Face Recognition and the Social Individual

Face recognition depends upon the uniqueness of each human face. This is accomplished by the patterns formed by the unique relationship among face features. Unique face-patterns are produced by the intrusion of random factors into the process of biological growth and development. Processes are described which enable a unique face-pattern to be represented as a percept in the visual sensory system. The components of the face recognition system are analyzed as is the manner in which the precept is connected through microcircuits to a memory file so that the history of a perceiver’s encounters with a familiar face enables the perceiver to access a memory store that is a record of the outcome of past encounters with the perceived. The importance of the face recognition system in enabling humans to individuate members the social group is discussed, as well as the importance of face recognition in the development of the individual’s social identity and ability to be a collaborative member of the social groups to which it belongs. The role of prosopagnosia—the inability to recognize familiar faces—in furthering an understanding of the face recognition system is examined, as is its importance in demonstrating the crucial nature of face recognition in human social functions. It is proposed that human face recognition is not a unique phenomenon but is an elaboration of processes existing in nonhuman primates as well as in lower animals.     

Orientation-contingent face aftereffects and implications for face-coding mechanisms

Humans have an impressive ability to discriminate between faces despite their similarity as visual patterns. This expertise relies on configural coding of spatial relations between face features and/or holistic coding of overall facial structure. These expert face-coding mechanisms appear to be engaged most effectively by upright faces, with inverted faces engaging primarily feature-coding mechanisms. We show that opposite figural aftereffects can be induced simultaneously for upright and inverted faces, demonstrating that distinct neural populations code upright and inverted faces. This result also suggests that expert (upright) face-coding mechanisms can be selectively adapted. These aftereffects occur for judgments of face normality and face gender and are robust to changes in face size, ruling out adaptation of low-level, retinotopically organized coding mechanisms. Our results suggest a resolution of a paradox in the face recognition literature. Neuroimaging studies have found surprisingly little orientation selectivity in the fusiform face area (FFA) despite evidence that this region plays a role in expert face coding and that expert face-coding mechanisms are selectively engaged by upright faces. Our results, demonstrating orientation-contingent adaptation of face-coding mechanisms, suggest that the FFA's apparent lack of orientation selectivity may be an artifact of averaging across distinct populations within the FFA that respond to upright and inverted faces.     

A new approach to the diagnosis of deficits in processing faces: Potential application in autism research

Deficits in social communication are one of the behavioral signatures of autism spectrum disorder(ASD). Because faces are arguably the most important social stimuli that we encounter in everyday life, investigating the ability of individuals with ASD to process faces is thought to be important for understanding the nature of ASD. However, although a considerable body of evidence suggests that ASD individuals show specific impairments in face processing, a significant number of studies argue otherwise. Through a literature review, we found that this controversy is largely attributable to the different face tests used across different studies. Therefore, a more reliable and valid face test is needed. To this end, we performed a meta-analysis on data gleaned from a variety of face tests conducted on individuals with developmental prosopagnosia(DP) who suffer a selective deficit in face processing. Based on this meta-analysis, we selected an old/new face recognition test that relies on face memory as a standard diagnostic test for measuring specific face processing deficits. This test not only reliably reflects DP individuals' subjective experiences with faces in their daily lives, but also effectively differentiates deficits in face processing from deficits caused by other general problems. In addition, DP individuals' performance in this test predicts their performance in a variety of face tests that examine specific components of face processing(e.g., holistic processing of faces). Finally, this test can be easily administrated and is not overly sensitive to prior knowledge. In summary, this test can be used to evaluate face-processing ability, and it helped to resolve the controversy whether individuals with ASD exhibit face-processing deficits.     

Optimized Transection: A Prelude to Oriented Sectioning

A technique is described which permits blocks of tissue to be flat-embedded in euhedral plastic castings and then to be transected along a plane so that sections may be cut which are optimally oriented to the internal ultrastructure of the block. In the transection procedure a hollow plastic cylinder is placed on the specimen trimming block. The cylinder's top prescribes a plane to which the tissue block is accurately oriented and clamped at a predetermined level. Two hand files and a burnisher are worked across the cylinder's top to 1) remove extraneous material above the plane of transection, 2) expose the tissue for sectioning and 3) smooth the block face. The clear plastic at the periphery of the exposed tissue is then easily trimmed away with a razor blade. The result is a block face with a flat, reflective surface which may be quickly aligned to the knife on the ultramicrotome. The effort needed to transect, align and face the block is minimal and 1-micron or semithin sections produced will be precisely parallel to, and at, the plane of transection. Dust produced by the transection procedure is easily eliminated from the work area by use of a small disposable vacuum cleaner. The technique of producing optimally oriented light microscope sections, using the transector, is enhanced by application of solvents to the block face which cause it to develop a temporary low relief, exactly matching the structural detail of sections cut from the block face. Areas of interest can be accurately located and isolated on the block face, using only a hand-held razor blade, so that oriented ultrathin sections of important regions can be routinely cut and examined in the electron microscope.     

