Auditory cortical plasticity under operation: reorganization of auditory cortex induced by electric cochlear stimulation reveals adaptation to altered sensory input statistics
ABSTRACT We introduce a framework based on plastic-adaptational processes for an interpretation of electrical cochlear implant (CI) stimulation. Cochlear prostheses are used to restore sound perception in adults and children with profound deafness. After providing a review of cortical plasticity, we summarize our findings using optical imaging of intrinsic signals to map cat auditory cortex (AI) activated by CI stimulation. In adult AI of neonatally deafened animals, the acoustic deprivation caused a severe distortion of cochleotopic maps. A three-month period of CI-stimulation using the continuous interleaved sampling strategy did not re-install the status typically found in normal adults, but resulted in the emergence of a new topographical organization characterized by large, joint representations of all stimulated electrode sites. We suggest that the effectiveness of CI-stimulation relies primarily on a re-learning of input pattern arising from “artificial” sensory inputs via electrical stimulation, thereby supporting the importance of learning and training for the interpretation and understanding of the effects of CI stimulation. We suggest that the ability for gaining/re-gaining speech understanding mediated by CI-stimulation is accomplished by new strategies of cortical processing due to enhanced cooperativity among large populations of neurons that serve higher processing stages to interpret new patterns arriving from the periphery. These strategies are thought to emerge from adaptational capacities in response to the constraints imposed by the properties of the new input statistics that in turn result from the stimulation strategy employed.
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ABSTRACT: 1. BACKGROUND In the early nineteenth century, Franz Gall, a German- born physician and neuroanatomist who studied and worked in Vienna, proposed that specific functions or behaviors are controlled by particular regions of the cerebral cortex. Although Gall extended this proposition to develop the (incorrect) doctrine of phrenology, it was the first account of localization of function in the cerebral cortex. Forty years later Gall's ideas were extended by Paul Pierre Broca, who in 1861 published an account of a patient who could understand language but could not speak. Postmortem examination of the patient's brain showed a lesion in the posterior area of the frontal lobes, an area that has become known as Broca's area. This intriguing finding led to the search for more functionally distinct regions of the cerebral cortex and, in 1870, Fritsch and Hitzig reported that electrically stimulating the pre- central gyrus in the dog resulted in movements of the contralateral limb. Fritsch and Hitzig had found what is now known as the primary motor cortex. Investigation of localized functional regions of the cerebral cortex in- creased at a rapid pace and by the mid-twentieth century it was well established that the cerebral cortex could be divided into discrete regions on the basis of cytoarchitec- tonics (type, density, and layering of cells) and physiolo- gical function. Localization of function in the cerebral cortex is perhaps best demonstrated in the mammalian visual cortex, where in the primate and presumably the human, more than 30 distinct cortical regions associated with the analysis of visual information exist. The localization of function in the cerebral cortex has traditionally relied on techniques such as lesion studies, neuroanatomical tract tracing and single-cell electrophy-Wiley Encyclopedia of Biomedical Engineering, 04/2006; , ISBN: 9780471740360
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ABSTRACT: An important article, entitled “Single units and sensation: a neuron doctrine for perceptual psychology” proposed that “active high-level neurons directly and simply cause the elements of our perception” (Barlow 1972). This work articulated the conceptual framework at that time and had a great impact on research of sensory information processing. In the 1950s, single neuron recordings, the monitoring of extracellular potential changes, had become routine in the laboratory, boosting the conceptual framework of single cell analysis.
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ABSTRACT: A Division III examination in the School of Cognitive Science, Hampshire College, May 2006. Chairperson, Neil Stillings. Includes bibliographical references.