Sensorimotor processing is dependent on observed speed during the observation of hand-hand and hand-object interactions.

Observing a physical interaction between individuals (e.g., observing friends shaking hands) or between an object and an individual (e.g., observing a teammate striking or being struck with a ball) can lead to somatosensory activation in the observer. However, it is not known whether the speed of the observed interaction modulates such somatosensory activation (e.g., observing a teammate being struck with a slow vs. a fast-moving ball). In three experiments, participants observed a hand or object interact with another hand or object, all presented with a slow- or fast-moving effector. To probe sensorimotor processes during observation, participants were asked to react to an auditory beep (i.e., response time [RT] task) at the moment of observed contact. If observed contact led to increased somatosensory activation, RTs would decrease due to statistical and/ or intersensory facilitation. In all three experiments, RTs were lower when observing fast compared to slow motion stimuli, regardless of the moving (i.e., hand or ball) and target stimulus (i.e., hand or leaf). Further, when only an object (i.e., leaf) was the target, RTs did not differ between the moving hand and moving ball condition. In contrast, when an object (i.e., ball) was used as the moving stimulus, the magnitude of the speed effect (i.e., fast - slow RT difference) was significantly larger when the ball contacted a hand as compared to a leaf. Overall, these results provide novel evidence for a relationship between the observed kinematics of an object-human interaction and the sensorimotor processing in the observer.

The initiation of a hand grip is delayed by silently reading an incompatible syllable.

The movements of phonation structures (e.g., tongue) have been shown to facilitate compatible hand movements. For example, reaction time (RT) of precision and power hand grips (made with tips of thumb and finger vs. whole hand) are shortened with the production of syllables that share similar action features (e.g., employing the proximal vs. dorsal portion of the tongue, respectively). This effect is coined the articulation-grip correspondence (AGC) effect. However, it is not known if the AGC effect is due to action facilitation vs. interference, and if such facilitation/ interference is due to covertly or overtly reading the syllable. To answer the associated empirical questions, the present experiment involved participants initiating a precision or power grip without the covert/ overt reading of a syllable, or while covertly or overtly reading the syllable /ti/ or /ka/. In both the covert and overt reading conditions, there were longer RTs for precision grips with the syllable /ka/ than /ti/, and there were longer RTs for power grips with the syllable /ti/. In contrast, the syllable /ti/ or /ka/ did not alter precision or power grip RTs, respectively. These findings support the notion of articulation-grip interference but not facilitation and that such interference can be observed with covert (silent) reading.

Facilitation of tactile processing during action observation of goal-directed reach and grasp movements.

Our perception of sensory events can be altered by action, but less is known about how our perception can be altered by action observation. For example, our ability to detect tactile stimuli is reduced when our limb is moving, and task-relevance and movement speed can alter such tactile detectability. During action observation, however, the relationship between tactile processing and such modulating factors is not known. Thus, the current study sought to explore tactile processing at a task-relevant location during the observation of reaching and grasping movements performed at different speeds. Specifically, participants observed videos of an anonymous model performing movements at a slow [i.e., peak velocity (PV): 155 mm/s], medium (i.e., PV: 547 mm/s), or fast speed (i.e., PV: 955 mm/s). To assess tactile processing, weak electrical stimuli of different amplitudes were presented to participants' right thumbs when the observed model was at their starting position and prior to any movement, or when the observed model's limb reached its PV. When observing slow movements, normalized perceptual thresholds were significantly lower/better than for the premovement stimulation time. These data suggest that the movement speed can modulate tactile processing, even when observing a movement. Furthermore, these findings provide seminal evidence for tactile facilitation at a task-relevant location during the observation of slow reaching and grasping movements (i.e., speeds associated with tactile exploration).NEW & NOTEWORTHY Previous work has highlighted the relationship between touch processing and movement speed during action, but the current study sought to understand this relationship during action observation of reaching and grasping movements. Here, we provide seminal evidence that tactile perceptual thresholds at the thumb are reduced compared with rest when observing the slowest movement speeds. Thus, tactile processing was facilitated at a task-relevant location during the observation of movements with speeds associated with tactile exploration.

Investigating the online control of goal-directed actions to a tactile target on the body.

