[Herpesvirus infections and immunological disturbances in patients with different stages of Alzheimer's disease]

INTRODUCTION

Alzheimer's disease (AD) is a multifactorial disease that leads to a progressive memory loss, visualspatial impairments, emotional and personality changes. As its earliest pre-dementia clinical stage, amnestic mild cognitive impairment syndrome (aMCI) is currently considered. Neuroinflammation plays a role in the development and progression of aMCI and the initial stage of AD, which can be supported by immunological disorders of a systemic character. Study of factors, including infections, influencing immune disorders and systemic inflammatory response in patients with aMCI, is of great importance.The aim of this study was to obtain new data on the possible role of herpesvirus infections in the development and progression of aMCI.

MATERIAL AND METHODS

100 patients with aMCI diagnosis, 45 patients with AD, 40 people from the control group were enrolled into the study. The frequency of DNA detection of herpesviruses (Epstein-Barr virus (EBV), human herpesviruses (HHV) type 6 and 7, cytomegalovirus (CMV)), the levels of viral load and the serological markers of herpesvirus infections (IgG to HHV-1, IgG to CMV) were determined. Immunological studies included an assessment of the level of the main pro-inflammatory and anti-inflammatory cytokines, and indicators of humoral and cellular immunity.

RESULTS

The study found an increased detection rate of EBV in saliva and a higher level of EBV DNA in saliva in aMCI and AD than in the control group. A relationship between the presence of active EBV infection and changes in immunological parameters in patients with aMCI were found. It was also discovered that the level of IgG antibodies to CMV is associated with the stage of AD.

DISCUSSION

The results indicate a possible role of EBV- and CMV-induced infections in the development of immunological changes which are typical for mild cognitive impairment and in the progression of AD.

CONCLUSION

The obtained data can be important for prognostic methods addressing AD development, including its pre-dementia stage, and for new approaches to individualized treatment and prevention.

A passive BCI for monitoring the intentionality of the gaze-based moving object selection

OBJECTIVE

The use of an electroencephalogram (EEG) anticipation-related component, the expectancy wave (E-wave), in brain-machine interaction was proposed more than 50 years ago. This possibility was not explored for decades, but recently it was shown that voluntary attempts to select items using eye fixations, but not spontaneous eye fixations, are accompanied by the E-wave. Thus, the use of the E-wave detection was proposed for the enhancement of gaze interaction technology, which has a strong need for a mean to decide if a gaze behaviour is voluntary or not. Here, we attempted at estimating whether this approach can be used in the context of moving object selection through smooth pursuit eye movements.

APPROACH

18 participants selected, one by one, items which moved on a computer screen, by gazing at them. In separate runs, the participants performed tasks not related to voluntary selection but also provoking smooth pursuit. A low-cost consumer-grade eye tracker was used for item selection.

MAIN RESULTS

A component resembling the E-wave was found in the averaged EEG segments time-locked to voluntary selection events of every participant. Linear discriminant analysis with shrinkage regularization (sLDA) classified the intentional and spontaneous smooth pursuit eye movements, using single-trial 300 ms long EEG segments, significantly above chance in eight participants. When the classifier output was averaged over ten subsequent data segments, median group ROC AUC of 0.75 was achieved.

SIGNIFICANCE

The results suggest the possible usefulness of the E-wave detection in the gaze-based selection of moving items, e.g., in video games. This technique might be more effective when trial data can be averaged, thus it could be considered for use in passive interfaces, for example, in estimating the degree of the user's involvement during gaze-based interaction.

Towards Semantic Brain Mapping Methodology Based on a Multidimensional Markup of Continuous Russian-Language Texts: an Attempt at Validation and Development

In the present study, we combine linguistic annotation of oral texts in Russian with the registration of BOLD signal in functional MRI experiments to determine how and where semantic categories are represented in the human brain. Using the same stimuli material, we also analyze the differences in cortical activation in three thematic domains: description of nature, description of working principles of technical devices and more self-referential texts, addressing the question of human identity in conflict situations. We discuss methodological problems within the two approaches (microanalysis and macroanalysis) to study brain activation in natural conditions, i.e. under a continuous speech flow. Within the thematic domain studies, only minimally significant differences in brain activation were registered during the listening to texts from the three thematic groups. This outcome leads to the conclusion that the approach of thematic group contrasts (cognitive subtraction methodology) is not sufficient to study the mechanisms of text comprehension, and should be replaced by the modeling of multidimensional representations of semantic categories in time. Within the semantic category approach, we describe the neurolinguistic process of text understanding as the activation of 15 clusters responsible for semantic categories (e.g. “Conflict”, “Mental”, “Social”). Our data demonstrate that the clusters are widely distributed across the human brain. In contrast to the previous studies, we suggest that deep subcortical structures are involved in the processing of certain categories as well. The observed lateralization of category processing underlines the involvement of the right hemisphere in the processing of meaning.

