ANATOMY OF LIMBIC SYSTEM
Terms
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- illustrate and describe the structures of the limbic system?
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The term "limbic" refers to the neural tissue that follows the lateral ventricles in their circular course. This tissue includes the cingulate and parahippocampal gyri, the uncus (including the hippocampus), and structures connected with them, such as the amygdala and hypothalamus.
Hippo is in the floor of the lateral ventricle, and the axons come around the thalamus
Lateral ventricle is a space, the ventricle is c shape and the bottom part of it is the inferior horn -
1. How is the PERIAMYGDALOID CORTEX and the AMYGDALA and the ENTORHINAL connected?
2. What is the role of the amygdala?
3. What are the 3 TEMPORAL CORTICAL AFFERENTS TO AMYGDALA AND HIPPOCAMPUS ? -
1. Peri and entor cover the amgdala. PERIAMYGDALOID CORTEX (1-2 layers): input from lateral olfactory stria. Amygdala is anterior to the foot of the hippocampus and HIPPOCAMPAL COMPLEX is also a cortical structure which lies hidden in the inferior horn of the lateral ventricle.
2. Anygdala is involved in:
the sensation of fear. This fear is not of anything particular in the environment but is described as nameless, uncanny, and impalpable.
NOTES:
Cortex of the rhinal fissure into H and Amyg so there is further processing that occurs in these medisal structures og the temporsl lobe
The amygdala is needed fr the fear reactiom…you get a nameless fear called “DREADâ€
You get perception of a truck coming at you = middle and inferior temporal gyri cause its fear of something not a nameless fear!
If you walk out in the lobby and you hgear rthe roaring of a lion, so it’s the supoerior temporal grus, casuse it’s the auditoiry systrem, so you fet fear
In hippocampus, the projections from the 3 gyri, sup, middle, inf….you can take out the hoppocampus and test the monkeys on simple memory and they are uninpaured!! So is it necessSY FOR memorory…there is a recpognotoion aspect = perorhinal…so take out H, the monkey is impaired in memory for diff oblects in space, not a single object but a bunch of them and the relation if diff objects to each othetr in space
The AMYGDALAS is a memory of a FEAR related!
3. The three TEMPORAL CORTICAL AFFERENTS TO AMYGDALA AND HIPPOCAMPUS
are:
-Complex auditory
-Complex visual
-Taste
NOTES:
Anterior portion of the insula is the primary taste cortex
Middle cderebral artery turns into the lateral fissure and from thgere it branches to come out to the enture surface of the brain
You see antreior cerebral artery
Taste is in the anterior insula? - What are the 5 inputs to the limbic system?
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-Olfactory
-Thalamus
-Superior temporal gyrus (auditory)
-Middle and inferior temporal gyri (higher order visual)
-Insula (gustatory) -
Distinguish between :
1. Lamina air flow
2. Turbulent air flow
3. How do the axons of olfactory cells travel? -
If you breathe in normally, the air flow is lamina or layeted so most of the air goers directly diw to the larynx, not nbasal cavity then to trachae but CN 1 are smnall cells in the nasal mucosa of the superior nasal concha and this means thsty lamina aur flow, air borne mopleculoes are sensed in the olfactory receptors cause they are un thye superior nasal concha and thyey synapse in tge olfactory lobe
Niffing†behavior
Smelling is a “sniffing behaviorâ€:- a narrow opening like the nostrils and you bring air in very fast, you now have turbulent flow not lamina flow!! The flow is too much thsty it moves everywhere! This in the nasal cavity, the air goes all the way up to the superior concha then you can smell or sniff rathger, primates have a very small olfasctory system like the rat!...has a system that is bigger than the human..see that the dog is always sniffing to produce turbulent flow..more sensitivity to airborne moleculers
3. Axons of olfactory cells travel through perforations in the cribriform plate of the ethmoid bone to synapse in the olfactory bulb.
Location of olfactory receptor cells (CNI), superior concha only - Describe the olfactory pathway?
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-The olfactory bulb receives the olfactory nerve (CN1).
-Axons from the olfactory bulb project via the olfactory tract and the lateral olfactory stria and medial olfactory stria to the primary olfactory cortex and the amgdala.
