Relation of olfactory EEG to behavior: Spatial analysis.

Freeman, Walter J.; Baird, Bill

doi:10.1037/0735-7044.101.3.393

Cited by 167 publications

(116 citation statements)

References 17 publications

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“…A2.04), for which the criterion was the concave-upward inflection in the spatial PSD X at high frequency ( Fig. A1.02, B, Appendix 1.2, Part 1, Freeman and Baird, 1987;Barrie, Freeman and Lenhart, 1996). Spatial filtering imposed structure on the data from the 8x8 arrays, so that care had to be taken to study by use of randomized controls the degree to which structuring occurred (Appendix 2.3).…”

Section: Justification Of the Choice Of The Phase Cone As The Spatialmentioning

confidence: 98%

“…A1.12 in Part 1) without impediment by sulci in under a quarter cycle duration of a gamma wave . This time frame is as rapid as the re-set of phase over the much smaller rabbit olfactory bulb (Freeman and Baird, 1987).…”

Section: Sudden Changes In Eeg Occur Simultaneously Over Large Distanmentioning

confidence: 98%

“…In the 2-dimensional spatial domain the simplest options for the basis functions to measure the phase gradient were a plane, a radially symmetric bivariate Gaussian density function, or a circular cone (Freeman and Baird, 1987). Each basis function was fitted to the phase data by nonlinear regression with the criterion of minimizing least squares residuals (Appendix 2.2).…”

Section: Justification Of the Choice Of The Phase Cone As The Spatialmentioning

confidence: 99%

“…Each basis function was fitted to the phase data by nonlinear regression with the criterion of minimizing least squares residuals (Appendix 2.2). Preliminary results from fitting the same olfactory test data with all three basis functions (Freeman and Baird, 1987) showed that the cone gave the smallest % residuals and the simplest interpretation of phase velocity as an expression of axonal conduction velocity in m/s (see equation 4 in Section 2.4). All of these simple basis functions had the drawback that most 8x8 matrices of numbers could be fitted, whether or not they had structure, giving parameters that might indicate structure where none existed.…”

Section: Justification Of the Choice Of The Phase Cone As The Spatialmentioning

confidence: 99%

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Origin, structure, and role of background EEG activity. Part 2. Analytic phase

Freeman

2004

Clinical Neurophysiology

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Objective: To explain spontaneous EEG through measurements of spatiotemporal patterns of phase among beta-gamma oscillations.Methods: High-density 8x8 intracranial arrays were fixed over sensory cortices of rabbits. EEGs were spatially low pass filtered, temporally band pass filtered and segmented in overlapping windows stepped at 2 ms. Phase was measured with the cosine as the temporal basis function, using both Fourier and Hilbert transforms to compensate for their respective limitations. Spatial patterns in 2-D phase surfaces were measured with the geometric form of the cone as the spatial basis function.Results: Two fundamental state variables were measured at each digitizing step in the 64 EEGs: the rate of change in phase with time (frequency) and the rate of change in phase with distance (gradient). The parameters of location, diameter, duration, and phase velocity of the cone of phase were derived from these two state variables. Parameter distributions including recurrence intervals extending into the low theta range were fractal; the mean values varied with window duration and interelectrode distance. Conclusions:The formation of spatial amplitude patterns began with phase transitions that were documented by phase discontinuities and phase cones. The multiplicity of overlapping cones indicated that sensory neocortices maintained a scale-free state of self-organized criticality (SOC) in each hemisphere as the basis for its rapid integration of sensory input with prior learning stored in cortical synaptic webs. Further evidence came from the fractal properties of the phase parameters and the self-similarity of phase patterns in the ms/mm to m/s ranges.Significance: These EEG data suggest that neocortical dynamics is analogous to the dynamics of self-stabilizing systems, such as a sand pile that maintains its critical angle by avalanches, and a pan of boiling water that maintains its critical temperature by bubbles that release heat. Betagamma oscillations stem from the ability of neocortex to maintain its stability under continuous sensory bombardment. Modeling implies that the critical parameter of neocortex (analogous to angle of repose or temperature) is the mean firing rates of neurons that are homeostatically regulated by refractory periods everywhere at all times in cortex. The advantage of SOC in perception may be the ability it gives neocortex to generate instantaneous global phase transitions (avalanches, bubbles) large enough to include the multiple sensory areas that are necessary to form Gestalts (multisensory percepts).Background EEG analytic phase 3Walter J Freeman

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Section: Justification Of the Choice Of The Phase Cone As The Spatialmentioning

confidence: 98%

Section: Sudden Changes In Eeg Occur Simultaneously Over Large Distanmentioning

confidence: 98%

Section: Justification Of the Choice Of The Phase Cone As The Spatialmentioning

confidence: 99%

Section: Justification Of the Choice Of The Phase Cone As The Spatialmentioning

confidence: 99%

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Origin, structure, and role of background EEG activity. Part 2. Analytic phase

