Elena Gherri

Manual response preparation and saccade programming are linked to attention shifts: ERP evidence for covert attentional orienting and spatially specific modulations of visual processing.

The premotor theory of attention claims that attentional shifts are triggered during response programming, regardless of which response modality is involved. To investigate this claim, event-related brain potentials (ERPs) were recorded while participants covertly prepared a left or right response, as indicated by a precue presented at the beginning of each trial. Cues signalled a left or right eye movement in the saccade task, and a left or right manual response in the manual task. The cued response had to be executed or withheld following the presentation of a Go/Nogo stimulus. Although there were systematic differences between ERPs triggered during covert manual and saccade preparation, lateralised ERP components sensitive to the direction of a cued response were very similar for both tasks, and also similar to the components previously found during cued shifts of endogenous spatial attention. This is consistent with the claim that the control of attention and of covert response preparation are closely linked. N1 components triggered by task-irrelevant visual probes presented during the covert response preparation interval were enhanced when these probes were presented close to cued response hand in the manual task, and at the saccade target location in the saccade task. This demonstrates that both manual and saccade preparation result in spatially specific modulations of visual processing, in line with the predictions of the premotor theory.

Co-occurrence of sequential and practice effects in the Simon task: Evidence for two independent mechanisms affecting response selection

The Simon effect refers to the observation that responses to a relevant stimulus dimension are faster and more accurate when the stimulus and response spatially correspond than when they do not, even though stimulus position is irrelevant. Recent findings have suggested that the Simon effect can be strongly modulated by prior practice with a spatially incompatible mapping and by correspondence sequence. Although practice is thought to influence conditional stimulus —response (S-R) processing, leaving response priming through the unconditional route unaffected, sequential effects are thought to represent trial-by-trial adaptations that selectively involve unconditional S —R processing. In the present study, we tested this assumption by assessing the effects of correspondence sequence both when the Simon task alone was performed and when it was preceded by a spatial compatibility task with either incompatible (Experiments 1-2) or compatible (Experiment 2) instructions. The observation that practice and correspondence sequence co-occur and exert additive effects strongly demonstrates that the two factors affect different processing routes.

ERP correlates of shared control mechanisms involved in saccade preparation and in covert attention

We investigated whether attention shifts and eye movement preparation are mediated by shared control mechanisms, as claimed by the premotor theory of attention. ERPs were recorded in three tasks where directional cues presented at the beginning of each trial instructed participants to direct their attention to the cued side without eye movements (Covert task), to prepare an eye movement in the cued direction without attention shifts (Saccade task) or both (Combined task). A peripheral visual Go/Nogo stimulus that was presented 800 ms after cue onset signalled whether responses had to be executed or withheld. Lateralised ERP components triggered during the cue–target interval, which are assumed to reflect preparatory control mechanisms that mediate attentional orienting, were very similar across tasks. They were also present in the Saccade task, which was designed to discourage any concomitant covert attention shifts. These results support the hypothesis that saccade preparation and attentional orienting are implemented by common control structures. There were however systematic differences in the impact of eye movement programming and covert attention on ERPs triggered in response to visual stimuli at cued versus uncued locations. It is concluded that, although the preparatory processes underlying saccade programming and covert attentional orienting may be based on common mechanisms, they nevertheless differ in their spatially specific effects on visual information processing.

Hypnotic Suggestion Modulates Cognitive Conflict The Case of the Flanker Compatibility Effect

The present work was aimed at investigating whether the flanker compatibility effect can be eliminated by means of a posthypnotic suggestion influencing attentional focusing. In Experiment 1, participants who scored high and low on hypnotic susceptibility performed the flanker compatibility task when naturally awake and when under a posthypnotic suggestion aimed at increasing the targets discriminability from the flankers. Results showed that the posthypnotic suggestion effectively eliminated the flanker compatibility effect in highly susceptible participants, whereas low-susceptibility participants did not show any reduction in the effect. In Experiment 2, highly susceptible participants performed the task after receiving a suggestion but without the induction of hypnosis. Results showed that the suggestion alone was not sufficient to reduce the flanker compatibility effect. These results support the view that in highly susceptible participants, hypnotic suggestion can influence the ability to focus on relevant information.

Manual response preparation disrupts spatial attention: An electrophysiological investigation of links between action and attention

Previous behavioural and neuroscience studies have shown that the systems involved in the control of attention and action are functionally and anatomically linked. We used behavioural and event-related brain potential measures to investigate whether such links are mandatory or merely optional. Cues presented at the start of each trial instructed participants to shift attention to the left or right side and to simultaneously prepare to a finger movement with their left or right hand. In different trials, cues were followed by a central Go signal, requiring execution of the prepared manual response (motor task), or by a peripheral visual stimulus, which required a target-non-target discrimination only when presented on the cued side (attention task). Lateralised ERP components indicative of covert attention shifts were found when attention and action were directed to the same side (same side condition), but not when attention and action were directed to opposite sides (opposite sides condition). Likewise, effects of spatial attention on the processing of peripheral visual stimuli were present only when attention and action were directed to the same side, but not in the opposite sides condition. These results demonstrate that preparing a manual response on one side severely disrupts the attentional selection of visual stimuli on the other side, and suggest that it is not possible to simultaneously direct attention and action to different locations in space. They support the hypothesis that the control of spatial attention and action are implemented by shared brain circuits, and are therefore linked in a mandatory fashion.

