Asymmetric effects of graspable distractor disks on motor preparation of successive grasps: A behavioural and event-related potential (ERP) study.

There is evidence that seeing a graspable object automatically elicits a preparatory motor process. However, it is unclear whether this implicit visuomotor process might influence the preparation of a successive grasp for a different object. We addressed the issue by implementing a combined behavioural and electrophysiological paradigm. Participants performed pantomimed grasps directed to small or large disks with either a two (pincer) or a five-finger (pentapod) grip, after the presentation of congruent (same size) or incongruent (different size) distractor disks. Preview reaction times (PRTs) and response-locked lateralized readiness potentials (R-LRPs) were recorded as online indices of motor preparation. Results revealed asymmetric effects of the distractors on PRTs and R-LRPs. For pincer grip disks, incongruent distractors were associated with longer PRTs and a delayed R-LRP peak. For pentapod grip disks, conversely, incongruent distractors were associated with shorter PRTs and a delayed R-LRP onset. Supporting an interpretation of these effects as tapping into motor preparation, we did not observe modulations of stimulus-locked LRP's (sensitive to sensory processing), or of the P300 component (related to reallocating attentional resources). These results challenge models (i.e., the "dorsal amnesia" hypothesis) which assume that visuomotor information presented before a grasp will not affect how we later perform that grasp.

All talk? Challenging the use of left-temporal EEG alpha oscillations as valid measures of verbal processing and conscious motor control.

This study tested the validity of EEG left-temporal alpha power and upper-alpha T7-Fz connectivity as indices of verbal activity and conscious motor control. Participants (n = 20) reached for, and transported, a jar under three conditions: a control condition and two self-talk conditions aimed at eliciting either task-unrelated verbal processing or task-related conscious control, while EEG and hand kinematics were recorded. Compared to the control condition, both self-talk conditions increased self-reported verbal processing, but only the task-related self-talk condition increased left-temporal activity (i.e., alpha power decreased). However, as cortical activity increased across the entire scalp topography, conscious control likely elicits a multitude of processes that may not be explained by left-temporal activity or verbal processing alone, but by a widespread decrease in neural efficiency. No significant effects for T7-Fz connectivity were detected. Results suggest that left-temporal EEG alpha oscillations are unlikely to uniquely reflect verbal processing during conscious motor control.

The effects of valid and invalid expectations about stimulus valence on behavioural and electrophysiological responses to emotional pictures.

Previous studies have shown that uncertainty about the expected valence of an upcoming stimulus modulates behavioural and neural responses to the stimulus. However, relatively little is known about how invalid emotion expectations (i.e. expecting a positive picture but seeing a negative picture) affect neural and behavioural responses. To investigate this, two experiments were conducted where participants viewed and rated the pleasantness of emotional pictures that were preceded by a cue. In Experiment 1, there were three cue conditions: uncertain, valid and invalid. The uncertain cue did not indicate the valence of the upcoming picture, whereas cues in the valid condition (70% of positive and negative cues) correctly indicated the valence of the upcoming picture. The remaining trials were invalid, where the valence of the picture differed from the expected valence. Behavioural results showed that invalidly cued negative pictures elicited more neutral valence ratings compared to validly cued pictures. In Experiment 2 we replicated the findings of Experiment 1, and in addition found an increased amplitude for the early (400-600 ms) portion of the late positive potential (LPP) for invalidly compared to validly cued pictures. Together, these results show that invalid expectations influence the neural and behavioural processing of subsequently presented emotional pictures, where invalidly cued pictures led to attenuated (i.e., more neutral) emotional responses, and enhanced early LPP amplitude, compared to validly cued pictures.

Systematic Distortions in Vertical Placement of Features in Drawings of Faces and Houses.

A crucial part of accurately drawing portraits is the correct vertical positioning of the eyes. Non-experts typically place the eyes higher on the head than they are actually located; however, the explanation for this remains unclear. In Experiment 1, participants drew faces from memory and directly copied from a photograph, to confirm whether biases in observational drawings were related to biases in memory-based drawings. In Experiment 2, participants drew a cat's face, to test explanations by Carbon and Wirth for the positional bias: the 'view-from-below, the 'head-as-box', and the 'hair-as-hat' explanations. Results indicated that none of these three explanations could fully account for the vertical positioning biases observed in drawings of the cat's face. The findings are discussed in relation to the idea that distortions of vertical alignment in drawings may be related to the position of the most salient features within a face or object.

Effect Anticipation Affects Perceptual, Cognitive, and Motor Phases of Response Preparation: Evidence from an Event-Related Potential (ERP) Study.

