Global motion integration in the postero-medial part of the lateral suprasylvian cortex in the cat

In cats, the postero-medial part of lateral suprasylvian cortex (PMLS) is generally considered a key area for motion processing. While behavioral studies have indeed supported the role of PMLS cortex in higher order motion integration (Cereb Cortex 6:814–822, 1996), there is no evidence that individual PMLS cells can perform such analysis (Vis Neurosci 5:463–468, 1990; J Neurophysiol 63:1529–1543, 1990). Given the fundamental importance of understanding the neural substrate subtending higher order motion processing, we investigated whether PMLS neurons can signal the direction of motion of complex random dot kinematograms (RDKs) wherein comprising elements do not provide any local coherent motion cues. Results indicated that most PMLS cells (82%) can integrate the displacement of individual elements into a global motion percept. Their large receptive fields allowed the integration of motion for elements separated by large spatial intervals (up to 4°). In most cases, the analysis of complex RDK motion necessitated the contribution of the area of the visual field beyond the classical receptive field. None of the complex RDK-sensitive cells were found to be pattern-motion selective when tested with plaid patterns. Our results provide the first evidence that receptive fields of PMLS neurons can perform global motion analysis and support the behavioral evidence that this area is implicated in complex motion processing (Cereb Cortex 6:814–822, 1996). It also further corroborates the findings that PMLS neurons cannot signal the true direction of a plaid pattern (Vis Neurosci 5:463–468, 1990; J Neurophysiol 63:1529–1543, 1990). Providing that these same neurons can signal the direction of complex RDKs, there may be distinct cortical mechanisms for processing different types of complex motion.     

Zebrafish as a new animal model to study lymphangiogenesis

The lymphatic system is essential for fluid homeostasis, fat absorption and immune responses, and also plays key roles under pathological conditions, such as tumor metastasis, lymphoedema and inflammation. The main function of the lymphatic vascular system is to return excess interstitial fluid back to the blood vascular system. Lymph, including fluid, macromolecules, leukocytes and activated antigen-presenting cells, is transported from the blind-ended lymphatic capillaries toward the collecting lymphatic vessels; for there, it is returned to the blood circulation through lymphatico-venous junctions (Alitalo et al. in Nature 438:946–954, 2005). Despite its importance, lymphangiogenesis remains poorly understood. The lack of specific markers has complicated the identification of lymph vessels, and a small animal model that could be genetically manipulated to discover the function of novel lymphangiogenic candidates has only recently become available (Ny et al. in Nat Med 11(9):998–1004, 2005). Since 2004, we have worked to make the zebrafish a new genetic model for unraveling the function of candidate genes involved in lymphangiogenesis. We have demonstrated that zebrafish possess a lymphatic vascular system that shares the morphological, molecular and functional characteristics of the lymphatic vessels found in other vertebrates (Yaniv et al. in Nat Med 12(6):711–716, 2006). In this process, we realized that it was necessary to seek a common definition for the lymph system which would be applicable from fish to man. The aim of this article is to review classical, mainly morphological, studies in order to elucidate the nature of the lymphatic system.     

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.     

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.     

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.     

Neural noise can explain expansive, power-law nonlinearities in neural response functions

Many phenomenological models of the responses of simple cells in primary visual cortex have concluded that a cell's firing rate should be given by its input raised to a power greater than one. This is known as an expansive power-law nonlinearity. However, intracellular recordings have shown that a different nonlinearity, a linear-threshold function, appears to give a good prediction of firing rate from a cell's low-pass-filtered voltage response. Using a model based on a linear-threshold function, Anderson et al. showed that voltage noise was critical to converting voltage responses with contrast-invariant orientation tuning into spiking responses with contrast-invariant tuning. We present two separate results clarifying the connection between noise-smoothed linear-threshold functions and power-law nonlinearities. First, we prove analytically that a power-law nonlinearity is the only input-output function that converts contrast-invariant input tuning into contrast-invariant spike tuning. Second, we examine simulations of a simple model that assumes instantaneous spike rate is given by a linear-threshold function of voltage and voltage responses include significant noise. We show that the resulting average spike rate is well described by an expansive power law of the average voltage (averaged over multiple trials), provided that average voltage remains less than about 1.5 SDs of the noise above threshold. Finally, we use this model to show that the noise levels recorded by Anderson et al. are consistent with the degree to which the orientation tuning of spiking responses is more sharply tuned relative to the orientation tuning of voltage responses. Thus neuronal noise can robustly generate power-law input-output functions of the form frequently postulated for simple cells.     

