Location but not amount of stimulus occlusion influences the stability of visuo-motor coordination

The current study examined whether the amount and location of available movement information influenced the stability of visuo-motor coordination. Participants coordinated a hand-held pendulum with an oscillating visual stimulus in an inphase and antiphase manner. The effects of occluding different amounts of phase at different phase locations were examined. Occluding the 0°/180° phase locations (end-points) significantly increased the variability of the visuo-motor coordination. The amount of occlusion had little or no affect on the stability of the coordination. We concluded that the end-points of a visual rhythm are privileged and provide access to movement information that ensures stable coordination. The results are discussed with respect to the proposal of Bingham and colleagues (e.g., Bingham GP. Ecol Psychol 16:45–53, 2004a; Wilson AD, Collins DR, Bingham GP. Exp Brain Res 165:351–361, 2005a) that the relevant information for rhythmic visual coordination is relative direction information.     

Location but not amount of stimulus occlusion influences the stability of visuomotor coordination

The current study examined whether the amount and location of available movement information influenced the stability of visuomotor coordination. Participants coordinated a handheld pendulum with an oscillating visual stimulus in an inphase and antiphase manner. The effects of occluding different amounts of phase at different phase locations were examined. Occluding the 0°/180° phase locations (end-points) significantly increased the variability of the visuomotor coordination. The amount of occlusion had little or no affect on the stability of the coordination. We concluded that the end-points of a visual rhythm are privileged and provide access to movement information that ensures stable coordination. The results are discussed with respect to the proposal of Bingham (Ecol Psychol 16:45–43, 2004) and Wilson et al. (Exp Brain Res 165:351–361, 2005) that the relevant information for rhythmic visual coordination is relative direction information.     

Stability of rhythmic visuo-motor tracking does not depend on relative velocity

It is well established that the in-phase pattern of bimanual coordination (i.e. a relative phase of 0°) is more stable than the antiphase pattern (i.e., a relative phase of 180°), and that a spontaneous transition from antiphase to in-phase typically occurs as the movement frequency is gradually increased. On the basis of results from relative phase perception experiments, Bingham (Proceedings of the 23rd annual conference of the cognitive science society. Laurence Erlbaum Associates, Mahwah, pp 75–79, 2001; Ecol Psychol 16:45–53, 2004; Advances in psychology 135: time-to-contact. Elsevier, Amsterdam, pp 421–442, 2004) proposed a dynamical model that consists of two phase driven oscillators coupled via the perceived relative phase, the resolution of which is determined by relative velocity. In the present study, we specifically test behavioral predictions from this last assumption during a unimanual visuo-motor tracking task. Different conditions of amplitudes and frequencies were designed to manipulate selectively relative phase and relative velocity. While the known effect of phase and frequency were observed, relative phase variability was not affected by the different conditions of relative velocity. As such, Bingham’s model assumption that instability in relative phase coordination is brought about by relative velocity that affects the resolution of the perceived relative phase has been invalidated for the case of rhythmic unimanual visuo-motor tracking. Although this does not rule out the view that relative phase production is constrained by relative phase perception, the mechanism that would be responsible for this phenomenon still has to be established.     

Locomotor behaviour of children while navigating through apertures

During everyday locomotion, we encounter a range of obstacles requiring specific motor responses; a narrow aperture which forces us to rotate our shoulders in order to pass through is one example. In adults, the decision to rotate their shoulders is body scaled (Warren and Whang in J Exp Psychol Hum Percept Perform 13:371–383, 1987), and the movement through is temporally and spatially tailored to the aperture size (Higuchi et al. in Exp Brain Res 175:50–59, 2006; Wilmut and Barnett in Hum Mov Sci 29:289–298, 2010). The aim of the current study was to determine how 8-to 10-year-old children make action judgements and movement adaptations while passing through a series of five aperture sizes which were scaled to body size (0.9, 1.1, 1.3, 1.5 and 1.7 times shoulder width). Spatial and temporal characteristics of movement speed and shoulder rotation were collected over the initial approach phase and while crossing the doorway threshold. In terms of making action judgements, results suggest that the decision to rotate the shoulders is not scaled in the same way as adults, with children showing a critical ratio of 1.61. Shoulder angle at the door could be predicted, for larger aperture ratios, by both shoulder angle variability and lateral trunk variability. This finding supports the dynamical scaling model (Snapp-Childs and Bingham in Exp Brain Res 198:527–533, 2009). In terms of movement adaptations, we have shown that children, like adults, spatially and temporally tailor their movements to aperture size.     

