Cedars-Sinai: amygdala category neurons' firing predicts which images humans later remember
Single-neuron recordings in neurosurgical patients show that amygdala activity at first viewing of an image predicts whether it is later remembered; two datasets.
Researchers recording single-neuron activity in the human brain report that the firing of category-selective neurons in the amygdala during the first viewing of an image predicts whether the image will later be remembered, according to a paper on nature.com nature.com
nature.comnature.comOpen source ↗. The work, from a Cedars-Sinai team and published in Nature Neuroscience, used recordings from neurosurgical patients: 42 patients and 49 sessions in the first task. The effect was tested in two separate datasets, which allowed the authors to assess its robustness.
How the experiment was run
Patients performed a working memory task followed by a recognition test. In each of 140 trials they viewed one or three new pictures and, after a maintenance period, said whether a probe picture matched one of them. Each image belonged to one of five categories: people, food, animals, cars and landscapes.
After a delay of 10–30 minutes, patients were shown 400 images: 200 from the earlier task and 200 never shown before. For each image they indicated whether it was "old" or "new" and how sure they were. Neuron activity at encoding was then compared between items later remembered and items later forgotten.
What the amygdala neurons showed
Category-selective amygdala neurons fired more during encoding of later remembered items than of later forgotten ones nature.com
nature.comnature.comOpen source ↗. The effect was predictive of the episodic aspect of the memory and was restricted to each cell's preferred category. It emerged earlier and was stronger in the amygdala than in the hippocampus, and did not depend on stimulus valence or arousal.
Successful memory formation was accompanied by enhanced spike-field coherence between the activity of amygdala category cells and hippocampal field potentials. According to the authors, this indicates that stimulus-specific recruitment of the amygdala, rather than a general change in its activity, predicts memory formation.
The amygdala is classically associated with emotional events. Earlier studies, cited in the paper, found that amygdala stimulation enhances memory for a wide range of neutral stimuli without inducing emotional responses. The authors suggest category cells in the right amygdala as a target for interventions in disorders affecting episodic memory in humans. Ueli Rutishauser said the activity of specific neuron types predicts, while a person sees an image for the first time, whether it will later be remembered.
