35: Limbic System Flashcards
Seven parts of the limbic system
- Subcallosum
- Cingulate gyrus
- Hippocampus
- Parahippocampal gyrus
- Amygdala
- Uncus
- Septal nuclei
Functions of limbic system
Integrate info from diverse brain areas to influence behavior, memory, and pain perception
Location of limbic system
Between hypothalamus + neocortex
Hypothalamus + limbic system
Anatomical basis for emotional, drive-related and motivated aspects of behavior
What is the Ammon horn?
The hippocampus proper
Uncal herniation
Uncus (and possibly parahippocampal gyrus) -> moves down over edge of tentorium cerebelli
Cause of uncal herniaton
Hemorrhagic lesion or tumor
Ipsilateral and contralateral S/S of uncal herniation
Ipsilateral: dilated pupil, abnl eye movements, double vision (CN 3 involvement)
Contralateral: weakness of extremities (CST involvement)
What can happen if uncal herniation progresses?
Respiration affected, abnl reflexes, potential rapid decline
Korsakoff’s syndrome: what happens in brain
Progressive degen of mammillary bodies, hippocampus, and dorsomedial thalamic nuclei
What causes Korsakoff’s syndrome
Thiamine deficiency, typically from chronic EtOH
S/S Korsakoff’s
Impedes retention of memory, difficulty learning new tasks, difficulty understanding written material and having convos, confabulation
Hippocampal amnesia deficits
Deficit in: anterograde episodic memory, spaced procedural and working memory
Cause of hippocampal amnesia
Bilateral lesion of hippocampus
Anosmia causes
Viral infection of olfactory mucosa, obstruction of nasal passages, congenital, shearing of CN1, tumor in floor of anterior cranial fossa
Phantosmia
Olfactory hallucination, distortion of smell experience of perception of a smell when none is present
Cause of phantosmia
Lesion in anteromedial temporal lobe; abnormal sequence of neuronal activity
Kluver-Bucy Syndrome cause
Bilateral temporal lobe lesion - abolished amygdaloid complex
S/s Kluver-Bucy Syndrome (6)
- Visual agnosia
- Hyperorality
- Hypermetamorphosis
- Placidity
- Hyperphagia
- Hypersexuality
Visual agnosia
Inability to recognize objects by sight
Hyperorality
Examines objects by mouth
Hypermetamorphosis
Compulsion to intensively explore immediate environment or overreact to visual stimuli
Placidity
Not showing anger/fear when thats appropriate
The Papez circuit
Description of an anatomicophysiologic mechanism for emotion
Idea behind the papez circuit
Emotions reach consciousness and conscious thought affects emotion -> neural circuit must exist between limbic system and cortical areas
Structures that are important in the Papez circuit
Diencephalon, cerebral cortex, cingulate gyrus ,fornix, amygdala
