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Understanding sensory-motor integration ORGANIZATION OF SENSORY SYSTEMS: General perspectives • • • • • Sensori-motor integration External senses Localize/Detect and monitor change Less sensitive to unchanging stimuli Tuned…sense modes Organization of sensory systems • Sense organs • Receptors-specificity and transduction – Receptive fields- and limitations • coding- labeled lines vs pattern coding • Adaptation and suppression • • • • Neural relays and recoding Intra-modality sensory Convergence Cortical representation/ perception Sensory subsystems The Visual System Tracing the ccts of vision Organization of sensory systems • Sense organs • Receptors-specificity and transduction – Receptive fields- and limitations • Adaptation and suppression • coding- labeled lines vs pattern coding • • • • Neural relays and recoding Intra-modality sensory Convergence Cortical representation/ perception Sensory subsystems The organ of vision The eye is like an SLR camera Like a camera • Lens-focus • Iris-light control (aperture) • Photoreceptors- transduction of light info (Light sensitive film) The lens-a small point of interest Like a camera-lens is curved • Upside-down and inverted Like a camera- Control of eye movement also critical Eye movement- 3 major types of movement that can affect vision Pursuit/tracking Saccades vergence Organization of sensory systems • Sense organs • Receptors-specificity and transduction – Receptive fields- and limitations – Adaptation and suppression – coding- labeled lines vs pattern coding • • • • Intra-modality sensory Convergence Neural relays and recoding Cortical representation/ perception Sensory subsystems Sensitivity and Limitations of the visual system: visible light spectrum Organization of sensory systems • Sense organs • Receptors-specificity and transduction – Receptive fields and limitations – Adaptation and suppression – coding- labeled lines vs pattern coding • • • • Intra-modality sensory Convergence Neural relays and recoding Sensory subsystems Cortical representation/ perception The Iris • Controls light exposure Organization of sensory systems • Sense organs • Receptors-specificity and transduction – Receptive fields- and limitations – Adaptation and suppression – coding- labeled lines vs pattern coding • • • • Intra-modality sensory Convergence Neural relays and recoding Sensory subsystems Cortical representation/ perception The retina-photoreceptive tissue Visual field and retino-topic organization More on the retina Photoreceptors Rods and Cones Receptive fields and Coding RODS- dark/low illumination sensitive to movement peripheral vision CONES- High illumination sensitive to color foveal vision ROD CONE DISTRIBUTION FOVEA FOVEA and optic disc/blind spot Foveal acuity Retinal circuitry NOTE: • Light passes through ganglion cell layer, and bipolar cell layer before striking photoreceptors ( light transparent). • Activation of photoreceptor activats cct in reverse direction. What accounts for Foveal acuity Accounting for Foveal Accuity 1. Cone properties 2. Circuitry Color Coding in cones The Trichromatic Theory of color Receptive fields of Ganglion cells Set up for sensory evoked recording Sensory convergence Retinal photoreceptors corresponding to Ganglion cell receptive fields Purpose of ganglion cell receptive fields? Lateral inhibition? Lateral inhibition Overlapping receptive fields contribute to lateral inhibition The center of one field may be the surround of another Retina ganglion cell axons coalesce …and leave eye chamber to form the optic nerve From retina to cortex Decussation at optic chiasm Decussation-crossing over ..how does this work? Partial decussation at optic chiasm Decussation-crossing over Not as simple as left and right eye Decussation of visual field info Temporal retina Nasal Retina -Nasal Retinal Fibers Cross -Temporal fibers do not Retinotopic-Cortical representation -Left and right visual field info -upside down -Foveal dominance Cortical Organization- LGN input at layer 4 Vertical processing Set up for sensory evoked recording Remember sensory convergence Receptive fields of neurons in the PVC-orientation specificity Orientation specificity Orientation modules:Sensoryevoked recording studies Modules- orientation specific columns plus PVC “blobs” Diagnosing/predicting visual deficits What happens if the entire PVC is damaged? Blind sight/ Superior Colliculi • http://video.google.com/videosearch?hl=e n&rls=GGIC,GGIC:200701,GGIC:en&ei=KD1bSsuNMJKKMec7EI&resnum=0&q=blindsight&um=1&ie= UTF-8&sa=N&tab=wv# • Other visual subsystems -SCN -Pineal gland Suprchiasmatic NucleusCircadian Rhythms Pineal Gland-”the third eye” and Infradian rhythms Secretor cells of the pineal gland Produce melatonin OK… so what happens next? VENTRAL STREAM • Object Recognition – Visual agnosias – Prosopagnosia – Anosagnosia – http://video.google.com/videosearch?q=ramachandran+synesthe sia&www_google_domain=www.google.com&hl=en&emb=0&aq =4&oq=ramachandran#q=ramachandran+imposter&hl=en&emb =0 prosopagnosia • Dorsal Sream• WHERE/ CONTEXT/SPACE – Balints – Movement agnosia – Visual Sensory neglect Balint’s syndrome and Simultagnosia • Balint's syndrome is a neuropsychological disorder that results from damage to both parietal lobes 77. Clinically, it includes three main symptoms: simultanagnosia (the inability to see more than one object at a time); optic ataxia (the fixation of gaze with severe problems in voluntarily moving fixation); and optic apraxia (the inability to reach towards the correct location of perceived objects)78 • Spatial-visual agnosia Visual hemilateral neglect Putting the Visual World into perspective: The DLPFC Synesthesia and the DLPFC? • http://science.discovery.com/videos/whensenses-collide-origins.html • Synesthesia • Check it out Dawgs! Sensori-Motor Integration