Premotor Theory Research Articles

Temporal order judgments and presaccadic shifts of attention: What can prior entry teach us about the premotor theory?

A temporal order judgment (TOJ) 2-alternative forced choice design was used to examine presaccadic shifts of attention. Prior work on the premotor theory of attention (PTA) has predominantly focused on single-target discrimination tasks as a tool to measure accuracy and shifts of attention. It is important to demonstrate that the PTA is effective across attentional tasks that have been shown to be reliable in other contexts. Therefore, it was decided to use a perceptual task that probes multiple locations simultaneously and can equally be used to examine spatial spread of attention in more detail. In typical TOJ studies, prior entry is the metric used to measure an attentional effect. Prior entry is the biasing of temporal perception toward an attentionally cued location. This generally manifests as observers processing events at the cued location more rapidly, altering their perspective of temporal order. Participants were required to prepare saccades toward one of four targets, two of which would light up either synchronously or sequentially after a GO signal but before saccadic execution. Results demonstrated that in conditions with critical stimulus onset asynchronies, saccade preparation had a significant effect on performance. Prior entry effects were observed at saccade congruent locations with probes at these locations being typically perceived earlier than probes presented at a neutral location. These effects were not observed in control trials without a saccade. A further spatial effect was demonstrated for the attentional modulation, suggesting that this effect is restricted predominantly to horizontal configurations. Overall, results demonstrated that presaccadic attention is effective at eliciting a prior entry effect in TOJ designs and that such effects are more pronounced when the probes are distributed across the two lateral hemifields.

What does it actually mean that Premotor Theory is about embodied attention?

ABSTRACT One of the most vigorously debated issues in attention labs concerns the nature of the coupling between the sensory-motor system and covert spatial attention. Proponents of the Premotor Theory of Attention (PToA) claim that attention should be accounted for in terms of motor preparation for goal-directed actions such as eye or hand movements. For others, it is a supramodal psychological entity that is independent of our sensorimotor machinery. Both parties also seek to articulate this controversy in terms of cognitive science as a question of whether attention is embodied or disembodied cognition. The PToA is thought to advocate the embodiment of attention. We, however, are inclined to think that a more nuanced view of this conceptual framework is needed to yield some insights into how radical it actually is in terms of embodied cognition (EC). We argue that PToA still seems to bear some features of weak embodiment. Yet we suggest that it has the potential to build a stronger concept of attention as EC, but somewhat paradoxically this would require giving attention deflationary treatment and reconstructing it in other terms. We propose that the notion of pre-reflective intentionality might serve as an inspiration to this end.

Congruent movement training as a rehabilitation method to ameliorate symptoms of neglect–proof of concept

Stroke patients with visuospatial neglect (VSN) have difficulties responding to visual information located in the contralesional hemifield, affecting many daily life activities (ADL) such as eating, reading and mobility. Visual Scanning Therapy (VST) is widely used in clinical practice to ameliorate symptoms of VSN. Yet, not all patients benefit from this training and many training sessions are needed in order to achieve stable results. One potentially promising improvement to the VST is based on the theory that different effectors of the motor systems (e.g., eyes, hands) independently allocate attention during the programming of the movement (i.e., Pre Motor Theory of Attention (PMT)). Here, we studied this direct implementation of the PMT and tested whether a congruent movement training (CMT: congruent -i.e., executed at the same time to the same location-eye and pointing movements) is more effective to attenuate symptoms of neglect compared to VST. This study can be seen as a proof of concept. Attenuation of neglect symptoms was found in the CMT group after just 5 h of training in the subacute phase of neglect. In contrast, no training effects were found in the VST group. These findings indicate the potential of CMT which is a minimal –yet crucial-upgrade of the standard VST protocol that can be easily implemented in the clinic.

Visual selective attention and the control of tracking eye movements: a critical review.

