Lecture 12 - The Ancient Forebrain - Basal Ganglia, Hippocampus and Amygdala Flashcards
How many nuclei does the basal ganglia encompass?
putamen, caudate nuclei, globus palidus, substatia nigra subthalamic nuclei
Where is the basal ganglia located?
Located laterally to thalamus and deep within the cortex. Subthalamic nuclei below thalamus.
Substantia nigra in midbrain but contributes to circuitry of basal nuclei
What is the Putamen and Caudate nucleus collectively known as?
The striatum
Is the basal ganglia another control centre in the brain?
yes,
Circuitry passess through here controlling motor action, executive function and emotional/procedural memory
How does the basal ganglia manage to be closed?
This works through a series of inhibitory and disinhibitary connections;
All circuits take a route through the thalamus, which projects into the appropriate cortex site.
These circuits may mediate our actions depending on experience
What is the Motor, Associative and Limbic loop?
Motor - motor control
Associative - Executive function
Limbic - Procedural Memory
Describe the process of movement, and how motor loop is some ‘go’ signal?
- Neurons in the Globus Pallidus fire at rest and inhibit VL in the thalamus
- Commands for movement come from primary motor cortex and excite putamen neurons, which inhibit Globus pallidus neurons
- These release Thalamic VL neurons from inhibition
- These activate SMA in motor cortex
In monkeys what neurones fire before any activity takes place?
PMA neurons
What doe executive movements consist of?
involve learning new tasks, making decisions based on prior experience, optimise movements
What does procedural memory consist of?
habits e.g. bike riding also known as non-declaritive memory
What is the formation of factual memory created by?
the hippocampus
What happens when structures are removed from the temporal lobe?
profound amnesia, suggests that memories are formed in the temporal lobe but not stored there
what is the hippocampus important for?
formation and storage of declaritive memory, spatial memory and relational memory
where is the hippocampus located?
part of the temporal lobe of the cerebrum, hidden from outside view and extends anteriorly into the brain
Describe the appearance of the hippocampus?
It has a cylindrical/tubular structure that tapers as it extends back into the brain.
Like the verntricles and …this is a curved “C” structure which bends back on itself over the thalamus.
It looks like a seahorse
What is the C shape of the hypothalamus continuous?
is continuous wih a white matter tract know as the fornix – this traverses the thalamus and ends at the hypothalamus
what part of the brain is associated with emotive processing?
Limbic system
What happens to hippocampus during Alzheimers?
Hippocampus degenerates during Alzheimer’s leading to memory loss and unchecked emotive expression.
The hippocampus is linked to the hypothalamus (via fornix), which links to…?
Limbic lobe, more accurately known as the cingulate cortex – which has projections to hippocamus but also to neocrotex involved in sensory processing
What is the hippocampus mainly associated with?
declarative memory - – facts, figures, events
may also be associated with working memory as well
What may be the result of removing temporal lobe?
shows dimished ability to form working memories demonstrating a role for the hippocampus in this.
However, more evidence seems to show that the hippocampus provides context for long-term declarative memory
What is relational memory?
the theory that the brain remembers things and spaces in an interconnected fashion
What happens to people who have lost their temporal lobe to disease?
People who have lost temporal lobe funciton through disease or lobotomy, often have severe antergorade amnesia
Do neurones fire when in a specific place it recognises?
yes, this is known as autobiographical memory
What is the amygdala?
egg shaped portion of grey matters in the medial temporal lobe connected to the fronterior hippocampus
What nuclei is the amygdala split into?
the corticomedial nuclei (middle of the cortex), basolateral nuclei (at the bottom) and the central nucleus
What affect does lesions of the amygdala have in humans?
Have shown an emotional flattening.
Further, people have demonstrated difficultires in identifying the expression of fear in people.
How does amygdala process information?
sensory informaiton is projected into the basolateral
nuclei
Basolateral also ouput to the cerebral cortex where conscience processign of the emotional experience occurs.
The central nucleur receive inputs from…and ouput to the hypothalamus (auonmic response) and brain-stem which can eleicit motor responses
Give a summary of the forebrain?
Thalamus integrates sensory information
Hypothalamus controls bodies homeostasis and drive
Basal ganglia involved in initiating and mediating movement (including habit forming)
Hippocampus associated with declarative (factual) memory
Amygdala appears to process information on fear