'Side-effects': intrinsic and task-induced asymmetry in bimanual rhythmic coordination

Multifrequency coordination studies have shown the importance of hand-role in addition to hand-preference in bimanual rhythmic coordination. In these studies, hand-role has been defined by the task of the individual hands (moving fast or slow). In the present study, the hands were coordinated at the same frequency and hand-role was defined by the asymmetry of the coordination pattern. Eleven consistent left-handers and 13 consistent right-handers tapped three patterns (anti-phase, left-gallop, right-gallop) in four visual feedback conditions (no feedback, left-hand feedback, right-hand feedback, full feedback). The analysis focused on phase shifts, phase variability, intertap interval variability, and correlations between intertap intervals. The manipulation of visual feedback had only minor effects. In the anti-phase pattern, a symmetric coupling mechanism was found. The results support the idea that coordination in the gallop pattern is governed by a hierarchical control mechanism. In contrast to the multifrequency studies, however, successful control in the gallop is not dependent on a hand arrangement that accommodates the preferred hand as the leading hand. An adjustment to the model of Summers et al. (1993, J Exp Psychol Hum Percept Perform 19:416–428) is presented for the case of the gallop pattern.     

Sound can improve visual search in developmental dyslexia

We examined whether developmental dyslexic adults suffer from sluggish attentional shifting (SAS; Hari and Renvall in Trends Cogn Sci 5:525–532, 2001) by measuring their shifting of attention in a visual search task with dynamic cluttered displays (Van der Burg et al. in J Exp Psychol Human 34:1053–1065, 2008). Dyslexics were generally slower than normal readers in searching a horizontal or vertical target among oblique distracters. However, the addition of a click sound presented in synchrony with a color change of the target drastically improved their performance up to the level of the normal readers. These results are in line with the idea that developmental dyslexics have specific problems in disengaging attention from the current fixation, and that the phasic alerting by a sound can compensate for this deficit.     

An anti-Hick’s effect for exogenous, but not endogenous, saccadic eye movements

Previously, we have shown that the reaction times (RTs) of exogenously generated saccadic eye movements decrease with an increase in the number of response alternatives (Lawrence et al. in J Vis 8(26):1–7, 2008; Lawrence and Gardella in Exp Brain Res 195(3):413–418, 2009). Because this pattern of RTs is in the direction opposite that predicted by Hick (Q J Exp Psychol 4:11–26, 1952), we termed the effect an “anti-Hick’s” effect. In the present study, we examined whether this effect characterizes saccades in general, or only those saccades that are exogenously generated. An anti-Hick’s effect was found for exogenous, but not for endogenous, saccades. These results demonstrate a clear dissociation between exogenously and endogenously generated saccades and place an important constraint on the anti-Hick’s effect.     

REM-dependent repair of competitive memory suppression

Memories are enhanced during sleep through memory consolidation processes. A recent study reported that sleep increases competitive forgetting in the absence of sleep-dependent consolidation of the target memory (Racsmany et al. in Psychol Sci 21:80–85, 2010). Here, using a modified retrieval-induced forgetting task, we examined whether sleep-dependent modulation of forgetting occurs concurrently with the consolidation of related target memories. Participants encoded a word-pair list and then practiced retrieving a portion of these pairs. Following a break with sleep or wake, recall of all pairs was tested. As expected, recall for practiced pairs was greater following sleep relative to wake. Contrary to Racsmany et al. (Psychol Sci 21:80–85, 2010), competitive forgetting decreased following sleep. Moreover, recall for practiced pairs correlated with slow wave sleep (SWS) while forgetting of competing targets correlated negatively with REM, suggesting a novel function of these sequential brain states on memory processing.     

Overlapping functional anatomy for working memory and visual search

Recent behavioural findings using dual-task paradigms demonstrate the importance of both spatial and non-spatial working memory processes in inefficient visual search (Anderson et al. in Exp Psychol 55:301–312, 2008). Here, using functional magnetic resonance imaging (fMRI), we sought to determine whether brain areas recruited during visual search are also involved in working memory. Using visually matched spatial and non-spatial working memory tasks, we confirmed previous behavioural findings that show significant dual-task interference effects occur when inefficient visual search is performed concurrently with either working memory task. Furthermore, we find considerable overlap in the cortical network activated by inefficient search and both working memory tasks. Our findings suggest that the interference effects observed behaviourally may have arisen from competition for cortical processes subserved by these overlapping regions. Drawing on previous findings (Anderson et al. in Exp Brain Res 180:289–302, 2007), we propose that the most likely anatomical locus for these interference effects is the inferior and middle frontal cortex of the right hemisphere. These areas are associated with attentional selection from memory as well as manipulation of information in memory, and we propose that the visual search and working memory tasks used here compete for common processing resources underlying these mechanisms.     

