Kinematic Analysis of the Cat Shoulder Girdle during Treadmill Locomotion: an X-ray Study

A quantitative kinematic analysis of the movements of the shoulder girdle in the three dimensions of space during treadmill locomotion (velocity range 0.33–1.2 m/s) was performed in two cats. Since the movement patterns of the scapula and the humeroscapular joint can only vaguely be estimated through the overlying skin we used implanted metal spheres placed on the scapula in combination with three-dimensional pulsed X-ray cinematography (time resolution 20 ms) to reconstruct the excursions of the scapula, the humerus and the elbow and to calculate the respective angular amplitudes and velocities. The movements of the scapula relative to the Th4 spinous process consist of four major components: (i) a monophasic flexion (caudocranial movement of the glenoid fossa during swing)/extension (craniocaudal movement of the glenoid fossa during stance) sequence, the fulcrum for which sequence is situated near the vertebral border of the scapula at the medial elongation of the scapular spine; (ii) a vertical monophasic up/down sequence of the fulcrum relative to the trunk, the highest vertical position being reached during mid-stance and the lowest vertical position during mid-swing; (iii) a biphasic abduction/adduction sequence during swing and during stance respectively; and (iv) small rotations along the scapular spine. The trajectory recordings of the scapula indicate that the scapula yields relative to the trunk under the body weight after ground contact. The angular excursions of the humeroscapular joint consist of: (i) a flexion/extension sequence during swing, a yield after ground contact and a final extension at the end of stance; (ii) an adduction and outward rotation during the early swing phase flexion; (iii) an abduction and inward rotation during the late swing phase extension; and (iv) an adduction during the yield with only minor rotations during the whole stance phase. The movement patterns are discussed in view of the muscular synergies necessary to guide the scapula and the humerus during stance and swing, and in relation to the implications for the organization of these patterns in spinal neuronal systems.     

Recovery of Locomotion after Spinal Cord Hemisection: An X-Ray Study of the Cat Hindlimb

Hemisection of the spinal cord in adult cats is a suitable model to study the mechanisms underlying recovery of motor functions. The initial paresis of the hindlimb is followed by a considerable improvement of locomotor functions of the affected hindlimb. Kinematic analyses of treadmill locomotion were performed from 10 days to 8 months after complete hemisections (right side) of the spinal cord at the thoracolumbar level, using X-ray cinematography for precise measurements of the hindlimb joint angles. The footfall pattern and the electromyogram were recorded. Motor control of both proximal and distal hindlimb joints improved substantially during the 1st postoperative month. However, persistent locomotor deficits were still present several months after hemisection. They could be divided into three groups of symptoms: (1) The gait pattern was disturbed with regard to interlimb coordination. The stance-phase duration of the right hindlimb was shortened. (2) The flexor capacity of the affected hindlimb was reduced, resulting in a slow insufficient flexion of the hip, knee, and ankle during the swing phase. (3) The timing of the flexion–extension events was impaired. The onset of the E1-extension was delayed and the amplitude was reduced. Electromyographic patterns of muscle activity during locomotion of the lesioned side hindlimb differed from the contralateral hindlimb, which served as a control. The results indicate that in spite of a good short-term functional improvement there are long-term locomotor deficits present after spinal cord hemisection.     

Cat Distal Forelimb Joints and Locomotion: An X-ray Study

The complex construction of the joint apparatus of the cat distal forelimb, which allows the paw three degrees of freedom, poses special requirements on the neural signals controlling the paw position. To understand the electromyography (emg) signals of the distal forelimb muscles during locomotion, it is necessary to know the kinematics of the forelimb joints in detail. As no such information is available, we used the pulsed X-ray technique in trained cats during treadmill locomotion to analyse the angular excursions of the wrist, the metacarpophalangeal (MCP) and the proximal interphalangeal (PIP) joints. X-ray illuminations were done in either the parasagittal or the frontal plane. At the beginning of the stance phase the wrist (WR) and the MCP joints extended slowly, and the PIP joints flexed. Whereas the WR and the PIP joints maintained a constant angular position of approximately 200 degrees and 60 degrees, respectively, throughout the stance phase, extension continued in the MCP joints from 240 degrees at touch-down to 300 degrees at the end of the stance phase. Slightly before lift-off (100 ms) the WR and the MCP joints flexed rapidly. This flexion changed approximately 150 ms after lift-off into a slow extension. The PIP joints extended rapidly at the beginning and at the end of the swing phase, during the interposed period of the swing phase they displayed a slow flexion. Rotatory movements of the forelimb in the radioulnar joints were present during the swing and stance phases. During the swing phase the limb first supinated (starting 100 ms after lift-off); pronation occurred immediately before ground contact. During the stance phase the supination angle was kept constant until 100 ms before lift-off, when a short pronation was found. The paw was kept in an ulnar deviated position throughout the complete step cycle. Ulnar deviation decreased at the end of the swing and stance phases. The results of this study increase our understanding of how the body weight is transmitted on to the ground. They suggest four main functions for the skeletomotor apparatus and the underlying neural commands to secure the forward movement of the animal during the stance phase: (i) preparation and stabilization of a force-transmitting platform; (ii) stabilization of the wrist and the carpal/metacarpal joints; (iii) stabilization of the supination angle; (iv) antigravity control of the extension in the MCP.     

