Fear conditioning following a unilateral anterior temporal lobectomy: reduced autonomic responding and stimulus contingency knowledge.
Animal research demonstrated that during fear conditioning the amygdala plays a central role in forming an association between the conditioned stimulus (CS) and the unconditioned stimulus (US). Lesion studies conducted in patients who underwent a unilateral anterior temporal lobe resection, however; yielded contradictory findings. To date, it remains unclear whether amygdala damage only affects fear-conditioned startle responding or impairs both the latter and fear-conditioned skin conductance responding (SCR). Moreover inconsistency exists regarding the preservation of contingency knowledge in amygdala-damaged patients. In the current study, a differential fear conditioning task was presented to a unilaterally amygdala-damaged patient group and a healthy control group, recording fear-potentiated startle responses along with SCRs. Retrospectively, the valence of the CSs and contingency awareness was assessed. Unlike the control group, unilaterally amygdala-damaged patients showed neither in their SCRs nor in their valence ratings an effect of fear conditioning. The startle data, however, yielded in none of the two test groups fear-conditioned responding. Finally, considerably fewer patients (37.5%) than controls (95%) acquired correct memory of the presented contingency. Based on these findings we concluded that the fear conditioning impairment in amygdala-damaged patients was not restricted to SCRs, but also affected valence ratings and memory of the presented contingency. A broader theory of the amygdala as relevance detector is proposed in order to account for the diverse neurological findings obtained so far.
Department of Psychology, University of Leuven, Belgium. Evelien.Coppens@psy.kuleuven.be
Evelien
E
Coppens
Wim
W
van Paesschen
Mathieu
M
Vandenbulcke
Debora
D
Vansteenwegen
D000704:Analysis of Variance; D038481:Anterior Temporal Lobectomy / Q000009:adverse effects* / Q000379:methods; D001341:Autonomic Nervous System / Q000503:physiopathology*; D001364:Awareness / Q000502:physiology; D003214:Conditioning, Classical / Q000502:physiology*; D004576:Electromyography; D004833:Epilepsy, Temporal Lobe / Q000601:surgery; D005239:Fear; D005260:Female; D007839:Functional Laterality; D005712:Galvanic Skin Response / Q000502:physiology; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D013216:Reflex, Startle / Q000502:physiology