Perception of relative throw-ability

Bingham et al. (J Exp Psychol Hum Percept Perform 15(3):507–528, 1989) showed that skilled throwers can perceive optimal objects for throwing to a maximum distance. Zhu and Bingham (J Exp Psychol Hum Percept Perform 34(4):929, 2008, 36(4):862–875, 2010) replicated this finding and then showed that felt heaviness is used to perceive this affordance (see also Zhu and Bingham in Evol Hum Behav 32(4):288–293, 2011; Zhu et al. in Exp Brain Res 224(2):221–231, 2013). Throwers pick the best weight for spherical projectiles in each graspable size. Bingham et al. (J Exp Psychol Hum Percept Perform 15(3):507–528, 1989) speculated that relative throw-ability might be perceptible. This would mean that the ordering of distances achieved by maximum effort throws of different objects could be judged. This affordance property is not the same as optimal throw-ability, because it requires all projectiles to be evaluated relative to one another with respect to ordinally scaled distances, not just a discrete optimum. We now used a magnitude estimation task to test this hypothesis, comparing the resultant ordering with that exhibited by distances of throws in previous studies. The findings show that participants were able to perform the perceptual task. However, discrimination among objects of different weight within a size was better than between sizes. The implications of these results for understanding of the information used to perform this task are discussed.     

Placing order in space: the SNARC effect in serial learning

The SNARC effect, consisting of a systematic association between numbers and lateralized response, reflects the mental representation of magnitude along a left-to-right mental number line (Dehaene et al. in J Exp Psychol 122:371–396, 1993). Critically, this effect has been reported in the classification of overlearned non-numerical sequences such as letters, days and months (Gevers et al. in Cognition 87:B87–B95, 2003 and Cortex 40:171–172, 2004) suggesting that ordinal, rather than magnitude information, is critical for spatial coding. This study tests the hypothesis of an oriented spatial representation as the privileged way of mentally organizing serial information, by looking for stimulus–response compatibility effects in the processing of a newly acquired arbitrary sequence. Here we report an association between ordinal position of the items and spatial response preference for both order-relevant and order-irrelevant tasks. These results suggest that any ordered information, even when order is not intrinsically relevant to it, is spontaneously mapped in the representational space. This spatial representation is likely to acquire a left-to-right orientation, at least in western cultures.     

Saccades and reaches,behaving differently

Previously, we have shown, both in humans and monkeys, that the latencies of exogenously generated saccades decrease with an increase in the number of response alternatives (Lawrence et al. in J Vis 8:26, 1–7, 2008). Because this pattern of latencies was in the direction opposite that predicted by Hick (Q J Exp Psychol 4:11–26, 1952), we termed the effect an “anti-Hick’s” effect. In contrast, previous research has shown that reach latencies increase with an increase in response alternatives (e.g., Wright et al. in Exp Brain Res 179:475–496, 2007). Given that there are known interactions between the saccade and reach systems, we examined whether the direction of the relationship between latencies and response alternatives differed when saccades and reaches are concomitantly executed. Interestingly, we found that the pattern of latencies nevertheless persisted in a visually guided saccade and reach task. These results place an important constraint on the anti-Hick’s effect, suggesting not only that the effect is localized within the saccade system, but also that it is localized in the saccade system at a level in which saccade and reach signals do not interact.

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Temporal uncertainty does not affect response latencies of movements produced during startle reactions

Previous research has shown that a startle ‘go’ stimulus, presented at a constant latency with respect to a warning stimulus, is capable of eliciting an intended voluntary movement in a simple reaction time (RT) task at very short latencies without involvement of the cerebral cortex (Carlsen et al. in Exp Brain Res 152:510–518, 2003; J Motor Behav 36:253–264, 2004a; Exp Brain Res 159:301–309 2004b; Valls-Solé et al. in J Physiol 516:931–938, 1999). The purpose of the present experiment was to determine the effect of temporal uncertainty on response latency during an RT task that comprised a startle stimulus. Participants were required to perform an active 20° wrist extension movement in response to an auditory tone that was presented 2,500 to 5,500 ms after a warning stimulus, in 1,000 ms increments. On certain trials the control auditory stimulus (80 dB) was unexpectedly replaced by the startle stimulus (124 dB). When participants were startled the intended voluntary movement was initiated at approximately 70 ms, regardless of foreperiod duration. The magnitude and invariance of response latencies to the startle stimulus suggest that the intended movement had indeed been prepared prior to the arrival of the imperative go stimulus, within 2.5 s of the warning stimulus. Furthermore, there was no evidence that the prepared movement decayed over a period of at least 3 s.     

