N170 Adaptation Research Articles

N170 adaptation effect of the sub-lexical phonological and semantic processing in Chinese character reading

N170 adaptation effect of the sub-lexical phonological and semantic processing in Chinese character reading

Face identity is encoded in the duration of N170 adaptation

Previous studies assessing the involvement of the face-sensitive N170 component of the event-related potential (ERP) in the processing of face identity have shown controversial results when assessing N170 amplitude in repetition suppression (RS) designs. On the other hand, N170 adaptation is robustly associated with the inter-stimulus interval (ISI) between immediate face repetitions. Interestingly, interactions of face identity and ISI could provide valuable information on early encoding of face identity, but have not been investigated so far. We employed a repetition suppression paradigm using identical and non-identical repetitions as well as parametrically varied ISIs between 500 msec and 2,000 msec in 27 healthy subjects to investigate N170 adaptation effects. Both face identity and varying ISIs significantly influenced N170 adaptation effects, albeit with small effects sizes. Most importantly, however, face identity and ISIs strongly interacted with rapid N170 amplitude recovery in non-identical trials, but sustained N170 adaptation in identical trials. We excluded low-level sensory contributions to the N170 adaptation effect by analyzing the P1 component and by running an additional experiment employing different stimulus sizes. This specific result strongly argues in favor of neuronal sensitivity to face identity, which is primarily mirrored in the N170 temporal decay function that essentially differentiates identical and non-identical face trials. In general, taking advantage of the temporal dimension of adaptation processes, i.e., their decay over time, provides additional dissections of neuronal function into feature-specific selectivity versus non-selectivity.

Eyeglasses elicit effects similar to face-like perceptual expertise: evidence from the N170 response.

Studies of event-related potentials show that the specific N170 response has become a stable electrophysiological hallmark of objects related to expertise in early perceptual processing. In the present study, we investigated whether eyeglasses can elicit N170 effects similar to those elicited by objects of expertise. Our results showed that the N170 response elicited by eyeglasses was larger than the response elicited by objects that do not generate perceptual expertise (e.g., houses). Importantly, we found that eyeglasses could produce a within-category N170 adaptation effect, similar to that produced in response to objects of expertise (e.g., faces). Our results have revealed for the first time that with a large amount of experience, eyeglasses could evoke the face-like N170 response, which suggested that eyeglasses may become an object of perceptual expertise to some human observers.

When rapid adaptation paradigm is not too rapid: Evidence of face-sensitive N170 adaptation effects

Recent findings have demonstrated that N170 adaptation effects evoked by face adaptors are general to face and non-face tests, implicating adaptor-locked interferences in the rapid adaptation paradigm. Here we examined the extent to which adaptor-locked interferences confound N170 adaptation effects in different experimental parameters by manipulating the stimulus onset asynchrony (SOA) duration and jitter between adaptors and tests. In the short SOA, those interferences were well visible for the grand-average ERP waveforms evoked by tests, and they are likely to render rapid adaptation paradigm with short SOA unreliable. The adaptor-locked interferences were attenuated by appropriately increasing SOA duration, such that face-sensitive adaptation effects were evident in the long SOA for both baseline-to-peak and peak-to-peak N170 measurements. These findings suggest that the rapid adaptation paradigm may work with a relative long SOA. Our findings provide useful information for future studies regarding the choosing of appropriate experimental parameters and measurements for the rapid adaptation paradigm. In addition, future studies are needed to investigate how to objectively subtract the overlaps of adaptors from tests and to validate the N170 adaptation effect with appropriate behavioral performance.

N170 adaptation effect for repeated faces and words

Using ERP adaptation paradigms, studies have shown that the N170 adaptation effect is a stable phenomenon for both faces and words. However, the N170 adaptation effect for repeated identity remains unclear, so we have addressed this with two experiments. In Experiment 1, we investigated the face-related N170 repeated adaptation effect in a short interstimulus interval (ISI) and found that the N170 response elicited by faces was smaller when preceded by a same face adaptor than by another face adaptor. Experiment 2 addressed whether this repeated N170 adaptation effect generalizes to words. For the first time, the results indicated that the N170 response elicited by words was larger with a different word as an adaptor relative to the same word as an adaptor. Our results demonstrate that the face-related N170 response is sensitive to visual face features and extend the characteristics of N170 with the sensitivity to repeated items to other familiar objects of expertise (i.e. words). The results also suggest that there are some common characteristics between faces and words in the early perceptual processing.

