Rightward Movement Research Articles

Doing the right thing

In this paper we take issue with two recent analyses proposed for extraposition : Analyses based on Kayne's (1984) Linear Correspondence Axiom (Kayne 1994 ; Zwart 1992, 1994) and the strictly right branching analysis of Haider (1993). We compare these to the traditional rightward movement analysis, a particular version of wich we present. It turns out that only the rightward movement account can explain the relevant data in German, including extraction from embedded clauses, coreference with and binding of elements in embedded clauses, restrictions on the distribution of embedded clauses, and constituency facts around topicalization

Gapping and P-Stranding

Jayaseelan (1990) and Lasnik and Saito (1991) observe thatEnglish Gapping exhibits properties typical of rightwardmovement. In this paper, we address the question of why this isthe case. We propose that in Gapping, a contrasted element in thefull-fledged conjunct can move leftward or rightward to create astructure for copying and that illegitimate derivations areexcluded by independently motivated constraints. As one suchconstraint, we adopt Saito‘s (1985) condition on adjunctionsites, which requires that an element adjoin to the side of thecategory which is opposite to the head. Since Saito‘s constraintrelies on the head parameter, this analysis makes the obviousprediction that Gapping constructions in head-final languagesshould involve leftward movement. We show that this is indeed thecase with Japanese. The most important theoretical consequencesare: (i) that the directionality of adjunction is constrained inLF in the same way as in overt syntax and (ii) that constraintssuch as the Right Roof Constraint and the Subjacency Conditionapply both in overt syntax and in LF. The other importantconsequence is that P-stranding is universally allowed at LF forleftward movement but not for rightward movement.

Effects of Left Heart Assist on Geometry and Function of the Interventricular Septum

Background. Right ventricular (RV) dysfunction is a common but poorly understood problem associated with mechanical left heart assist (LHA). Left ventricular unloading may affect RV function even in normal hearts by altering geometry or function of the interventricular septum, although such changes have not been well defined. Accordingly, the purposes of this study were to quantify the effects of LHA on septal geometry and function in normal swine and to assess the resultant effects on RV function. Methods. Domestic swine (50 kg, n = 10) were anesthetized and instrumented for collection of physiologic data and for open-chest LHA, which was accomplished by left atrial to subclavian artery bypass using a centrifugal pump. Both global and regional RV function data as well as two-dimensional echocardiographic data of septal geometry and function were collected at control levels and during both partial and full LHA. Short-axis echocardiographic images were obtained at the midventricular level and analyzed to quantify septal curvature (k; cm −1), systolic septal thickening (%), and systolic septal excursion (cm). Results. Partial LHA had no effect on either septal geometry or function. Full LHA resulted in decreased diastolic septal curvature (k = 0.10 ± 0.07 versus 0.42 ± 0.06 at control; p < 0.05), reduced systolic septal thickening (0.27 ± 5.23 versus 29.32 ± 8.61 at control; p < 0.05), and reversed leftward systolic septal excursion (−0.29 ± 0.11 versus 0.11 ± 0.03 at control; p < 0.05). End-diastolic septal position was shifted leftward during full LHA compared with control, but was associated with rightward systolic motion of the left ventricular mass and septum as a unit. There were no changes in global or free-wall RV function during either partial LHA or full LHA compared with control. Conclusions. Left heart assist results in marked changes in both geometry and function of the interventricular septum in normal hearts. These changes, however, do not appear to be associated with changes in either global or regional RV function. Evaluation of the septum with echocardiography may be helpful in defining strategies for clinical application of this technology.

On the Structure of the French DP

AbstractThis paper discusses and expands upon various ideas concerning the structure of nominals in general (DPs) and of French nominals in particular, with the underlying idea that CP and DP have parallel argumental and functional structure. The main topics discussed are: (i) the projection of arguments in French and English; (ii) the parameterization of N-movement, which accounts for some word order differences between French and English; (iii) the distribution of adjectives in event nominals, which reflects that of adverbs in clauses in both French and English; (iv) a peculiar case of rightward movement out of DP that provides further evidence for N-movement as well as for the claim concerning the prohibition on right adjunction of genitive nominals within DP; and (v) extraction facts that are a consequence of the status of [Spec, DP] as an A′-position in French.

Body surface isopotential T map for assessment of right ventricular volume and pressure overloads in secundum atrial septal defect.