An Electromyographic Study of the Hindlimb Locomotor Movements in the Acute Thalamic Rat

In this paper we have analysed the patterns of muscular activities that underlie hindlimb locomotor movements in the acute thalamic rat. Electromyographic activities of muscles representative of the functional muscle groups of the hindlimbs were recorded bipolarly during locomotion in acute thalamic rats. Locomotor movements occurred spontaneously, but could also be induced by electrical stimulation (0. 1 ms pulses; 30–70 Hz; 75–300 μA) of the lateral hypothalamic area. The two hindlimbs displayed a wide variety of coordination patterns during both types of locomotion. However, alternated coordination of the hindlimbs occurred more frequently during induced than during spontaneous locomotion. Correspondingly, the duration of the spontaneous step cycles had a tendency to be shorter than that of the evoked step cycles, although they had a quite similar range. The patterns of muscular activities within one hindlimb were similar during spontaneous and induced locomotion. During each step cycle, (i) the hip and ankle flexors usually displayed a single burst in alternation with that displayed by the hip, knee and ankle extensors, (ii) a double bursting pattern was sometimes observed in flexors during fast locomotor movements, (iii) within flexors and extensors, muscles were recruited sequentially, and (iv) the activation of other muscles (semitendinosus, rectus femoris, extensor and flexor digitorum longus) consisted of single or double bursting patterns.     

X-ray kinematic analysis of forelimb movements during target reaching and food taking in the cat

We have used a three-dimensional X-ray cinematographic approach to investigate the kinematics of the forelimb during target reaching and food taking in five cats. Measurements of the trajectory of the limb during the reaching movement showed that the movement paths of the metacarpophalangeal joint (MCP) and the wrist were sigmoidal with a long nearly linear segment. The elbow followed a bent movement path with maximal inflection in the middle. The path of the humerus had an ascending parabola-like characteristic. The velocity profiles of the MCP and wrist were nearly bell-shaped and skewed to the left, whereas the profiles of the elbow joint were more or less double peaked with the second peak occurring 60-40 ms before object contact. Several different velocity peaks reflecting specific aspects of the task existed when the bell-shaped velocity profiles were divided in their vectorial components. Angular motion of the elbow consisted of a flexion-extension sequence during the reach and a flexion during the subsequent retraction. After an initial flexion during lift-off the wrist was extended. It kept this extended position during orienting towards the food container. During the retraction phase it was further extended. The angle between the wrist axis and the parasagittal plane changed during the movement. It first increased, then decreased during the last 100 ms before the object was reached. During the retraction it increased again to support the object weight against gravity. The position of the wrist was established by radio-ulnar supination and movements of the whole arm around the shoulder joint. We hypothesize that the position of the wrist axis is the controlled variable during protraction and retraction, regardless of whether it is achieved by radio-ulnar supination or by movements around the shoulder.     

Discharge characteristics of the elbow joint nerve of the cat

Direct recordings were made from intact elbow joint nerves (EJN) in decerebrate cats. These multiunit recordings indicate that the EJN is a relatively pure articular nerve and does not contain significant numbers of muscle afferent fibres. In every cat the EJN exhibited a tonic discharge throughout a full range of elbow joint positions. The discharge was most intense when the elbow was extended to 165° and least intense when the joint was held in midrange positions between 90° and 120°. There was a modest increase in discharge as the elbow was held in more flexed positions and activity at 30° was about half of that at 165°. Alterations in the tone of muscles around the joint did not affect the adapted EJN discharge at anyangle.     

