The effect of early visual deprivation on the development of face detection

Early visual experience refines the retinotopic organization within and across visual cortical regions

Early visual areas are retinotopically organized in human and non-human primates. Population receptive field (pRF) size increases with eccentricity and from lower- to higher-level visual areas. Furthermore, the cortical magnification factor (CMF), a measure of how much cortical space is devoted to each degree of visual angle, is typically larger for foveal as opposed to peripheral regions of the visual field. Whether this fine-scale organization within and across visual areas depends on early visual experience has yet been unknown. Here, we employed 7T functional magnetic resonance imaging pRF mapping to assess the retinotopic organization of early visual regions (i.e., V1, V2, and V3) in eight sight recovery individuals with a history of congenital blindness until a maximum of 4 years of age. Compared with sighted controls, foveal pRF sizes in these individuals were larger, and pRF sizes did not show the typical increase with eccentricity and down the visual cortical processing stream (V1-V2-V3). Cortical magnification was overall diminished and decreased less from foveal to parafoveal visual field locations. Furthermore, cortical magnification correlated with visual acuity in sight recovery individuals. The results of this study suggest that early visual experience is essential for refining a presumably innate prototypical retinotopic organization in humans within and across visual areas, which seems to be crucial for acquiring full visual capabilities.

Curiosity constructs communicative competence through social feedback loops

One of the most important challenges for a developing infant is learning how best to allocate their attention and forage for information in the midst of a great deal of novel stimulation. We propose that infants of altricial species solve this challenge by learning selectively from events that are contingent on their immature behavior, such as babbling. Such a contingency filter would focus attention and learning on the behavior of social partners, because social behavior reliably fits infants' sensitivity to contingency. In this way a contingent response by a caregiver to an immature behavior becomes a source of learnable information - feedback - to the infant. Social interactions with responsive caregivers afford infants opportunities to explore the impacts of their immature behavior on their environment, which facilitates the development of socially guided learning. Furthermore, contingent interactions are opportunities to make and test predictions about the efficacy of their social behaviors and those of others. In this chapter, we will use prelinguistic vocal learning to exemplify how infants use their developing vocal abilities to elicit learnable information about language from their social partners. Specifically, we review how caregivers' contingent responses to babbling create information that facilitates infant vocal learning and drives the development of communication. Infants play an active role in this process, as their developing predictions about the consequences of their actions serve to further refine their allocation of attention and drive increases in the maturity of their vocal behavior.

The influence of childhood emotional neglect on emotional face processing in young adults

Childhood emotional neglect (CEN) refers to a failure to meet the basic emotional needs of a child, which can seriously impact interpersonal communication and psychological health in young adults. Emotional face processing is critical in interpersonal communication; however, whether CEN affects this processing in young adults has not been investigated. Therefore, the current study aimed to explore the effects of CEN on emotional face processing in young adults. Using the Child Trauma Questionnaire, an online survey was conducted with 5010 students from four universities in Tianjin, China. After online interviews and diagnosis by professional doctors, we obtained 20 participants with CEN (CEN group) and 20 without CEN (control group). None of the participants had any mental diseases. A 2 × 4 mixed design was used to investigate the differences in accuracy and response time when identifying the valence of the emotional faces. Compared to the control group, the CEN group identified the valence of all emotional faces more slowly, but there was no significant difference between the two groups in terms of accuracy. CEN caused delayed emotional face processing in young adults, which may be related to unresponsive, unavailable, and limited emotional interaction patterns between parents and their children.

Stratifying the autistic phenotype using electrophysiological indices of social perception

Autism spectrum disorder (ASD) is a neurodevelopmental condition characterized by difficulties in social communication, but also great heterogeneity. To offer individualized medicine approaches, we need to better target interventions by stratifying autistic people into subgroups with different biological profiles and/or prognoses. We sought to validate neural responses to faces as a potential stratification factor in ASD by measuring neural (electroencephalography) responses to faces (critical in social interaction) in N = 436 children and adults with and without ASD. The speed of early-stage face processing (N170 latency) was on average slower in ASD than in age-matched controls. In addition, N170 latency was associated with responses to faces in the fusiform gyrus, measured with functional magnetic resonance imaging, and polygenic scores for ASD. Within the ASD group, N170 latency predicted change in adaptive socialization skills over an 18-month follow-up period; data-driven clustering identified a subgroup with slower brain responses and poor social prognosis. Use of a distributional data-driven cutoff was associated with predicted improvements of power in simulated clinical trials targeting social functioning. Together, the data provide converging evidence for the utility of the N170 as a stratification factor to identify biologically and prognostically defined subgroups in ASD.