The body surface isopotential T map was analyzed to detect right ventricular volume and pressure overloads in 25 patients with secundum atrial septal defect. Three patterns were distinguished: a T map resembling normal (type A, n = 9); that with an isolated negative area in a positive area (type B, n = 11); and that with rightward movement of maximum (type C, n = 5). Right ventricular end-diastolic volumes in types B (161 +/- 19% of normal; %N) and C (175 +/- 40% N) were significantly (p < 0.01) greater than those in controls (100 +/- 9% N) and type A (113 +/- 18% N). Right ventricular systolic pressure in type C (48 +/- 11 mmHg) was significantly (p < 0.01) higher than those in the controls (30 +/- 5 mmHg), type A (31 +/- 4 mmHg), or type B (34 +/- 5 mmHg). These results suggest that the patients with type B have right ventricular volume overload and those with type C have both volume and pressure overloads.

Responses to Opposed Directions of Motion:: Continuum or Independent Mechanisms?

Opponency between opposite directions of motion is a characteristic of many models of movement detection and is commonly invoked in explanations of the motion after-effect. If detection of opposite directions is mediated by a single mechanism, then a single, smooth psychometric function for the discrimination of global direction in random-dot kinematograms should be found as a function of the percent of directional coherence of dots in the display, ranging from 100% coherence leftwards through 0% coherence to 100% coherence rightwards. Moreover, after rightward motion adaptation, a single psychometric function should still be observed if adaptation affects the perceptual system prior to opponent interactions. If, however, leftward and rightward detectors operate independently, then the slopes of the leftward and rightward halves of the function may differ, particularly after unidirectional adaptation. We measured the probability of a “rightward” direction response for nine values of motion coherence for five observers with and without prior rightward motion adaptation. Although a smooth psychometric function was found without motion adaptation, after adaptation, the rightward half of the psychometric function was flattened whereas the leftward half remained unchanged. Such results indicate that movement direction analysers operate in a non-opponent manner. Copyright © 1996 Elsevier Science Ltd.

Eye position and target amplitude effects on human visual saccadic latencies.

Gaze shifts vary in the extent of eye and head contribution; a large amplitude and/or an eccentric ocular orbital starting position alter the participation of head movement in the shift. The interval between eye onset and head onset determines compensatory counterrolling before and after the shift and the extent of vestibular ocular reflex reduction during the shift. The latency of eye saccades in the head-fixed condition was measured with respect to target amplitude and orbital position in order to establish base-line operations of these two variables as they apply to the head-free condition. Eye movements were measured during single-step saccades in nine young adult humans. The target step, hereafter called a jump, started from three possible fixation lights; e.g., rightward saccades started from the midline (0 degree) or from -20 or -40 degrees left of the midline, with a maximum amplitude of 80 degrees. The latency of saccades starting from the primary position increased with jump amplitude (amplitude-latency relation). When the eye started eccentrically, the latency was decreased (orbital position-latency relation), with the largest jump amplitudes most affected. These changes can be related to active eye-head coordination. Thus, with a leftward maximal orbital eccentricity, compensatory eye rotation would be impossible with a rightward head movement; however, incorporating the orbital position-latency relation, the forward ocular saccade is expedited by 90 ms. Conversely, with a primary starting position, the ocular component of an 80 degrees gaze saccade could be slowed 125 ms by incorporating the amplitude-latency relation, thus facilitating a head contribution to the gaze shift. The orbital position and amplitude-latency relations were prominent in those subjects with habitually large head contributions to the gaze shift and minimal in individuals with typically small head contributions.

Vertical and Horizontal Eye Displacement During Static Pitch and Roll Postures

The positions of both eyes were measured objectively in the dark following "look straight ahead" instructions for 16 subjects at 27 combinations of static pitch and roll postures over 360 degrees of space, using an infrared video technique. Shifts in vertical version, or the doll reflex, varied sinusoidally with pitch and roll angle. At 0 degree roll, the average response has a peak-to-trough amplitude of 9.28 degrees and is symmetric about a downward eye position of 4.63 degrees. The proposed Dual Otolith Model (DOM), based on a combination of utricular and saccular inputs, provided excellent fits to the present data (R2 = 0.876) and to the data of previous studies (R2 = 0.916 to 0.994). Deviations in horizontal version varied sinusoidally with roll angle, with no significant effect of pitch angle. In general, clockwise (right-ear-down) rolls produced rightward eye movements, and counterclockwise (left-ear-down) rolls produced leftward eye movements. The average versions were symmetric about a leftward eye position of 1.14 degrees, with a peak-to-trough amplitude of 3.76 degrees. The data were well represented by the proposed Horizontal Version Model (HVM; R2 = 0.796), which depended only on utricular input.

