A meta-analysis of event-related potential correlates of recognition memory

A longstanding question in memory research is whether recognition is supported by more than one mnemonic process. Dual-process models distinguish recollection of episodic detail from familiarity, while single-process models explain recognition in terms of one process that varies in strength. Dual process models have drawn support from findings that recollection and familiarity elicit distinct electroencephalographic event-related potentials (ERPs): a mid-frontal ERP effect that occurs at around 300-500 ms post-stimulus onset and is often larger for familiarity than recollection contrasts, and a parietal ERP effect that occurs at around 500-800 ms and is larger for recollection than familiarity contrasts. We sought to adjudicate between dual- and single-process models by investigating whether the dissociation between these two ERP effects is reliable over studies. We extracted effect sizes from 41 experiments that had used Remember-Know, source memory, and associative memory paradigms (1,000 participants). Meta-analysis revealed a strong interaction between ERP effect and mnemonic process of the form predicted by dual-process models. Although neither ERP effect was significantly process-selective taken alone, a moderator analysis revealed a larger mid-frontal effect for familiarity than recollection contrasts in studies using the Remember-Know paradigm. Mega-analysis of raw data from six studies further showed significant process-selectivity for both mid-frontal and parietal ERPs in the predicted time windows. On balance, the findings favor dual- over single-process theories of recognition memory, but point to a need to promote sharing of raw data.

More elaborate processing of own-race faces and less elaborate processing of other-race faces contribute to the other-race effect in face memory

Research suggests that own-race faces are naturally memorized in a more elaborate (e.g., many features of a face or the whole face) way, whereas other-race faces are memorized in a less elaborate (e.g., only selected features of the face) manner. Here, we tested if instructions for judgements about the whole face and a single facial feature modulated the other-race effect in face memory. White participants performed whole-face and single-feature tasks while memorizing White and Black faces for later recognition. Encoding instructions had a stronger impact on own-race than other-race faces. Whole-face instructions increased the other-race effect, whereas single-feature instructions decreased it. Own-race faces in the whole-face task demonstrated event-related potential (ERP) patterns of memory encoding comparable to previously observed natural memory encoding, suggesting naturally more elaborate encoding of own-race faces. ERPs of memory encoding for other-race faces were similar between task conditions and comparable to previously observed natural encoding patterns, suggesting naturally less elaborate encoding. No impact of the encoding tasks was found on ERPs related to memory retrieval, which may be an artefact of a perceptual task that does not enhance semantic details in memory. The current results indicate that some contributions to the other-race effect are more elaborate (more detailed) memory encoding for own-race faces and less elaborate (less detailed) memory encoding for other-race faces. This study also provides evidence for more malleability of own-race than other-race faces through task instructions, consistent with assumptions of perceptual learning theories of the other-race effect.

An Event-Related Potential Investigation of Early Visual Processing Deficits During Face Perception in Youth at Clinical High Risk for Psychosis

Impairments in early visual face perception are well documented in patients with schizophrenia. Specifically, event-related potential (ERP) research in patients with schizophrenia has demonstrated deficits in early sensory processing of stimulus properties (P1 component) and the structural encoding of faces (N170 component). However, it is not well understood if similar impairments are present in individuals at clinical high risk (CHR) for psychosis (ie, those in the putative prodromal stage of the illness). Thus, it is unknown if face perception deficits are the result of illness onset or are present in the high-risk period for the illness. The present study used the ERP technique to examine neural activation when viewing facial emotion expressions and objects in 44 CHR and 47 control adolescents and young adults (N = 91). P1 amplitude was similar across groups, indicating that early sensory processing impairments did not substantially contribute to face perception deficits in CHR youth. CHR youth exhibited reduced N170 amplitude compared to controls when viewing faces but not objects, implicating a specific deficit in the structural encoding of faces rather than a general perceptual deficit. Further, whereas controls demonstrated the expected face-selective N170 effect (ie, larger amplitude for faces than objects), CHR youth did not, which suggests that facial emotion expressions do not elicit the expected preferential perceptual processing for critical social information in individuals at CHR for psychosis. Together, these findings provide valuable information regarding the specific impairments contributing to face perception deficits in the high-risk period where treatment stands to aid in preventing illness progression.

Investigation of saliva, tongue swabs and buccal swabs as alternative specimen types to nasopharyngeal swabs for SARS-CoV-2 testing

Throughout the ongoing SARS-CoV-2 pandemic, the recommended sample type for initial diagnostic testing for SARS-CoV-2 infection has been a nasopharyngeal swab. Shortages in swabs and difficulties in obtaining nasopharyngeal swabs in certain patient groups has prompted research into alternative specimen types for the diagnosis of COVID-19. The aim of this study was to assess how ‘simply collected’ saliva along with tongue swabs and buccal swabs preformed as an alternative specimen type for SARS-CoV-2 detection. It was observed that saliva samples allowed for the detection of 85.3% of positive patients, tongue swabs allowed for the detection of 67.6% of positive patients and buccal swabs allowed for detection of 20.8% of positive patients, when compared to nasopharyngeal swabs. From this data, it could be concluded that using simple saliva collection can provide a less invasive and reliable alternative method for the detection of SARS-CoV2 particularly in those patients where invasive sampling is difficult and where regular repeat testing is required.

