Dual-task interference as an indicator of on-line programming in simple movement sequences.

The probe reaction time paradigm was used to investigate the processing demands of an elbow extension and 2 types of extension-flexion movements, one with a short pause time (50–100 ms) at reversal and another with a long pause time (250–300 ms). The probe task consisted of a bite response to an auditory signal. The locations of the probe were determined by on-line analysis of electromyographic activity and kinematic profiles. Depending on the temporal location of the probe relative to the initiation of the flexion phase, participants either initiated the masseter and biceps muscles successively or grouped them together as a single conjoint response. Results are discussed in terms of limitations during on-line preparation and execution of movements. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neuropathology in cats experimentally infected with feline immunodeficiency virus: a morphological, immunocytochemical and morphometric study

Head flexion and extension movements near the natural head position (NHP) were analysed for the location of the mean instantaneous centre of rotation (ICR). Forty-six healthy young adults (30 women and 16 men) with sound dentitions, free from cranio-cervical disorders, performed habitual movements that were automatically detected and measured by an infrared three-dimensional motion analyser. ICR and curvature radius were calculated for each movement and subject. In both extension and flexion, ICR position changed during the motion. The movement was symmetrical in all subjects. No gender or flexion/extension differences were found for both ICR position and relevant curvature radius. On average, ICR relative to NHP soft-tissue nasion was located at about 150% of the soft-tissue nasion-right tragus distance, with an angle of about 220 degrees relative to the true horizontal. Results suggest that head flexion or extension is always performed with a combination of rotation (atlanto-occipital joint) and translation (cervical spine) even in the first degrees of motion. Moreover, NHP at rest seems to be some degree more flexed and anterior than head position during movements. These relative positions and their muscular determinants could also influence mandibular posture at rest and during functional movements.     

Spatial constraints on the voluntary control of attention across visual space.

Investigated the extent to which attention can be voluntarily allocated across the visual field during a single fixation. In Exp I, 20 undergraduates made a reaction time (RT) response to a stimulus occurring in a cued or a noncued location while maintaining a center fixation. In Exp II, 3 naive and 5 experienced undergraduates underwent a replication of Exp I and were monitored for horizontal eye movement during head restraint. Results from Exp I indicate that Ss were constrained to voluntarily attending to a single primary focus in space, and these findings were supported in Exp II. Data replicate those found by M. I. Posner et al (see record 1981-11809-001). (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Patterns of eye movements during parallel and serial visual search tasks.

In 2 experiments with a total of 24 undergraduates, eye movements were monitored while Ss performed parallel and serial search tasks. In Exp 1a, Ss searched for an "O" among "X"s (parallel condition) and for a "T" among "L"s (serial condition). In the parallel condition of Exp 1b, "Q" was the target and "O"s were distractors; in the serial condition, these stimuli switched roles. Displays contained 1, 12, or 24 stimuli, with both target-present and target-absent trials. RT and eye-movement measures (number of fixations, saccadic error, and latency to move) indicated that search efficiency was greatest in the parallel conditions, followed by the serial condition of Exp 1a and, finally, by the serial condition of Exp 1b. This suggests that eye movements are correlated with the attentional processes underlying visual search. (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)     

Spatial localization in sequential letter displays.

Conducted 2 experiments with a total of 26 undergraduates to investigate the ability to locate letters presented successively along a horizontal row. The letters were displayed for 5 msec, and the inter-letter interval varied between 0 and 200 msec. In Exp I, localization decreased as the inter-letter interval was increased to 50 msec. With further increments in inter-letter interval, performance improved. However, there was a correlation between the positions of the letters in space and in time. Exp II indicated that the recovery in spatial localization with inter-letter intervals greater than 50 msec is spurious (i.e., it does not occur if the correlation is minimized). (French summary) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The roles of typicality, instance dominance, and category dominance in verifying category membership.

