ABSTRACT
OBJECTIVES: Fractal geometry is a tool used to characterize irregularly shaped and complex figures. It can be used not only to generate biological structures (e.g., the human renal artery tree), but also to derive parameters such as the fractal dimension in order to quantify the shapes of structures. As such, it allows user-independent evaluation and does not rely on the experience level of the examiner. METHODS: We applied a box-counting algorithm to determine the fractal dimension of atypical nuclei in dysplastic cervical epithelium. An automatic algorithm was used to determine the fractal dimension of nuclei in order to prevent errors from manual segmentation. Four groups of patients (CIN 1-3 and control) with 10 subjects each were examined. In total, the fractal dimensions of 1200 nuclei were calculated. RESULTS: We found that the fractal dimensions of the nuclei increased as the degree of dysplasia increased. There were significant differences between control and atypical nuclei found by an analysis of variance. Atypical nuclei associated with CIN 1, CIN 2, and CIN 3 also differed significantly among these groups. CONCLUSION: We conclude that the fractal dimension is a valuable tool for detecting irregularities in atypical nuclei of the cervix uteri and thus allows objective nuclear grading.
Subject(s)
Cell Nucleus/pathology , Fractals , Uterine Cervical Dysplasia/pathology , Female , HumansABSTRACT
The use of a stochastic resonance model contributes crucially to our comprehension of the intensity resolution characteristics of the mammalian cochlea. In guinea pigs, as demonstrated by different statistical methods, the temporal distribution of the interspike intervals of the spontaneous activity reflects an intrinsic cochlear white noise process, demanded as basic requirement for manifest stochastic resonance phenomena. Brownian motion of cochlear fluids is discussed as the underlying white noise motor. Following our model, the amount of white noise, adjusted at the level of the stereocilia of the inner hair cells, determines the threshold, dynamic range and intensity discrimination limen of an individual afferent neuron of the mammalian cochlea.
Subject(s)
Cochlea/physiology , Signal Transduction/physiology , Animals , Cochlea/innervation , Fractals , Guinea Pigs , Hair Cells, Auditory, Inner/physiology , Neurons, Afferent/physiology , Signal Processing, Computer-Assisted , Stochastic ProcessesABSTRACT
In the mammalian primary cochlear afferents, fractals in the postsynaptic bursting behaviour triggered by a constant perisynaptic release of glutamatergic transmitter agonists have been demonstrated. In order to test the validity of fractally coded auditory signal transmission in man, frequency, intensity and temporal resolution tests were performed in cochlear implanted patients. All patients clearly recognized the fractally coded signals transmitted to the cochlear implants. These first results demonstrate evidence for fractally coded auditory signal transmission in man.
Subject(s)
Auditory Perception , Cochlear Implants , Adult , Aged , Deafness/rehabilitation , Electric Stimulation , Humans , Middle AgedABSTRACT
In guinea pigs, the constant iontophoretic release of transmitter agonists in the synaptic cleft of inner hair cells (IHC) triggers chemically an irregular and bursting mode of spiking discharge, subsynaptically recorded in the afferent dendrites. The tendency to form spike clusters appears to be independent of the quality and quantity of the used test substances, the excitatory amino acids N-methyl-D-aspartate (NMDA) and alpha-amino-3-hydroxy-5-methyl-4- isoxazole-propionic acid (AMPA). The recorded spike trains show a remarkable stability of the calculated individual box-counting dimension characterizing the bursting behaviour as a fractal random point process. The fractal kinetics seems to reflect molecular instabilities of cochlear afferent glutamate receptors, determining the mode of the signal transmission in the auditory periphery.
Subject(s)
Auditory Pathways/anatomy & histology , Fractals , Receptors, Glutamate/physiology , Signal Transduction/physiology , Synaptic Membranes/physiology , Action Potentials/physiology , Afferent Pathways/anatomy & histology , Animals , Female , Guinea Pigs , Iontophoresis , Male , MicrochemistryABSTRACT
As an average of minimal 3 to maximal 30 single auditory-nerve fibers converge in the auditory pathway, the fractal geometry of their signals is transformed to a different fractal geometry such that small variations of the primary discharge patterns correspond to large variations of the combined signal. The addition of white noise does not affect the fractal signal structure. The quality of the transsynaptic information transfer depends on the relation between the number of the convergent spike trains and the individual fractal geometries of the convergent spike trains.
