Multiple frames of reference for pointing to a remembered target

Pointing with an unseen hand to a visual target that disappears prior to movement requires maintaining a memory representation about the target location. The target location can be transformed either into a hand-centered frame of reference during target presentation and remembered under that form, or remembered in terms of retinal and extra-retinal cues and transformed into a body-centered frame of reference before movement initiation. The main goal of the present study was to investigate whether the target is stored in memory in an eye-centered frame, a hand-centered frame or in both frames of reference concomitantly. The task was to locate, memorize, and point to a target in a dark environment. Hand movement was not visible. During the recall delay, participants were asked to move their hand or their eyes in order to disrupt the memory representation of the target. Movement of the eyes during the recall delay was expected to disrupt an eye-centered memory representation whereas movement of the hand was expected to disrupt a hand-centered memory representation by increasing movement variability to the target. Variability of movement amplitude and direction was examined. Results showed that participants were more variable on the directional component of the movement when required to move their hand during recall delay. On the contrary, moving the eyes caused an increase in variability only in the amplitude component of the pointing movement. Taken together, these results suggest that the direction of the movement is coded and remembered in a frame of reference linked to the arm, whereas the amplitude of the movement is remembered in an eye-centered frame of reference.     

A common processing system for duration, order and spatial information: evidence from a time estimation task

The aim of the present study was to verify whether duration, order and space representations share common mechanisms. A two-alternative time estimation paradigm was implemented in two experiments in which subjects had to judge whether the first or the second tone in a pair was shorter (or longer) and to respond by pressing a left or a right key. In Experiment 1, subjects were more accurate in conditions where the first tone was shorter or the second tone was longer, with no effects of spatial information. In Experiment 2, a modification of the paradigm allowed us to demonstrate the presence of a SNARC-like effect, as evidenced by the interaction between order and response key, and of a second-order interaction among duration, order and space. These findings seem consistent with the hypothesis that processing of these three mental categories is subserved by a common mechanism, representing duration and order information according to a spatially-defined magnitude system.     

Parallel processing of multisensory information concerning self-motion

Summary Cats trained to stand on a platform exhibit postural responses to dynamic tilting that appear to be based on an internal reference model of body geometry and the environment rather than directly on sensory inputs, as in a classical reflex chain. The data presented show an independent control of global variables of limb geometry, the length and the orientation, resulting from a parallel processing of multisensory inputs into separate central representations of body tilt. Limb length and orientation changes have completely different response dynamics and can be decoupled by appropriate manipulation of sensory information about self-motion.     

Parallel and sequential information processing in animals as a function of different hemispheres

The procedure of motor-food conditioned reflexes in conjunction with unilateral decortication of the hemispheres by means of spreading depression was used in experiments on 53 rats. Differentiation of geometric figures, combined into simultaneous complexes or chain stimuli, presented simultaneously or sequentially, was developed. It was shown that lateralization of predominant disturbances of analysis depends not on the type of stimuli used, but on the nature of their presentation. In the case of simultaneous presentation, the most profound disturbances occurred after the right hemisphere was disconnected, and in the case of sequential presentation, as a result of inactivation of the left hemisphere. The presence of a simultaneous processor in the right hemisphere of the animals and a sequential processor in the left is suggested.Translated from Fiziologicheskii Zhurnal SSSR imeni I. M. Sechenova, Vol. 68, No. 6, pp. 723–728, June, 1982.     

Parallel processing of physical and lexical auditory information in humans

We usually process auditory information at the physical level (e.g., pitch or side of presentation) and the formal level (e.g., semantic or syntax) simultaneously. However, most physiological studies investigate either the former or the latter level of processing. In this experiment, words belonging to three lexical categories (nouns, verbs, and adverbs) were randomly presented to the right or left ear. Participants were required to count all nouns presented on the relevant side. All side-relevant stimuli elicited two negativities between 100-250 and 450-650 ms post-stimulus. Nouns yielded more positive potential amplitudes between 200 and 700 ms than verbs and adverbs. This effect was observed for words presented in both relevant and irrelevant ear, i.e., it was independent of whether nouns were targets or not. After 600 ms post-stimulus, a P300-like wave was recorded to target nouns only. This component was maximal at left temporal sites. The data contradict the hierarchic processing hypothesis (first side selection, then target selection) and indicate parallel processing of physical and lexical information. Implications for the issue of language specificity of brain potentials are discussed.     

