Single-Cell Responses to Face Adaptation in the Human Medial Temporal Lobe

Alexander Kraskov,Itzhak Fried,Florian Mormann,Christof Koch,Rodrigo Quian Quiroga

doi:10.1016/j.neuron.2014.09.006

Abstract

SummaryWe used a face adaptation paradigm to bias the perception of ambiguous images of faces and study how single neurons in the human medial temporal lobe (MTL) respond to the same images eliciting different percepts. The ambiguous images were morphs between the faces of two familiar individuals, chosen because at least one MTL neuron responded selectively to one but not to the other face. We found that the firing of MTL neurons closely followed the subjects’ perceptual decisions—i.e., recognizing one person or the other. In most cases, the response to the ambiguous images was similar to the one obtained when showing the pictures without morphing. Altogether, these results show that many neurons in the medial temporal lobe signal the subjects’ perceptual decisions rather than the visual features of the stimulus.

Highlights

A key function of the brain is to extract meaning from relatively limited, noisy, and ambiguous sensory information
We used a face adaptation paradigm to bias the perception of ambiguous images of faces and study how single neurons in the human medial temporal lobe (MTL) respond to the same images eliciting different percepts
We found that the firing of MTL neurons closely followed the subjects’ perceptual decisions—i.e., recognizing one person or the other

Summary

Introduction

A key function of the brain is to extract meaning from relatively limited, noisy, and ambiguous sensory information. At the top of the hierarchy along the ventral visual pathway, high-level visual areas have strong connections to the medial temporal lobe (MTL) (Saleem and Tanaka, 1996; Suzuki, 1996; Lavenex and Amaral, 2000), which has been consistently shown to be involved in semantic memory (Squire and Zola-Morgan, 1991; Nadel and Moscovitch, 1997; Squire et al, 2004) It is precisely in this area where we previously reported the presence of ‘‘concept cells’’—i.e., neurons with highly selective and invariant responses that represent the meaning of the stimulus. Concept cells are selectively activated by different pictures of a particular person, by the person’s written or spoken name, and even by internal recall, in the absence of any external stimulus (Quian Quiroga et al, 2005, 2008a, 2009; Gelbard-Sagiv et al, 2008; Quian Quiroga, 2012)

Results

Discussion

Conclusion