Examined the relationships between category verification reaction time (RT), exemplar typicality, instance dominance, category selection time (an RT measure of category dominance), and 3 production measures of category dominance in 3 experiments with 122 Ss. The category dominance measures were obtained in Exp I for use in 2 nearly identical category verification experiments. In Exp II, the category name was presented 800 msec before the exemplar name. In Exp III, the exemplar name preceded the category name by 800 msec. Multiple regression analyses of the yes and no category verification RTs indicated that category dominance produced large and highly significant effects in all conditions, whereas instance dominance produced marginally significant and selective effects. Typicality had no effect beyond its shared effect with the dominance measures except as a possible suppressor variable. Category selection time was the best predictor, although all of the category dominance measures were better predictors than typicality or instance dominance. It is concluded that typicality may be an inappropriate independent variable for RT tasks studying the memory representation of natural-world knowledge. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Patterns of movement of totally intrinsic-minus fingers based on a study of one hundred and forty-one fingers

A detailed study of metacarpophalangeal flexion and interphalangeal extension movements of 141 fingers with complete intrinsic-muscle paralysis due to leprosy showed that long flexors and long extensors produce movement at the metacarpophalangeal and proximal interphalangeal joints simultaneously, and not successively as is generally believed. The amounts of flexion resulting from long flexor activity are almost equal at the two joints and metacarpophalangeal flexion is achieved without excessive flexion of the proximal interphalangeal joint, but this is masked by the claw-finger deformity. The movement resulting from activity of the long extensor is complex and there are three or more qualitatively different patterns of extension. Although the long extensor produces simultaneous extension at the metacarpophalangeal and proximal interphalangeal joints, the latter consistently lags behind the former so that full extension is not achieved at the proximal interphalangeal joint even when the metacarpophalangeal joint is maximally extended. The diverse patterns of extension are not related to duration of degree of clawing or to any particular finger.     

Semantic processing of non-attended visual information.

In 2 experiments, with 28 university students, reaction time (RT) to name 1 of 2 rows of letter material was measured. The reported row was always a word. In Exp I, the nonreported row contained either a word semantically related to the reported word, a nonassociated word, or a nonword. Nonwords were not used in Exp II. Attentional selectivity was varied by presenting a report cue either 250 msec prior to display onset or 250 msec after display onset. RT was faster when the report cue preceded the display, indicating that this cue induced selective attention. In both the selective and nonselective conditions, RT to name the target word was faster when the nonreported row contained a word associated with the target than when it contained a nonassociated word. However, this facilitation of RT produced by associated nonreported words was greater under the nonselective condition. While semantic information was extracted from both nonattended and attended visual material a larger semantic interaction occurred when attention was directed to both rows of a visual display. Results also indicate that the presence of nonwords influenced the strategy used to analyze a visual display. (French summary) (19 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Patterns of GFAP-immunoreactivity parallel the tonotopic axis in the developing dorsal cochlear nucleus

The gain of the H reflex attenuates during passive stepping and pedalling movements of the leg. We hypothesized that the kinematics of the movement indirectly reflect the receptor origin of this attenuation. In the first experiment, H reflexes were evoked in soleus at 26 points in the cycle of slow, passive pedalling movement of the leg and at 13 points with the leg static (the ankle was always immobilized). Maximum inhibition occurred as the leg moved through its most flexed position (P < 0.05). Inhibition observed in the static leg was also strongest at this position (P < 0.05). The increase in inhibition was gradual during flexion movement, with rapid reversal of this increase during extension. In the second experiment, the length of stretch of the vasti muscles was modelled. Variable pedal crank lengths and revolutions per minute (rpm) altered leg joint displacements and angular velocities. Equivalent rates of stretch of the vasti, achieved through different combinations of joint displacements and velocities, elicited equivalent attenuations of mean reflex magnitudes in the flexed leg. Reflex gain exponentially related to rate of stretch (R2 = 0.98 P < 0.01). The results imply that gain attenuation of this spinal sensorimotor path arises from spindle discharge in heteronymous extensor muscles of knee and/or hip, concomitant with movement.     

