Onset and Offset as Determinants of the Simon Effect

We investigated the presence and the characteristics of the Simon effect for onset and offset targets when these stimuli are randomly intermixed. In Experiment 1, two possible target locations were occupied by an occluder. On onset trials, a target appeared above an occluder, while on offset trials one of the occluders disappeared, revealing the target underneath. In Experiment 2, four stimuli appeared randomly in six possible locations. On onset trials, a new stimulus appeared in an empty location while on offset trials, one of the initial stimuli disappeared. In both experiments, the Simon effect for onset and offset targets was characterized by similar size, time course and sequential modulation, suggesting similar sensorimotor interactions between target and response locations. However, the Simon effect in the current trials was more evident when the same type of target (onset or offset) was repeated on successive trials demonstrating the role of stimulus category in its modulation

Tool use modulates early stages of visuo-tactile integration in far space:Evidence from event-related potentials

The neural representation of multisensory space near the body is modulated by the active use of long tools in non-human primates. Here, we investigated whether the electrophysiological correlates of visuo-tactile integration in near and far space were modulated by active tool use in healthy humans. Participants responded to a tactile target delivered to one hand while an irrelevant visual stimulus was presented ipsilaterally in near or far space. This crossmodal task was performed after the use of either short or long tools. Crucially, the P100 components elicited by visuo-tactile stimuli was enhanced on far as compared to near space trials after the use of long tools, while no such difference was present after short tool use. Thus, we found increased neural responses in brain areas encoding tactile stimuli to the body when visual stimuli were presented close to the tip of the tool after long tool use. This increased visuo-tactile integration on far space trials following the use of long tools might indicate a transient remapping of multisensory space. We speculate that performing voluntary actions with long tools strengthens the representation of sensory information arising within portions of space (i.e. the hand and the tip of the tool) that are most functionally relevant to one's behavioural goals

Searching on the back:Attentional selectivity in the periphery of the tactile field

Recent evidence has identified the N140cc lateralized component of event-related potentials as a reliable index of the deployment of attention to task-relevant items in touch. However, existing ERP studies have presented the tactile search array to participants' limbs, most often to the hands. Here, we investigated distractor interference effects when the tactile search array was presented to a portion of the body that is less lateralized and peripheral compared to the hands. Participants were asked to localize a tactile target presented among distractors in a circular arrangement to their back. The N140cc was elicited contralateral to the target when the singleton distractor was absent. Its amplitude was reduced when the singleton distractor was present and contralateral to the target, suggesting that attention was directed at least in part to the distractor when the singletons are on opposite sides. However, similar N140cc were observed when the singleton distractor was ipsilateral to the target compared to distractor absent trials. We suggest that when target and singleton distractor are ipsilateral, the exact localization of the target requires the attentional processing of all items on the same side of the array, similar to distractor absent trials. Together, these observations replicate the distractor interference effects previously observed for the hands, suggesting that analogous mechanisms guide attentional selectivity across different body parts

Visual imagery vividness and mental rotation of characters:An event related potentials study

Recent behavioural evidence suggests that differences in the vividness of visual imagery (VVI) affect the way in which mental rotation (MR) tasks are accomplished. However, the role of VVI in MR tasks is still debated. We explored it using event-related brain potentials (ERPs) which allow to track the time course of MR processes with high temporal resolution. We assigned participants to two different groups based on their VVI and compared the rotation-related negativity (RRN), the electrophysiological correlate of MR. Accuracy did not differ in the two groups. However, the RRN offset was delayed in lower as compared to higher VVI individuals. The processing of MR as indexed by the RRN is longer in individuals with lower VVI, providing direct evidence for a role of VVI in MR processing

Cognitive conflict is an example of action-grounded cognition.

