Grasp effects of the Ebbinghaus illusion are ambiguous

The assumption that the Ebbinghaus/Titchener illusion deceives perception but not grasping, which would confirm the two-visual-systems hypothesis (TVSH) as proposed by Milner and Goodale (The visual brain in action, 1995), has recently been challenged. Franz et al. (Exp Brain Res 149:470–477, 2003) found that the illusion affects both perception and grasping, and showed that the effect of the illusion on the peak grip aperture (PGA) cannot be accounted for by different sizes of the gap that separates the central target disk from the surrounding flankers. However, it is not yet clear if the presence of flankers per se influences grasping. We therefore compared kinematic parameters of prehension, using the Ebbinghaus illusion, and a neutral control condition where normal subjects grasped a disk without any flankers. In accordance with the well-known effects of the illusion on perceived size, the PGA was smaller when the target disk was surrounded by large flankers, and larger when it was encircled by small flankers. However, the largest PGA values were reached in the neutral control condition. Hence the presence of flankers leads to a general reduction of the PGA, possibly because the flankers are regarded as obstacles. This ‘reduction effect’ casts doubts on how appropriate it is to directly compare perceptual measures and PGA values when using the Ebbinghaus illusion. Even smaller effects of the illusion on the PGA compared to larger perceptual effects cannot be unequivocally interpreted.     

The influence of display characteristics on active pursuit and passively induced eye movements

Summary A series of experiments has been conducted on human subjects to examine the effect of the movement of small targets located in the peripheral visual field on oculomotor response. Subjects were presented with either a single centrally positioned target or a pair of targets displaced at angles of ±5°, ±10° and ±20° from centre. Target movement was in the horizontal plane, the paired targets always moving in unison. The stimulus waveform consisted of either a sinusoidal or random target motion encompassing a frequency range from 0.1 to 4 Hz with an angular displacement of ±3.5°. Subjects made two types of response. First they were instructed to follow the single target or the centre point of the paired targets. In this active pursuit condition the gain of slow-phase eye velocity progressively decreased as the moving targets were moved from the central position to the most peripheral location (±20°). Secondly, subjects were required passively to ignore the target movement by staring blankly ahead. During this passive response nystagmic eye movements were induced for which the slowphase eye velocity also decreased with increasing target eccentricity, but the gains were always less than those induced during active pursuit. The frequency characteristics of the passive response were very similar to those of the active response, breaking down at frequencies beyond 1 Hz. The ability to suppress the passive response was also investigated by the presentation of a tachistoscopically illuminated earth-fixed target. The response was found to decline as the interval between presentations of the fixation target was decreased from 3000 ms to 100 ms. It is suggested that the passive response originates from a basic velocity drive to the oculomotor system resulting from image movement across the retina. This velocity drive may be cancelled with adequate fixation but must be enhanced to accomplish desired eye velocity during active pursuit.     

Compensation for distal impairments of grasping in adults with hemiparesis

Previous studies have shown that patients with arm and hand paresis following stroke recruit an additional degree of freedom (the trunk) to transport the hand during reaching and use alternative strategies for grasping. The few studies of grasping parameters of the impaired hand have been case studies mainly focusing on describing grasping in the presence of particular impairments such as hemi-neglect or optic ataxia and have not focussed on the role of the trunk in prehension. We hypothesized that the trunk movement not only ensures the transport of the hand to the object, but it also assists in orienting the hand for grasping when distal deficits are present. Nineteen patients with chronic hemiparesis and seven healthy subjects participated in the study. Patients had sustained a stroke of non-traumatic origin 6–82 months previously (31±22 months) and had mild or moderate to severe arm paresis. Using a whole hand grasp, subjects reached and grasped a cylinder (35 mm) that was placed sagittally (T1) or at a 45° angle to the sagittal midline in the ipsilateral workspace (T2), both at about 90% arms length (10 trials per target). Eight infrared emitting diodes were placed on bony landmarks of the hand, arm and trunk and kinematic data were recorded by an optical motion analysis system (Optotrak) for 2–5 s at 120 Hz. Hand position and orientation were recorded by a Fastrack Polhemus system. Our results show that during goal-directed prehension tasks, individuals with hemiparesis oriented the hand more frontally for grasping and used more trunk anterior displacement or rotation to transport the hand to the target compared to healthy subjects. Despite these changes, the major characteristics of reaching and grasping such as grip aperture size, temporal coordination between hand transport and aperture formation and the relative timing of grip aperture were largely preserved. For patients with more severe distal impairments, the amount of trunk displacement was also correlated with a more frontal hand orientation for grasping. Furthermore, in healthy subjects and patients without distal impairments, the trunk movement was mostly related to proximal arm movements while in those with distal impairments, trunk movement was related to both proximal and distal arm movements. Data support the hypothesis that the trunk movement is used to assist both arm transport and hand orientation for grasping when distal deficits are present.     