Simple and Rapid Block Face Alignment Methods for the Ultramicrotome

Light from the fluorescent lamp on an ultramicrotome can be reflected from a mirror located beneath the knife face 50 that the knife and edge can he imaged on the block face. It is well known that this image can be used to accurately align the block face to the knife edge and cutting direction. A method is described of pre-aligning the lamp, stereomicroscope, knife, and the mirror, which is fixed with respect to the knife face, 80 that a bright reflection of the knife face on the block face is obtained only when the block face is brought close to alignment. This initial alignment is an extremely rapid procedure, and is followed by slower, more accurate manipulation of the block and knife for precise alignment.

The mirror, easily mounted to a Porter-Blum MT-2 ultramicrotome knife holder, is very simple in design and readily adaptable to any ultramicrotome. Methods to permit small movements of the block for the MT-1 and MT-P ultramicrotomes are also descrihed.     

Neural mechanism of dynamic responses of neurons in inferior temporal cortex in face perception

Understanding the neural mechanisms of object and face recognition is one of the fundamental challenges of visual neuroscience. The neurons in inferior temporal (IT) cortex have been reported to exhibit dynamic responses to face stimuli. However, little is known about how the dynamic properties of IT neurons emerge in the face information processing. To address this issue, we made a model of IT cortex, which performs face perception via an interaction between different IT networks. The model was based on the face information processed by three resolution maps in early visual areas. The network model of IT cortex consists of four kinds of networks, in which the information about a whole face is combined with the information about its face parts and their arrangements. We show here that the learning of face stimuli makes the functional connections between these IT networks, causing a high spike correlation of IT neuron pairs. A dynamic property of subthreshold membrane potential of IT neuron, produced by Hodgkin–Huxley model, enables the coordination of temporal information without changing the firing rate, providing the basis of the mechanism underlying face perception. We show also that the hierarchical processing of face information allows IT cortex to perform a “coarse-to-fine” processing of face information. The results presented here seem to be compatible with experimental data about dynamic properties of IT neurons.     

Effects of unconscious processing on implicit memory for fearful faces

Emotional stimuli can be processed even when participants perceive them without conscious awareness, but the extent to which unconsciously processed emotional stimuli influence implicit memory after short and long delays is not fully understood. We addressed this issue by measuring a subliminal affective priming effect in Experiment 1 and a long-term priming effect in Experiment 2. In Experiment 1, a flashed fearful or neutral face masked by a scrambled face was presented three times, then a target face (either fearful or neutral) was presented and participants were asked to make a fearful/neutral judgment. We found that, relative to a neutral prime face (neutral-fear face), a fearful prime face speeded up participants' reaction to a fearful target (fear-fear face), when they were not aware of the masked prime face. But this response pattern did not apply to the neutral target. In Experiment 2, participants were first presented with a masked faces six times during encoding. Three minutes later, they were asked to make a fearful/neutral judgment for the same face with congruent expression, the same face with incongruent expression or a new face. Participants showed a significant priming effect for the fearful faces but not for the neutral faces, regardless of their awareness of the masked faces during encoding. These results provided evidence that unconsciously processed stimuli could enhance emotional memory after both short and long delays. It indicates that emotion can enhance memory processing whether the stimuli are encoded consciously or unconsciously.     

Electrical Stimulation over Bilateral Occipito-Temporal Regions Reduces N170 in the Right Hemisphere and the Composite Face Effect

Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation technique that can modulate cortical excitability. Although the clinical value of tDCS has been advocated, the potential of tDCS in cognitive rehabilitation of face processing deficits is less understood. Face processing has been associated with the occipito-temporal cortex (OT). The present study investigated whether face processing in healthy adults can be modulated by applying tDCS over the OT. Experiment 1 investigated whether tDCS can affect N170, a face-sensitive ERP component, with a face orientation judgment task. The N170 in the right hemisphere was reduced in active stimulation conditions compared with the sham stimulation condition for both upright faces and inverted faces. Experiment 2 further demonstrated that tDCS can modulate the composite face effect, a type of holistic processing that reflects the obligatory attention to all parts of a face. The composite face effect was reduced in active stimulation conditions compared with the sham stimulation condition. Additionally, the current polarity did not modulate the effect of tDCS in the two experiments. The present study demonstrates that N170 can be causally manipulated by stimulating the OT with weak currents. Furthermore, our study provides evidence that obligatory attention to all parts of a face can be affected by the commonly used tDCS parameter setting.     