An evaluation of spatial information processing in aged rats

The spatial learning abilities of young, middle-age, and senescent rats were investigated in two experiments using several versions of the Morris water maze task. In Experiment 1, Long-Evans hooded rats were trained to find a submerged escape platform hidden within the water maze. During this phase of testing, aged rats exhibited acquisition deficits compared with either young or middle-age subjects. With continued training, however, all age groups eventually achieved comparable asymptotic levels of performance. Subsequent testing in Experiment 1 revealed that following original training, aged rats were not impaired in learning a novel escape location or in their ability to locate a visible, cued escape platform. In an attempt to identify the basis of the age-related impairments observed in Experiment 1, naive young and aged rats in Experiment 2 were initially tested for their ability to locate a cued escape platform in the water maze. During this phase of testing, the escape latencies of both young and aged rats rapidly decreased to equivalent asymptotic levels. Subsequent analyses revealed that following cue training, young subjects exhibit a significant spatial bias for the region of the testing apparatus where the platform was positioned during training. In contrast, aged rats showed no spatial bias. Training was continued in Experiment 2 using a novel submerged platform location for each subject. During these place training trials, the escape latencies of senescent rats were longer than those of young subjects. These impairments were also accompanied by a lack of spatial bias among aged rats relative to young control subjects.(ABSTRACT TRUNCATED AT 250 WORDS)     

Touch responses made to remembered and visual target locations in the dark: a human psychophysical study

Saccadic eye movements made to remembered locations in the dark show a distinct up-shift in macaque monkey, and slight upward bias in humans (Gnadt et al. 1991). This upward bias created in the visual spatial mapping of a saccade may be translated downstream in a hand/touch movement. This error could possibly reveal (a) information about the frames of reference used in each scenario and (b) the sources of this error within the brain. This would suggest an early planning stage if they are shared, or a later stage if the errors are distinct. Methods: Eight human subjects performed touch responses to a touch screen monitor to both visual and remembered target locations. The subjects used a high-resolution touch-screen monitor, a bite bar and chin-rest for restricting head movements during responses. All target locations were 20° vectors from the central starting position in horizontal, vertical and oblique planes of motion. Results: Subjects were accurate to both visual and remembered target locations with little variance. Subject means showed no significant differences between control and memory trials; however, a distinct asymmetry was observed between cardinal and oblique planes during memory trials. Subjects consistently made errors to oblique locations during touches made to the remembered location that was not evident in control conditions. This error pattern revealed a strong hypermetric tendency for oblique planes of touches made to a remembered location.     

Behavioral dynamics of intercepting a moving target

From matters of survival like chasing prey, to games like football, the problem of intercepting a target that moves in the horizontal plane is ubiquitous in human and animal locomotion. Recent data show that walking humans turn onto a straight path that leads a moving target by a constant angle, with some transients in the target-heading angle. We test four control strategies against the human data: (1) pursuit, or nulling the target-heading angle beta, (2) computing the required interception angle beta (3) constant target-heading angle, or nulling change in the target-heading angle beta and (4) constant bearing, or nulling change in the bearing direction of the target psi which is equivalent to nulling change in the target-heading angle while factoring out the turning rate (beta - phi) We show that human interception behavior is best accounted for by the constant bearing model, and that it is robust to noise in its input and parameters. The models are also evaluated for their performance with stationary targets, and implications for the informational basis and neural substrate of steering control are considered. The results extend a dynamical systems model of human locomotor behavior from static to changing environments.     