Top-down modulation of visual cortical processing after transient congenital blindness

Early visual experience has been shown to be critical for the development of visual and multisensory functions; however, its impact on functional brain organization remains largely unexplored. Here, we therefore investigated the effect of early visual deprivation on top-down attentional modulation of visual cortical processing within the occipito-temporal cortex. Furthermore, we explored whether early visual deprivation may affect the extent to which typically visual, motion-selective area hMT responds to moving visual stimuli. Using functional magnetic resonance imaging, we compared cortical responses in area hMT and in the fusiform face area (FFA) to moving face stimuli - which were either task relevant or task irrelevant - relative to stationary face stimuli between cataract-reversal participants and normally sighted controls. Although both groups exhibited significantly stronger visual cortical responses in area hMT to moving stimuli than during the stationary baseline, the magnitude of this effect was significantly lower in the cataract-reversal group. In contrast, both groups exhibited significantly enhanced visual cortical responses in area hMT and in the FFA when moving face stimuli were task relevant compared to when they were task irrelevant, with no significant differences between groups in the magnitude of these effects. These results indicate that top-down attentional modulation of visual cortical processing in area hMT and FFA does not depend on early visual experience. Furthermore, the present results suggest that the functional specialization of area hMT for visual motion processing may be partially disrupted by early visual deprivation.

Three Months-Old' Preferences for Biological Motion Configuration and Its Subsequent Decline

To perceive, identify and understand the action of others, it is essential to perceptually organize individual and local moving body parts (such as limbs) into the whole configuration of a human body in action. Configural processing-processing the relations among features or parts of a stimulus-is a fundamental ability in the perception of several important social stimuli, such as faces or biological motion. Despite this, we know very little about how human infants develop the ability to perceive and prefer configural relations in biological motion. We present two preferential looking experiments (one cross-sectional and one longitudinal) measuring infants' preferential attention between a coherent motion configuration of a person walking vs. a scrambled point-light walker (i.e., a stimulus in which all configural relations were removed, thus, in which the perception of a person is impossible). We found that three-month-old infants prefer a coherent point-light walker in relation to a scrambled display, but both five- and seven-month-old infants do not show any preference. We discuss our findings in terms of the different perceptual, attentional, motor, and brain processes available at each age group, and how they dynamically interact with selective attention toward the coherent and socially relevant motion of a person walking during our first year of life.

Machine Learning Applications in Pediatric Ophthalmology

Purpose: To describe emerging applications of machine learning (ML) in pediatric ophthalmology with an emphasis on the diagnosis and treatment of disorders affecting visual development. Methods: Literature review of studies applying ML algorithms to problems in pediatric ophthalmology. Results: At present, the ML literature emphasizes applications in retinopathy of prematurity. However, there are increasing efforts to apply ML techniques in the diagnosis of amblyogenic conditions such as pediatric cataracts, strabismus, and high refractive error. Conclusions: A greater understanding of the principles governing ML will enable pediatric eye care providers to apply the methodology to unexplored challenges within the subspecialty.

Visual experience dependent plasticity in humans

While sensitive periods in brain development have often been studied by investigating the recovery of visual functions after a congenital phase of visual deprivation in non-human animals, research in humans who had recovered sight after a transient phase of congenital blindness is still scarce. Here, we discuss the hypothesis put forward based on non-human primate work which states that the effects of experience increase downstream the visual processing hierarchy. Recent results from behavioral and neuroscience studies in sight recovery individuals are discussed in the context of research findings from permanently congenitally blind humans as well as from prospective studies in infants and children.

Neural mechanisms of visual sensitive periods in humans

Sensitive periods in brain development are phases of enhanced susceptibility to experience. Here we discuss research from human and non-human neuroscience studies which have demonstrated a) differences in the way infants vs. adults learn; b) how the brain adapts to atypical conditions, in particular a congenital vs. a late onset blindness (sensitive periods for atypical brain development); and c) the extent to which neural systems are capable of acquiring a typical brain organization after sight restoration following a congenital vs. late phase of pattern vision deprivation (sensitive periods for typical brain development). By integrating these three lines of research, we propose neural mechanisms characteristic of sensitive periods vs. adult neuroplasticity and learning.

