Vision and Audition - Human Neuropsychology PDF

Quiz! You accidentally touch a hot pot on the stove and reflexively withdraw your hand. Which of the following statements about the reflex arc is NOT true? a) Action potentials are generated in the afferent pathway when a painful stimulus activates pain receptors, which then propagates the impul...

Quiz! You accidentally touch a hot pot on the stove and reflexively withdraw your hand. Which of the following statements about the reflex arc is NOT true? a) Action potentials are generated in the afferent pathway when a painful stimulus activates pain receptors, which then propagates the impulses to the dorsal horn of the spinal cord b) The spinal cord sends signals through the efferent pathway to contract and relax antagonistic muscles (e.g., biceps and triceps) to withdraw from the painful stimulus. c) Signals are transmitted to the brain through the ascending pathway, which allows the brain to have awareness of the pain beyond the reflex. d) NONE. All the above statements are true. 1  Quiz! You accidentally touch a hot pot on the stove and reflexively withdraw your hand. Which of the following statements about the reflex arc is NOT true? a) Action potentials are generated in the afferent pathway when a painful stimulus activates pain receptors, which then propagates the impulses to the dorsal horn of the spinal cord b) The spinal cord sends signals through the efferent pathway to contract and relax antagonistic muscles (e.g., biceps and triceps) to withdraw from the painful stimulus. c) Signals are transmitted to the brain through the ascending pathway, which allows the brain to have awareness of the pain beyond the reflex. d) NONE. All the above statements are true. 2 Midterm 1 Mean: 89.32% Median: 90% 3 Human Neuropsychology Lecture 7 BIO N173 / PSY 163/ PSYCH 162 Vision and Audition 4 Functional Anatomy of Vision 5  Subdivisions of the Occipital Cortex Primary Visual Cortex (V1) Laminar organization most distinct of all cortical areas Retinotopic mapping Has more than one distinct function Preserved in V2 Striate cortex: Another name for visual cortex due to its striped appearance 6  Subdivisions of the Occipital Cortex Color Vision Primary job of V4, but distributed throughout occipital cortex Plays a role in detection of movement, depth, and position V4 is now thought to process both color and form 7 What number do you see? 8 What number do you see? 9 What number do you see? 10 What number do you see? 11 What number do you see? 12  Color Blindness Color vision deficiency Affects a significant proportion of the population Overrepresented in males — genetic color blindness is X-linked and thus will tend to affect males more than females Caused by a deficiency in the development of one or more sets of retinal cones (red, blue, green) 13  Connections of the Visual Cortex Primary Visual Cortex (V1) Input from LGN Output to all other levels Secondary Visual Cortex (V2) Output to all other levels After V2 output to: Parietal lobe - Dorsal Stream Inferior temporal lobe - Ventral Stream Superior temporal sulcus (STS) [Ventral] 14 Dorsal vs. Ventral Pathways 15 Dorsal vs. Ventral Pathways 16 Summary of Visual System Anatomy 17 Visual field deficits 18 Scotomas - blindspots 19  Blindsight - A clinical case study Patient TN Two successive strokes knocked out V1 in both his left and right hemispheres. Complete cortical blindness. Yet TN could still navigate his environment without his cane! TN was examined by Lawrence Weiskrantz at Oxford University, who coined the term “blindsight” De Gelder et al. Current Biology 2008 20 21  Blindsight - detecting emotion Lesions to V1 produce cortical blindness in the visual field Although individuals cannot name the object in the lesioned portion of the visual field, they can react to it unconsciously Perhaps evidence for a more primitive form of vision? 22 Neural basis for unconscious vision? 23  Visual Agnosia Object Agnosia Apperceptive Agnosia Deficit in the ability to develop a percept of the structure of an object or objects Results from bilateral damage to the lateral occipital lobes Associative Agnosia Can perceive objects, but cannot identify them Results from lesions to the anterior temporal lobes 24 25 Prosopagnosia - a simulation 26 Prosopagnosia - a simulation 27 Prosopagnosia - another simulation 28 Prosopagnosia - another simulation 29 Auditory Processing 30  Pathways to the Auditory Cortex Auditory nerve (cranial nerve VIII) Carries auditory information from the ear to the CNS. Cochlear nucleus First neurons in the medulla that receive neural messages from auditory receptors via the auditory nerve. Superior olivary nucleus receives neural messages from the cochlear nuclei. Inferior colliculus receives information from both the cochlear nucleus and the superior olivary nucleus. 31  Pathways to the Auditory Cortex Medial geniculate nucleus (MGN) A1 tonotopic mapping Thalamic neurons receiving signals from the inferior colliculus. Primary auditory cortex (A1) The area of the temporal lobe that receives auditory input from the thalamus. Secondary auditory cortex The area of the temporal lobe surrounding the primary auditory cortex, where pitch, loudness, and timbre are perceived and specific sounds are recognized. 32  Hearing loss Cortical deafness damage to primary auditory cortex inability to perceive sounds despite intact ears Auditory Verbal Agnosia - AVA (pure word deafness) damage to posterior superior temporal lobes Note: inability to perceive words (cannot AVA is one component of Wernicke’s aphasia distinguish phonemes) We will discuss this more can still speak, read, write, and hear sounds when we talk about Language disorders 33  Musical Disorders Amusia An inability to recognize or reproduce music. Cannot perform fine pitch discrimination Congenital: tone deafness (4% of population) Acquired: due to organic brain damage Implicates the posterior superior temporal gyrus Perfect (Absolute) Pitch Ability to identify or recreate musical notes More common in those with Williams Syndrome or Autism More common in congenitally blind individuals 34