Reversible inactivation of amygdala and cerebellum but not perirhinal cortex impairs reactivated fear memories.
The cerebellum, amygdala and perirhinal cortex are involved in fear learning but the different roles that these three structures play in aversive learning are not well defined. Here we show that in adult rats amygdala or cerebellar vermis blockade causes amnesia when performed immediately, but not 1 h, after the recall of fear memories. Thus, the cerebellum, as well as the amygdala, influences long-term fear memories. These effects are long lasting, as they do not recover over time, even after a reminder shock administration. However, all of the subjects were able to form new fear memories in the absence of inactivation. By increasing the strength of conditioning, we observed that stronger fear memories are affected by the combined but not independent amygdala and cerebellar blockade. These results demonstrate that the cerebellum supports the memory processes even in the absence of a crucial site for emotions like the amygdala. Furthermore, they suggest that the amygdala is only one of the neural sites underlying long-term fear memories. Finally, the inactivation of the perirhinal cortex never alters retrieved fear traces, showing important differences between the amygdala, cerebellum and perirhinal cortex in emotional memories.
Sacchetti
Benedetto
B
Rita Levi-Montalcini Center for Brain Repair, Department of Neuroscience, University of Turin, Turin, Italy. benedetto.sacchetti@unito.it
Sacco
Tiziana
T
Strata
Piergiorgio
P
D000647:Amnesia / Q000139:chemically induced / Q000503:physiopathology*; D000679:Amygdala / Q000033:anatomy & histology / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D000841:Anisomycin / Q000009:adverse effects; D001362:Avoidance Learning / Q000187:drug effects / Q000502:physiology; D002531:Cerebellum / Q000033:anatomy & histology / Q000187:drug effects / Q000502:physiology*; D005239:Fear / Q000187:drug effects / Q000502:physiology*; D008297:Male; D008568:Memory / Q000187:drug effects / Q000502:physiology*; D009415:Nerve Net / Q000033:anatomy & histology / Q000187:drug effects / Q000502:physiology; D009419:Nerve Tissue Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D009434:Neural Pathways / Q000033:anatomy & histology / Q000187:drug effects / Q000502:physiology*; D020534:Parahippocampal Gyrus / Q000033:anatomy & histology / Q000187:drug effects / Q000502:physiology; D011500:Protein Synthesis Inhibitors / Q000009:adverse effects; D051381:Rats; D017208:Rats, Wistar; D026941:Sodium Channel Blockers / Q000009:adverse effects; D013779:Tetrodotoxin / Q000009:adverse effects; D013995:Time; D013997:Time Factors
D009419:Nerve Tissue Proteins; D011500:Protein Synthesis Inhibitors; D026941:Sodium Channel Blockers; D013779:Tetrodotoxin; D000841:Anisomycin