Face Recognition: Babies get it right
- University of Massachusetts Amherst, United States
Human faces are an important part of social interactions. We use them to recognize a friend, to gauge someone's mood, or to figure out where to direct our attention. But before engaging in any of these activities, we must first identify a face as a face.
The fundamental question of how a perceptual system, such as the one underlying face recognition, becomes organized in the brain is important for understanding how changes in the brain lead to changes in behavior. Studying face perception in developing infants could help us to understand the parts of the brain that contribute to adult face perception. It might also reveal how face-processing abilities can be impaired in some populations, such as people with Autism.
In adults, the right hemisphere of the brain is critical for recognizing faces. Damage to the right hemisphere, but not the left hemisphere, can impair face recognition. Moreover, the right hemisphere produces larger brain responses than the left hemisphere when a face is seen. This has been witnessed using two different neuroimaging methods. The first, called functional magnetic resonance imaging (fMRI), measures the flow of blood around the brain and relates this to brain activity (e.g., Kanwisher et al., 1997). The second directly measures event-related potentials (ERPs)—the electrical response of a brain region to a stimulus (e.g., Rossion et al., 2003).
In children, there is also evidence that the right and left hemispheres of the brain respond differently to faces (Scherf et al., 2007). Recently it was reported that the response of the right hemisphere to faces is intricately linked to changes that occur in the left hemisphere when children learn to read (Dundas et al., 2014). To date, the majority of studies on infants (who are too young to read) have found no significant differences in how the two sides of the brain respond to faces (e.g., de Haan and Nelson, 1999; Gliga and Dehaene-Lambertz, 2007). However, one group did find response differences between hemispheres when comparing faces to markedly less complex stimuli (patterns of colored dots) (Tzourio-Mazoyer et al., 2002).
Now, in eLife, Adélaïde de Heering and Bruno Rossion from the University of Louvain have used a fast periodic visual stimulation (FPVS) approach to explore face perception in a group of infants aged between four and six months (de Heering and Rossion, 2015). This approach involves presenting images at a rapid, fixed rate in order to induce brain responses that occur at the same rate (often defined as ‘steady-state visual evoked potentials’, SSVEPs; Regan, 1966; for a review, see Norcia et al., 2015).
de Heering and Rossion report that, in the brains of these infants, faces are represented as a distinct category of objects, separate from other categories of objects such as plants or man-made objects. This distinction can be seen most prominently in the response recorded over the right occipito-temporal brain region, which is near the back of the brain. Importantly, faces that vary in size, viewpoint and features (such as the expression and the gender of the faces) are all categorized as faces. This is even the case when the images include naturalistic backgrounds.
These findings provide evidence that by the time they are six months old, infants possess a relatively robust ability to identify that faces are different from objects, and can do so in a realistic context. Moreover, the larger face-related brain responses recorded over the right hemisphere suggest that the right hemisphere of the brain has begun to preferentially respond to faces by six months of age. These findings also complement previous behavioral and ERP work suggesting that infants can distinguish between faces and objects in the first year of life (for a review, see Scott and Nelson, 2004).
Although this technique has been successfully used in infant studies of low-level vision (e.g., Braddick et al., 1986), de Heering and Rossion are among the first researchers to demonstrate the effectiveness of the FPVS technique using complex images in infant research. This is an important addition to the developmental scientist's toolbox and will greatly expand our ability to characterize brain development in infants even before they begin to talk. This technique has been successfully used in a variety of adult investigations but to our knowledge only one other published study reports results from this method with infants (Farzin et al., 2012).
The fact that the FPVS technique can be applied to infant populations has a number of benefits for researchers. Infants can be exposed to hundreds of trials and several conditions within minutes, and no verbal or motor response is required. This large amount of data, collected in a short period of time, results in a higher of proportion data suitable for analysis than in studies using behavior or standard ERP approaches. The increased number of trials also allows researchers to use a variety of visual stimuli that vary in shape, size and orientation, leading to conclusions that are more generalizeable and relevant to real-world situations. Relative to other methods, the FPVS method measures infant brain responses objectively, allowing for precise testing of predictions and easy comparisons across investigations. Finally, the FPVS method measures how the brain tells the difference between various stimulus conditions and provides a direct link between this response and the behavioral tasks commonly used to study infant perception, learning and memory.
