Margot J. Taylor

Guidelines for using human event-related potentials to study cognition: recording standards and publication criteria.

Event-related potentials (ERPs) recorded from the human scalp can provide important information about how the human brain normally processes information and about how this processing may go awry in neurological or psychiatric disorders. Scientists using or studying ERPs must strive to overcome the many technical problems that can occur in the recording and analysis of these potentials. The methods and the results of these ERP studies must be published in a way that allows other scientists to understand exactly what was done so that they can, if necessary, replicate the experiments. The data must then be analyzed and presented in a way that allows different studies to be compared readily. This paper presents guidelines for recording ERPs and criteria for publishing the results.

Early processing of the six basic facial emotional expressions.

Facial emotions represent an important part of non-verbal communication used in everyday life. Recent studies on emotional processing have implicated differing brain regions for different emotions, but little has been determined on the timing of this processing. Here we presented a large number of unfamiliar faces expressing the six basic emotions, plus neutral faces, to 26 young adults while recording event-related potentials (ERPs). Subjects were naive with respect to the specific questions investigated; it was an implicit emotional task. ERPs showed global effects of emotion from 90 ms (P1), while latency and amplitude differences among emotional expressions were seen from 140 ms (N170 component). Positive emotions evoked N170 significantly earlier than negative emotions and the amplitude of N170 evoked by fearful faces was larger than neutral or surprised faces. At longer latencies (330-420 ms) at fronto-central sites, we also found a different pattern of effects among emotions. Localization analyses confirmed the superior and middle-temporal regions for early processing of facial expressions; the negative emotions elicited later, distinctive activations. The data support a model of automatic, rapid processing of emotional expressions.

Inversion and contrast polarity reversal affect both encoding and recognition processes of unfamiliar faces: a repetition study using ERPs.

Using ERPs in a face recognition task, we investigated whether inversion and contrast reversal, which seem to disrupt different aspects of face configuration, differentially affected encoding and memory for faces. Upright, inverted, and negative (contrast-reversed) unknown faces were either immediately repeated (0-lag) or repeated after 1 intervening face (1-lag). The encoding condition (new) consisted of the first presentation of items correctly recognized in the two repeated conditions. 0-lag faces were recognized better and faster than 1-lag faces. Inverted and negative pictures elicited longer reaction times, lower hit rates, and higher false alarm rates than upright faces. ERP analyses revealed that negative and inverted faces affected both early (encoding) and late (recognition) stages of face processing. Early components (N170, VPP) were delayed and enhanced by both inversion and contrast reversal which also affected P1 and P2 components. Amplitudes were higher for inverted faces at frontal and parietal sites from 350 to 600 ms. Priming effects were seen at encoding stages, revealed by shorter latencies and smaller amplitudes of N170 for repeated stimuli, which did not differ depending on face type. Repeated faces yielded more positive amplitudes than new faces from 250 to 450 ms frontally and from 400 to 600 ms parietally. However, ERP differences revealed that the magnitude of this repetition effect was smaller for negative and inverted than upright faces at 0-lag but not at 1-lag condition. Thus, face encoding and recognition processes were affected by inversion and contrast-reversal differently.

Is 2 + 2 = 4? Meta-analyses of brain areas needed for numbers and calculations

Most of us use numbers daily for counting, estimating quantities or formal mathematics, yet despite their importance our understanding of the brain correlates of these processes is still evolving. A neurofunctional model of mental arithmetic, proposed more than a decade ago, stimulated a substantial body of research in this area. Using quantitative meta-analyses of fMRI studies we identified brain regions concordant among studies that used number and calculation tasks. These tasks elicited activity in a set of common regions such as the inferior parietal lobule; however, the regions in which they differed were most notable, such as distinct areas of prefrontal cortices for specific arithmetic operations. Given the current knowledge, we propose an updated topographical brain atlas of mental arithmetic with improved interpretative power.

Eyes first! Eye processing develops before face processing in children

Faces and eyes are critical social stimuli which adults process with ease, but how this expertise develops is not yet understood. Neural changes associated with face and eye processing were investigated developmentally using ERPs (N170), in 128 subjects (4–15 year olds and adults). Stimuli included upright faces to assess configural processing, eyes and inverted faces to assess feature-based processing. N170 was present in the youngest children with similar patterns of face sensitivity seen in adults. Development of N170 to upright faces continued until adulthood, suggesting slow maturation of configural processing. In contrast, N170 was shorter latency and much larger to eyes than faces in children and was mature by 11 years, suggesting the early presence of an eye detector, with a rapid maturational course.

The Faces of Development: A Review of Early Face Processing over Childhood

The understanding of the adult proficiency in recognizing and extracting information from faces is still limited despite the number of studies over the last decade. Our knowledge on the development of these capacities is even more restricted, as only a handful of such studies exist. Here we present a combined reanalysis of four ERP studies in children from 4 to 15 years of age and adults (n = 424, across the studies), which investigated face processing in implicit and explicit tasks. We restricted these analyses to what was common across studies: early ERP components and upright face processing across all four studies and the inversion effect, investigated in three of the studies. These data demonstrated that processing faces implicates very rapid neural activity, even in young children at the P1 componentwith protracted age-related change in both P1 and N170, that were sensitive to the different task demands. Inversion produced latency and amplitude effects on the P1 from the youngest group, but on N170 only starting in mid childhood. These developmental data suggest that there are functionally different sources of the P1 and N170, related to the processing of different aspects of faces.