Effects of visual stimuli on temporal order judgments of unimanual finger stimuli

Successive tactile stimuli, delivered one to each hand, are referred to spatial representation before they are ordered in time (Yamamoto and Kitazawa in Nat Neurosci 4:759–765 2001a). In the present study, we examined if this applies even when they are delivered unilaterally to fingers of a single hand. Tactile stimuli were delivered left-to-rightward relative to the body (2nd–3rd–4th) or in reverse with stimulus onset asynchrony of 100 ms. Simultaneously with the delivery of tactile stimuli, three of nine small squares arranged in a matrix of 3 × 3 were turned on as if they appeared near the tips of the fingers. Although subjects were instructed to ignore the visual stimuli and make a forced choice between the two orders of tactile stimuli, the correct-judgment probability depended on the direction of visual stimuli. It was greater than 95% when the direction of visual stimuli matched that of the tactile stimuli, but less than 50% when they were opposite to each other. When the right hand was rotated counterclockwise on the horizontal plane (90°) so that the fingers were pointing to the left, the preferred direction of visual stimuli that yielded the peak correct judgment was also rotated, although not to the full extent. These results show that subjects cannot be basing their tactile temporal order judgment solely on a somatotopic map, but rather on a spatial map on which both visual and tactile signals converge. An erratum to this article can be found at     

Interhemispheric interaction expands attentional capacity in an auditory selective attention task

Previous work from our laboratory indicates that interhemispheric interaction (IHI) functionally increases the attentional capacity available to support performance on visual tasks (Banich in The asymmetrical brain, pp 261–302, 2003). Because manipulations of both computational complexity and selection demand alter the benefits of IHI to task performance, we argue that IHI may be a general strategy for meeting increases in attentional demand. Other researchers, however, have suggested that the apparent benefits of IHI to attentional capacity are an epiphenomenon of the organization of the visual system (Fecteau and Enns in Neuropsychologia 43:1412–1428, 2005; Marsolek et al. in Neuropsychologia 40:1983–1999, 2002). In the current experiment, we investigate whether IHI increases attentional capacity outside the visual system by manipulating the selection demands of an auditory temporal pattern-matching task. We find that IHI expands attentional capacity in the auditory system. This suggests that the benefits of requiring IHI derive from a functional increase in attentional capacity rather than the organization of a specific sensory modality.     

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.     

Nonmuscle myosin, force maintenance, and the tonic contractile phenotype in smooth muscle

Recent studies have demonstrated that nonmuscle (NM) myosin II forms filaments and can generate and maintain force in smooth muscle tissue [Lofgren et al. (2003) J Gen Physiol 121:301–310; Morano et al. (2000) Nat Cell Biol 2:371–375]. To further investigate the mechanical contribution of NM myosin to force maintenance during smooth muscle contraction, we utilized a selective inhibitor of the NM myosin ATPase, blebbistatin [Straight et al. (2003) Science 299:1743–1747]. Force and myosin light chain (MLC₂₀) phosphorylation were measured during KCl stimulation of small strips of intact mouse bladder and aorta at 22°C. The bladder strips contracted with a typical phasic force response, characterized by a large, rapid, transient increase in force followed by a decline to a lower, steady-state level. The addition of blebbistatin did not alter the peak force, but decreased force maintenance. KCl depolarization of aortic strips resulted in a tonic contraction; force increased to a sustained steady state. Similar to the bladder tissue, blebbistatin substantially decreased the steady-state force in the aorta. Blebbistatin did not influence the MLC₂₀ phosphorylation transient in either tissue type. Additionally, blebbistatin did not change the maximum shortening velocity (V _max) during KCl depolarization of the aorta. Our results also suggest that NMIIA and NMIIB isoforms are differentially expressed. The expression of NMIIA is more prominent in the bladder, while NMIIB expression is predominant in the aorta. These results suggest that NM myosin contributes to the mechanism of force maintenance in smooth muscle, and could suggest that the expression of NMIIB is a factor for determining the tonic contractile phenotype.     

Effects of stimulus spatial frequency,size, and luminance contrast on orientation tuning of neurons in the dorsal lateral geniculate nucleus of cat

It is generally thought that orientation selectivity first appears in the primary visual cortex (V1), whereas neurons in the lateral geniculate nucleus (LGN), an input source for V1, are thought to be insensitive to stimulus orientation. Here we show that increasing both the spatial frequency and size of the grating stimuli beyond their respective optimal values strongly enhance the orientation tuning of LGN neurons. The resulting orientation tuning was clearly contrast-invariant. Furthermore, blocking intrathalamic inhibition by iontophoretically administering γ-aminobutyric acid (GABA)_A receptor antagonists, such as bicuculline and GABAzine, slightly but significantly weakened the contrast invariance. Our results suggest that orientation tuning in the LGN is caused by an elliptical classical receptive field and orientation-tuned surround suppression, and that its contrast invariance is ensured by local GABA_A inhibition. This contrast-invariant orientation tuning in LGN neurons may contribute to the contrast-invariant orientation tuning seen in V1 neurons.     