-the primary olfactory cortex overlies the uncus of the parahippocampal gyrus and it projects to the hippocampal formation via the entorhinal cortex.
-The lateral olfactory stria projects to the primary olfactory cortex and the amygdaloid nucleus.
-The primary olfactory cortex consists of the periamygdaloid cortices. -
1. Describe the CORTICOLIMBIC CONNECTIONS?
2. Describe the temporal neocortex and its 2 main areas? -
CORTICOLIMBIC CONNECTIONS
The cortex of the temporal lobe: A neural pathway for the perception, discrimination and memory for sounds, objects and faces.
2. TEMPORAL NEOCORTEX (6-layered):
a. Superior temporal gyrus
Perception of complex auditory stimuli, e.g., melody, rhythm, speech recognition. Auditory recognition memory (anterior third of this gyrus
Word deafness (planum temporale)
Auditory hallucinations of schizophrenia
b. Middle and inferior temporal gyri
Perception and identification of complex visual objects such as
size, color, texture, shape
Perception of faces
Mental imagery and memory for faces, animals, and colors of objects
Dream Imagery
Visual recognition memory (perirhinal cortex) - Describe the CORTICOCORTICAL AUDITORY CONNECTIONS?
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Input to hescl’s gyris is the medial geniculate- relay from the thalamus to the cortexa`
A sound reaches the hersclre gyris, starts from the spiral ganglion…it is a tonotopically organizesd cortex
There are a series if relays and at the temporal pole, the axons project to the meduasl portion of the temporal lobe
Superior temporal gyrus
Perception of complex auditory stimuli, e.g., melody, rhythm, speech recognition
Auditory recognition memory (anterior third of this gyrus
Word deafness (planum temporale)
Auditory hallucinations of schizophrenia - Describe CORTICOCORTICAL VISUAL CONNECTIONS?
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Middle and inferior temporal gyri
Perception and identification of complex visual objects such as size, color, texture, shape
Perception of faces
Mental imagery and memory for faces, animals, and colors of objects
Dream Imagery
Visual recognition memory (perirhinal cortex)
NOTES:
Inferior temporal gyri throygh a series of relay
No line btw the occipitasl lobre or temporal lobe
Middle and inferior temp gyri are continuums of higher visual sysytem
Neurins of the visual respond only to points of light but not to shape, motyion, only color, a lot of processing through the cortex is how you see shape
Cells in the visual association cortex will see a line composed of a series of fots and the cells can then see simpler pyramids…so lots of neurinal m,achinery that resolver complex shapes like the human FACE!!
If you destry here you get prosagnosia- can’t identify faces, where the face was is a huge bur, important because we are social animals and if we cannot see faces, it sux!
Cortical continues, so this cortex is perceptual in nature
MEDIAL VIEW
Visual sensation , whehn it reaches ther fissure, ther stram of relays terminate in the perirhinal cortex!! On either side of the rhinal fissure..line the walls. If this is removed bilaterallky the human cannot have RECOGNITION MEMORY because the perirhinal cortex is involved in recognition memory.
Train monleys to use ehat they saw b4
A patient
Took at the entire temporal lobe and the ppl could no longer form any new memories…so recognition mem, so cortex of the rthinal fissyre, wshich projects tyo the hippocapus sand the amygdala - Describe AMYGDALOID AND HIPPOCAMPAL EFFERENTS TO HYPOTHLAMUS?
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Trace further connections of the hippocampus
There are 2 ouptputs of the amygdala
-output of the stria terminjales under the latreal venbtril and goes to the paraventriclua layr of the tha;amus
-the more ventral psrt way goes to the hippocampal ouput to tge mamillary bodies
illustration of a frontal section taken at the level of the anterior temporal lobe, showing the cortico-limbic projections and the further relay into the hypothalamus. One of the hypothalamic nuclei receiving this information is the parvocellular division of the paraventricular hypothalamic nucleus. This nucleus is the origin of the descending autonomic connections to the preganglionic parasympathetic and sympathetic nerve cell bodies of the brainstem and spinal cord. -
1. Illustrate the circular nature of the limbic system and mention the role of the hippocampus, fornix, mammillothalamic tract, and the anterior thalamic nucleus.
