Wladimir Kirsch

Brain structures involved in interoceptive awareness and cardioafferent signal processing: a dipole source localization study.

Afferent signals from the body play an important role for emotional and motivational aspects of behavior. Nevertheless, little is known about the cortical and subcortical structures involved in interoceptive processes. Recently, a functional MRI study demonstrated that insula, somatomotor, and cingulated cortices are activated when subjects focus attention on their heartbeats. Aside from the use of imaging data, cardiac awareness has frequently been studied by using the heartbeat‐evoked potential (HEP), a brain wave that appears contingent on the heartbeat. The present study aimed at localizing sources of the HEP. Multichannel EEG was recorded in 44 subjects while they performed a heartbeat perception task. This task was used to quantify interoceptive awareness and to subdivide the subjects into good and poor heartbeat perceivers. Analyses showed highest HEP amplitudes over frontal and frontocentral electrode locations in the time range of later than 200 ms after R‐wave onset. By means of a BESA dipole‐source‐analysis, four sources of the HEP were identified which were located in the anterior cingulate, the right insula, the prefrontal cortex, and the left secondary somatosensory cortex. Good heartbeat perceivers showed both significantly higher HEP amplitudes and higher dipole strength than poor heartbeat perceivers in all four cortical sources. We conclude that the identified structures are involved in the processing of cardiac signals, whereby anterior cingulate and right insula seem to serve as interoceptive centers for cardioception. Hum Brain Mapping, 2005.

Visual Near Space Is Scaled to Parameters of Current Action Plans

In the present study, we show that energetic costs of planned hand movements affect the perception of distances in reaching space. In three experiments, participants prepared hand movements that varied regarding movement amplitude or necessary movement force in either a blockwise or trial-by-trial manner. Before actual execution of the action, a visually presented distance had to be estimated. The results show that judgments of visual distances vary as a function of planned movement amplitude and movement force, specifically, when these parameters change rapidly from moment to moment. These findings show that previous reports of influences of action on perception from extrapersonal space and more enduring changes of action potential generalize to grasping space and much more subtle changes of movement effort. How actions affect visual perception might be determined by the changing parameters of current action plans.

Influence of Motor Planning on Distance Perception within the Peripersonal Space

We examined whether movement costs as defined by movement magnitude have an impact on distance perception in near space. In Experiment 1, participants were given a numerical cue regarding the amplitude of a hand movement to be carried out. Before the movement execution, the length of a visual distance had to be judged. These visual distances were judged to be larger, the larger the amplitude of the concurrently prepared hand movement was. In Experiment 2, in which numerical cues were merely memorized without concurrent movement planning, this general increase of distance with cue size was not observed. The results of these experiments indicate that visual perception of near space is specifically affected by the costs of planned hand movements.

Moving further moves things further away in visual perception: position-based movement planning affects distance judgments

We examined how different characteristics of planned hand movements affect visual perception of distances in reachable space. Participants planned hand movements of certain amplitude. Before execution of the movement, certain visual distances had to be judged. Distances were judged as larger the larger the amplitude of the concurrently prepared hand movements was. On top of that, with constant movement amplitude, distances were judged as larger, the further away the start point of the planned movement was located from the body. These results indicate that distinct variables specified during motor planning, such as effector’s final position, are linked to the visual perception of environmental characteristics.

Impact of planned movement direction on judgments of visual locations

Abstract The present study examined if and how the direction of planned hand movements affects the perceived direction of visual stimuli. In three experiments participants prepared hand movements that deviated regarding direction (“Experiment 1” and “2”) or distance relative to a visual target position (“Experiment 3”). Before actual execution of the movement, the direction of the visual stimulus had to be estimated by means of a method of adjustment. The perception of stimulus direction was biased away from planned movement direction, such that with leftward movements stimuli appeared somewhat more rightward than with rightward movements. Control conditions revealed that this effect was neither a mere response bias, nor a result of processing or memorizing movement cues. Also, shifting the focus of attention toward a cued location in space was not sufficient to induce the perceptual bias observed under conditions of movement preparation (“Experiment 4”). These results confirm that characteristics of planned actions bias visual perception, with the direction of bias (contrast or assimilation) possibly depending on the type of the representations (categorical or metric) involved.

