Case report: stimulation of the right amygdala induces transient changes in affective bias

Background: Sensitive outcome measures are needed to quantify the effects of neuromodulation in mood disorders.

Objective: This study examined the utility of a novel affective bias (AB) task in identifying transient mood changes induced by amygdala stimulation in a single rare participant.

Methods: Localized, pulsed electrical stimulation was delivered for 8 min during measures of AB and self-reported mood. Responses were compared with those gathered without stimulation on the same day in the same setting, using paired t-tests.

Results: Stimulation of the basolateral nucleus of the right amygdala at 50 Hz, 15 V, and 200 μs pulse-width produced a significant positive shift in AB (t = -2.864, df = 53, P = .006), despite equivocal findings on self-reported mood (t = -.184, df = 12, P = .857).

Conclusion: Affective bias may be more sensitive to stimulation-induced fluctuations in mood than subjective report, suggesting utility as an outcome measure in neuromodulation studies.