1 Functional Neuroanatomy

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(1)Cambridge University Press 978-0-521-10645-0 - Comprehensive Psychiatry Review William Weigi Wang Excerpt More information. PART I. INTELLECTUAL FOUNDATION OF PSYCHIATRY. 1 Functional Neuroanatomy. Once upon a time, psychiatric conditions were divided into “organic” and “functional,” based on whether there was an observable structural or chemical deviation. This categorization is no longer meaningful. Scientific researches continue to find more and more anatomical structures that have a tangible connection to the neuronal functions with which most psychiatrists are concerned: mood, thought, cognition, behavior, and also movement and sensation. Changes in these structures, often at microscopic scale, may have significant impact on mental function. Knowledge of these anatomical structures is essential in understanding the biological aspect of psychiatry. The general organization of the central nervous system is presented in Figure 1–1. Anatomy of the spinal cord is not reviewed here because of its relatively limited application in common psychiatric disorders. Selected topics on spinal cord anatomy are reviewed in Chapter 43, in combination with spinal cord diseases.. Cerebrum Cerebral cortex Basal ganglia Olfactory bulb (CN I) Amygdala Basal ganglia Caudate Cingulate Globus pallidus Heschl’s gyri Hippocampus Rolandic fissure Sylvian fissure Limbic system Nucleus accumbens Prefrontal cortex Primary sensory cortex Putamen Substantia nigra Striatum Ventral tegmental area. Cerebellum Anterior lobe Posterior lobe Flocculonodular lobe Brainstem Diencephalon (CN II) Midbrain (CN III–IV) Pons (CN V–VIII) Medulla (CN IX–XII) Hypothalamus Limbic system Reticular formation Spinal cord Cervical nerves (8 2) Thoracic nerves (12 2) Lumber nerves (5 2) Saccral nerves (5 2) Coccygeal nerve (1) Dermatones. Figure 1–1 General organization of the central nervous system. Only the major structural components are labeled. Structures described in this chapter are listed in italic font.. 1. © in this web service Cambridge University Press. www.cambridge.org.

(2) Cambridge University Press 978-0-521-10645-0 - Comprehensive Psychiatry Review William Weigi Wang Excerpt More information. 2. Part I. Intellectual Foundation of Psychiatry. Hypothalamus Nuclei of CN V Nuclei of CN VII. Amygdala. VTA Locus coeruleus. Figure 1–2 Amygdala output connections. The inlet shows amygdala in an MRI coronal section. Abbreviations: MRI stands for magnetic resonance imaging; VTA stands for ventral tegmental area.. Amygdala: anatomy (Figure 1–2) From Greek, “almond.” Groups of neurons deep within the medial temporal lobes An essential part of the limbic system Involved in memory, emotional reactions, and appetite conditioning Output to: 4 Hypothalamus : activation of the sympathetic nervous system 4 Nuclei of the trigeminal nerve (CN V) and facial nerve (CN VII): facial expressions 4 Ventral tegmental area (VTA): activation of dopamine 4 Locus coeruleus : activation of norepinephrine. Amygdala : roles in anxiety and fear Mediates learned fear responses Directs the expression of certain emotions Exerts influence on the cortex Damage to the amygdala may ablate the ability to distinguish fear and anger Positron emission tomography (PET) shows that harm avoidance is associated with increased activity in the right amygdala and other structures. Auditory system Peripheral system: 4 Changes of air pressure form sounds 4 Vibration of tympanic membrane. © in this web service Cambridge University Press. www.cambridge.org.

(3) Cambridge University Press 978-0-521-10645-0 - Comprehensive Psychiatry Review William Weigi Wang Excerpt More information. Chapter 1. Fuctional Neuroanatomy. 3. Caudate nucleus Putamen & globus pallidus. Amygdala Nucleus accumbens Subthalamic nucleus Substantia nigra. Figure 1–3 Components of basal ganglia.. 4 Vibration is transmitted through ossicles to the endolymph of the cochlear spiral 4 Vibrations of the endolymph move cilia on hair cells 4 Hair cells generate neural impulses Central system: 4 Neural impulses travel through cochlear nerves to cochlear nuclei (brainstem) 4 Then the impulses travel to the medial geniculate nucleus (MGN, at thalamus) 4 MGN projects to the primary auditory cortex (Heschl’s gyri ). Basal ganglia (Figure 1–3) Anatomical components: 4 Putamen 4 Caudate nucleus 4 Nucleus accumbens 4 Globus pallidus 4 Subthalamic nucleus 4 Substantia nigra Function (consists of a series of circuits that are associated with a variety of functions): 4 Motor control 4 Cognition 4 Emotions 4 Learning. Caudate nucleus Anatomy: 4 Part of basal ganglia 4 Together with putamen, forms the dorsal striatum 4 Separated from the lenticular nucleus by the internal capsule. © in this web service Cambridge University Press. www.cambridge.org.