Size matters: How reaching and vergence movements are influenced by the familiar size of stereoscopically presented objects

The knowledge about the usual size of objects-familiar size-is known to be a taken into account for distance perception. The influence of familiar size on action programming is less clear and has not yet been tested with regard to vergence eye movements. In two experiments, we stereoscopically presented everyday objects, such as a credit card or a package of paper tissues, and varied the distance as specified by binocular disparity and the distance as specified by familiar size. Participants had to fixate the shown object and subsequently reach towards it either with open or with closed eyes. When binocular disparity and familiar size were in conflict, reaching movements revealed a combination of the two depth cues with individually different weights. The influence of familiar size was larger when no visual feedback was available during the reaching movement. Vergence movements closely followed binocular disparity and were largely unaffected by familiar size. In sum, the results suggest that in this experimental setting familiar size is taken into account for programming and executing reaching movements while vergence movements are primarily based on binocular disparity.

[A role of the immune system in the pathogenesis of schizophrenia]

The review addresses immunological aspects of schizophrenia, a multifactor disease caused by genetic factors, innate disorders of the central nervous system (CNS), including the consequences of perinatal hypoxia and infections, and adverse environmental influences. Neuroinflammation as a part of the pathophysiology of schizophrenia is characterized by the higher transcription of CNS inflammatory mediators, excessive activation of microglia, inhibition of glutamatergic receptors that leads to the decrease in the number of cortical synapses and neuronal apoptosis. The authors discuss a role of genetic polymorphisms of cytokine genes, complement system components etc. The literature data on the changes in systemic immune response and imbalance in Th1/Th2 adaptive immune responses are analyzed as well. Some papers showed higher levels of proinflammatory mediators in CSF and blood of patients with schizophrenia that indicated the involvement of blood brain barrier (BBB) dysfunction. The authors present the recent data on BBB dysfunction in schizophrenia and its role in the pathogenesis of the disease, autoimmunity in patients comparing it with immune activation and genetic predisposition. An important and arguable issues about a role of parasite and viral infections in the pathogenesis of schizophrenia, initiation of immune responses and direct impacts on the brain, an influence of antipsychotic treatment on immunity are discussed. In author's opinion, conflicting results of genetic and immunological studies of schizophrenia may be explained by different methodological approaches to selection of patients and healthy controls and the differences in schizophrenia classification.

Consciousness in a multilevel architecture: Evidence from the right side of the brain

By taking into account Bruce Bridgeman's interest in an evolutionary framing of human cognition, we examine effective (cause-and-effect) connectivity among cortical structures related to different parts of the triune phylogenetic stratification: archicortex, paleocortex and neocortex. Using resting-state functional magnetic resonance imaging data from 25 healthy subjects and spectral Dynamic Causal Modeling, we report interactions among 10 symmetrical left and right brain areas. Our results testify to general rightward and top-down biases in excitatory interactions of these structures during resting state, when self-related contemplation prevails over more objectified conceptual thinking. The right hippocampus is the only structure that shows bottom-up excitatory influences extending to the frontopolar cortex. The right ventrolateral cortex also plays a prominent role as it interacts with the majority of nodes within and between evolutionary distinct brain subdivisions. These results suggest the existence of several levels of cognitive-affective organization in the human brain and their profound lateralization.

EEG Negativity in Fixations Used for Gaze-Based Control: Toward Converting Intentions into Actions with an Eye-Brain-Computer Interface

