The impact of perceptual changes to studied items on ERP correlates of familiarity and recollection is subject to hemispheric asymmetries.

It is still unclear which role the right hemisphere (RH) preference for perceptually specific and the left hemisphere (LH) bias towards abstract memory representations play at the level of episodic memory retrieval. When stimulus characteristics hampered the retrieval of abstract memory representations, these hemispheric asymmetries have previously only modulated event-related potential (ERP) correlates of recollection (late positive complex, LPC), but not of familiarity (FN400). In the present experiment, we used stimuli which facilitated the retrieval of abstract memory representations. With the divided visual field technique, new items, identical repetitions and color-modified versions of incidentally studied object pictures were presented in either the right (RVF) or the left visual field (LVF). Participants performed a memory inclusion task, in which they had to categorize both identically repeated and color-modified study items as 'old'. Only ERP, but not behavioral data showed hemispheric asymmetries: Compared to identical repetitions, FN400 and LPC old/new effects for color-modified items were equivalent with RVF/LH presentation, but reduced with LVF/RH presentation. By promoting the use of abstract stimulus information for memory retrieval, we were thus able to show that hemispheric asymmetries in accessing abstract or specific memory representations can modulate ERP correlates of familiarity as well as recollection processes.

Exploring the Cognitive Processes Causing the Age-Related Categorization Deficit in the Recognition of Facial Expressions.

BACKGROUND/STUDY CONTEXT: Elderly people do not categorize emotional facial expressions as accurately as younger people, particularly negative emotions. Although age-related impairments in decoding emotions in facial expressions are well documented, the causes of this deficit are poorly understood. This study examined the potential mechanisms that account for this age-related categorization deficit by assessing its dependence on presentation time. METHODS: Thirty young (19-27 years old) and 31 older (68-78 years old) Chinese adults were asked to categorize the six basic emotions in facial expressions, each presented for 120, 200, 600, or 1000 ms, before and after exposure to a neutral facial expression. RESULTS: Shortened presentation times caused an age-related deficit in the recognition of happy faces, whereas no deficit was observed at longer exposure times. An age-related deficit was observed for all negative emotions but was not exacerbated by shorter presentation times. CONCLUSION: Age-related deficits in categorization of positive and negative emotions are caused by different mechanisms. Because negative emotions are perceptually similar, they cause high categorization demands. Elderly people may need more evidence in favor of the target emotion than younger people, and they make mistakes if this surplus of evidence is missing. In contrast, perceptually distinct happy faces were easily identified, and elderly people only failed when the presentation time was too short for their slower perceptual processing.

Effects of short-term experience on anticipatory eye movements during action observation.

Recent studies have shown that anticipatory eye movements occur during both action observation and action execution. These findings strongly support the direct matching hypothesis, which states that in observing others' actions, people take advantage of the same action knowledge that enables them to perform the same actions. Furthermore, a connection between action experience and the ability to anticipate action goals has been proposed. Concerning the role of experience, most studies concentrated on motor experts such as athletes and musicians, whereas only few studies investigated whether motor programs can be activated by short-term experience. Applying a pre-post design, we examined whether short-term experience affects anticipatory eye movements during observation. Participants (N = 150 university students) observed scenes showing an actor performing a block stacking task. Subsequently, participants performed either a block stacking task, puzzles, or a pursuit rotor task. Afterward, participants were again provided with the aforementioned block stacking task scenes. Results revealed that the block stacking task group directed their gaze significantly earlier toward the action goals of the block stacking task during posttest trials, compared with Puzzle and pursuit rotor task groups, which did not differ from each other. In accordance with the direct matching hypothesis, our study provides evidence that short-term experience with the block stacking task activates task-specific action knowledge.

Intercommunication between prefrontal and posterior brain regions for protecting visual working memory from distractor interference.

Because visual working memory has a very restricted capacity, good filtering mechanisms are essential for its successful functioning. A neuronal signal emitted by the prefrontal cortex is considered to be an important contributor to filtering. Proof of the functional significance of this signal during normal cognitive functioning is, however, still missing. Furthermore, research has so far neglected that the prefrontal cortex must receive input from posterior brain areas that report the necessity to filter. From human electroencephalograms, we extracted several event-related components that reflect the different subprocesses of filtering. On the basis of their timing and a clear pattern of correlations, we reason that filtering might consist of a causal chain of events that involve prefrontal and posterior cortex regions: After distractors are detected in posterior regions, a prefrontal mechanism is activated, which in turn prevents subsequent unnecessary parietal storage of distractor information.

