Key brain region responds to subjective perception in study of individual neuron activity

When evaluating another person's emotions -- happy, sad, angry, afraid -- humans take cues from facial expressions. Neurons in a part of the brain called the amygdala "fire" in response to the visual stimulation as information is processed by the retina, the amygdala and a network of interconnected brain structures. Some of these regions respond just to the actual features of the face, whereas others respond to how things appear to the viewer, but it is unknown where in the brain this difference arises.
Although the amygdala's importance in face recognition and emotional assessment is well-known, little is understood about how these processes work, but research led by investigators at Cedars-Sinai and the California Institute of Technology has found that at least some of the brain cells that specialize in recognizing emotions may represent judgments based on the viewer's preconceptions rather than the true emotion being expressed.
With colleagues from Huntington Memorial Hospital, using electrodes placed deep in the brain for unrelated diagnostic purposes, investigators recorded electrical activity of individual neurons and found a subset that were "emotion-selective" because their responses distinguished between happy and fearful faces.
Patients were shown pictures of faces whose emotion was difficult to recognize because only parts of the features were clearly visible. Some neurons were more active to faces showing fear, whereas others were more active to happy faces.
"In these instances, the patients correctly judged the expressed emotion," said Ueli Rutishauser, PhD, assistant professor of neurosurgery and director of human neurophysiology research at Cedars-Sinai, senior author of an article published online the week of June 30 in the Early Edition of Proceedings of the National Academy of Sciences.
"But we found that these neurons also responded similarly during incorrect trials, when patients made errors about the actual emotion shown on the faces," Rutishauser added. "When a fear face was incorrectly judged as happy, the neurons responded as if a happy face was correctly judged as happy -- in a sense, "correctly" representing the patient's incorrect judgment. When a happy face was incorrectly judged as a fear face, the neurons responded as if a fear face had been correctly judged as fear -- again, reinforcing the 'correctness' of the incorrect decision. This tells us that the neurons' responses were based on the subjective, perceived judgments that the patients made rather than on the 'ground truth' of the emotion shown in the stimulus."
When the investigators recorded neurons in the hippocampus -- a structure adjacent to the amygdala that also is involved in processing of thoughts, emotions and memories -- they found that the cells responded to the visual stimuli, but those responses did not reflect the patients' subjective judgment.

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"To our knowledge, these findings are novel, in that they show that the response of emotion-sensitive neurons in the amygdala is biased toward the person's subjective judgment of emotions instead of simply responding to the actual features of the stimulus," said Shuo Wang, PhD, a postdoctoral scholar at Caltech and first author of the article. "We've known that the amygdala plays an important role in face and emotion recognition, but these results suggest that it integrates sensory information about faces. It may be that subjective perceptions of facial emotion are formed through repeated cycles of processing between the amygdala, the temporal cortex and other brain structures that shape a person's values and social perspectives."
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zoon wrote:The subjects were deciding whether the person in the picture was afraid, rather than whether they were afraid of the person in the picture; the experiment was about mind reading, otherwise known as Theory of Mind. I think it's interesting because the amygdala is an evolutionarily ancient region that deals with emotions, while ToM is comparatively recent. This result and others support simulation theory, the theory that we mindread other people partly by running our own brain processes offline, and that much of this happens at an automatic level.

DavidMcC wrote:

zoon wrote:The subjects were deciding whether the person in the picture was afraid, rather than whether they were afraid of the person in the picture; the experiment was about mind reading, otherwise known as Theory of Mind. I think it's interesting because the amygdala is an evolutionarily ancient region that deals with emotions, while ToM is comparatively recent. This result and others support simulation theory, the theory that we mindread other people partly by running our own brain processes offline, and that much of this happens at an automatic level.

I'm not quite sure what you mean by "running our own brain processes offline". I assume that the "automatic level" means that it is an unconscious process.

EDIT: Do you mean that there is inhibition of certain neural signals from the amygdala, which would otherwise produce the physiological effects of fear?