Neurons in the human amygdala selective for perceived emotion.
Level 4 - case-series / case-control
Observational single-unit recording study in a clinical series of neurosurgical patients (analogous to case series).
PubMed 24982200 · doi:10.1073/pnas.1323342111
What was done
Depth electrodes recorded activity from over 200 single neurons in the amygdalae of 7 neurosurgical patients. Subjects performed an emotion discrimination task (fear vs. happy) by button press while viewing degraded face stimuli. Firing patterns were analyzed during correct trials to evaluate objective emotion encoding and during incorrect trials to isolate subjective perceptual judgment. Parallel recordings were analyzed in hippocampal neurons, and responses to specific facial features (such as the eye region) were assessed.
What was found
The abstract reports qualitative findings without exact numerical values or effect sizes. Amygdala neurons distinguished fear from happy faces during correct trials and tracked the patients' subjective judgment during incorrect trials. On average, amygdala neuronal responses were modulated most strongly by responses to happy faces and were driven predominantly by judgments regarding the eye region. In contrast, hippocampal neurons encoded the objective stimulus emotion but did not encode subjective judgment.
Why it matters
This study provides direct human single-neuron evidence that amygdala activity reflects subjective, conscious perceptual decisions about facial expressions rather than purely bottom-up visual properties of the stimulus.
Limits
The sample size is very small (7 neurosurgical patients), and findings from patients requiring intracranial depth electrodes may not fully generalize to neurotypical populations. The abstract does not report exact firing rates, sample proportions of responsive units, or quantitative effect sizes.
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