Electrophysiological correlates of exemplar-specific processes in implicit and explicit memory.

The present ERP study investigated the retrieval of task-irrelevant exemplar-specific information under implicit and explicit memory conditions. Subjects completed either an indirect memory test (a natural/artificial judgment) or a direct recognition memory test. Both test groups were presented with new items, identical repetitions, and perceptually different but conceptually similar exemplars of previously seen study objects. Implicit and explicit memory retrieval elicited clearly dissociable ERP components that were differentially affected by exemplar changes from study to test. In the indirect test, identical repetitions, but not different exemplars, elicited a significant ERP repetition priming effect. In contrast, both types of repeated objects gave rise to a reliable old/new effect in the direct test. The results corroborate that implicit and explicit memory fall back on distinct cognitive representation and, more importantly, indicate that these representations differ in the type of stimulus information stored. Implicit retrieval entailed obligatory access to exemplar-specific perceptual information, despite its being task irrelevant. In contrast, explicit retrieval proved to be more flexible with conceptual and perceptual information accessed according to task demands.

An action video clip database rated for familiarity in China and Germany.

Stimulus material for studying object-directed actions is needed in different research contexts, such as action observation, action memory, and imitation. Action items have been generated many times in individual laboratories across the world, but they are used in very few experiments. For future studies in the field, it would be worthwhile to have a larger set of action stimulus material available to a broader research community. Some smaller action databases have already been published, but those often focus on psycholinguistic parameters and static action stimuli. With this article, we introduce an action database with dynamic action stimuli. The database contains action descriptions of 1,754 object-directed actions that have been rated for familiarity in Germany and in China. For 784 of these actions, action video clips are available. With the use of our database, it is possible to identify actions that differ in familiarity between Western and Eastern cultures. This variable may be of interest to some researchers in the field, since it has been shown that familiarity influences action information processing. Action descriptions are listed and categorized in tables that can be downloaded, along with the corresponding video clips, as supplemental material.

Task Demands Differentially Affect Processing of Intrinsic and Extrinsic Object Features in Working Memory.

Some argue that visual working memory operates on integrated object representations. Here, we contend that obligatory feature integration occurs with intrinsic but not extrinsic object features. Working memory for shapes and colors was assessed using a change-detection task with a central test probe, while recording event-related potentials (ERPs). Color was either an intrinsic surface feature of a shape or connected to the shape via a proximal but spatially disjunct extrinsic frame. There were two types of test: The direct test required memory for shape and color; the indirect test required only shape memory. Study-test changes of color were therefore either task-relevant or task-irrelevant. We assessed performance costs and event-related potential (ERP) effects arising from color changes. In the direct test, performance was poorer for extrinsic than intrinsic stimuli; task-relevant color changes elicited enhanced frontal negativity (N2, FN400) for both intrinsic and extrinsic stimuli. In the indirect test, performance costs and ERP effects associated with irrelevant color change were larger for intrinsic than extrinsic stimuli. This suggests intrinsic information is more readily integrated into the working-memory representation and evaluated against the test probe. Findings imply that feature integration is not obligatory under all conditions but influenced by stimulus-driven and task-related focus of attention.

What does ipsilateral delay activity reflect? Inferences from slow potentials in a lateralized visual working memory task.

In the lateralized change detection task, two item arrays are presented, one on each side of the display. Participants have to remember the items in the relevant hemifield and ignore the items in the irrelevant hemifield. A difference wave between contralateral and ipsilateral slow potentials with respect to the relevant items, the contralateral delay activity, can be calculated. As its amplitude varies with the number of items held in working memory (WM) and reaches its asymptote with WM capacity, it is considered a pure neural correlate of visual WM load. However, in addition to this contralateral delay activity, load-dependent activity has also been observed over the hemisphere ipsilateral to the relevant hemifield, suggesting that the ipsilateral hemisphere is also involved in memory-related processes. This ipsilateral activity might either reflect a bilateral processing of relevant or else a lateralized processing of irrelevant, to-be-filtered-out items. As in the lateralized change detection task, the number of items on both sides of the display is typically identical, it was not possible to decide between these alternatives yet. To disentangle the influence of relevant and irrelevant items, we orthogonally varied the number of both types of items. Processing of relevant items caused purely contralateral load-dependent activity. Ipsilateral slow potentials were influenced by the number of irrelevant items only if visual WM load was low, but not if it was high. This suggests that whether irrelevant items are processed or filtered out depends on visual WM load.

