RESUMEN
Based on the research of biological olfactory system, a novel chaotic neural network model - K set model has been established. This chaotic neural network can not only simulate the real brain activity of olfactory system, but also present novel chaotic concept for signal processing and pattern recognition. This paper investigates the characteristics of the K set models. Experimental result shows that KIII model can be used for various area of pattern classification efficiently.
RESUMEN
Epidural electrocorticograms over the right auditory cortex (field AI) were measured using implanted 18-channel (3 x 6) electrode arrays in four animals (Mongolian gerbil) trained to discriminate between a rising and a falling frequency modulated tone (frequency range 2-4 kHz). Using a previously introduced classification procedure, transient patterns of cortical activity suitable to discriminate between the rising and the falling modulation were identified. Early (locked to stimulus onset) and late (emerging at variable times poststimulus) patterns could be differentiated. Deletion of increasing numbers of randomly selected electrodes was used to determine a critical density of recording channels required to capture the discriminative power of the early and late patterns. Statistical analysis of the classification revealed a sigmoid dependence of the discriminative power from the number of remaining electrodes with an inflection point at 12 electrodes. The analysis of the minima of the classification statistic revealed that in the early patterns discriminative information was focal on regions corresponding to the tonotopic representation of the stimuli, whereas in late patterns this information seemed to be distributed nonfocally across larger cortical regions. This analysis supports the previous notion of the coexistence of topographically organized activity states related to the physical stimulus features and nontopographically organized states determined largely by intrinsic factors (Ohl et al. 2001).
Asunto(s)
Corteza Auditiva/fisiología , Potenciales Evocados Auditivos/fisiología , Estimulación Acústica , Animales , Aprendizaje Discriminativo , Electrodos Implantados , Gerbillinae , Percepción de la Altura Tonal/fisiología , Factores de TiempoRESUMEN
Humans are able to classify novel items correctly by category; some other animals have also been shown to do this. During category learning, humans group perceptual stimuli by abstracting qualities from similarity relationships of their physical properties. Forming categories is fundamental to cognition and can be independent of a 'memory store' of information about the items or a prototype. The neurophysiological mechanisms underlying the formation of categories are unknown. Using an animal model of category learning, in which frequency-modulated tones are distinguished into the categories of 'rising' and 'falling' modulation, we demonstrate here that the sorting of stimuli into these categories emerges as a sudden change in an animal's learning strategy. Electro-corticographical recording from the auditory cortex shows that the transition is accompanied by a change in the dynamics of cortical stimulus representation. We suggest that this dynamic change represents a mechanism underlying the recognition of the abstract quality (or qualities) that defines the categories.
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Corteza Auditiva/fisiología , Percepción Auditiva/fisiología , Aprendizaje Discriminativo/fisiología , Animales , Electrofisiología , Gerbillinae , Masculino , Modelos Animales , Modelos NeurológicosRESUMEN
The generation of oscillatory activity may be crucial to brain function. The coordination of individual neurons into rhythmic and coherently active populations is thought to result from interactions between excitatory and inhibitory cells mediated by local feedback connections. By using extracellular recording wires and silicon microprobes to measure electrically evoked damped oscillatory responses at the level of neural populations in the entorhinal cortex, and by using current-source density analysis to determine the spatial pattern of evoked responses, we show that the propagation of activity through the cortical circuit and consequent oscillations in the local field potential are dependent upon background neural activity. Pharmacological manipulations as well as surgical disconnection of the olfactory bulb serve to quell the background excitatory input incident to entorhinal cortex, resulting in evoked responses without characteristic oscillations and showing no signs of polysynaptic feedback. Electrical stimulation at 200 Hz applied to the lateral olfactory tract provides a substitute for the normal background activity emanating from the bulb and enables the generation of oscillatory responses once again. We conclude that a non-zero background level of activity is necessary and sufficient to sustain normal oscillatory responses and polysynaptic transmission through the entorhinal cortex.
