Herbert Hagendorf

Updating of working memory in a running memory task: an event-related potential study.

The aim of the study was to identify central executive activity in the event-related potential (ERP) in the time and space domain. Lists of three to eight consonants were presented sequentially. After each list the ordered recall of the three most recent items was required. In this running memory task the updating of working memory contents from the fourth letter on may be understood as a control process. ERPs elicited from each consonant presented in the lists were subtracted from those of a control condition that was also applied to the participants. The difference waveforms showed fronto-central distributed positivities, probably indicating the activity of a postulated central executive. This finding confirms those of neuroimaging studies that localize executive activity to prefrontal brain areas.

I spy with my little eye: detection of temporal violations in event sequences and the pupillary response.

Scripts of familiar activities store the temporal order of events. This enables us to generate predictions about which event will follow another. When an event does not unfold in the chronological order, a mismatch arises between the predictions and the external sensory input which is perceived as a conflict. The detection of this mismatch is accomplished by a comparison mechanism (Zacks et al., 2007; Barsalou, 2009). We have applied pupillometry to investigate the nature of this comparison process. We further tested for individual differences in the efficiency of the mismatch detection. Participants were presented the title of an event sequence to trigger predictions about the order in which events would unfold. Subsequently, three script events were presented one at a time. The events either unfolded in the correct chronological order or included temporal violations at different points within the event triplet. Violations of the temporal order had to be detected. As soon as it was detected, the trial had to be terminated. We found that a temporal violation elicited a large pupillary response in all individuals indicating that the comparison between the predictions and the external sensory input was accomplished online and worked equally well for all individuals. However, not all individuals terminated the trial after having detected the violation. Results showed that efficient individuals who responded adequately had a greater pupillary response than inefficient individuals suggesting that they invested more cognitive resources. The results are discussed in light of theories of behavioral performance and conflict-monitoring.

An fMRI investigation into the neural mechanisms of spatial attentional selection in a location-based negative priming task

Selective attention enables us to respond to objects and events that are relevant to our goals for adaptive interactions with the environment. Despite evidence from research addressing the selection of a target location, little is known about the neural mechanisms of attentional selection in situations in which the selection is biased in favor of the information in the irrelevant location. In this study, we combined event-related fMRI and a location-based negative priming paradigm with a prime-probe-trial design to investigate the neural mechanisms of spatial attentional selection. Participants were instructed to respond to the location of a pre-specified target while ignoring a distractor at an irrelevant location. The goal of this study was twofold. First, we identified brain regions that are linked to conflict resolution situations, in which the selection bias puts the irrelevant information in the probe trial on a selection advantage over the target. Second, we determined the mechanism of conflict resolution when the encoding conditions of stimuli are manipulated by presenting stimuli either abruptly (onset) or masked (no-onset). The results showed that the bottom-up-induced competition among stimuli in the target selection is stronger for onset than no-onset stimuli. The superior parietal lobule was sensitive to those changes in bottom-up-induced competition. Furthermore, the dorsolateral prefrontal cortex and inferior parietal lobe were activated to resolve the additional processing effort necessary to select the negatively biased target. In conclusion, the present study identified dissociable neural components needed to resolve the negative selection bias, which attentional modulation can be addressed in future studies by examining changes in the functional connectivity.

Insights Into Knowledge Representation: The Influence of Amodal and Perceptual Variables on Event Knowledge Retrieval From Memory

Event sequences or scripts are the conceptual representations of activities in memory. Traditional views hold that events are represented in amodal networks and are retrieved by associative strategies. The embodied cognition approach holds that knowledge is grounded in perception and retrieved by mental simulation. We used a script generation task where event sequences of activities had to be produced. Activities varied in their degree of familiarity. In a regressional design we investigated whether amodal or perceptual variables best predicted knowledge retrieval to gain insight into the underlying representation. Retrieval depended on the familiarity of the activity. While novel activities mainly relied on perception-based simulation and to a lesser extent on associative strategies, moderately familiar activities showed the opposite pattern, and events of familiar activities were retrieved by association alone. We conclude that amodal structures exist in all representations that become stronger with increasing frequency and finally prevail over perceptual structures.

Electrophysiological evidence for cognitive control during conflict processing in visual spatial attention

Event-related potentials were measured to investigate the role of visual spatial attention mechanisms in conflict processing. We suggested that a more difficult target selection leads to stronger attentional top-down control, thereby reducing the effects of arising conflicts. This hypothesis was tested by varying the selection difficulty in a location negative priming (NP) paradigm. The difficult task resulted in prolonged responses as compared to the easy task. A behavioral NP effect was only evident in the easy task. Psychophysiologically the easy task was associated with reduced parietal N1, enhanced frontocentral N2 and N2pc components and a prolonged P3 latency for the conflict as compared to the control condition. The N2pc effect was also obvious in the difficult task. Additionally frontocentral N2 amplitudes increased and latencies of N2pc and P3 were delayed compared to the easy task. The differences at frontocentral and parietal electrodes are consistent with previous studies ascribing activity in the prefrontal and parietal cortex as the source of top-down attentional control. Thus, we propose that stronger cognitive control is involved in the difficult task, resulting in a reduced behavioral NP conflict.

