Marcus Thomas Pearce ◽  
Martin Skov ◽  
Marcos Nadal
Keyword(s):  
Sensory Information ◽  
Openness To Experience ◽  
Fundamental Aspect ◽  
Evaluative Judgment ◽  
Evaluative Judgments ◽  
Individual Traits ◽  
Sensory Modalities ◽  
Sensory Cortices ◽  
The Individual ◽  
Reward Circuit

Evaluative judgment—i.e., assessing to what degree a stimulus is liked or disliked—is a fundamental aspect of cognition, facilitating comparison and choosing among alternatives, deciding, and prioritizing actions. Neuroimaging studies have shown that evaluative judgment involves the projection of sensory information to the reward circuit. To investigate whether evaluative judgments are based on modality-specific or modality-general attributes, we compared the extent to which balance, contour, symmetry, and complexity affect liking responses in the auditory and visual modalities. We found no significant correlation for any of the four attributes across sensory modalities, except for contour. This suggests that evaluative judgments primarily rely on modality-specific sensory representations elaborated in the brain’s sensory cortices and relayed to the reward circuit, rather than abstract modality-general representations. The individual traits art experience, openness to experience, and desire for aesthetics were associated with the extent to which design or compositional attributes influenced liking, but inconsistently across sensory modalities and attributes, also suggesting modality-specific influences.

scholarly journals Afferent connections of the primary somatosensory cortex of the mouse for contextual and multisensory processing

2019 ◽  
Author(s):  
Ian Omer Massé ◽  
Sohen Blanchet-Godbout ◽  
Gilles Bronchti ◽  
Denis Boire
Keyword(s):  
Somatosensory Cortex ◽  
Multisensory Processing ◽  
Sensory Information ◽  
Primary Somatosensory Cortex ◽  
Thalamic Nuclei ◽  
Descending Pathways ◽  
Afferent Connections ◽  
Barrel Field ◽  
Anatomical Basis ◽  
Sensory Cortices

AbstractSensory information is conveyed from peripheral receptors through specific thalamic relays to primary areas of the cerebral cortex. Information is then routed to specialized areas for the treatment of specific aspects of the sensory signals and to multisensory associative areas. Information processing in primary sensory cortices is influenced by contextual information from top-down projections of multiple cortical motor and associative areas as well as areas of other sensory modalities and higher order thalamic nuclei. The primary sensory cortices are thus located at the interface of the ascending and descending pathways. The theory of predictive coding implies that the primary areas are the site of comparison between the sensory information expected as a function of the context and the sensory information that comes from the environment. To better understand the anatomical basis of this model of sensory systems we have charted the cortical and subcortical afferent inputs in the ipsilateral and contralateral hemispheres of the primary somatosensory cortex of adult C57Bl/6 mice. Iontophoretic injections of the b-fragment of cholera toxin were performed inside the mystacial caudal barrel field, more rostral barrel field and somatosensory cortex outside the barrel field to test the hypothesis that differences exist between these three parts and to compare their projections to the subnetworks built from the Mouse Connectome Project data. The laminar distribution of retrogradely labeled cell bodies was used to classify the projections as feedback, feedforward or lateral. Layer indices range between −1 and 1, indicating feedback and feedforward connections respectively. The primary somatosensory cortex and the barrel field have afferent connections with somatosensory areas, non-somatosensory primary sensory areas, multisensory, motor, associative, and neuromodulatory areas. The caudal part of the barrel field displays different and more abundant cortical and subcortical connections compared to the rest of the primary somatosensory cortex. Layer indices of cortical projections to the primary somatosensory cortex and the barrel field were mainly negative and very similar for ipsilateral and contralateral projections. These data demonstrate that the primary somatosensory cortex receives sensory and non-sensory information from cortical and subcortical sources.

Sign in / Sign up

Export Citation Format

Share Document