(4) Cambridge University Press 978-0-521-10645-0 - Comprehensive Psychiatry Review William Weigi Wang Excerpt More information. 4. Part I. Intellectual Foundation of Psychiatry. Superior sagittal sinus. Arachnoid granulations. Subarachnoid space. Choroid plexus of lateral ventricle Dura mater. Choroid plexus of third ventricle Choroid plexus of fourth ventricle. Figure 1–4 Flow of cerebrospinal fluid.. Blood Cerebrospinal fluid. Median aperture. Central canal. Function: 4 Important part of the learning and memory system Neurochemistry: 4 Highly innervated by dopamine neurons 4 These neurons originate mainly from the VTA and the substantia nigra. Cerebellum function Activated before a planned – or even imagined – movement Modulates the tone of agonistic and antagonistic muscles Predicts the relative contraction needed for smooth motion. Cerebrospinal ﬂuid: formation and absorption (Figure 1–4) Formation: 4 Choroid plexuses of lateral, third, and fourth ventricles Flow: 4 Choroid plexuses 4 Ventricles 4 Median aperture (foramen of Magendie) or lateral apertures (foramina of Luschka) 4 Subarachnoid space Absorption: 4 Through arachnoid granulations, also known as arachnoid villi 4 To the superior sagittal sinus or venous lacunae. Cingulate Anatomy: 4 A gyrus between the corpus callosum and the cingulate sulcus 4 An integral part of the limbic system. © in this web service Cambridge University Press. www.cambridge.org.

(5) Cambridge University Press 978-0-521-10645-0 - Comprehensive Psychiatry Review William Weigi Wang Excerpt More information. Chapter 1. Fuctional Neuroanatomy. Lateral ventricles. 5. Thalamus. Caudate nucleus. Internal capsule. Putamen. Amygdala. . Third ventricle. Figure 1–5 Coronal cut shows globus pallidus and its surrounding structures.. Function: 4 Emotion formation and processing 4 Learning 4 Memory 4 Unconscious priming. Glial cells Astrocytes: 4 Most common type of glial cells 4 Nutritional support to neurons 4 Deactivation of neurotransmitters 4 Integration with the blood-brain barrier Oligodendrocytes: 4 Appear only in the central nervous system 4 Form myeline sheaths Schwann cells: 4 Appear only in the peripheral nervous system 4 Form myeline sheaths 4 Remove cellular debris. Globus pallidus (Figure 1–5) Anatomy: 4 A subcortical structure 4 A major element of the basal ganglia 4 Forms the dorsal striatum Function: 4 Involved in the regulation of voluntary movements at a subconscious level 4 Probably involved in physiological pace-making. © in this web service Cambridge University Press. www.cambridge.org.

(6) Cambridge University Press 978-0-521-10645-0 - Comprehensive Psychiatry Review William Weigi Wang Excerpt More information. 6. Part I. Intellectual Foundation of Psychiatry. Figure 1–6 Heschl’s gyri, the primary auditory cortex. It is the first cortical structure to process incoming auditory information from the medial geniculate nucleus (MGN).. Heschl's gyri. Heschl’s gyri (Figure 1–6) Richard Heschl (1824–1881) was an Austrian anatomist. Also known as the transverse temporal gyri or Heschl’s convolutions Located bilaterally in the primary auditory cortex in the superior temporal gyrus Receives auditory stimuli from the contralateral ear Supplied by the middle cerebral artery. Hippocampus From Latin, “sea horse.” Located in the medial temporal lobe Part of the limbic system Plays an important role in memory and spatial navigation. Hypothalamus Anatomy: 4 Located below the thalamus, just above the brain stem 4 Occupies the major portion of the ventral region of the diencephalon Function: 4 Links the nervous system to the endocrine system via the pituitary gland (hypophysis) 4 Synthesizes and secretes hypothalamic-releasing hormones, and these in turn stimulate or inhibit the secretion of pituitary hormones 4 Regulates certain metabolic processes and other autonomic activities – body temperature, hunger, thirst, and circadian cycles. © in this web service Cambridge University Press. www.cambridge.org.

(7) Cambridge University Press 978-0-521-10645-0 - Comprehensive Psychiatry Review William Weigi Wang Excerpt More information. Chapter 1. Fuctional Neuroanatomy. 7. Rolandic fissure. Sylvian fissure. Figure 1–7 Rolandic fissure and Sylvian fissure.. Important brain ﬁssures (Figure 1–7) Luigi Rolando (1773–1831) was an Italian anatomist. Franciscus Sylvius (1614–1672) was a German-Dutch physician and anatomist. Rolandic fissure: 4 Also known as the central sulcus or fissure of Rolando 4 Separates the parietal lobe from the frontal lobe, and the primary motor cortex from the primary somatosensory cortex Sylvian fissure: 4 Also known as the lateral sulcus or lateral fissure 4 Divides the frontal and parietal lobes from the temporal lobe. Limbic system Anatomy (major components as listed): 4 Amygdala 4 Cingulate gyrus 4 Hippocampus 4 Hypothalamus 4 Mammillary body 4 Nucleus accumbens 4 Orbitofrontal cortex 4 Thalamus Function: 4 Pleasure 4 Sexual arousal 4 Health consciousness 4 Not completely understood. © in this web service Cambridge University Press. www.cambridge.org.