Dissociations between performance and visual fixations after subordinate- and basic-level training with novel objects

Previous work suggests that subordinate-level object training improves exemplar-level perceptual discrimination over basic-level training. However, the extent to which visual fixation strategies and the use of visual features, such as color and spatial frequency (SF), change with improved discrimination was not previously known. In the current study, adults (n = 24) completed 6 days of training with 2 families of computer-generated novel objects. Participants were trained to identify one object family at the subordinate level and the other object family at the basic level. Before and after training, discrimination accuracy and visual fixations were measured for trained and untrained exemplars. To examine the impact of training on visual feature use, image color and SF were manipulated and tested before and after training. Discrimination accuracy increased for the object family trained at the subordinate-level, but not for the family trained at the basic level. This increase was seen for all image manipulations (color, SF) and generalized to untrained exemplars within the trained family. Both subordinate- and basic-level training increased average fixation duration and saccadic amplitude and decreased the number of total fixations. Collectively, these results suggest a dissociation between discrimination accuracy, indicative of recognition, and the associated pattern of changes present for visual fixations.

Energy-Period Profiles of Brain Networks in Group fMRI Resting-State Data: A Comparison of Empirical Mode Decomposition With the Short-Time Fourier Transform and the Discrete Wavelet Transform

Traditionally, functional networks in resting-state data were investigated with linear Fourier and wavelet-related methods to characterize their frequency content by relying on pre-specified frequency bands. In this study, Empirical Mode Decomposition (EMD), an adaptive time-frequency method, is used to investigate the naturally occurring frequency bands of resting-state data obtained by Group Independent Component Analysis. Specifically, energy-period profiles of Intrinsic Mode Functions (IMFs) obtained by EMD are created and compared for different resting-state networks. These profiles have a characteristic distribution for many resting-state networks and are related to the frequency content of each network. A comparison with the linear Short-Time Fourier Transform (STFT) and the Maximal Overlap Discrete Wavelet Transform (MODWT) shows that EMD provides a more frequency-adaptive representation of different types of resting-state networks. Clustering of resting-state networks based on the energy-period profiles leads to clusters of resting-state networks that have a monotone relationship with frequency and energy. This relationship is strongest with EMD, intermediate with MODWT, and weakest with STFT. The identification of these relationships suggests that EMD has significant advantages in characterizing brain networks compared to STFT and MODWT. In a clinical application to early Parkinson's disease (PD) vs. normal controls (NC), energy and period content were studied for several common resting-state networks. Compared to STFT and MODWT, EMD showed the largest differences in energy and period between PD and NC subjects. Using a support vector machine, EMD achieved the highest prediction accuracy in classifying NC and PD subjects among STFT, MODWT, and EMD.

Bird expertise does not increase motion sensitivity to bird flight motion

While motion information is important for the early stages of vision, it also contributes to later stages of object recognition. For example, human observers can detect the presence of a human, judge its actions, and judge its gender and identity simply based on motion cues conveyed in a point-light display. Here we examined whether object expertise enhances the observer's sensitivity to its characteristic movement. Bird experts and novices were shown point-light displays of upright and inverted birds in flight, or upright and inverted human walkers, and asked to discriminate them from spatially scrambled point-light displays of the same stimuli. While the spatially scrambled stimuli retained the local motion of each dot of the moving objects, it disrupted the global percept of the object in motion. To estimate a detection threshold in each object domain, we systematically varied the number of noise dots in which the stimuli were embedded using an adaptive staircase approach. Contrary to our predictions, the experts did not show disproportionately higher sensitivity to bird motion, and both groups showed no inversion cost. However, consistent with previous work showing a robust inversion effect for human motion, both groups were more sensitive to upright human walkers than their inverted counterparts. Thus, the result suggests that real-world experience in the bird domain has little to no influence on the sensitivity to bird motion and that birds do not show the typical inversion effect seen with humans and other terrestrial movement.

Acute effects of naturalistic THC vs. CBD use on recognition memory: a preliminary study

The ratio of ∆9-tetrahydrocannabinol (THC) to cannabidiol (CBD) varies widely across cannabis strains. CBD has opposite effects to THC on a variety of cognitive functions, including acute THC-induced memory impairments. However, additional data are needed, especially under naturalistic conditions with higher potency forms of cannabis, commonly available in legal markets. The goal of this study was to collect preliminary data on the acute effects of different THC:CBD ratios on memory testing in a brief verbal recognition task under naturalistic conditions, using legal-market Colorado dispensary products. Thirty-two regular cannabis users consumed cannabis of differing THC and CBD levels purchased from a dispensary and were assessed via blood draw and a verbal recognition memory test both before (pretest) and after (posttest) ad libitum home administration in a mobile laboratory. Memory accuracy decreased as post-use THC blood levels increased (n = 29), whereas performance showed no relationship to CBD blood levels. When controlling for post-use THC blood levels as a covariate, participants using primarily THC-based strains showed significantly worse memory accuracy post-use, whereas subjects using strains containing both THC and CBD showed no differences between pre- and post-use memory performance. Using a brief and sensitive verbal recognition task, our study demonstrated that naturalistic, acute THC use impairs memory in a dose dependent manner, whereas the combination of CBD and THC was not associated with impairment.