Importance of the temporal structure of movement sequences on the ability of monkeys to use serial order information

The capacity to acquire motor skills through repeated practice of a sequence of movements underlies many everyday activities. Extensive research in humans has dealt with the importance of spatial and temporal factors on motor sequence learning, standing in contrast to the few studies available in animals, particularly in nonhuman primates. In the present experiments, we studied the effect of the serial order of stimuli and associated movements in macaque monkeys overtrained to make arm-reaching movements in response to spatially distinct visual targets. Under different conditions, the temporal structure of the motor sequence was varied by changing the duration of the interval between successive target stimuli or by adding a cue that reliably signaled the onset time of the forthcoming target stimulus. In each condition, the extent to which the monkeys are sensitive to the spatial regularities was assessed by comparing performance when stimulus locations follow a repeating sequence, as opposed to a random sequence. We observed no improvement in task performance on repeated sequence blocks, compared to random sequence blocks, when target stimuli are relatively distant from each other in time. On the other hand, the shortening of the time interval between successive target stimuli or, more efficiently, the addition of a temporal cue before the target stimulus yielded a performance advantage under repeated sequence, reflected in a decrease in the latency of arm and saccadic eye movements accompanied by an increased tendency for eye movements to occur in an anticipatory manner. Contrary to the effects on movement initiation, the serial order of stimuli and movements did not markedly affect the execution of movement. Moreover, the location of a given target in the random sequence influenced task performance based on the location of the preceding target, monkeys being faster in responding as a result of familiarity caused by extensive practice with some target transitions also used in the repeated sequence. This performance advantage was most prominently detectable when temporal prediction of forthcoming target stimuli was optimized. Taken together, the present findings demonstrate that the monkey’s capacity to make use of serial order information to speed task performance was dependent on the temporal structure of the motor sequence.     

组学大数据环境下的基因变异信息并行处理与分析

随着第二代测序技术的发展与应用,其产生的测序数据也呈现快速的增长趋势,如何有效、快速、稳定地对海量测序数据进行分析成为生物研究领域迫切的需求。目前许多传统的测序数据分析软件仅支持单一功能,并不具备完整的数据分析能力,应对海量的测序数据时其处理能力也显著不足。为了应对上述问题,本文设计了一款基于Hadoop框架的测序数据分析软件,整合了现今生物研究领域内常用的多款序列分析软件,从而实现了对测序序列数据的自动化分析。该软件输入原始的测序数据后,经过碱基质量控制、序列比对、SNP位点信息提取、突变基因信息生成等几个过程,最终输出详细的突变基因信息报告。该软件实现了自动化的数据分析,提高了数据分析的效率,极大减轻了数据分析人员的工作量。     

Dissociating the role of the parietal cortex and dorsal hippocampus for spatial information processing

Dorsal hippocampus, parietal cortex, and control lesioned rats were tested on both a metric and topological task. The metric task consisted of 2 different objects placed 68 cm apart on a cheese board. After habituation, the objects were moved to a separation of 38 cm on Day 1 and to a separation of 98 cm on Day 2. The topological task consisted of 4 different objects placed in a square orientation. After habituation, the first 2 objects were switched, and after the rats habituated to that change, the back 2 objects were switched. This was repeated on a different day with 4 new objects. The data suggest that the hippocampus is necessary for metric representations, whereas the parietal cortex is necessary for topological representations.     

Lesions of the dorsal hippocampus or parietal cortex differentially affect spatial information processing

The present experiments used 2 versions of a modified Hebb-Williams maze to test the role of the dorsal hippocampus (dHip) and parietal cortex (PC) in processing allocentric and egocentric space during acquisition and retention. Bilateral lesions were made to either the dHip or PC before maze testing (acquisition) or after maze testing (retention). The results indicate that lesions of the dHip impair allocentric maze acquisition, whereas lesions of the PC impair egocentric maze acquisition. During retention, lesions of the PC produced a significant impairment on both maze versions, whereas lesions of the dHip produced short-lived, transient impairments on both maze versions. These results suggest that during acquisition, the hippocampus and PC process spatial information in parallel; however, long-term retention of spatial information requires the PC with the dHIP as necessary for retrieval and/or access but not necessarily storage.     