Characterization of the heartworm <Emphasis Type="Italic">Acanthocheilonema spirocauda</Emphasis> (Leidy, 1858) Anderson, 1992 (Nematoda: Onchocercidae) in Scandinavia

The heartworm Acanthocheilonema spirocauda (Leidy, Proc Acad Nat Sci Philadelphia 10:110–112, 1858) Anderson, 1992 is described from material collected from harbour seals in Scandinavia and compared with types and other specimens described by Anderson (Can J Zool 37:481–493, 1959) from harbour seals in eastern USA. Most morphometric characters of the material from USA fall within the ranges established for the Scandinavian one. Some intraspecific variability in the organisation of papillae on the male tail was detected among the Scandinavian specimens. Differences between the specimens from Scandinavia and Eastern USA are also found in the organisation of papillae on the tail of males and females. An excretory pore was not discernible, but a clearly hemizonid-like structure is described. For the first time, scanning electron micrographs present external morphological structures of the species.     

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.     

Saccadic-like visuomotor adaptation involves little if any perceptual effects

Studies on visuomotor adaptation provide crucial clues on the functional properties of the human motor system. The widely studied saccadic adaptation paradigm is a major example of such a fruitful field of investigation. Magescas and Prablanc (J Cogn Neurosci 18(1):75–83, 2006) proposed a transposition of this protocol to arm pointing behavior, by designing an experiment in which the informational context of the upper limb visuomotor system is comparable to that of the saccadic system. Subjects were given terminal only visual feedback in a hand pointing task, assumed to produce a purely terminal visual error signal. Importantly, this paradigm has been shown to induce no saccadic adaptation. Although the saccadic adaptation paradigm is known to induce a predominantly motor adaptation with minor sensory effects, the lack of sensory changes has not been tested in its transposition to pointing. The present study was a partial replication of Magescas and Prablanc’s (J Cogn Neurosci 18(1):75–83, 2006) study with additional control tests. A first experiment searched for a possible change in the static visual-to-proprioceptive congruency. A second experiment, based on an anti-pointing task, aimed at separating the sensory and motor effects of the adaptation in a dynamic condition. Consistent with most results on saccadic adaptation, we found a predominant adaptation of the motor components, with little if any involvement of the sensory components. Results are interpreted by proposing a causal relationship between the type of error signal and its adaptive effects.     

Visuomotor mental rotation: the reaction time advantage for anti-pointing is not influenced by perceptual experience with the cardinal axes

In the visuomotor mental rotation (VMR) paradigm, participants execute a center-out reaching movement to a location that deviates from a visual cue by a predetermined instruction angle. Previous work has demonstrated a linear increase in reaction time (RT) as a function of the amplitude of the instruction angle (Georgopoulos and Massey in Exp Brain Res 65:361–370, 1987). In contrast, we recently reported a RT advantage for an instruction angle of 180° relative to a 90° angle (Neely and Heath in Neurosci Lett 463:194–198, 2009). It is possible, however, that perceptual expertise with the cardinal axes, which are perceptually familiar reference frames, influenced the results of our previous investigation. To address this issue, we employed a VMR paradigm identical to that of our previous work, with the exception that the stimulus array was shifted 45° from the horizontal and vertical meridians. Our results demonstrated that RTs were fastest and least variable when the instruction angle was 0°, followed by 180°, which in turn, was faster than 90°. Such findings establish that the RT advantage for the 180° instruction angle is not influenced by perceptual expertise with the cardinal axes. Moreover, the present results provide convergent evidence that RT is not determined by the angle of rotation; instead, they indicate that response latencies reflect computational differences in the complexity of response remapping.     