The role of claw color in species recognition and mate choice in a fiddler crab

Abstract

Many animal signals are brightly colored and convey information about species identity as well as information about individual conspecifics. Colorful bird and lizard signals have received much attention, and many studies have related specific spectral properties of these signals to variation in mating success and territory defense. Far less attention has been given to invertebrates even though there are spectacularly colorful species. The enlarged claw of the male banana fiddler crab Austruca mjoebergi, for example, is bright yellow and contrasts vividly against the mudflat substrate. It is used in waving displays to attract females and in male territory defense and combat. Claw color varies among males in the degree of “yellowness,” ranging very pale yellow to orange. In this study, we examined female responses to claw color variation in two-choice tests using robotic crabs. We found that although females strongly discriminate against colors that fall outside the natural range of intensity, hue, and chroma, they show no consistent preferences for different claw colors within the natural range, and no single component of claw color (hue, chroma, or intensity) independently affected female choices. Using three-choice tests, we also showed that female preferences induce stabilizing selection on male claw color. We conclude that, although claw color is sufficient to facilitate species recognition, it is unlikely to be used in intraspecific mate choice to provide information about male quality.

Significance statement

Fiddler crabs are often brightly colored, are visually orientated animals, and have a highly complex social system. Despite this, there are few studies that have looked at the role of color in species recognition and mate choice in these animals. In this study, we use robotic crabs with painted claws to determine the role of claw color in species recognition and mate choice in the banana fiddler crab, Austruca mjoebergi. We found that color is important in conspecific mate recognition but the variation among males in claw “yellowness” is unlikely to be used by females in intraspecific mate choice decisions.

A robust deep neural network for denoising task-based fMRI data: An application to working memory and episodic memory

In this study, a deep neural network (DNN) is proposed to reduce the noise in task-based fMRI data without explicitly modeling noise. The DNN artificial neural network consists of one temporal convolutional layer, one long short-term memory (LSTM) layer, one time-distributed fully-connected layer, and one unconventional selection layer in sequential order. The LSTM layer takes not only the current time point but also what was perceived in a previous time point as its input to characterize the temporal autocorrelation of fMRI data. The fully-connected layer weights the output of the LSTM layer, and the output denoised fMRI time series is selected by the selection layer. Assuming that task-related neural response is limited to gray matter, the model parameters in the DNN network are optimized by maximizing the correlation difference between gray matter voxels and white matter or ventricular cerebrospinal fluid voxels. Instead of targeting a particular noise source, the proposed neural network takes advantage of the task design matrix to better extract task-related signal in fMRI data. The DNN network, along with other traditional denoising techniques, has been applied on simulated data, working memory task fMRI data acquired from a cohort of healthy subjects and episodic memory task fMRI data acquired from a small set of healthy elderly subjects. Qualitative and quantitative measurements were used to evaluate the performance of different denoising techniques. In the simulation, DNN improves fMRI activation detection and also adapts to varying hemodynamic response functions across different brain regions. DNN efficiently reduces physiological noise and generates more homogeneous task-response correlation maps in real data.

Multivariate group-level analysis for task fMRI data with canonical correlation analysis

Task-based functional Magnetic Resonance Imaging (fMRI) has been widely used to determine population-based brain activations for cognitive tasks. Popular group-level analysis in fMRI is based on the general linear model and constitutes a univariate method. However, univariate methods are known to suffer from low sensitivity for a given specificity because the spatial covariance structure at each voxel is not taken entirely into account. In this study, a spatially constrained local multivariate model is introduced for group-level analysis to improve sensitivity at a given specificity for activation detection. The proposed model is formulated in terms of a multivariate constrained optimization problem based on the maximum log likelihood method and solved efficiently with numerical optimization techniques. Both simulated data mimicking real fMRI time series at multiple noise fractions and real fMRI episodic memory data have been used to evaluate the performance of the proposed method. For simulated data, the area under the receiver operating characteristic curves in detecting group activations increases for the subject and group level multivariate method by 20%, as compared to the univariate method. Results from real fMRI data indicate a significant increase in group-level activation detection, particularly in hippocampus, para-hippocampal area and nearby medial temporal lobe regions with the proposed method.

Prophylactic closed-incision negative-pressure wound therapy is associated with decreased surgical site infection in high-risk colorectal surgery laparotomy wounds

AIM

Surgical site infection in colorectal surgery is associated with significant healthcare costs, which may be reduced by using a closed-incision negative-pressure therapy device. The aim of this study was to assess the impact of closed-incision negative-pressure therapy on the incidence of surgical site infection.

METHOD

In this retrospective cohort study we evaluated all patients who had undergone high-risk open colorectal surgery at a single tertiary care centre from 2012 to 2016. We compared the incidence of surgical site infection between those receiving standard postoperative wound care between 2012 and 2014 and those receiving closed-incision negative-pressure therapy via a customizable device (Prevena Incision Management System, KCI, an Acelity company, San Antonio, Texas, USA) between 2014 and 2016. A validated surgical site infection risk score was used to create a 1:1 matched cohort subset.

RESULTS

Negative pressure therapy was used in 77 patients and compared with 238 controls. Negative pressure patients were more likely to have a stoma (92% vs 48%, P < 0.01) and to be smokers (33% vs 15%, P < 0.01). Surgical site infection was higher in control patients (15%, n = 35/238) compared with negative pressure patients (7%, n = 5/77) (P = 0.05). On regression analysis, negative pressure therapy was associated with decreased surgical site infection (OR 0.27; 95% CI 0.09-0.78). These differences persisted in the matched analysis.

