Source Paper
Temporally Graded Retrograde Amnesia of Contextual Fear after Hippocampal Damage in Rats: Within-Subjects Examination
Stephan G. Anagnostaras, Stephen Maren, Michael S. Fanselow
Journal of Neuroscience • 1999
View Abstract
We have shown previously that electrolytic lesions of the dorsal hippocampus (DH) produce a severe deficit in contextual fear if made 1 d, but not 28 d, after fear conditioning (Kim and Fanselow, 1992). As such, the hippocampus seems to play a time-limited role in the consolidation of contextual fear conditioning. Here, we examine retrograde amnesia of contextual fear produced by DH lesions in a within-subjects design. Unlike our previous reports, rats had both a remote and recent memory at the time of the lesion. Rats were given 10 tone–shock pairings in one context (remote memory) and 10 tone–shock pairings in a distinct context (with a different tone) 50 d later (recent memory), followed by DH or sham lesions 1 d later. Relative to controls, DH-lesioned rats exhibited no deficit in remote contextual fear, but recent contextual fear memory was severely impaired. They also did not exhibit deficits in tone freezing. This highly specific deficit in recent contextual memory demonstrated in a within-subjects design favors mnemonic over performance accounts of hippocampal involvement in fear. These findings also provide further support for a time-limited role of the hippocampus in memory storage.
Freezing Behavior Test
Objective: Measure freezing responses to assess contextual and tone fear memory retention after hippocampal lesions, examining retrograde amnesia in a within-subjects design
Protocol Steps
Remote Memory Fear Conditioning
Rats received tone-shock pairings in one context to establish remote memory
Note: 10 tone-shock pairings administered in first context
View evidence from paper
“Rats were given 10 tone–shock pairings in one context (remote memory)”
Recent Memory Fear Conditioning
Rats received tone-shock pairings in a distinct context with a different tone to establish recent memory
Note: 10 tone-shock pairings in distinct context with different tone
View evidence from paper
“10 tone–shock pairings in a distinct context (with a different tone) 50 d later (recent memory)”
Hippocampal Lesion or Sham Surgery
Dorsal hippocampus electrolytic lesions or sham lesions performed
Note: DH or sham lesions administered; lesion timing is critical
View evidence from paper
“followed by DH or sham lesions 1 d later”
Freezing Behavior Assessment
Measure freezing responses to assess contextual and tone fear memory retention
Note: Freezing measured for both remote and recent contextual memory, and tone freezing
View evidence from paper
“DH-lesioned rats exhibited no deficit in remote contextual fear, but recent contextual fear memory was severely impaired. They also did not exhibit deficits in tone freezing”