Fear processing and social networking in the absence of a functional amygdala.

Background: The human amygdala plays a crucial role in processing social signals, such as face expressions, particularly fearful ones, and facilitates responses to them in face-sensitive cortical regions. This contributes to social competence and individual amygdala size correlates with that of social networks. While rare patients with focal bilateral amygdala lesion typically show impaired recognition of fearful faces, this deficit is variable, and an intriguing possibility is that other brain regions can compensate to support fear and social signal processing.

Reduced 5-HT(2A) receptor signaling following selective bilateral amygdala damage.

Neurobiological evidence implicates the amygdala as well as serotonergic (serotonin, 5-HT) signaling via postsynaptic 5-HT(2A) receptors as essential substrates of anxiety behaviors. Assuming a functional interdependence of these substrates, we hypothesized that a low-fear behavioral phenotype due to bilateral lesion of the amygdala would be associated with significant 5-HT(2A) receptor changes. Thus, we used [(18)F]altanserin positron emission tomography (PET) referenced to radioligand plasma levels and corrected for partial volume effects to quantify the spatial distribution of 5-HT(2A) receptor binding potential (BP(P)) in a rare patient with Urbach-Wiethe disease and selective bilateral amygdala calcification damage relative to 10 healthy control subjects.

Amygdala control of emotion-induced forgetting and remembering: evidence from Urbach-Wiethe disease.

When presented in a neutral context, emotional items interfere with episodic encoding of temporally contiguous non-emotional items, resulting in dissociable valence-dependent retrograde and arousal-dependent anterograde modulatory effects. By studying two rare patients with congenital lipoid proteinosis (Urbach-Wiethe) and a focal disease emphasis on the basolateral amygdala (BLA), we demonstrate that this bidirectional modification of episodic encoding by emotion depends on the integrity of the amygdala, as both retrograde and anterograde modulatory effects are absent. Our findings implicate the amygdala in a neural circuitry that orchestrates rapid retrograde and anterograde regulation of episodic memory access upon criteria of behavioral significance.