The advantage of mentally rotating clockwise.

The time taken to decide whether a character is shown in its mirror or normal version has been shown to increase approximately linearly with the angular departure from an up-right position. Additionally, in some studies, decisions took longer for clockwise tilted characters than for counterclockwise tilted ones. Other studies do not report the latter effect. We argue that inconsistencies across studies are caused by variance in participants' strategies. The task employed here was specifically designed to bring these strategies and thereby the direction of rotation under experimental control. From the EEG recorded during the rotation period, we extracted an event-related slow potential whose amplitude is sensitive to the amount of mental rotation. In both strategy conditions, the slow potential's amplitude was lower for clockwise than for counterclockwise rotations. We take this as evidence that mental rotation of alphanumeric characters is easier in a clockwise than in a counterclockwise direction.

Visual Working Memory of Chinese Characters and Expertise: The Expert's Memory Advantage Is Based on Long-Term Knowledge of Visual Word Forms.

People unfamiliar with Chinese characters show poorer visual working memory (VWM) performance for Chinese characters than do literates in Chinese. In a series of experiments, we investigated the reasons for this expertise advantage. Experiments 1 and 2 showed that the advantage of Chinese literates does not transfer to novel material. Experts had similar resolution as novices for material outside of their field of expertise, and the memory of novices and experts did not differ when detecting a big change, e.g., when a character's color was changed. Memorizing appears to function as a rather abstract representation of word forms because memory for characters' fonts was poor independently of expertise (Experiment 3), though still visual. Distractors that were highly similar conceptually did not increase memory errors, but visually similar distractors impaired memory (Experiment 4). We hypothesized that literates in Chinese represent characters in VWM as tokens of visual word forms made available by long-term memory. In Experiment 5, we provided novices with visual word form knowledge. Participants subsequently performed a change detection task with trained and novel characters in a functional magnetic resonance experiment. We analyzed set size- and training-dependent effects in the intraparietal sulcus (IPS) and the visual word form area. VWM for trained characters was better than for novel characters. Neural activity increased with set size and at a slower rate for trained than for novel characters. All conditions approached the same maximum, but novel characters reached the maximum at a smaller set size than trained characters. The time course of the bold response depended on set size and knowledge status. Starting from the same initial maximum, neural activity at small set sizes returned to baseline more quickly for trained characters than for novel characters. Additionally, high performers showed generally more neural activity in the IPS than low performers. We conclude that experts' better performance in working memory (WM) is caused by the availability of visual long-term representations (word form types) that allow a sparse representation of the perceived stimuli and make even small changes big because they cause a type change that is easily detected.

Unitization of internal and external features contributes to associative recognition for faces: Evidence from modulations of the FN400.

Associative recognition requires discriminating between old items and conjunction lures constructed by recombining elements from two different study items. This task can be solved not only by recollection but also by familiarity if the to-be-remembered stimuli are perceived as a unitized representation. In two event-related potential (ERP) studies, we provide evidence for the integration of internal and external facial features by showing that the early frontal old-new effect (considered a correlate of familiarity) is modulated by the specific combination of facial features. Participants studied faces consisting of internal features (eyes, eyebrows, nose, and mouth) paired with external features (hair, head shape, and ears). During the testing phase, intact, recombined, and new faces were presented. Recombined faces consisted of internal and external features taken from two different studied faces. The results showed that at the frontal sites, during the time window from 300 to 500 ms, ERPs to intact faces were more positive than those to new and recombined faces; the latter two did not differ from one another. The late parietal effect was observed only after a more extended study phase in Experiment 2. We take the modulation of the early frontal old-new effect as evidence for the contribution of familiarity to associative recognition for combinations of internal and external facial features.

Verbal predicates foster conscious recollection but not familiarity of a task-irrelevant perceptual feature--an ERP study.

Research on the effects of perceptual manipulations on recognition memory has suggested that (a) recollection is selectively influenced by task-relevant information and (b) familiarity can be considered perceptually specific. The present experiment tested divergent assumptions that (a) perceptual features can influence conscious object recollection via verbal code despite being task-irrelevant and that (b) perceptual features do not influence object familiarity if study is verbal-conceptual. At study, subjects named objects and their presentation colour; this was followed by an old/new object recognition test. Event-related potentials (ERP) showed that a study-test manipulation of colour impacted selectively on the ERP effect associated with recollection, while a size manipulation showed no effect. It is concluded that (a) verbal predicates generated at study are potent episodic memory agents that modulate recollection even if the recovered feature information is task-irrelevant and (b) commonly found perceptual match effects on familiarity critically depend on perceptual processing at study.

