The impact of stimulus size and orientation on individual face coding in monkey face-selective cortex

Abstract

Face-selective neurons in the monkey temporal cortex discharge at different rates in response to pictures of different individual faces. Here we tested whether this pattern of response across single neurons in the face-selective area ML (located in the middle Superior Temporal Sulcus) tolerates two affine transformations; picture-plane inversion, known to decrease the average response of face-selective neurons and the other, stimulus size. We recorded the response of 57 ML neurons in two awake and fixating monkeys. Face stimuli were presented at two sizes (10 and 5 degrees of visual angle) and two orientations (upright and inverted). Different faces elicited distinct patterns of activity across ML neurons that were reliable (i.e., predictable with a classifier) within a specific size and orientation condition. Despite observing a reduction in the average response magnitude of face-selective neurons to inverted faces, compared to upright faces, classifier performance was above chance for both upright and inverted faces. While decoding was largely preserved across changes in stimulus size, a classifier trained with one orientation condition and tested on the other did not lead to performance above chance level. We conclude that different individual faces can be decoded from patterns of responses in the monkey area ML regardless of orientation or size, but with qualitatively different patterns of responses for upright and inverted faces.

Face pareidolia in male schizophrenia

“…Recent studies in non-human primates show that among brain regions responsive to face-like images, the amygdala plays a decisive role 112 . Moreover, preference for both real faces and face-like non-faces is eliminated in a monkey with bilateral amygdala lesions 100 . This underscores an interaction between visual processing of a socially significant face pattern and its affective value.…”

“…This method is believed to disentangle perceptual mechanisms from higher-order influences such as cognitive biases 79 . It is assumed that a hard-wired subcortical face detection machinery prioritizes early face detection even at potential costs of false positives 65 , 100 , and in such a way provides privileged access for face-like images to visual awareness. From this perspective, as SZ and TD individuals are rather similar at earlier stages of encoding face-like images under b-CFS conditions 79 , differences in face pareidolia between them may be considered of the cognitive rather than perceptual origin.…”

Parallel Processing of Facial Expression and Head Orientation in the Macaque Brain

“…6a). This finding can be interpreted as evidence that area PL is activated by the complex features of a face (Issa and DiCarlo, 2012), and that this activation is invariant to the image distortions imposed by changes in retinal size and lighting conditions (Taubert et al, 2018a). However, while tolerant of changes in lowlevel properties that do not change the interpretation of the facial signals from a social perspective, the data also suggest that area PL is sensitive to high-level changes in facial structure.…”

Social cognition in individuals born preterm

“…Furthermore, a kind of predisposition for a coarse face schema (such as two eyes above a mouth) is believed to occur already very early in lifespan 77 : foetuses in the third trimester of pregnancy 78 , human infants 79 – 82 , and children aged 5–6 years 83 are reported to demonstrate a visual preference for face-like stimuli over similar images. Furthermore, even newly hatched domestic chicks ( Gallus gallus ) exhibit preference to a coarse face schema 84 – 86 , while non-human primates such as the rhesus monkey are likely to share face-detection machinery with humans 87 – 89 . Yet it is reported that only 7- and 8-month-old human infants (but not infants aged 5-6 months) exhibit visual preference to Archimboldo portraits over the same images presented upside-down 90 that implies a period of development of the sensitivity to faces in such images.…”

“…The periventricular area of the brain contains many interconnecting fibres, damage to which may lead to brain disintegration eliciting a number of deficits in visual perception and social cognition. Converging evidence from neuroimaging, neuropsychological and electrophysiological studies indicate that the subcortical face route, such as colliculo-pulvino-amygdalar pathway 91 , provides a neural substrate for the cortical social brain network 87 , 89 , 92 , 93 . Alterations of this pathway along with subcortical-cortical and cortico-cortical connectivity caused by PVL might be decisive for alterations in face processing and social cognition in PB individuals.…”