Inactivation of face selective neurons alters eye movements when free viewing faces

Abstract

During free viewing, faces attract gaze and induce specific fixation patterns corresponding to the facial features. This suggests that neurons encoding the facial features are in the causal chain that steers the eyes. However, there is no physiological evidence to support a mechanistic link between face encoding neurons in high-level visual areas and the oculomotor system. In this study, we targeted the middle face patches of inferior temporal (IT) cortex in two macaque monkeys using an fMRI localizer. We then utilized muscimol microinjection to unilaterally suppress IT neural activity inside and outside the face patches and recorded eye movements while the animals free viewing natural scenes. Inactivation of the face selective neurons altered the pattern of eye movements on faces: the monkeys found faces in the scene but neglected the eye ipsilateral to the inactivation hemisphere. These findings reveal the causal contribution of the high-level visual cortex in eye movements.

When the whole is only the parts: non-holistic object parts predominate face-cell responses to illusory faces

“…Moreover, we found that the pareidolia selectivity could be mostly explained (80%) by the pareidolic eye features alone. While the significance of eyes for face cells have previously been demonstrated (Azadi et al, 2023;Freiwald et al, 2009;Issa & DiCarlo, 2012;Waidmann et al, 2022), an important distinction to be made here is that real eyes are still recognizable as eyes, even without the context of a real face. On the other hand, when viewed in isolation, we argue that a pareidolic eye feature (e.g., an egg yolk in a frying pan) does not resemble an eye more so than it resembles the actual object part (i.e., an egg yolk).…”

“…First, while humans clearly perceive illusory faces in pareidolia images, even assigning age, gender, and emotion to these nonface objects(Wardle et al, 2020, 2022), it is unclear whether monkeys even perceive illusory faces. Eye-tracking experiments show that free-viewing monkeys look preferentially at pareidolia images, and their fixation patterns for pareidolia images were correlated with their viewing patterns for faces (Azadi et al, 2023; Taubert et al, 2017). However, the monkeys also fixated small round object parts regardless of the presence of an illusory face.…”

“…Face cells respond more to faces than to non-face objects (Bruce et al, 1981; Gross et al, 1972; Tsao et al, 2006) and have been causally implicated in the perception of faces (A. Afraz et al, 2015; S.-R. Afraz et al, 2006; Azadi et al, 2023; Moeller et al, 2017; Sadagopan et al, 2017). Several studies have suggested hallmark properties of configural or holistic face processing in the responses of individual face cells.…”

Individual gaze shapes diverging neural representations

“…This resonates with the foveal bias of face-and text-preferring neural populations in IT 1,22,23 and strongly suggests that individual gaze shapes individual visual worlds 3 . Individual gaze in turn is shaped by genes 24,25 and experience 20 linked to categorical preferences in the ventral stream 26,27 . Individual gaze may further be tuned to idiosyncratic characteristics of the visual system 28,29 .…”