Neuro - relevant Anatomy and Physiology 2 Flashcards
What is Cognition?
The integration of all sensory information to make sense of a situation
What is the role of the Hippocampus in memory?
- Formation of memories
- Learning
What is the role of the Cortex in memory?
Storage of memories
What is the role of the Thalamus in memory?
Searches + Accesses memories
What is the role of the Amygdala and Cingulate gyrus in memory?
Emotion + memory
What is the Limbic system?
A collection of structures involved in processing emotion and memory
What are the structures of the Limbic system?
- Cingulate gyrus
- Thalamus
- Hypothalamus
- Amygdala
- Hippocampus
What type of memory loss do people have if they have bilateral hippocampal damage?
- central to learning and the formation of memories*
- unable to form long-term memories
- > although immediate (sensory) memory (seconds in length) and intact long-term memory (before the damage) is intact - reflexive memory (motor skills) also remains intact
What is immediate (or sensory) memory?
- a few seconds
- describes the ability to hold experiences in the mind for a few seconds
- based on different sensory modalities
- visual memories decay fastest (<1s), auditory ones slowest (<4s)
- nb. NOT THE SAME as working memory!!*
What is short-term memory?
- seconds-hours
- often called working memory
- used for short-term tasks ie. dialling a phone number, mental arithmetic, reading a sentence
- associated with reverberating circuits
What is immediate long-term memory?
- hours-weeks
- ie. what you did last weekend
- associated with chemical adaptation at the presynaptic terminal
What is long-term memory?
- can be lifelong
- ie. where you grew up, childhood friends
- associated with structural changes in synaptic connections
What is Anterograde Amnesia?
Which area is destroyed in this type of amnesia?
- inability to recall events that happen after the injury
- > depending on the severity of the injury, this can be short-lived or permanent
- destruction of the Hippocampus (ie. Clive wearing) results in permanent inability to form new memories
What is Retrograde Amnesia?
- can’t remember events leading up to the injury
- > although recall of events that happened a long time ago are still intact (as they are better rehearsed and more deeply embedded)
- often presents with anterograde amnesia - however, if only the thalamus is damaged, and the hippocampus is spared, only retrograde amnesia is seen (suggests thalamus is required for “searching” our existing memory bank)
What structural changes are involved at the post-synaptic cell for Long-Term memory?
Long Term Potentiation
- > (“strengthens the synapse”)
- > a well-established, well-rehearsed pattern of neuronal firing unique to that particular memory
What structural changes are involved at the post-synaptic cell for Immediate Long-Term memory?
- Involves chemical changes in the presynaptic neurones
- Increasing Ca2+ entry presynaptic terminals, increases NT release
What are the 2 main types of Long Term Memory?
1 - Declarative or Explicit Memory:
- Abstract memory for events (episodic memory) and for words, rules and language (semantic memory)
- Relies heavily on the Hippocampus
2 - Procedural/Reflexive/Implicit Memory:
- Acquired slowly through repetition -> includes motor memory for acquired motor skills such as playing tennis, and rules-based learning such as, in the UK, always driving on the left
- Thinking about these skills often impairs performance
- Based mainly in the Cerebellum
- Independent of Hippocampus (nb. Clive Wearing)
What is the Papez Circuit?
- If experience is considered useful, the Frontal cortex “gates” the so-called Papez circuit:
- Hippocampus -> Mammillary bodies -> Anterior Thalamus -> Cingulate gyrus
- Reverberating activity then continues between the Papez circuit, the Frontal cortex, the sensory and association areas until the consolidation process is complete
- Different components of the memory are laid down in different parts of the cortex ie. visual component in the visual cortex, auditory in the auditory cortex, etc
- Recall can be evoked by multiple associations -> many memories have strong emotional components to them ie. pleasant or unpleasant
How does Korsakoff’s syndrome affect memory?
- Vitamin B1 deficiency
- Leads to damage of Limbic system structures
- Leads to loss of ability to consolidate memories
How does REM sleep affect memory?
- Subjects deprived of sleep show impairment in memory consolidation for complex cognitive tasks
- Dreaming may enable memory consolidation -> reinforce weak circuits
- Pt’s with Korsakoff’s or Alzheimer’s have greatly reduced REM sleep (cholinergic neurones responsible for REM)
How does Alzheimers disease affect memory?
- Severe loss of cholinergic neurones throughout the brain, including the Hippocampus
- Gross impairment of memory
- Some improvement in Alzheimer’s may be seen with anti-cholinesterases, but underlying degeneration continues
- Unknown cause