Bimanual Fitts’ tasks: Kelso,Southard, and Goodman, 1979 revisited

The experiment was designed to replicate and extend to an integrated feedback condition the pattern of movement time results found by Kelso et al. (J Exp Psychol Hum Percept Perform 5:229–238, 1979a, Science 204:1029–1031, 1979b) where the simultaneous movement of one hand to a low ID target and the other to a higher ID target indicated “a tight coordinate coupling between the hands” (p. 229). In the present experiment, a control group was provided feedback that depicted the independent movement of the two limbs under low and higher indexes of difficulty (ID). A Lissajous group was provided integrated feedback in the form of a Lissajous plot. The results indicated a pattern of results for the control and Lissajous groups similar to that found by Kelso et al. for one and two-limb movements to the same difficulty targets. The control group also replicated the finding for two-limb movements to mixed ID tasks. However, the Lissajous group simultaneously produced disparate movement in the mixed target conditions. The results are consistent with recent findings indicating that when provided salient integrated feedback participants can effectively produce disparate movements of the two limbs.     

Non-target flanker effects on movement in a virtual action centred reference frame

Visual selective attention is thought to underly inhibitory control during pointing movements. Accounts of inhibitory control during pointing movements make differential predictions about movement deviations towards or away from highly salient non-target flankers based on their potential cortical activation and subsequent inhibition: (1) Tipper et al. (Vis Cogn 4:1–38, 1997) “response vector model” predicts movements away from highly salient flankers; (2) Welsh and Elliott’s (Q J Exp Psychol 57:1031–1057, 2004a and J Mot Behav 36:200–211, 2004b) “response activation model” predicts movements towards highly salient flankers early in the response, that is resolved by a race for inhibition. To eliminate the confounds of physical properties, such as obstacle avoidance and information cues of non-target objects, pointing was conducted in a virtual environment (graphical user interface). Participants were 14 skilled computer users who moved a computer cursor with a mouse to virtual targets. Analysis revealed non-target flankers significantly interfered with movement consistent with action centred selective attention, and reflecting a proximity-to-hand effect. Spatial analysis revealed evidence of highly salient flankers attracting movement, and less salient flankers repelling movement, supporting Welsh and Elliott’s response activation model. These effects were achieved in a virtual 2D environment where interference caused by the physical properties of objects was less cogent.     

Inhibition of return in cue–target and target–target tasks

Inhibition of return (IOR), the term given for the slowing of a response to a target that appeared at the same location as a previously presented stimulus, has been studied with both target–target (TT; participants respond to each successive event) and cue–target (CT; participants only respond to the second of two events) tasks. Although both tasks have been used to examine the processes and characteristics of IOR, few studies have been conducted to understand if there are any differences in the processes that underlie the IOR that results from ignoring (CT paradigm) or responding to (TT paradigm) the first stimulus. The purpose of the present study was to examine the notion that IOR found in TT tasks represents “true” IOR whereas IOR found in CT tasks consist of both “true” IOR and response inhibition (Coward et al. in Exp Brain Res 155:124–128, 2004). Consistent with the pattern of effects found by Coward et al. (Exp Brain Res 155:124–128, 2004), IOR was larger in the CT task than in the TT task when a single detection response was required (Experiment 1). However, when participants completed one of two spatially-directed responses (rapid aiming movement to the location of the target stimulus), IOR effects from the CT and TT tasks were equal in magnitude (Experiment 2). Rather than CT tasks having an additional response inhibition component, these results suggest that TT tasks may show less of an inhibitory effect because of a facilitatory response repetition effect.     

Limitations of feedforward control in multiple-phase steering movements

When attempting to perform bi-phasic steering movements (such as a lane change) in the absence of visual and inertial feedback, drivers produce a systematic heading error in the direction of the lane change (Wallis et al., Curr Biol 12(4):295–299, 2002; J Exp Psychol Hum Percept Perform 33(55):1127–1144, 2007). Theories of steering control which employ exclusively open-loop control mechanisms cannot accommodate this finding. In this article we show that a similar steering error occurs with obstacle avoidance, and offer compelling evidence that it stems from a seemingly general failure of human operators to correctly internalise the dynamics of the steering wheel. With respect to lateral position, the steering wheel is an acceleration control device, but we present data indicating that drivers treat it as a rate control device. Previous findings from Wallis et al. can be explained the same way. Since an open-loop control mechanism will never succeed when the dynamics of the controller are internalised improperly, we go on to conclude that regular, appropriately timed sensory feedback—predominantly from vision—is necessary for regulating heading, even during well-practiced, everyday manoeuvres such as lane changing and obstacle avoidance.     

