letters to nature : fear inhibition (CI: 20-s light). An electric shock was the uncon- ditioned stimulus (US). In the first phase of training, five CS-US pairings were presented with a variable intertrial interval (60-180 s) on each of two consecutive days. Following this fear-conditioning phase. animals were divided into two groups (CI-CS paired and

doi:10.4324/9780203825266-84

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ABSTRACT

Rgura 1 ConditioneO inhiblOOn: electrophysiology and benaviour. I, ElectrOde placements in the prefrontal cortex (grey area) Cg1: cingulate area 1: Prl and MO: prefrontal and medial """tal cortices, resoectiVely". b. d. Representative changes in activity before (Pre , and 21 and during Cl-CS presentation. c. Top. mean unit activity ratIOS. CS presentatlOfl caused a greater oecrease in prefrontal actIVity in unpaJrec;i animals than in paired animals (Flo 10 = 5.9: P < 0.051. Bottom. mean percentage freezing. Unpaired miCe displayed mOfe treezing than paired mice (Fl. 10 = 7.n: P < 0.02) .• , Rela_iIl between behavioural and electropllysiological data from aJI12 animals (r = 0.73: P = 0.0(63).