Spatio-Temporal Neural Changes After Task-Switching Training in Old Age.

In the present study, we aimed at examining selective neural changes after task-switching training in old age by not only considering the spatial location but also the timescale of brain activation changes (i.e., sustained/block-related or transient/trial-related timescales). We assigned a sample of 50 older adults to a task-switching training or an active single-task control group. We administered two task paradigms, either sensitive to transient (i.e., a context-updating task) or sustained (i.e., a delayed-recognition working-memory task) dynamics of cognitive control. These dynamics were captured by utilizing an appropriate event-related or block-related functional magnetic resonance imaging design. We captured selective changes in task activation during the untrained tasks after task-switching training compared to an active control group. Results revealed changes at the neural level that were not evident from only behavioral data. Importantly, neural changes in the transient-sensitive context updating task were found on the same timescale but in a different region (i.e., in the left inferior parietal lobule) than in the task-switching training task (i.e., ventrolateral PFC, inferior frontal junction, superior parietal lobule), only pointing to temporal overlap, while neural changes in the sustained-sensitive delayed-recognition task overlapped in both timescale and region with the task-switching training task (i.e., in the basal ganglia), pointing to spatio-temporal overlap. These results suggest that neural changes after task-switching training seem to be critically supported by the temporal organization of neural processing.

Visual and spatial working memory: from boxes to networks.

It is shown that visuo-spatial working memory is better characterized as processes operating on sensory information (visual appearance) and on spatial location (environmental coordinates) in a distributed network than as unitary slave system. Results from passive (short-term) and active memory tasks (imagery) disclose the properties (capacity, content) and the components of this network. The prefrontal cortex is a control structure (dorsal prefers active, ventral passive tasks) and it contributes to spatial memory by a prospective spatial code (eye movements). Visual appearance (including dynamic aspects) is represented as features and object files (bound features) within content-specific areas in the ventral occipital cortex. Spatial coordinates are represented in the parietal cortex (modality-unspecific), when used in spatio-temporal tasks (Corsi) they are closely related to attention. Imagery of objects activates occipito-temporal structures, spatial transformations and mental rotation the parietal cortex (specifically the intraparietal sulcus). Perception, working memory, and imagery use the same neural network. Differences between the tasks are explained by different demands and states of the neural network, and differences in the configuration of the anterior-posterior neural circuits.

Common coding of auditory and visual spatial information in working memory.

We compared spatial short-term memory for visual and auditory stimuli in an event-related slow potentials study. Subjects encoded object locations of either four or six sequentially presented auditory or visual stimuli and maintained them during a retention period of 6 s. Slow potentials recorded during encoding were modulated by the modality of the stimuli. Stimulus related activity was stronger for auditory items at frontal and for visual items at posterior sites. At frontal electrodes, negative potentials incrementally increased with the sequential presentation of visual items, whereas a strong transient component occurred during encoding of each auditory item without the cumulative increment. During maintenance, frontal slow potentials were affected by modality and memory load according to task difficulty. In contrast, at posterior recording sites, slow potential activity was only modulated by memory load independent of modality. We interpret the frontal effects as correlates of different encoding strategies and the posterior effects as a correlate of common coding of visual and auditory object locations.

Age-related changes in working memory: Age affects relational but not conjunctive feature binding.

In contrast to long-term memory, age-related association deficits in working memory are found only inconsistently. The authors hypothesized that type of binding is critical for the occurrence of such deficits. Relational binding abilities (associating separate visual units) should degrade with age, whereas more automatic conjunctive binding abilities (associating features within an object) should not. They contrasted associative memory and item memory using a change-detection task with colors and shapes in younger (18-33 years) and older (64-82 years) healthy adults. Color was either a surface feature of the shape (conjunctive binding) or a feature of a shape-external frame (relational binding). In a direct test of associative memory, participants memorized color-shape associations; in an indirect item memory test, participants were required to memorize only the shapes, and the authors measured the costs of ignoring task-irrelevant color changes from study to test. In the direct test, associative memory was poorer when relational binding was required rather than conjunctive binding, and associative memory was poorer in the older group, but no age-related association deficit was apparent. In the indirect test, by contrast, type of binding interacted with age: younger participants showed study-test congruence effects independent of the type of binding, but older adults showed enhanced congruence effects for conjunctive stimuli, indicating intact or even enhanced conjunctive binding, and practically no costs for relational stimuli, indicating poor relational binding. This stimulus-specific effect of a task-irrelevant feature change indicates that relational and conjunctive binding in working memory are differently affected by healthy aging. (PsycINFO Database Record

Event-related potential repetition effects at encoding predict memory performance at test.

