Sensory Systems Vision, Audition, Somatosensation, Gustation, & Olfaction Sarah L. Chollar University of California, Riverside sarah.chollar@gmail.com
Sensory Systems How the brain allows us to see, hear, feel, taste and smell the world around us. Why study sensory systems? Increases understanding of basic neural processes and promotes growth of the field Clinical benefit: treatment for disorders Cochlear Implants LASIK Refractive Eye Surgery
Systems Level Analysis The study of sensory systems focuses on a systems level of analysis. Levels of Analysis in Neuroscience Behavioral Systems Cellular Molecular Genetic Levels of Analysis Behavior Behavioral Systems Systems Interregional Circuits Local (Regional) Circuits Neurons Cellular Dendritic Trees Synaptic Microcircuits Synapses Molecular Molecules and Ions Genetic Genes
Sensory Systems Themes Organization Topographic Maps Layers and Columns Pathways and Circuits Specialized Sensory Receptors Processing Signal Transduction Coding of Sensory Information Serial and Parallel Processing http://www.colorado.edu/intphys/class/iphy3430-200/image/10-4.jpg
Overview Visual System Auditory System Somatosensory System Gustatory System Olfactory System Sensory System Discussion
Visual System Anatomy of the Visual System Organization of the Retina Photoreceptors and Signal Transduction Receptive Fields and Lateral Inhibition Visual Processing Pathways Cortical Organization Visual Deficits and Disorders The Binding Problem
1. Eye 2. Optic Nerve 3. Optic Chiasm 4. Optic Tract Visual System Anatomy Serial processing from eye to visual cortex- processing in sequence (1,2,3) 5. Lateral Geniculate Nucleus (LGN) of the Thalamus 6. Optic Radiation 7. Primary Visual Cortex (V1) http://www.nmr.mgh.harvard.edu/~rhoge/hst583/doc/visualcortex.jpg
Anatomy of the Eye
The Organization of the Retina Cell Types Photoreceptors Bipolar Cells Ganglion Cells Horizontal Cells Amacrine Cells Optic Nerve There are no photoreceptors here axons of ganglion cells form optic nerve and leave the eye Kalat, Biological Psychology 9 th Edition (2007)
Information Flow in the Retina 1. Photoreceptors 1. Rods/Cones 2. Bipolar Cells 1. Horizontal Cells 2. Amacrine Cells 3. Ganglion Cells Kalat, Biological Psychology 9 th Edition (2007)
Photoreceptors: Rods and Cones
Signal Transduction in Rods
Electromagnetic Spectrum Visible spectrum is a small part of the entire electromagnetic spectrum. Measured in nanometers How big is a nanometer?» Very small! Kalat, Biological Psychology 9 th Edition (2007)
Scale In Biological Systems A meter is divided into 1000 millimeters A millimeter is divided into 1000 micrometers A micrometer is divided into 1000 nanometers Microbiology coloring book
Trichromatic Theory Three types of cones Respond to different wavelengths (colors) Short Wavelength (S-W) Medium Wavelength (M-W) Long Wavelength (L-W) Significant overlap of M and L-W cones Kalat, Biological Psychology 9 th Edition (2007)
Trichromatic and Opponent Process
Color Vision Blue light stimulates S-W cone Excites bipolar cell and horizontal cell Excitation dominates over inhibition Bipolar sends blue signal to ganglion cell Green or red light excites horizontal cell and inhibits bipolar cell Yellow excites both L and M-W cones which excite the horizontal cell and produce strong inhibition of bipolar cell Kalat, Biological Psychology 9 th Edition (2007)
Photoreceptors: Rods vs Cones
Visual Acuity: Cones vs Rods One-to-one connectivity of cones increases visual acuity and fine discrimination High convergence of rods onto ganglion cells increases sensitivity to low light, but decreases acuity
Receptive Fields Receptive field a region of the retina that, when stimulated, causes a change in activity of the cell.
Center Surround Receptive Fields Level of the ganglion cells On Center Off center
Receptive Fields: Convergence from LGN to V1 Receptive fields become more complex as you ascend through the visual system through the convergence of inputs from lower levels. Center surround of ganglion cells converge in LGN Receptive fields of LGN cells converge on simple cells in V1
Cortical Receptive Fields: Simple and Complex Cells
A Hypercolumn
Visual Field Deficits Left visual field processed in right hemisphere Right visual field processed in left hemisphere
Visual Processing Pathways Once information reaches the visual cortex, processing of visual information takes place in several places and can occur at the same time We refer to this type of processing as parallel processing Processing in different areas happens at the same time Increases computational performance
Higher Processing of Visual Information Movement Magnocellular Integration of vision and movement Color Parvocellular/magnocellular Color and brightness Shape Parvocellular Complex shape analysis Kalat, Biological Psychology 9 th Edition (2007)
Auditory System Auditory and Vestibular System Anatomy Sound Perception Auditory Pathways Tonotopic Map of Auditory Cortex Sound Localization
Auditory System Anatomy Outer Ear Pinna Auditory Canal Middle Ear Tympanic Membrane Incus, Mallus, Stapes Oval/Round Window Inner Ear Cochlea Vestibular System Eustachian Tube Auditory Nerve
Kalat, Biological Psychology 9 th Edition (2007)
Sound Perception Kalat, Biological Psychology 9 th Edition (2007)
Auditory Processing Serial processing in the auditory system 1. Cochlea 2. Cochlear Nucleus 3. Superior Olive 4. Inferior Colliculus 5. Medial Geniculate Nucleus (MGN) Thalamus 6. Auditory Cortex (A1) Kalat, Biological Psychology 9 th Edition (2007)
Auditory Cortex: Tonotopic Organization Map of A1 is organized by frequency low on one end and high on the other This corresponds to locations on the basilar membrane of the cochlea Cells respond to a preferred tone (note), but respond better to complex sounds Kalat, Biological Psychology 9 th Edition (2007)
Sound Localization Several cues are used to determine the location of a sound Time of arrival Phase difference Loudness Time of arrival of a sound is delayed between left ear and right ear Kalat, Biological Psychology 9 th Edition (2007)
Sound Localization: Phase Phase works best as a sound localization cue for low frequency The difference in the phase of the waveform between one ear and the other Kalat, Biological Psychology 9 th Edition (2007)