The aim of the present work was to show that cognitive conflict, an issue that has been widely studied within the boundaries of the classical cognitive approach, is a clear example of higher order cognition tied to perception and action. Examples of how the cognitive conflict arising from spatial correspondence tasks is highly grounded in body attributes and in environmental/situational factors are provided. Spatial performance is strongly modulated by handedness, prior experience and by social factors. In addition, in two experiments empirical findings are reported showing that the spatial correspondence effect is a function of the location of the dynamic event even when target location is in the opposite position. These results point to the notion that spatial performance is refractory from the intervention of higher order cognition

Age-associated delay in mental rotation

Age-associated slowing in mental rotation (MR) process has been documented in the literature. Particularly, the intercept of the response times (RTs) function of rotation angle has been consistently found to be larger in older than in younger adults. However, the intercept represents the speed of response in two distinct sub-processes of MR: the initial phase of stimulus encoding and the final phase of response selection and execution. Thus, it remains unclear which of these two sub-processes of MR is affected by age. To investigate this, we recorded event-related potentials in younger and older individuals during a letter rotation task. The onset of the rotation-related negativity (RRN), the electrophysiological correlate of MR, was delayed in older (n = 20; mean age = 20.1) as compared to younger participants (n = 20, mean age = 73.4). Consistent with this observation, additional analyses revealed that the RRN amplitude was modulated by rotation angle between 350 and 500 ms post-stimulus in younger adults (n = 26, mean age = 21.0), while this modulation only emerged in the later time window (500-650ms) in older participants (n = 26; mean age = 73.6). These results suggest that MR occurs later in older adults and demonstrate that the initial phase before MR proper is one source of the age-related slowing observed in MR tasks. Possible accounts for this age-associated delay include a prolonged phase of stimulus encoding and/or selective difficulties in directing attention away from the external stimulus towards its internal mental representation

The effect of perceptual load on tactile spatial attention:Evidence from event related potentials

To investigate whether tactile spatial attention is modulated by perceptual load, behavioural and electrophysiological measures were recorded during two spatial cuing tasks in which the difficulty of the target/non-target discrimination was varied (High and Low load tasks). Moreover, to study whether attentional modulations by load are sensitive to the availability of visual information, the High and Low load tasks were carried out under both illuminated and darkness conditions. ERPs to cued and uncued non-targets were compared as a function of task (High vs. Low load) and illumination condition (Light vs. Darkness). Results revealed that the locus of tactile spatial attention was determined by a complex interaction between perceptual load and illumination conditions during sensory-specific stages of processing. In the Darkness, earlier effects of attention were present in the High load than in the Low load task, while no difference between tasks emerged in the Light. By contrast, increased load was associated with stronger attention effects during later post-perceptual processing stages regardless of illumination conditions. These findings demonstrate that ERP correlates of tactile spatial attention are strongly affected by the perceptual load of the target/non-target discrimination. However, differences between illumination conditions show that the impact of load on tactile attention depends on the presence of visual information. Perceptual load is one of the many factors that contribute to determine the effects of spatial selectivity in touch

External coding and salience in the tactile Simon effect

Previous studies have demonstrated a tactile Simon effect in which stimulus codes are generated based on the stimulated hand, not on limb position in external space (the somatotopic Simon effect). However, given evidence from visual Simon effect studies demonstrating that multiple stimulus codes can be generated for a single stimulus, we examined whether multiple stimulus codes can be generated for tactile stimuli as well. In our first experiment using four stimulators (two on each side of the hand), we found novel evidence for a hand-centered Simon effect, along with the typical somatotopic Simon effect. Next, we examined whether the potential salience of these somatotopic codes could be reduced, by testing only one hand with two stimulators attached. In Experiments 2\u20134, we found a strong hand-centered Simon effect with a diminished somatotopic Simon effect, providing evidence that stimulus salience can change the weighting of somatosensory stimulus coding. Finally, we also found novel evidence that the hand-centered Simon effect is coded in external, not somatotopic, coordinates. Furthermore, the diminished somatotopic Simon effect when testing on one hand only provides evidence that salience is an important factor in modulating the tactile Simon effect