Threat, domain-specificity and the human amygdala.

Area of Science:

• Neuroscience
• Cognitive Psychology
• Affective Science

Background:

• The human amygdala is known to respond strongly to negative human faces.
• Limited understanding exists regarding amygdala responses to other animate entities and inanimate objects, and how valence/arousal influence these responses.

Purpose of the Study:

• To investigate amygdala responses to faces, animals, and manipulable objects across different emotional valences and arousal levels.
• To determine if the amygdala differentiates threat responses based on object animacy.

Main Methods:

• Subjects performed a repetition detection task using photographs of faces, animals, and manipulable objects.
• Stimuli were equated for emotional valence and arousal, encompassing negative, neutral, and positive categories.
• fMRI data was analyzed to assess amygdala and cortical activation patterns.

Main Results:

• Both left and right amygdala showed greater activation to animate entities (faces, animals) compared to manipulable objects.
• This effect was pronounced for negative stimuli (fearful faces, threatening animals) and neutral stimuli.
• Weapons did not activate the amygdala but did activate dorsal stream regions associated with object action.

Conclusions:

• The human amygdala automatically responds to threats from animate entities but not inanimate objects like weapons.
• Two distinct circuits may underpin automatic threat detection: an amygdala-based circuit for animate stimuli and a cortex-based circuit for man-made objects.