Ultrastructure of the calcium release channel of sarcoplasmic reticulum

This study is concerned with the characterization of the morphology of the calcium release channel of sarcoplasmic reticulum (SR) from fast-twitch skeletal muscle, which is involved in excitation-contraction coupling. We have previously purified the ryanodine receptor and found it to be equivalent to the feet structures, which are involved, in situ, in the junctional association of transverse tubules with terminal cisternae of SR. The receptor is an oligomer of a single high molecular weight polypeptide and when incorporated into phospholipid bilayers, has channel conductance which is characteristic of calcium release in terminal cisternae of SR. The purified channel can be observed by electron microscopy using different methods of sample preparation, with complementary views being observed by negative staining, double staining, thin section and rotary shadowing electron microscopy. Three views can be observed and interpreted: (a) a square face which, in situ, is junctionally associated with the transverse tubule or junctional face membrane; (b) a rectangle equivalent to the side view; and (c) a diamond shape equivalent to the side view, of which the base portion appears to be equivalent to the transmembrane segment. Negative staining reveals detailed substructure of the channel. A computer averaged view of the receptor displays fourfold symmetry and ultrastructural detail. The dense central mass is divided into four domains with a 2-nm hole in the center, and is enclosed within an outer frame which has a pinwheel appearance. Double staining shows substructure of the square face in the form of parallel linear arrays (six/face). The features of the isolated receptor can be correlated with the structure observed in terminal cisternae vesicles. Sections tangential to the junctional face membrane reveal that the feet structures (23-nm squares) overlap so as to enclose smaller square spaces of approximately 14 nm/side. We suggest that this is equivalent to the transverse tubule face and that the terminal cisternae face is smaller (approximately 17 nm/face) and has larger alternating spaces as a consequence of the tapered sides of the foot structures. Image reconstruction analysis appears to be feasible and should provide the three-dimensional structure of the channel.     

Passive and motivated perception of emotional faces: qualitative and quantitative changes in the face processing network

Emotionally expressive faces are processed by a distributed network of interacting sub-cortical and cortical brain regions. The components of this network have been identified and described in large part by the stimulus properties to which they are sensitive, but as face processing research matures interest has broadened to also probe dynamic interactions between these regions and top-down influences such as task demand and context. While some research has tested the robustness of affective face processing by restricting available attentional resources, it is not known whether face network processing can be augmented by increased motivation to attend to affective face stimuli. Short videos of people expressing emotions were presented to healthy participants during functional magnetic resonance imaging. Motivation to attend to the videos was manipulated by providing an incentive for improved recall performance. During the motivated condition, there was greater coherence among nodes of the face processing network, more widespread correlation between signal intensity and performance, and selective signal increases in a task-relevant subset of face processing regions, including the posterior superior temporal sulcus and right amygdala. In addition, an unexpected task-related laterality effect was seen in the amygdala. These findings provide strong evidence that motivation augments co-activity among nodes of the face processing network and the impact of neural activity on performance. These within-subject effects highlight the necessity to consider motivation when interpreting neural function in special populations, and to further explore the effect of task demands on face processing in healthy brains.     

On a newly modified method for plastic reconstruction of the face using the skull (based on Kollman data)

Since Kollmann & Büchly (1898) presented for the first time a plastic reconstruction of the face on the skull, which was based on empiric data, this method has been improved continuously. Up to now, however, doubts on its reliability could not be removed completely. While in the meantime the reconstruction of the large organs of the face could be based on a more secured empiric basis, this was not possible concerning the remaining surface of the face. This could be surmounted using the measurements of the soft parts of the living body (34 items) proposed by Helmer (1980). Basing on these measurements the author presents a newly modified method for the plastic reconstruction of the face on the skull. Among others he accepts as basic pattern the principle of parallel profile lines suggested by Helmer (to identify skulls by means of superposition of electronic pictures). By that the author is of the opinion that he has improved the possibility of verifying and reproducing acquired results. It is recommended to fill still uncertain methodological gaps by distinct working hypothesis. However, on plastic reconstructions unclear details should be treated in such a way that they are standing out against the remaining surface. The potential scope of the plastic reconstruction of the face on the skull has been limited by Helmer's method (identification of skulls), but is basically still unchanged.     