General and own-species attentional face biases

Humans demonstrate enhanced processing of human faces compared with animal faces, known as own-species bias. This bias is important for identifying people who may cause harm, as well as for recognizing friends and kin. However, growing evidence also indicates a more general face bias. Faces have high evolutionary importance beyond conspecific interactions, as they aid in detecting predators and prey. Few studies have explored the interaction of these biases together. In three experiments, we explored processing of human and animal faces, compared with each other and to nonface objects, which allowed us to examine both own-species and broader face biases. We used a dot-probe paradigm to examine human adults' covert attentional biases for task-irrelevant human faces, animal faces, and objects. We replicated the own-species attentional bias for human faces relative to animal faces. We also found an attentional bias for animal faces relative to objects, consistent with the proposal that faces broadly receive privileged processing. Our findings suggest that humans may be attracted to a broad class of faces. Further, we found that while participants rapidly attended to human faces across all cue display durations, they attended to animal faces only when they had sufficient time to process them. Our findings reveal that the dot-probe paradigm is sensitive for capturing both own-species and more general face biases, and that each has a different attentional signature, possibly reflecting their unique but overlapping evolutionary importance.

Premature birth affects visual body representation and body schema in preterm children

Research has demonstrated that from the first six months of life infants show early sensitivity to body visual features and rely on sensorimotor and proprioceptive inputs in forming representations of their own bodies. Premature birth interferes with typical exposition to visual, sensorimotor and proprioceptive stimulation, thus presumably affecting the development of body representations. Here, we tested this hypothesis by comparing the performance of preterm children with that of age-matched full-termchildren in two tasks assessing, respectively, visual body processing and body schema. We found that preterm children had spared configural processing but altered holistic processing of others' bodies and showed a general difficulty in expressing visuospatial judgements on body stimuli. Furthermore, body-centered visuospatial abilities were associated with specific impairments in operating object-based visuospatial transformations. The findings of this study indicate that preterm birth might interfere with the development of body representations at the levels of body visual perceptual processing and of body schema, with effects even on visuo-spatial abilities for non-bodily stimuli. Body-centered rehabilitative interventions should be proposed to preterm children in order to enhance visuo-spatial abilities and higher-level cognitive functions.

Sensory experience during early sensitive periods shapes cross-modal temporal biases

Typical human perception features stable biases such as perceiving visual events as later than synchronous auditory events. The origin of such perceptual biases is unknown. To investigate the role of early sensory experience, we tested whether a congenital, transient loss of pattern vision, caused by bilateral dense cataracts, has sustained effects on audio-visual and tactile-visual temporal biases and resolution. Participants judged the temporal order of successively presented, spatially separated events within and across modalities. Individuals with reversed congenital cataracts showed a bias towards perceiving visual stimuli as occurring earlier than auditory (Expt. 1) and tactile (Expt. 2) stimuli. This finding stood in stark contrast to normally sighted controls and sight-recovery individuals who had developed cataracts later in childhood: both groups exhibited the typical bias of perceiving vision as delayed compared to audition. These findings provide strong evidence that cross-modal temporal biases depend on sensory experience during an early sensitive period.

New insights into cortical development and plasticity: from molecules to behavior

The human brain contains 100 billion neurons, and each neuron can have up to 200,000 connections to other neurons. Recent advancements in neuroscience-ranging from molecular studies in animal models to behavioral studies in humans-have given us deeper insights into the development of this extraordinarily intricate system. Studies show a complex interaction between biological predispositions and environment; while the gross neuroanatomy and low-level functions develop early prior to receiving environmental inputs, functional selectivity is shaped through experience, governed by the maturation of local excitatory and inhibitory circuits and synaptic plasticity during sensitive periods early in development. Plasticity does not end with the closing of the early sensitive period - the environment continues to play an important role in learning throughout the lifespan. Recent work delineating the cascade of events that initiates, controls and ends sensitive periods, offers new hope of eventually being able to remediate various clinical conditions by selectively reopening plasticity.

The development of human visual cortex and clinical implications

The primary visual cortex (V1) is the first cortical area that processes visual information. Normal development of V1 depends on binocular vision during the critical period, and age-related losses of vision are linked with neurobiological changes in V1. Animal studies have provided important details about the neurobiological mechanisms in V1 that support normal vision or are changed by visual diseases. There is very little information, however, about those neurobiological mechanisms in human V1. That lack of information has hampered the translation of biologically inspired treatments from preclinical models to effective clinical treatments. We have studied human V1 to characterize the expression of neurobiological mechanisms that regulate visual perception and neuroplasticity. We have identified five stages of development for human V1 that start in infancy and continue across the life span. Here, we describe these stages, compare them with visual and anatomical milestones, and discuss implications for translating treatments for visual disorders that depend on neuroplasticity of V1 function.