The anticipation of action effects is a basic process that can be observed even for key-pressing responses in a stimulus-response paradigm. In Ziessler et al.'s (2012) experiments participants first learned arbitrary effects of key-pressing responses. In the test phase an imperative stimulus determined the response, but participants withheld the response until a Go-stimulus appeared. Reaction times (RTs) were shorter if the Go-stimulus was compatible with the learned response effect. This is strong evidence that effect representations were activated during response planning. Here, we repeated the experiment using event-related potentials (ERPs), and we found that Go-stimulus locked ERPs depended on the compatibility relationship between the Go-stimulus and the response effect. In general, this supports the interpretation of the behavioral data. More specifically, differences in the ERPs between compatible and incompatible Go-stimuli were found for the early perceptual P1 component and the later frontal P2 component. P1 differences were found only in the second half of the experiment and for long stimulus onset asynchronies (SOAs) between imperative stimulus and Go-stimulus, i.e., when the effect was fully anticipated and the perceptual system was prepared for the effect-compatible Go-stimulus. P2 amplitudes, likely associated with evaluation and conflict detection, were larger when Go-stimulus and effect were incompatible; presumably, incompatibility increased the difficulty of effect anticipation. Onset of response-locked lateralized readiness potentials (R-LRPs) occurred earlier under incompatible conditions indicating extended motor processing. Together, these results strongly suggest that effect anticipation affects all (i.e., perceptual, cognitive, and motor) phases of response preparation.

Modulation of auditory spatial attention by visual emotional cues: differential effects of attentional engagement and disengagement for pleasant and unpleasant cues.

Previous research has demonstrated that threatening, compared to neutral pictures, can bias attention towards non-emotional auditory targets. Here we investigated which subcomponents of attention contributed to the influence of emotional visual stimuli on auditory spatial attention. Participants indicated the location of an auditory target, after brief (250 ms) presentation of a spatially non-predictive peripheral visual cue. Responses to targets were faster at the location of the preceding visual cue, compared to at the opposite location (cue validity effect). The cue validity effect was larger for targets following pleasant and unpleasant cues compared to neutral cues, for right-sided targets. For unpleasant cues, the crossmodal cue validity effect was driven by delayed attentional disengagement, and for pleasant cues, it was driven by enhanced engagement. We conclude that both pleasant and unpleasant visual cues influence the distribution of attention across modalities and that the associated attentional mechanisms depend on the valence of the visual cue.

The effects of stereo disparity on the behavioural and electrophysiological correlates of perception of audio-visual motion in depth.

Motion is represented by low-level signals, such as size-expansion in vision or loudness changes in the auditory modality. The visual and auditory signals from the same object or event may be integrated and facilitate detection. We explored behavioural and electrophysiological correlates of congruent and incongruent audio-visual depth motion in conditions where auditory level changes, visual expansion, and visual disparity cues were manipulated. In Experiment 1 participants discriminated auditory motion direction whilst viewing looming or receding, 2D or 3D, visual stimuli. Responses were faster and more accurate for congruent than for incongruent audio-visual cues, and the congruency effect (i.e., difference between incongruent and congruent conditions) was larger for visual 3D cues compared to 2D cues. In Experiment 2, event-related potentials (ERPs) were collected during presentation of the 2D and 3D, looming and receding, audio-visual stimuli, while participants detected an infrequent deviant sound. Our main finding was that audio-visual congruity was affected by retinal disparity at an early processing stage (135-160ms) over occipito-parietal scalp. Topographic analyses suggested that similar brain networks were activated for the 2D and 3D congruity effects, but that cortical responses were stronger in the 3D condition. Differences between congruent and incongruent conditions were observed between 140-200ms, 220-280ms, and 350-500ms after stimulus onset.

The effect of colour and size on attentional bias to alcohol-related pictures

Attentional bias plays an important role in the development and maintenance of alcohol addiction, and has often been measured with a visual probe task, where reaction times are compared for probes replacing either a substancerelated cue or a neutral cue. Systematic low-level differences between image classes are a potential cause of low internal reliability of the probe task (Ataya et al., 2012). Moreover, it is unclear whether automatic attentional capture by low-level properties such as size and colour in the non-substance related image could reduce attentional bias to the alcohol-related cue. Here, alcohol-related attentional bias was assessed in moderate social drinkers by measuring reaction times to targets that replaced either an alcohol-related or a non-alcohol related (i.e., neutral) picture. All alcohol-related images were greyscale, and the neutral stimulus could be either greyscale (‘control’), in colour (‘colour’), or greyscale and 25% larger in size (‘25% larger size’). We found attentional bias towards the alcohol-related stimuli in the control and 25% larger size conditions, but not in the colour condition. The magnitude of attentional bias was significantly reduced in the colour condition compared to the control and 25% larger size conditions. These findings indicate that salient low-level features in the non-substance related cue, in particular colour, can reduce the effect of alcohol-related content on the allocation of alcohol drinkers’ attention. Further, the results highlight the need for image pairs in visual probe tasks to be closely matched on basic perceptual dimensions (AU)

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Modulation of spatial attention to visual targets by emotional environmental sounds