People's eyes are directed at objects of interest with the aim of acquiring visual information. However, processing this information is constrained in capacity, requiring task-driven and salience-driven attentional mechanisms to select few among the many available objects. A wealth of behavioral and neurophysiological evidence has demonstrated that visual selection and the motor selection of saccade targets rely on shared mechanisms. This coupling supports the premotor theory of visual attention put forth more than 30 years ago, postulating visual selection as a necessary stage in motor selection. In this review, we examine to which extent the coupling of visual and motor selection observed with saccades is replicated during ocular tracking. Ocular tracking combines catch-up saccades and smooth pursuit to foveate a moving object. We find evidence that ocular tracking requires visual selection of the speed and direction of the moving target, but the position of the motion signal may not coincide with the position of the pursuit target. Further, visual and motor selection can be spatially decoupled when pursuit is initiated (open-loop pursuit). We propose that a main function of coupled visual and motor selection is to serve the coordination of catch-up saccades and pursuit eye movements. A simple race-to-threshold model is proposed to explain the variable coupling of visual selection during pursuit, catch-up and regular saccades, while generating testable predictions. We discuss pending issues, such as disentangling visual selection from preattentive visual processing and response selection, and the pinpointing of visual selection mechanisms, which have begun to be addressed in the neurophysiological literature.

To the edge of gaze and beyond: Visual distraction outside the oculomotor range

Neurophysiological studies demonstrated that attentional orienting is performed by fronto-parietal brain areas which also play an important role in oculomotor control (e.g. LIP, FEF). Accordingly, several studies claimed that exogenous attention can only be allocated to where we can potentially make an eye movement, i.e. within the oculomotor range. We tested this assumption by assessing the disruptive effect of a salient distractor at locations within and beyond participants' oculomotor range. Participants rotated their heads ~38° leftwards to prevent them from performing large rightward saccades. The required head rotation angle was determined individually prior to the experiment and monitored with an electromagnetic motion tracking device. In this posture, participants fixated the screen center and focused their attention on a location on the left side of the screen, where they had to discriminate the orientation of a visual noise patch. While assessing visual orientation sensitivity — an established proxy of visual attention — at this endogenously attended location, we flashed a salient cue either at the attended location or at various locations inside or outside their oculomotor range. We found that whenever the salient cue occurred at a location other than the endogenously attended location, it withdrew visual attention and significantly hampered endogenous attentional orienting. Crucially, this disruptive effect occurred regardless of whether the cue was presented within or beyond participants' oculomotor range, demonstrating that exogenous events equally grab our attention both inside and outside the oculomotor range. Since spatial exogenous attention was attracted unrestrictedly toward locations to which no saccade could be executed, the coupling of attention and eye movement control presumably is less tight than, for example, the prominent Premotor Theory of Attention would suggest. Rather, attention can be shifted freely over the entire visual range, independent of pathological and physiological limitations of the eye movement system.

Preparation of saccade sequences and eye programming affect endogenous covert attention.

Endogenous attention can be allocated in parallel to at least two saccade target locations of a planned sequence, but attentional resources are larger in the location of the first than the second saccade. The meridian effect that is observed in endogenous attention can be explained by eye programming, but it is not known how eye-movement preparation and eye programming can together affect endogenous attention during sequential saccades. We used a double-task paradigm to investigate this issue. In two experiments, we confirmed the relation between the preparation of sequential saccades and attentional selection and also showed that eye programming could eliminate deterioration of attentional resources in the second saccade location. The finding of the meridian effect in both the saccadic task and the target discrimination task additionally indicates the important role of eye programming in endogenous attention. The results were discussed in terms of the Premotor Theory of Attention.

Inducing oculomotor plasticity to disclose the functional link between voluntary saccades and endogenous attention deployed perifoveally

To what extent oculomotor and attention systems are linked remains strongly debated. Previous studies suggested that saccadic adaptation, a well-studied model of oculomotor plasticity, and orienting of attention rely on overlapping networks in the parietal cortex and can functionally interact. Using a Posner-like paradigm in healthy human subjects, we demonstrate for the first time that saccadic adaptation boosts endogenous attention orienting. Indeed, the discrimination of perifoveal targets benefits more from central cues after backward adaptation of leftward voluntary saccades than after a control saccade task. We propose that the overlap of underlying neural networks actually consists of neuronal populations co-activated by oculomotor plasticity and endogenous attention deployed perifoveally. The functional coupling demonstrated here plaids for conceptual models not belonging to the framework of the premotor theory of attention as the latter has been rejected precisely for this voluntary/endogenous modality. These results also open new perspective for rehabilitation of visuo-attentional deficits.

Associations and Dissociations between Oculomotor Readiness and Covert Attention.

