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These experiments try to exhibit the interactions of the electrical activity of the microenvironment of a neuronal population spatially distant from the microenvironment of a different neuronal population. These experiments involve 18 cats with chronic electrodes surgically implanted into cerebral cortex, septal nuclei and amygdala. The Fast Fourier Transform (FFT) algorithm is done to process frequency domain data. In order to compare the phase relations between two channels, x(t) and y(T), use is often made of the coherence function. Computing partial coherence implies first eliminating from each two signals, that part which can be considered as being determined by, or predictable, on the basis of a third signal. It is assumed that there are three stochastic signals Y1, Y2, Y3. These variables can be considered as spectral components for a particular frequency. We assume that the correlations can be interpreted as square root of the coherence. For simplicity we use, in the partial correlations analyses. more...

These studies use 24 cats under non-anesthetic states. Electrodes are implanted, under appropriate anesthetic and stereotoxic procedures in non-auditory neocortical areas, nucleus accumbens, and certain nuclei of the amygdala complex. Auditory stimulation was done using the free field method with periodic tones at 2.0 KHz to 3.0 KHz at 80db. The auditory stimulation and recording was performed with hard wire and telemetry methods. The analog data is collected on FM tape and processed with minicomputer. Digital filtering, cross, coherence, phase, spectral and cycle time analyses are used on the analog data. In these studies, we have looked at the electroencephalogram (EEG) and the auditory evoked potentials (AEP) of cortical and subcortical regions using frequency and time domain methods. The analyses of the interaction of spatially distributed neuronal networks during EEG and AEP activity may give insights to topographical relations in the brain. more...

There is evidence that certain brain rhythms may signal the occurrence of different brain states. Support for this hypothesis may be provided by evidence that processing of information is changed during different brain states. The prestimulus period proceeding the auditory evoked potential (AEP) is converted to a power spectral estimate. These power spectra are used to sort for the AEP when certain power values for the (36-42Hz) and the (11-16Hz) are reached in the prestimulus period of the sensory motor cortex, nucleus accumbers and amygdala. Attempts are made to measure the performance of the 40Hz and SMR estimators. These studies are made in the cerebral cortical and subcortical regions in cats. In these studies D and L isomers of amphetamine are used to induce a chemical brain state changes. The AEP are selected in the amphetamine altered states based on the prestimulus auto spectra. more...

These studies concern the EEG rhythms of the sensory motor cortex in cats. The cat generates a 12H to 16Hz rhythm related to the MU (Rolandic) rhythm in man. The behavioral state required to generate the rhythm in man and the cat requires complete immobility and alertness. The MU rhythm in man centers around 9Hz and in the cat at 12Hz to 16Hz. This rhythm is used in the biofeedback training for the treatment of intractable seizures in man. It has also been used (12 Hz to 16 Hz) experimentally in animals. It is necessary to enhance the MU rhythm and simultaneously depress the seizure activity. Our interest has been to detect and enhance the SMR rhythm (12 H to 16 Hz) in the cat. We found that when it is enhanced it also enhances the amplitude of auditory evoked potentials in other brain regions. more...