CONCLUSION

Negative pressure therapy was associated with decreased surgical site infection. Negative pressure therapy offers significant potential for quality improvement.

Single-Trial EEG Analysis Predicts Memory Retrieval and Reveals Source-Dependent Differences

We used pattern classifiers to extract features related to recognition memory retrieval from the temporal information in single-trial electroencephalography (EEG) data during attempted memory retrieval. Two-class classification was conducted on correctly remembered trials with accurate context (or source) judgments vs. correctly rejected trials. The average accuracy for datasets recorded in a single session was 61% while the average accuracy for datasets recorded in two separate sessions was 56%. To further understand the basis of the classifier’s performance, two other pattern classifiers were trained on different pairs of behavioral conditions. The first of these was designed to use information related to remembering the item and the second to use information related to remembering the contextual information (or source) about the item. Mollison and Curran (2012) had earlier shown that subjects’ familiarity judgments contributed to improved memory of spatial contextual information but not of extrinsic associated color information. These behavioral results were similarly reflected in the event-related potential (ERP) known as the FN400 (an early frontal effect relating to familiarity) which revealed differences between correct and incorrect context memories in the spatial but not color conditions. In our analyses we show that a classifier designed to distinguish between correct and incorrect context memories, more strongly involves early activity (400–500 ms) over the frontal channels for the location distinctions, than for the extrinsic color associations. In contrast, the classifier designed to classify memory for the item (without memory for the context), had more frontal channel involvement for the color associated experiments than for the spatial experiments. Taken together these results argue that location may be bound more tightly with the item than an extrinsic color association. The multivariate classification approach also showed that trial-by-trial variation in EEG corresponding to these ERP components were predictive of subjects’ behavioral responses. Additionally, the multivariate classification approach enabled analysis of error conditions that did not have sufficient trials for standard ERP analyses. These results suggested that false alarms were primarily attributable to item memory (as opposed to memory of associated context), as commonly predicted, but with little previous corroborating EEG evidence.

3D spatially-adaptive canonical correlation analysis: Local and global methods

Local spatially-adaptive canonical correlation analysis (local CCA) with spatial constraints has been introduced to fMRI multivariate analysis for improved modeling of activation patterns. However, current algorithms require complicated spatial constraints that have only been applied to 2D local neighborhoods because the computational time would be exponentially increased if the same method is applied to 3D spatial neighborhoods. In this study, an efficient and accurate line search sequential quadratic programming (SQP) algorithm has been developed to efficiently solve the 3D local CCA problem with spatial constraints. In addition, a spatially-adaptive kernel CCA (KCCA) method is proposed to increase accuracy of fMRI activation maps. With oriented 3D spatial filters anisotropic shapes can be estimated during the KCCA analysis of fMRI time courses. These filters are orientation-adaptive leading to rotational invariance to better match arbitrary oriented fMRI activation patterns, resulting in improved sensitivity of activation detection while significantly reducing spatial blurring artifacts. The kernel method in its basic form does not require any spatial constraints and analyzes the whole-brain fMRI time series to construct an activation map. Finally, we have developed a penalized kernel CCA model that involves spatial low-pass filter constraints to increase the specificity of the method. The kernel CCA methods are compared with the standard univariate method and with two different local CCA methods that were solved by the SQP algorithm. Results show that SQP is the most efficient algorithm to solve the local constrained CCA problem, and the proposed kernel CCA methods outperformed univariate and local CCA methods in detecting activations for both simulated and real fMRI episodic memory data.

Neural and behavioral effects of subordinate-level training of novel objects across manipulations of color and spatial frequency

Perceptual expertise is marked by subordinate-level recognition of objects in the expert domain. In this study, participants learned one family of full-color, artificial objects at the subordinate (species) level and another family at the basic (family) level. Discrimination of trained and untrained exemplars was tested before and after training across several image manipulations [full-color, grayscale, low spatial frequency (LSF) and high spatial frequency (HSF)] while event-related potentials (ERPs) were recorded. Regardless of image manipulation, discrimination (indexed by d') of trained and of untrained exemplars was enhanced after subordinate-level training, but not after basic-level training. Enhanced discrimination after subordinate-level training generalized to untrained exemplars and to grayscale images and images in which LSF or HSF information was removed. After training, the N170 and N250, recorded over occipital and occipitotemporal brain regions, were both more enhanced after subordinate-level training than after basic-level training. However, the topographic distribution of enhanced responses differed across components. The N170 latency predicted reaction time after both basic-level training and subordinate-level training, highlighting an association between behavioral and neural responses. These findings further elucidate the role of the N170 and N250 as ERP indices of subordinate-level expert object processing and demonstrate how low-level manipulations of color and spatial frequency impact behavior and the N170 and N250 components independent of training or expertise.

