Goshen - Feb 4,6

Question 1

What are the two major viewpoints on to be addressed in this study regarding the consolidation of remote memories?

What evidence is used by both positions to support
their viewpoint?

Answer 1

Two major view points:

1. hippocampus is not part of memory consolidation
   - (ev) hippocampal lesions impair RECENT memory, but have no effect on REMOTE
   - (ev) graded amnesia
2. hippocampus continues to be a part of memory consolidation
   - multiple trace theory: hippocampal memory trace isn’t replaced with a cortical one, but they actually interplay with each other
   - (ev) nongraded amnesia & nongraded retrograde amnesia

Question 2

Discuss the findings depicted in Figure 3 by describing the purpose of each of the experimental groups in subgraphs 3a through 3f.

How many separate ways was the
optogenetic [inhibition] approach used to reveal MAJOR weaknesses of previous lesion or pharmacological approaches to understand how and where long term memories are stored?

Answer 2

Figure 3 Findings
A. (part1) ca1 inhibition during recall blocked remote fear memory - low % freezing (aka not showing fear) – (part2) interference was reversible…fear memory was fully expressed the next day
B. inhibited mice demonstrated remote fear recall with illumination - fear expression mechanisms remained intact (as opposed to not there at all??)
C/D. looking at whether the hippocampus would be involved in contextual fear recall as long as a memory trace could be detected - ca1 inhibition during recall blocked remote fear memory even after long intervals
==== these results point to on going involvement of the hippocampus in remote contextual fear memories (default activator) ========
E/F

Optogenetic inhibition approach

• enables cell type precision
• enables temporal control