The effect of central retinal lesions on optokinetic nystagmus in the monkey

Summary In alert monkeys (Macaca mulatta and fascicularis) the effect of central retinal lesions on fast optokinetic responses was investigated during high velocity optokinetic and visual-vestibular conflict stimulation. The fast component of the optokinetic response manifests itself as a rapid rise in the slow-phase eye velocity after light-on, during high velocity optokinetic stimulation; and a sudden drop in eye velocity after light-off. In contrast, the velocity storage component leads only to gradual changes in eye velocity during continuous optokinetic stimulation and after light-off (optokinetic after-nystagmus).Retinal lesions were placed by laser coagulation in and around the fovea. Responses of the normal and lesioned eye were compared. It was found that central lesions up to 12 deg (fovea diameter 6 deg) had only a negligible effect on fast optokinetic responses. With lesions of more than 25–30 deg diameter centered on the fovea definite fast responses could still be obtained, on average reduced to about 50% of the responses of the normal eye. Some monkeys showed initially no fast optokinetic responses and had, therefore, to be excluded from lesion experiments.The results demonstrate that fast optokinetic responses also can be obtained from extrafoveal areas, i.e. areas which are not generally involved in smooth pursuit eye movements. These results are discussed in relation to reports that the smooth pursuit eye movement system is also used to generate fast optokinetic responses.Supported by Swiss National Foundation for Scientific Research 3.343-2.78 and Deutsche Forschungsgemeinschaft, SFB 200 A2These experiments were performed at the Dept. of Neurology, University of Zürich. A preliminary report of this work was presented at the workshop on Physiological and pathological aspects of eye movements in Habay-la-Neuve (Belgium) and at the 8th Extraordinary Meeting of the Barany Society in Basel (Switzerland)     

Cerebellar subjects show impaired coupling of reach and grasp movements

We examined how cerebellar deficits in isolated reaching or grasping movements contribute to abnormalities in a combined reach and grasp movement, and whether people with cerebellar damage show abnormalities in the spatiotemporal relationships of reach and grasp movements. We studied subjects with cerebellar damage and matched controls as they performed a combined reach and grasp, an isolated reach, and an isolated grasp. These movements were performed under slow-accurate and fast speed conditions. Subjects were also tested for their ability to correctly estimate the target size based on visual information. We measured the three-dimensional position of the index finger, thumb and wrist joint during all tasks. Results showed that cerebellar subjects overestimated the target size to a greater extent than did controls. During movement testing, cerebellar subjects were impaired on isolated reach and isolated grasp. However, they did not worsen parameters of reach or grasp movements during the combined reach and grasp. Instead there were distinct deficits in the coupling of the reach and grasp movement. Compared with controls, cerebellar subjects showed abnormalities in the sequence of the reach and grasp movement and highly variable timing of peak grip aperture. In the slow-accurate condition, cerebellar subjects decomposed the reach and grasp movement into separate reach then grasp components, and produced multiple peaks in grip aperture. In the fast condition, cerebellar subjects did not decompose, produced a single peak grip aperture, and dropped the target more often. These results indicate that cerebellar damage can cause a specific breakdown in the coupling of reach and grasp movements. The cerebellum may be involved in combining reach and grasp movements into a single motor program.     

