By:- Hina Khalid

Introduction of limbic system Anatomy, physiology of limbic

system Structures of Limbic system Functions of structures Related prblems

The term "limbic" comes from the Latin limbus, for "border" or "edge.

The set of brain structures that forms the inner border of the cortex.

System is the area of the brain that regulates emotion and memory.

It includes many structures in the cerebral pre-cortex and sub-cortex of the brain .

The term has been used within psychiatry and neurology.

The definition of the limbic system is still evolving. Broca,s (1878) “limbic lobe” was primarily cortical. The Kluver-Bucy syndrome (1937-1939): Bi-lateral

temporal lobectomy in monkeys produced: visual agnosias (“psychic blindness”:cannot recognize the meaning of objects),oral tendencies

compulsion to react to every visual stimulus, changes in emotional behavior, in dietary habits, and in sexual behavior.

Upon histology, they found that the lesion involved temporal association cortex, the amygdala, the hippocampus, and the fornix (connects the hippocampus to the septal nucleus and hypothalamus).

was delineated by James Papez,The Papez circuit consists of

Hippocampus Fornix mamillary bodies anterior nucleus of the thalamus cingulate gyrus. boundaries of the limbic system were subsequently

expanded to include the amygdala, septum, basal forebrain, nucleus accumbens, and orbitofrontal cortex.

Amygdale; almond shaped mass of nuclei involved in emotional responses, hormonal secretions, and memory.

Cingulate gyrus; a fold in the brain involved with sensory input concerning emotions and the regulation of aggressive behavior.

Fornix; an arching, fibrous band of nerve fibers that connect the hippocampus to the hypothalamus.

Hippocampus; a tiny nub that acts as a memory indexer -- sending memories out to the appropriate part of the cerebral hemisphere for long-term storage and retrieving them.

Plasticity and Attention Responding to stress Learning about emotional stimuli learning, or classical conditioning Affective state Memory Feelings of pleasure that are related to our survival,

such as those experienced from eating and sex New memories(damage to this area of the brain may

result in an inability to form new memories)

•The Amygdala is important for making associations across stimulus modalities (a certain fragrance often elicits an associated visual image).It appears to be responsible for the influence of emotional states on sensory inputs.•This produces a spectrum of sensory perceptions from apparently identical stimuli (ex. the sound of one's own motorcycle is never perceived as noise). Thought to be responsible for face recognition.

The amygdala involved in many cognitive processes.

Just like in the hippocampus, memory seems to be impacted by processes in the amygdale; however, it is not spatial memory like the hippocampus, but episodic-autobiographical memory (EAM) networks.

The amygdala, as researched by Markowitsch

was found to be responsible for the encoding, storage, and retrieval of these types of memories.

Besides memory, the amygdala also seems to be an important brain region involved in socialization fear attention and emotional processes.

Pessoa generalized this concept with help from evidence of EEG recordings, and concluded that the amygdala helps an organism to define a stimulus and therefore respond accordingly the amygdala was initially thought to be linked to fear, this gave way for research in the amygdala for emotional processes, anxiety disorders.

The Cingulate (to surround) Gyrus (fold), is part of the cerebrum gray matter surrounding and directly connected to the parts of the inner Limbic System. The Cingulate Gyrus serves as a conduit of messages to and from the inner Limbic System.

 

An arching, fibrous band of nerve fibers that connect the hippocampus to the hypothalamus.

The hypothalamus sits under the thalamus at the top of the brainstem. Although the hypothalamus is small, it controls many critical bodily functions:

Controls autonomic nervous system Center for emotional response and behavior Regulates body temperature Regulates food intake Regulates water balance and thirst Controls sleep-wake cycles Controls endocrine system

The Hippocampus is very important in the transition of information from short to long term memory

It is also part of the Temporal Lobe, damage to that portion of the brain can result in a loss of memory.

The size of a pearl, this structure directs a multitude of important functions. It wakes you up in the morning, and gets the adrenaline flowing.

The hypothalamus is also an important emotional center, controlling the molecules that make you feel exhilarated, angry, or unhappy.

 

The mammillary bodies (mamillary bodies) are a pair of small round bodies, located on the undersurface of the brain, that, as part of the diencephalon form part of the limbic system. They are located at the ends of the anterior arches of the fornix. They consist of two groups of nuclei, the medial mammillary nuclei and the lateral mammillary nuclei . Neuroanatomists have often categorized the mammillary bodies as part of the hypothalamus

FunctionsThey, along with the anterior and dorsomedial nuclei in the thalamus, are involved with the processing of recognition memory.

They are believed to add the element of smell to memories.

The hypothalamus is shaded blue. The pituitary gland extends from the hypothalamus.

It is also part of the Temporal Lobe, damage to that portion of the brain can result in a loss of memory.

The size of a pearl, this structure directs a multitude of important functions. It wakes you up in the morning, and gets the adrenaline flowing.

The hypothalamus is also an important emotional center, controlling the molecules that make you feel exhilarated, angry, or unhappy.

 

The Hippocampus is very important in the transition of information from short to long term memory

It is also part of the Temporal Lobe, damage to that portion of the brain can result in a loss of memory.