Movement corrections to somatosensory targets have been found to be shorter in latency and larger in magnitude than corrections to external visual targets. Somatosensory targets (e.g., body positions) can be identified using both tactile (i.e., skin receptors) and proprioceptive information (e.g., the sense of body position derived from sensory organs in the muscles and joints). Here, we investigated whether changes in tactile information alone, without changes in proprioception, can elicit shorter correction latencies and larger correction magnitudes than those to external visual targets. Participants made reaching movements to a myofilament touching the index finger of the non-reaching finger (i.e., a tactile target) and a light-emitting diode (i.e., visual target). In one-third of the trials, target perturbations occurred 100 ms after movement onset, such that the target was displaced 3 cm either away or toward the participant. We found that participants demonstrated larger correction magnitudes to visual than tactile target perturbations. Moreover, we found no differences in correction latency between movements to perturbed tactile and visual targets. Further, we found that while participants detected tactile stimuli earlier than visual stimuli, they took longer to initiate reaching movements to an unperturbed tactile target than an unperturbed visual target. These results provide evidence that additional processes may be required when planning movements to tactile versus visual targets and that corrections to changes in tactile target positions alone may not facilitate the latency and magnitude advantages observed for corrections to somatosensory targets (i.e., proprioceptive-tactile targets).

Contribution of perfusion to the 11 C-acetate signal in brown adipose tissue assessed by DCE-MRI and 68 Ga-DOTA PET in a rat model.

PURPOSE: Determine if dynamic contrast enhanced (DCE) -MRI and/or 68 gallium 1,4,7,10-tetraazacyclododecane N, N', N″, N‴-tretraacetic acid (68 Ga-DOTA) positron emission tomography (PET) can assess perfusion in rat brown adipose tissue (BAT). Evaluate changes in perfusion between cold-stimulated and heat-inhibited BAT. Determine if the 11 C-acetate pharmacokinetic model can be constrained with perfusion information to improve assessment of BAT oxidative metabolism. METHODS: Rats were split into three groups. In group 1 (N = 6), DCE-MRI with gadobutrol was compared directly to 68 Ga-DOTA PET following exposure to 10 °C for 48 h. 11 C-Acetate PET was also performed to assess oxidation. In group 2 (N = 4), only 68 Ga-DOTA PET was acquired following exposure to 10 °C for 48 h. Finally, in group 3 (N = 10), perfusion was assessed with DCE-MRI in rats exposed to 10 °C or 30 °C for 48 h, and oxidation was measured with 11 C-acetate. Perfusion was quantified with a two-compartment pharmacokinetic model, while oxidation was assessed by a four-compartment model. RESULTS: DCE-MRI and 68 Ga-DOTA PET provided similar perfusion measures, but a decrease in the perfusion signal was noted with longer imaging sessions. Exposure to 10 °C or 30 °C did not affect the perfusion measures, but the 11 C-acetate signal increased in BAT at 10 °C. Without prior information about blood volume, the 11 C-acetate compartment model overestimated blood volume and underestimated oxidation in 10 °C BAT. CONCLUSION: Precise assessment of oxidation via 11 C-acetate PET requires prior information about blood volume which can be obtained by DCE-MRI or 68 Ga-DOTA PET. Since perfusion can change rapidly, simultaneous PET-MRI would be preferred.

Visually guided saccades and acoustic distractors: no evidence for the remote distractor effect or global effect.

A remote visual distractor increases saccade reaction time (RT) to a visual target and may reflect the time required to resolve conflict between target- and distractor-related information within a common retinotopic representation in the superior colliculus (SC) (i.e., the remote distractor effect: RDE). Notably, because the SC serves as a sensorimotor interface it is possible that the RDE may be associated with the pairing of an acoustic distractor with a visual target; that is, the conflict related to saccade generation signals may be sensory-independent. To address that issue, we employed a traditional RDE experiment involving a visual target and visual proximal and remote distractors (Experiment 1) and an experiment wherein a visual target was presented with acoustic proximal and remote distractors (Experiment 2). As well, Experiments 1 and 2 employed no-distractor trials. Experiment 1 RTs elicited a reliable RDE, whereas Experiment 2 RTs for proximal and remote distractors were shorter than their no distractor counterparts. Accordingly, findings demonstrate that the RDE is sensory specific and arises from conflicting visual signals within a common retinotopic map. As well, Experiment 2 findings indicate that an acoustic distractor supports an intersensory facilitation that optimizes oculomotor planning.