Contrasting neuronal activity in the ipsilateral and contralateral supplementary motor areas in relation to a movement of monkey's distal hindlimb

Recordings were made from the supplementary motor areas in both cortical hemispheres of a monkey trained to press a foot pedal. As a result of appropriate limb fixation, the movement was performed with activity predominantly in distal muscles of the right hindlimb. Forty-three percent of contralateral neurons showed movement-related activity. In contrast, only 9% of ipsilateral neurons were active and magnitudes of their activity were smaller.     

Efferent Pattern of Fictive Locomotion in the Cat Forelimb: with Special Reference to Radial Motor Nuclei

In immobilized decerebrate cats fictive locomotion was evoked by midbrain stimulation to analyse the efferent pattern to elbow and to distal forelimb muscles innervated by the deep radial nerve. The locomotor activity was assessed by recording nerve discharges and motoneuronal membrane potential changes. The elbow flexor and extensor motoneurons showed a reciprocal activity; the membranes were correspondingly depolarized and hyperpolarized. In the motor nuclei to the wrist and digit extensors the active phases changed systematically according to the radio-ulnar order of the muscles: the extensor carpi radialis (ECR) was flexor-coupled, the ulnaris (ECU) extensor-coupled, the digitorum communis (EDC), the lateralis (EDL) and the indicis proprius (EIP) displayed intermediate patterns. Intracellular recordings from these motoneurons revealed in all motor nuclei, except ECR, a double depolarization. The first occurred early and the second later in the flexor phase; a hyperpolarization was interposed. The second depolarization mainly determined the active phase. According to the radio-ulnar order of the muscles the onset and termination of the second depolarization were delayed. This was presumably due to the interposed hyperpolarization, which progressively increased in amplitude. The ECR exhibited a single depolarization, into which the double depolarization apparently merged. The other radial motor nuclei, supinator (Sup) and Abductor pollicis longus (APL) displayed complex patterns. Sup showed tonic discharges, flexor-type discharges or discharges extending both into the flexor and extensor phase, APL showed discharges similar to either EIP or Sup. Membrane potential changes were small in APL and Sup. Thus, the central locomotor network generates differentiated efferent activities in the distal forelimb muscles, the radio-ulnar order of the muscles being important for the generated pattern.     

正常下尺桡关节三维有限元模型的建立及验证

背景：国内外学者已应用有限元分析在前臂的桡骨骨折及其固定、尺骨骨折及其固定等方面进行了生物力学评价,但还未见应用该方法对下尺桡关节进行生物力学评价相关的文献报道。 目的：建立并验证下尺桡关节三维有限元模型,用于临床的生物力学研究。 方法：将1名健康男性志愿者右肱骨远端到腕关节中段的CT和MRI图像,导入Mimics10.01和ANSYS10.0中,建立下尺桡关节三维有限元模型,模拟体外生物力学试验,在横向拉伸、轴向压缩、旋前和旋后扭转4种工况下观测下尺桡关节各结构的应力分布,所得结果与文献报道的生物力学实测数据比较验证。 结果与结论：所构建的下尺桡关节有限元模型共有333 805个单元,508 384个节点,客观反映下尺桡关节真实解剖形态。所建模型在横向拉伸、轴向压缩、旋前和旋后扭转4种工况下,理论分析结果与生物力学实测数据一致。证实所建的下尺桡关节有限元模型真实性较高,可用于生物力学分析实验。     

X-ray kinematic analysis of shoulder movements during target reaching and food taking in the cat

Co-ordinate movements around the shoulder are essential during reaching movements. We performed a quantitative kinematic analysis of movements of the shoulder girdle: three-dimensional X-ray frames (time resolution 20 ms) were recorded during the target-reaching and food-taking paradigm in five cats either sitting (n = 4) or standing (n = 1) in front of a food well. Movements of the scapula consisted of a flexion of the scapula (anteversion of the glenoid) followed by flexion of the gleno-humeral joint (decrease in the angle between the scapular spine and humerus). In the sitting animals, the gleno-humeral flexion reversed to extension some 120 ms before object contact, while in the standing animal flexion continued during the ongoing scapular flexion. In both cases, the scapula was nearly horizontal at the end of target reaching. The fulcrum for scapular movements was located near the vertebral border of the scapula at the medial elongation of the scapular spine. No major translational components of the fulcrum with respect to the trunk were found during reaching. Together with full flexion of the scapula, this reduces the number of degrees of freedom considerably and thereby probably simplifying the specification of the end-point of the limb chain. End-point specification is further supported by rotational movements of the scapula. In the sitting animal, the amplitude of inward rotation along the long axis of the scapula was around 20 degrees, while it was much more variable in the standing animal, reflecting more variable starting positions. We hypothesize that the glenoid is used to 'foveate' the target object.     