Impact of action planning on spatial perception: attention matters.

Previous research suggested that perception of spatial location is biased towards spatial goals of planned hand movements. In the present study I show that an analogous perceptual distortion can be observed if attention is paid to a spatial location in the absence of planning a hand movement. Participants judged the position of a target during preparation of a mouse movement, the end point of which could deviate from the target by a varying degree in Exp. 1. Judgments of target position were systematically affected by movement characteristics consistent with perceptual assimilation between the target and the planned movement goal. This effect was neither due to an impact of motor execution on judgments (Exp. 2) nor due to characteristics of the movement cues or of certain target positions (Exp. 3, Exp. 5A). When the task included deployment of attention to spatial positions (former movement goals) in preparation for a secondary perceptual task, an effect emerged that was comparable with the bias associated with movement planning (Exp. 4, Exp. 5B). These results indicate that visual distortions accompanying manipulations of variables related to action could be mediated by attentional mechanisms.

On the origin of body-related influences on visual perception.

The human body and the potential to move it affect the way we perceive the world. Here we explored a possible origin of such action-specific effects on perception. Participants were asked to enclose a virtual object by movements of their index finger and thumb and judged either the actual finger-thumb distance or the size of the virtual object subsequently. The visual-haptic discrepancy that comes with such virtual grasping resulted in a mutual impact of visual and body-related signals: the visual judgments of object’s size were attracted by the felt finger posture and vice versa, judged finger distance was attracted by the size of the grasped object. This pattern was observed in spite of a clear spatial separation between somatic and visual signals and was conceptually replicated using a virtual reaching paradigm. The results indicate that basic mechanisms of multisensory integration accompany the emergence of action-specific effects on perception.

Hitting ability and perception of object's size: evidence for a negative relation

We examined the relation between motor performance and perception of object’s size in near space. The general task was to repeatedly hit a target by means of pointing movements and to estimate target’s size. In contrast to the results of previous studies, Experiment 1 and Experiment 2 revealed a negative relation between action ability and perceived target size: Participants who hit the target relatively often and whose motor variability was relatively low judged targets to be smaller than did participants whose motor performance was relatively poor. In Experiment 3, the size judgments were made in the presence of the target before, as well as after, pointing movements. The target was judged as smaller when it was easy, rather than difficult, to hit before as well as after the movement. Altogether, these results indicate that under certain conditions, an increased action ability reduces the apparent size of the actions’ target objects.

Impact of hand orientation on bimanual finger coordination in an eight-finger tapping task.

In the present experiment we examined whether a symmetry tendency in bimanual finger coordination is observable in an experimental setting resembling a serial learning task and whether this tendency is defined in hand-based coordinates. Participants performed an eight-finger bimanual coordination task, in which they responded to sequences of visual stimuli by sequences of tapping movements. Visual stimuli triggered flexion of fingers, which were parallel or mirror symmetrical in respect to the body midline. Additionally, the orientation of the right hand relative to the left hand was varied. When both hands had the same orientation, the mirror symmetrical mode was more stable than the parallel mode. When both hands had different orientations, in contrast, the parallel mode was more stable. This result suggests that the tendency towards mirror symmetry was defined in hand-based coordinates. This outcome is relevant for the research of skill learning regarding the issue of whether acquired sequence knowledge is tied to specific effectors.

Perceptual and behavioral adjustments after action inhibition

Inhibiting a motor action typically prompts a more cautious action mode, leaning toward accuracy rather than speed. In the present study, we explored whether action inhibition is also accompanied by changes of visual perception. Our participants performed goal-directed hand movements from a start to a target position and then judged the start–target distance. On a proportion of the trials, movement execution had to be stopped before the target position was reached. The results of two experiments revealed smaller start–target distance estimates after interrupted than after unrestricted movements. Moreover, movement amplitudes were decreased in movements that followed interrupted ones. In line with the predictions of action-specific accounts of perception, this outcome indicates that subjective perceptual changes might inform us how to plan future actions.