Three-dimensional solution structure of Acanthamoeba profilin-I

We have determined a medium resolution three-dimensional solution structure of Acanthamoeba profilin-I by multidimensional nuclear magnetic resonance spectroscopy. This 13-kD actin binding protein consists of a five stranded antiparallel beta sheet flanked by NH2- and COOH-terminal helices on one face and by a third helix and a two stranded beta sheet on the other face. Data from actin-profilin cross- linking experiments and the localization of conserved residues between profilins in different phyla indicate that actin binding occurs on the molecular face occupied by the terminal helices. The other face of the molecule contains the residues that differ between Acanthamoeba profilins-I and II and may be important in determining the difference in polyphosphoinositide binding between these isoforms. This suggests that lipids and actin bind to different faces of the molecule.     

Optimized transection: a prelude to oriented sectioning

A technique is described which permits blocks of tissue to be flat-embedded in euhedral plastic castings and then to be transected along a plane so that sections may be cut which are optimally oriented to the internal ultrastructure of the block. In the transection procedure a hollow plastic cylinder is placed on the specimen trimming block. The cylinder's top prescribes a plane to which the tissue block is accurately oriented and clamped at a predetermined level. Two hand files and a burnisher are worked across the cylinder's top to 1) remove extraneous material above the plane of transection, 2) expose the tissue for sectioning and 3) smooth the block face. The clear plastic at the periphery of the exposed tissue is then easily trimmed away with a razor blade. The result is a block face with a flat, reflective surface which may be quickly aligned to the knife on the ultramicrotome. The effort needed to transect, align and face the block is minimal and 1-micron or semithin sections produced will be precisely parallel to, and at, the plane of transection. Dust produced by the transection procedure is easily eliminated from the work area by use of a small disposable vacuum cleaner. The technique of producing optimally oriented light microscope sections, using the transector, is enhanced by application of solvents to the block face which cause it to develop a temporary low relief, exactly matching the structural detail of sections cut from the block face.(ABSTRACT TRUNCATED AT 250 WORDS)     

Methods for Precisely Trimming Block Faces for Ultramicrotomy

Two devices are described to aid in trimming block faces of embedded tissue for ultramicrotomy. The first, a reticle to fit the ocular of a stereomicroscope, can be manufactured by the ultramicrotomist and is designed to outline the edges of the block face so that it can be trimmed to a standard size and shape with the area of interest centered in it. The second, a rectangular “trim-align” block mounted in the knife holder of the uitramicrotome, is, with the block face, aligned to the plane of sectioning, and aids in retrimming the top and bottom edges of the block face. This is the simplest trimming device yet described and the first which will, from any sort of embedded material, produce a block face with parallel top and bottom edges even if the block face is not perpendicular to the axis of the specimen holder. If the edge of the diamond knife used for sectioning is parallel to the axis of rotation of the knife holder, the block face has also been automatically aligned to the knife as a consequence of this aligning and trimming procedure. As a result, sectioning can begin immediately without further adjustments.     

Use of High Intensity Illumination to Aid Alignment of Knife Edge and Block Face for Ultramicrotomy

Alignment of a diamond or glass knife with the face of an epoxy block, prior to sectioning, can be facilitated by the use of high intensity illumination. Such light produces a brilliant reflection of the knife edge on the block face in the form of a bright band which diminishes in height as the knife approaches the block face. Excellent visibility of block face and knife edge is afforded at magnifications up to 40. Allowing the block to cool for 1 min counteracts the thermal effects of the light before sectioning commences. This technique provides a convenient alternative to the use of reflecting devices for alignment of the knife during its approach to the block.     

Face cooling-induced reduction of plasma prolactin response to exercise as part of an integrated response to thermal stress

This study was designed to verify if the decrease in blood prolactin (PRL) induced by selective face cooling during exercise could be part of a response to specific body thermal stress. Five healthy trained male cyclists presenting a significant plasma PRL elevation to exercise were, on three occasions and at weekly interval, submitted to a submaximal exercise (approx. 65% VO2max) on ergocycle with and without selective face cooling. In absence of face cooling a first trial served to establish reference values for workload, heart rate and plasma PRL levels, the latter increasing markedly (450% of resting values) in these conditions. On a second trial but with workload maintained at reference values (222 +/- 9 W), a significant bradycardia was observed with face cooling; furthermore, plasma PRL response to exercise was significantly reduced (to 31% of original response). On a third trial with face cooling, workload had to be significantly augmented (242 +/- 10 W) to maintain heart rate at reference level (78% HRmax); in addition, plasma PRL response to exercise was almost unchanged compared to the reference-value level. The absence of a significant face cooling-induced decrease in sympathetic tonus, as evaluated through peripheral plasma catecholamines response, does not indicate a role for the autonomic nervous system in the face cooling-induced reduction of both heart rate and PRL responses during exercise. Assay of circulating peripheral beta-endorphins could indicate that the face cooling-induced PRL blunted response does not necessarily involve an opioid mediation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Observations on the innervated face of the electrocyte of the main organ of the electric eel (Electrophorus electricus L.)