Shaping of the cat paw for food taking and object manipulation: an X-ray analysis

The kinematics of the cat distal forelimb during food-taking were analysed to obtain information on the movement processes within the paw before and during object taking in a species without monosynaptic cortico-motoneuronal projections. The behaviour was investigated with two tests: either the table test (TT, food offered on a table located at ground level in a reaching distance of 22 and 28 cm) or the horizontal test (HT, food offered in a small container located at shoulder level, height 18–25 cm, reaching distance 6–12 cm). In five animals, the changes in configuration and the conjoint actions of the wrist, the metacarpophalangeal (MCP) and proximal interphalangeal (PIP) joints were assessed with three-dimensional X-ray cinematography (time resolution 20 ms, spatial resolution 1 mm) and video analysis. While approaching the target, the digits were first extended and subsequently abducted. This ‘preshaping’ consisted of combined angular changes in the MCP and PIP joints, thereby attaining an adequate grip aperture. Each cat used a stable strategy, but different cats used different strategies. In the TT, preshaping involved an MCP extension and a PIP flexion. In the HT, predominant extension of the MCP, predominant extension of the PIP, or a combination of both were used, followed by MCP flexion and PIP flexion. The grip aperture started to decrease before object contact, earlier in the TT, later in the HT. Grasping was achieved by flexion of first the PIP and later the MCP. The X-ray analysis gave evidence for individuated digit movements. Correlation analysis of the angular position of the joints between the different phalanges showed that digits 3 and 4 acted in concert, as did digits 2 and 5, but with clear independence between the different pairs. Furthermore, the different phalanges served different purposes during the grasp. Digits 3, 4 established object contact, digits 2, 5 were mainly used to stabilize the paw onto the surface. The cat distal forelimb displays a refined movement repertoire during the preshaping and grasping phase of food-taking. During the preshaping phase, the kinematics resembled in some aspects the situation in humans. The results demonstrate the ability of the polysynaptic projections from the cortico-motoneuronal system to organize differentiated distal limb movements, including individuated movements of the digits.     

Distinct Temporal Patterns of Expression of Sodium Channel-like Immunoreactivity During the Prenatal Development of the Monkey and Cat Retina

Polyclonal and monoclonal antibodies prepared against the α-subunit of the voltage-gated sodium channel (αNaCh) were used to examine the distribution of sodium channel-like immunoreactivity during the prenatal development of the cat and rhesus monkey ( Macaca mulatta ) retina. At all prenatal ages studied, beginning on embryonic day 29 (E29) in the cat and E52 in the monkey, both antibodies labelled optic axons. With the polyclonal antibodies, the appearance of positive cells largely mirrored the onset of their morphological maturation. Immunoreactivity appeared first in the somata of ganglion cells, and subsequently the inner plexiform layer could be distinguished by its intense immunolabelling. A few weeks later horizontal cells displayed immunolabelling that extended to their dendrites in the developing outer plexiform layer. This was followed by immunoreactive cones, with bipolar cells labelled only postnatally. By contrast, with the monoclonal antibody some cells were found to be immunoreactive while their somata were still in the ventricular layer (E33 in cat and E52 in monkey). Many of these cells appeared to migrate to the outer portion of the prospective inner nuclear layer, where they gradually acquired the morphological appearance of bipolar cells. Transient expression of immunolabelling with monoclonal sodium channel antibody was found in the cones of the cat and cones and rods of the monkey. These results indicate that different types of αNaCh-like proteins are expressed in the mammalian retina at distinct developmental periods. Their presence at very early stages during development suggests that these proteins could play a specific role in the commitment and/or differentiation of specific retinal cell types.     