Finger control in the tripod grasp

The present study aimed to determine whether grasping is based on either (1) synchronous finger movements producing stereotyped types of grasp, or (2) independently controlled finger movements producing variable final finger postures. Participants reached for and grasped sphere-shaped objects of three sizes. They were allowed to select three different grasp configurations: a "pinch" grip (thumb and index finger), a "middle" grip (thumb and middle finger) and a "tripod" grip (thumb and index plus middle finger). Object distance from the subject was varied in order to verify whether finger control and final finger postures varied according to the degree of accuracy required by target object distance. All the participants always selected the tripod grip when reaching for the large and medium size objects. The pinch grip was used by half of the participants when reaching for the small object, but only in 17% of the trials. Target object distance did not appear to influence the type of selected grip. The tripod grip was found to consist of two different components: an aperture component (opening and closing the gap between the thumb and opposition finger) and a finger separation component (increasing and decreasing the gap between the index and middle fingers). The timing of the aperture component was the same for the index and middle fingers. In contrast, the timing of the finger separation was weakly coupled with the aperture components. Moreover, the relative spatial position among the three fingers during and at the end of grasp varied according to object size. When grasping the large object, both the index finger and the middle finger were in opposition to the thumb. In contrast, when grasping the small object, the index finger was less in opposition to the thumb with respect to the middle finger. The final spatial position of the thumb relative to the starting position was independent of object size, whereas those of the index and middle fingers varied with object size. The results support the notion that grasp is accomplished by using two virtual fingers formed by the thumb and one or more other fingers that synchronously open and close on the object along the opposition space [Arbib 1990; in: Jeannerod M (ed) Attention and performance XIII: motor representation and control. Lawrence Erlbaum, Hillsdale, pp 111–138]. This suggests a degree of coupling between the control of the virtual fingers. Electronic Publication     

Role of the feedforward command and reafferent information in the coordination of a passing prehension task

The performances of a deafferented patient and five control subjects have been studied during a self-driven passing task in which one hand has to grasp an object transported by the other hand and in a unimanual reach-to-grasp task. The kinematics of the reach and grasp components and the scaling of the grip aperture recorded for the self-driven passing task were very similar in controls and the deafferented subject (GL). In contrast, for the unimanual task when vision was absent, GL’s coordination between reaching and grasping was delayed in space and time compared with the control subjects. In addition, frequent reopening of the grip was observed in GL during the final closure phase of the unimanual prehension task. These results support the notion that afferent proprioceptive information resulting from the reaching movement – which seemed to be used to coordinate reaching and grasping commands in the unimanual task – is no longer necessary in the self-induced passing task. Finally, for the externally driven passing task, when the object was passively transported by the experimenter, the coordination was consistently modified in all subjects; grip aperture onset was delayed, thus asserting a specific contribution of the central command or feedforward mechanisms into the anticipation of the grasp onset observed in the self-driven passing task. The origin and nature of the information necessary for building up the feedforward mechanisms remains to be elucidated. Received: 21 August 1998 / Accepted: 29 January 1999     

TRP channels: a TR(I)P through a world of multifunctional cation channels

The transient receptor potential (TRP) family of ion channels comprises more than 50 cation-permeable channels expressed from yeast to man. On the basis of structural homology, the TRP family can be subdivided in to seven main subfamilies: the TRPC (Canonical) group, the TRPV (Vanilloid) group, the TRPM (Melastatin) group, the TRPP (Polycystin), the TRPML (Mucolipin), the TRPA (Ankyrin) and the TRPN (NOMP) family. The cloning and characterization of members of this cation channel family has exploded during recent years, leading to a plethora of data concerning TRPs in a variety of cell types, tissues and species. This paper briefly reviews the TRP superfamily and the basic properties of its many members as a readers guide in this Special Issue. Hopefully, a better understanding of TRP channel physiology will provide important insight into the relationship between TRP channel dysfunction and human diseases.     