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Potenciales de Acción/fisiología , Relojes Biológicos/fisiología , Corteza Entorrinal/fisiología , Red Nerviosa/fisiología , Vías Nerviosas/fisiología , Neuronas/fisiología , Bulbo Olfatorio/fisiología , Potenciales de Acción/efectos de los fármacos , Anestésicos/farmacología , Animales , Relojes Biológicos/efectos de los fármacos , Desnervación , Estimulación Eléctrica/métodos , Electrofisiología , Corteza Entorrinal/citología , Corteza Entorrinal/efectos de los fármacos , Potenciales Evocados/efectos de los fármacos , Potenciales Evocados/fisiología , Retroalimentación/efectos de los fármacos , Retroalimentación/fisiología , Femenino , Masculino , Microelectrodos/normas , Modelos Neurológicos , Red Nerviosa/citología , Red Nerviosa/efectos de los fármacos , Vías Nerviosas/citología , Vías Nerviosas/cirugía , Neuronas/efectos de los fármacos , Dinámicas no Lineales , Bulbo Olfatorio/citología , Bulbo Olfatorio/cirugía , Ratas , Ratas Sprague-Dawley , Olfato/efectos de los fármacos , Olfato/fisiología , Transmisión Sináptica/efectos de los fármacos , Transmisión Sináptica/fisiología , Vigilia/efectos de los fármacos , Vigilia/fisiologíaRESUMEN
Existing methods of complexity research are capable of describing certain specifics of bio systems over a given narrow range of parameters but often they cannot account for the initial emergence of complex biological systems, their evolution, state changes and sometimes-abrupt state transitions. Chaos tools have the potential of reaching to the essential driving mechanisms that organize matter into living substances. Our basic thesis is that while established chaos tools are useful in describing complexity in physical systems, they lack the power of grasping the essence of the complexity of life. This thesis illustrates sensory perception of vertebrates and the operation of the vertebrate brain. The study of complexity, at the level of biological systems, cannot be completed by the analytical tools, which have been developed for non-living systems. We propose a new approach to chaos research that has the potential of characterizing biological complexity. Our study is biologically motivated and solidly based in the biodynamics of higher brain function. Our biocomplexity model has the following features, (1) it is high-dimensional, but the dimensionality is not rigid, rather it changes dynamically; (2) it is not autonomous and continuously interacts and communicates with individual environments that are selected by the model from the infinitely complex world; (3) as a result, it is adaptive and modifies its internal organization in response to environmental factors by changing them to meet its own goals; (4) it is a distributed object that evolves both in space and time towards goals that is continually re-shaping in the light of cumulative experience stored in memory; (5) it is driven and stabilized by noise of internal origin through self-organizing dynamics. The resulting theory of stochastic dynamical systems is a mathematical field at the interface of dynamical system theory and stochastic differential equations. This paper outlines several possible avenues to analyze these systems. Of special interest are input-induced and noise-generated, or spontaneous state-transitions and related stability issues.
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Adaptación Fisiológica , Encéfalo/fisiología , Modelos Teóricos , Cadenas de Markov , Dinámicas no LinealesRESUMEN
Arrays of 64 electrodes (8 x 8, 7 x 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.
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Electroencefalografía , Neocórtex/fisiología , Tiempo de Reacción/fisiología , Procesamiento de Señales Asistido por Computador , Animales , Corteza Auditiva/fisiología , Electrodos Implantados , Femenino , Análisis de Fourier , Conejos , Corteza Somatosensorial/fisiología , Corteza Visual/fisiologíaRESUMEN
This study investigated the tonotopic organization of pure-tone-evoked middle latency auditory evoked potentials (MAEPs) recorded at the auditory cortical surface in unanesthetized gerbils. Multielectrode array recording and multiple linear regression analysis of the MAEP demonstrated different degrees of tonotopic organization of early and late MAEP components. The early MAEP components P1 and N1 showed focal topography and clear dependence in location and size of cortical area covered on pure-tone frequency. The later components P2 and N2 showed a widespread topography which was largely unaffected in location and size of cortical area covered by pure-tone frequency. These results allow delimitation of the neural generators of the early and late MAEP components in terms of the spectral properties of functionally defined neural populations.