Perturbation of visuospatial attention by high-frequency offline rTMS

The contribution of different cortical regions to visuospatial attention can be probed with the help of perturbation techniques, such as transcranial magnetic stimulation (TMS). Repetitive TMS (rTMS) has also been suggested as a tool for the therapy of brain injuries, by adjusting the neural excitability of injured or intact brain regions. Low- and high-frequency rTMS have been shown to result in subsequent (offline) reductions or increases of local cortical excitability, respectively. Previous studies demonstrated that low-frequency (1 Hz) rTMS of posterior parietal cortex (PPC) produced significantly reduced detection of stimuli in the visual hemifield contralateral to the stimulation site, as well as increased ipsilateral detection. We here explored the functional impact of high-frequency (20 Hz) rTMS with an attention task similar to that of a previous low-frequency study (Hilgetag et al. in Nat Neurosci 4:953–957, 2001). Normal healthy subjects (N = 14) received high-frequency rTMS (20 Hz, 10 min, 50% stimulator output) over right or left PPC (coordinate points P4 or P3). After stimulation of the right PPC, detection of single visual stimuli in the contralateral hemifield was significantly impaired. Generally, rTMS of right and left PPC produced mirror-symmetric trends in reduced contralateral detection. These effects were still present after post-TMS sham stimulation (more than 20 min after the end of active rTMS). The results suggest that attentional function can be perturbed by high-frequency rTMS as well as by low-frequency rTMS, despite potential differences in the underlying neural mechanisms. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

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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Bimanual reaches with symbolic cues exhibit errors in target selection

We examined the movement trajectories of symmetric and asymmetric bimanual reaches to targets specified by direct spatial cues and by indirect symbolic cues. Symbolically cued asymmetric reaches have been shown to exhibit longer reaction times compared with symmetric reaches, whereas no such reaction time cost is observed when targets are spatially cued—a pattern thought to implicate increased demands on response selection (Diedrichsen et al. in Psychol Sci 12(6):493–498, 2001). As symbolically cued reaches impose greater demands on cognitive visuomotor translation than spatially cued reaches (Diedrichsen et al. in Cereb Cortex 16(12):1729–1738, 2006), we asked whether bimanual movements exhibit more spatial coupling with symbolic cues than with spatial cues. Participants made bimanual symmetric and asymmetric reaches to short- and long-distance targets cued either symbolically or spatially. We replicated the reaction time cost for symbolically cued asymmetric movements. A subset of these asymmetric reaches also showed large trajectory modulations. It appeared that this subset had been incorrectly prepared and the movements required of the left and right arms had been switched. No such errors in target selection were observed when targets were spatially cued. In contrast to the reaction time cost and errors in selection for symbolically cued movements, we observed little evidence of increased spatial coupling with symbolic cues when movements were initiated towards the correct targets. We conclude that cognitive visuomotor translation demands during response selection increases bimanual coupling at the level of response selection (reaction time cost, errors in target selection) but not at the level of movement execution (spatial coupling).     

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.     

Comparing several equations that predict peak VO2 using the 20-m multistage-shuttle run-test in 8-10-year-old children

This study compared the validity of reported equations as predictors of peak VO₂ in 8–10-year-old children. Participants (90 boys and girls aged 8–10 years) performed the multistage-shuttle-run-test (MSRT) and peak VO₂ was measured in field using a portable gas analyser. The equations that estimated peak VO₂ from the MSRT performance were chosen according to the age range of this study. As follows, the FITNESSGRAM reports and the equations of Leger et al. (Can J Appl Sport Sci 5: 77–84, 1988), Barnett et al. (Pediatr Exerc Sci 5:42–50, 1993), Matsuzaka et al. (Pediatr Exerc Sci 16:113–125, 2004) and Fernhall et al. (Am J Ment Retard 102:602–612, 1998) were used to estimate the peak VO₂ and compared with the directly measured value. The equation of Leger et al. (Can J Appl Sport Sci 5: 77–84, 1988) provided a mean difference (d) of 4.7 ml kg⁻¹ min⁻¹ and a 1.0 slope. The equation of Matsuzaka et al. (Pediatr Exerc Sci 16:113–125, 2004)(a) using maximal speed (MS) showed a higher d (5.4) than the remaining using total laps d (4.2). The equation of Barnett et al. (Pediatr Exerc Sci 5:42–50, 1993)(a) that includes triceps skinfold and MS showed the highest d (6.1) but the smallest range (24.1) and slope (0.6). Data from the FITNESSGRAM had the smallest d (1.8 ml kg⁻¹ min⁻¹), but also had the highest range between limits of agreement (28.6 ml kg⁻¹ min⁻¹) and a 1.2 slope. The lowest slope (0.4) and range (22.2 ml kg⁻¹ min⁻¹) were observed using the equation of Fernhall et al. (Am J Ment Retard 102:602–612, 1998). Log transformation of the data revealed that the equations of Matsuzaka et al. (Pediatr Exerc Sci 16:113–125, 2004)(a) (1.1*/÷1.25) and Fernhall et al. (Am J Ment Retard 102:602–612, 1998) (1.17*/÷1.25) showed the closest agreement among all, but they still yield unsatisfactory accuracy.