Grasping reveals visual misjudgements of shape

There are many conditions in which the visually perceived shape of an object differs from its true shape. We here show that one can reveal such errors by studying grasping. Nine subjects were asked to grasp and lift elliptical cylinders that were placed vertically at eye height. We varied the cylinder’s aspect ratios, orientations about the vertical axis and distances from the subject. We found that the subjects’ grip orientations deviated systematically from the orientations that would give the mechanically optimal grip. That this is largely due to misjudging the cylinder’s shape (rather than to selecting a comfortable posture) follows from the fact that the grip aperture was initially more strongly correlated with the maximal grip aperture (which is related to the expected contact positions) than with the final grip aperture (which is determined by the real contact positions). The correlation with the maximal grip aperture drops from 0.8 to 0.6 in the last 1% of the traversed distance (11% of movement time), showing that the grip aperture was anticipated incorrectly (it is automatically “corrected” at contact). The grip orientation was already strongly correlated with the grip orientation at the time of maximal grip aperture, half way through the movement (R≥0.7), showing that the suboptimal grip orientations were planned that way. We conclude that subjects plan their grasps using information that is based on the misperceived shape.     

Somatosensory control of precision grip during unpredictable pulling loads

Summary In the previous paper regarding the somatosensory control of the human precision grip, we concluded that the elicited automatic grip force adjustments are graded by the amplitude of the imposed loads when restraining an active object subjected to unpredictable pulling forces (Johansson et al. 1992a). Using the same subjects and apparatus, the present study examines the capacity to respond to imposed load forces applied at various rates. Grip and load forces (forces normal and tangential to the grip surfaces) and the position of the object in the pulling direction (distal) were recorded. Trapezoidal load force profiles with plateau amplitudes of 2 N were delivered at the following rates of loading and unloading in an unpredictable sequence: 2 N/s, 4 N/s or 8 N/s. In addition, trials with higher load rate (32 N/s) at a low amplitude (0.7 N) were intermingled. The latencies between the start of the loading and the onset of the grip force response increased with decreasing load force rate. They were 80±9ms, 108 ±13ms, 138 ± 27 ms and 174 ± 39 ms for the 32, 8, 4 and 2 N/s rates, respectively. These data suggested that the grip response was elicited after a given minimum latency once a load amplitude threshold was exceeded. The amplitude of the initial rapid increase of grip force (i.e., the catch-up response) was scaled by the rate of the load force, whereas its time course was similar for all load rates. This response was thus elicited as a unit, but its amplitude was graded by afferent information about the load rate arising very early during the loading. The scaling of the catch-up response was purposeful since it facilitated a rapid reconciliation of the ratio between the grip and load force to prevent slips. In that sense it apparently also compensated for the varying delays between the loading phase and the resultant grip force responses. However, modification of the catch-up response may occur during its course when the loading rate is altered prior to the grip force response or very early during the catch-up response itself. Hence, afferent information may be utilized continuously in updating the response although its motor expression may be confined to certain time contingencies. Moreover, this updating may take place after an extremely short latency (45–50 ms). Our findings support the idea that the initiation as well as ongoing regulation of the motor responses is dependent on supraspinal control, but afferent signals directly processed through fast segmental networks may also contribute in the regulation. The grip force responses to the unloading phases, they were also graded by the load force rate and the response latencies increased with decreasing load force rate. However, the latencies were longer and more variable, and no catch-up responses were observed. Rather, the grip force decline was programmed for the inter-trial grip force level.     

