Gisa Aschersleben

The Theory of Event Coding (TEC): a framework for perception and action planning.

Traditional approaches to human information processing tend to deal with perception and action planning in isolation, so that an adequate account of the perception-action interface is still missing. On the perceptual side, the dominant cognitive view largely underestimates, and thus fails to account for, the impact of action-related processes on both the processing of perceptual information and on perceptual learning. On the action side, most approaches conceive of action planning as a mere continuation of stimulus processing, thus failing to account for the goal-directedness of even the simplest reaction in an experimental task. We propose a new framework for a more adequate theoretical treatment of perception and action planning, in which perceptual contents and action plans are coded in a common representational medium by feature codes with distal reference. Perceived events (perceptions) and to-be-produced events (actions) are equally represented by integrated, task-tuned networks of feature codes--cognitive structures we call event codes. We give an overview of evidence from a wide variety of empirical domains, such as spatial stimulus-response compatibility, sensorimotor synchronization, and ideomotor action, showing that our main assumptions are well supported by the data.

Transformations in the Couplings Among Intellectual Abilities and Constituent Cognitive Processes Across the Life Span

Two-component theories of intellectual development over the life span postulate that fluid abilities develop earlier during child development and decline earlier during aging than crystallized abilities do, and that fluid abilities support or constrain the acquisition and expression of crystallized abilities. Thus, maturation and senescence compress the structure of intelligence by imposing age-specific constraints upon its constituent processes. Hence, the couplings among different intellectual abilities and cognitive processes are expected to be strong in childhood and old age. Findings from a population-based study of 291 individuals aged 6 to 89 years support these predictions. Furthermore, processing robustness, a frequently overlooked aspect of processing, predicted fluid intelligence beyond processing speed in old age but not in childhood, suggesting that the causes of more compressed functional organization of intelligence differ between maturation and senescence. Research on developmental changes in functional brain circuitry may profit from explicitly recognizing transformations in the organization of intellectual abilities and their underlying cognitive processes across the life span.

Synchronizing actions with events: The role of sensory information

Tasks requiring the subject to tap in synchrony to a regular sequence of stimulus events (e.g., clicks) usually elicit a response pattern in which the tap precedes the click by about 30-50 msec. This “negative asynchrony” was examined, first, by instructing subjects to use different effectors for tapping (hand vs. foot; Experiments 1 and 2), and second, by administering extrinsic auditory feedback in addition to the intrinsic tactile/kinesthetic feedback (Experiment 2). Experiment 3 controlled whether the results observed in Experiment 2 were due to purely sensory factors within the auditory modality. Results suggest that taps are synchronized with clicks at the central level by superimposing two sensory codes in time: the tactile/kinesthetic code that represents the tap (the afferent movement code) and the auditory code that represents the click (the afferent code that results from the guiding signal). Because the processing times involved in code generation are different for these two central codes, the tap has to lead over the click.

Correspondence effects with manual gestures and postures: A study of imitation

In this study, the authors applied methods and theories from research of stimulus-response compatibility (SRC) to action imitation. In 6 experiments, they adopted the logic of the Simon paradigm (B. Hommel & W. Prinz, 1996) to explore interference between task-relevant symbolic stimulus features (color) and task-irrelevant iconic stimulus features (2 hand gestures and 2 postures). The same 2 hand gestures served as responses. Pronounced correspondence effects for both gestures and postures showed up throughout. In line with theories of SRC, the authors account for these correspondence effects in terms of overlap arising between stimulus and response features in a common representational domain. As a specific extension of this approach, they propose 2 functionally independent mechanisms: One operates movement-based when dynamic information is provided, and the other operates state-based with static postures as stimuli. Implications for theories of both SRC and action imitation are discussed.

Automatic visual bias of perceived auditory location

Studies of reactions to audiovisual spatial conflict (alias “ventriloquism”) are generally presented as informing on the processes of intermodal coordination. However, most of the literature has failed to isolate genuine perceptual effects from voluntary postperceptual adjustments. A new approach, based on psychophysical staircases, is applied to the case of the immediate visual bias of auditory localization. Subjects have to judge the apparent origin of stereophonically controlled sound bursts as left or right of a median reference line. Successive trials belong to one of two staircases, starting respectively at extreme left and right locations, and are moved progressively toward the median on the basis of the subjects’ responses. Response reversals occur for locations farther away from center when a central lamp is flashed in synchrony with the bursts than without flashes (Experiment 1), revealing an attraction of the sounds toward the flashes. The effect cannot originate in voluntary postperceptual decision, since the occurrence of response reversal implies that the subject is uncertain concerning the direction of the target sound. The attraction is contingent on sound-flash synchronization, for early response reversals did no longer occur when the inputs from the two modalities were desynchronized (Experiment 2). Taken together, the results show that the visual bias of auditory localization observed repeatedly in less controlled conditions is due partly at least to an automatic attraction of the apparent location of sound by spatially discordant but temporally correlated visual inputs.

Codes and their vicissitudes

First, we discuss issues raised with respect to the Theory of Event Coding (TEC)s scope, that is, its limitations and possible extensions. Then, we address the issue of specificity, that is, the widespread concern that TEC is too unspecified and, therefore, too vague in a number of important respects. Finally, we elaborate on our views about TECs relations to other important frameworks and approaches in the field like stages models, ecological approaches, and the two-visual-pathways model.