Plasticity may change inputs as well as processes, structures, and responses

Significant work has documented neuroplasticity in development, demonstrating that developmental pathways are shaped by experience. Plasticity is often discussed in terms of the results of differences in input; differences in brain structures, processes, or responses reflect differences in experience. In this paper, I discuss how developmental plasticity also effectively changes input into the system. That is, structures and processes change in response to input, and those changed structures and processes influence future inputs. For example, plasticity may change the pattern of eye movements to a stimulus, thereby changing which part of the scene becomes the input. Thus, plasticity is not only seen in the structures and processes that result from differences in experience, but also is seen in the changes in the input as those structures and processes adapt. The systematic study of the nature of experience, and how differences in experience shape learning, can contribute to our understanding of neuroplasticity in general.

Electrophysiological evidence of altered visual processing in adults who experienced visual deprivation during infancy

We examined the role of early visual input in visual system development by testing adults who had been born with dense bilateral cataracts that blocked all patterned visual input during infancy until the cataractous lenses were removed surgically and the eyes fitted with compensatory contact lenses. Patients viewed checkerboards and textures to explore early processing regions (V1, V2), Glass patterns to examine global form processing (V4), and moving stimuli to explore global motion processing (V5). Patients' ERPs differed from those of controls in that (1) the V1 component was much smaller for all but the simplest stimuli and (2) extrastriate components did not differentiate amongst texture stimuli, Glass patterns, or motion stimuli. The results indicate that early visual deprivation contributes to permanent abnormalities at early and mid levels of visual processing, consistent with enduring behavioral deficits in the ability to process complex textures, global form, and global motion.

Face Detection and the Development of Own-Species Bias in Infant Macaques

In visually complex environments, numerous items compete for attention. Infants may exhibit attentional efficiency-privileged detection, attention capture, and holding-for face-like stimuli. However, it remains unknown when these biases develop and what role, if any, experience plays in this emerging skill. Here, nursery-reared infant macaques' (Macaca mulatta; n = 10) attention to faces in 10-item arrays of nonfaces was measured using eye tracking. With limited face experience, 3-week-old monkeys were more likely to detect faces and looked longer at faces compared to nonfaces, suggesting a robust face detection system. By 3 months, after peer exposure, infants looked faster to conspecific faces but not heterospecific faces, suggesting an own-species bias in face attention capture, consistent with perceptual attunement.

The Influence of Averageness on Adults' Perceptions of Attractiveness: The Effect of Early Visual Deprivation

Adults who missed early visual input because of congenital cataracts later have deficits in many aspects of face processing. Here we investigated whether they make normal judgments of facial attractiveness. In particular, we studied whether their perceptions are affected normally by a face's proximity to the population mean, as is true of typically developing adults, who find average faces to be more attractive than most other faces. We compared the judgments of facial attractiveness of 12 cataract-reversal patients to norms established from 36 adults with normal vision. Participants viewed pairs of adult male and adult female faces that had been transformed 50% toward and 50% away from their respective group averages, and selected which face was more attractive. Averageness influenced patients' judgments of attractiveness, but to a lesser extent than controls. The results suggest that cataract-reversal patients are able to develop a system for representing faces with a privileged position for an average face, consistent with evidence from identity aftereffects. However, early visual experience is necessary to set up the neural architecture necessary for averageness to influence perceptions of attractiveness with its normal potency.

Reduced adaptability, but no fundamental disruption, of norm-based face coding following early visual deprivation from congenital cataracts

Faces are adaptively coded relative to visual norms that are updated by experience, and this adaptive coding is linked to face recognition ability. Here we investigated whether adaptive coding of faces is disrupted in individuals (adolescents and adults) who experience face recognition difficulties following visual deprivation from congenital cataracts in infancy. We measured adaptive coding using face identity aftereffects, where smaller aftereffects indicate less adaptive updating of face-coding mechanisms by experience. We also examined whether the aftereffects increase with adaptor identity strength, consistent with norm-based coding of identity, as in typical populations, or whether they show a different pattern indicating some more fundamental disruption of face-coding mechanisms. Cataract-reversal patients showed significantly smaller face identity aftereffects than did controls (Experiments 1 and 2). However, their aftereffects increased significantly with adaptor strength, consistent with norm-based coding (Experiment 2). Thus we found reduced adaptability but no fundamental disruption of norm-based face-coding mechanisms in cataract-reversal patients. Our results suggest that early visual experience is important for the normal development of adaptive face-coding mechanisms.