Face, eye and object early processing: what is the face specificity?

We investigated the human face specificity by comparing the effects of inversion and contrast reversal, two manipulations known to disrupt configural face processing, on human and ape faces, isolated eyes and objects, using event-related potentials. The face sensitive marker, N170, was shortest to human faces and delayed by inversion and contrast reversal for all categories and not only for human faces. Most importantly, N170 to inverted or contrast-reversed faces was not different from N170 to eyes that did not differ across manipulations. This suggests the disruption of facial configuration by these manipulations isolates the eye region from the face context, to which eye neurons respond. Our data suggest that (i) the inversion and contrast reversal effects on N170 latency are not specific to human faces and (ii) the similar increase of N170 amplitude by inversion and contrast reversal is unique to human faces and is driven by the eye region. Thus, while inversion and contrast reversal effects on N170 latency are not category-specific, their effects on amplitude are face-specific and reflect mainly the contribution of the eye region.

Review of neuroimaging in autism spectrum disorders: what have we learned and where we go from here

Autism spectrum disorder (ASD) refers to a syndrome of social communication deficits and repetitive behaviors or restrictive interests. It remains a behaviorally defined syndrome with no reliable biological markers. The goal of this review is to summarize the available neuroimaging data and examine their implication for our understanding of the neurobiology of ASD.Although there is variability in the literature on structural magnetic resonance literature (MRI), there is evidence of volume abnormalities in both grey and white matter, with a suggestion of some region-specific differences. Early brain overgrowth is probably the most replicated finding in a subgroup of people with ASD, and new techniques, such as cortical-thickness measurements and surface morphometry have begun to elucidate in more detail the patterns of abnormalities as they evolve with age, and are implicating specific neuroanatomical or neurodevelopmental processes. Functional MRI and diffusion tensor imaging techniques suggest that such volume abnormalities are associated with atypical functional and structural connectivity in the brain, and researchers have begun to use magnetic resonance spectroscopy (MRS) techniques to explore the neurochemical substrate of such abnormalities. The data from multiple imaging methods suggests that ASD is associated with an atypically connected brain. We now need to further clarify such atypicalities, and start interpreting them in the context of what we already know about typical neurodevelopmental processes including migration and organization of the cortex. Such an approach will allow us to relate imaging findings not only to behavior, but also to genes and their expression, which may be related to such processes, and to further our understanding of the nature of neurobiologic abnormalities in ASD.

Non-spatial attentional effects on P1

OBJECTIVE It has been suggested that P1, the earliest endogenous visual potential, is influenced primarily by spatial location. However, we have found that attention to non-spatial visual features can affect both the latency and amplitude of this component. METHODS A series of studies are reviewed, starting with 4 using simple geometric forms, and either serial presentation of single stimuli or presentation of stimulus arrays followed by two studies using natural complex images. RESULTS With simple stimuli, latency and amplitude effects are seen on the P1, but differ among the paradigms, depending on the demands of the task. The data further showed a facilitation effect and that binding occurs in parallel with single feature processing. For complex stimuli we found P1 shorter to faces than inverted faces, eyes or non-face stimuli, and larger to animal than non-animal pictures. The above effects were present in children as well as in adults. CONCLUSIONS These findings demonstrate that very early stages of processing can be modified by top-down attentional influences across a range of ages and experimental paradigms, concordant with visual processing models showing very rapid and dispersed activation with feedback at early cortical levels.

Tracking the development of the N1 from age 3 to adulthood: an examination of speech and non-speech stimuli

OBJECTIVES To examine developmental changes in the N1a, N1b and N1c evoked by a tone and a speech consonant (/da/). METHODS Subjects (n=70 for tones; n=69 for /da/) were grouped into 2 year intervals (age 3-16) and adults. They listened to a tone (2 kHz; 36 ms; 77 dB SL; ISI=600 ms; n=346) or a speech consonant /da/ (female voice recording; 7 ms VOT; 212 ms; 72 dB SL; ISI=600 ms; n=349) while watching a Disney((R)) screensaver. EEG was recorded from 26 electrodes referenced to Cz. An averaged reference was computed off-line. Amplitude and latency data were analyzed with repeated-measures ANOVAs for agexelectrode, and agexN1 component, respectively. RESULTS Left hemisphere N1a was mature before age 3 whereas the right hemisphere N1a matured around 7-8 years. The vertex N1b showed a parietal distribution which shifted anteriorly with age. The N1c showed age- and stimulus-related changes. The N1c measured over the left hemisphere matured earlier than the N1c over the right hemisphere. The N1c to /da/ matured earlier than that to tones. CONCLUSIONS Auditory processing undergoes steady and subtle developmental changes. These changes follow different maturational patterns depending on the type of stimuli. The evidence suggests earlier development of the left hemisphere and earlier development of the generators underlying speech processing.