Human Neuropsychology Lecture 6: Functional Anatomy of the Nervous System - PDF

Human Neuropsychology Lecture 6 BIO N173 / PSY 163/ PSYCH 162 Functional Anatomy of the Nervous System 0 1 2 3  The Nervous System Functions Detect stimuli in the envir...

Human Neuropsychology Lecture 6 BIO N173 / PSY 163/ PSYCH 162 Functional Anatomy of the Nervous System 0 1 2 3  The Nervous System Functions Detect stimuli in the environment Recognize the significance of external stimuli Make decisions based on the significance Execute an appropriate response “Every function of the human body is under control of the nervous system” Gray’s Anatomy 40th ed. 4  Major Divisions The Peripheral Nervous System (PNS) Detect environmental stimuli Transmit information to the CNS Carry out orders given by the CNS The Central Nervous System (CNS) Receive and analyze information Make executive decisions Transmit decisions back to the PNS 5  Peripheral Nervous System Somatic Nervous System Afferent: carry information from sensory neurons to the CNS Efferent: carry information from the CNS to motor neurons Nerves are always in pairs, one efferent (motor) and one afferent (sensory) 31 pairs of spinal nerves 12 pairs of cranial nerves 6 PNS: Cranial Nerves (12 pairs) 7 PNS: Spinal Nerves (31 pairs) 8 Autonomic Nervous System The cervical nerves primarily serve somatic motor control and sensory function in the neck, shoulders, arms and diaphragm. Sexual Function: PANS initially promotes erection (vasodilation). SANS then controls ejaculation and vaginal contraction during orgasm (vasoconstriction). This ensures correct timing of things. Bladder Function: PANS contracts bladder and relaxes sphincter (urination). SANS relaxes bladder and contracts sphincter (urine storage). This prevents urination in stressful situations. 9 Components of the Reflex Arc 10 Fight or Flight Response 11  Central Nervous System Spinal cord Located in vertebrate spinal column. Limited analysis and decision making. Transmits information to and from the brain. Brain Located in the skull. Analyzes sensory information and makes appropriate responses. 12  Central Nervous System The Brain Weighs only about 1400 grams (2% of the average body weight). Complex structure is folded into gyri (hills) and sulci (valleys). Why is it folded like this? 13 14 Hindbrain (Rhombencephalon) Metencephalon Pons: sensory relay Cerebellum: maintaining posture, timing, planning movements, etc... Myelencephalon Medulla: controls basic life functions, e.g. breathing, heart rate, vomiting, etc. The medulla contains part of the reticular formation (reticular activating system) which plays a role in arousal and sleep regulation. 15  Midbrain (Mesencephalon) Mesencephalon Tectum (roof): contains the superior colliculus which control eye movements and the inferior colliculus which handles auditory information. Tegmentum (floor): contains part of the reticular formation, the substantia nigra which releases dopamine, the red nucleus which controls body movements. What happens if there is a problem with the substantia nigra that prevents it from producing enough dopamine? 16 Brainstem The brainstem consists of the hindbrain (metencephalon and myelencephalon) as well as the midbrain (mesencephalon). 17  Diencephalon Thalamus: a central relay station consisting of: Lateral Geniculate Nucleus (LGN): visual processing Medial Geniculate Nucleus (MGN): auditory processing Hypothalamus: involved in homeostatic control Pituitary gland: involved in hormonal control (master gland) Pineal gland: releases melatonin and is involved in sleep-wake cycle. 18  Telencephalon I: Limbic System The Limbic System: governs emotions such as anger, happiness, and fear and is involved in the storage and retrieval of memories. Includes hippocampus and amygdala. 19 Telencephalon II: Basal Ganglia Basal Ganglia Have widespread connections to the cortex and forebrain and are involved in the initiation of voluntary movements, maintaining muscle tone and posture Contain the caudate nucleus, the putamen, and the globus pallidus. The caudate nucleus and the putamen are referred to as the striatum due to their striped appearance. 20 Telencephalon III: Neocortex Occipital lobe—primary function is the analysis of visual information Parietal lobe—processes sensory information and is involved in spatial perception. Temporal lobe—processes auditory information and language (Wernicke’s area) Frontal lobe—motor programming, complex intellectual functioning, speech production (Broca’s area), personality, and executive function. 21  Cortical Homunculus Somatosensory and motor cortices have a physical representation of the body Wilder Penfield (1891-1976) 22 The Ventricular System 23  The Vascular System ~400 miles of blood vessels 24 The Vascular System 25  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