Selectivity of Face Perception to Horizontal Information over Lifespan (from 6 to 74 Year Old)

Face recognition in young human adults preferentially relies on the processing of horizontally-oriented visual information. We addressed whether the horizontal tuning of face perception is modulated by the extensive experience humans acquire with faces over the lifespan, or whether it reflects an invariable processing bias for this visual category. We tested 296 subjects aged from 6 to 74 years in a face matching task. Stimuli were upright and inverted faces filtered to preserve information in the horizontal or vertical orientation, or both (HV) ranges. The reliance on face-specific processing was inferred based on the face inversion effect (FIE). FIE size increased linearly until young adulthood in the horizontal but not the vertical orientation range of face information. These findings indicate that the protracted specialization of the face processing system relies on the extensive experience humans acquire at encoding the horizontal information conveyed by upright faces.

Evolutionary Psychology as a Metatheory for the Social Sciences: How to Gather Interdisciplinary Evidence for a Psychological Adaptation

Evolutionary psychology has been proposed as a new metatheory for the social sciences ( Buss, 1995 ). Evolutionary psychology is an approach that emphasizes the evolutionary background of psychological phenomena (e.g., cognition, motivation, perception), with the expectation that knowledge about this background enhances our understanding of the working of the present human mind. This proposal has met with both enthusiasm and criticism. An important criticism is that it is hard, if possible at all, to find empirical evidence for a hypothesized psychological adaptation. This criticism has been addressed with the proposal to build a nomological network of evidence around a hypothesized psychological adaptation ( Schmitt & Pilcher, 2004 ). In this article, we show that it is possible to use this nomological network of evidence to support the hypothesis that face recognition is an adaptation. We reviewed the literature on face recognition from different disciplines (psychology, medicine, neuroscience, genetics, primatology, and anthropology) and conclude that there is an extensive network of evidence for the proposed hypothesis. We argue that building a nomological network of evidence is a promising way to address several criticisms of evolutionary psychology, and that such a network can serve as a metatheoretical framework for the social sciences.

Efficient human face detection in infancy

Adults detect conspecific faces more efficiently than heterospecific faces; however, the development of this own-species bias (OSB) remains unexplored. We tested whether 6- and 11-month-olds exhibit OSB in their attention to human and animal faces in complex visual displays with high perceptual load (25 images competing for attention). Infants (n = 48) and adults (n = 43) passively viewed arrays containing a face among 24 non-face distractors while we measured their gaze with remote eye tracking. While OSB is typically not observed until about 9 months, we found that, already by 6 months, human faces were more likely to be detected, were detected more quickly (attention capture), and received longer looks (attention holding) than animal faces. These data suggest that 6-month-olds already exhibit OSB in face detection efficiency, consistent with perceptual attunement. This specialization may reflect the biological importance of detecting conspecific faces, a foundational ability for early social interactions.

Face processing among twins with and without autism: social correlates and twin concordance

Autism spectrum disorder (ASD) has a strong heritable basis, as evidenced by twin concordance rates. Within ASD, symptom domains may arise via independent genetic contributions, with varying heritabilities and genetic mechanisms. In this article, we explore social functioning in the form of (i) electrophysiological and behavioral measures of face processing (P1 and N170) and (ii) social behavior among child and adolescent twins with (N = 52) and without ASD (N = 66). Twins without ASD had better holistic face processing and face memory, faster P1 responses and greater sensitivity to the effects of facial inversion on P1. In contrast, N170 responses to faces were similar across diagnosis, with more negative amplitudes for faces vs non-face images. Across the sample, stronger social skills and fewer social difficulties were associated with faster P1 and N170 responses to upright faces, and better face memory. Twins were highly correlated within pairs across most measures, but correlations were significantly stronger for monozygotic vs dizygotic pairs on N170 latency and social problems. We suggest common developmental influences across twins for face processing and social behavior, but highlight (i) neural speed of face processing and (ii) social difficulties as important avenues in the search for genetic underpinnings in ASD.