MAO-A Phenotype Effects Response Sensitivity and the Parietal Old/New Effect during Recognition Memory

A critical problem for developing personalized treatment plans for cognitive disruptions is the lack of understanding how individual differences influence cognition. Recognition memory is one cognitive ability that varies from person to person and that variation may be related to different genetic phenotypes. One gene that may impact recognition memory is the monoamine oxidase A gene (MAO-A), which influences the transcription rate of MAO-A. Examination of how MAO-A phenotypes impact behavioral and event-related potentials (ERPs) correlates of recognition memory may help explain individual differences in recognition memory performance. Therefore, the current study uses electroencephalography (EEG) in combination with genetic phenotyping of the MAO-A gene to determine how well-characterized ERP components of recognition memory, the early frontal old/new effect, left parietal old/new effect, late frontal old/new effect, and the late posterior negativity (LPN) are impacted by MAO-A phenotype during item and source memory. Our results show that individuals with the MAO-A phenotype leading to increased transcription have lower response sensitivity during both item and source memory. Additionally, during item memory the left parietal old/new effect is not present due to increased ERP amplitude for correct rejections. The results suggest that MAO-A phenotype changes EEG correlates of recognition memory and influences how well individuals differentiate between old and new items.

Individual differences in EEG correlates of recognition memory due to DAT polymorphisms

INTRODUCTION

Although previous research suggests that genetic variation in dopaminergic genes may affect recognition memory, the role dopamine transporter expression may have on the behavioral and EEG correlates of recognition memory has not been well established.

OBJECTIVES

The study aims to reveal how individual differences in dopaminergic functioning due to genetic variations in the dopamine transporter gene influences behavioral and EEG correlates of recognition memory.

METHODS

Fifty-eight participants performed an item recognition task. Participants were asked to retrieve 200 previously presented words while brain activity was recorded with EEG. Regions of interest were established in scalp locations associated with recognition memory. Mean ERP amplitudes and event-related spectral perturbations when correctly remembering old items (hits) and recognizing new items (correct rejections) were compared as a function of dopamine transporter group.

RESULTS

Participants in the dopamine transporter group that codes for increased dopamine transporter expression (10/10 homozygotes) display slower reaction times compared to participants in the dopamine transporter group associated with the expression of fewer dopamine transporters (9R-carriers). 10/10 homozygotes further displayed differences in ERP and oscillatory activity compared to 9R-carriers. 10/10 homozygotes fail to display the left parietal old/new effect, an ERP signature of recognition memory associated with the amount of information retrieved. 10/10 homozygotes also displayed greater decreases of alpha and beta oscillatory activity during item memory retrieval compared to 9R-carriers.

CONCLUSION

Compared to 9R-carriers, 10/10 homozygotes display slower hit and correct rejection reaction times, an absence of the left parietal old/new effect, and greater decreases in alpha and beta oscillatory activity during recognition memory. These results suggest that dopamine transporter polymorphisms influence recognition memory.

The effects of Hurricane Sandy on trauma center admissions

BACKGROUND

Hurricane Sandy was a particularly unusual storm with regard to both size and location of landfall. The storm landed in New Jersey, which is unusual for a tropical storm of such scale, and created hazardous conditions which caused injury to residents during the storm and in the months following. This study aims to describe differences in trauma center admissions and patterns of injury during this time period when compared to a period with no such storm.

METHODS

Data were collected for this study from patients who were admitted to the trauma center at Morristown Medical Center during Hurricane Sandy or the ensuing cleanup efforts (patients admitted between 29 October 2012 and 27 December 2012) as well as a control group consisting of all patients admitted to the trauma center between 29 October 2013 and 27 December 2013. Patient information was collected to compare the admissions of the trauma center during the period of the storm and cleanup to the control period.

RESULTS

A total of 419 cases were identified in the storm and cleanup period. 427 were identified for the control. Striking injuries were more common in the storm and cleanup group by 266.7% (p = 0.0107); cuts were more common by 650.8% (p = 0.0044). Medical records indicate that many of these injuries were caused by Hurricane Sandy. Self-inflicted injuries were more common by 301.3% (p = 0.0294). There were no significant differences in the total number of patients, mortality, or injury severity score between the two cohorts.

CONCLUSION

The data we have collected show that the conditions caused by Hurricane Sandy and the following cleanup had a significant effect on injury patterns, with more patients having been injured by being struck by falling or thrown objects, cut while using tools, or causing self-inflicted injuries. These changes, particularly during the cleanup period, are indicative of environmental changes following the storm which increase these risks of injury.

A family of locally constrained CCA models for detecting activation patterns in fMRI

Canonical correlation analysis (CCA) has been used in Functional Magnetic Resonance Imaging (fMRI) for improved detection of activation by incorporating time series from multiple voxels in a local neighborhood. To improve the specificity of local CCA methods, spatial constraints were previously proposed. In this study, constraints are generalized by introducing a family model of spatial constraints for CCA to further increase both sensitivity and specificity in fMRI activation detection. The proposed locally-constrained CCA (cCCA) model is formulated in terms of a multivariate constrained optimization problem and solved efficiently with numerical optimization techniques. To evaluate the performance of this cCCA model, simulated data are generated with a Signal-To-Noise Ratio of 0.25, which is realistic to the noise level contained in episodic memory fMRI data. Receiver operating characteristic (ROC) methods are used to compare the performance of different models. The cCCA model with optimum parameters (called optimum-cCCA) obtains the largest area under the ROC curve. Furthermore, a novel validation method is proposed to validate the selected optimum-cCCA parameters based on ROC from simulated data and real fMRI data. Results for optimum-cCCA are then compared with conventional fMRI analysis methods using data from an episodic memory task. Wavelet-resampled resting-state data are used to obtain the null distribution of activation. For simulated data, accuracy in detecting activation increases for the optimum-cCCA model by about 43% as compared to the single voxel analysis with comparable Gaussian smoothing. Results from the real fMRI data set indicate a significant increase in activation detection, particularly in hippocampus, para-hippocampal area and nearby medial temporal lobe regions with the proposed method.

