Neural correlates of temporal integration in face recognition: An fMRI study

The impact of aging and repetition on eye movements and recognition memory

The modulation of gaze fixations on neural activity in the hippocampus, a region critical for memory, has been shown to be weaker in older adults compared to younger adults. However, as such research has relied on indirect measures of memory, it remains unclear whether the relationship between visual exploration and direct measures of memory is similarly disrupted in aging. The current study tested older and younger adults on a face memory eye-tracking task previously used by our group that showed that recognition memory for faces presented across variable, but not fixed, viewpoints relies on a hippocampal-dependent binding function. Here, we examined how aging influences eye movement measures that reveal the amount (cumulative sampling) and extent (distribution of gaze fixations) of visual exploration. We also examined how aging influences direct (subsequent conscious recognition) and indirect (eye movement repetition effect) expressions of memory. No age differences were found in direct recognition regardless of facial viewpoint. However, the eye movement measures revealed key group differences. Compared to younger adults, older adults exhibited more cumulative sampling, a different distribution of fixations, and a larger repetition effect. Moreover, there was a positive relationship between cumulative sampling and direct recognition in younger adults, but not older adults. Neither age group showed a relationship between the repetition effect and direct recognition. Thus, despite similar direct recognition, age-related differences were observed in visual exploration and in an indirect eye-movement memory measure, suggesting that the two groups may acquire, retain, and use different facial information to guide recognition.

Distinct neural-behavioral correspondence within face processing and attention networks for the composite face effect

The composite face effect (CFE) is recognized as a hallmark for holistic face processing, but our knowledge remains sparse about its cognitive and neural loci. Using functional magnetic resonance imaging with independent localizer and complete composite face task, we here investigated its neural-behavioral correspondence within face processing and attention networks. Complementing classical comparisons, we adopted a dimensional reduction approach to explore the core cognitive constructs of the behavioral CFE measurement. Our univariate analyses found an alignment effect in regions associated with both the extended face processing network and attention networks. Further representational similarity analyses based on the Euclidian distances among all experimental conditions were used to identify cortical regions with reliable neural-behavioral correspondences. Multidimensional scaling and hierarchical clustering analyses for neural-behavioral correspondence data revealed two principal components underlying the behavioral CFE effect, which fit best to the neural responses in the bilateral insula and medial frontal gyrus. These findings highlight the distinct neurocognitive contributions of both face processing and attentional networks to the behavioral CFE outcome, which bridge the gaps between face recognition and attentional control models.

Stress and the medial temporal lobe at rest: Functional connectivity is associated with both memory and cortisol

When acute stress is experienced immediately after memory encoding (i.e., post-encoding stress) it can significantly impact subsequent memory for that event. For example, recent work has suggested that post-encoding stress occurring in a different context from encoding impairs memory. However, the neural processes underlying these effects are poorly understood. We aimed to expand this understanding by conducting an analysis of resting functional connectivity in the period following post-encoding stress that occurred in a different context than encoding, using seed regions in the medial temporal lobes known for their roles in memory. In the current study of 44 males randomized to stress (n = 23) or control (n = 21) groups, we found that stress increased cortisol, impaired recollection of neutral materials, and altered functional connectivity with medial temporal lobe regions. Although stress did not significantly alter hippocampus-amygdala functional connectivity, relative to participants in the control group, participants in the post-encoding stress group showed lower functional connectivity between the hippocampus and a region with a peak in the superior temporal gyrus. Across participants in both groups, functional connectivity between these regions was related to greater increases in cortisol, and it was also inversely related to recollection of neutral materials. In contrast, the stress group showed greater parahippocampal cortex functional connectivity with a region in the left middle temporal gyrus than the control group. Moreover, greater functional connectivity between the parahippocampal cortex and the observed cluster in the middle temporal gyrus was associated with greater cortisol changes from pre- to post-manipulation, but was not related to differences in memory. The results show that post-encoding stress can alter the resting-state functional connectivity between the medial temporal lobe and neocortex, which may help explain how stress impacts memory.

Dynamic neural mechanisms underlie race disparities in social cognition

Race disparities in behavior may emerge in several ways, some of which may be independent of implicit bias. To mitigate the pernicious effects of different race disparities for racial minorities, we must understand whether they are rooted in perceptual, affective, or cognitive processing with regard to race perception. We used fMRI to disentangle dynamic neural mechanisms predictive of two separable race disparities that can be obtained from a trustworthiness ratings task. Increased coupling between regions involved in perceptual and affective processing when viewing Black versus White faces predicted less later racial trust disparity, which was related to implicit bias. In contrast, increased functional coupling between regions involved in controlled processing predicted less later disparity in the differentiation of Black versus White faces with regard to perceived trust, which was unrelated to bias. These findings reveal that distinct neural signatures underlie separable race disparities in social cognition that may or may not be related to implicit bias.