Comparison between Accelerometer and Gyroscope in Predicting Level-Ground Running Kinematics by Treadmill Running Kinematics Using a Single Wearable Sensor.

Wearable sensors facilitate running kinematics analysis of joint kinematics in real running environments. The use of a few sensors or, ideally, a single inertial measurement unit (IMU) is preferable for accurate gait analysis. This study aimed to use a convolutional neural network (CNN) to predict level-ground running kinematics (measured by four IMUs on the lower extremities) by using treadmill running kinematics training data measured using a single IMU on the anteromedial side of the right tibia and to compare the performance of level-ground running kinematics predictions between raw accelerometer and gyroscope data. The CNN model performed regression for intraparticipant and interparticipant scenarios and predicted running kinematics. Ten recreational runners were recruited. Accelerometer and gyroscope data were collected. Intraparticipant and interparticipant R2 values of actual and predicted running kinematics ranged from 0.85 to 0.96 and from 0.7 to 0.92, respectively. Normalized root mean squared error values of actual and predicted running kinematics ranged from 3.6% to 10.8% and from 7.4% to 10.8% in intraparticipant and interparticipant tests, respectively. Kinematics predictions in the sagittal plane were found to be better for the knee joint than for the hip joint, and predictions using the gyroscope as the regressor were demonstrated to be significantly better than those using the accelerometer as the regressor.

Contributions of exercise-induced fatigue versus intertrial tendon vibration on visual-proprioceptive weighting for goal-directed movement.

It has been argued that exercise-induced muscle fatigue and tendon vibration can alter proprioceptive estimates of limb position. While exercise-induced muscle fatigue may also affect central efferent processes related to limb position sense, tendon vibration specifically targets peripheral afferent signals. It is unclear, however, whether either of these perturbations (i.e., muscle fatigue or tendon vibration) can alter the multisensory weighting processes preceding goal-directed movements. The current study sought to specifically explore visual-proprioceptive weighting before or after eccentric exercise-induced antagonist muscle fatigue (experiment 1) versus with or without intertrial simultaneous agonist-antagonist tendon vibration (experiment 2). To assess sensory weighting, a visual-proprioceptive mismatch between the participant's actual initial starting position and the associated visual cursor position was employed. This method provides an estimate of the participant's reliance on the proprioceptive or visual starting limb position for their aiming movements. Although there was clear evidence of muscle fatigue, there was no systematic alteration of proprioceptive weighting after eccentric exercise and no relationship between sensory weighting and the level of fatigue. On the other hand, participants' reliance on their actual (proprioceptive) limb position was systematically reduced when exposed to agonist-antagonist tendon vibration before each aiming movement. These findings provide seminal evidence that intertrial tendon vibration, but not exercise-induced fatigue, can alter the reliability of proprioceptive estimates and the relative contributions of visual and proprioceptive information for goal-directed movement.NEW & NOTEWORTHY Previous work has used muscle fatigue or tendon vibration to perturb proprioceptive limb position estimates. This study sought to determine whether exercise-induced muscle fatigue versus intertrial tendon vibration can alter multisensory weighting for upper limb-aiming movements. By introducing a discrepancy between participants' actual proprioceptive and visual finger position, this study provides seminal evidence for the reduction of proprioceptive-to-visual weighting using intertrial tendon vibration but no evidence for a systematic reduction following exercise-induced fatigue.

Cerebrovascular inflammation promotes the formation of brain metastases.