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Corteza Auditiva/fisiología , Mapeo Encefálico , Espacio Epidural/fisiología , Potenciales Evocados Auditivos/fisiología , Percepción de la Altura Tonal/fisiología , Estimulación Acústica , Animales , Gerbillinae , Modelos Lineales , Masculino , Tiempo de Reacción/fisiología , Análisis de RegresiónRESUMEN
Spatial spectral analysis is essential for deriving spatial patterns from simultaneous recordings of electrocorticograms (ECoG), in order to determine the optimal interval between electrodes in arrays, and to design spatial filters, particularly for extraction of information about the dynamics of human gamma activity. ECoG were recorded from up to 64 electrodes 0.5 mm apart in a linear array 3.2 cm long, which was placed on the exposed superior temporal gyrus or motor cortex of volunteers undergoing diagnostic surgery. Visual displays of multiple traces revealed broad spectrum oscillations in episodic bursts having a common aperiodic wave form with recurring patterns of spatial amplitude modulation (AM patterns) on selected portions of the array. The one-dimensional spatial spectrum of the human ECoG was calculated at successive time samples and averaged over periods of up to 20 s. Log power decreased monotonically with increasing log spatial frequency in cycles/mm (c/mm) to the noise level approximately 2 log units below maximal power at minimal frequency (0.039+/-0.002 c/mm). The inflection point at 0.40+/-0.05 c/mm specified an optimal value for a low pass spatial filter to remove noise, and an optimal interelectrode spacing of 1.25 mm to avoid undersampling and aliasing. An 8 x 8 array with that spacing would be 10 x 10 mm.
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Encefalopatías/fisiopatología , Corteza Cerebral/fisiopatología , Adolescente , Adulto , Electrodos Implantados , Electroencefalografía , Femenino , Humanos , Procesamiento de Imagen Asistido por Computador , Masculino , Persona de Mediana EdadRESUMEN
Intelligent behavior is characterized by flexible and creative pursuit of endogenously defined goals. Intentionality is a key concept by which to link neuron and brain to goal-directed behavior through brain dynamics. An archetypal form of intentional behavior is an act of observation in space-time, by which information is sought for the guidance of future action to explore unpredictable and ever-changing environments. These acts are based in the brain dynamics that creates spatiotemporal patterns of neural activity, serving as images of goals, of command sequences by which to act to reach goals, and of expected changes in sensory input resulting from intended actions. Prediction of the sensory consequences of intended action and evaluation of performance is by reafference. An intentional act is completed upon modification of the system by itself through learning. These principles are well known among psychologists and philosophers. What is new is the development of nonlinear mesoscopic brain dynamics, by which the theory of chaos can be used to understand and simulate the constructions of meaningful patterns of neural activity that implement the process of observation. The design of neurobiological experiments, analysis of the resulting data, and synthesis of explanatory models require an understanding of the hierarchical nature of brain organization, here conceived as single neurons and neural networks at the microscopic level; clinically defined cortical and subcortical systems studied by brain imaging (for example, fMRI) at the macroscopic level, and self-organizing neural populations at an intermediate mesoscopic level, at which synaptic interactions create novel activity patterns through nonlinear state transitions. The constructive neurodynamics of sensory cortices, when they are engaged in pattern recognition, is revealed by learning-dependent spatial patterns of amplitude modulation and by newly discovered radially symmetric spatial gradients of the phase of aperiodic carrier waves in multichannel subdural EEG recordings.
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Conducta/fisiología , Encéfalo/fisiología , Neuronas/fisiología , Animales , Conducta Animal/fisiología , Electroencefalografía , Humanos , Modelos NeurológicosRESUMEN
The present study investigated the topography of epidurally recorded middle latency components P1 and N1 evoked by spectrally dynamic stimuli (linearly frequency-modulated (FM) tones) with respect to the tonotopic structure of the right primary auditory cortex, field AI. Whereas the gross topography corresponded to the spectral content of the FM tones, specific tonotopic offsets were found between the potential distributions evoked by FM tones of different modulation direction (i.e. 'rising' vs. 'falling'). Potentials evoked by rising FM tones were located at tonotopic positions corresponding to higher frequencies compared with potentials evoked by falling FM tones. Data indicated that the magnitude of these offsets can be attributed to the local tonotopic resolution in AI and are not dependent on the modulation rate.