Facial Expression Aftereffect Revealed by Adaption to Emotion-Invisible Dynamic Bubbled Faces

Visual adaptation is a powerful tool to probe the short-term plasticity of the visual system. Adapting to local features such as the oriented lines can distort our judgment of subsequently presented lines, the tilt aftereffect. The tilt aftereffect is believed to be processed at the low-level of the visual cortex, such as V1. Adaptation to faces, on the other hand, can produce significant aftereffects in high-level traits such as identity, expression, and ethnicity. However, whether face adaptation necessitate awareness of face features is debatable. In the current study, we investigated whether facial expression aftereffects (FEAE) can be generated by partially visible faces. We first generated partially visible faces using the bubbles technique, in which the face was seen through randomly positioned circular apertures, and selected the bubbled faces for which the subjects were unable to identify happy or sad expressions. When the subjects adapted to static displays of these partial faces, no significant FEAE was found. However, when the subjects adapted to a dynamic video display of a series of different partial faces, a significant FEAE was observed. In both conditions, subjects could not identify facial expression in the individual adapting faces. These results suggest that our visual system is able to integrate unrecognizable partial faces over a short period of time and that the integrated percept affects our judgment on subsequently presented faces. We conclude that FEAE can be generated by partial face with little facial expression cues, implying that our cognitive system fills-in the missing parts during adaptation, or the subcortical structures are activated by the bubbled faces without conscious recognition of emotion during adaptation.

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.

The neural basis of maternal bonding

Background

Accumulating evidence suggests that mothers show a different pattern of brain responses when viewing their own compared to other infants. However, there is inconsistency across functional imaging studies regarding the key areas involved, and none have examined relationships between brain and behavioural responses to infants. We examined the brain regions activated when mothers viewed videos of their own infant contrasted with an unknown infant, and whether these are associated with behavioural and self-reported measures of mother-infant relations.

Method

Twenty right-handed mothers viewed alternating 30-sec blocks of video of own 4–9 month infant and an unfamiliar matched infant, interspersed with neutral video. Whole brain functional magnetic resonance images (fMRI) were acquired on a 1.5T Philips Intera scanner using a TR of 2.55 s. Videotaped mother-infant interactions were systematically evaluated blind to family information to generate behavioural measures for correlational analysis.

Results

Enhanced blood oxygenation functional imaging responses were found in the own versus unknown infant contrast in the bilateral precuneus, right superior temporal gyrus, right medial and left middle frontal gyri and left amygdala. Positive mother-infant interaction (less directive parent behaviour; more positive/attentive infant behaviour) was significantly associated with greater activation in several regions on viewing own versus unknown infant, particularly the middle frontal gyrus. Mothers' perceived warmth of her infant was correlated with activations in the same contrast, particularly in sensory and visual areas.

Conclusion

This study partially replicates previous reports of the brain regions activated in mothers in response to the visual presentation of their own infant. It is the first to report associations between mothers' unique neural responses to viewing their own infant with the quality of her concurrent behaviour when interacting with her infant and with her perceptions of infant warmth. These findings provide support for developing fMRI as a potential biomarker of parenting risk and change.

The neuroscience of face processing and identification in eyewitnesses and offenders

Humans are experts in face perception. We are better able to distinguish between the differences of faces and their components than between any other kind of objects. Several studies investigating the underlying neural networks provided evidence for deviated face processing in criminal individuals, although results are often confounded by accompanying mental or addiction disorders. On the other hand, face processing in non-criminal healthy persons can be of high juridical interest in cases of witnessing a felony and afterward identifying a culprit. Memory and therefore recognition of a person can be affected by many parameters and thus become distorted. But also face processing itself is modulated by different factors like facial characteristics, degree of familiarity, and emotional relation. These factors make the comparison of different cases, as well as the transfer of laboratory results to real live settings very challenging. Several neuroimaging studies have been published in recent years and some progress was made connecting certain brain activation patterns with the correct recognition of an individual. However, there is still a long way to go before brain imaging can make a reliable contribution to court procedures.

Influence of reward on corticospinal excitability during movement preparation

Current models of decision making postulate that action selection entails a competition within motor-related areas. According to this view, during action selection, motor activity should integrate cognitive information (e.g., reward) that drives our decisions. We tested this hypothesis in humans by measuring motor-evoked potentials (MEPs) in a left finger muscle during motor preparation in a hand selection task, in which subjects performed left or right key presses according to an imperative signal. This signal was either obvious or ambiguous, but subjects were always asked to react as fast as possible. When the signal was really indistinct, any key press was regarded as correct, so subjects could respond "at random" in those trials. A score based on reaction times was provided after each correct response, and subjects were told they would receive a monetary reward proportional to their final score. Importantly, the scores were either equitable for both hands or favored implicitly left responses (reward(neutral) and reward(biased) blocks, respectively). We found that subjects selected their left hand more often in the reward(biased) than in the reward(neutral) condition, particularly after ambiguous signals. Moreover, left MEPs were larger, as soon as the signal appeared, in the reward(biased) than in the reward(neutral) conditions. During the course of motor preparation, this effect became strongest following ambiguous signals, a condition in which subjects' choices relied strongly on the reward. These results indicate that motor activity is shaped by a cognitive variable that drives our choices, possibly in the context of a competition taking place within motor-related areas.