References
-
Brain activity differentiates face and object processing in 6-month-old infantsDevelopmental Psychology 35:1113.https://doi.org/10.1037/0012-1649.35.4.1113
-
The fusiform face area: a module in human extrastriate cortex specialized for face perceptionJournal of Neuroscience 17:4302–4311.
-
Review of Psychiatry SeriesReview of Psychiatry Series, Volume 23, American Psychiatric Publishing.
Article and author information
Author details
Publication history
Copyright
© 2015, Hadley and Scott
This article is distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use and redistribution provided that the original author and source are credited.
Metrics
-
- 3,795
- views
-
- 121
- downloads
-
- 0
- citations
Views, downloads and citations are aggregated across all versions of this paper published by eLife.
Download links
A two-part list of links to download the article, or parts of the article, in various formats.
Downloads (link to download the article as PDF)
Open citations (links to open the citations from this article in various online reference manager services)
Cite this article (links to download the citations from this article in formats compatible with various reference manager tools)
Face Recognition: Babies get it right
eLife 4:e08232.
https://doi.org/10.7554/eLife.08232
Further reading
-
- Neuroscience
Perceptual systems heavily rely on prior knowledge and predictions to make sense of the environment. Predictions can originate from multiple sources of information, including contextual short-term priors, based on isolated temporal situations, and context-independent long-term priors, arising from extended exposure to statistical regularities. While the effects of short-term predictions on auditory perception have been well-documented, how long-term predictions shape early auditory processing is poorly understood. To address this, we recorded magnetoencephalography data from native speakers of two languages with different word orders (Spanish: functor-initial vs Basque: functor-final) listening to simple sequences of binary sounds alternating in duration with occasional omissions. We hypothesized that, together with contextual transition probabilities, the auditory system uses the characteristic prosodic cues (duration) associated with the native language’s word order as an internal model to generate long-term predictions about incoming non-linguistic sounds. Consistent with our hypothesis, we found that the amplitude of the mismatch negativity elicited by sound omissions varied orthogonally depending on the speaker’s linguistic background and was most pronounced in the left auditory cortex. Importantly, listening to binary sounds alternating in pitch instead of duration did not yield group differences, confirming that the above results were driven by the hypothesized long-term ‘duration’ prior. These findings show that experience with a given language can shape a fundamental aspect of human perception – the neural processing of rhythmic sounds – and provides direct evidence for a long-term predictive coding system in the auditory cortex that uses auditory schemes learned over a lifetime to process incoming sound sequences.
-
- Cell Biology
- Neuroscience
Reactive astrocytes play critical roles in the occurrence of various neurological diseases such as multiple sclerosis. Activation of astrocytes is often accompanied by a glycolysis-dominant metabolic switch. However, the role and molecular mechanism of metabolic reprogramming in activation of astrocytes have not been clarified. Here, we found that PKM2, a rate-limiting enzyme of glycolysis, displayed nuclear translocation in astrocytes of EAE (experimental autoimmune encephalomyelitis) mice, an animal model of multiple sclerosis. Prevention of PKM2 nuclear import by DASA-58 significantly reduced the activation of mice primary astrocytes, which was observed by decreased proliferation, glycolysis and secretion of inflammatory cytokines. Most importantly, we identified the ubiquitination-mediated regulation of PKM2 nuclear import by ubiquitin ligase TRIM21. TRIM21 interacted with PKM2, promoted its nuclear translocation and stimulated its nuclear activity to phosphorylate STAT3, NF-κB and interact with c-myc. Further single-cell RNA sequencing and immunofluorescence staining demonstrated that TRIM21 expression was upregulated in astrocytes of EAE. TRIM21 overexpressing in mice primary astrocytes enhanced PKM2-dependent glycolysis and proliferation, which could be reversed by DASA-58. Moreover, intracerebroventricular injection of a lentiviral vector to knockdown TRIM21 in astrocytes or intraperitoneal injection of TEPP-46, which inhibit the nuclear translocation of PKM2, effectively decreased disease severity, CNS inflammation and demyelination in EAE. Collectively, our study provides novel insights into the pathological function of nuclear glycolytic enzyme PKM2 and ubiquitination-mediated regulatory mechanism that are involved in astrocyte activation. Targeting this axis may be a potential therapeutic strategy for the treatment of astrocyte-involved neurological disease.