The idea that covert mental processes such as spatial attention are fundamentally dependent on systems that control overt movements of the eyes has had a profound influence on theoretical models of spatial attention. However, theories such as Klein’s Oculomotor Readiness Hypothesis (OMRH) and Rizzolatti’s Premotor Theory have not gone unchallenged. We previously argued that although OMRH/Premotor theory is inadequate to explain pre-saccadic attention and endogenous covert orienting, it may still be tenable as a theory of exogenous covert orienting. In this article we briefly reiterate the key lines of argument for and against OMRH/Premotor theory, then evaluate the Oculomotor Readiness account of Exogenous Orienting (OREO) with respect to more recent empirical data. These studies broadly confirm the importance of oculomotor preparation for covert, exogenous attention. We explain this relationship in terms of reciprocal links between parietal ‘priority maps’ and the midbrain oculomotor centres that translate priority-related activation into potential saccade endpoints. We conclude that the OMRH/Premotor theory hypothesis is false for covert, endogenous orienting but remains tenable as an explanation for covert, exogenous orienting.

Is the premotor theory of attention essentially about pre-reflective intentionality?

The Premotor Theory of Attention (PToA) is a prominent, albeit controversial, modern experimental account of attentional processes. According to the PToA, motor preparation is both necessary and sufficient for spatial attention. Explaining the cognitive process of attention in terms of sensori-motor machinery can be considered as embedded in the idea of embodied cognition. The vocabulary adopted by the PToA seems to bear a particular resemblance to Merleau-Ponty’s phenomenological notion of pre-reflective intentionality. He articulates it by means of directness towards the lived world, which is constituted in the spatial motility of the body-subject. In this epistemological state of affairs, we come up with two leading questions: (a) can the main tenets of PToA be essentially reconstructed in terms of the notion of pre-reflective intentionality and since the bodily motility is meant by the French phenomenologist to be at the root of all forms of intentionality, (b) can the PToA be expanded to account for all kinds of attention? In conclusion, we advocate a positive answer for the former question and point to serious doubts as to why it can rather not be retained regarding the latter.

Covert attention beyond the range of eye-movements: Evidence for a dissociation between exogenous and endogenous orienting

The relationship between covert shift of attention and the oculomotor system has been the subject of numerous studies. A widely held view, known as Premotor Theory, is that covert attention depends upon activation of the oculomotor system. However, recent work has argued that Premotor Theory is only true for covert, exogenous orienting of attention and that covert endogenous orienting is largely independent of the oculomotor system. To address this issue we examined how endogenous and exogenous covert orienting of attention was affected when stimuli were presented at a location outside the range of saccadic eye movements. Results from Experiment 1 showed that exogenous covert orienting was abolished when stimuli were presented beyond the range of saccadic eye movements, but preserved when stimuli were presented within this range. In contrast, in Experiment 2 endogenous covert orienting was preserved when stimuli appeared beyond the saccadic range. Finally, Experiment 3 confirmed the observations of Exp.1 and 2. Our results demonstrate that exogenous, covert orienting is limited to the range of overt saccadic eye movements, whereas covert endogenous orienting is not. These results are consistent with a weak, exogenous-only version of Premotor Theory.

Spatial and temporal dynamics of presaccadic attentional facilitation before pro- and antisaccades.

The premotor theory of attention and the visual attention model make different predictions about the temporal and spatial allocation of presaccadic attentional facilitation. The current experiment investigated the spatial and temporal dynamics of presaccadic attentional facilitation during pro- and antisaccade planning; we investigated whether attention shifts only to the saccade goal location or to the target location or elsewhere, and when. Participants performed a dual-task paradigm with blocks of either anti- or prosaccades and also discriminated symbols appearing at different locations before saccade onset (measure of attentional allocation). In prosaccades blocks, correct prosaccade discrimination was best at the target location, while during errors, discrimination was best at the location opposite to the target location. This pattern was inversed in antisaccades blocks, although discrimination remained high opposite to the target location. In addition, we took the benefit of a large range of saccadic landing positions and showed that performance across both types of saccades was best at the actual saccade goal location (where the eye will actually land) rather than at the instructed position. Finally, temporal analyses showed that discrimination remained highest at the saccade goal location, from long before to closer to saccade onset, increasing slightly for antisaccades closer to saccade onset. These findings are in line with the premises of the premotor theory of attention, showing that attentional allocation is primarily linked both temporally and spatially to the saccade goal location.

Visual attention is not deployed at the endpoint of averaging saccades.