A Metabolic Mapping Study of Orientation Discrimination and Detection Tasks in the Cat

Increasing evidence suggests that a large number of distinct cortical areas and associated subcortical structures participate in the processing of visual information and that different aspects of visual scenes are evaluated in different areas. This necessitates identification of cortical and subcortical regions cooperating in particular visual tasks. Using the 2-deoxyglucose technique, we monitored the differential activation of areas in the cat visual cortex participating in an orientation discrimination and a detection task. Concordant with previous lesion studies, we found increased activity levels in area 17 in the discrimination condition relative to the detection condition. In addition, the 2-deoxyglucose technique revealed discrimination-related increased activations in the claustrum, the putamen and in parts of the anteromedial, anterolateral and posterolateral lateral suprasylvian visual areas. Regions activated differentially with the detection task comprised subdivisions of areas 17, 18, 19 and 21, posterior area 7 (7p), several areas of the posterior part of the middle and posterior suprasylvian sulcus, the pulvinar complex and the superior colliculus. These results show that the 2-deoxyglucose technique is useful to investigate cognitive brain functions, and that different sets of cortical and subcortical regions are activated during two visual tasks with similar visual stimulation.     

寰枢关节脱位病因及其相关作用机制研究

寰枢关节位置特殊,具有承重、运动等重要功能,是延髓和脊髓等重要神经中枢,其内走行颈动静脉、枕大神经等重要结构,寰枢关节脱位病因及其作用机制研究具有重大意义。本文拟从寰枢关节及其周围结构解剖学、生物力学和组织学特点三方面对寰枢关节脱位病因及其相关作用机制进行阐述。     

Effect of Hyperthermia on a Thalamocortical System in the Kitten and the Cat: A Preliminary Study

Hyperthermia produces many changes in the ongoing electrical activity of the brain. One of the responses which fever can induce is seizure activity. The thalamocortical augmenting response, a complex neurophysiological response, has been related to seizure discharges. The changes in that complex neurophysiological response induced by experimental hyperthermia were assessed in adult cats and in kittens, using analytical methodology first developed in adult cats. The effect of two anticonvulsants (phenytoin and valproate) on those hyperthermia-induced changes in the thalamocortical augmenting response were compared in kittens. The differences between the effects of the two anticonvulsants on the thalamocortical augmenting response can be related to the reported clinical differences between the two anticonvulsants in patients with febrile seizures.     

Properties of K+ Conductances in Cat Retinal Ganglion Cells During the Period of Activity-mediated Refinements in Retinofugal Pathways

During ontogeny retinal ganglion cells manifest pronounced changes in excitable membrane properties. To further our understanding of the ionic conductances underlying such functional changes, the whole-cell voltage-clamp variation of the patch-clamp technique was used to record potassium currents in 220 ganglion cells dissociated from cat retinas ranging in age from embryonic day 31 to postnatal day 10. Potassium currents were isolated by blocking voltage-gated Na⁺ and Ca²⁺ currents with tetrodoxin (TTX) and CoCl₂ respectively and were characterized by their pharmacology, kinetics and voltage-dependence of activation and inactivation. In all cases, a combination of three currents accounted for the total outward calcium-independent K⁺ current: (i) a steady linear conductance; (ii) a voltage-gated transient current, l_A, and (iii) a voltage-gated sustained current, l_k. Both voltage-gated currents were affected by the application of 4-aminopyridine and tetraethylammonia (TEA): l_A showed a greater sensitivity to 4-aminopyridine, while l_k was more sensitive to TEA. Both voltagegated currents were present throughout the developmental period examined; however, the percentage of retinal ganglion cells (RGCs) expressing l_A showed a marked decline from 82% at E31 to 45% at postnatal ages. During this developmental period there was an increase in the density of the two voltage-gated and the linear conductance. Additionally, with maturation, significantly slower inactivation kinetics were observed for l_K. These findings, and our previous results dealing with maturational changes in the TTX-sensitive voltage-gated Na current, are related to the generation of excitability in developing retinal ganglion cells. Furthermore, the presence of cells with and without transient K⁺ conductance throughout development suggests that the different spiking patterns observed in RGC classes may be partially due to differences in their membrane properties.     

