Manual asymmetries in visually directed aiming.

Hypothesized that the right hand–hemisphere system is faster at processing visual feedback. In Study 1, 12 male undergraduates pointed at a target using a range of movement times under 2 illumination conditions: lights-on and lights-off in which only the target light remained visible following initiation of the aiming movement. While the results confirm that movement accuracy deteriorated less with increased speed for the right hand, the feedback interpretation for hand differences in speed–accuracy tradeoff was not supported. In Study 2, with the same Ss, no effect of illumination was apparent, suggesting that visual information available during the course of the movement was not useful. The right-hand advantage in pointing accuracy remained. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Asymmetries in the preparation and control of manual aiming movements.

Conducted 2 experiments with 20 undergraduates to determine if typical right hand target aiming advantages could be reduced or eliminated by increasing the spatial demands of the aiming task. In Exp 1, right hand advantages were found for both movement time and error regardless of spatial characteristics of the task. When a greater degree of spatial uncertainty was introduced in Exp 2, Ss exhibited a left hand reaction time advantage. Taken together, results suggest that the right cerebral hemisphere may have a special role to play in preparing the spatial aspects of an aiming movement, while the left hemisphere is more important for movement execution. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Manual asymmetries and saccadic eye movements in right-handers during single and reciprocal aiming movements

The aim of the present study was to establish whether gracile afferents to the inferior olive are topographically organized and whether such inputs coincide with the location of cells that output to the hindlimb C1 zone in the cerebellar posterior lobe. Small injections (n=15) of the anterograde tracers Fluoro-Ruby or biotinylated dextran amine were made into gracile, resulting in anterograde labelling often distributed in partially separate, rostrocaudally directed columns within the lateral half of the contralateral rostral dorsal accessory olive (rDAO). In 12 cases, anterograde labelling was also located within the caudolateral medial accessory olive. Evidence for a topographical organization was obtained, suggesting that medial gracile targets only the most lateral part of rDAO, whereas lateral gracile also targets more medial parts. Gracile injections centred dorsally also resulted in more extensive terminal fields in rDAO than similar sized injections centred ventrally which may relate to the representation of the distal hindlimb in dorsal gracile (e.g., Millar and Basbaum, 1975). Injections of retrograde tracer (green beads) into the C1 zone in the ipsilateral caudal paramedian lobule (7 cases), resulted in retrograde cell labelling in the middle one-third of contralateral DAO in two columns that fused caudally. The proportion of labelled cells that overlapped with anterograde labelled terminals was related to the dorsoventral locus of the gracile injection site: gracile injections centred dorsally produced the largest degree of overlap and therefore, potentially, the greatest functional convergence. In summary, the results suggest that a topographical organization is present within the gracilo-olivo-cerebellar projection which is discussed in relation to the functional organization of the olivocerebellar system.     

Hand movement asymmetries during verbal and nonverbal tasks.

12 male and 12 female right-handed undergraduates were videotaped while they assembled blocks to perform a series of verbal and nonverbal tasks and a neutral (nonlateralized) task. Analysis of the videotapes revealed that the frequency of movement of one hand relative to the other changed systematically with the cognitive nature of the task, but only for movements playing a functional role in task performance. For the majority of such movements, verbal tasks elicited a greater proportion of right-hand use than did a neutral task, while nonverbal tasks elicited a greater proportion of left-hand use than did a neutral task. These shifts may have reflected the engagement of lateralized problem-solving systems within the 2 hemispheres. (French abstract) (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The influence of visual target and limb information on manual aiming.

Conducted 2 experiments to determine the impact of visual target information, visual limb information, and a no vision target-pointing delay on manual aiming accuracy. In Exp I, 10 undergraduates made target pointing movements with a stylus from a home switch to the center of a target pad. Movement time was recorded under different lighting conditions. In Exp II, 10 undergraduates performed the same task under stable lighting conditions. Results indicate that visual target information was more important than limb information in determining movement accuracy and demonstrate that it was not necessary for target information to be physically present, since a visual representation of the movement environment persisted for a brief period after visual occlusion. Results contradict the findings of L. G. Carlton (see record 1982-02570-001). (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The influence of uncertainty and premovement visual information on manual aiming.

Conducted 2 experiments in which target uncertainty and the visual information available before and during a target-aiming movement were varied. 10 undergraduates participated in each of the studies. In both experiments, target uncertainty failed to interact with the visual manipulations. Findings support the idea that a visual representation contains general information about the layout of the movement environment. Data also provide evidence against the notion that a specific motor program is structured while vision is available and executed later. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Disentangling the effects of attentional and amplitude asymmetries on relative phase dynamics.