We usually look at an object when we are going to manipulate it. Thus, eye tracking can be used to communicate intended actions. An effective human-machine interface, however, should be able to differentiate intentional and spontaneous eye movements. We report an electroencephalogram (EEG) marker that differentiates gaze fixations used for control from spontaneous fixations involved in visual exploration. Eight healthy participants played a game with their eye movements only. Their gaze-synchronized EEG data (fixation-related potentials, FRPs) were collected during game's control-on and control-off conditions. A slow negative wave with a maximum in the parietooccipital region was present in each participant's averaged FRPs in the control-on conditions and was absent or had much lower amplitude in the control-off condition. This wave was similar but not identical to stimulus-preceding negativity, a slow negative wave that can be observed during feedback expectation. Classification of intentional vs. spontaneous fixations was based on amplitude features from 13 EEG channels using 300 ms length segments free from electrooculogram contamination (200-500 ms relative to the fixation onset). For the first fixations in the fixation triplets required to make moves in the game, classified against control-off data, a committee of greedy classifiers provided 0.90 ± 0.07 specificity and 0.38 ± 0.14 sensitivity. Similar (slightly lower) results were obtained for the shrinkage Linear Discriminate Analysis (LDA) classifier. The second and third fixations in the triplets were classified at lower rate. We expect that, with improved feature sets and classifiers, a hybrid dwell-based Eye-Brain-Computer Interface (EBCI) can be built using the FRP difference between the intended and spontaneous fixations. If this direction of BCI development will be successful, such a multimodal interface may improve the fluency of interaction and can possibly become the basis for a new input device for paralyzed and healthy users, the EBCI "Wish Mouse."

Dynamic Causal Modeling of Hippocampal Links within the Human Default Mode Network: Lateralization and Computational Stability of Effective Connections

The purpose of this paper was to study causal relationships between left and right hippocampal regions (LHIP and RHIP, respectively) within the default mode network (DMN) as represented by its key structures: the medial prefrontal cortex (MPFC), posterior cingulate cortex (PCC), and the inferior parietal cortex of left (LIPC) and right (RIPC) hemispheres. Furthermore, we were interested in testing the stability of the connectivity patterns when adding or deleting regions of interest. The functional magnetic resonance imaging (fMRI) data from a group of 30 healthy right-handed subjects in the resting state were collected and a connectivity analysis was performed. To model the effective connectivity, we used the spectral Dynamic Causal Modeling (DCM). Three DCM analyses were completed. Two of them modeled interaction between five nodes that included four DMN key structures in addition to either LHIP or RHIP. The last DCM analysis modeled interactions between four nodes whereby one of the main DMN structures, PCC, was excluded from the analysis. The results of all DCM analyses indicated a high level of stability in the computational method: those parts of the winning models that included the key DMN structures demonstrated causal relations known from recent research. However, we discovered new results as well. First of all, we found a pronounced asymmetry in LHIP and RHIP connections. LHIP demonstrated a high involvement of DMN activity with preponderant information outflow to all other DMN regions. Causal interactions of LHIP were bidirectional only in the case of LIPC. On the contrary, RHIP was primarily affected by inputs from LIPC, RIPC, and LHIP without influencing these or other DMN key structures. For the first time, an inhibitory link was found from MPFC to LIPC, which may indicate the subjects’ effort to maintain a resting state. Functional connectivity data echoed these results, though they also showed links not reflected in the patterns of effective connectivity. We suggest that such lateralized architecture of hippocampal connections may be related to lateralization phenomena in verbal and spatial domains documented in human neurophysiology, neuropsychology, and neurolinguistics.

Changes in snoRNA and snRNA Abundance in the Human, Chimpanzee, Macaque, and Mouse Brain

Small nuclear and nucleolar RNAs (snRNAs and snoRNAs) are known to be functionally and evolutionarily conserved elements of transcript processing machinery. Here, we investigated the expression evolution of snRNAs and snoRNAs by measuring their abundance in the frontal cortex of humans, chimpanzees, rhesus monkeys, and mice. Although snRNA expression is largely conserved, 44% of the 185 measured snoRNA and 40% of the 134 snoRNA families showed significant expression divergence among species. The snRNA and snoRNA expression divergence included drastic changes unique to humans: A 10-fold elevated expression of U1 snRNA and a 1,000-fold drop in expression of SNORA29. The decreased expression of SNORA29 might be due to two mutations that affect secondary structure stability. Using in situ hybridization, we further localized SNORA29 expression to nucleolar regions of neuronal cells. Our study presents the first observation of snoRNA abundance changes specific to the human lineage and suggests a possible mechanism underlying these changes.