Brain metastases are the most prevalent intracranial malignancy. Patient outcome is poor and treatment options are limited. Hence, new avenues must be explored to identify potential therapeutic targets. Inflammation is a known critical component of cancer progression. Intratumoral inflammation drives progression and leads to the release of circulating tumor cells (CTCs). Inflammation at distant sites promotes adhesion of CTCs to the activated endothelium and then initiates the formation of metastases. These interactions mostly involve cell adhesion molecules expressed by activated endothelial cells. For example, the vascular cell adhesion molecule-1 (VCAM-1) is known to promote transendothelial migration of cancer cells in different organs. However, it is unclear whether a similar mechanism occurs within the specialized environment of the brain. Our objective was therefore to use molecular imaging to assess the potential role of VCAM-1 in promoting the entry of CTCs into the brain. First, magnetic resonance imaging (MRI) and histological analyses revealed that cerebrovascular inflammation induced by intracranial injection of lipopolysaccharide significantly increased the expression of VCAM-1 in the Balb/c mouse brain. Next, intracardiac injection of 4T1 mammary carcinoma cancer cells in animals with cerebrovascular inflammation yielded a higher brain metastasis burden than in the control animals. Finally, blocking VCAM-1 prior to 4T1 cells injection prevented this increased metastatic burden. Here, we demonstrated that by contributing to CTCs adhesion to the activated cerebrovascular endothelium, VCAM-1 improves the capacity of CTCs to form metastatic foci in the brain.

Cerebrovascular MRI in the mouse without an exogenous contrast agent.

PURPOSE: To assess the effect of a variety of anesthetic regimes on T2∗ -weighted MRI of the mouse brain and to determine the optimal regimes to perform T2∗ -weighted MRI of the mouse cerebrovasculature without a contrast agent. METHODS: Twenty mice were imaged with a 3D T2∗ -weighted sequence under isoflurane, dexmedetomidine, or ketamine-xylazine anesthesia with a fraction of inspired oxygen varied between 10% and 95% + 5% CO2 . Some mice were also imaged after an injection of an iron oxide contrast agent as a positive control. For every regime, whole brain vessel conspicuity was visually assessed and the apparent vessel density in the cortex was quantified and compared. RESULTS: The commonly used isoflurane anesthetic leads to poor vessel conspicuity for fraction of inspired oxygen higher or equal to 21%. Dexmedetomidine and ketamine-xylazine enable the visualization of a significantly larger portion of the vasculature for the same breathing gas. Under isoflurane anesthesia, the fraction of inspired oxygen must be lowered to between 10% and 14% to obtain similar vessel conspicuity. Initial results on automatic segmentation of veins and arteries using the iron oxide positive control are also reported. CONCLUSION: T2∗ -weighted MRI in combination with an appropriate anesthetic regime can be used to visualize the mouse cerebrovasculature without a contrast agent. The differences observed between regimes are most likely caused by blood-oxygen level dependent effects, highlighting the important impact of the anesthetic regimes on cerebral blood oxygenation of the mouse brain at rest.

Age-related Differences in Sensorimotor Transformations for Visual and/or Somatosensory Targets: Planning or Execution?

Background: Older and younger adults utilize sensory information differently to plan and control their reaching movements to visual targets. In addition, younger adults appear to utilize different sensorimotor transformations when reaching to somatosensory vs. visual targets. Critically, it is not yet known if older adults perform similar sensorimotor transformations when planning and executing movements to targets of varying modalities (i.e., visual, somatosensory or bimodal).Methods: Participants (12 younger adults, mean age: 22; 12 older adults, mean age: 67) performed reaches with their right upper-limb to visual, somatosensory, and bimodal (i.e., visual-somatosensory) targets in a dark room. Data were ultimately analyzed using a 2 Age-Group by 3-Target Modality ANOVA.Results: For both age groups, endpoint precision was best when the visual target was presented (i.e., visual or bimodal). Critically, older adults exhibited longer reaction time (RT) compared to younger adults, especially when initiating reaches to the somatosensory targets (Cohen's d = 0.95). These longer RT's for older adults when aiming to somatosensory targets may indicate that aging leads to deficits in performing the sensorimotor transformations necessary to plan a reaching movement toward somatosensory targets. In contrast, control mechanisms during reaching execution appear to be comparable for both younger and older adults.Conclusions: When performing a voluntary movement to a felt vs. a seen target location, older adults appear to have altered planning mechanisms, compared to younger adults. Specifically, they tend to take more time to complete the necessary sensorimotor transformations to locate a somatosensory target. These findings could be used to guide the design of physical activity and rehabilitation protocols.

