Behavioural and neurophysiological evidence for face identity and face emotion processing in animals

Abstract

Visual cues from faces provide important social information relating to individual identity, sexual attraction and emotional state. Behavioural and neurophysiological studies on both monkeys and sheep have shown that specialized skills and neural systems for processing these complex cues to guide behaviour have evolved in a number of mammals and are not present exclusively in humans. Indeed, there are remarkable similarities in the ways that faces are processed by the brain in humans and other mammalian species. While human studies with brain imaging and gross neurophysiological recording approaches have revealed global aspects of the face-processing network, they cannot investigate how information is encoded by specific neural networks. Single neuron electrophysiological recording approaches in both monkeys and sheep have, however, provided some insights into the neural encoding principles involved and, particularly, the presence of a remarkable degree of high-level encoding even at the level of a specific face. Recent developments that allow simultaneous recordings to be made from many hundreds of individual neurons are also beginning to reveal evidence for global aspects of a population-based code. This review will summarize what we have learned so far from these animalbased studies about the way the mammalian brain processes the faces and the emotions they can communicate, as well as associated capacities such as how identity and emotion cues are dissociated and how face imagery might be generated. It will also try to highlight what questions and advances in knowledge still challenge us in order to provide a complete understanding of just how brain networks perform this complex and important social recognition task.

In search of the chemical basis for MHC odourtypes

“…Consider a parallel evolved system for communicating individual identity: visual face recognition. There is now considerable evidence that humans, other primates and even sheep are able to recognize individuals by distinctive visual characteristics of their faces (reviewed in Calder & Young 2005;Tate et al 2006;McKone et al 2007). This ability seems to reside in some sort of holistic processing of relational visual information.…”

Brain imaging reveals neuronal circuitry underlying the crow’s perception of human faces

“…This network of brain regions that perceive and analyze faces is informed by ventral and dorsal visual pathways-the ventral enabling fine discrimination and the dorsal providing rapid, but coarse, emotional assessment (3). Brain mapping investigations on other species capable of human recognition are extremely limited; however, electrophysiological recordings in the visual cortex of domestic sheep and nonhuman primates have indicated the presence of neurons that respond to human facial information (5).…”

Should Damage to the Machinery of Social Perception Damage Perception?

“…Sheep are social animals that readily recognize faces and interpret facial expressions of their conspecifics, even when the faces presented on a computer monitor. Single-unit electrophysiological recordings have revealed that neurons in the sheep temporal cortex exhibit selectivity for faces that bears a striking similarity to that observed in monkeys and humans (Tate, Fischer, Leigh, & Kendrick, 2006). While this observation does not imply that sheep possess a human-like potential for mind reading, it does at least raise the question whether the sheep homologs of the human STS and TPJ might be involved in some form of social monitoring.…”