Michael I. G. Simpson

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Modulation perception has typically been characterized by measuring detection thresholds for sinusoidally amplitude-modulated (SAM) signals. This study uses multicomponent modulations. "Second-order" temporal modulation transfer functions (TMTFs) measure detection thresholds for a sinusoidal modulation of the modulation waveform of a SAM signal [Lorenzi et(More)
We have examined whether the widely used herbicide, paraquat (1,1'-dimethyl-4,4'dipyridylium) may accumulate in rat brain following multiple oral dosing (5 mg paraquat ion/kg/day) for 14 days and whether this dosing regime may produce signs of neurotoxicity. This dosing regime may determine whether low dose exposure to mammals may be neurotoxic. Using(More)
Experiments were performed to determine the extent of paraquat entry into the brain of neonatal and elderly rats, as compared with adult rats, which may be dependent on the efficacy of the blood-brain barrier. A single, median lethal dose (20 mg/kg s.c.) of paraquat containing [14C]paraquat was administered to neonatal (10 day old), adult (3 month old) and(More)
Pollen of eight species of Cryptantha was studied using scanning electron microscopy. In addition, transmission electron microscopy was used in Cryptantha intermedia to elucidate the ultrastructural basis for their heterocolpate pollen, in which three " true " colporate apertures alternate with three " pseudoapertures. " Both apertures and pseudoapertures(More)
  • Annette Lewis Winner, Michael G Simpson, Resumen Pentagramma, Windham Yaskievych, E Wollenweber, Subsp Rebmanii Winner +1 other
  • 2008
Pentagramma triangularis (Kaulfuss) Yatskievych, Windham, & E. Wollenweber subsp. rebmanii Winner and M. G. Simpson subsp. nov. is a new subspecies endemic to south-central to southeast San Diego County, California, USA, and inland, northwestern Baja California, Mexico. It is uncommon on seasonally moist, granitic-derived or gabbro-clay substrates,(More)
This paper introduces a lead field formulation for use in beamformer analysis of MEG data. This 'dual source beamformer' is a technique to image two temporally correlated sources using beamformer methodology. We show that while the standard, single source beamformer suppresses the reconstructed power of two spatially separate but temporally correlated(More)
BACKGROUND Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a familial heart muscle disease characterized by structural, electrical, and pathological abnormalities of the right ventricle (RV). Several disease loci have been identified. Mutations in desmoplakin have recently been isolated in both autosomal-dominant and autosomal-recessive forms of(More)
This study used magnetoencephalography (MEG) to examine the dynamic patterns of neural activity underlying the auditory steady-state response. We examined the continuous time-series of responses to a 32-Hz amplitude modulation. Fluctuations in the amplitude of the evoked response were found to be mediated by non-linear interactions with oscillatory(More)
In this study we investigate whether stimulus variability affects the auditory steady-state response (ASSR). We present cosinusoidal AM pulses as stimuli where we are able to manipulate waveform shape independently of the fixed repetition rate of 4 Hz. We either present sounds in which the waveform shape, the pulse-width, is fixed throughout the(More)
—Cryptantha (Boraginaceae) is a group of approximately 200 annual and perennial species, representing two-thirds of the diversity within subtribe Cryptanthinae. The genus exhibits an amphitropic distribution, occurring in temperate and desert regions of western North and South America. Fifty samples of 45 species of Cryptantha s. l., exemplars of the(More)