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Action preparation helps and hinders perception of action
No full textSeveral 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
A Neural Network Model of Inhibitory Processing in Subliminal Priming
No full textMasked Priming Experiments have revealed a precise set of facilitatory and inhibitory visual-motor control processes. Most notably, inhibitory effects have been identified in which prime-target compatibility induces performance costs and prime-target incompatibility induces performance benefits. We argue that this profile of data is commensurate with an ?emergency braking mechanism?, whereby responses can be retracted as a result of changing sensory evidence. The main contribution of this paper is to provide a neural network based explanation of this phenomenon. This is obtained through the use of feedforward inhibition to implement backward masking, lateral inhibition to implement response competition and opponent processing mechanisms to implement response retraction. Although the model remains simple, it does a very good job of reproducing the available masked priming data. For example, it reproduces a large spectrum of reaction time data across a number of different experimental conditions. Perhaps most notably however, it also reproduces Lateralized Readiness Potentials that have been recorded while subjects perform different conditions. In addition, it provides a concrete set of testable predictions
La pianificazione di movimenti oculari e’ in grado di indurre spostamenti dell’attentione? (Are shifts of attention elicited during covert eye movement preparation?). National Congress of the Italian Psychological Society, Division of Experimental Psychology, Como.
No full textDo ERP components triggered during attentional orienting represent supramodal attentional control?
No full textLateralized ERP components triggered during cued shifts of spatial attention (anterior directing attention negativity [ADAN], late directing attention positivity [LDAP]) have been observed during visual, auditory, and tactile attention tasks, suggesting that these components reflect supramodal attentional control processes. This interpretation has recently been called into question by the finding that the ADAN is absent in response to auditory attention cues. Here we demonstrate that ADAN and LDAP components are reliably elicited in a purely unimodal auditory attention task where auditory cues are followed by auditory imperative stimuli. The fact that the ADAN is not restricted to task contexts where visual or tactile stimuli are relevant is consistent with the hypothesis that this component is linked to supramodal attentional control
Ultraestructura de los vasos sanguíneos del órgano de Eimer
No full textEstudio de la ultraestructura de los capilares sanguíneos a nivel del órgano de Eimer de Talpa europaea utilizando técnicas particulares para microscopía óptica.Ministerio de Cultur
Compte rendu : H. Eimer, "R.O. Meisezahl (1906-1992), Die tibetischen Texte der Schenkung Imre Schwaiger"
No full textCompte rendu, Revue bibliographique de sinologie, 1996, 21 : H. Eimer, "R.O. Meisezahl (1906-1992), Oriens, vol. 34, 1994, p. 1-9; R.O. Meisezahl, "Die tibetischen Texte der Schenkung Imre Schwaiger", Oriens, vol. 34, 1994, 470-496
Links between eye movement preparation and the attentional processing of tactile events: An event-related brain potential study
No full textObjective
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
Active listening impairs visual perception and selectivity: an ERP study of auditory dual-tasks costs on visual attention
No full textThe 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
Manual response preparation disrupts spatial attention: an electrophysiological investigation of links between action and attention
No full textPrevious 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
Spatial attention can be allocated rapidly and in parallel to new visual objects
No full textIn real-life visual environments, where multiple objects compete for processing, new objects that require immediate attention often appear when attention is already focused elsewhere. The question of whether spatial attention can be directed independently to different locations in the visual field remains controversial [1]. Serial models assume a unitary attentional focus that is directed to one object at a time [2 and 3] and moves rapidly between objects [4 and 5]. According to parallel models, attention can be simultaneously allocated to several visual objects, but the distribution of attention cannot change rapidly when new objects arrive [6]. Here we demonstrate the existence of a fast and flexible mechanism of attentional object selection, where focal attention is allocated in parallel and independently to different target objects. Using event-related brain potential (ERP) markers of visual attention, we show that when two targets appear in rapid succession at different locations, two separate foci of attention are established, each with its own independent time course. Attention can be maintained at its previous location while it is simultaneously allocated to a new target object. Our results challenge the view that the attentional focus is always unitary and that the spatial selection of multiple visual objects operates in a strictly serial fashion
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