A Meta-analytic Review of Auditory Event-Related Potential Components as Endophenotypes for Schizophrenia: Perspectives From First-Degree Relatives

INTRODUCTION

As endophenotypes bridge the gap between genetics and phenotypic disease expression, identifying reliable markers is important for fostering understanding of pathophysiology. The present aim was to conduct current meta-analyses of 3 key auditory event-related potential (ERP) components that have been held as potential endophenotypes for schizophrenia: P50, P300 amplitude and latency, and mismatch negativity (MMN), reflective of sensory gating, attention and classification speed, and perceptual discrimination ability, respectively. In order to assess endophenotype viability, these components were examined in unaffected relatives of patients with schizophrenia and healthy controls.

METHODS

Effect sizes (ES) were examined between relatives and controls for P50 suppression (10 studies, n = 360 relatives, 473 controls), P300 amplitude (20 studies, n = 868 relatives, 961 controls), P300 latency (17 studies, n = 674 relatives, 792 controls), and MMN (11 studies, n = 377 relatives, 552 controls).

RESULTS

Reliable differences in P50 suppression (ES = 0.86, P < .001), P300 amplitude (ES = -0.52, P < .001), and P300 latency (ES = 0.44, P < .05) were found between unaffected relatives and controls. A trend was found between relatives and controls for MMN (ES = 0.21, P = 0.06), and the use of extraneous channels was found to be a significant moderator (P = 0.01). When MMN was analyzed using frontocentral channel Fz, a significant difference was found (ES = 0.26, P < 0.01).

DISCUSSION

The results indicate that P50 suppression, P300 amplitude and P300 latency, and MMN may serve as viable endophenotypes for schizophrenia.

FN400 and LPC memory effects for concrete and abstract words

According to dual-process models, recognition memory depends on two neurocognitive mechanisms: familiarity, which has been linked to the frontal N400 (FN400) effect in studies using ERPs, and recollection, which is reflected by changes in the late positive complex (LPC). Recently, there has been some debate over the relationship between FN400 familiarity effects and N400 semantic effects. According to one view, these effects are one and the same. Proponents of this view have suggested that the frontal distribution of the FN400 could be due to stimulus concreteness: recognition memory experiments commonly use highly imageable or concrete words (or pictures), which elicit semantic ERPs with a frontal distribution. In the present study, we tested this claim using a recognition memory paradigm in which subjects memorized concrete and abstract nouns; half of the words changed font color between study and test. FN400 and LPC old/new effects were observed for abstract as well as concrete words, and were stronger over right hemisphere electrodes for concrete words. However, there was no difference in anteriority of the FN400 effect for the two word types. These findings challenge the notion that the frontal distribution of the FN400 old/new effect is fully explained by stimulus concreteness.

Scaling the Episodic Familiarities of Pictures and Words

Most current memory theories assume that judgments of past occurrence are based on a unidimensional familiarity signal In a test of this hypothesis, subjects studied mixed lists of pictures and words that occurred up to three times each They then were given two tests a forced-choice frequency discrimination test including all pairs of conditions (e g, picture seen twice vs word never seen) and a numerical frequency judgment test on individual items Forced-choice proportions for all pairings (picture-picture, word-word, and picture-word) were well fit by a one-dimensional scaling solution, suggesting a common basis of recognition and frequency judgments for both pictures and words Both forced-choice and numerical judgment data indicated that familiarities of pictures started lower than those of words but increased more rapidly with repetition Results are discussed in connection with the distinction between familiarity and recall, and the possible role of rescaling in the mirror effect

The Similarity of Brain Activity Associated with True and False Recognition Memory Depends On Test Format

Event-related potentials (ERPs) were compared for correct recognitions of previously presented words and false recognitions of associatively related, nonpresented words (lures) When the test items were presented blocked by test type (old, new, lure), waveforms for old and lure items were different, especially at frontal and left parietal electrode sites, consistent with previous positron emission tomography (PET) data (Schacter, Reiman, et al, 1996) When the test format randomly intermixed the types of items, waveforms for old and lure items were more similar We suggest that test format affects the type of processing subjects engage in, consistent with expectations from the source-monitoring framework (Johnson, Hashtroudi, & Lindsay, 1993) These results also indicate that brain activity as assessed by neuroimaging designs requiring blocked presentation of trials (e.g., PET) do not necessarily reflect the brain activity that occurs in cognitive-behavioral paradigms, in which types of test trials are typically intermixed

The Training and Transfer of Real-World Perceptual Expertise

A hallmark of perceptual expertise is that experts classify objects at a more specific, subordinate level of abstraction than novices. To what extent does subordinate-level learning contribute to the transfer of perceptual expertise to novel exemplars and novel categories? In this study, participants learned to classify 10 varieties of wading birds and 10 varieties of owls at either the subordinate, species (e.g., “great blue crown heron,” “eastern screech owl”) or the family (“wading bird,” “owl”) level of abstraction. During training, the amount of visual exposure was equated such that participants received an equal number of learning trials for wading birds and owls. Pre- and posttraining performance was measured in a same/different discrimination task in which participants judged whether pairs of bird stimuli belonged to the same or different species. Participants trained in species-level discrimination demonstrated greater transfer to novel exemplars and novel species categories than participants trained in family-level discrimination. These findings suggest that perceptual categorization, not perceptual exposure per se, is important for the development and generalization of visual expertise.