The commonality between the perceptual adaptation mechanisms involved in processing faces and nonface objects of expertise.

The authors designed 2 experiments to examine the commonality of the N170 component involved in processing faces and nonface objects of expertise. In Experiment 1, to investigate the N170 adaptation effect between faces and printed language, 18 bilingual participants (7 males) were recruited, and the N170 response elicited by faces and words was recorded using a 128-channel HydroCel Geodesic Sensor Net. To address whether this asymmetrical between-category N170 adaptation effect generalizes to any object of expertise, in Experiment 2, 19 participants (9 males) were recruited by training to become Greeble experts. The N170 component elicited by faces and Greebles was recorded before and after training. In Experiment 1, the authors found that only faces can affect the N170 response elicited by words but words cannot affect the N170 response elicited by face. In Experiment 2, both before and after training, Greeble adaptors did not affect the N170 response elicited by faces. It is important to note that after training, the faces decreased the N170 response elicited by the Greebles. These results suggest that not only is there some commonality of N170 response elicited by face and nonface objects of expertise but also the kinds of functions associated with the N170 neural selectivity to faces were more than that to nonface expert objects.

Normal perception of Mooney faces in developmental prosopagnosia: Evidence from the N170 component and rapid neural adaptation.

Individuals with developmental prosopagnosia (DP) have a severe difficulty recognizing the faces of known individuals in the absence of any history of neurological damage. These recognition problems may be linked to selective deficits in the holistic/configural processing of faces. We used two-tone Mooney images to study the processing of faces versus non-face objects in DP when it is based on holistic information (or the facial gestalt) in the absence of obvious local cues about facial features. A rapid adaptation procedure was employed for a group of 16 DPs. Naturalistic photographs of upright faces were preceded by upright or inverted Mooney faces or by Mooney houses. DPs showed face-sensitive N170 components in response to Mooney faces versus houses, and N170 amplitude reductions for inverted as compared to upright Mooney faces. They also showed the typical pattern of N170 adaptation effects, with reduced N170 components when upright naturalistic test faces were preceded by upright Mooney faces, demonstrating that the perception of Mooney and naturalistic faces recruits shared neural populations. Our findings demonstrate that individuals with DP can utilize global information about face configurations for categorical discriminations between faces and non-face objects, and suggest that face processing deficits emerge primarily at more fine-grained higher level stages of face perception.

Rapid Adaptation Effect of N170 for Printed Words

Faces and written words are two of the most familiar types of visual patterns with the brain's selective response of N170 component in early perception. Using ERP adaptation paradigms, studies have found the N170 response is reduced when there is repeated presentation of upright faces relative to a control condition. In contrast to these well-established features of the face-related N170 adaptation effect, the characteristics of the N170 adaptation effect for printed words are less clear. The goal was to investigate the ERP adaptation effects of printed language (English words and Chinese characters) in a short ISI (200 msec.) adaptation paradigm. The present study showed that both alphabetic words and non-alphabetic words could produce a rapid N170 adaptation effect. Objects of expertise (e.g. words and faces) can produce a rapid N170 adaptation effect but other objects (e.g., houses) cannot, indicating that the specific stimuli have some specific mechanisms for the rapid N170 adaptation.

The overlap of neural selectivity between faces and words: evidences from the N170 adaptation effect.

Faces and words both evoke an N170, a strong electrophysiological response that is often used as a marker for the early stages of expert pattern perception. We examine the relationship of neural selectivity between faces and words by using a novel application of cross-category adaptation to the N170. We report a strong asymmetry between N170 adaptation induced by faces and by words. This is the first electrophysiological result showing that neural selectivity to faces encompasses neural selectivity to words and suggests that the N170 response to faces constitutes a neural marker for versatile representations of familiar visual patterns.

