Neuroscience Exam 3 - Gall - Lecture 3
|In which gyri of the brain do you find the limbic system?|| The gyrus rectus (medial to optic tract)|
Orbital frontal gyrus (lateral to optic tract)
Parahippocampal gyrus (medial to the temporal love).
|What are the components of the limbic system?|| - hippocampus |
- entorhinal cortex*,
- piriform cortex*
- septal nuclei
- cingulate cortex
- medial dorsal and anterior thalamic nuclei
- mammillary bodies
- Ventromedial (VM) hypothalamus
*Olfactory cortical areas
|Is the amygdala or the hippocampus not bounded by a ventricle?|| The amygdala. |
The amygdala is like an almost. The hippocampus is like a seahorse.
|On coronal cross section where is the amygdala?|| The most medial aspect of the temporal lobes. |
It is in the rostral temporal lobe, deep to the parahippocampal gyrus.
|On coronal cross section where is the hippocampus?|| The most medial aspect of the temporal lobes. |
The hippocampus is on the same plane as the amygdala, but it is located more caudally.
|What are the three main circuits of the limbic system?|| Amygdala circuit.|
|What are the three divisions of the amygdala?|| 1. Basolateral|
Note. These divisions of the amygdala are interconnected. So they communicate with one another.
|What are the four functions of the amygdala? (The four F's).||Important: Flight, fight, fear, fornication. |
- Fear, anxiety, emotion, aggression, mating, endocrine activities.
- Imposes cortical control over hypothalamic behaviors. This prevents you from doing inappropriate activities.
- Emotional memory (emotionally significant memories). Things with emotional memory have to be told only once and will remember.
- Implicated in depression, violent tendencies, impulsive behavior. SSRI's work on the amygdala. The amygdala is late to mature in development, it is not developed even in teens.
|Describe the corticomedial division of the amygdala.|| Receives olfactory input (from bulb mitral cells) |
Gives rise to efferents to the septal nuclei, olfactory tubercle and hypothalamus.
This region has important interconnections with the hypothalamus and is involved in sexual behavior.
|Describe the basolateral division of the amygdala.||Has bidirectional connections with all cortex (Neocortex, olfactory cortex, entorhinal cortex, hippocampus).|
Other efferents to mediodorsal thalamus, hypothalamus and brainstem autonomic centers. Relays projections to the frontal cortex. So can think of this division as the brain of the amygdala.
The Basolateral group is very important for some forms of learning (e.g., fear conditioning).
|Describe the central division of the amygdala.|| Bidirectional connections with hypothalamus and brainstem. |
Important for autonomic control as an output center.
It is highly responsive to stress.
|What is the larger point to see with the functional amygdala circuitry?|| Having olfactory input into the corticomedial division can get to the brainstem or hypothalamus. |
Or from the neocortex to the hypothalamus or brainstem.
|What are the three long paths that carry amygdala afferents and efferents.|| 1. Ventral amygdalofugal pathway|
2. Stria terminalis
3. Medial forebrain bundle
|Describe the ventral amygdalofugal pathway.|| connects amygdala with:|
mediodorsal (MD) thalamus, which goes to the orbital frontal cortex and back to the BLA.
|Describe the stria terminalis.|| Long arching pathway adjacent to the tail of the caudate.|
Interconnects amygdala with hypothalamus & septum.
This pathways arcs up over the thalamus.
|Describe the medial forebrain bundle.|| connects amygdala with:|
Phylogenetically old pathway connecting almost everything in its path from brainstem to orbital frontal cortex (like a freeway with onramps and offramps). Interconnects amygdala with brainstem, hypothalamus, frontal/olfactory cortex.
|What are the functions of the amygdaloid complex using the mnemonic A HOME.||A - autonomic controls, emotional influence over autonomic responses (sweating, crying, etc). |
H - hormonal reproductive functions (sexual behavior, ovulation, and abortion. Can stimulate different parts of the amygdala to do these functions).
O - olfactory relays influence over reproductive/endocrine functions.
M - memory, particularly with emotional coloring.
E - Emotional fear, rage, and placidity.
Note: the amygdala relays cortical control over all of the above functions.
|What is Kluver-Bucy syndrome?|| When have damage to the amygdala and get no cortical control. |
Get psychic blindness (troubling identifying how to use an object), oral and hypersexual tendencies.
|What are the major functions of the forebrain limbic system?||- "HOME" (Homeostasis, Olfaction, Memory, Emotion: important functions!)|
- Circuitry provides forebrain control of hypothalamus and its many functions as well as brainstem (arousal) influences on forebrain functions, such as learning and memory
- HM case (bilateral hippocampal damage) illustrates hippocampal function in declarative memory formation
- Damage to the amygdala disturbs emotional control and can lead to rage or placidity. Amygdala is also strongly implicated in depression
Clinical import: epilepsy, Alzheimer's disease, memory, depression
|Where is the amygdala located?|| Anterior temporal lobe. The amygdala is composed of a collection of nuclei in the central anterior temporal lobe, anterior to the hippocampus. |
It cannot be seen from the surface but is deep within the parahippocampal gyrus (the piriform cortex lies superficial to the amygdala).
|Note.||The major divisions of the amygdala are interconnected - thus information that is received in the corticomedial division will ultimately influence the basolateral and central divisions.|
|Note.||The basolateral division has bidirectional axonal connections with all fields of cortex (neocortex and olfactory cortex).|
|Note.||The corticomedial division is the target of afferents from olfactory bulb and olfactory cortex.|
|Note.||The amygdala projections to mediodorsal thalamus create an indirect link with frontal cortex (i.e., an amgdala -> Mediodorsal thalamus -> frontal cortex pathway).|