Separating the FN400 and N400 potentials across recognition memory experiments

There is a growing debate as to whether frontally distributed FN400 potentials reflect familiarity-based recognition or are functionally identical to centro-parietal N400 reflecting semantic processing. We conducted two experiments in which event-related potentials (ERPs) associated with semantic priming and recognition were recorded, either when priming was embedded within a recognition test (Experiment 1), or when these two phases were separated (Experiment 2). In Experiment 1, we observed 300-500 ms differences between primed and unprimed old words as well as differences between old and new primed words, but these two effects did not differ topographically and both showed midline central maxima. In Experiment 2, the N400 for priming was recorded exclusively during encoding and again showed a midline central distribution. The ERP component of recognition was only found for unrelated words (not primed previously during encoding), and also showed a midline central maximum, but, in addition, was present in the left frontal area of the scalp. Conversely, the priming effect was absent in the left frontal cluster. This pattern of results indicate that FN400 and N400 potentials share similar neural generators; but when priming and recognition are not confounded, these potentials do not entirely overlap in terms of topographical distribution and presumably reflect functionally distinct processes.

Deficits in Early Stages of Face Processing in Schizophrenia: A Systematic Review of the P100 Component

INTRODUCTION

Schizophrenia is associated with deficits in face and affect recognition, which contribute to broader social functioning deficits. The present aim was to conduct a meta-analysis of early face processing in schizophrenia, as indexed by the P100 event-related potential component.

METHODS

Twelve studies (n = 328 patients with schizophrenia, n = 330 healthy controls) of the P100 component during face processing were evaluated by calculating Cohen's d for each study and overall weighted mean effect size (ES). In additional exploratory analyses, moderating influences of method and design were investigated, and the P100 component during face processing was evaluated based on valence: 5 studies (n = 225 patients, n = 225 controls) included neutral stimuli, 5 studies (n = 225 patients, n = 225 controls) included happy stimuli, and 4 studies (n = 209 patients, n = 209 controls) included fearful stimuli.

RESULTS

The amplitude of the P100 to face stimuli was smaller in patients relative to controls (ES = .41, P < .01). Methodological or design differences did not account for heterogeneity in ES. When split by valence, results indicate smaller P100 in patients relative to control subjects in response to neutral (ES = .32, P < .001) and happy (ES = .21, P < .05) stimuli, whereas there was no difference in response to fearful faces (ES = .09, P > .05).

DISCUSSION

The results indicate that P100 amplitude in response to faces is smaller in patients with schizophrenia, showing that socially relevant visual processing deficits begin earlier in processing than previously suggested. Additionally, the exploratory analyses suggest emotional specificity in these deficits. Ramifications for our understanding of face processing deficits and treatment development are discussed.

The role of spatial frequency in expert object recognition

Novices recognize objects at the basic-category level (e.g., dog, chair, and bird) at which identification is based on the global form of the objects (Rosch, Mervis, Gray, Johnson, & Boyes-Braem, 1976). In contrast, experts recognize objects within their domain of expertise at the subordinate level (e.g., Sparrow or Finch) for which the internal object information may play an important role in identification (Tanaka & Taylor, 1991). To investigate whether expert recognition relies on internal object information, we band-pass filtered bird images over a range of spatial frequencies (SF) and then masked the filtered image to preserve its global form. In Experiment 1, bird experts categorized common birds at the family level (e.g., Robin or Sparrow) more quickly and more accurately than novices. Both experts and novices were more accurate when bird images contained the internal information represented by a middle range of SFs, and this finding was characterized by a quadratic function in which accuracy decreased toward each end of the SF spectrum. However, the experts, but not the novices, showed a similar quadratic relationship between response times and SF range. In Experiment 2, experts categorized Warblers and Finches at the more specific, species level (e.g., Wilson's Warbler or House Finch). Recognition was again fastest and most accurate for images filtered in the middle range of SFs. Collectively, these results indicate that a midrange of SFs contain crucial information for subordinate recognition, and that extensive perceptual experience can influence the efficiency with which this information is utilized. (PsycINFO Database Record

Genetic variation in the serotonin transporter gene influences ERP old/new effects during recognition memory

Recognition memory is defined as the ability to recognize a previously encountered stimulus and has been associated with spatially and temporally distinct event-related potentials (ERPs). Allelic variations of the serotonin transporter gene (SLC6A4) have recently been shown to impact memory performance. Common variants of the serotonin transporter-linked polymorphic region (5HTTLPR) of the SLC6A4 gene result in long (l) and short (s) allelic variants with carriers of the s allele having lowered transcriptional efficiency. Thus, the current study examines the effects polymorphisms of the SLC6A4 gene have on performance and ERP amplitudes commonly associated with recognition memory. Electroencephalogram (EEG), genetic, and behavioral data were collected from sixty participants as they performed an item and source memory recognition task. In both tasks, participants studied and encoded 200 words, which were then mixed with 200 new words during retrieval. Participants were monitored with EEG during the retrieval portion of each memory task. EEG electrodes were grouped into four ROIs, left anterior superior, right anterior superior, left posterior superior, and right posterior superior. ERP mean amplitudes during hits in the item and source memory task were compared to correctly recognizing new items (correct rejections). Results show that s-carriers have decreased mean hit amplitudes in both the right anterior superior ROI 1000-1500ms post stimulus during the source memory task and the left anterior superior ROI 300-500ms post stimulus during the item memory task. These results suggest that individual differences due to genetic variation of the serotonin transporter gene influences recognition memory.