Hemifield effects of spatial attention in early human visual cortex

Early visual areas (V1, V2, V3/VP, V4v) contain representations of the contralateral hemifield within each hemisphere. Little is known about the role of the visual hemifields along the visuo‐spatial attention processing hierarchy. It is hypothesized that attentional information processing is more efficient across the hemifields (known as bilateral field advantage) and that the integration of information is greater within one hemifield as compared with across the hemifields. Using functional magnetic resonance imaging we examined the effect of distance and hemifield on parallel attentional processing in the early visual areas (V1–V4v) at individually mapped retinotopic locations aligned adjacently or separately within or across the hemifields. We found that the bilateral field advantage in parallel attentional processing over separated attended locations can be assigned, at least partly, to differences in distractor position integration in early visual areas. These results provide evidence for a greater integration of locations between two attended locations within one hemifield than across both hemifields. This nicely correlates with behavioral findings of a bilateral field advantage in parallel attentional processing (when distractors in between cannot be excluded) and a unilateral field advantage if attention has to be shifted across separated locations (when locations in between were integrated).

Coordination in visual working memory

Coordination of mental procedures is considered in terms of control processes (Baddeley, 1989) in visual working memory and appears to be a separable aspect of the demand imposed by cascaded serial processes (Carlson & Lundy, 1992). The main task required subjects to indicate whether symbolically suggested rotations and reflections correctly describe the difference between matrix patterns of filled-in squares within a 3 x 3 grid or between line drawings. Experiments were carried out to show that coordination is a separable component in this transformation task. A marker for coordination is the difference between the time taken to execute two transformations as a whole and the sum of the component transformations in isolation. The separate coordination demand was found in an experiment with matrix patterns mentioned, in an experiment with letter-like line drawings, and also in an experiment that forced subjects to maintain whole-pattern representations. A last experiment checked whether coordination is carried out by an autonomous control unit. There was a self-paced control of serial presentation of transformation symbols instead of a simultaneous presentation of those symbols. This additional external triggering resulted in a substantial decrease in the demand for coordination. Coordination of mental procedures and temporary representations is a fundamental constraint on the use of working-memory processes.

The role of temporal properties on the detection of temporal violations: insights from pupillometry

Scripts store the temporal order of component events of everyday activities as well as the temporal position of the events within the activity (early or late). When confronted with an activity, predictions are generated about how the component events will unfold. Thereby, an error-detection mechanism continuously monitors whether they unfold as anticipated or not in order to reveal errors in the unfolding activity. We investigated whether the temporal position “early” or “late” influenced the detection of errors using the pupillary response as an index of cognitive resource consumption. An event triplet consisting of three events was presented in a chronological or non-chronological temporal order. Crucially, the triplet focused either on the beginning (temporal position “early”) or the end (temporal position “late”) of an activity. We assumed that these position codes would be used to facilitate error detection when a non-chronological event was presented. Results showed that errors in the temporal order were detected more successfully in early than in late triplets. Results further suggest that strong predictions are formed about how an activity begins. Violations of this prediction must be overcome by zooming into the representation and allocating attention to the temporal position that consumes cognitive resources. Only after zooming in has taken place successfully may the position codes be used to anticipate temporal violations in unfolding event sequences.

Semantic Priming of Progression Features in Events

Event knowledge includes persons and objects and their roles in the event. This study investigated whether the progression of patients from a source to a resulting feature, such as the progression of hair that is cut from long to short, forms part of event representations. Subjects were presented with an event prime followed by two adjectives and asked to judge whether the adjectives were interrelated. Results showed that the semantic interrelation of two adjectives is recognized faster and more accurately when the adjectives denote source and resulting features of the patient of the primed event (“cutting”: long–short). Furthermore, we found that presenting an event-related adjective in combination with an unrelated adjective makes it more difficult to recognize that the two adjectives are not interrelated, but only when the event-related adjective denotes a source feature. We argue that an inference mechanism automatically completes the representation of the event. We conclude that source and resulting features are represented in a goal-directed and chronological way.

Cooking from cold to hot: Goal-directedness in simulation and language

Abstract The present study explores the processing of temporal information in event knowledge by focusing on the transition from an earlier, source state to a later, goal state. Participants were presented with an event verb followed by antonymous adjectives or adverbs denoting an earlier state and a later state. The states were presented either chronologically (to cook: cold – hot) or inversely (to cook: hot – cold) with regard to the denoted event. Participants were asked to identify either the earlier or the later state. We found that later states are identified faster and more accurately than earlier states. Later states presented chronologically were identified even more quickly than later states presented inversely. We attribute our results to the fact that directedness towards the goal state is a general principle of cognition which plays a fundamental role in language and in simulation, whereby language processing provides faster and more direct access to goals even than simulation.