(8) Cambridge University Press 978-0-521-10645-0 - Comprehensive Psychiatry Review William Weigi Wang Excerpt More information. 8. Part I. Intellectual Foundation of Psychiatry. Nucleus accumbens (Figure 1–3) Location: the head of the caudate and the anterior portion of the putamen Neurobiological role: 4 Reward 4 Pleasure 4 Addiction Neurotransmitter: 4 Mainly gamma-aminobutyric acid (GABA) 4 Some cholinergic interneurons Associated with the action of addictive drugs such as cocaine and amphetamine; almost every drug abused by humans has been shown to increase dopamine levels in the nucleus accumbens. Prefrontal cortex Anterior part of the frontal lobes, generally involved in executive function (regulating thoughts and actions in accordance with internal goals) Orbitofrontal cortex: 4 Decision making 4 Emotion and reward 4 Part of the limbic system Medial prefrontal areas 4 Planning complex cognitive behaviors 4 Personality expression 4 Moderating appropriate social behavior. Primary sensory cortex Lateral postcentral gyrus in the parietal lobe Roughly overlaps with Brodmann areas 3, 1, and 2 Receives the thalamocortical projection from the sensory input fields. Putamen (Figure 1–3) From Latin, “shell.” Anatomy: 4 Part of basal ganglia 4 Dorsal striatum 4 Outermost part of the lenticular nucleus (the inner part is globus pallidus ) Function: 4 Not well defined 4 Likely to play a role in reinforcement learning. Reticular formation Also known as the reticular activating system Anatomy: 4 Centered in the pons, connected to the thalamus, hypothalamus, cortex, and cerebellum. © in this web service Cambridge University Press. www.cambridge.org.

(9) Cambridge University Press 978-0-521-10645-0 - Comprehensive Psychiatry Review William Weigi Wang Excerpt More information. Chapter 1. Fuctional Neuroanatomy. 9. Function: 4 Arousal and motivation 4 Maintaining the state of consciousness 4 Circadian rhythm. Reward system Primarily involves the mesolimbic and mesocortical dopamine pathway Anatomical structures include VTA, nucleus accumbens, substantia nigra, and prefrontal lobe. Substantia nigra (Figure 1–3) From Latin, “black substance.” A heterogeneous portion of the midbrain A component of basil ganglia Center of dopamine production Plays a central role in the reward system and addiction. Striatum A subcortical structure of telencephalon, it consists of: 4 Putamen 4 Caudate nucleus Striatum is the major input station of basal ganglia. Ventral tegmental area Also known as ventral tegmentum Is part of the midbrain Consists of dopamine, GABA, and glutamate neurons Is part of two major dopamine pathways 4 The mesolimbic pathway, which projects to the nucleus accumbens 4 The mesocortical pathway, which projects to cortical areas in the frontal lobes Functions: 4 Part of the reward system 4 Emotion and security motivation 4 Avoidance and fear-conditioning. © in this web service Cambridge University Press. www.cambridge.org.

(10) Cambridge University Press 978-0-521-10645-0 - Comprehensive Psychiatry Review William Weigi Wang Excerpt More information. 2 Neurochemistry. The synthesis, metabolism, transportation, interaction, and other behaviors of neurochemicals play important roles in mental activities. Two major categories of neurochemicals are studied in psychiatry: neurotransmitters and neuroactive drugs. This chapter reviews the important neurotransmitters, which include Acetylcholine Dopamine Gamma-amino butyric acid (GABA) Glutamate Glycine Histamine Melatonin Norepinephrine Serotonin. Acetylcholine synthesis and metabolism (Figure 2–1) Theodor Meynert (1833–1892) was a German-Austrian neuropathologist and anatomist. Location 4 Basal nucleus of Meynert at basal forebrain Precursors 4 Acetyl-CoA and choline Metabolism 4 Breaks down to acetyl-CoA and choline 4 Catalyzed by acetylcholinesterase in the synaptic cleft. Adrenergic ³-1 antagonism: clinical effects Sedation Orthostatic hypotension Priapism. Adrenergic ³-2 receptor Presynaptic receptors provide negative feedback on the release of serotonin and norepinephrine Agonists – decreases serotonin and norepinephrine release 4 Clonidine – sympatholytic action; helpful in opiate withdrawal Antagonists – increases serotonin and norepinephrine release 10. © in this web service Cambridge University Press. www.cambridge.org.

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