Task-irrelevant emotion facilitates face discrimination learning

We understand poorly how the ability to discriminate faces from one another is shaped by visual experience. The purpose of the present study is to determine whether face discrimination learning can be facilitated by facial emotions. To answer this question, we used a task-irrelevant perceptual learning paradigm because it closely mimics the learning processes that, in daily life, occur without a conscious intention to learn and without an attentional focus on specific facial features. We measured face discrimination thresholds before and after training. During the training phase (4 days), participants performed a contrast discrimination task on face images. They were not informed that we introduced (task-irrelevant) subtle variations in the face images from trial to trial. For the Identity group, the task-irrelevant features were variations along a morphing continuum of facial identity. For the Emotion group, the task-irrelevant features were variations along an emotional expression morphing continuum. The Control group did not undergo contrast discrimination learning and only performed the pre-training and post-training tests, with the same temporal gap between them as the other two groups. Results indicate that face discrimination improved, but only for the Emotion group. Participants in the Emotion group, moreover, showed face discrimination improvements also for stimulus variations along the facial identity dimension, even if these (task-irrelevant) stimulus features had not been presented during training. The present results highlight the importance of emotions for face discrimination learning.

Global processing in amblyopia: a review

Amblyopia is a neurodevelopmental disorder of the visual system that is associated with disrupted binocular vision during early childhood. There is evidence that the effects of amblyopia extend beyond the primary visual cortex to regions of the dorsal and ventral extra-striate visual cortex involved in visual integration. Here, we review the current literature on global processing deficits in observers with either strabismic, anisometropic, or deprivation amblyopia. A range of global processing tasks have been used to investigate the extent of the cortical deficit in amblyopia including: global motion perception, global form perception, face perception, and biological motion. These tasks appear to be differentially affected by amblyopia. In general, observers with unilateral amblyopia appear to show deficits for local spatial processing and global tasks that require the segregation of signal from noise. In bilateral cases, the global processing deficits are exaggerated, and appear to extend to specialized perceptual systems such as those involved in face processing.

Early visual deprivation from congenital cataracts disrupts activity and functional connectivity in the face network

The development of the face-processing network has been examined with functional neuroimaging, but the effect of visual deprivation early in life on this network is not known. We examined this question in a group of young adults who had been born with dense, central cataracts in both eyes that blocked all visual input to the retina until the cataracts were removed during infancy. We used functional magnetic resonance imaging to examine regions in the "core" and "extended" face networks as participants viewed faces and other objects, and performed a face discrimination task. This task required matching faces on the basis of facial features or on the spacing between the facial features. The Cataract group (a) had reduced discrimination performance on the Spacing task relative to Controls; (b) used the same brain regions as Controls when passively viewing faces or making judgments about faces, but showed reduced activation during passive viewing of faces, especially in extended face-network regions; and (c) unlike Controls, showed activation in face-network regions for objects. In addition, the functional connections of the fusiform gyri with the rest of the face network were altered, and these brain changes were related to Cataract participants' performance on the face discrimination task. These results provide evidence that early visual input is necessary to set up or preserve activity and functional connectivity in the face-processing network that will later mediate expert face processing.

Impact of total sleep deprivation on behavioural neural processing of emotionally expressive faces

Sleep deprivation impacts subjective mood states, but very little research has examined the impact on processing emotional information. In the current study, we investigated the impact of total sleep deprivation on neural responses to emotional facial expressions as well as the accuracy and speed with which these faces were categorized. Forty-nine participants completed two tasks in which they were asked to categorize emotional facial expressions as Happy, Sad, Angry, or Fearful. They were shown the 'full' expression of the emotions in one task and more subtle expressions in a second task in which expressions were 'morphed' with neutral faces so that the intensity of emotion varied. It was expected that sleep deprivation would lead to greater reactivity (indexed by larger amplitude N170 event-related potentials), particularly for negative and more subtle facial expressions. In the full face task, sleep-deprived (SD) participants were significantly less accurate than controls (C) at identifying Sad faces and slower to identify all emotional expressions. P1 was smaller and N170 was larger for the SD compared to C group, but for all emotions, indicating generalized impairment in low-level visual processing. In the more difficult morphed face task, SD participants were less accurate than C participants for Sad faces; as well, the group difference in reaction time was greatest for Sad faces. For the SD group, N170 increased in amplitude with increasing perceptual difficulty for the Fearful and Angry faces, but decreased in amplitude with increasing difficulty for Sad faces. These data illustrate that sleep deprivation led to greater neural reactivity for the threat-related negative emotions as they became more subtle; however, there was a failure to engage these perceptual resources for the processing of Sad faces. Sleep loss preferentially impacted the processing of Sad faces; this has widespread implications for sleep-deprived groups.