Electrophysiology and Pharmacology of the Corticothalamic Input to Lateral Thalamic Nuclei: an Intracellular Study in the Cat

Though most experimental evidence indicates that the corticothalamic (CT) pathway would exert a direct excitatory action on thalamic relay neurons, the electrophysiological features of this excitation have never been clearly described. A methodological problem in previous electrophysiological studies was that direct corticofugal effects on relay cells could not be separated from those mediated by collateral activation of reticular thalamic neurons. In the present study, the reticular complex was lesioned by kainic acid and the CT response of relay neurons of the ventral lateral nucleus was recorded intracellularly in cats under pentobarbital or urethane anaesthesia. Following reticular thalamic lesions, a prominent depolarization was triggered in thalamic relay cells by stimulation of the CT pathway. This depolarization strongly drove spike discharges, and its amplitude augmented when the stimulation rate exceeded 2 Hz. Tetanizing the CT input with short trains (100 - 200 Hz for 200 - 300 ms) produced a similar augmentation to test volleys for 15 - 30 s after the tetanos. The CT excitation and its frequency-dependent augmentation were depressed by ketamine injection or by local application of N-methyl-D-aspartate (NMDA) antagonists. The augmenting phenomenon appeared strictly homosynaptic. For instance, it did not appear during repetitive stimulation of the cerebellar input, nor did the CT input potentiate subthreshold synaptic potentials of cerebellar origin during a conditioning procedure. Conversely, the cerebellar excitation was depressed when it occurred during the CT depolarization. It is concluded that the direct synaptic responses induced by CT fibres in relay neurons are mediated at least partly by the activation of NMDA receptors. Moreover, the marked non-linear additivity of cerebellar and CT synaptic potentials raises questions concerning the presumed improvement of thalamic transmission of peripheral informations ensured by the CT input. Instead, both inputs could compete for control of the firing of thalamic neurons. The numerical importance of CT fibres and the strong augmenting mechanism operating at synaptic sites in the thalamus suggest that the role of the thalamus is not only to transfer peripheral informations toward the cortex, but also and mainly to feed back to the cortex a modified copy of its own neuronal constructs.     

Lamellar Organization of Pontocerebellar Neuronal Populations. A Multi-tracer and 3-D Computer Reconstruction Study in the Cat

This study deals with the three-dimensional arrangement of populations of pontocerebellar cell bodies projecting to the parafloccular complex. The fluorescent tracers rhodamine B isothiocyanate, fluoro-gold and fast blue were injected in either adjacent or separated cerebellar folia. A set of coordinates ( x, y, z ) was assigned to each retrogradely labelled cell and the total distribution reconstructed and displayed on a graphics workstation. At a large scale, we found that the majority of the cells of each labelled population (all projecting to the same folium) were confined to a lamella-shaped tissue volume. Each lamella extended from medial to lateral, and accordingly followed the curving of the pontine grey around the corticospinal and corticobulbar fibre tracts. At a smaller scale, i.e. within each lamellar subspace, the neurons belonging to one labelled population were distributed in aggregates of various shapes. To enable further analysis of the shapes of the intralaminar aggregates, we developed a computer program for unfolding of the lamellae, based on cubic B-spline approximation. The flattened reconstructions were three-dimensional polygonal windows, circumscribing the large majority of the labelled cell swarm (usually 70–80% of the total number of labelled cells in one population). The present findings, taken together with previous data on a gradual, rather than disjunctive, shift of pontocerebellar neuronal position in relation to a gradual shift of target region (Bjaalie et al., Anat Rec , 231 , 510–523, 1991), suggest that the cerebropontocerebellar system may be organized according to a set of fairly simple topographic rules.     

How Young Children Treat Objects and People: An Empirical Study of the First Year of Life in Autism

Objective. To figure out features of autism before the age of one and to explore the pathways of early social and nonsocial attention in autism through home movies.Method. Home movies of 15 children later diagnosed with autism, are compared with home movies of 13 typical children. The films of the two groups have been mixed and rated by blind observers through a Grid composed of social and nonsocial item and applied to two age ranges: 0–6 months (T1) and 7–12 months (T2). Two MANOVAs, an ANOVA and discriminant analyses were applied.Results. Significant differences between the two groups were found only for the item in the Social area at T1 but not at T2, when groups did not differ in either social or nonsocial areas. At T2 children with autism had significantly higher scores in the nonsocial area while normal children did not show significant differences between areas. Discriminant analyses revealed that social attention can distinguish the two groups at T1 but not at T2.Conclusions. The fundamental impairment of joint attention in autism could be considered a consequence of the early atypical developmental gap and of a later disconnection between attention to people and objects. Abnormal developmental trajectories for social and nonsocial attention could help us in the future to understand relationships between adaptive capacities and symptoms, and set the stage for appropriate early screening instruments.This study was supported by grant RC 6/02 from National Institute of Health.