Infants' sensitivity to uniform motion

Uniform motion across the retina is a powerful cue to the perception of self-motion. In spite of its importance for adaptive functioning, little is known about the early development of uniform motion sensitivity. Six-, 12-, and 18-week-old infants viewed random-dot kinematograms depicting leftward or rightward uniform motion. The display induced optokinetic nystagmus (OKN), which a trained observer used to judge the direction of target motion. Both speed of motion and directional coherence were varied to obtain independent motion detection thresholds. Infants of all three ages could detect uniform motion, and their detection thresholds were constant during this period of development. This is in contrast to the clear improvements in relative motion sensitivity noted previously between 6 and 18 weeks of age with a preferential looking (PL) paradigm. The developmental differences between these studies may result from: (1) separate mechanisms for detecting uniform (absolute) and differential (relative) motion; or (2) separate mechanisms underlying OKN and PL response measures.

Relations between Attentional and Intentional Neural Systems

This study explored whether preparing an arm movement influences detection of a visual stimulus. We cued subjects to respond with either a rightward or a leftward movement to the appearance of a stimulus located either in the centre, in the left, or in the right visual field. Programming a movement toward a lateral direction enhanced visual attention at that side. Rightward movements were associated with an attentional cost only for responses to a central location, while leftward movements slowed response latencies to both central and right-sided stimuli. We hypothesized that programming a rightward movement depends on the activation of intentional centers in either cerebral hemisphere. On the contrary, leftward movements might be only driven by the contralateral hemisphere.

Task-specific conjugate lateral eye movements.

Conjugate lateral eye movements induced by task-specific reflective thought were examined in 10 dextral men. Verbal and spatial stimuli designed to activate reflective thought in the left (verbal) and right (spatial) cerebral hemispheres of the brain were presented tachistoscopically in a darkened environment. Eye movements during reflective thought were monitored and scored using an infrared eye-tracking device. Reflective thought induced by the spatial task produced significantly more leftward conjugate lateral eye movement. The verbal task tended to produce more rightward and upward movements. The results are viewed as consistent with a task-specific brain-hemispheric activation model of contralateral conjugate eye movements during reflective thought.

The complementary relationship between waking and REM sleep in the oculomotor system: an increase of rightward saccades during waking causes a decrease of rightward eye movements during REM sleep

Since an inverse relationship between waking and REM sleep eye movements (EMs) has been found with respect to frequency, amplitude and direction of EMs, we evaluated variations in the percentages of horizontal rapid eye movements (REMs) during REM sleep after having increased rightward saccades during waking by means of a unilateral tachistoscopic visual test administered prior to sleep. In another condition subjects were given the same 4 h testing condition prior to sleep, the only difference being that they were instructed not to move their gaze; therefore only “attentional movements” were possible. This condition served as a control for the role of oculomotor activity in the complementary relationship between waking and REM sleep eye movements. The actual increase of rightward saccades during waking resulted in a significant decrease of rightward REMs. This effect has been observed only in the condition in which rightward eye movements were increased and it is specific for REMs of amplitude similar to those which were increased during waking by the lateralized test.

Retinotopic and directional defects in motion discrimination in humans with cerebral lesions.

We investigated the discrimination of motion direction in peripheral and central vision in 23 patients with unilateral cerebral hemispheric lesions on computed tomography or magnetic resonance imaging. We used random dot cinematograms that determined a percent coherence motion threshold for 16 points in the peripheral field and for four directions separately in central vision. We measured asymmetry of right- versus left-field peripheral discrimination (retinotopic defects) and asymmetry of central discrimination for rightward versus leftward motion (directional defects), compared with normal subjects. Five patients had directional asymmetries of foveal motion perception, all worse for motion toward the side of their lesions. One patient had a bidirectional defect for the perception of horizontal motion. For 3 of these 6, the average of all horizontal and vertical motion discrimination thresholds was also elevated. Two had contralateral retinotopic defects. One of these also had an ipsidirectional foveal defect, but the other did not. The remaining 5 patients with ipsidirectional foveal defects had hemianopias that precluded testing for coexistent retinotopic defects. The lesions of the 6 patients with ipsidirectional defects overlapped in white matter underlying the lateral temporo-occipital cortex, at the junction of Brodmann areas 19 and 37. In contrast, lesions of patients without directional defects spared this region.

