Chp 10. Memory Formation: Early Stages

Question 1

Explain the formation of a memory trace beginning with a behavioural experience

Answer 1

behavioural experience activates a set of weakly connected neurons, which activate the cellular-molecular processes in those neurons which strengthen their synaptic connection, this creates a neural representation known as a memory trace.

Question 2

Richard Morris thoughts

Answer 2

first to test that initial formation of memory depends on activation of NMDA receptors. thought this because NMDA is critical for strengthening synapses so probably important for initiation of memories for behavioural experiences

Question 3

Richard Morris Experiment (groups)

Answer 3

Groups: 1. control = with vehicle 2. treatment = implanted cannula with APV (NMDA antagonist) into the ventricular system which would enter the CSF. APV would block glutamate from binding to NMDA receptors and impair formation of memories at the time of learning

Question 4

Richard Morris Experiment (method)

Answer 4

Performed the place learning version of the water task. (the platform becomes invisible)

Question 5

Richard Morris Experiment (Results)

Answer 5

APV prevented LTP induction in dentate gyrus of the hippocampus

impaired rats ability to learn hidden platform location

did not even display a quadrant preference

Question 6

What were the two approaches used to test the hypothesis that NMDA are important for memory formation

Answer 6

1. pharmacological alteration (richard morris)
2. genetic engineering

Question 7

What popular view caused a pushback of the thoughts of the importance of NMDAR

Answer 7

that NMDAR plasticity processes are crucial for encoding but not the expression of memory

Question 8

What did Saucier and Cain believe about the water task that Richard performed

Answer 8

that the impairments seen were due to the secondary effects of the NMDA blockage on sensory and motor processes

Question 9

Saucier and Cain Experiment (method and results)

Answer 9

pre-trained rats (let then swim in the maze with no platform), then inject NMDA antagonist (APV) and they showed no impairments

Question 10

What new experiment was created because intrigued by NMDAR function (hypothesis)

Answer 10

NMDAR activation in hippocampus is not necessary for the initial acquisition of place learning in the water task, but is needed for the post-training consolidation processes in hippocampus
(dont need it to learn where it is, but need it to remember)

Question 11

New experiment (groups)

Answer 11

3 groups
CPP (NMDA antagonist) in either peripheral or intra-hippocampal (more difficult) injections or vehicle
these were administered during different times of training for the water task
(peripheral injections of CPP were before new location training)

Question 12

New experiment (design)

Answer 12

Rapid Acquisition Task
3 Phases:
1. initial location = 4 days, 8 trails per day
2. new location = 1 day, 16 trials in 2 hours
3. competition test = will rats go to new or initial location (there was no actual platform in the pool)

Question 13

Results of New experiment (results)

Question 14

Results of new experiment (conclusion)

Answer 14

shutting down plasticity in the hippocampus during or after acquisition of new location impairs memory consolidation. There is no effect on previously acquired locations before training.

Question 15

Dorsal vs. Ventral HPC in NMDA function in the new experiment

Answer 15

experiment was limited to dorsal HPC

possible NMDA receptor function in ventral HPC supports new location learning