Rapid online corrections for upper limb reaches to perturbed somatosensory targets: evidence for non-visual sensorimotor transformation processes.

When performing upper limb reaches, the sensorimotor system can adjust to changes in target location even if the reaching limb is not visible. To accomplish this task, sensory information about the new target location and the current position of the unseen limb are used to program online corrections. Previous researchers have argued that, prior to the initiation of corrections, somatosensory information from the unseen limb must be transformed into a visual reference frame. However, most of these previous studies involved movements to visual targets. The purpose of the present study was to determine if visual sensorimotor transformations are also necessary for the online control of movements to somatosensory targets. Participants performed reaches towards somatosensory and visual targets without vision of their reaching limb. Target positions were either stationary, or perturbed before (~ 450 ms), or after movement onset (~ 100 ms or ~ 200 ms). In response to target perturbations after movement onset, participants exhibited shorter correction latencies, larger correction magnitudes, and smaller movement endpoint errors when they reached to somatosensory targets as compared to visual targets. Because reference frame transformations have been shown to increase both processing time and errors, these results indicate that hand position was not transformed into visual reference frame during online corrections for movements to somatosensory targets. These findings support the idea that different sensorimotor transformations are used for the online control of movements to somatosensory and visual targets.

Diffusion MRI monitoring of specific structures in the irradiated rat brain.

PURPOSE: The analysis of biological and mesoscopic structures properties by diffusion MRI (dMRI) in brain after radiation therapy remains challenging. In our study, we described the consequences associated with an unwanted dose to healthy tissue, assessing radiation-induced brain alterations of living rats with dMRI compared to histopathology and behavioral assays. METHODS: The right primary motor cortex M1 of the rat brain was targeted by stereotactic radiosurgery with a mean radiation dose of 41 Gy. Multidirectional single b-value dMRI data of the whole brain were acquired with a 7T small-animal scanner before irradiation until 110 days post-irradiation. Diffusion tensor imaging metrics, such as fractional anisotropy (FA), mean diffusivity (MD), axial (AD), and radial diffusivity (RD) were compared to brain alterations detected by immunohistochemistry and motor performances measured by a behavioral test. RESULTS: Between days 90 and 110, radiation necrosis was observed into the white matter spreading into M1 . Results showed a reduction of FA in the corpus callosum and in the striatum, which was driven by an increase in RD from 90 to 110 days post-irradiation, whereas only RD increased in M1 . Values of RD and AD increased in the irradiated hippocampus, while FA remained constant. Moreover, an increased MD, AD and RD was observed in the hippocampus that was probably related to inflammation as well as reactive astrogliosis after 110 days post-irradiation. Finally, rats did not exhibit locomotor deficits. CONCLUSIONS: dMRI metrics can assess brain damage; the sensitivity of dMRI metrics depends on the brain region.

Using proprioception to control ongoing actions: dominance of vision or altered proprioceptive weighing?

Visual feedback is crucial for movement accuracy (e.g., Keele and Posner, J Exp Psychol 77:155-158, 1968). As well, proprioception has been argued to be important for the control of voluntary movements (e.g., Bagesteiro et al., Exp Brain Res 171:358-370, 2006; Rossetti et al., J Neurophysiol 74:457-463, 1995). While tendon vibration (TVib) has been used to perturb proprioceptive information during limb matching tasks (Goodwin et al., Science 175:1382-1384, 1972), the current study employed between-trial dual-muscle TVib, coupled with vision occlusion, to assess the use of vision and proprioception for the online control of voluntary movements. Participants (n = 17) performed an upper-limb reaching task (30 cm). TVib influenced both accuracy and precision of movement endpoint. Critically, variability analyses showed that participant's performance was most affected by TVib at 75% of the movement duration, even in the presence of vision. These findings demonstrate that between-trial dual-muscle tendon vibration can perturb proprioceptive feedback, and further, suggest that proprioception can be important for the online control of reaches, even when vision is available.

Distinct and flexible rates of online control.