Recovery from directional hypokinesia and bradykinesia in unilateral neglect

Patients with acute right hemisphere (RH) damage and left unilateral neglect may exhibit slowness in both the initiation and execution of goal-directed movements toward the contralesional side (respectively, directional hypokinesia and directional bradykinesia). We retested 13 patients with RH damage, who on initial testing 1 year earlier had shown these impairments on a visually cued sequential movement task. Initiation and execution times were measured separately for leftward and rightward movement sequences, performed in either hemispace and across the body midline. Patients with anterior/subcortical lesions exhibited directional hypokinesia and bradykinesia on initial testing, but no longer showed either after 12 months. It is suggested that the recovery exhibited by these patients was determined conjointly by residual functioning of flexible anterior/subcortical structures involved in response production, in addition to the resolution of transient secondary dysfunction (i.e., diaschisis) of posterior (parietal) areas responsible for attentional orienting and target selection. In contrast, patients with posterior (parietal) lesions continued to exhibit directional hypokinesia after 12 months, probably as a result of permanent damage to a region whose dedicated or specialised functions cannot readily be compensated by other brain areas. These results support the notion that spatial attention and goal-directed movement are subserved by a distributed network involving separate but interconnected brain regions. Distinct functional losses may be predicted, in both the acute and chronic stages postinjury, on the basis of temporary or permanent dysfunction of discrete components of this network.

Horizontal visual motion modulates focal attention in left unilateral spatial neglect.

Patients with unilateral spatial neglect are impaired in directing focal attention toward the contralesional side of space. Provision of static spatial cues on the neglected side has previously been shown to help overcome this deficit. Common movement of visual stimuli may also guide the allocation of spatial attention, although such effects have not been examined in patients with unilateral spatial neglect. Eleven patients with right hemisphere damage and clinical evidence of left unilateral spatial neglect, and 11 matched, healthy controls were tested on a task of horizontal line bisection. Lines were presented on a computer display, with a neutral, static, or slowly drifting, random dot background. Under conditions of motion, background stimuli drifted either leftward or rightward, across the full width of the display, at speeds that did not elicit optokinetic nystagmus or perceptual aftereffects. Controls were accurate in all conditions, and showed minimal effects of background conditions. By contrast, patients with left unilateral spatial neglect were sensitive to leftward background motion, showing a significant leftward shift in bisection error, relative to neutral, static, and rightward moving backgrounds. There was no significant effect of rightward motion in comparison with the neutral and static conditions. The extent to which patients were susceptible to the effects of background motion was not related to severity of unilateral spatial neglect, as measured by clinical tests. The benefits of leftward motion may reflect activity of preserved motion processing mechanisms, which provide input to an otherwise dysfunctional attentional network. The use of visual motion to assist in contralesionally guiding focal attention may be useful in the rehabilitation of unilateral spatial neglect.

Regression-contingent analyses of eye movements during sentence processing: Reply to Rayner and Sereno

Altmann, Garnham, and Dennis (1992) explored contextual influences on syntactic ambiguity resolution by monitoring eye movements during reading. In order to resolve a conflict of interpretation given that the different eye movement measures yielded different patterns, we introduced a regression-contingent analysis of reading times, separating trials according to whether the eyes departed from the region of interest with a leftward (regressive) or rightward movement. R,ayner and Sereno (1994) argue that various assumptions which they claim underlie the motivation for introducing the regression-contingent measure are in fact flawed. In this paper I demonstrate that these assumptions are incorrectly ascribed to us (while agreeing that they are incorrect), and that Rayner and Sereno's re-analysis oF an earlier study by Rayner, Garrod, and Perfetti (1992) neither questions nor threatens the generalizability of the regression-contingent measure, Finally, I discuss same of the uncertainties surrounding the interpretation of first-pass reading times which further motivate the measure we adopted in Altrnann et al.'s (1992) study.