Nerve growth factor induced changes in the Golgi apparatus of PC-12 rat pheochromocytoma cells as studied by ligand endocytosis, cytochemical and morphometric methods

Summary Cells of the PC-12 rat pheochromocytoma cell line respond to nerve growth factor (NGF) by sprouting neurites and biochemically differentiating into sympathetic ganglion-like cells. NGF-stimulated (differentiated) and unstimulated (undifferentiated) cells were studied by cytochemical techniques for the localization of the enzymes acid phosphatase (ACPase) and thiamine pyrophosphatase (TPPase), and by a morphometric analysis of the distribution of endocytosed wheat-germ agglutinin labelled with horseradish peroxidase (WGA-HRP). Both cytochemical stains showed the enzymes to be distributed in lysosomes and certain cisternae of the Golgi apparatus in both NGF stimulated and unstimulated cells. ACPase was not confined to GERL (Golgi-endoplasmic reticulum-lysosome) as in certain other cells. The morphometric studies demonstrated that the reaction product of the internalized WGA-HRP occupied 4.7% of the cytoplasmic area in unstimulated cells and 4.5% in NGF-stimulated ones. Despite this similarity, the distribution of the WGA-HRP among the studied intracellular compartments in these two cell groups varied. In the NGF-stimulated cells 3.3% of the WGA-HRP reaction product was found in the innermost Golgi cisterna(e) while in unstimulated cells only 0.3% was seen in this compartment. Similarly, 4.3% of the WGA-HRP stain was found in small vesicles at the trans aspect of the Golgi apparatus in stimulated cells, when only 0.3% of the stain occupied this compartment in undifferentiated cells. The morphometric analysis also revealed that when the PC-12 cells were stimulated with NGF, the Golgi apparatus increased in area by approximately 70%. These findings are consistent with the hypothesis that NGF induced differentiation of PC-12 cells is coupled with enhanced endocytosis of WGA and probably of its receptor to the innermost Golgi cisterna(e) and the closely associated vesicles.     

Distorting the visual size of the hand affects hand pre-shaping during grasping

Vision of the body is known to affect somatosensory perception (e.g. proprioception or tactile discrimination). However, it is unknown whether visual information about one’s own body size can influence bodily action. We tested this by measuring the maximum grip aperture (MGA) parameter of grasping while eight subjects viewed a real size, enlarged or shrunken image of their hand reaching to grasp a cylinder. In the enlarged view condition, the MGA decreased relative to real size view, as if the grasping movement was actually executed with a physically larger hand, thus requiring a smaller grip aperture to grasp the cylinder. Interestingly, MGA remained smaller even after visual feedback was removed. In contrast, no effect was found for the reduced view condition. This asymmetry may reflect the fact that enlargement of body parts is experienced more frequently than shrinkage, notably during normal growth. In conclusion, vision of the body can significantly and persistently affect the internal model of the body used for motor programming.     

A new approach for evaluation of the in vitro haemolytic potential of a solution of a new medicine

In the process of developing an intravenously injectable drug, its haemolytic potential must be considered. There are no Regulatory Guidelines for this kind of test. Many authors have set up different models, attempting to obtain early information about the behaviour of test compounds when injected into the bloodstream.In the present work, an in vitro static model is presented, which takes into account the injection rate (R _inj.) of the drug, and the blood flow rate (Q _v) of the vein in which the drug must be injected. From the relationship between these two parameters, the C_max, expressed as mg/ml, can be calculated. This latter parameter allows us to calculate the drug concentration which, at any moment during injection, comes into contact with a known aliquot of new' blood passing through the injection site. Furthermore, a dynamic test has been developed, which simulates an injection into the blood flow using a tubing system and infusion pumps set for the same R _ini. and Q _v values used in static test. Two injectable drugs, Valium® and Lanoxin®, and a commonly used vehicle, propylene glycol, have been tested by both the methods. These compounds have also been tested with another in vitro method (Prieur et al. 1973), in which a volumetric blood-to-test solution ratio of 1:1 is adopted for every drug tested, with neither R _inj. nor Q _v being taken into account. Results of the haemolytic potential obtained with the three tests have been compared.A good correlation has been observed between the static and the dynamic tests, whereas Prieur's model, which uses a drug-to-blood ratio which is far higher than in vivo, has been shown to give false positive results.It is concluded that a test for the evaluation of the haemolytic potential of drugs must take into account the pharmacodynamic characteristics of the formulation intended to be injected, and at least the blood flow rate. The proposed static test has been demonstrated to be an easy and reliable method of obtaining a true picture of the in vivo situation.     

