Alexander Jones

Neural correlates of endogenous attention, exogenous attention and inhibition of return in touch.

Selective attention helps process the myriad of information constantly touching our body. Both endogenous and exogenous mechanisms are relied upon to effectively process this information; however, it is unclear how they relate in the sense of touch. In three tasks we contrasted endogenous and exogenous event‐related potential (ERP) and behavioural effects. Unilateral tactile cues were followed by a tactile target at the same or opposite hand. Clear behavioural effects showed facilitation of expected targets both when the cue predicted targets at the same (endogenous predictive task) and opposite hand (endogenous counter‐predictive task), and these effects also correlated with ERP effects of endogenous attention. In an exogenous task, where the cue was non‐informative, inhibition of return (IOR) was observed. The electrophysiological results demonstrated early effects of exogenous attention followed by later endogenous attention modulations. These effects were independent in both the endogenous predictive and exogenous tasks. However, voluntarily directing attention away from a cued body part influenced the early exogenous marker (N80). This suggests that the two mechanisms are interdependent, at least when the task requires more demanding shifts of attention. The early marker of exogenous tactile attention, the N80, was not directly related to IOR, which may suggest that exogenous attention and IOR are not necessarily two sides of the same coin. This study adds valuable new insight into how we process and select information presented to our body, showing both independent and interdependent effects of endogenous and exogenous attention in touch.

The interaction between attention and motor prediction. An ERP study.

Performing a voluntary action involves the anticipation of the intended effect of that action. Interaction with the environment also requires the allocation of attention. However, the effects of attention upon motor predictive processes remain unclear. Here we use a novel paradigm to investigate attention and motor prediction orthogonally. In an acquisition phase, high and low tones were associated with left and right key presses. In the following test phase, tones were presented at random and participants attended to only one ear whilst ignoring tones presented in the unattended ear. In the test phase a tone could therefore be presented at the attended or unattended ear, as well as being congruent or incongruent with prior action-effect learning. We demonstrated early and late effects of attention as well as a later independent motor prediction effect with a larger P3a for incongruent tones. Interestingly, we demonstrated an intermediate interaction, showing an action-effect negativity (NAE) for tones which were unattended, whilst no motor prediction effect was found for attended tones. This interaction pattern suggests that attention and motor prediction are not opposing processes but can both operate to modulate prediction, providing valuable new insight into the relationship between attention and the effects of motor prediction.

Independent effects of bottom-up temporal expectancy and top-down spatial attention. An audiovisual study using rhythmic cueing

Selective attention to a spatial location has shown enhanced perception and facilitate behavior for events at attended locations. However, selection relies not only on where but also when an event occurs. Recently, interest has turned to how intrinsic neural oscillations in the brain entrain to rhythms in our environment, and, stimuli appearing in or out of sync with a rhythm have shown to modulate perception and performance. Temporal expectations created by rhythms and spatial attention are two processes which have independently shown to affect stimulus processing but it remains largely unknown how, and if, they interact. In four separate tasks, this study investigated the effects of voluntary spatial attention and bottom-up temporal expectations created by rhythms in both unimodal and crossmodal conditions. In each task the participant used an informative cue, either color or pitch, to direct their covert spatial attention to the left or right, and respond as quickly as possible to a target. The lateralized target (visual or auditory) was then presented at the attended or unattended side. Importantly, although not task relevant, the cue was a rhythm of either flashes or beeps. The target was presented in or out of sync (early or late) with the rhythmic cue. Results showed participants were faster responding to spatially attended compared to unattended targets in all tasks. Moreover, there was an effect of rhythmic cueing upon response times in both unimodal and crossmodal conditions. Responses were faster to targets presented in sync with the rhythm compared to when they appeared too early in both crossmodal tasks. That is, rhythmic stimuli in one modality influenced the temporal expectancy in the other modality, suggesting temporal expectancies created by rhythms are crossmodal. Interestingly, there was no interaction between top-down spatial attention and rhythmic cueing in any task suggesting these two processes largely influenced behavior independently.

Reflexive attention in touch: an investigation of event related potentials and behavioural responses.

Exogenous attention has been extensively studied in vision but little is known about its behavioural and neural correlates in touch. To investigate this, non-informative tactile cues were followed after 800 ms by tactile targets and participants either detected targets or discriminated their location. Responses were slowed for targets at cued compared to uncued locations (i.e. inhibition of return (IOR)) only in the detection task. Concurrently recorded ERPs showed enhanced negativity for targets at uncued compared to cued locations at the N80 component and this modulation overlapped with the P100 component but only for the detection task indicating IOR may, if anything, be linked to attentional modulations at the P100. Further, cue-target interval analysis showed an enhanced anterior negativity contralateral to the cue side in both tasks, analogous to the anterior directed attention negativity (ADAN) previously only reported during endogenous orienting.