2. What is the cingulum bundle? -
1. A lot in the limbic system is circular in nature
Fornix, mamillary body = project back to itself
The congulare gyrus has other connection too from others..these are the classical projections
Mamillary body = anteriorthal nucleus
Fgornix = tio mamillary body and the thalamus as well
Senspory info tp the limbic system and there are other outputs
2. The cingulul bundle is a relay between the cingulate gyrus and the hippocampus. - Describe the temporal lobe connections to the descending autonomic pathyways?
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A frontal section taken at the level of the anterior temporal lobe, showing the cortico-limbic projections and the further relay into the hypothalamus. One of the hypothalamic nuclei receiving this information is the parvocellular division of the paraventricular hypothalamic nucleus. This nucleus is the origin of the descending autonomic connections to the preganglionic parasympathetic and sympathetic nerve cell bodies of the brainstem and spinal cord. According, they are the final stage in the route by which complex sensory experiences influence autonomic reflexes, such as salivation and blood pressure (baroreceptor) control.
NOTES:
Hypothalamus is the central psrt for the endocrine system and the autonomic nervous system
The hypo gets inputd from the amygdalsa and the hippocasmpus, visual traste, and auditii is projected to the hypo by the amygdalsa abnd the hippocampis
ANS gets info about the external wordl by way of this pasrhway, the internal organs react to it
Series of connection into the hypotahlamis prepaes the body fgor flight or foght, means thsat the muscles work hard, need more oxygen so the ANS are in atagonism so we need to tilt toards the sympa and shut off the parasym so this is the heasdquaters
The axons feed back to the pre gabg and gang of the ANS, so go to the intermediolatral, or pre gang, superior salivatory⬦this nucleus will dsampen down the para
The pupillary dilation is a sighn of fear so projection to edinger is inhibiyrd but innervation for pupil dilation is increasond so gerere is an effect of the hypothalamic control of the ANS
THE cortex has holes, so there is dementia because the nberve cekls are gone so there is expansionand the latreal ventricle and 3rd gets big, there is also larger sulci as well! There are pinoles and tge remaining structures are just glial in the brain
The basilar artery
Know about the anterior cerebral artery as it goes on top and around
The lower
Destro the mifdle of the anterior cerebral artery, the sympyoms will be in the lower representation of the body
Motor cortrex affected will derstupy foot and leg
These axons project to the corticospinal ral horrn tract, they are contralatral and they terminate in the vental ⬦so you get an upper motor neuron lesion
What cortex for the face?? You will see the corticobulbar that has bilteral , so not an upper motor neuron weakness
Where is the tongue representation⬦LEARN YOUR HOMONCULUS!!!! -
1. Discuss temporal lobe epilepsy?
2. Discuss Horner's syndrome? -
1. 1. Temporal lobe epilepsy.
Symptoms
Sensory: Hallucinations in the auditory, visual, olfactory, visceral, gustatory, and vestibular modalities. Episodes of déjà vu; episodes of macropsia/micropsia.
Motor: Automatic movements, such as vacant staring, chewing, swallowing, laughter, clapping, meaningless movements; frequent dizzy spells, falling episodes or blackouts unrelated to alcohol or drug use.
Cognitive: Periodic loss of fully conscious contact with reality, loss of memory for specific acts (violent or nonviolent) followed by confusion, headache, sleep or fatigue; episodes of inability to understandconversations despite of awareness that people are speaking; episodes of dreamy states; episodes of forced thinking.
2. HORNER’S SYNDROME
A disconnection of the descending autonomic pathway from the preganglionic sympathetic nerve cell bodies of the intermediolateral column of the spinal cord, T1-L4, after which the following signs appear.
Miosis, a constricted pupil due to the unopposed action of the pupillary muscle.
Pseudo-ptosis, a drooping eyelid due to paralysis of the superior tarsal muscle.
Anhydrosis, an inability to activate the sweat glands.
Ppl with a cut at the cervical level isolated from upper control so if no construction the blod vesseks are open, makes the face wardm, darkens the skin