Combining proprioception and touch to compute spatial information

Localising a tactile stimulus in egocentric space involves integrating information from skin receptors with proprioceptive inputs about body posture. We investigated whether body posture automatically influences tactile spatial judgements, even when it is irrelevant to the task. In Experiment 1, participants received two successive tactile stimuli on the forearm and were asked to indicate whether the first or second touch of the pair was closer to an anatomical body landmark, either the wrist or the elbow. The task was administered in three experimental conditions involving different body postures: canonical body posture with extended forearm and hand pointing distally; a non-canonical body posture with forearm and hand pointing vertically up at 90° and a ‘reversed’ body posture with the elbow fully flexed at 180°, so that the hand pointed proximally. Thus, our task required localising touch on the skin and then relating skin locations to anatomical body landmarks. Critically, both functions are independent of the posture of the body in space. We nevertheless found reliable effects of body posture: judgement errors increased when the canonical forearm posture was rotated through 180°. These results were further confirmed in Experiment 2, in which stimuli were delivered to the finger. However, additionally reversing the canonical posture of the finger, as well as that of the forearm, so that the finger was restored to its canonical orientation in egocentric space, restored performance to normal levels. Our results confirm an automatic process of localising the body in external space underlying the process of tactile perception. This process appears to involve a combination of proprioceptive and tactile information.     

Role of the posterior parietal association cortex in the processing of spatial event information

Humans and monkeys with damage to the parietal association cortex (PC) exhibit deficits on visual-spatial tasks that are often dependent upon the attentional requirements of the task at hand. In order to test whether there is a correspondence between humans and rats in terms of the function of PC in the processing of spatial information, separate groups of rats were trained in two list-learning tasks, a win-stay task and a win-shift task, on an eight-arm radial maze. It is assumed that these two tasks vary in degree of required attention effort, because the win-shift rule is considerably easier for the rat to learn than the win-stay rule. One group of animals in each condition was given preoperative training before receiving bilateral aspiration lesions of PC. Another group in each condition received PC lesions prior to training. The results indicated that animals with PC lesions are unable to acquire either the win-stay or the win-shift rule. However, of the animals with preoperative training, only the win-stay trained animals were deleteriously affected by the brain lesion. The win-shift animals showed no postoperative decline in performance. Because rats with PC lesions are only impaired on the more demanding spatial task, these results are consistent with the human clinical observations.     

Cortex,striatum and cerebellum: control of serial order in a grooming sequence

Summary Rats emit grooming actions in sequences that follow characteristic patterns of serial order. One of these patterns, a syntactic chain, has a particularly stereotyped order that recurs spontaneously during grooming thousands of times more often than could occur by chance. Previous studies have shown that performance of this sequence is impaired by excitotoxin lesions of the corpus striatum. In this study we examined whether the striatum is unique in its importance to this behavioral sequence or whether control of the sequence instead depends equally upon the cortex and cerebellum. In two experiments, a fine-grained behavioral analysis compared the effects of striatal ablation to the effects of motor cortex ablation, ablation of the entire neocortex, or ablation of the cerebellum. Cortical and cerebellar aspiration produced mere temporary deficits in grooming sequences, which appeared to reflect a general factor that was nonsequential in nature. Only striatal damage produced a permanent sequential deficit in the coordination of this syntactic grooming chain. We conclude that the striatum has a unique role in the control of behavioral serial order. This striatal role may be related to a number of sequential disorders observed in human diseases involving the striatum.     

