Lectures3+4-Chapter_2-BiologicalFoundations

Another sense that of balance mediated by the

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Unformatted text preview: er sense, that of balance mediated by the vestibular system, is not part of the curriculum for this course. Aquatic animals (fish and amphibians) have, in addition to all of these other senses, an electric sense (mediated by specialized electroreceptors in the sensory periphery). Perceptions we experience from each sensory modality are a joint product of the sensory stimulation patterns we receive in our brains, together with ongoing brain activity that is independent of stimulation. 28 From the “Law of Specific Nerve Energies” to Networks The idea that sensory signals from each modality are transmitted by a specific set of nerve fibres that communicate directly with specific brain areas was first enunciated in 1826 by Johannes Müller. burda kaldin burdan devam et!! While this has turned out to be true, it has more recently been discovered that there is a good deal of “sharing” of information between sensory modalities – that is, nerve cells in brain areas that were initially thought of as primarily “visual”, “auditory” or “somatosensory” because of the massive sources of sensory input they receive, also Johannes Müller (1801-1858) respond to changes in stimulation from other sensory modalities (visual or somatosensory neurons changing their firing patterns in response to sound changes, for example). Nervous System: Multiple pathways, parallelism, and hierarchies Multiple pathways transmit signals from sensory organs to brain and within brain. Multiple pathways within a given sensory system are arranged in parallel: Can function independently at lower levels; are integrated at higher levels. Hierarchical organization: Lowest level = receptors and associated fibres Relay structures in brainstem, midbrain and thalamus send information on to higher cortical levels. 29 What Happens If We Reroute Nerve Fibres Carrying Sensory Signals To Another Part of the Brain? 30 2 From: von Melchner, L, Pallas, SL, Sur, M (2000) Visual behaviour mediated by retinal projections directed to t...
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