Freeman

2004

Clinical Neurophysiology

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“…A1.02, B). Spatial filtering (Freeman and Baird, 1987, Freeman and Barrie, 2000 was by applying the filter without Hamming to the 8 digitized EEG amplitudes at each time point in each column and row. An exponential low pass filter was applied separately to the real and imaginary amplitudes (Gonzalez and Wintz, 1977) with the factor for attenuation, G(f x ), ranging from 1 and 0 with increasing spatial frequency, f x :…”

Section: Appendix 11 Temporal Spectral Analysis Using Psd T and Banmentioning

confidence: 99%

Origin, structure, and role of background EEG activity. Part 1. Analytic amplitude

Freeman

2004

Clinical Neurophysiology

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Objective: To explain the neural mechanisms of spontaneous EEG by measuring the spatiotemporal patterns of synchrony among beta-gamma oscillations during perception. Methods: EEGs were measured from 8x8 (5.6x5.6 mm) arrays fixed on the surfaces of primary sensory areas in rabbits that were trained to discriminate visual, auditory or tactile conditioned stimuli (CSs) eliciting conditioned responses (CRs). EEG preprocessing was by (i) band pass filtering to extract the beta-gamma range (deleting theta-alpha); (ii) low-pass spatial filtering (not high-pass Laplacians used for localization), (iii) spatial averaging (not time averaging used for evoked potentials), and (iv) close spacing of 64 electrodes for simultaneous recording in each area (not sampling single signals from several areas); (v) novel algorithms were devised to measure synchrony and spatial pattern stability by calculating variances among patterns in 64-space derived from the 8x8 arrays (not by fitting equivalent dipoles). These methodological differences are crucial for the proposed new perspective on EEG. Results: Spatial patterns of beta-gamma EEG emerged following sudden jumps in cortical activity called "state transitions". Each transition began with an abrupt phase re-setting to a new value on every channel, followed sequentially by re-synchronization, spatial pattern stabilization, and a dramatic increase in pattern amplitude. State transitions recurred at varying intervals in the theta range. A novel parameter was devised to estimate the perceptual information in the betagamma EEG, which disclosed 2 to 4 patterns with high information content in the CS-CR interval on each trial; each began with a state transition and lasted ~.1 s. Conclusions:The function of each primary sensory neocortex was discontinuous; discrete spatial patterns occurred in frames like those in cinema. The frames before and after the CS-CR interval had low content. Significance: Derivation and interpretation of unit data in studies of perception might benefit from using multichannel EEG recordings to define distinctive epochs that are demarcated by state transitions of neocortical dynamics in the CS-CR intervals, particularly in consideration of the possibility that EEG may reveal recurring episodes of exchange and sharing of perceptual information among multiple sensory cortices. Simultaneously recorded, multichannel betagamma EEG might assist in the interpretation of images derived by fMRI, since high betagamma EEG amplitudes imply high rates of energy utilization. The spatial pattern intermittency provides a tag to distinguish gamma bursts from contaminating EMG activity in scalp recording in order to establish beta-gamma recording as a standard clinical tool. Finally, EEG cannot fail to have a major impact on brain theory.Background EEG analytic amplitude 3Walter J Freeman http://sulcus.berkeley.edu/wjf/EG_EEGPart1AnalyticAmplitude.pdf Cover Figure Legend:The EEG shows that neocortex processes information in frames like a cinema. The perceptual content is foun...

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Spatial coding of odorant features in the glomerular layer of the rat olfactory bulb

1998

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In order to determine whether molecular features of odorants are represented spatially in the glomerular layer of the olfactory bulb, we used metabolic mapping of [14C] 2-deoxyglucose uptake in rats exposed to equal vapor concentrations of odorants differing systematically in chemical structure. The odorants were ethyl acetate, ethyl butyrate, isoamyl acetate, and isoamyl butyrate. Statistical analysis of anatomically standardized arrays of uptake revealed that each ester produced a characteristic spatial pattern of activity in the glomerular layer. The patterns were similar in different rats exposed to the same odorant, and their complexity increased with increasing odorant carbon number. This finding suggests that the presence of more potentially recognized molecular features is associated with a greater number of activated receptors. Individual regions of the glomerular layer responded specifically to isoamyl esters, and other regions preferred ethyl esters. Regions of similar specificity occurred in lateral and medial aspects of the bulb, the medial representation being more caudal and ventral than the lateral one. This pattern correlates with projections of olfactory sensory neurons expressing the same putative olfactory receptor gene. The patterns overlapped greatly in the posterolateral and posteromedial glomerular layer, a finding one should predict, given the large overlap in chemical structure across the aliphatic esters. Thus, molecular features appear to be encoded spatially in the glomerular layer, and the identity of the odorant may be determined by a subsequent decoding of the combination of molecular features represented in the glomerular layer.

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Relation of olfactory EEG to behavior: Spatial analysis.

Cited by 167 publications

References 17 publications

Origin, structure, and role of background EEG activity. Part 2. Analytic phase

Origin, structure, and role of background EEG activity. Part 2. Analytic phase

Origin, structure, and role of background EEG activity. Part 1. Analytic amplitude

Spatial coding of odorant features in the glomerular layer of the rat olfactory bulb

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