Attentional asymmetry in rhythmic interlimb coordination induces an asymmetry in relative phase dynamics, allegedly reflecting an asymmetry in coupling strength. However, relative phase asymmetries may also be engendered by an attention-induced difference between the amplitudes (and hence the preferred frequencies) of the limb movements. The authors conducted 3 experiments to dissociate those (not mutually exclusive) potential effects. Controlled manipulations of amplitude disparity and attentional focus, both alone and combined, revealed that variations in amplitude disparity had the expected effects, but produced evidence against the currently prevailing interpretation that attentional asymmetry affects the relative phase dynamics through an asymmetry in coupling strength. Implications of these findings are discussed vis-à-vis recent empirical findings and extant dynamical models. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Path curvature in workspace and in joint space: evidence for coexisting coordinative rules in aiming

In this study we tried to establish whether point-to-point aiming movements are planned in workspace, joint space, or both. Eight right-handed subjects performed horizontal, vertical, and diagonal aiming movements on a transversal plane. Movements were performed at several speeds. Curvature variations of the hand and corresponding joint-space paths were investigated as a function of position, direction, and speed. Straightness of hand paths predominated for vertical movements but was systematically violated for horizontal and top-right to bottom-left movements. Furthermore, the hand-path curvature of the latter movements increased with speed. Joint-space paths showed more deviation from a straight line than hand paths except for top-left to bottom-right movements in which the paths were equally curved. A comparison of normalized path curvatures at the hand and joint level indicated that in aiming, the coordinative rule of straight-line production seems to apply to both workspace and joint-space planning. The present findings confirm Kawato's (1996) views that optimization processes operate concurrently at the two control levels of arm-trajectory formation under study.     

The role of peripheral and central visual information for the directional control of manual aiming movements.

Seeing one's hand in visual periphery has been shown to optimize the directional accuracy of a sweeping hand movement, which is consistent with J. Paillard's (1980; Paillard and B. Amblard, 1985) two-channels model of visual information processing. However, contrary to this model, seeing one's hand in central vision, even for a brief period of time, also resulted in optimal directional accuracy. In 3 experiments, this study tested two opposing hypotheses proposed to explain the latter finding, and also determined whether additional support could be found for the existence of a visual kinetic channel. Results indicated that seeing one's hand in central vision, even for a very short delay, resulted in the same accuracy as being permitted to see one's hand for the duration of the whole movement. This suggests that seeing one's hand around the target might enable one to code its location and that of the target within a single frame of reference and, thus, facilitate movement planning. In addition, seeing one's hand in motion while in visual periphery permitted a better directional accuracy than when this information was not available, suggesting that the movement vector, which is planned prior to movement initiation, can be quickly updated following movement initiation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effect of the Müller-Lyer illusion on the planning and control of manual aiming movements.

Two experiments used Müller-Lyer stimuli to test the predictions of the planning-control model (S. Glover, 2002) for aiming movements. In Experiment 1, participants aimed to stimuli that either remained the same or changed upon movement initiation. Experiment 2 was identical except that the duration of visual feedback for online control was manipulated. The authors found that the figures visible during movement planning and online control had additive effects on endpoint bias, even when participants had ample time to use visual feedback to modify their movements (Experiment 2). These findings are problematic not only for the planning-control model but also for A. D. Milner and M. A. Goodale's (1995) two visual system explanation of illusory bias. Although our results are consistent with the idea that a single representation is used for perception, movement planning, and online control (e.g., V. H. Franz, 2001), other work from our laboratory and elsewhere suggests that the manner in which space is coded depends on constraints associated with the specific task, such as the visual cues available to the performer. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Alcoholism, aging, and functional cerebral asymmetries.

Reviews research concerning the possible relationship between cognitive decline and abnormal hemispheric asymmetries in alcoholic and aging individuals. Because the deteriorative effects of alcoholism on the central nervous system have suggested greater visuospatial than language-related functional impairments, numerous investigators had hypothesized that right-hemisphere integrity may be selectively disrupted (rather than the left hemisphere). Furthermore, performance on diverse perceptual and cognitive tests used to measure right-hemisphere functions in alcoholics had been observed to decline with normal chronological aging as well, thereby raising the possibility that certain neuropsychological deficits associated with alcoholism (presumably related to right-hemispheric decline) are identical to those associated with aging. However, an extensive review of empirical research findings on cerebral asymmetries both in alcoholics and in aging individuals suggested that their patterns of functional laterality are similar to those of normal controls. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Parental antagonism, relatedness asymmetries, and genomic imprinting

The theory of inclusive fitness can be modified to consider separate coefficients of relatedness for an individual's maternal and paternal alleles. A gene is said to have parentally antagonistic effects if it has an inclusive fitness benefit when maternally derived, but an inclusive fitness cost when paternally derived (or vice versa). Parental antagonism favours the evolution of alleles that are expressed only when maternally derived or only when paternally derived (genomic imprinting).     