Sensorimotor characteristics of speech motor sequences

Summary The present experiment focused on the characteristics of sequential speech movements. Subjects generated two successive lip and jaw closing movements associated with the two p's in sapapple. By selectively manipulating the lower lip perturbation it was possible to discern the role of somatic sensory interactions with the presumed sequential movement programming. Lower lip perturbation duration was manipulated to yield two different load conditions. In the Load On (LN) condition, the perturbation remained on for both closing movements. In the Load On/Off (LNF) condition, the perturbation was removed at variable times prior to the second closing movement. Analyses focused on comparing the EMG and resulting kinematic changes for the second p closure across the two load conditions relative to the normal control (no load) condition. The second p closure was differentially affected by the load conditions resulting in changes in the upper and lower lip compensations. Upper lip changes reflected consistent load duration differences; however, the magnitude of the lower lip EMG and kinematic adjustments did not mirror those of the upper lip. In contrast to the differential upper lip/ lower lip changes observed for the magnitude adjustments, timing adjustments were similar for both upper lip and lower lip suggesting a separation between the specification of magnitude and timing of speech movements. Differential load effects were also observed for the timing of the second closing movements. For the LN condition, the onset of muscle activity and subsequent movement occurred earlier (re: control); for the LNF condition, load removal delayed the onset of muscle activity and the subsequent movement (re: control). Further, the opening movement preceding the second closing movement was modified for both load conditions suggesting that all movements in the sequence, not just closing movements, can be modified. The present results suggest that the programming of speech movement sequences is a dynamic process involving scaling and timing of motor commands relying on various degrees of sensory interaction. The apparent separation in the magnitude and timing specification of the movement sequences suggests the parallel influences of different neural systems. The consequence of this control scheme is that specification of movement parameters for sequential motor acts is a flexible real-time sensorimotor process interacting with less-flexible well-established central motor relations. Further, motor programs for speech may reflect certain generalized movement actions (e.g., oral opening, oral closing) rather than individual words, syllables, or other linguistic categories programmed on a movement-to-movement basis.     

Viewing-distance invariance of movement detection

Summary Since visual movement information is often presented in electronic displays or films it is amazing that there is a paucity of research on the influence of viewing distance on motion detection in cinematograms. We report a relatively high degree of detection constancy with changing viewing distance for coherent motion in random-pixel cinematograms. A constant performance irrespective of viewing-distance is called distance-invariance and for motion detection it proves to hold reasonably well for a relatively wide range of viewing distances both for foveal and eccentric vision. The limits of this viewing-distance invariance are explored as a function of screen velocity. Detection performance is quantified by a theshold signal-to-noise-ratio (SNR-) value, S, which is determined as a function of velocity for a range of viewing distances from 53 to 13476 mm for foveal vision and from 60 to 1925 mm at 24° eccentricity on the nasal horizontal meridian of the right eye's retina. The data can be explained, at least qualitatively, by a model in which a spatial-resolution stack has a stack of velocity-tuned motion detectors at every resolution layer. Such a stack-of-stacks model is in line with proposals for contrast-detection stack-models, but it suggests that the usual hypothesis that motion perception is based on the activity of two separate systems, the short-range and the long-range system, might be superfluous. This two-systems distinction was largely based on the different performance found for moving random dot patterns and moving form-defined stimuli. A moving random pixel array viewed at very close range (e.g. 6 cm) presents the subject with relatively large almost square blobs, which are less dissimilar from the phi-stimuli used in classic motion perception studies than random dot stimuli at the usual medium to large viewing distances. It leads to maximum displacement threshold (D_m-) values that are not untypical of the long-range system, but by gradually increasing the viewing-distance and thus decreasing the pixel-size a continuous change is found from typical long-range to typical short-range values of D_m. The two-systems distinction for motion detection appears to refer to the stimulus rather than to the visual system: The motion-detection system might be forced into a local or a global mode of operation by the choice of stimulus.     