ABCC6 and pseudoxanthoma elasticum

ABCC6 belongs to the adenosine triphosphate-binding cassette (ABC) gene subfamily C. This protein family is involved in a large variety of physiological processes, such as signal transduction, protein secretion, drug and antibiotic resistance, and antigen presentation [Kool et al. (1999) 59:175–182; Borst and Elferink (2002) 71:537–592]. ABCC6 is primarily and highly expressed in the liver and kidney [Kool et al. (1999) 59:175–182; Bergen et al. (2000) 25:228–2231]. The precise physiological function and natural substrate(s) transported by ABCC6 are unknown, but the protein may be involved in active transport of intracellular compounds to the extracellular environment [Kool et al. (1999) 59:175–182] [Scheffer et al. (2002) 82:515–518]. Recently, it was shown that loss of function mutations in ABCC6 cause pseudoxanthoma elasticum (PXE) [Bergen et al. (2000) 25:228–2231; Le Saux et al. (2000) 25:223–227]. PXE is an autosomal recessively inherited multi-organ disorder [Goodman et al. (1963) 42:297–334; Lebwohl et al. (1994) 30:103–107]. PXE is primarily associated with the accumulation of mineralized and fragmented elastic fibers of the connective tissue in the skin [Neldner (1988) 6:1–159], Bruch’s membrane in the retina [Hu et al. (2003) 48:424–438], and vessel walls [Kornet et al. (2004) 30:1041–1048]. PXE patients usually have skin lesions and breaks in Bruch’s membrane of the retina (angioid streaks). Also, a variety of cardiovascular complications has been observed [Hu et al. (2003) 48:424–438]. Recently, a mouse model for PXE was created by targeted disruption of Abcc6 [Gorgels et al. (2005) 14:1763–1773; Klement et al. (2005) 25:8299–8310], which may be useful to elucidate the precise function of Abcc6 and to develop experimental therapies.     

MLP (muscle LIM protein) as a stress sensor in the heart

Muscle LIM protein (MLP, also known as cysteine rich protein 3 (CSRP3, CRP3)) is a muscle-specific-expressed LIM-only protein. It consists of 194 amino-acids and has been described initially as a factor involved in myogenesis (Arber et al. Cell 79:221–231, 1994). MLP soon became an important model for experimental cardiology when it was first demonstrated that MLP deficiency leads to myocardial hypertrophy followed by a dilated cardiomyopathy and heart failure phenotype (Arber et al. Cell 88:393–403, 1997). At this time, this was the first genetically altered animal model to develop this devastating disease. Interestingly, MLP was also found to be down-regulated in humans with heart failure (Zolk et al. Circulation 101:2674–2677, 2000) and MLP mutations are able to cause hypertrophic and dilated forms of cardiomyopathy in humans (Bos et al. Mol Genet Metab 88:78–85, 2006; Geier et al. Circulation 107:1390–1395, 2003; Hershberger et al. Clin Transl Sci 1:21–26, 2008; Kn?ll et al. Cell 111:943–955, 2002; Kn?ll et al. Circ Res 106:695–704, 2010; Mohapatra et al. Mol Genet Metab 80:207–215, 2003). Although considerable efforts have been undertaken to unravel the underlying molecular mechanisms—how MLP mutations, either in model organisms or in the human setting cause these diseases are still unclear. In contrast, only precise knowledge of the underlying molecular mechanisms will allow the development of novel and innovative therapeutic strategies to combat this otherwise lethal condition. The focus of this review will be on the function of MLP in cardiac mechanosensation and we shall point to possible future directions in MLP research.     

Endogenous orienting is reduced during the attentional blink

We studied endogenous cuing during the attentional blink in order to examine its resistance to dual task interference. In two experiments, we found a reduced impact of endogenous cuing during the “blink” time of the attentional blink. In a third experiment endogenous cuing was intact when it was not influenced by demands imposed by an earlier target. Contrary to a recent report (Zhang et al. in Exp Brain Res, 185, 287–295, 2008), the results indicate that endogenous orienting guided by semantic cues is susceptible to the attentional blink.