Elliott et al. (Hum Mov Sci 10:393-418, 1991) proposed a pseudocontinuous model of online control whereby overlapping corrections lead to the appearance of smooth kinematic profiles in the presence of online feedback. More recently, it was also proposed that online control is not a singular process [see Elliott et al. (Psychol Bull 136(6):1023-1044, 2010)]. However, support for contemporary models of online control were based on methodologies that were not designed to be sensitive to different online control sub-processes. The current study sought to evaluate the possibility of multiple distinct (i.e., visual and non-visual) mechanisms contributing to the control of reaching movements completed in either a full-vision, a no-vision, or a no-vision memory-guided condition. Frequency domain analysis was applied to the acceleration traces of reaching movements. In an attempt to elicit a modulation in the online control mechanisms, these movements were completed at two levels of spatio-temporal constraint, namely with 10 and 30 cm target distances. One finding was that performance in the full-vision relative to both no-vision conditions could be distinguished via two distinct frequency peaks. Increases in the peak magnitude at the lower frequencies were associated with visuomotor mechanisms and increases in the peak magnitude at the higher frequencies were associated with non-visual mechanisms. In addition, performance to the 30-cm target led to a lower peak at a lower frequency relative to the 10 cm target, indicating that the iterative rates of visuomotor control mechanisms are flexible and sensitive to the spatio-temporal constraints of the associated movement.

Understanding the continuum of radionecrosis and vascular disorders in the brain following gamma knife irradiation: An MRI study.

PURPOSE: The radiation dose delivered to brain tumors is limited by the possibility to induce vascular damage and necrosis in surrounding healthy tissue. In the present study, we assessed the ability of MRI to monitor the cascade of events occurring in the healthy rat brain after stereotactic radiosurgery, which could be used to optimize the radiation treatment planning. METHODS: The primary somatosensory forelimb area (S1FL) and the primary motor cortex in the right hemisphere of Fischer rats (n = 6) were irradiated with a single dose of Gamma Knife radiation (Leksell Perfexion, Elekta AG, Stockholm, Sweden). Rats were scanned with a small-animal 7 Tesla MRI scanner before treatment and 16, 21, 54, 82, and 110 days following irradiation. At every imaging session, T2 -weighted (T2 w), Gd-DTPA dynamic contrast-enhanced MRI (DCE-MRI), and T2*-weighted ( T2* w) images were acquired to measure changes in fluid content, blood vessel permeability, and structure, respectively. At days 10, 110, and 140, histopathology was performed on brain sections. Locomotion and spatial memory ability were assessed longitudinally by behavioral tests. RESULTS: No vascular changes were initially observed. After 54 days, a small necrotic volume in the white matter below the S1FL, surrounded by an area presenting significant vascular permeability, was revealed. Between 54 and 110 days, the necrotic volume increased and was accompanied by the formation of a ring-like region, where a mixture of necrosis and permeable blood vessels were observed, as confirmed by histology. Behavioral changes were only observed after day 82. CONCLUSION: Together, DCE-MRI and T2* w images supported by histology provided a coherent picture of the phenomena involved in the formation of new, leaky blood vessels, which was followed by the detection of radionecrosis in a preclinical model of brain irradiation. Magn Reson Med 78:1420-1431, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

An optimal velocity for online limb-target regulation processes?

The utilization of visual information for the control of ongoing voluntary limb movements has been investigated for more than a century. Recently, online sensorimotor processes for the control of upper-limb reaches were hypothesized to include a distinct process related to the comparison of limb and target positions (i.e., limb-target regulation processes: Elliott et al. in Psychol Bull 136:1023-1044. doi: 10.1037/a0020958 , 2010). In the current study, this hypothesis was tested by presenting participants with brief windows of vision (20 ms) when the real-time velocity of the reaching limb rose above selected velocity criteria. One experiment tested the perceptual judgments of endpoint bias (i.e., under- vs. over-shoot), and another experiment tested the shifts in endpoint distributions following an imperceptible target jump. Both experiments revealed that limb-target regulation processes take place at an optimal velocity or "sweet spot" between movement onset and peak limb velocity (i.e., 1.0 m/s with the employed movement amplitude and duration). In contrast with pseudo-continuous models of online control (e.g., Elliott et al. in Hum Mov Sci 10:393-418. doi: 10.1016/0167-9457(91)90013-N , 1991), humans likely optimize online limb-target regulation processes by gathering visual information at a rather limited period of time, well in advance of peak limb velocity.