The premotor theory of attention postulates that spatial attention arises from the activation of saccade areas and that the deployment of attention is the consequence of motor programming. Yet attentional and oculomotor processes have been shown to be dissociable at the neuronal level in covert attention tasks. To investigate a potential dissociation at the behavioral level, we instructed human participants to move their eyes (saccade) towards 1 of 2 nearby, competing saccade targets. The spatial distribution of visual attention was determined using oriented visual stimuli presented either at the target locations, between them, or at several other equidistant locations. Results demonstrate that accurate saccades towards one of the targets were associated with presaccadic enhancement of visual sensitivity at the respective saccade endpoint compared to the nonsaccaded target location. In contrast, averaging saccades, landing between the 2 targets, were not associated with attentional facilitation at the saccade endpoint. Rather, attention before averaging saccades was equally deployed at the 2 target locations. Taken together, our results reveal that visual attention is not obligatorily coupled to the endpoint of a subsequent saccade. Rather, our results suggest that the oculomotor program depends on the state of attentional selection before saccade onset and that saccade averaging arises from unresolved attentional selection.

The effect of offset cues on saccade programming and covert attention.

Salient peripheral events trigger fast, “exogenous” covert orienting. The influential premotor theory of attention argues that covert orienting of attention depends upon planned but unexecuted eye-movements. One problem with this theory is that salient peripheral events, such as offsets, appear to summon attention when used to measure covert attention (e.g., the Posner cueing task) but appear not to elicit oculomotor preparation in tasks that require overt orienting (e.g., the remote distractor paradigm). Here, we examined the effects of peripheral offsets on covert attention and saccade preparation. Experiment 1 suggested that transient offsets summoned attention in a manual detection task without triggering motor preparation planning in a saccadic localisation task, although there were a high proportion of saccadic capture errors on “no-target” trials, where a cue was presented but no target appeared. In Experiment 2, “no-target” trials were removed. Here, transient offsets produced both attentional facilitation and faster saccadic responses on valid cue trials. A third experiment showed that the permanent disappearance of an object also elicited attentional facilitation and faster saccadic reaction times. These experiments demonstrate that offsets trigger both saccade programming and covert attentional orienting, consistent with the idea that exogenous, covert orienting is tightly coupled with oculomotor activation. The finding that no-go trials attenuates oculomotor priming effects offers a way to reconcile the current findings with previous claims of a dissociation between covert attention and oculomotor control in paradigms that utilise a high proportion of catch trials.

Eye abduction reduces competition in the oculomotor system

It is well established that there is a tight coupling between covert attention and the eye movement system. It is not yet clear whether there is a functional relationship between the two systems. Recent studies using the Posner cueing paradigm have demonstrated that preventing participants from executing a saccade reduces the attentional benefits associated with allocation of covert attention. One such technique involves abducting the eye in the orbit and presenting the stimuli outside of the effective oculomotor range (Craighero et al., 2004). In the present study we used saccadic curvature to examine whether eye abduction also reduces the competition in the oculomotor system. Saccadic curvature arises from competition within the oculomotor map when a visual distractor competes with the target. Typically, this causes saccades to curve away from the distractor. We experimentally reduced the ability to execute saccades by abducting the eye 30° into the temporal hemifield (monocular vision). This way the peripheral part of the temporal hemifield was located outside of the oculomotor range. Participants made a vertical eye movement while on some trials a distractor was shown either at a close or remote location in one of the hemifields. The results showed a decrease in curvature away from distractors located outside the oculomotor range. However, no such decrease was observed in the nasal hemifield, where saccade planning was unaffected. The results demonstrate that the inability to plan a saccade results in a decrease of distractor evoked activity in the oculomotor system even when the retinal stimulation is kept the same. The results are consistent with the premotor theory, which proposes that attention has emerged as an unavoidable consequence of movement planning. Meeting abstract presented at VSS 2016

Using temporally aligned event-related potentials for the investigation of attention shifts prior to and during saccades

