Abstract
People rapidly shift their attention where another person is looking. We recently demonstrated that macaques also shift their attention in the direction of viewed gaze and the similar spatial and temporal dynamics of this gaze-following response in macaques and humans suggests shared neural circuitry (Deaner and Platt, 2003 Current Biology 13: 1609–1613). To assess the flexibility of these mechanisms, we probed whether gaze-following is modulated by social context and whether neuronal activity in area LIP reflects this modulation. Monkeys performed a peripheral target detection task by fixating a central square briefly replaced by an image of a familiar macaque looking left or right (100–800 ms SOA). Upon face offset, a yellow square unpredictably appeared 15 degrees left or right and monkeys were rewarded for shifting gaze to it. High and low social status monkeys served as gaze cues. We predicted gaze-following would be weaker when viewing high-status monkeys because they attracted gaze in a separate target choice task (Deaner and Platt 2004 Journal of Vision Supplement). At 200 ms SOA, reaction times were faster when targets appeared in the direction of viewed gaze. Moreover, gaze-following was suppressed when viewing high-status monkeys. These findings suggest that gaze-following is not reflexive, but can be modulated by social context. We next probed the effects of viewing faces with averted gaze on neuronal activity in macaque area LIP. The preferred direction of each neuron was first mapped using standard delayed saccade trials. We found that neuronal activity in area LIP reflected spatial bias induced by viewing faces with laterally-deviated gaze. Specifically, firing rate was enhanced by viewing low-status monkeys gazing in the preferred direction of each neuron, but was suppressed by viewing high-status monkeys gazing in the same direction. LIP neurons thus encoded spatial bias derived from social cues and context.
Supported by R03-MH-66259 and the Cure Autism Now Foundation (MLP); F32-MH-068128 (ROD)