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Corteza Auditiva/fisiología , Electroencefalografía , Potenciales Evocados Auditivos/fisiología , Neuronas/fisiología , Estimulación Acústica , Animales , Gerbillinae , Tiempo de ReacciónRESUMEN
New methods were devised to improve the discrimination of EEG spatial amplitude patterns recorded from arrays of 64 electrodes placed on visual, auditory or somatic cortex. The 64 traces shared a spatially coherent, aperiodic carrier wave with a spatial pattern of amplitude modulation (AM). Previous observations on AM patterns from rabbits trained to discriminate conditioned stimuli with reinforcement (CS+) and without (CS-) had revealed epochs between the CS and the CR in which AM patterns on CS+ trials could be distinguished from AM patterns on CS- trials. The AM patterns were expressed by points in 64-space that formed clusters. Levels of CS-/CS+ pattern separation were quantified by a pair-wise Euclidean distance method with cross-validation. The present study documents use of the technique for nonlinear mapping (NLM) to project the 64-dimensional structure onto a plane while preserving the relative distances between all points. The goodness of classification by the Euclidean distance measure was the same or improved after projection. Whereas the Euclidean distance measure only gave pair-wise classifications, the planar displays showed the patterns for multiple clusters simultaneously. These NLM-based methods revealed previously unrecognized structures within distributions of AM patterns in sensory cortices in the time period between the CS and CR.
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Mapeo Encefálico/métodos , Electroencefalografía/métodos , Animales , Corteza Auditiva/fisiología , Análisis por Conglomerados , Análisis Discriminante , Conejos , Corteza Somatosensorial/fisiología , Corteza Visual/fisiologíaRESUMEN
Field potentials were recorded simultaneously from the olfactory bulb (OB), prepyriform cortex (PPC), entorhinal cortex (EC), and dentate gyrus (DG) of rats trained to respond to appetitively reinforced odors. Preafferent anticipatory events in the beta band (12-35 Hz) suggest transmission from EC to OB before the odorant stimulus. Gamma band (35-120 Hz) power in olfactory regions is significantly reduced during stimulus presentation as compared with high values during preafferent expectation. High coherence of OB and PPC gamma activity during the preodorant control period is interrupted before the stimulus and is followed by increased gamma coherence among OB, EC, and DG. These results suggest that olfactory perceptual processing is bidirectional and covers a wide frequency range.
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Condicionamiento Operante/fisiología , Sistema Límbico/fisiología , Olfato/fisiología , Vías Aferentes/fisiología , Animales , Conducta Apetitiva/fisiología , Nivel de Alerta/fisiología , Sincronización Cortical , Señales (Psicología) , Giro Dentado/fisiología , Vías Eferentes/fisiología , Corteza Entorrinal/fisiología , Potenciales Evocados/fisiología , Masculino , Modelos Neurológicos , Odorantes , Vías Olfatorias/fisiología , Oscilometría , Ratas , Ratas Sprague-Dawley , Recompensa , Factores de TiempoRESUMEN
Scanning-laser ophthalmoscope (SLO) technology has provided, among other possibilities, the potential for three-dimensional (3-D) visualization of anatomy in the posterior pole of the eye. The use of indocyanine green (ICG) as an infrared fluorescent marker of vasculature in combination with aninfrared SLO (the Heidelberg Retina Angiograph) is presented. Presently, two main factors among others discussed impede the visualization of 3-D structures in observed SLO data. Random eye motion between optical sections and (to a lesser degree) motion between raster scan lines prevent assessment of spatial orientation and connectivity of vasculature. Second, smear along the optic axis owing to the optics prevents accurate determination of vessel or lesion size and shape, especially for features spanning several optical sections. A novel, to our knowledge, deconvolution algorithm is described that automatically corrects for the poor axial (optical-sectioning) resolution of the SLO and for patient random eye motion during target fixation. Encouraging preliminary results are presented showing the usefulness of applying blind deconvolution toward improving the 3-D clarity of SLO data. Although clinical and medical research applications are broad, the specific medical sample selected shows the potential of examining microvascular 3-D morphology for diagnosis and treatment of choroidal tumors.
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Brains are dynamic systems in which learning tends towards isolation by increasing specialization of cognitive skills. Induction of social skills for cooperative behavior requires "unlearning" in social contexts. A hypothesis is proposed by which oxytocin and related neuropeptides play a key role in meltdown of prior learning in preparation for new learning. This has implications for clinical management of disorders of the socialization processes in children.