Saccadic foveation of a moving visual target in the rhesus monkey

When generating a saccade toward a moving target, the target displacement that occurs during the period spanning from its detection to the saccade end must be taken into account to accurately foveate the target and to initiate its pursuit. Previous studies have shown that these saccades are characterized by a lower peak velocity and a prolonged deceleration phase. In some cases, a second peak eye velocity appears during the deceleration phase, presumably reflecting the late influence of a mechanism that compensates for the target displacement occurring before saccade end. The goal of this work was to further determine in the head restrained monkey the dynamics of this putative compensatory mechanism. A step-ramp paradigm, where the target motion was orthogonal to a target step occurring along the primary axes, was used to estimate from the generated saccades: a component induced by the target step and another one induced by the target motion. Resulting oblique saccades were compared with saccades to a static target with matched horizontal and vertical amplitudes. This study permitted to estimate the time taken for visual motion-related signals to update the programming and execution of saccades. The amplitude of the motion-related component was slightly hypometric with an undershoot that increased with target speed. Moreover, it matched with the eccentricity that the target had 40-60 ms before saccade end. The lack of significant difference in the delay between the onsets of the horizontal and vertical components between saccades directed toward a static target and those aimed at a moving target questions the late influence of the compensatory mechanism. The results are discussed within the framework of the "dual drive" and "remapping" hypotheses.     

Schizophrenia is a disorder of higher order hierarchical processing

Schizophrenia is a mental disorder in which the patient manifests with auditory hallucinations, paranoid or bizarre delusions, and disorganized speech and thinking. It is associated with significant social dysfunction. There are many hypotheses regarding schizophrenia. Most of these focus on schizophrenia as a manifestation of abnormalities from genetic [Mulle JG. Genomic structural variation and schizophrenia. Curr Psychiatry Rep 2008;10(2):171–7], viral [Fruntes V, Limosin F. Schizophrenia and viral infection during neurodevelopment: a pathogenesis model? Med Sci Monit 2008;14(6):RA71–7], neurochemical [e.g. dopamine (Lewis DA, Akil M. Cortical dopamine in schizophrenia: strategies for postmortem studies. J Psychiatr Res 1997;31(2):175–95) or interactions between neurotransmitters (Duncan GE, Sheitman BB, Lieberman JA. An integrated view of pathophysiological models of schizophrenia. Brain Res Brain Res Rev 1999;29(2):250–64)] or brain structural [Kotrla KJ, Weinberger DR. Brain imaging in schizophrenia. Annu Rev Med 1995;46:113–22] origins. Most of these hypotheses do not account for how or why these presumed causes lead to the manifestations of schizophrenia. We argue that brain structure and function is compatible with a hierarchical processing structure that forms the basis for perception and thought in healthy humans. We propose that perturbations of the types listed above lead to disruption of higher levels of perception and hierarchical temporal processing by the brain and that this constitutes the core deficit in schizophrenia.We present evidence that this model explains many of the features of schizophrenia and we make a series of predictions about schizophrenia.     

Intercepting a moving target: effects of temporal precision constraints and movement amplitude

The effects of temporal precision constraints and movement amplitude on performance of an interceptive aiming task were examined. Participants were required to strike a moving target object with a "bat" by moving the bat along a straight path (constrained by a linear slide) perpendicular to the path of the target. Temporal precision constraints were defined in terms of the time period (or window) within which contact with the target was possible. Three time windows were used (approx. 35, 50 and 65 ms) and these were achieved either by manipulating the size of the bat (experiment 1a), the size of the target (experiment 1b) or the speed of the target (experiment 2). In all experiments, movement time (MT) increased in proportion to movement amplitude but was only affected by differences in the temporal precision constraint if this was achieved by variation in the target's speed. In this case the MT was approximately inversely proportional to target speed. Peak movement speed was affected by temporal accuracy constraints in all three experiments: participants reached higher speeds when the temporal precision required was greater. These results are discussed with reference to the speed-accuracy trade-off observed for temporally constrained aiming movements. It is suggested that the MT and speed of interceptive aiming movements may be understood as responses to the spatiotemporal constraints of the task.