Limbic System

Limbic System

\- is a rim of the cerebral cortex on the medial surface of each hemisphere

\- functions:

* *Olfaction*
* *Memory*
* *Emotion*
* *Homeostasis*

\- includes the:

* *cingulate gyrus*
* *parahippocampal gyrus*
* *hippocampus*
* *dentate gyrus*
* *fornix*

Cingulate Gyrus

\- lies above the pus callosum

\- “belt”

Parahippocampal Gyrus

\- located in the medial temporal lobe

\- regulates extreme emotion including rage and drive

Hippocampus

part of the limbic system responsible for learning and memory.

Dentate Gyrus

found between the hippocampus and parahippocampal gyrus.

Fornix

connection of the mammillary body and limbic area.

Orbitofrontal Cortex

\- mediates the conscious perception of smell

\- has reciprocal connection with the mediodorsal nucleus of thalamus

Mediodorsal Nucleus of the Thalamus

\- has reciprocal connections with the orbitofrontal and prefrontal cortex via the thalamus

\- receives input from the amygdaloid nucleus

\- since it has connections with the hypothalamus and amygdala, it has a direct connection with correct/appropriate emotion

Anterior Nucleus of the Thalamus

\- receives input from the mammillary nucleus via the mammillothalamic tract and fornix

\- projects to the cingulate gyrus

\- major link in the limbic circuit of Papez

* Hippocampal Formation
* Mammillary Body
* Thalamus
* Cingulate Gyrus

four structures that forms the circuit of Papez:

Circuit of Papez

\- very important for emotion, memory, learning, and social behavior

\- for appropriate maternal behavior; mother-child bond (some journals)

\- also observed in postpartum depression

\- strong projections with emotion and feeling of connectedness and bond

Septal Area

\- includes the paraterminal gyrus and subcallosal area

\- small subcortical region in the limbic system

\- directly related to emotion and social behavior

\- responsible for positive feelings of emotion and recognition of positive qualities of an individual

Limbic System

\- includes subcallosal area, paraterminal gyrus, cingulate gyrus, isthmus, and parahippocampal gyrus (uncus)

\- most do not have direct anatomical function (just connections) except, limbic lobe, amygdala, hippocampal formation, and dentate gyrus

Hippocampal Formation

\- functions in learning learning, memory, and recognition of novelty

\- distinct c-shaped characteristic; the bulge on the end of temporal lobe near lateral ventricle

\- receives major input via the entorhinal cortex

Hippocampal Formation

formed by the:

* *dentate gyrus*
* *subicular complex/subiculum*
* *parahippocampal gyrus*
* *entorhinal cortex*

Entorhinal Cortex

important in learning and memory; associates smell with memory.

Dentate Gyrus

\- contains granule cells that receive hippocampal input and project it to the pyramidal cells of the hippocampus and subiculum

\- lies between the fimbria of the hippocampus and the parahippocampal gyrus

\- continuation of subicular cortex/subiculum

\- an important limbic lobe area for connection of different memories (debatable)

Subiculum

\- receives input via hippocampal pyramidal cells

\- projects via fornix to mammillary nuclei and anterior nucleus of thalamus

\- has anatomical function for memory; processing of information about movement

Amygdaloid Complex

\- a basal ganglion underlying the parahippocampal uncus

\- is a continuation of the hypothalamus

\- function:

* associated with feeding and nutrition
* regulate unwanted behavior such as rage and aggression
* gives/subserves fibers to olfactory and cortex (relation with feeding and nutrition)

Corticomedial Group

olfactory input of the amygdala.

Basolateral Group

cortical input of the amygdala.

* Olfactory bulb and olfactory cortex
* Cerebral cortex
* Hypothalamus

major afferent connections to the amygdaloid complex.

Hypothalamus

\- is a major part of the limbic system that projects to the brainstem and spinal cord

\- functions:

* *visceral reflex center*


* *modulates the activity of lower visceral reflex centers*
* *adjuncts the activity of various visceral organs to match the physical activity and energy requirements of the person*

* Thermoregulatory center
* Satiety and hunger center
* Thirst center
* Maternal instinct center

four visceral reflex centers.

Thermoregulatory Center

for appropriate emotional reaction to different level of temperature.

Satiety and Hunger Center

for appropriate reaction to hunger.

Thirst Center

\- regulates salt-and-water balance

\- for appropriate reaction if thirsty

Maternal Instinct Center

divided into 2 reflex:

* *Milk Let Down Reflex*
* *Labor Contraction*

* Cardiovascular reflex center
* Swallowing reflex center
* Vomiting reflex center

\- three reflex centers (connection with the limbic system and medullary)

\- for an emotional reaction to noxious stimuli

* Micturition reflex center
* Defacation reflex center

\- two reflex center (connection with spinal cord and limbic system)

\- for peeing and defecation