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Encéfalo/fisiología , Neurotransmisores/fisiología , Conducta Social , Animales , Trastorno Autístico/fisiopatología , Trastorno Autístico/psicología , Niño , Cognición , Electroencefalografía , Procesos de Grupo , Humanos , Aprendizaje , Mamíferos , Modelos Neurológicos , Modelos Psicológicos , Neuropéptidos/fisiología , Oxitocina/fisiologíaRESUMEN
In this review I posit two levels of neural function. Microscopic activity is generated by neurons, to the extent that they act autonomously or in concert with networks of finite numbers of other neurons. Macroscopic activity is found in neuropil, where it depends on the sustained interaction of innumerable neurons. These levels coexist in cerebral cortex. Microscopic activity is manifested in the fraction of the variance of single neuron pulse trains (> 99.9%) that is both random and uncorrelated with pulse trains of other neurons in the neuropil. Macroscopic activity is revealed in the < 0.1% of the total variance of each neuron that is covariant with all other neurons in an area of neuropil comprising a population. It is best observed in dendritic potentials recorded as surface EEGs. The "spontaneous" background activity of neuropil at both levels arises from mutual excitation within a population of excitatory neurons. It is governed by a point attractor of the neuropil, which is actualized by the microscopic activity engendering the macroscopic state, and which acts as an order parameter to regulate the contributing neurons. The point attractor manifests a homogeneous field of white noise, into which sensory receptors send their microscopic stimuli. When neuropil comprises both excitatory and inhibitory neurons, the interactions at the macroscopic level lead to oscillations, manifesting a limit cycle attractor. When multiple areas of neuropil comprising a sensory system interact, then owing to their incommensurate characteristic frequencies and the long axonal delays between them, the system maintains a global chaotic attractor having multiple wings, one for each discriminable class of stimuli. Access to each wing is by stimulus-induced state transitions, leading to the construction of macroscopic chaotic patterns, that are carried to targets of cortical transmission by the microscopic noise. The chaotic modulation of the carrier noise is extracted by the targets through spatiotemporal integration, thereby retrieving the small covariance comprising the chaotic signal. Thus, controlled noise is the substrate for the meanings of stimuli that are expressed in chaotic patterns of sensory cortical activity.
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Corteza Cerebral/fisiología , Red Nerviosa/fisiología , Neuronas/fisiología , Dinámicas no Lineales , Animales , Artefactos , Corteza Cerebral/ultraestructura , Procesos EstocásticosRESUMEN
Olfactory bulb activity has been postulated to be chaotic, as measured in the EEG, and to be subject to an attractor with many "wings" enabling classification of different learned odor classes. Two parallel questions are thus addressed by the work presented here: (1) what is the evidence for attractors in the olfactory system, which can mediate learned odor classes? and (2) how does the olfactory system enter a specific attractor or attractor wing associated with the learned odor during the classification process? Both of these questions address the wider notion of endogenous activity preparing the system for an expected stimulus, which is at the basis of the reafference principle. By viewing the brain as a distributed complex dynamical system with global attractors, these questions can be answered together. Rats were implanted with bipolar macroelectrodes in the Olfactory Bulb (OB), Prepyriform Cortex (PPC), Entorhinal Cortex (EC), and Dentate Gyrus (DG), and then trained in an operant paradigm to press a bar for a reward in the presence of one odor and to receive no reward in the presence of another odor. Local Field Potentials (LFP) were recorded simultaneously from the structures during the operant task. We present evidence for three endogenous events: (1) preafference, which is manifested both by the EC entering an attractor and a mid-range signal (15-30 Hz) which appears to be passed from the EC to the OB just before the OB enters an attractor; (2) afference, where the OB enters an attractor during the odor recognition period of the experiment and the LFP recordings indicate that the OB drives the other structures in all frequency bands, especially the high gamma band (65-100 Hz) associated with the OB burst frequency; and (3) reafference or post-afference, which is accompanied by a lower frequency gamma band signal (40-60 Hz) originating in the PPC and passed to both the OB and the EC just before the onset of the motor response to the odor. We use a new method, NECTAR (Nonparametric Exact Contingency Table Association Routine), related to mutual information, to verify what is seen with coherence and phase estimates, the apparent driving of each structure at different times in the odor trials, and to display evidence for non-periodic attractors governing both individual physiological structures and the system of structures. This is the first evidence of an endogenous, limbic event associated with sensory perceptual tuning in a mammal. These results are also the first experimental confirmation that the attractors governing olfactory activity involve multiple sites in the olfactory/limbic system and implement the process of attention.