According to the pre-motor theory of attention, attention is shifted to a saccade's landing position before the saccade is executed. Such pre-saccadic attention shifts are usually studied in psychophysical dual-task conditions, with a target-discrimination task before saccade onset. Here, we present a novel approach to investigate pre-saccadic attention shifts with the help of event-related potentials (ERPs). Participants executed one or two saccades to color-defined targets while ERPs and eye-movements were recorded. In single-target blocks participants executed a single saccade. In two-targets blocks participants made either a single saccade to one of the targets, or two successive saccades to both targets. Importantly, in two-targets blocks, targets could appear on the same or on opposite sides of the vertical midline. This allowed us to study contra-to-ipsilateral ERP differences (such as the N2pc or PCN) that reflect attention shifts to the targets, prior to saccade onset and during saccades. If pre-saccadic attention shifts to saccade target locations are necessary for saccade execution and if searched-for saccade targets capture attention, there should be enhanced attentional competition (1) between two targets compared to single targets; (2) between two opposite-sides targets compared to two same-side targets; and (3) in two saccades rather than one saccade conditions: More attentional competition was expected to delay saccade latency and to weaken pre-saccadic laterality effects in ERPs. Hypotheses were tested by means of temporally aligned ERPs that were simultaneously time-locked to stimulus onsets, saccade onsets, and saccade offsets. Predictions (1) and (2) were partly and fully confirmed, respectively, but no evidence was found for (3). We explain the implications of our results for the role of attention during saccade preparation, and we point out how temporally aligned ERPs compare to ICA-based electroencephalogram (EEG) artifact correction procedures and to psychophysical dual-task approaches.

There is no attentional global effect: Attentional shifts are independent of the saccade endpoint.

Many studies have found a strong coupling between selective attention and eye movements. The premotor theory of attention suggests that saccade preparation is directly responsible for such attentional shifts. While it has already been shown that the attentional shift is not directly coupled to the final stages of motor execution, it is currently unknown to what aspect of the earlier stages of saccade preparation the attentional shift is coupled. An important step in this preparation process is resolving the landing point when multiple elements compete for the saccade. Here we ask how such a competition influences the presaccadic attentional locus and whether the presaccadic shift of attention is coupled to the saccade landing position or the possible saccade goals. To this end, we adopt a global effect paradigm where a target is accompanied by a salient distractor resulting in the majority of eye movements landing in between target and distractor. To determine the allocation of attention, participants are presented with a discrimination task shortly before the execution of the saccade. Despite a strong global effect obtained for saccade endpoints, we find little evidence for attentional facilitation at the location between target and distractor, but strong attentional facilitation at the location of the target and distractor. We argue that attention is coupled to active oculomotor programs, but not part of the resolution of these programs towards the execution of the saccade.

The role of the oculomotor system in covert social attention.

Observing a change in gaze direction triggers a reflexive shift of attention and appears to engage the eye-movement system. However, the functional relationship between social attention and this oculomotor activation is unclear. One extremely influential hypothesis is that the preparation of a saccadic eye movement is necessary and sufficient for a covert, reflexive shift of attention (the premotor theory of attention; Rizzolatti et al., 1994). Surprisingly, this theory has not been directly tested with respect to reflexive gaze cueing. In order to address this issue, gaze cueing, peripheral cueing, and arrow cueing were examined under conditions in which some stimuli appeared at locations that could not become the goal of a saccadic eye movement. It was observed that peripheral cues failed to elicit reflexive attentional orienting when targets appeared beyond the range of eye movements. Similarly, nonpredictive arrow cues were ineffective when targets could not become the goal of a saccade. In contrast, significant gaze-cueing effects were still observed when targets were beyond the range of eye movements. These data demonstrate that the mechanisms involved in gaze cueing are dissociated from those involved in exogenous orienting to peripheral or arrow cues. Furthermore, the findings suggest that, unlike peripheral cueing and reflexive arrow cueing, gaze cueing is independent of oculomotor control. We conclude that the premotor theory does not offer a compelling explanation for gaze cueing.

Look where you’re going! Perceptual attention constrains the online guidance of action

Action guidance, like perceptual discrimination, requires selective attention. Perception is enhanced at the target of a reaching movement, but it is not known whether selecting an object for perception reciprocally prioritises it for action. Two theoretical frameworks, the premotor theory and the Visual Attention Model, predict that this reciprocal relation should hold. We tested the influence of perceptual attention on the online control of reaching. In Experiment 1, participants attended covertly to a flanker on one or other side of a fixated target, prior to reaching for that target, which occasionally jumped, after reach onset, to the attended or non-attended side. Participants corrected their reaches for almost all target jumps. In Experiment 2, we required covert monitoring of the flanker during reaching. This concurrent perceptual task globally reduced correction behaviour, indicating that perception and action share a common attentional resource. Corrections were especially unlikely toward the attended side. This is explained by assuming that perceptual attention primed an action toward the attended location and that the participant inhibited this primed action. The data thus imply that perceptual selection constrains online action guidance, as predicted by the premotor theory and the VAM. We further argue that the fact that participants can inhibit a location within the action system but simultaneously maintain its prioritisation for perceptual monitoring, is easier to reconcile with the VAM than with the premotor theory.

