Revealing past memories: proactive interference and ketamine-induced memory deficits

Area of Science:

• Neuroscience
• Cognitive Psychology
• Pharmacology

Background:

• Repetitive event memories are prone to interference.
• Proactive interference significantly impacts episodic memory testing.
• Ketamine (NMDA receptor antagonist) is known to cause cognitive deficits.

Purpose of the Study:

• To investigate ketamine's effects on memory acquisition, retrieval, and retention.
• To assess ketamine's role in proactive interference using a radial water maze.
• To understand ketamine's impact on episodic memory encoding and retrieval.

Main Methods:

• Rats were administered ketamine (2.5-100 mg/kg) at different stages of a delayed-match-to-place radial water maze task.
• Memory encoding was tested by administering ketamine before the sample trial.
• Memory retrieval and retention were assessed by administering ketamine before the test trial or after the sample trial, respectively.

Main Results:

• Ketamine (2.5-25 mg/kg) before the sample trial impaired memory encoding, leading to errors in adjacent arms.
• Ketamine (25-100 mg/kg) after the sample trial did not affect memory retention.
• Ketamine before the test trial impaired retrieval, with errors directed towards previous session's goal locations, indicating promoted proactive interference.

Conclusions:

• Ketamine administration promotes proactive interference, disrupting episodic memory retrieval.
• NMDA receptor antagonism by ketamine subtly impairs both memory encoding and retrieval processes.
• These findings illustrate the competition between memory representations and ketamine's disruptive effect on memory recall.