Predictability influences finger force control when catching a free-falling object

We studied grip force control when catching a free-falling object with the dominant hand. An instrumented object was dropped either from the subjects opposite hand or expectedly from the experimenters hand. Following digit-object contact, triggered responses were observed in the load and grip force profiles. The peak rates of load force increase and the peak load forces produced at the time the catching fingers made contact with the object were of similar magnitude for the experimenter- and self-release conditions. However, the peak rates of grip force development and the peak grip forces were more pronounced when the object was dropped by the experimenter. These findings suggest that the prediction of the load magnitude was less precise when the object was dropped from the experimenters hand. In addition, a correlation analysis between maximum grip and load force rates revealed a less precise coupling between the force rates in the experimenter-release condition. The time lags between maximum force rates and maximum forces were longer for the experimenter-release than for the self-release condition. These observations may indicate a less precise temporal coupling between grip and load force profiles in the experimenter-release condition. As observed during other manipulative tasks, the co-ordination between grip and load forces is a prerequisite to cope with collision forces when catching free-falling objects. Grip force control during catching is both highly automatic and flexible depending on the predictability of the task.     

The effect of illusory size on force production when grasping objects

Milner and Goodale (1995) have proposed that visuomotor and perceptual processes are mediated by discrete visual systems that reflect the functional independence of action and perception. The visuomotor system is proposed to be insensitive to pictorial illusions of object size, whereas the perceptual system is reliably "tricked" by such figures. Brenner and Smeets (1996) and Jackson and Shaw (2000) demonstrated that grasp preshaping, but not grasping force, is immune to the Ponzo visual illusion, suggesting that not all visuomotor processes operate independently of the perceptual system. The present study investigated the effect of illusory object size on prehension kinematics and grasping dynamics (i.e., grip force and load force) as well as perceptual judgements of object size. Unlike previous investigations, object mass was held constant independent of changes in size. The Ponzo figure reliably affected perceptual estimates of object size, but this effect was restricted to one form of the illusion. Some aspects of the prehension movement were sensitive to veridical but not illusory object size (peak grip aperture, peak grip force, peak vertical wrist acceleration), whereas other movement parameters demonstrated illusory size effects (movement time, peak wrist velocity). Still other movement parameters were not sensitive to veridical or illusory object size (peak load force). Together the data suggest that certain prehension components are immune to pictorial illusions of object size, whereas others are not. Complex interactions between the perceptual and visuomotor systems appear to underlie the anticipatory scaling of grasping forces in prehension.     

Interference of grasping observation during prehension, a behavioural study

During the last 10 years a considerable number of neurophysiological and functional imaging studies have provided evidence that observation and execution of movements activate common representations. Furthermore, several behavioural studies suggest that action observation can influence the performance of movements. Recently it was shown that viewing incongruent movements interferes with the execution of non-object oriented sinusoidal arm movements (Kilner et al. in Curr Biol 13:522–525, 2003). In the current study, we investigated whether interference of action observation also occurs during goal-directed prehension movements. Participants were required to grasp cubes of different sizes while simultaneously observing an actor performing grasping or pointing movements. The actors’ movement could be directed at objects that were identical, or different in size to the cube grasped by the participant. The results showed that maximum grip aperture was affected by observation of grasping towards larger objects. No effect of object size was found during observation of pointing movements. These results suggest that observation of grasping movements can interfere with the on-line control of prehension movements and provides further evidence for overlapping networks for grasping observation and execution.     