Lost in vision: ERP correlates of exogenous tactile attention when engaging in a visual task.

Behavioural studies have shown that when engaging in a visual task response facilitation to tactile stimuli at exogenously cued locations is diminished. Here we investigated behavioural and also neural correlates of tactile exogenous attention when participants either watched a visual stream (single task) or also detected targets in the visual stream (dual task). During the visual stream, tactile cues were presented to the left or right hand followed by tactile targets at the same or opposite hand. Behavioural results demonstrated slowed responses to tactile targets at cued locations (i.e., IOR) in the single whilst no attention effect in the dual task. Concurrently recorded EEG revealed multiple stages of tactile processing to be attenuated when engaging in a visual task: First, the amplitude of the cueelicited somatosensory P100 component was suppressed suggesting relative early cross-modality effects in the dual task. Second, correlates of cue-induced attentional control processes showed a reduced late somatosensory negativity (LSN) in the dual compared to the single task suggesting smaller preparatory processes. Finally, early attentional selection correlates of post-target ERPs (N80) were absent in the dual task. This study demonstrated for the first time that engaging in a visual task abolished behavioural IOR in touch. ERP analyses showed that early somatosensory processing as well as specific correlates of tactile attentional orienting and target selection are diminished under visual engagement. Our findings are in line with a supramodal account of attention.

Independent effects of endogenous and exogenous attention in touch.

Abstract Endogenous and exogenous attention in touch have typically been investigated separately. Here we use a double-cueing paradigm manipulating both types of orienting in each trial. Bilateral endogenous cues induced long-lasting facilitation of endogenous attention up to 2 s. However, the exogenous cue only elicited an effect at short intervals. Our results favour a supramodal account of attention and this study provides new insight into how endogenous and exogenous attention operates in the tactile modality.

Temporal expectancies driven by self- and externally generated rhythms

&NA; The dynamic attending theory proposes that rhythms entrain periodic fluctuations of attention which modulate the gain of sensory input. However, temporal expectancies can also be driven by the mere passage of time (foreperiod effect). It is currently unknown how these two types of temporal expectancy relate to each other, i.e. whether they work in parallel and have distinguishable neural signatures. The current research addresses this issue. Participants either tapped a 1 Hz rhythm (active task) or were passively presented with the same rhythm using tactile stimulators (passive task). Based on this rhythm an auditory target was then presented early, in synchrony, or late. Behavioural results were in line with the dynamic attending theory as RTs were faster for in‐ compared to out‐of‐synchrony targets. Electrophysiological results suggested self‐generated and externally induced rhythms to entrain neural oscillations in the delta frequency band. Auditory ERPs showed evidence of two distinct temporal expectancy processes. Both tasks demonstrated a pattern which followed a linear foreperiod effect. In the active task, however, we also observed an ERP effect consistent with the dynamic attending theory. This study shows that temporal expectancies generated by a rhythm and expectancy generated by the mere passage of time can work in parallel and sheds light on how these mechanisms are implemented in the brain. HighlightsTemporal expectancies can be driven by rhythms or by the mere passage of time.We conceived a paradigm using EEG that tests for both these forms of expectancy.We compared self‐generated and externally generated rhythms.We found evidence for both expectancy processes working in parallel.

The attentive homunculus: ERP evidence for somatotopic allocation of attention in tactile search

Our brain constantly receives tactile information from the bodys surface. We often only become aware of this information when directing our attention towards the body. Here, we report a study investigating the behavioural and neural response when selecting a target amongst distractor vibrations presented simultaneously to several locations either across the hands or body. Comparable visual search studies have revealed the N2pc as the neural correlate of visual selective attention. Analogously, we describe an enhanced negativity contralateral to the tactile target side. This effect is strongest over somatosensory areas and lasts approximately 200ms from the onset of the somatosensory N140 ERP component. Based on these characteristics we named this electrophysiological signature of attentional tactile target selection during tactile search the N140-central-contralateral (N140cc). Furthermore, we present supporting evince that the N140cc reflects attentional enhancement of target rather than suppression of distractor locations; the component was not reliably altered by distractor but rather by target location changes. Taken together, our findings present a novel electrophysiological marker of tactile search and show how attentional selection of touch operates by mainly enhancing task relevant locations within the somatosensory homunculus.

Body in mind.

