Olfactory system

Olfaction Cribiform plate Olfactory Receptor Medial Olfactory Striae Anterior Commissure Second Order Neurons Project IPSILATERALLY To Cortex WITHOUT STOPPING AT THALAMUS Lateral Olfactory Striae Primary Olfactory Cortex (surface of uncus overlying amygdala) Entorhinal Cortex: olfactory association area Nasal Mucosa Olfactory Bulb Olfactory Tract amygdala

Olfactory Cortex

Septal area & hypothalamus brainstem Medial forebrain bundle Stria medullary thalami Results salivation secretion in stomach

Limbic System Limbic = borderline

Outline Overview Hippocampal formation and Papez circuit Memory Memory impairment Amygdala Functions of the amygdala

Overview

Parahippocampal gyrus hippocampus amygdala Cingulate gyrus

hippocampus

Hippocampus (sea horse) Hippocampus

Ammon’s horn (Cornu Ammonis) Ammon’s horn (Cornu Ammonis)

Hippocampal Formation (Lateral View)

Hippocampal Formation (Medial View)

Hippocampal formation Hippocampus is one major part but often whole structure referred to as hippocampus. Other main part is dentate gyrus. curved structure found in floor of inferior horn of lateral ventricle Role in memory formation Spatial orientation

Hippocampal formation

Inputs to the Hippocampus entorhinal cortex  adjacent to hippocampal formation in parahippocampal gyrus  olfactory cortex  also receives projections from cingulate gyrus, prefrontal cortex, amygdala, other parts of temporal cortex contralateral hippocampus

4. Fascia dentata 3. CA4 2. CA3, CA2 1. CA1 6. Subiculum 20. Presubiculum 21. Parasubiculum 22. Entorhinal cortex 4. Fascia dentata 3. CA4 2. CA3, CA2 1. CA1 6. Subiculum 20. Presubiculum 21. Parasubiculum 22. Entorhinal cortex Division of Hippocampal Formation

Afferent Connections From Entorhinal Cortex Alveolar Path Alveolar Path from medial part of EC from medial part of EC to CA1 and Subiculum to CA1 and Subiculum Perforant Path Perforant Path from lateral part of EC from lateral part of EC to CA1, CA2, CA3 and to CA1, CA2, CA3 and Dentate Gyrus Dentate Gyrus From Entorhinal Cortex Alveolar Path Alveolar Path from medial part of EC from medial part of EC to CA1 and Subiculum to CA1 and Subiculum Perforant Path Perforant Path from lateral part of EC from lateral part of EC to CA1, CA2, CA3 and to CA1, CA2, CA3 and Dentate Gyrus Dentate Gyrus

Outputs from the Hippocampus To mammillary bodies via fornix Contralateral hippocampus also output to amygdala

Indusium griseum

JAMES PAPEZ ( )

Papez circuit Hippocampus Mammillary body anterior nucleus of the thalamus Cingulate Gyrus Parahippocampal Gyrus Mammillothalamic tract Fornix

Memory impairment bilateral destruction of temporal lobe structures leads to anterograde amnesia: inability to form new memories  bilateral removal of part of temporal lobes including hippocampus  cannot form new memories of events, names, etc. (declarative memory)  can learn new skills (non- declarative memory is intact)

Limbic Dysfunction – Memory Disorder Sergei Korsakoff ( ) Korsakoff’spsychosis

Korsakoff’s syndrome damage to mammillary bodies and DM of thalamus due to malnutrition, often a result of chronic alcoholism anterograde amnesia characterized by confabulation – make up explanations for events they don’t understand

Alzheimer's disease the degeneration and loss of cholinergic neurones in the nucleus basalis Meynert

Alzheimers’ Disease neurodegenerative disease amyloid proteins build up and form amyloid plaques (outside cells) neurofibrillary tangles inside cells leads to neuronal death hippocampus is one of first areas to degenerate, leads to anterograde amnesia cortex also degenerates early, leads to retrograde amnesia and dementia

Amygdala or amygdaloid nucleus actually a collection of nuclei beneath the uncus of the temporal lobe at the anterior end of the hippocampal formation and horn of lateral ventricle next to tail of caudate nucleus sometimes considered part of basal ganglia role in emotion

Amygdala Figure 12.18

Basal ganglia: Basomedial & central Olfactory:

Amygdaloid Nuclear Complex Amygdaloid Nuclear Complex “Emotion” & Amygdala

Connections of the Amygdala Amygdala Hypothalamus and septal area Prefrontal and cingulate cortex Olfactory cortex DM of thalamus Hippocampus (stria terminalis)

Stria Terminalis stria terminalis  projects to septal area and hypothalamus (mainly)  C-shaped course  travels with caudate nucleus

Septal area

What are emotions?

Limbic Function Functional Aspects of Limbic System Functional Aspects of Limbic System 1. Emotion - Affective Behavior 1. Emotion - Affective Behavior Amygdala – fear, aggression Amygdala – fear, aggression Nucleus accumbens, Septal nuclei – pleasure, reward Nucleus accumbens, Septal nuclei – pleasure, reward Limbic and Prefrontal Cortex Limbic and Prefrontal Cortex - Desire, Motivation, Goal-directed Behavior - Desire, Motivation, Goal-directed Behavior Hypothalamus and Brain Stem Hypothalamus and Brain Stem - ANS - maintenance of self (appetites) - ANS - maintenance of self (appetites) maintenance of species (sexual function) maintenance of species (sexual function) cf. Klüver-Bucy Syndrome cf. Klüver-Bucy Syndrome hyperphagia, hypersexuality, hyperorality, and.hyperphagiahypersexuality 2. Memory and Learning 2. Memory and Learning Papez Circuit Papez Circuit cf. Korsakoff’s syndrome cf. Korsakoff’s syndrome Functional Aspects of Limbic System Functional Aspects of Limbic System 1. Emotion - Affective Behavior 1. Emotion - Affective Behavior Amygdala – fear, aggression Amygdala – fear, aggression Nucleus accumbens, Septal nuclei – pleasure, reward Nucleus accumbens, Septal nuclei – pleasure, reward Limbic and Prefrontal Cortex Limbic and Prefrontal Cortex - Desire, Motivation, Goal-directed Behavior - Desire, Motivation, Goal-directed Behavior Hypothalamus and Brain Stem Hypothalamus and Brain Stem - ANS - maintenance of self (appetites) - ANS - maintenance of self (appetites) maintenance of species (sexual function) maintenance of species (sexual function) cf. Klüver-Bucy Syndrome cf. Klüver-Bucy Syndrome hyperphagia, hypersexuality, hyperorality, and.hyperphagiahypersexuality 2. Memory and Learning 2. Memory and Learning Papez Circuit Papez Circuit cf. Korsakoff’s syndrome cf. Korsakoff’s syndrome

53 Mesotelecephalic Dopamine System Nigrostriatal pathway: Green Mesocorticolimbic pathway: Red

Capgras’ syndrome Cognition without Emotion

Limbic system: Summary Hippocampus – role in memory Papez circuit: hippocampus  mammillary body  AV of thalamus  cingulate gyrus  parahippocampal gyrus  hippocampus Amygdala – role in emotion Memory  declarative vs. non-declarative  Working, short, intermediate, long-term  Amnesia: retrograde, anterograde, Korsakoff’s, Alzheimers

HIPPOCAMPUS Spatial memories in rodents & probably humans