Chapter 10 Visual Perception Visual Pathways Parvocellular system Magnocellular system M ganglion cells projects to dorsal stream where system that travels to posterior parietal lobe from areas V1 V2 V5 Brightness contrast orientation movement depth and location of objects Both systems then travel to the prefrontal cortex planning Disorders of Visual Perception Object agnosia impairment in ability to recognize objects by sight Prosopagnosia inability to recognize familiar faces Due to inferior temporal lobe damage fusiform face area specialized for face recognition Color agnosia impairment in color perception due to brain damage V1 is for wavelength discrimination V4 is for more complex color perception color constancy color of an object stays the same despite changing light such as a chair which stays red no matter the time of day Movement agnosia inability to perceive movement damage to area V5 medial temporal gyrus Neglect ignores visual touch auditory stimulation on opposite side of damages posterior parietal lobe mostly on right hemisphere Still have the systems to process the stimulation but they seem unable to direct attention to the stimulus Chapter 11 Body Senses and Movement Proprioception skin senses and the Vestibular Sense Proprioception sense of the position and movement of our limbs and body Involves sensors for tension in muscles and angles of limbs at joints Helps maintain posture move limbs and reach grasp objects Doesn t require attentional resources after they ve been established learned in early childhood Skin Senses Touch warmth cold and pain Two major types of receptor Free nerve endings sense of warmth cold pain dendrites of sensory neurons that have been specialized to act as receptors Relatively close to the surface Different protein channels for specific sensations 2 receptors for warmth 1 for cold 2 receptors for painful heat burning Vestibular Sense Encapsulated receptors complex structures enclosed in membrane sense of touch Merkel s discs and Meissner s corpuscle Located in superficial layers of skin Detect texture and fine detail of objects Respond also to movement ex move hand around on surface of object Ruffini ending and Pacinian corpuscle Located in deeper layers of skin Detect stretching of skin perception of shape of grasped objects Receptors send information to the post central gyrus primary somatosensory cortex found in parietal lobe Dermatome a segment of the body served by a specific nerve cranial or spinal Maintains balance and provides info on head position and movement Semicircular canals of inner ear responsive to rotational movement found on top of the cochlea 3 semicircular tubes of bone that are 90 degrees to each other oriented to almost represent the 3 major dimensions in space x y z Filled with endolymph fluid inside Toward the base there is an enlargement called the ampulla which contains a gelatin structure with nerve fibers coming out of it where receptors are located Cupula hair cells axons of ampullary nerve Hair cells activated by bending Utricle more horizontal and saccule more verticle monitor head position in relation to gravity Hair cells embedded into otolithic membrane gelatinous which have otoliths made of calcium carbonate which will tend to bend stretch gelatinous substance which will in turn activate the hair cells and send signal Simply put When head is tilted or moved the gelatinous mass with otoliths shifts bending cilia of the receptors depolarization repolarization Respond also to acceleration Utricle horizontal acceleration Saccule vertical acceleration
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