Christian Groh-Bordin

Has the butcher on the bus dyed his hair? When color changes modulate ERP correlates of familiarity and recollection.

Recognition memory is usually thought of as comprising two distinct memory processes, namely familiarity and recollection. This distinction is reflected in specific event-related potential (ERP) components associated with both subprocesses. A mid-frontal attenuated negativity for correctly recognized old items relative to new ones around 400 ms has been typically linked to familiarity, whereas a parietally accentuated, more pronounced positivity for old items from 500 to 800 ms has been connected with recollection. Recently, this classification has been challenged by relating the mid-frontal old/new effect to conceptual priming mechanisms. Moreover, the perceptual sensitivity of both old/new effects is still under debate. The present study used a recognition memory task for visual objects and nonsense figures in order to investigate the functional significance of both ERP old/new effects. With respect to study presentation, all items were either presented in a perceptually identical or a color-modified version at test. Old nonsense figures, despite being meaningless, elicited a reliable mid-frontal old/new effect, thereby strongly suggesting a close relationship to familiarity processes rather than conceptual priming. Additionally, both the mid-frontal and the parietal old/new effect for real objects were graded with respect to the perceptual similarity between study and test. We argue that not only recollection, but also familiarity processes can provide information about perceptual atttributes, which is used in the course of recognition memory decisions.

Color and context: An ERP study on intrinsic and extrinsic feature binding in episodic memory

Episodic memory for intrinsic item and extrinsic context information is postulated to rely on two distinct types of representation: object and episodic tokens. These provide the basis for familiarity and recollection, respectively. Electrophysiological indices of these processes (ERPold-new effects) were used together with behavioral data to test these assumptions. We manipulated an intrinsic object feature (color; Experiment 1) and a contextual feature (background; Experiments 1 and 2). In an inclusion task (Experiment 1), the study—test manipulation of color affected object recognition performance and modulated ERPold—new effects associated with both familiarity and recollection. In contrast, a contextual manipulation had no effect, although both intrinsic and extrinsic information was available in a direct feature (source memory) test. When made task relevant (exclusion task; Experiment 2), however, context affected the ERP recollection effect, while still leaving the ERP familiarity effect uninfluenced. We conclude that intrinsic features bound in object tokens are involuntarily processed during object recognition, thus influencing familiarity, whereas context features bound in episodic tokens are voluntarily accessed, exclusively influencing recollection. Figures depicting all the electrodes analyzed are available in an online supplement at www.psychonomic.org/archive.

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.

Electrophysiological correlates of visual identity negative priming.

Negative priming (NP) refers to the finding that the processing of stimuli previously ignored is usually impaired in terms of reaction times and error rates. Although a robust empirical phenomenon, behavioral experiments were not able to ultimately distinguish between retrieval- and inhibition-based accounts of NP. Electrophysiological measures may help improve our understanding of this phenomenon. In this paper, we report an ERP correlate of identity NP with visual stimuli. In particular, we observed an enhanced N200 component when a distractor from the previous trial became the target in the next trial. This N200 modulation is explained in terms of a stronger response conflict when a previously ignored target must be selected against incompatible, and not previously ignored distractors; this interpretation is discussed as evidence for an inhibition view of NP.

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.

Where has all the inhibition gone? Insights from electrophysiological measures into negative priming without probe distractors.

Responses to probe targets that have been distractors in a prime display are slower than responses to unrepeated stimuli, a finding labeled negative priming (NP). However, without probe distractors the NP effect usually diminishes. The present study is the first to investigate ERP correlates of NP without probe distractors to shed light on the processes underlying NP. Based on existing findings in the field, we analyzed two ERP correlates that have been associated with the visual NP effect so far, namely the N200 and the P300. As expected, no behavioral NP effect as well as no N200 modulation emerged. However, the P300 component was enhanced when a prime distractor was repeated as the probe target. This effect is interpreted as reflecting automatic retrieval of the prime episode occurring independently of the presence of probe distractors.

Scanning your body is different from performing body movements: a double dissociation between body representational neglect and apraxia.

Body representational neglect (BRN) and apraxia can be found after left hemisphere (LH) lesions. Additionally, both disorders recruit knowledge about certain body parts, their position in space, and their spatial relationship to each other. Hence, the present study examined whether BRN and apraxia can be functionally dissociated at the behavioral and neural level. 23 LH lesioned patients were examined with a standardized body neglect test (Vest test) and a standardized test of apraxia (imitation of meaningless gestures). At the behavioral level BRN and apraxia showed a double dissociation. Moreover, these deficits were associated with specific brain lesions: while BRN was related to lesions in Brodmann areas 6 and 44 and frontal white matter, apraxia was linked to lesions in the superior longitudinal fasciculus and parietal and central white matter. The results are discussed as indicating dissociable representations of the human body within the left cerebral hemisphere.

Höhere visuelle Funktionen: Neglect, Raumorientierung, Balint-Holmes-Syndrom und visuelle Agnosien

Einbusen hoherer visueller Hirnfunktionen umfassen den halbseitigen Neglect, Raumorientierungsstorungen, das Balint-Holmes-Syndrom und die visuellen Agnosien.

Elementare visuelle Leistungen: Visus, Gesichtsfeld und verwandte Funktionen

Laien und nicht wenige Fachleute verstehen unter dem Begriff Sehleistungen oft ein recht eingeschranktes Repertoire an Fahigkeiten, zu denen am haufigsten das Scharfsehen, die Farberkennung und das raumliche Sehen gezahlt werden. Tatsachlich lassen sich unter diesem Begriff jedoch eine Fulle einzelner visueller Fahigkeiten zusammenfassen, derer man sich oft nicht bewusst ist, da sie meist automatisiert ablaufen. Der Existenz zahlreicher visueller Wahrnehmungsleistungen und darauf aufbauender visuomotorischer und motorischer Fahigkeiten wird man sich oft erst dann schmerzlich bewusst, wenn sie nach einer Hirnschadigung plotzlich nicht mehr wie gewohnt funktionieren. ◘ Abb. 14.1 vermittelt einen Eindruck von der Vielfalt der uns zur Verfugung stehenden visuellen Wahrnehmungsleistungen sowie ihrer jeweiligen Funktion im Rahmen von Wahrnehmung, Kognition und Handeln. Aus dieser Fulle visueller Wahrnehmungsleistungen beim gesunden Menschen resultiert eine ebensolche Vielfaltigkeit visueller Wahrnehmungsstorungen bei hirngeschadigten Patienten.