The sense of touch is imperative in cognition, development, and for how we perceive the world and interact with others. The skin envelopes our body and is our largest organ providing us with information about our immediate environment. In addition to this “surface” information, our somatosensory system also processes information regarding body position and internal bodily states. The importance of processing information to our body is unlikely to be disputed, however, relatively little research has focused on the somatosensory system and the body sense as compared to vision and audition. The last two decades have however seen an increased interest in the body sense from a range of different perspectives, using different methodologies which this research topic aimed to reflect. The broad range of unanswered research questions relating to the body is also mirrored by the contributions in this research topic. We are constantly bombarded with tactile information, such as from the clothes on our body, or the chair we sit upon, yet we are able to process only what is relevant to us. Mechanisms of selective attentions help to prioritize, predict and select information relevant to the situation and to guide our behavior. Selectively attending to a location on the body has repeatedly shown to enhance processing of stimuli at attended over unattended location (e.g., Jones and Forster, 2014). In this research topic, Tame et al. (2014) showed that detection of a tactile stimulus is dependent upon concurrent presented stimuli which may act as a detection mask, even though the mask is presented at different fingers or hands. Somatosensory information is not typically presented in isolation but the sense of touch is also integrated with other modalities (for an overview see Calvert et al., 2004). Using event-related potentials (ERPs), Staines et al. (2014) showed how visual information relevant to movements modulates somatosensory processing. In a comprehensive review, Heed and Azanon, 2014) explored the findings of how we localize touch to our body. Touch can be localized both using somatotopic but also external coordinates. That is, where on the skin was the stimulus, or where based on external spatial co-ordinates did the tactile stimulus appear. Their overview focuses on how temporal order judgment (TOJ) tasks have been a fruitful paradigm to investigate tactile spatial processing. External and somatotopic maps were also shown, using ERPs, to be affected by where vision is directed (Gherri and Forster, 2014). Observing others being touched as well as the social aspect of touch are important parts of everyday life and this has also recently attracted increased research interest. In particular, in this research topic Gillmeister (2014) introduced a new behavioral paradigm to measure how observing touch on another persons hand influences the perception of ones own touch. Moreover, Farmer et al. (2014) showed how induced changes in body ownership through observation of touch applied to another persons hand of a different skin color can modulate social attitudes. A similar emerging and interesting research area, briefly covered in this research topic, is how we use interoceptive cues and how the sense of self develops (Sel, 2014). Last but not least, a study investigating the touch and weight perception on aesthetic appreciation points to an important role of ones own body perception in aesthetic perception (Yamada et al., 2014). Together, these recent, seemingly divers studies could fall under the term embodied cognition which now encompasses seemingly diverse fields of psychology highlighting the influence of the body in mind on cognition in general. This research topic brings together both research from well-established paradigms and research areas as well as highlighting how the body and the sense of touch is also being explored in new ways. The contributions here show there are a broad range of perspectives and questions to be addressed when processing stimuli to and within our body. The increased interest in the sense of touch over the last decades will hopefully continue as much still remains to be explored.

Motor-evoked potentials reveal a motor-cortical readout of evidence accumulation for sensorimotor decisions.

Many everyday activities, such as driving and sports, require us to engage in time-pressured sensorimotor decision making in response to visual cues. The computational principle of continuous evidence accumulation is the dominant account underlying models of speeded decision making, but the nature and locus of the decision variable that triggers action is debated. Traditionally, cognitive stages such as perception, stimulus-response translation, and the generation of motor plans, have been considered to occur in series. However, this idea is challenged by neurophysiological work in animals, suggesting that cognitive operations are distributed across sensorimotor cortex. Here, we investigate whether a decision variable can be observed in the primary motor cortex (M1) of humans. Participants categorised faces as male or female, with task difficulty manipulated using natural or morphed stimuli. Transcranial magnetic stimulation, applied at random across the reaction-time interval, produced motor-evoked potentials (MEPs) in two hand muscles that were the major contributors when generating the correct and incorrect pinch/grip movements. MEP magnitudes reveal covert action preparation, even when no action is produced. Smoothing MEPs using a Gaussian kernel allowed us to recover a continuous time-varying MEP average, comparable to an EEG component, which permitted precise localisation of the time at which the motor plan for the responding muscle began to dominate over the non-responding action. This moment was calculated in both stimulus-locked and response-locked analyses, and was found to occur at the same time with stimulus locking, but earlier with response locking, when ambiguous stimuli made the decision more challenging. This pattern is consistent with M1 providing a continuous readout of evidence accumulation. We predicted the evidence accumulation profile from a drift diffusion model, using only behavioural data, and found a good qualitative match to the observed neurometric MEP profiles. Meeting abstract presented at VSS 2015.