Previous research has shown that visual spatial attention can be modulated by emotional prosody cues, but it is not known whether such crossmodal modulation of visual attention is associated with the engagement or disengagement of attentional resources. To test this, we employed a modified spatial cueing task, where participants indicated whether a visual target appeared either on the left or the right, after hearing a spatially non-predictive peripheral sound. Prior studies using prosody cues have found that modulation of visual attention by emotional auditory cues was lateralized, but this may have been due to the speech content of the stimuli; here instead we used non-speech environmental sounds. The sound was either emotional (pleasant, unpleasant) or neutral, and was presented either on the same side as the visual target ('valid' trial) or on the opposite side ('invalid' trial). For the cue validity index (RT to invalid cue minus RT to valid cue), we found differences between emotional and neutral cues, but only for visual targets presented in the right hemifield; here the cue validity index was lower for unpleasant compared to neutral and pleasant cues. Absolute RTs for targets on the right were faster for invalid trials following unpleasant cues, compared to pleasant and neutral cues, indicating that the reduced cue validity effect was due to faster disengagement from unpleasant auditory cues. Further, our results show that the laterality effect is related to the emotional nature of the cues, rather than the speech content of the stimuli.(AU)

Modulation of spatial attention to visual targets by emotional environmental sounds

Previous research has shown that visual spatial attention can be modulated by emotional prosody cues, but it is not known whether such crossmodal modulation of visual attention is associated with the engagement or disengagement of attentional resources. To test this, we employed a modified spatial cueing task, where participants indicated whether a visual target appeared either on the left or the right, after hearing a spatially non-predictive peripheral sound. Prior studies using prosody cues have found that modulation of visual attention by emotional auditory cues was lateralized, but this may have been due to the speech content of the stimuli; here instead we used non-speech environmental sounds. The sound was either emotional (pleasant, unpleasant) or neutral, and was presented either on the same side as the visual target ('valid' trial) or on the opposite side ('invalid' trial). For the cue validity index (RT to invalid cue minus RT to valid cue), we found differences between emotional and neutral cues, but only for visual targets presented in the right hemifield; here the cue validity index was lower for unpleasant compared to neutral and pleasant cues. Absolute RTs for targets on the right were faster for invalid trials following unpleasant cues, compared to pleasant and neutral cues, indicating that the reduced cue validity effect was due to faster disengagement from unpleasant auditory cues. Further, our results show that the laterality effect is related to the emotional nature of the cues, rather than the speech content of the stimuli...

The time course of auditory-visual processing of speech and body actions: evidence for the simultaneous activation of an extended neural network for semantic processing.

An extensive network of cortical areas is involved in multisensory object and action recognition. This network draws on inferior frontal, posterior temporal, and parietal areas; activity is modulated by familiarity and the semantic congruency of auditory and visual component signals even if semantic incongruences are created by combining visual and auditory signals representing very different signal categories, such as speech and whole body actions. Here we present results from a high-density ERP study designed to examine the time-course and source location of responses to semantically congruent and incongruent audiovisual speech and body actions to explore whether the network involved in action recognition consists of a hierarchy of sequentially activated processing modules or a network of simultaneously active processing sites. We report two main results:1) There are no significant early differences in the processing of congruent and incongruent audiovisual action sequences. The earliest difference between congruent and incongruent audiovisual stimuli occurs between 240 and 280 ms after stimulus onset in the left temporal region. Between 340 and 420 ms, semantic congruence modulates responses in central and right frontal areas. Late differences (after 460 ms) occur bilaterally in frontal areas.2) Source localisation (dipole modelling and LORETA) reveals that an extended network encompassing inferior frontal, temporal, parasaggital, and superior parietal sites are simultaneously active between 180 and 420 ms to process auditory­visual action sequences. Early activation (before 120 ms) can be explained by activity in mainly sensory cortices. . The simultaneous activation of an extended network between 180 and 420 ms is consistent with models that posit parallel processing of complex action sequences in frontal, temporal and parietal areas rather than models that postulate hierarchical processing in a sequence of brain regions.

Reaction time facilitation for horizontally moving auditory-visual stimuli.

For moving targets, bimodal facilitation of reaction time has been observed for motion in the depth plane (C. Cappe, G. Thut, B. Romei, & M. M. Murray, 2009), but it is unclear whether analogous RT facilitation is observed for auditory-visual motion stimuli in the horizontal plane, as perception of horizontal motion relies on very different cues. Here we found that bimodal motion cues resulted in significant RT facilitation at threshold level, which could not be explained using an independent decisions model (race model). Bimodal facilitation was observed at suprathreshold levels when the RTs for suprathreshold unimodal stimuli were roughly equated, and significant RT gains were observed for direction-discrimination tasks with abrupt-onset motion stimuli and with motion preceded by a stationary phase. We found no speeded responses for bimodal signals when a motion signal in one modality was paired with a spatially co-localized stationary signal in the other modality, but faster response times could be explained by statistical facilitation when the motion signals traveled in opposite directions. These results strongly suggest that integration of motion cues led to the speeded bimodal responses. Finally, our results highlight the importance of matching the unimodal reaction times to obtain response facilitation for bimodal motion signals in the linear plane.