Functional inactivation of the amygdala before but not after auditory fearconditioning prevents memory formation

Two competing theories predict different effects on memory consolidation wh en the amygdala is inactivated after fear conditioning. One theory, based o n studies using inhibitory avoidance training, proposes that the amygdala m odulates the strength of fear learning, and post-training amygdala manipula tions interfere with memory consolidation. The other, based on studies usin g Pavlovian fear conditioning, hypothesizes that fear learning occurs in th e amygdala, and post-training manipulations after acquisition will not affe ct memory consolidation. We infused the GABA(A) agonist muscimol (4.4 nmol/ side) or vehicle into lateral and basal amygdala (LBA) of rats either befor e or immediately after tone-foot shock Pavlovian fear conditioning. Pre-tra ining infusions eliminated acquisition, whereas post-training infusions had no effect. These findings indicate that synaptic activity in LBA is necess ary during learning, but that amygdala inactivation directly after training does not affect memory consolidation. Results suggest that essential aspec ts of plasticity underlying auditory fear conditioning take place within LB A during learning.