What happens in the central nervous system? Because the lifespan of most neurons in the brain approaches that of the organism ( 3), it is conceivable that the population of face-selective cells that fire today when you see your mother, for instance, is identical to the population that fired under the same circumstances 10 years ago. In addition to the continuous replacement of individual cells, the protein constituents of cells likewise undergo nearly continuous turnover ( 2). A cup of coffee, for instance, tastes the same today as it did one year ago, despite the fact that the receptors in our taste buds are replaced every two weeks ( 1). The consistent behavior that is evident at the global level of the organism can persist despite continuous change in the system’s component parts. Many biological systems perform in a stable manner over time. We propose that neurons in the AF face patch are specialized for aspects of face perception that demand stability as opposed to plasticity. Longitudinal tracking over a series of daily recording sessions revealed that face-selective neurons maintain consistent visual response profiles across months-long time spans despite the influence of ongoing daily experience. Using chronically implanted microwire electrodes guided by functional MRI targeting, we obtained distinct profiles of selectivity for face and nonface stimuli that served as fingerprints for individual neurons in the anterior fundus (AF) face patch within the superior temporal sulcus. Here we show that the macaque inferotemporal cortex contains face-selective cells that show virtually no change in their patterns of visual responses over time periods as long as one year.
It therefore remains unclear how neuronal properties observed on a given day predict that same neuron's activity months or years later. The functional properties of neurons in behaving animals are typically assessed over time periods ranging from minutes to hours, which amounts to a snapshot compared to a lifespan of a neuron.
Because primates are frequently called upon to recognize and remember new individuals, the neuronal representation of faces in the brain might be expected to change over time. Face perception in both humans and monkeys is thought to depend on neurons clustered in discrete, specialized brain regions.
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