Effective Connectivity within the Default Mode Network: Dynamic Causal Modeling of Resting-State fMRI Data

The Default Mode Network (DMN) is a brain system that mediates internal modes of cognitive activity, showing higher neural activation when one is at rest. Nowadays, there is a lot of interest in assessing functional interactions between its key regions, but in the majority of studies only association of Blood-oxygen-level dependent (BOLD) activation patterns is measured, so it is impossible to identify causal influences. There are some studies of causal interactions (i.e., effective connectivity), however often with inconsistent results. The aim of the current work is to find a stable pattern of connectivity between four DMN key regions: the medial prefrontal cortex (mPFC), the posterior cingulate cortex (PCC), left and right intraparietal cortex (LIPC and RIPC). For this purpose functional magnetic resonance imaging (fMRI) data from 30 healthy subjects (1000 time points from each one) was acquired and spectral dynamic causal modeling (DCM) on a resting-state fMRI data was performed. The endogenous brain fluctuations were explicitly modeled by Discrete Cosine Set at the low frequency band of 0.0078–0.1 Hz. The best model at the group level is the one where connections from both bilateral IPC to mPFC and PCC are significant and symmetrical in strength (p < 0.05). Connections between mPFC and PCC are bidirectional, significant in the group and weaker than connections originating from bilateral IPC. In general, all connections from LIPC/RIPC to other DMN regions are much stronger. One can assume that these regions have a driving role within the DMN. Our results replicate some data from earlier works on effective connectivity within the DMN as well as provide new insights on internal DMN relationships and brain’s functioning at resting state.

[Macroscopic Functional Networks of the Human Brain when Viewing and Recalling Short Videos]

Macroscopic functional network of the human brain were identified by use of the independent component analysis (ICA) of fMRI while viewing and imaging/recalling stories. The networks were relatively stable in structure, but had a specific dynamics in different experimental conditions. When comparing detected networks with previously detected resting state networks it was found that they coincide on localization. We. discovered also the specificity of activating the peripheral and central parts of retinotopic projections in the visual cortex. The peripheral areas were activated during subject viewing and imaging/recalling. On the contrary, the central departments strengthened their activation when viewing and reduced activity during the imaging/recalling.

Effects of driving time on microsaccadic dynamics

Driver fatigue is a common cause of car accidents. Thus, the objective detection of driver fatigue is a first step toward the effective management of fatigue-related traffic accidents. Here, we investigated the effects of driving time, a common inducer of driver fatigue, on the dynamics of fixational eye movements. Participants drove for 2 h in a virtual driving environment while we recorded their eye movements. Microsaccade velocities decreased with driving time, suggesting a potential effect of fatigue on microsaccades during driving.

Attentional dynamics during free picture viewing: Evidence from oculomotor behavior and electrocortical activity

Most empirical evidence on attentional control is based on brief presentations of rather abstract stimuli. Results revealed indications for a dynamic interplay between bottom-up and top-down attentional mechanisms. Here we used a more naturalistic task to examine temporal signatures of attentional mechanisms on fine and coarse time scales. Subjects had to inspect digitized copies of 60 paintings, each shown for 40 s. We simultaneously measured oculomotor behavior and electrophysiological correlates of brain activity to compare early and late intervals (1) of inspection time of each picture (picture viewing) and (2) of the full experiment (time on task). For picture viewing, we found an increase in fixation duration and a decrease of saccadic amplitude while these parameters did not change with time on task. Furthermore, early in picture viewing we observed higher spatial and temporal similarity of gaze behavior. Analyzing electrical brain activity revealed changes in three components (C1, N1 and P2) of the eye fixation-related potential (EFRP); during picture viewing; no variation was obtained for the power in the frontal beta- and in the theta activity. Time on task analyses demonstrated no effects on the EFRP amplitudes but an increase of power in the frontal theta and beta band activity. Thus, behavioral and electrophysiological measures similarly show characteristic changes during picture viewing, indicating a shifting balance of its underlying (bottom-up and top-down) attentional mechanisms. Time on task also modulated top-down attention but probably represents a different attentional mechanism.

Gaze transfer in remote cooperation: is it always helpful to see what your partner is attending to?

Establishing common ground in remote cooperation is challenging because nonverbal means of ambiguity resolution are limited. In such settings, information about a partner's gaze can support cooperative performance, but it is not yet clear whether and to what extent the abundance of information reflected in gaze comes at a cost. Specifically, in tasks that mainly rely on spatial referencing, gaze transfer might be distracting and leave the partner uncertain about the meaning of the gaze cursor. To examine this question, we let pairs of participants perform a joint puzzle task. One partner knew the solution and instructed the other partner's actions by (1) gaze, (2) speech, (3) gaze and speech, or (4) mouse and speech. Based on these instructions, the acting partner moved the pieces under conditions of high or low autonomy. Performance was better when using either gaze or mouse transfer compared to speech alone. However, in contrast to the mouse, gaze transfer induced uncertainty, evidenced in delayed responses to the cursor. Also, participants tried to resolve ambiguities by engaging in more verbal effort, formulating more explicit object descriptions and fewer deictic references. Thus, gaze transfer seems to increase uncertainty and ambiguity, thereby complicating grounding in this spatial referencing task. The results highlight the importance of closely examining task characteristics when considering gaze transfer as a means of support.