The present study used multiple repetitions of meaningless pictorial stimuli to examine the electrophysiological correlates of the creation of a new stimulus representation. Study participants judged whether preexperimentally unfamiliar figures (meaningless line drawings) that were repeated up to four times contained a crossover in their contour. Stimulus repetition thereby led to a reduction of the visual N1 component in event-related potentials as well as to a late (430-600 ms), successively increasing positivity over posterior electrodes. In particular, the size of this latter event-related potential effect highly correlated with and thus predicted participants' performance in a subsequent recognition memory test. It can therefore be interpreted as neural correlate of the creation of a new memory-effective stimulus representation.

The influence of object and background color manipulations on the electrophysiological indices of recognition memory.

In a recognition memory experiment, the claim was tested that intrinsic object features contribute to familiarity, whereas extrinsic context features do not. We used the study-test manipulation of color to investigate the perceptual specificity of ERP old-new effects associated with familiarity and recollection. Color was either an intrinsic surface feature of the object or a feature of the surrounding context (a frame encasing the object); thus, the same feature was manipulated across intrinsic/extrinsic conditions. Subjects performed a threefold (same color/different color/new object) decision, making feature information task-relevant. Results suggest that the intrinsic manipulation of color affected the mid-frontal old-new effect associated with familiarity, while this effect was not influenced by extrinsic manipulation. This ERP pattern could not be explained by basic behavioral performance differences. It is concluded that familiarity can be perceptually specific with regard to intrinsic information belonging to the object. The putative electrophysiological signature of recollection - a late parietal old-new effect - was not present in the data, and reasons for this null effect are discussed.

Context effects on familiarity are familiarity effects of context - an electrophysiological study.

Within dual-process accounts of recognition memory, familiarity (as opposed to recollection) is often referred to as a rather automatic and context-free process. Thus, in episodic object recognition, familiarity and its electrophysiological ERP signature are supposed to index prior occurrence of an object independent of the context the object was originally encountered in, e.g., [Ecker, U.K.H., Zimmer, H.D., Groh-Bordin, C., in press. Color and context: An ERP study on intrinsic and extrinsic feature binding in episodic memory. Mem. Cogn.]). Yet, contextual sensitivity of familiarity has also been reported (e.g., [Tsivilis, D., Otten, L.J., Rugg, M.D., 2001. Context effects on the neural correlates of recognition memory: An electrophysiological study. Neuron 31, 497-505.]). We argue that considering attentional and perceptual factors of target processing is vital in understanding these conflicting results. Presenting target objects on contextual landscape scenes, we introduced a cueing technique designed to focus subjects' attention on target processing. We demonstrate that context effects on familiarity are diminished if the attentional impact of contextual stimuli is experimentally controlled, arguing that contextual influences on object familiarity are indirect and mediated by factors such as salience and attentional capture. Results suggest that salient context stimuli may elicit an independent familiarity signal instead of directly impacting on the familiarity signal of the target object. We conclude that (a) object familiarity is in principle a rather automatic and context-free process, and that (b) the study of episodic memory can profit substantially from adopting a dynamic processing perspective.

Is the Correlation between Storage Capacity and Matrix Reasoning Driven by the Storage of Partial Solutions? A Pilot Study of an Experimental Approach.

Working memory capacity (WMC) and reasoning abilities-as assessed by figural matrices tests-are substantially correlated. It is controversially discussed whether this correlation is only caused by controlled attention or also by storage capacity. This study aims at investigating storage of partial solutions as a possible mechanism by which storage capacity may contribute to solving figural matrices tests. For this purpose, we analyzed how an experimental manipulation of storage demands changes the pattern of correlations between WMC and performance in a matrix task. We manipulated the storage demands by applying two test formats: one providing the externalization of partial solutions and one without the possibility of externalization. Storage capacity was assessed by different types of change detection tasks. We found substantial correlations between storage capacity and matrices test performance, but they were of comparable size for both test formats. We take this as evidence that the necessity to store partial solutions is not the limiting factor which causes the association between storage capacity and matrices test. It is discussed how this approach can be used to investigate alternative mechanisms by that storage may influence performance in matrices tests.