Improving the evaluation of cardiac function in rats at 7T with denoising filters: a comparison study.

BACKGROUND: We investigate the use of different denoising filters on low signal-to-noise ratio cardiac images of the rat heart acquired with a birdcage volume coil at 7T. Accuracy and variability of cardiac function parameters were measured from manual segmentation of rat heart images with and without filtering. METHODS: Ten rats were studied using a 7T Varian system. End-diastolic and end-systolic volumes, ejection fraction and left ventricle mass (LVM) were calculated from manual segmentation by two experts on cine-FLASH short-axis slices covering the left ventricle. Series were denoised with an anisotropic diffusion filter, a whole variation regularization or an optimized Rician non-local means (ORNLM) filtering technique. The effect of the different filters was evaluated by the calculation of signal-to-noise (SNR) and contrast-to-noise (CNR) ratios, followed by a study of intra- and inter-expert variability of the measurement of physiological parameters. The calculated LVM was compared to the LVM obtained by weighing the heart ex vivo. RESULTS: The SNR and the CNR increased after application of the different filters. The performance of the ORNLM filter was superior for all the parameters of the cardiac function, as judged from the inter- and intra-observer variabilities. Moreover, this filtering technique resulted in the lowest variability in the LVM evaluation. CONCLUSIONS: In cardiac MRI of rats, filtering is an interesting alternative that yields better contrast between myocardium and surrounding tissues and the ORNLM filter provided the largest improvements.

Safety and pharmacokinetics of a kinin B1 receptor peptide agonist produced with different counter-ions.

Several studies have shown the potential therapeutic utility of kinin B1 receptor (B1R) peptide agonists in neurological and ischemic cardiovascular diseases and brain cancer. Preclinical safety studies are a prerequisite for further drug development. The objectives of this study were to determine the acute toxicity and pharmacokinetics of the peptide B1R agonist, SarLys[dPhe8]desArg9-bradykinin (NG29), as trifluoroacetate (TFacetate) or acetate salt form, following intravenous injection in rats. A maximum tolerated dose (MTD) of NG29-TFacetate was established at 75 mg/kg from the results of a dose range-finding study (up to 200 mg/kg). The short-term (4-day) repeat-dose toxicity study of NG29, using its MTD value, showed that NG29-acetate exhibited minimal non-adverse clinical pathology changes in hematology, coagulation, clinical chemistry and urine parameters and severe kidney histopathological changes characterized by renal tubular degeneration. No such effects were observed with NG29-TFacetate. At the injection site, NG29-TFacetate was considered to be more locally irritating when compared to the acetate form. The extent of exposure and half-life values of NG29-TFacetate were comparable to the acetate form (AUC0-α of 10.2 mg/l*h vs. 9.9 mg/l*h; T1/2 of 2.3 h vs. 2.4 h). This study shows that in rats NG29-TFacetate exhibits a superior tolerability profile compared with the peptide acetate form.

The processing of visual and auditory information for reaching movements.

Presenting target and non-target information in different modalities influences target localization if the non-target is within the spatiotemporal limits of perceptual integration. When using auditory and visual stimuli, the influence of a visual non-target on auditory target localization is greater than the reverse. It is not known, however, whether or how such perceptual effects extend to goal-directed behaviours. To gain insight into how audio-visual stimuli are integrated for motor tasks, the kinematics of reaching movements towards visual or auditory targets with or without a non-target in the other modality were examined. When present, the simultaneously presented non-target could be spatially coincident, to the left, or to the right of the target. Results revealed that auditory non-targets did not influence reaching trajectories towards a visual target, whereas visual non-targets influenced trajectories towards an auditory target. Interestingly, the biases induced by visual non-targets were present early in the trajectory and persisted until movement end. Subsequent experimentation indicated that the magnitude of the biases was equivalent whether participants performed a perceptual or motor task, whereas variability was greater for the motor versus the perceptual tasks. We propose that visually induced trajectory biases were driven by the perceived mislocation of the auditory target, which in turn affected both the movement plan and subsequent control of the movement. Such findings provide further evidence of the dominant role visual information processing plays in encoding spatial locations as well as planning and executing reaching action, even when reaching towards auditory targets.