Biology subjects

Brandmeir, N.

Publications and source records attributed to Brandmeir, N..

3 recordsLinked to original sources

bioRxiv2021

A neuronal social trait space for first impressions in the human amygdala and hippocampus

People instantaneously evaluate faces with significant agreement on evaluations of social traits. However, the neural basis for such rapid spontaneous face evaluation remains largely unknown. Here, we recorded from 490 neurons in the amygdala and hippocampus in 5 neurosurgical patients and show that amygdala and hippocampal neurons encode a social trait space. We further investigated the temporal evolution and modulation on the social trait representation, and we employed encoding and decoding models to reveal the critical social traits for the trait space. We also recorded from another 259 neurons and replicated our findings using different social traits. Lastly, the neuronal social trait space may have a behavioral consequence likely involved in the abnormal processing of social information in autism. Together, our results suggest that there exists a neuronal population code for a comprehensive social trait space in the human amygdala and hippocampus that underlie spontaneous first impressions.

neuroscience↗

bioRxiv2020

Encoding of facial features by single neurons in the human amygdala and hippocampus

The human amygdala and hippocampus play a key role in face processing. However, it has been unknown how the neurons in the human amygdala and hippocampus encode facial feature information and directs eye movements to salient facial features such as the eyes and mouth. In this study, we identified a population of neurons that differentiated fixations on the eyes vs. mouth. The response of these feature-selective neurons was not dependent on fixation order, and eye-preferring and mouth-preferring neurons were not of different neuronal types. We found another population of neurons that differentiated saccades to the eyes vs. mouth. Population decoding confirmed our results and further revealed the temporal dynamics of face feature coding. Interestingly, we found that the amygdala and hippocampus played a different role in encoding face features. Lastly, we revealed two functional roles of feature-selective neurons that they encoded the salient region for face recognition and they encoded perceived social trait judgment. Together, we revealed and characterized a new class of neurons that encoded facial features. These neurons may play an important role in social perception and recognition of faces.

neuroscience↗

bioRxiv2020

Feature-based encoding of face identity by single neurons in the human medial temporal lobe

Neurons in the human amygdala and hippocampus that are selective for the identity of specific people are classically thought to encode a persons identity invariant to visual features (e.g., skin tone, eye shape). However, it remains largely unknown how visual information from higher visual cortical areas is translated into such a semantic representation of an individual person. Here, we show that some amygdala and hippocampal neurons are selective to multiple different unrelated face identities based on shared visual features. The encoded identities form clusters in the representation of a deep neural network trained to recognize faces. Contrary to prevailing views, these neurons thus represent an individuals face with a visual feature-based code rather than one based on association with known concepts. Feature neurons encoded faces regardless of their identity, race, gender, familiarity, or pixel-level visual features; and the region of feature space to which feature neurons are tuned predicted their response to new face stimuli. Our results reveal a new class of neurons that bridge the perception-driven representation of facial features in the higher visual cortex with mnemonic semantic representations in the MTL, which may form the basis for declarative memory.

neuroscience↗