Hand path priming in manual obstacle avoidance: Evidence for abstract spatiotemporal forms in human motor control.

Previous research suggests that motor equivalence is achieved through reliance on effector-independent spatiotemporal forms. Here the authors report a series of experiments investigating the role of such forms in the production of movement sequences. Participants were asked to complete series of arm movements in time with a metronome and, on some trials, with an obstacle between 1 or more of the target pairs. In moves following an obstacle, participants only gradually reduced the peak heights of their manual jumping movements. This hand path priming effect, scaled with obstacle height, was preserved when participants cleared the obstacle with 1 hand and continued with the other, and it was modulated by future task demands. The results are consistent with the hypothesis that the control of movement sequences relies on abstract spatiotemporal forms. The data also support the view that motor programming is largely achieved by changing just those features that distinguish the next movement to be made from the movement that was just made. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The structure of attentional control: Contingent attentional capture by apparent motion, abrupt onset, and color.

Five spatial cuing experiments tested 2 hypotheses regarding attentional capture: (1) Attentional capture is contingent on endogenous attentional control settings, and (2) attentional control settings are limited to the distinction between dynamic and static discontinuities as proposed by C. L. Folk et al (see record 1993-12300-001). In Exps 1 and 2, apparent-motion precues produced significant costs in performance for targets signaled by motion but not for targets signaled by color or abrupt onset. Exp 3 established that this pattern is not due to differences in the difficulty of target discrimination. Exps 4 and 5 revealed asymmetric capture effects between abrupt onset and apparent motion related to stimulus salience. Results support the hypotheses of Folk et al and suggest that stimulus salience may also play a role in attentional capture. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Similar attentional, frequency, and associative effects for pseudohomophones and words

Between the presentation and recall of 1 or 5 digits, Ss performed a secondary task of naming a visually presented letter string--a pseudohomophone (e.g., FOLE, HOAP) or its real-word counterpart (FOAL, HOPE). Memory load interacted with frequency (HOPE vs. FOAL, HOAP vs. FOLE) but not with lexicality (HOPE vs. HOAP, FOAL vs. FOLE). This outcome counters models in which nonwords are named by a slow (resource-expensive) process that assembles phonology and words are named by a fast (resource-inexpensive) process that accesses lexical phonology. When the associative priming-of-naming task was secondary to the memory task, pseudohomophone associative priming (HOAP-DESPAIR, FOLE-HORSE) equaled associative priming (HOPE-DESPAIR, FOAL-HORSE) and was affected in the same way by memory load. Assembled phonology seems to underlie the naming of both words and nonwords.     

Top-down controlled, delayed selection in the attentional blink.

In a previous study, it was shown that the attentional blink (AB)--the failure to recall the 2nd of 2 visual targets (T1 and T2) presented within 500 ms in rapid serial visual presentation--is reduced when T2 is preceded by a distractor that shares a feature with T2 (e.g., color; Nieuwenstein, Chun, van der Lubbe & Hooge, 2005). Here, this cuing effect is shown to be contingent on attentional set. For example, a red distractor letter preceding a green digit T2 is an effective cue when the task is to look for red and green digits, but the same red cue is relatively ineffective when the task is to look for only green digits or when the color of T2 is not specified. It is also shown that cuing is not interrupted by a distractor intervening between the cue and T2. These findings provide evidence for a contingent, delayed selection account of the AB. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Congruency, attentional set, and laterality effects with emotional words.

The present study investigated the influence of attention and word-emotion congruency on auditory asymmetries with stimuli that include verbal and emotional components. Words were presented dichotically to 80 participants and were pronounced in either congruent or incongruent emotional tones. Participants were asked to identify the presence of a target word or emotion under 1 of 2 conditions. The blocked condition required detection of a word or emotional target in separate blocks. In the randomized condition, the target was changed across trials by means of a postcue. A right-ear advantage (REA) and a left-ear advantage (LEA) were found for word and emotion targets, respectively. However, the finding of a Condition × Stimulus Type × Ear × Congruency interaction indicated that in the randomized condition, a REA was obtained for words when the stimuli were congruent and a LEA was observed for emotions when the stimuli were incongruent. The findings suggest that randomizing the target reduced the influence of the attentional set established by blocking the target. It is likely that this promoted the detection of hemispheric interference in the randomized condition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)