Intention-based and stimulus-based mechanisms in action selection

Human actions can be classified as being either more stimulus-based or more intention-based. According to the ideomotor framework of action control, intention-based actions primarily refer to anticipated action effects (in other words response-stimulus [R-S] bindings), whereas stimulus-based actions are commonly assumed to be more strongly determined by stimulus-response [S-R] bindings. We explored differences in the functional signatures of both modes of action control in a temporal bisection task. Participants either performed a choice response by pressing one out of two keys in response to a preceding stimulus (stimulus-based action), or pressed one out of two keys to produce the next stimulus (intention-based action). In line with the ideomotor framework, we found intention-based actions to be shifted in time towards their anticipated effects (the next stimulus), whereas stimulus-based actions were shifted towards their preceding stimulus. Event-related potentials (ERPs) in the EEG revealed marked differences in action preparation for the two tasks. The data as a whole provide converging evidence for functional differences in the selection of motor actions as a function of their triggering conditions, and support the notion of two different modes of action selection, one being exogenous or mainly stimulus-driven, the other being endogenous or mainly intention-driven.

Temporal ventriloquism: Crossmodal interaction on the time dimension: 1. Evidence from auditory-visual temporal order judgment

In the well-known visual bias of auditory location (alias the ventriloquist effect), auditory and visual events presented in separate locations appear closer together, provided the presentations are synchronized. Here, we consider the possibility of the converse phenomenon: crossmodal attraction on the time dimension conditional on spatial proximity. Participants judged the order of occurrence of sound bursts and light flashes, respectively, separated in time by varying stimulus onset asynchronies (SOAs) and delivered either in the same or in different locations. Presentation was organized using randomly mixed psychophysical staircases, by which the SOA was reduced progressively until a point of uncertainty was reached. This point was reached at longer SOAs with the sounds in the same frontal location as the flashes than in different places, showing that apparent temporal separation is effectively longer in the first condition. Together with a similar one obtained recently in a case of tactile-visual discrepancy, this result supports a view in which timing and spatial layout of the inputs play to some extent inter-changeable roles in the pairing operation at the base of crossmodal interaction.

The cerebral oscillatory network associated with auditorily paced finger movements

Motor tasks involve neural activity in a spatially distributed network. It is assumed that coherent activity between these brain structures reflects functional connectivity. The aim of the present study was to investigate brain areas associated with a unimanual auditorily paced finger-tapping task and to characterize their dynamic interplay. We examined cerebromuscular and cerebrocerebral coupling in 10 right-handed subjects using recordings of continuous brain activity with a 122-channel whole-head neuromagnetometer while subjects performed the task with both hands consecutively. Additionally, surface EMG of the first dorsal interosseus was measured. Our data demonstrate that an oscillatory network composed of primary sensorimotor cortex, lateral as well as mesial premotor areas, the posterior parietal cortex and thalamus contralateral, and cerebellum and primary auditory cortex ipsilateral to the tapping hand subserves task execution. Connectivity between these areas and direction of coupling agree well with anatomical findings. During the right-hand condition, additional oscillatory activity in the primary sensorimotor cortex ipsilateral to the tapping hand was evident. This result suggests an asymmetric motor control in right-handers. Cerebrocerebral coupling predominantly occurs at 8-12 Hz. Therefore, our data support the hypothesis that coupling at 8-12 Hz in a cerebello-thalamic-cortical network represents a fundamental characteristic of the motor system and provides evidence for the significance of 8-12 Hz oscillations in a large scale network during the execution of simple motor tasks.

Localizing the first position of a moving stimulus: The Fröhlich effect and an attention-shifting explanation

When subjects are asked to determine where a fast-moving stimulus enters a window, they typically do not localize the stimulus at the edge, but at some later position within that window (Fröhlich effect). We report five experiments that explored this illusion. An attentional account is tested, assuming that the entrance of the stimulus in the window initiates a focus shift toward it. While this shift is under way, the stimulus moves into the window. Because the first phenomenal (i.e., explicitly reportable) representation of the stimulus will not be available before the end of the focus shift, the stimulus is perceived at some later position. In Experiment 1, we established the Fröhlich effect and showed that its size depends on stimulus parameters such as movement speed and movement direction. In Experiments 2 and 3, we examined the influence of eye movements and tested whether the effect changed when the stimuli were presented within a structural background or when they started from different eccentricities. In Experiments 4 and 5, specific predictions from the attentional model were tested: In Experiment 4 we showed that the processing of the moving stimulus benefits from a preceding peripheral cue indicating the starting position of the subsequent movement, which induces a preliminary focus shift to the position where the moving stimulus would appear. As a consequence the Fröhlich effect was reduced. Using a detection task in Experiment 5, we showed that feature information about the moving stimulus is lost when it falls into the critical interval of the attention shift. In conclusion, the present attentional account shows that selection mechanisms are not exclusively space based; rather, they can establish a spatial representation that is also used for perceptual judgment—that is, selection mechanisms can bespace establishing as well.