Effects of varying acceleration of platform translation and toes-up rotations on the pattern and magnitude of balance reactions in humans

Different movement synergies used to restore balance in response to sudden support surface displacements have been described, which include the ankle movement synergy and a number of multisegmental movement synergies. The purpose of this study was to extend the analysis of the effects of stimulus magnitude on the pattern and scaling of balance reactions to larger magnitudes of balance disturbances, and to other types of balance disturbances, in particular, forward translations (FT), backward translations (BT), and toes-up rotations (RT). In addition, we examined whether the timing and magnitude of center of body mass (CM) displacement is an invariant feature of corrective responses to varying magnitudes of balance disturbances. Thirteen healthy adults were subjected to FT, BT, and RT of varying acceleration/velocity. The balance disturbance induced by FT and BT was fundamentally different from that induced by RT. The balance requirement during FT and BT was to rapidly translate the CM forward/backward to the new position within the displaced base of support. For RT, the requirement was to minimize the backward displacement of the CM. As evidenced from the initial phase of ankle, knee, and hip angular displacements and anterior-posterior (A-P) center of foot pressure displacement, the magnitude of the balance disturbance increased with increasing platform acceleration/velocity. For FT and BT, the present findings are consistent with the view that trajectory of CM is a control variable, as the timing, peak magnitude, and time to peak CM displacement did not vary as a function of platform acceleration/velocity. However, for RT, the peak magnitude and time to peak CM displacement did increase with increasing platform acceleration/velocity. The results demonstrate that in response to FT, BT, and RT, stability was restored by distinct multisegmental movement synergies. The corrective response to FT consisted of early knee flexion then ankle dorsiflexion and hip extension. The corrective response to BT consisted of hip flexion and ankle plantar flexion. For RT early hip flexion and knee flexion was observed. All muscles recorded (tibialis anterior, soleus, gastrocnemius, hamstrings, and quadriceps) were activated within a range of 60 to 170 ms from onset of platform displacement. For FT, BT, and RT, the pattern and timing of angular displacements and muscle responses did not vary as a function of platform acceleration/velocity, while there was a significant effect of platform acceleration/velocity on the magnitude of the corrective response, that is, peak magnitude of corrective hip, knee, and ankle angular displacements and magnitude of muscle responses. The present findings indicate that multiple sources of spatial information are necessary for the selection and initiation of the appropriate corrective response to meet the requirements of the different balance tasks. The present results strongly endorse the concept of a postural control network for recovery of standing balance, as opposed to positive feedback through local segmental or long loop reflex circuits.     

Processing of information in iconic memory: Differences between nonretarded and retarded subjects.

Compared iconic memory processes of 17 undergraduates and 18 retarded Ss (primarily aged 18–28 yrs; IQ 56–77) in 4 experiments. In Exp I, a partial report paradigm was used in which 6 retarded and 6 undergraduate Ss were presented 6 pictures under 4 intervals (0–500 msec). In Exp II, using 5 Ss in each group the same procedure as in Exp I was used but letters as well as pictures were included. Results show that although overall performance for retarded Ss was poor, they did better with letters than with pictures—a reverse of the finding with undergraduate Ss. In Exp III, 2 retarded Ss were given extended practice and incentive to perform well. Asymptote was reached in 10 days but never equaled performance of unpracticed undergraduates. In Exp IV, using 5 Ss in each group, information load was varied from 1 to 4 items, and a masking stimulus was used to interrupt processing following 6 intervals that lasted up to 250 msec. Results show that (1) there are quantitative differences between intelligence groups in iconic capacity; (2) retarded Ss process information more slowly, a difference that increases with increasing information load; and (3) there are substantive structural differences in iconic memory of retarded and nonretarded Ss. (35 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Overt and covert attention and vibrotactile reaction times: Gaze direction, spatial compatibility and hemispatial asymmetry.