Active listening impairs visual perception and selectivity: An erp study of auditory dual-task costs on visual attention

The ability to drive safely is disrupted by cell phone conversations, and this has been attributed to a diversion of attention from the visual environment. We employed behavioral and ERP measures to study whether the attentive processing of spoken messages is, in itself, sufficient to produce visual–attentional deficits. Participants searched for visual targets defined by a unique feature (Experiment 1) or feature conjunction (Experiment 2), and simultaneously listened to narrated text passages that had to be recalled later (encoding condition), or heard backward-played speech sounds that could be ignored (control condition). Responses to targets were slower in the encoding condition, and ERPs revealed that the visual processing of search arrays and the attentional selection of target stimuli were less efficient in the encoding relative to the control condition. Results demonstrate that the attentional processing of visual information is impaired when concurrent spoken messages are encoded and maintained, in line with cross-modal links in selective attention, but inconsistent with the view that attentional resources are modality-specific. The distraction of visual attention by active listening could contribute to the adverse effects of cell phone use on driving performance.

Dissociating effector and movement direction selection during the preparation of manual reaching movements: Evidence from lateralized ERP components

Objective The present study investigated whether lateralized ERP components triggered during covert manual response preparation (ADAN, LDAP) reflect effector selection, the selection of movement direction, or both. Methods Event-related brain potentials were recorded during a response precueing paradigm where visual cues provided either partial (Experiment 1) or full (Experiment 2) information about the response hand and the direction for a subsequent reaching movement. Results ADAN and LDAP components were elicited even when only partial response information was available, demonstrating that they do not require the presence of a fully specified motor program. The ADAN was elicited in a similar fashion regardless of whether effector or movement direction information was provided, suggesting that the underlying mechanisms are equally sensitive to both types of response-related information. In contrast, the LDAP was larger in response to cues providing effector information, but was also reliably present when movement direction was available. Conclusions ADAN and LDAP components reflect preparatory activity within anterior and posterior parts of the parieto-premotor sensorimotor network where different parameters for manual reaching movements are programmed independently. Significance These results support the claim of the premotor theory of attention that shared sensorimotor control mechanisms are involved in attention and motor programming.

Links between eye movement preparation and the attentional processing of tactile events: An event-related brain potential study

OBJECTIVE We investigated whether the covert preparation of saccadic eye movements results in spatially specific modulations of somatosensory processing. METHODS ERPs were recorded in a spatial cueing experiment where auditory cues preceded tactile stimuli delivered to the left or right hand. In the Saccade task, cues signalled that an eye movement towards the left or right hand had to be prepared. In the Covert Attention task, cues signalled the direction of a covert shift of tactile attention. RESULTS A lateralized component previously observed during cued shifts of spatial attention (ADAN) was elicited in the cue-target interval in both tasks. The somatosensory N140 component was enhanced for tactile stimuli presented to the hand on the cued side. This modulation was present not just in the Covert Attention task, but also in the Saccade task. Longer-latency effects of spatial cueing were only present in the Covert Attention task. CONCLUSIONS Covert shifts of attention and saccade preparation have similar effects on early stages of tactile processing, suggesting that both are mediated by overlapping control processes. SIGNIFICANCE These findings support the premotor theory of attention by demonstrating that the programming of eye movements has spatially selective effects on somatosensory processing.

Action preparation helps and hinders perception of action

Several theories of the mechanisms linking perception and action require that the links are bidirectional, but there is a lack of consensus on the effects that action has on perception. We investigated this by measuring visual event-related brain potentials to observed hand actions while participants prepared responses that were spatially compatible (e.g., both were on the left side of the body) or incompatible and action type compatible (e.g., both were finger taps) or incompatible, with observed actions. An early enhanced processing of spatially compatible stimuli was observed, which is likely due to spatial attention. This was followed by an attenuation of processing for both spatially and action type compatible stimuli, likely to be driven by efference copy signals that attenuate processing of predicted sensory consequences of actions. Attenuation was not response-modality specific; it was found for manual stimuli when participants prepared manual and vocal responses, in line with the hypothesis that action control is hierarchically organized. These results indicate that spatial attention and forward model prediction mechanisms have opposite, but temporally distinct, effects on perception. This hypothesis can explain the inconsistency of recent findings on action–perception links and thereby supports the view that sensorimotor links are bidirectional. Such effects of action on perception are likely to be crucial, not only for the control of our own actions but also in sociocultural interaction, allowing us to predict the reactions of others to our own actions.

Eye movement preparation causes spatially-specific modulation of auditory processing: New evidence from event-related brain potentials

To investigate whether saccade preparation can modulate processing of auditory stimuli in a spatially-specific fashion, ERPs were recorded for a Saccade task, in which the direction of a prepared saccade was cued, prior to an imperative auditory stimulus indicating whether to execute or withhold that saccade. For comparison, we also ran a conventional Covert Attention task, where the same cue now indicated the direction for a covert endogenous attentional shift prior to an auditory target-nontarget discrimination. Lateralised components previously observed during cued shifts of attention (ADAN, LDAP) did not differ significantly across tasks, indicating commonalities between auditory spatial attention and oculomotor control. Moreover, in both tasks, spatially-specific modulation of auditory processing was subsequently found, with enhanced negativity for lateral auditory nontarget stimuli at cued versus uncued locations. This modulation started earlier and was more pronounced for the Covert Attention task, but was also reliably present in the Saccade task, demonstrating that the effects of covert saccade preparation on auditory processing can be similar to effects of endogenous covert attentional orienting, albeit smaller. These findings provide new evidence for similarities but also some differences between oculomotor preparation and shifts of endogenous spatial attention. They also show that saccade preparation can affect not just vision, but also sensory processing of auditory events.