2 LIMBIC SYSTEM Limbic System works for 1. Emotion 2. Behavior 3. Motivation4. Memory (we will discuss in next lecture).
3 LIMBIC SYSTEM We will study Limbic System under the heading 1) History 2) Functional Anatomy3) Functions4) Experiments done in animals5) Chemical transmitters6) Clinical applications.
4 LIMBIC SYSTEM 1- History - Rhincephlon in RATS was first identified. Why it was named Rhincephalon?Because Rats are led by Olfactory stimuli.Than name was changed to LIMBIC SYSTEM because all animals are not guided by olfactory stimuli.
5 2. Functional Anatomy WHAT IS LIMBIC SYSTEM? It is ring of Fore brain structures that surround the brain stem2. Functional AnatomyLimbic System includesi). Amgdalaii). Hippocampusiii). Cingulate gyrusiv). Portions of hypothalamusv). Portions of thalamusVi) Portions of basal nucleivi). Portions of lobes of cerebral cortex [limbicassociation cortex]
8 Location of the Limbic System Figure 58-4; Guyton & Hall
9 LIMBIC SYSTEM Limbic System nuclei are connected by neuron pathway 3. We will discuss the functions of Limbic System1. Emotion2. Behavior3. Motivation
10 Functions 1. EmotionsEmotion means feelings, mood, anger, happiness, fear, and physical responses associated with these feeling e.g. laughing, cryingImportant – Input processed and giving rise to sensation of FEAR is in Amygdala, it lies in temporal lobe
11 Functions 2. BehaviorControl of behavior is under the limbic system and higher cortexe.g. behavior of survival – search for food, attack, socio-sexual behavior response
12 Functions 3. MotivationIt is well known that person reinforces behavior that has proved gratifying and suppresses that behavior which are associated with unpleasant experienceAreas in limbic system are named as- Reward center- Punishment center
13 Functions 3. Motivation [cont..] Why we call reward and punishment center?Because stimulation in these areas give rise to pleasant and unpleasant sensationsReward center – are found in regions of behavior activities of eating, drinkingPunishment center – are found in regions of pain
14 LIMBIC SYSTEM – Different areas Cingulate Gyrus Cingulate Gyrus – situated above corpus callosumFunctions- Sociable adaptable- Maternal behavior – care of offspring ( Animal who eat offspring has no cingulate gyrus)- Emotional behaviorDysfunction causes- Addictions to drugs– seeking pleasure
15 LIMBIC SYSTEM AMGDALA AMGDALA Functions - Sociability – more social, more friends- Fear response- Pleasure- Post traumatic stress- Aggression- Memory
16 LIMBIC SYSTEM Hippocampus Hippocampus – (Sea horse) Located in TemporallobeFunctions- Memory – Short term and Long term memory. If damage to hippocampus, patient cannot make long term memory.- damage causes anterograde amnesia
17 Hippocampus IMPORTANT FUNCTIONS [CONT..]reward and punishment determine whether or not information will be stored as memoryIf no reward or punishment, it is hardly remembered but a person learns any sensory experience that causes pain or pleasure and makes strong memory tracehippocampus provides the drive to rehearse and consolidate these sensory experiencesIMPORTANTFirst area to show damage in ALZEHIMER DISEASE is Hippocampus
18 Limbic Cortex FUNCTIONS cerebral association area functions for control of behaviorstimulation of various portions of this area can elicit almost all types of behavior in an animal
19 LIMBIC SYSTEM HYPOTHALAMUS Major part of Limbic system, it plays role in- Behavioral control , body temperature, osmolality of body fluids, control of body weight ( eating and drinking )- These internal functions are called VEGETATIVE functions of brain and are closely related to Behavior.
20 Hypothalamus major output pathway of the limbic system vegetative functions:neurogenic control of arterial pressureregulation of body temperatureregulation of fluid volumeregulation of endocrine gland secretiongrowth hormone, thyroid hormone, glucocorticoid secretion, sex hormones
21 Behavioral Functions of the Hypothalamus and Related Areas lateral hypothalamuseating, thirst, general level of activity, rageventromedial nucleussatiety, tranquillityperiventricular nucleusfear, punishment reactionsanterior and posterior hypothalamussexual drive
22 Functional Areas of the Hypothalamus Figure 58-6; Guyton & Hall
23 Behavior and its Control Reward and punishment causes the Limbic system so that we can learn. If no reward or punishment we ignore.Several limbic structures are concerned with sensory experience–is it pleasant or unpleasant?Reward center - the lateral and ventromedial hypothalamus, thalamus certain areas, Amygdala,Punishment center - located in hypothalamus and thalamus, Amygdala and HippocampusPunishment always takes precedent over reward.Punishment can frequently inhibit reward center.
26 4. Experiments done in rats - Experiments done in animals to see behavioral response to Reward and Punishment.- What was found ?- It was found if electrical stimulus is rewarding, animal presses the button more often , positive reinforcement.- But if electrical stimulus causes pain , animal decreases the rate of pressing the bar. So if punishment , we do not do the things again.
28 Emotional BehaviorCerebral cortex plays major role in directing many motor responses during emotional behavior e.g. to do or avoid situation, or modulation, or inhibition of emotional behavior.
29 5. NEUROTRANSMITTERS IN PATHWAYS OF EMOTIONS AND BEHAVIOR These are1. Norepinephrine2. Dopamine3. Serotonin
30 NEUROTRANSMITTERS IN PATHWAYS OF EMOTIONS AND BEHAVIOR Norepinephrine and dopamine are catecholamines, that are present in regions that elicit highest rate of self stimulation –DO IT YOURSELFThat is why amphatamine [stimulant] is used in depression. It causes increased release of dopamine from dopamine secreting neurons
31 OTHER EFFECT OF DOPAMINE Many drugs increase dopamine in pleasure pathways in limbic system, therefore, cause intense sensation of pleasure e.g. cocaineCocaine blocks re-uptake of dopamine at synapses
32 6. Clinical Application Limbic System defects 1- Depression It is psychiatric disorder associated with defect in limbic system neurotransmittersIn depression, neurotransmitter is decreased which is Norepinephrine or serotonin or bothNOTE – Depression is not neurological disorder i.e.there is no lesion in the brain
33 DEPRESSION Symptoms in depression are - Loss of interest - Negative mood- Inability to experience pleasure- Suicidal tendency
34 TREATMENT FOR DEPRESSION Anti-depressant drugs are used - Prozac – blocks re-uptake of released serotonin, therefore, there is increased serotonin at synapses - Amphetamine – causes increase release of Dopamine .
35 Clinical Application Alzheimer disease Memory loss- recent memory can not be converted to long term memory ( Ante grade Amnesia)