Deficits of position sense, unilateral neglect and optokinetic stimulation

The effects of optokinetic stimulation on position sense disorders were investigated in a series of 30 patients with unilateral vascular lesions (10 right brain-damaged patients with visuo-spatial hemineglect, 10 right brain-damaged patients without visuo-spatial hemineglect, 10 left brain- damaged patients), and 10 control subjects. The position sense deficit was more severe in right brain- damaged patients with neglect, where both the contralateral and the ipsilateral arm were involved. Optokinetic stimulation was effective only in right brain-damaged patients with neglect: stimulation with a leftward movement (contralateral to the side of the hemispheric lesion) improved the position sense deficit, while stimulation with a rightward (ipsilateral) movement produced a worsening of the performance level. These findings suggest that in right brain-damaged patients with neglect the position sense deficit has a nonsensory component, related to neglect, which may be affected by optokinetic stimulation. The role of the derangement of sensory and perceptual-egocentric representations of the body and of extrapersonal space in producing position sense disorders is discussed.

Movement direction analysers: Independence and bandwidth

Opponent, or ratio, models of movement direction perception propose that pairs of analysers, sensitive to opposite directions, are linked in an opponent fashion. Alternatively, distribution models posit independence of movement direction analysers. To investigate analyser independence, a direction-selective adaptation experiment was conducted in which motion coherence thresholds for random-dot apparent motion stimuli were measured for upward, downward, leftward and rightward motion with and without prior adaptation to rightward motion. Coherence thresholds for rightward motion were elevated on average by 0.64 log units after adaptation. Thresholds for motion in the other directions remained unchanged. Since opponent models predict enhanced sensitivity after adaptation for the direction opposite that of adaptation, these results suggest that movement direction analysers operate independently. In a second experiment subjects adapted to a bidirectional stimulus containing an equal number of leftward and rightward moving dots. Leftward and rightward coherence thresholds were elevated even though no motion aftereffects were produced. A third experiment in which coherence thresholds for test directions within a narrow range were measured with and without prior adaptation to motion in the direction of the range's mean showed that threshold elevation was maximal when test and adaptation direction were matched and fell off as the difference in adaptation and test direction increased. The resulting functions indicate that the bandwidth of movement direction analysers is between ± 35and+- 40deg, a value consistent with reported mean directional tuning functions of movement sensitive units in the middle temporal area but smaller than previously reported psychophysical values.

An objective criterion for apparent motion based on phase discrimination.

Studies of visual apparent motion have relied on observers' subjective self-reports of experienced motion, for which there is no objective criterion of right or wrong. A new method of phase discrimination is reported that may offer an objective indicator of apparent motion. Ss discriminated the direction of an objective 75-ms phase shift, away from strict temporal alternation of 2 stimulus dots. Accuracy increased from 50% to 100% correct as rate of alternation and distance between the dots was decreased, in conformity with Korte's third law of apparent motion. This and additional evidence suggests that phase discrimination may be mediated by asymmetries between the experienced strengths of leftward and rightward motion. Phase discrimination may also be adaptable to the study of apparent motion and related phenomena in other sensory modalities and other animal species.

Spatiotemporal sensitivity following lesions of area 18 in the cat

The contribution of cat area 18 to spatiotemporal sensitivity and to motion processing was assessed in cats with unilateral ibotenic acid lesions placed in physiologically identified portions of area 18. The lesions were centered in the representation of the lower right visual field, about 10 degrees from the vertical meridian. In one of the animals, the lesion invaded a small portion of area 19. We measured detectability of various spatiotemporal stimuli placed within the lesioned and intact portions of the visual field, while monitoring eye position with a scleral search coil. We found a loss of sensitivity to gratings of low and intermediate spatial frequency, within the ablated portion of the visual field. The sensitivity loss was 0.6-1.0 log units at low and intermediate spatial frequencies, and decreased at higher frequencies with the resolution limits remaining intact. The loss extended over a range of temporal frequencies for both drifting gratings and grating modulated in counterphase. We also found that within the lesioned hemifield, the cats were unable to discriminate between rightward and leftward motion even at the highest contrasts. These results demonstrate that area 18 plays an important role in detecting drifting low- and intermediate-spatial-frequency targets and is likely to represent a critical stage in the cortical processing of motion signals.