Abstract Details

Simultaneous detection of multiple EEG chirps by phase steps.

This author’s 1976 PhD Thesis(1) developed a method of EEG chirp analysis that could now be of practical use with faster computers. Fast Fourier Transforms, frequency shifted, with pre-whitening and phase-step prediction were used to simultaneously detect multiple overlapping occipital chirps,, starting at +–90 degrees at 0Hz (P or N) and around +-400Hz.sec (up and down_chirps). An Mwave was an up chirp turning over at some frequency (Mheight) to become a down _chirp of the same phase at 0Hz. Alternating P and N chirps , approximately 50ms apart from each other, were found at P4_O2. To some extent they could be differentiated by adding or subtracting a DC term. (2) A similar result was found, at lower frequencies, for the canine gastro-oesophageal sphincter. Subsequently, averaged random photic flash evoked potentials, with eyes closed, produced three classes of initial Ndown and Pup chirps, starting at the same frequency, and differentiated by the number of cycles the Ndown chirp took to reach 0Hz (3). Analogue pre-emphasis, with eyes open, and a flash at 40cm, partially occluded by a 1cm square chess board pattern, produced an initial three successive down-chirps, separated by 50ms, being N,P and N respectively (4). A somatosensory AEP showed a Ndown-chirp at -800Hz.sec. Some upchirps and ‘noise’ were removed by deleting components below an arbitrary amplitude. Concepts of cyclic detection and generation of down and up chirps via matched delays ( as memory, or layers of memory) into the equivalent of AND and OR gates, and hypothetical relationships to both content-addressable and refreshable memory, similar to DRAM, have problems but might be of some theoretical value. Various other EEG chirp detecting procedures have been developed elsewhere since approximately 2000.

TitleForenamesSurnameInstitutionLead AuthorPresenter
DrDouglas EMaynardRetired. Formerly EEG Dept, The Royal London Hospital
Reference
A Computer Analysis Of The Human Electroencephalogram. D E Maynard, 1976, https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.465350
Analysis of EEG in terms of overlapping pulse sequences D E Maynard Electroencephalography and Clinical Neurophysiology.1977, 43(4):479
Chirp Analysis of Averaged Evoked Responses To Photic Stimuli. D E Maynard, Electroenceph.clin.Neurophysiol, 1981, 52 (1), P25-P26
Extraction of Chirps From EEG Waveforms. D E Maynard, Electroenceph.clin.Neurophysiol, 1985.61:68P