Unconscious updating of grasp motor program

Grasp modification during prehension movements was studied in response to slight variations of somesthetic information about object size. Three experiments were carried out. In experiment 1 eight subjects were required to reach and grasp an object whose size could either increase or decrease, whereas its visual image remained unmodified. The object size was changed during the experiment with uninformed subjects after a block of trials during which visual and somesthetic information were congruent. At the end of the experiment subjects were required to reproduce the size of the object with their fingers (matching test). Results showed that maximal grip aperture during prehension as well as finger aperture in the matching test were modified according to variation in object size, although no subject realized that the object had changed during the experiment. Grasp time was also altered by object size change. Greater and earlier adaptation in maximal grip aperture, as well as perturbation of grasp time, were observed for decrease than for increase in object size. However, complete compensation was never reached for both parameters. Constant confidence in vision could have prevented both complete compensation and conscious detection of object change. This was investigated in two additional experiments. In experiment 2 visual information was made unreliable by informing subjects about variation in grasped object size. This led to greater and earlier modification in maximal grip aperture than in experiment 1. Grasp time was kept almost constant regardless of size variation. In experiment 3 vision of the stimulus was prevented and no information on change in object size was given to subjects. The results of experiment 3 were similar to those of experiment 1, although modification in maximal grip aperture was larger for increase in object size. Correspondingly, grasp time was more affected by increase than by decrease in object size. The results of the three experiments suggest that kinematic parameters usually considered as dependent on object properties, such as maximal grip aperture, were modified in order to compensate perturbation of temporal parameters. This modification induced a pragmatic knowledge of object size (as showed by the results of the matching test), although awareness was not reached.     

Selection of appropriate parameters, use of a quality control concept, and suitable statistical analyses for clinical pathology examination of animals in toxicity studies: Results of a current survey by the Japanese pharmaceutical manufacturers association

The Clinical Pathology Testing Working group (CPTWG) of the Japanese Pharmaceutical Manufacturers Association (JPMA) reviewed published literature on abnormal values in clinical pathology parameters in repeat-dose toxicity studies, and conducted a survey on the use of a quality control (QC) concept and statistical analysis methods.Among the journals published between 1985 and 1992, ten were selected that listed many clinical pathology values from repeat-dose toxicity studies of pharmaceuticals. The frequency of abnormal values which were statistically significant in clinical pathology examinations was checked. In all 787 papers, with a total of 15 030 sets of data, were examined to identify those abnormal values that were toxicologically meaningful and those that were not. Abnormal values that were toxicologically meaningful represented 30% and those that were not, 70%. The main criteria in judging abnormal values as toxicologically meaningful included, but were not limited to, the following: pharmacological effects, histopathological changes, obvious changes in related pathology parameters, and dose dependency. Parameters with frequent abnormal values were: haemoglobin (Hb); haematocrit (Ht); red blood cell count (RBC); white blood cell count (WBC); reticulocyte count; platelet count, for haematology; cholesterol; protein; alkaline phosphatase (ALP); urea nitrogen; phospholipid; triglyceride; GPT; potassium; GOT; sodium, for blood chemistry; and urine volume; urinary sodium; urinary potassium; specific gravity (sp. gr.), for urinalysis. These parameters, for each clinical pathology area, are regarded as core parameters to be tested in all repeat-dose toxicity studies.CPTWG also reviewed the toxicity studies (total 930) published in the main Japanese journals between 1985 and 1992. The percentage of correlation of changes in clinical pathology and histopathological examinations was 49% for clinical chemistry tests, 45% for haematology, and 33% of urinalysis. In order to increase the correlation of histopathological and clinical chemistry findings, it would be necessary to have high organ, tissue and species specificities.CPTWG surveyed the current maintenance status and quality control (QC) of equipment that is used for clinical pathology measurements. Maintenance of equipment used for haematology, clinical chemistry and urinalysis was provided in all the facilities surveyed. The scheduled maintenance of haematology equipment was provided by the manufacturers, at least twice a year, at most facilities. The scheduled maintenance by the inhouse technologist was conducted monthly to annually in more than half the facilities. A preoperational check was conducted by more than 90% of those facilities. The maintenance frequency of clinical chemistry equipment was similar. Methods of QC included the confirmation and verification of theoretical values to the actual values of control samples using the X-R control plot method (40% of the facilities) or the sample survey method (40% of the facilities). Most facilities used ± (2SD) or within the minimum and the maximum ranges an acceptable criteria.The last survey CPTWG conducted concerned statistical analysis methods used to evaluate clinical pathology values. When the measured clinical pathology parameters were expressed as mean values and variances, Rank Test or Welch Test was most frequently used in the case of unequal variance.