Summary The innervated face of electrocytes in the main electric organ of Electrophorus electricus L. was examined by light microscopy, both conventional and with Nomarski contrast, and by transmission and scanning electron microscopy. Acetylcholinesterase cytochemistry was used in the demonstration of the greater density of synapses over the caudal papillae. The various techniques contributed to a better understanding of the distribution and form of papillae and synapses at the posterior face of the electrocyte. Caudal papillae are longer and thinner than those at the rostral face, but it was not possible to recognize a different type sometimes referred to in the literature as small papillae. The contact of nerve endings with the electrocyte seems to be made predominantly on the terminal half of caudal papillae, however a smaller number occur elsewhere on the posterior face. Synaptic terminals frequently appear as round profiles, but may be also elongated, with or without bulges, usually occupying a depression, and separated from the post-synaptic membrane by a space of 60–100 nm, where an expansion may be found.     

A freeze fracture study of the developing tegumental outer membrane of Schistosoma mansoni

The freeze fracture technique has been used to quantify changes in the integral components of the double outer membrane of Schistosoma mansoni during the 6-week period of development within the mouse. The intramembraneous particle (IMP) density on the P1 face begins to rise within 6 h of host penetration, reaches a maximum at day 4 and then falls rapidly after day 9, so that it is at a low level between 3 and 6 weeks. The E1 face IMP density follows the same course as that of the P1 face except that maximum particle density is recorded on day 1 and the counts begin to fall on day 5. The IMP density on the P2 face remains at a consistently low level throughout development. The E2 face IMP density rises gradually to a peak at day 4, when the parasites have migrated to the lungs, and remains thereafter at a similar level, so that by 6 weeks the E2 face has a higher IMP density than the other three fracture faces. The E2 face IMP show a marked increase in size on day 4. Morphological studies indicate that a different type of inclusion body makes a transient appearance in the tegument of the lung worms, and immunocytochemical techniques show the lung worms to be nonimmunogenic. It is suggested, therefore, that the E2 face IMP may represent complexes of parasite antigens and acquired host antigens. The tegumental membranes of cultured specimens have also been examined by freeze fracturing and the IMP densities compared with those obtained from in vivo parasites; the cultured schistosomula have a lower E2 face particle density than the in vivo specimens.     

Experiences with development of morphological typology of the face

On base of the component analysis of facial dimensions the original diagnostic model of definition of a morphological facial type in Russian males and females is developed. The first typological characteristic feature describes the variability of general face size, allocating extreme micro- and macrotypes. The second one describes the face shape as a ratio of frontal and mandibular parts. On poles of variability it demonstrates a type with massive frontal face part and rather reduced mandibular one, and a contrast type with a massive mandibular part at relative gracile frontal face part. Central position in this model is occupied by variants with equally proportional development of the top and bottom face parts. On the basis of seven traditional anthropometric facial dimensions the place of any individual in terms of face size and form can be easily found in the suggested model. The chosen contrast variants of the face form are comparable to the appropriate characteristics of cerebral and digestive Sigaud types. The offered morphotypology allows to estimate accurately individual and group features in the face form. The methods of multivariate analysis reveal steady connection between somatotypes and features of a facial structure. Though the level of correlation does not exceed 0.3-0.4 of correlation coefficients, it is statistically significant at the highest degree of probability. The basic direction of habitus variability in men is observed at general face size, in women at face shape.     

The many faces of research on face perception

Face perception is fundamental to human social interaction. Many different types of important information are visible in faces and the processes and mechanisms involved in extracting this information are complex and can be highly specialized. The importance of faces has long been recognized by a wide range of scientists. Importantly, the range of perspectives and techniques that this breadth has brought to face perception research has, in recent years, led to many important advances in our understanding of face processing. The articles in this issue on face perception each review a particular arena of interest in face perception, variously focusing on (i) the social aspects of face perception (attraction, recognition and emotion), (ii) the neural mechanisms underlying face perception (using brain scanning, patient data, direct stimulation of the brain, visual adaptation and single-cell recording), and (iii) comparative aspects of face perception (comparing adult human abilities with those of chimpanzees and children). Here, we introduce the central themes of the issue and present an overview of the articles.