Performed 2 vibrotactile reaction time (RT) experiments, using 32 strongly dextral undergraduates to determine if (1) Ss attention toward/away from the operating hand effected RT and (2) there was an interaction with hand-hemispace and spatial compatibility. In Exp I, 16 Ss were administered a 250 Hz vibratory stimulus to the forefinger of a hand and were required to depress a switch as soon as the stimulus was felt. Hemispace of the stimulated hand was varied and head turns were recorded. In Exp II, 16 Ss were presented with stimuli to the left and the right hand and Ss looked at 1 hand for a block of trials. Results suggest that vibrotactile asymmetries may stem from differences in ability to hold covert attention in a number of spatial locations. It is suggested that overt and covert attention play different mediating roles in performance asymmetries, both at the hemispatial level and in classical anatomical connectivity paradigms of visual field and ear of entry. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Motor preparation and the effects of practice: Evidence from startle.

To examine sequential movement preparation, participants practiced unimanual movements that differed in amplitude and number of elements for 4 days in either a simple (Experiment 1) or choice (Experiment 2) reaction time (RT) paradigm. On Day 1 and 4, a startling stimulus was used to probe the preparation process. For simple RT, we found increased premotor RT for the two component movement during control trials on Day 1, which was minimized with practice. During startle trials, all movements were triggered at a short latency with similar consistency to control trials, suggesting full advance preparation of all movements. For choice RT, we also found increased premotor RT for control trials for the two component movement. As advance preparation could not occur, the startling stimulus did not trigger any of the movements. We hypothesized that complexity may relate to the neural commands needed to produce the movement, rather than a sequencing requirement. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Monitoring eye movements under conditions of associative matching, response production, and stimulus and response production.

Monitored eye movements in each of 3 studies with 20, 19, and 18 undergraduates, respectively, while Ss were given 8 study trials on a 7-item paired-associate list. Ss were then subjected to a single test trial of associative matching (Exp. I), response production (Exp. III) or stimulus and response production (Exp. IV). A 4th study with 42 Ss, (Exp. II), without eye movement monitoring, involved 3 groups of Ss given either 2, 4, or 6 study trials followed by a single test trial of associative matching. Results, with the exception of Exp. I, were generally consistent with a 2-stage notion of verbal paired-associate learning. (French summary) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Genotoxicity of trophosphamide in mouse germ cells: assessment of micronuclei in spermatids and chromosome aberrations in one-cell zygotes

We have used the muscle history dependence of the sensitivity of muscle spindles to stretch, to provide evidence for their contribution to kinaesthesia, the sense of position and movement. Stretch sensitivity is altered depending on whether or not slack has been introduced in intrafusal fibres [13]. At the human elbow joint detection threshold was measured to passive movements applied at different speeds to the forearm after a conditioning co-contraction of muscles of the upper arm, with the arm held either flexed ('hold short') or extended ('hold long'). Test measurements were made with the elbow joint at 90 degrees. For the three speeds of movement, 2 degrees s-1, 0.2 degree s-1 and 0.02 degree s-1, after 'hold short' conditioning thresholds were lower for movements into extension, after 'hold long' conditioning they were lower for movements into flexion. It is concluded that when muscle conditioning introduces slack in the intrafusal fibres of muscle spindles, this must be taken up by the test movements before they can be detected by the subject. It means that whenever detection thresholds to passive movements are measured at a joint, the contraction history of the muscles acting at that joint must be taken into account.     

Frequency effects in lexical decisions: A test of the verification model.

Lexical decisions about high-frequency words are faster than about low-frequency words. It has been suggested that the locus of this effect is in a verification stage in which a frequency-ordered comparison takes place that requires the continuous availability of a sensory representation of the stimulus. This proposal was tested in 4 lexical-decision experiments, using 64 undergraduates. In Exp I, high- and low-frequency words and nonword stimuli remained visible until Ss responded. The stimuli in Exp II were illuminated for only 1 retrace on a video monitor (16.7 msec), and in Exp III, the single retrace was followed by a pattern mask 50 msec later. The latter 2 conditions have been suggested as manipulations that would eliminate the verification stage of recognition. