Chapter 6
Hippocampus and Spatial Memory
Huangui Xiong
QUESTIONS
1.
Where is hippocampus located in human brain?
2.
What are the three subfields in the hippocampus?
3.
What are the principal cells in the dentate gyrus and CA1 field?
4.
CA1 region belongs to which subfield in hippocampus?
5.
The main input to the dentate gyrus originates from which part of brain and via which fiber path?
6.
The medial and lateral perforant paths project to which part of the dendrite tuft of the granule cells?
7.
Mossy fibers originate from which part of the hippocampus and synapse onto the neurons of which
field(s)?
8. How many groups of dendrites do a CA1 neuron have and the name for each group? From which part of a
CA1 neuron does the axon originate?
9. What is the main afferent pathway to the CA1 pyramidal cells and from where does this pathway
originate?
10. Briefly describe information flow through the hippocampus
11. Damage to the hippocampus disrupts which type of memory?
12. What are the three basic properties of LTP? Define each of the three basic properties.
13. What is the key role of NMDA receptors play in LTP induction and what are two simultaneously
occurring events needed for LTP induction?
6.
Hippocampus and Spatial Memory
Huangui Xiong
2
ANSWERS
1.
Where is hippocampus located in human brain?
The hippocampus is located inside the medial temporal lobe on both sides of the human brain.
2.
What are the three subfields in the hippocampus?
The dentate gyrus, hippocampal proper and subiculum.
3.
What are the principal cells in the dentate gyrus and CA1 field?
The principal cells in the dentate gyrus are granule cells and the principal cells in the CA field are pyramidal
cells.
4.
CA1 region belongs to which subfield in hippocampus?
Hippocampal proper
5.
The main input to the dentate gyrus originates from which part of brain and via which fiber path?
The main input to the dentate gyrus is from the entorhinal cortex by way of a fiber system called the perforant
path.
6.
The medial and lateral perforant paths project to which part of the dendrite tuft of the granule cells?
The perforant path is divided in the medial perforant path and the lateral perforant path. The medial perforant
path synapses onto the proximal dendritic area of the granule cells, while the lateral perforant path does it onto
the distal dendrites of these same cells.
7.
Mossy fibers originate from which part of the hippocampus and synapse onto the neurons of which
field(s)?
Mossy fibers originate from granule cells in the dentate gyrus and synapse onto the neurons in the CA3 field.
8.
How many groups of dendrites do a CA1 neuron have and the name for each group? From which part of
a CA1 neuron does the axon originate
A CA1 neuron has two groups of dendrites, the apical dendrite and the basal dendrites. The axon originates
from the proximal segment of basal dendrite.
9.
What is the main afferent pathway to the CA1 pyramidal cells and from where does this pathway
originate?
The main afferent pathway to the CA1 pyramidal cells is Schaffer collateral/commissural pathway. The
Schaffer collateral path consists of axons from the CA3 neurons in ipsilateral hippocampus and the commissural
path is composed of fibers from the CA3 neurons in the contralateral hippocampus.
10. Briefly describe information flow through the hippocampus
Information flow through the hippocampus proceeds from dentate gyrus to CA3 to CA1 to the subiculum,
forming the principal trisynaptic circuit.
11. Damage to the hippocampus disrupts which type of memory?
Damage to the hippocampus disrupts declarative memory processes and more specifically episodic memory
functions.
12. What are the three basic properties of LTP? Define each of the three basic properties.
Three basic properties of LTP are co-operativity, associativity and input-specificity. Co-operativity refers to the
fact that long-lasting synaptic enhancement following HFS increases with the number of stimulated afferents.
Associativity means that a weak input (small number of stimulated afferents) can be potentiated if it is active at
the same time as a strong tetanus (large number of stimulated afferents) to a separate but convergent input.
Input-specificity refers to a phenomenon that the increase in synaptic strength usually does not occur in other
synapses (on the same cell) that are not active at the time of repetitive stimulation.
6.
Hippocampus and Spatial Memory
Huangui Xiong
3
13. What is the key role of NMDA receptors play in LTP induction and what are two simultaneously
occurring events needed for LTP induction?
The key role that the NMDA receptors play in LTP induction relies on the voltage-dependent block of its
channel by Mg2+. The two simultaneously occurring events needed for LTP induction are cell membrane
depolarization and L-glutamate binds to NMDA receptor.