Comparing two types of engineering visualizations: task-related manipulations matter

This study focuses on the comparison of traditional engineering drawings with a CAD (computer aided design) visualization in terms of user performance and eye movements in an applied context. Twenty-five students of mechanical engineering completed search tasks for measures in two distinct depictions of a car engine component (engineering drawing vs. CAD model). Besides spatial dimensionality, the display types most notably differed in terms of information layout, access and interaction options. The CAD visualization yielded better performance, if users directly manipulated the object, but was inferior, if employed in a conventional static manner, i.e. inspecting only predefined views. An additional eye movement analysis revealed longer fixation durations and a stronger increase of task-relevant fixations over time when interacting with the CAD visualization. This suggests a more focused extraction and filtering of information. We conclude that the three-dimensional CAD visualization can be advantageous if its ability to manipulate is used.

Implicit food associations as obstacles to healthy nutrition: the need for further research

Healthy nutrition is the driving force behind measures to address the obesity and diabetes epidemic. Therefore, the relevance of healthy nutrition to public health is steadily increasing. Although many consumers have positive attitudes towards healthy nutrition, their eating habits do not always match these attitudes. This paper suggests that individuals can overcome the discrepancy between attitude/intention and behaviour if they consider implicit associations with healthy or unhealthy nutrition. Our paper aims to develop a research strategy to analyse the impact of the interplay between explicit and implicit food associations on food consumption. The suggested process comprises the following steps: consumer segmentation, isolated analysis of different implicit drivers, holistic examination of interaction effects of different drivers and development of implications for policy makers and managers.

Fixation based event-related fmri analysis: using eye fixations as events in functional magnetic resonance imaging to reveal cortical processing during the free exploration of visual images

Eye movements, comprising predominantly fixations and saccades, are known to reveal information about perception and cognition, and they provide an explicit measure of attention. Nevertheless, fixations have not been considered as events in the analyses of data obtained during functional magnetic resonance imaging (fMRI) experiments. Most likely, this is due to their brevity and statistical properties. Despite these limitations, we used fixations as events to model brain activation in a free viewing experiment with standard fMRI scanning parameters. First, we found that fixations on different objects in different task contexts resulted in distinct cortical patterns of activation. Second, using multivariate pattern analysis, we showed that the BOLD signal revealed meaningful information about the task context of individual fixations and about the object being inspected during these fixations. We conclude that fixation-based event-related (FIBER) fMRI analysis creates new pathways for studying human brain function by enabling researchers to explore natural viewing behavior.

Yarbus, eye movements, and vision

The impact of Yarbus's research on eye movements was enormous following the translation of his book Eye Movements and Vision into English in 1967. In stark contrast, the published material in English concerning his life is scant. We provide a brief biography of Yarbus and assess his impact on contemporary approaches to research on eye movements. While early interest in his work focused on his study of stabilised retinal images, more recently this has been replaced with interest in his work on the cognitive influences on scanning patterns. We extended his experiment on the effect of instructions on viewing a picture using a portrait of Yarbus rather than a painting. The results obtained broadly supported those found by Yarbus.

Editorial

Editorial to the Special Issue on Eye tracking and Usability Research

Eye typing in application: A comparison of two systems with ALS patients

A variety of eye typing systems has been developed during the last decades. Such systems can provide support for people who lost the ability to communicate, e.g. patients suffering from motor neuron diseases such as amyotrophic lateral sclerosis (ALS). In the current retrospective analysis, two eye typing applications were tested (EyeGaze, GazeTalk) by ALS patients (N = 4) in order to analyze objective performance measures and subjective ratings. An advantage of the EyeGaze system was found for most of the evaluated criteria. The results are discussed in respect of the special target population and in relation to requirements of eye tracking devices.

Influences of dwell time and cursor control on the performance in gaze driven typing

In gaze controlled computer interfaces the dwell time is often used as selection criterion. But this solution comes along with several problems, especially in the temporal domain: Eye movement studies on scene perception could demonstrate that fixations of different durations serve different purposes and should therefore be differentiated. The use of dwell time for selection implies the need to distinguish intentional selections from merely per-ceptual processes, described as the Midas touch problem. Moreover, the feedback of the actual own eye position has not yet been addressed to systematic studies in the context of usability in gaze based computer interaction. We present research on the usability of a simple eye typing set up. Different dwell time and eye position feedback configurations were tested. Our results indicate that smoothing raw eye position and temporal delays in visual feedback enhance the system's functionality and usability. Best overall performance was obtained with a dwell time of 500 ms.