The size of a pearl, this structure directs a multitude of important functions. It wakes you up in the morning, and gets the adrenaline flowing.

The hypothalamus is also an important emotional center, controlling the molecules that make you feel exhilarated, angry, or unhappy.

 

It has been demonstrated to be involved in various processes of cognition. The first and most widely researched area concerns memory, spatial memory in particular.

Spatial memory was found to have many sub-regions in the hippocampus, such as the dental gyrus (DG) in the dorsal hippocampus, the left hippocampus, and the Para hippocampus region.

The dorsal hippocampus was found to be an important component for the generation of new neurons, called adult-born granules (GC).

Over the decades, has also been found to have a huge impact in learning.

Hippocampus damage Damage relayed to the hippocampus region of

the brain has reported vast effects on overall cognitive functioning, particularly memory such as spatial memory.

Researchers particularly investigated the effects that high emotional arousal and certain types of drugs had on the recall ability in this specific memory type.

Lines the walls of 3rd ventricle, above the pituitary.

Divided into medial and lateral regions by the fornix, bundles of fiber tracts that connect the hippocampus to the mamillary bodies.

The hypothalamus is a grouping of nuclei that lie along the base of the brain near the pituitary gland.

The hypothalamus connects with many other regions of the brain and is responsible for controlling hunger, thirst, emotions, body temperature regulation, and circadian rhythms The hypothalamus also controls the pituitary gland by secreting hormones, which gives the hypothalamus a great deal of control over many body functions.

A major function of the nervous system is to maintain homeostasis, or the stability of the internal environment.

The hypothalamus, which comprises less than 1% of the total volume of the brain, is intimately connected to a number of structures within the limbic system and brainstem.

Together the hypothalamus and the limbic system exert control on the endocrine system the autonomic nervous system to maintain homeostasis.

Emotions and motivated behavior are crucial for survival: Emotional responses modulate the autonomic nervous

system to respond to threatening stimuli or situations. Emotional responses are adaptive. If you are prepared to

deal with threatening stimuli, you are more likely to survive and reproduce.

Motivated behavior underlies feeding, sexual and other behaviors integral to promoting survival and reproduction.

Fever ; Need to detect temperature changes and modulate the autonomic nervous system to either retain or dissipate heat.

Addiction ; Many recreational drugs work through neural pathways involved in reward and motivated behavior that form an important part of limbic system function.

Anxiety Disorders; Many anxiety disorders, such as Panic Disorder and Post-traumatic stress disorder have physiological symptoms mediated by the autonomic nervous system and by the limbic system.

Obesity ; Feeding behavior is in part controlled by the hypothalamus, and interactions between limbic reward circuitry and the hypothalamus are important to feeding behavior.

The structures of higher olfactory processing in phylogenetically more primitive animals have evolved in humans into the limbic system, the center of the emotional brain and the gate through which experience is admitted into memory according to emotional significance.

Alzheimer's changes the whole brain Alzheimer's disease leads to nerve cell death and

tissue loss throughout the brain. Over time, the brain shrinks dramatically, affecting nearly all its functions.

In the Alzheimer's brain: The cortex shrivels up, damaging areas

involved in thinking, planning and remembering.

Shrinkage is especially severe in the hippocampus, an area of the cortex that plays a key role in formation of new memories.

Ventricles (fluid-filled spaces within the brain) grow larger

Alzheimer's tissue has many fewer nerve cells and synapses than a healthy brain

Plaques, abnormal clusters of protein fragments, build up between nerve cells.

Dead and dying nerve cells contain tangles, which are made up of twisted strands of another protein.

The hypothalamus just above the brain stem, acts as an integrator for autonomic functions, receiving ANS regulatory input from the limbic system to do so.

Amnesia patients have trouble retaining long term memories.

Difficulty creating recent term lost of memories is called intergraded amnesia and is caused by damage to the hippocampus part of the brain which is a major part of the memory process.

Retrograde amnesia is also caused by damage to the hippocampus but the memories that were encoded or in the process of being encoded in long term memory are erased.

The limbic system has been particularly implicated in neuropathological studies of schizophrenia.

Several clinicopathological studies have found a reduction in the brain weight of the gray matter but not of the white matter in persons with schizophrenia.

In pathological as well as in magnetic resonance imaging (MRI) reports, persons with schizophrenia may have reduced volume of the hippocampus, amygdala, and parahippocampal gyrus.

During the hallucinations, the same cortical and subcortical structures were activated as were activated by the actual sounds, including the primary auditory cortex. At the same time, decreased activation was seen of areas thought to monitor speech, including the left middle temporal gyrus and the supplementary motor area.

Neuropathological studies have shown a decreased density of neuropils, the intertwined axons and dendrites of the neurons, in the frontal lobes of these patients.

Tucker, D. M., Derryberry, D., & Luu, P. (2000). Anatomy and Physiology of Human Emotion:

Vertical Integration of Brainstem, Limbic, and Cortical Systems. In J. Borod (Ed.),

Handbook of the Neuropsychology of Emotion. New York: Oxford.

Wada G Webb.,Richard K .Adler(4th edition)(2008)NEUROLOGY for the Speech-Language

Pathology.