Counterproductive effect of saccadic suppression during attention shifts.

During saccadic eye movements, the processing of visual information is transiently interrupted by a mechanism known as “saccadic suppression” [1] that is thought to ensure perceptual stability [2]. If, as proposed in the premotor theory of attention [3], covert shifts of attention rely on sub-threshold recruitment of oculomotor circuits, then saccadic suppression should also occur during covert shifts. In order to test this prediction, we designed two experiments in which participants had to orient towards a cued letter, with or without saccades. We analyzed the time course of letter identification score in an “attention” task performed without saccades, using the saccadic latencies measured in the “saccade” task as a marker of covert saccadic preparation. Visual conditions were identical in all tasks. In the “attention” task, we found a drop in perceptual performance around the predicted onset time of saccades that were never performed. Importantly, this decrease in letter identification score cannot be explained by any known mechanism aligned on cue onset such as inhibition of return, masking, or microsaccades. These results show that attentional allocation triggers the same suppression mechanisms as during saccades, which is relevant during eye movements but detrimental in the context of covert orienting.

Shifts in spatial attention predict decisions for voluntary action

Event Abstract Back to Event Shifts in spatial attention predict decisions for voluntary action Jeff Bednark1*, Michelle Steffens1 and Ross Cunnington1 1 Queensland Brain Institute, Australia Background: Preparatory brain activity begins up to several seconds before the decision to move is consciously perceived. Previous studies have identified brain areas outside of the motor regions that can predict voluntary movement selection. However, it is unclear which non-motor processes underlie this early predictive activity. In the present study, we test the premotor theory of attention, which asserts that covert spatial attention and motor preparation arise from similar neural substrates. Methods: Functional magnetic resonance imaging (fMRI) was used to investigate the degree of similarity between patterns of neural activity associated with covert shifts in spatial attention and voluntary movement selection. Twenty-four healthy right-handed adults participated in two tasks during brain scanning. To assess spatial attention, participants were cued to direct and hold attention to either their left or right hand, in order to detect frequency changes in vibrotactile stimuli on that hand. This allowed us to identify the pattern of neural activation representing shifts of spatial attention to the left hand and to the right hand. To assess motor activation, participants performed a voluntary action task, in which they freely selected whether to make a button-press with their left or right index finger. Crucially, we then used a form of multivariate pattern analysis, based on fMRI activation Similarity Index, to test whether decisions to move the left hand or right hand in the motor task could be predicted from patterns of activation associated with attending to the left hand or the right hand in the spatial attention task. Results: Analysis revealed that patterns of neural activity associated with covert spatial attention to the cued hand and movements performed on the same side (i.e. attention left and movement left) had a significantly higher Similarity Index than movements performed on the opposite side (i.e. attention left and movement right). Discussion: Our results support the premotor theory of attention. Results suggest that neural processes associated with shifts in spatial attention to the left or right hand also occur when preparing voluntary actions and are predictive of decisions of which hand participants ultimately move. Thus, it appears that spatial attentional processes are a crucial part of voluntary movement selection and performance. Keywords: premotor theory of attention, voluntary movement, fMRI, representational similarity, multivoxel pattern analysis Conference: ACNS-2013 Australasian Cognitive Neuroscience Society Conference, Clayton, Melbourne, Australia, 28 Nov - 1 Dec, 2013. Presentation Type: Oral Topic: Motor Citation: Bednark J, Steffens M and Cunnington R (2013). Shifts in spatial attention predict decisions for voluntary action. Conference Abstract: ACNS-2013 Australasian Cognitive Neuroscience Society Conference. doi: 10.3389/conf.fnhum.2013.212.00185 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 15 Oct 2013; Published Online: 25 Nov 2013. * Correspondence: Dr. Jeff Bednark, Queensland Brain Institute, Brisbane, Australia, j.g.bednark@gmail.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Jeff Bednark Michelle Steffens Ross Cunnington Google Jeff Bednark Michelle Steffens Ross Cunnington Google Scholar Jeff Bednark Michelle Steffens Ross Cunnington PubMed Jeff Bednark Michelle Steffens Ross Cunnington Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.