Surprise, surprise: Two distinct components in the visually evoked distractor effect

The distractor effect is an inhibition of saccades shortly after a sudden visual event. It has been explained both as an oculomotor reflex and as a manifestation of the orienting response. To clarify which explanation is more appropriate, we investigated a possible habituation of this effect. Visual and auditory distractors were presented at gaze-contingent intervals during the perception of meaningful pictures. Both reflexlike and modifiable components were present in the visual distractor effect, with latencies of about 110 and 180 ms, respectively. The influence of visual and auditory distractors on saccades preceded the earliest changes in cortical ERPs. Only for long-term habituation in the visual modality was a correlation with ERPs (N1) found.

Blinks, blanks and saccades: how blind we really are for relevant visual events

We report on a study in which subjects viewed color video stills of natural traffic situations while eye movements were recorded. A display change could occur randomly during three different occlusion modes--blinks, blanks and saccades--or during a fixation. These changes could be either relevant or irrelevant with respect to the traffic safety situation. Furthermore we contrasted insertions and deletions. All occlusion modes appeared equivalent concerning detection rate and detection time, and only differed from the fixation condition. The results also show that the detection of relevant changes was more likely and faster than that of irrelevant ones. However, even relevant insertions, which were almost always detected, were around 180 ms longer to report when they occurred during an occlusion. Furthermore, the detection of relevant changes was fairly stable across a wide range of the visual field, whereas irrelevant changes were less well detected, the further away from the fovea they occurred. We close with an outlook on a follow-up study where only relevant insertions and the blank occlusion were used in a driving simulator environment. Surprisingly, we found an advantage in change detection rate and time with blanks compared to the control condition. Change detection was also good during blinks, but not in saccades.

Heterarchy of cognition: the depths and the highs of a framework for memory research

To celebrate the levels-of-processing approach, I describe a multilevel evolutionary architecture for human behaviour and cognition. New experimental data on human eye movements are presented that demonstrate a possibility of splitting visual perceptual activity at least on two hierarchical but closely interrelated levels of processing. Furthermore, data from behavioural studies of human memory and neuroimaging testify that within the domain of cognition proper two higher levels can be differentiated. I call them "conceptual structures" and "metacognitive coordinations" and provide evidence that the latter may residue in the phylogenetically new structures of prefrontal and particularly right prefrontal cortices. From this point of few, the most natural framework for an analysis of the levels-of-processing effects on human memory is to consider them as interactions within the main gradients of evolution and development of the corresponding neurophysiological mechanisms. Finally, several new, still unanswered questions for the future research are formulated.

The omnipresent prolongation of visual fixations: saccades are inhibited by changes in situation and in subject's activity

Presenting a distractor prolongs not only saccadic reaction times in paced tasks but also fixation durations in unpaced tasks. To investigate whether the effect of a distractor is a pure optomotor reflex, we used both visual and auditory distractors in an unpaced picture-viewing paradigm. Results show a distractor effect for both modalities. Analysis of data from previous studies showed similar effects, even in amodal shifts of attention. These findings challenge the hypothesis that the effect is modality-specific and suggest that the distractor effect may be another expression of the orienting reflex.

Levels-of-processing effects on a variety of memory tasks: new findings and theoretical implications

Three experiments investigated level of processing (LOP) effects on a variety of direct and indirect memory tasks, in the context of a processing theory of dissociations. Subjects studied words in five encoding conditions and received one of ten memory tests. In Experiment 1, four tests previously classified as conceptual showed a robust LOP effect, as did a direct perceptual test of graphemic cued recall. An indirect perceptual word fragment completion test was unaffected by LOP. Experiment 2 showed that a new indirect version of a graphemic cued test was not affected by LOP. In Experiment 3, guided by a generation/recognition model, we constructed three new direct tests in which subjects identified words that were graphemically, phonologically, or semantically similar to studied words. The three tests differed in their sensitivity to study conditions, but LOP had no effect in any case, despite the involvement of deliberate conscious recollection. Contemporary explanatory frameworks couched as dichotomies (e.g., implicit/explicit, perceptual/conceptual) do not provide an adequate account of the results. It seems necessary instead to specify the types of information activated by each encoding condition, the types of information required by each test, and how encoding and retrieval processes are modified by task instructions.