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Adaptación Fisiológica , Giro Dentado/fisiología , Corteza Entorrinal/fisiología , Odorantes , Vías Olfatorias/fisiología , Percepción/fisiología , Vías Aferentes/fisiología , Animales , Electroencefalografía , Potenciales Evocados/fisiología , Masculino , Probabilidad , Ratas , Ratas Sprague-DawleyRESUMEN
1. Spatial ensemble averages were computed for 64 traces of electroencephalograms (EEGs) simultaneously recorded from 8 x 8 arrays over the epidural surfaces of the prepyriform cortex (PPC) and visual, somatic, and auditory cortices. They revealed a common waveform across each array. Examination of the spatial amplitude modulation (AM) of the waveform revealed classifiable spatial pattern in short time segments. The AM patterns varied within trials after presentation of identical conditioned stimuli, and also between trials with differing stimuli. 2. PPC EEGs revealed strong correlates with the respiratory rhythm; neocortical EEGs did not. 3. Time ensemble averaging of the PPC EEG attenuated the oscillatory bursts, indicating that olfactory gamma oscillations (20-80 Hz) were not phase-locked to the times of stimulus delivery but instead to inhalations. Time ensemble averages of neocortical recordings across trials revealed average evoked potentials starting 30-50 ms after the arrival of the stimulus. 4. Average temporal fast Fourier transform (FFT) power spectral densities (PSDs) from pre- and poststimulus PPC EEG segments revealed a peak of gamma activity in olfactory bursts. 5. The logarithm of the average temporal FFT PSDs from pre- and poststimulus neocortical EEG segments, when plotted against log frequency, revealed 1/f-type spectra in both pre- and poststimulus segments for negative/aversive conditioned stimuli (CS-) and positive/rewarding conditioned stimuli (CS+). The alpha'- and beta'-coefficients from the regression of Eq. 2 onto the average PSDs were significantly different between pre- and poststimulus segments, owing to the evoked potentials, but not between CS- and CS+ stimulus segments. 6. Spatiotemporal patterns were invariant over all frequency bins in the 1/f domain (20-100 Hz). Spatiotemporal patterns in the 2- to 20-Hz domain progressively differed from the invariant patterns with decreasing frequency. 7. In the spatial frequency domain, the logarithm of the average spatial FFT power spectra from pre- and poststimulus neocortical EEG segments, when plotted against the log spatial frequency, fell monotonically from the maximum at the lowest spatial frequency, downwardly curving to a linear 1/f spectral domain. This curve in the 1/f spectral domain extended from 0.133 to 0.880 cycles/mm in the PPC and from 0.095 to 0.624 cycles/mm in the neocortices. 8. Methods of FFT and principal component analysis (PCA) EEG decomposition were used to extract the broad-spectrum waveform common to all 64 EEGs from an array. AM patterns for the FFT and PCA components were derived by regression. They were shown by cross-correlation to yield spatial patterns that were equivalent to each other and to AM patterns from calculation of the 64 root-mean-square amplitudes of the segments. 9. Each spatial AM pattern was expressed by a 1 x 64 column vector and a point in 64-space. Similar patterns formed clusters, and dissimilar patterns gave multiple clusters. A statistical test was devised to evaluate dissimilarity by a Euclidean distance metric in 64-space. 10. Significant spatial pattern classification of CS- versus CS+ trials (below the 1% confidence limit for 20 of each) was found in discrete temporal segments of poststimulus data after digital temporal and spatial filter optimization. 11. Varying the analysis window duration from 10 to 500 ms yielded a window length of 120 ms as optimal for pattern classification. A 120-ms window was subsequently stepped across each record in overlapping intervals of 20 ms. Windows in which episodic, significant CS+/CS- differences occurred lasted 50-200 ms and were separated by 100-200 ms in the poststimulus period. 12. Neocortical spatial patterns changed under reinforcement contingency reversal, showing a lack of invariance in respect to stimuli and a dependence on context and learning, as previously found for the olfactory bulb and PPC.