Modulation of the N170 adaptation profile by higher level factors

Event-related potentials provide strong evidence for a face-specific process that peaks at about 170ms following stimulus onset – the N170 effect. The N170 has been shown to be sensitive to adaptation, reflected in an amplitude reduction by repeated face presentation, which is usually considered to be driven by bottom-up processes. Here we investigated whether the N170 adaptation profile can be modulated by top-down factors aiming at holistic or feature-based processing. Adaptor stimuli were Mooney faces, isolated facial features (eyes or mouths), or houses. Target faces required either a gender decision (holistic task), or a decision on a facial feature (detail task). We observed an intricate crossover interaction pattern, reflected in opposite effects on adaptation to Mooney faces and eyes as compared to mouth conditions. These findings provide evidence that adaptation effects can be modulated by top-down processes.

The category‐sensitive and orientation‐sensitive N170 adaptation in faces revealed by comparison with Chinese characters

By comparing faces with Chinese characters, the category-sensitive and orientation-sensitive N170 adaptation effects were examined when the stimuli were adapted by category (within vs. between) and orientation (same vs. different). The category-sensitive N170 adaptation was present for both faces and characters, supporting the assertion that the perception of faces and characters recruits domain-specific processing rather than general processing of visual expertise. In addition, the orientation-sensitive N170 adaptation was present only for faces but not for characters, suggesting that only faces recruit orientation-specific processing. More importantly, the orientation-sensitive N170 adaptation was not only present for inverted faces but also for upright faces, indicating that there are distinct neuron populations respectively sensitive to upright and inverted faces.

Exploring the time course of N170 repetition suppression: A preliminary study

Several studies employed the repetition suppression paradigm to investigate the face-specific N170 component of the event-related potential (ERP), but yielded highly inconsistent results. Varying inter-stimulus intervals (ISIs) may account for inconsistencies between studies. This study aimed at exploring the time course of repetition suppression by systematically investigating the association between ISI and ERP adaptation. Fourteen healthy subjects were investigated with a passive face recognition paradigm using paired stimuli. Stimuli were presented for 500ms and ISIs parametrically varied between 400 and 2000ms. N170 was constructed to investigate adaptation effects on the level of perceptual face processing. We found an evidence for an asymptotic decay of repetition suppression over time with significant N170 adaptation effects only after the shortest ISI. Our results robustly demonstrate that N170 adaptation in a paired stimulus protocol critically depends on short ISIs, thereby explaining the inconsistencies observed in the previous studies. For future social cognition studies using neuronal adaptation to face stimuli, the current results provide a well defined ISI associated with a large N170 adaptation effect.

Response Profile of the Face-Sensitive N170 Component: A Rapid Adaptation Study

To study the response profile of the face-selective N170 component, an adaptation procedure was employed where adaptor and test stimuli were presented in rapid succession. Test stimuli came from 4 different face categories (upright, inverted, and eyeless faces and eyes-only images). The same face stimuli, as well as upright and inverted houses, served as adaptors. Strong N170 amplitude reductions indicative of adaptation were found for all types of face test stimuli preceded by face adaptors relative to house adaptors, demonstrating that at a generic level, the N170 reflects the activation of face-selective neurons by full faces and by face parts. The highly specific pattern of N170 adaptation effects for different combinations of adaptor and test stimulus categories suggests additional distinct contributions of eye-selective neurons and of face-sensitive neurons that are tuned to deviations from canonical stimulus orientations to the N170 component. Results demonstrate that the N170 is generated by multiple neural sources at both early and later stages of configural face processing and that rapid adaptation techniques provide a powerful tool to dissociate these sources.

Face processing in humans is compatible with a simple shape–based model of vision

Understanding how the human visual system recognizes objects is one of the key challenges in neuroscience. Inspired by a large body of physiological evidence, a general class of recognition models has emerged, which is based on a hierarchical organization of visual processing, with succeeding stages being sensitive to image features of increasing complexity. However, these models appear to be incompatible with some well-known psychophysical results. Prominent among these are experiments investigating recognition impairments caused by vertical inversion of images, especially those of faces. It has been reported that faces that differ 'featurally' are much easier to distinguish when inverted than those that differ 'configurally'; a finding that is difficult to reconcile with the physiological models. Here, we show that after controlling for subjects' expectations, there is no difference between 'featurally' and 'configurally' transformed faces in terms of inversion effect. This result reinforces the plausibility of simple hierarchical models of object representation and recognition in the cortex.