Metacognitive processes in executive control development: the case of reactive and proactive control

Young children engage cognitive control reactively in response to events, rather than proactively preparing for events. Such limitations in executive control have been explained in terms of fundamental constraints on children's cognitive capacities. Alternatively, young children might be capable of proactive control but differ from older children in their metacognitive decisions regarding when to engage proactive control. We examined these possibilities in three conditions of a task-switching paradigm, varying in whether task cues were available before or after target onset. RTs, ERPs, and pupil dilation showed that 5-year-olds did engage in advance preparation, a critical aspect of proactive control, but only when reactive control was made more difficult, whereas 10-year-olds engaged in proactive control whenever possible. These findings highlight metacognitive processes in children's cognitive control, an understudied aspect of executive control development.

Familiarity and recollection in heuristic decision making

Heuristics involve the ability to utilize memory to make quick judgments by exploiting fundamental cognitive abilities. In the current study we investigated the memory processes that contribute to the recognition heuristic and the fluency heuristic, which are both presumed to capitalize on the byproducts of memory to make quick decisions. In Experiment 1, we used a city-size comparison task while recording event-related potentials (ERPs) to investigate the potential contributions of familiarity and recollection to the 2 heuristics. ERPs were markedly different for recognition heuristic-based decisions and fluency heuristic-based decisions, suggesting a role for familiarity in the recognition heuristic and recollection in the fluency heuristic. In Experiment 2, we coupled the same city-size comparison task with measures of subjective preexperimental memory for each stimulus in the task. Although previous literature suggests the fluency heuristic relies on recognition speed alone, our results suggest differential contributions of recognition speed and recollected knowledge to these decisions, whereas the recognition heuristic relies on familiarity. Based on these results, we created a new theoretical framework that explains decisions attributed to both heuristics based on the underlying memory associated with the choice options.

Sequential effects in response time reveal learning mechanisms and event representations

Binary choice tasks, such as 2-alternative forced choice, show a complex yet consistent pattern of sequential effects, whereby responses and response times depend on the detailed pattern of prior stimuli going back at least 5 trials. We show this pattern is well explained by simultaneous incremental learning of 2 simple statistics of the trial sequence: the base rate and the repetition rate. Both statistics are learned by the same basic associative mechanism, but they contribute different patterns of sequential effects because they entail different representations of the trial sequence. Subtler aspects of the data that are not explained by these 2 learning processes alone are explained by their interaction, via learning from joint error correction. Specifically, the cue-competition mechanism that has explained classic findings in animal learning (e.g., blocking) appears to operate on learning of sequence statistics. We also find that learning of the base rate and repetition rate are dissociated into response and stimulus processing, respectively, as indicated by event-related potentials, manipulations of stimulus discriminability, and reanalysis of past experiments that eliminated stimuli or prior responses. Thus, sequential effects in these tasks appear to be driven by learning the response base rate and the stimulus repetition rate. Connections are discussed between these findings and previous research attempting to separate stimulus- and response-based sequential effects, and research using sequential effects to determine mental representations. We conclude that sequential effects offer a powerful means for uncovering representations and learning mechanisms.

Classification aided analysis of oscillatory signatures in controlled retrieval

Control processes are critical for both facilitating and suppressing memory retrieval, but these processes are not well understood. The current work, inspired by a similar fMRI design (Detre et al., in press), used a modified Think/No-Think(TNT) paradigm to investigate the neural signatures of volition over enhancing and suppressing memory retrieval. Previous studies have shown memory enhancement when well-learned stimulus pairs are restudied in cued recall ("Recall or think of studied pair item"), and degradation when restudied with cued suppression ("Avoid thinking of studied pair item"). We used category-based (faces vs. scenes) multivariate classification of electroencephalography signals to determine if individual target items were successfully retrieved or suppressed. A logistic regression based on classifier output determined that retrieval activation during the cued recall/suppression period was a predictor for subsequent memory. Labeling trials with this internal measure, as opposed to their nominal Think vs. No-Think condition, revealed the classic TNT pattern of enhanced memory for successful cued-retrieval and degraded memory for cued-suppression. This classification process enabled a more selective investigation into the time-frequency signatures of control over retrieval. Comparing controlled retrieval vs. controlled suppression, results showed more prominent Theta oscillations (3 to 8 Hz) in controlled retrieval. Beta oscillations (12 to 30 Hz) were involved in high levels of both controlled retrieval and suppression, suggesting it may have a more general control-related role. These results suggest unique roles for these frequency bands in retrieval processes.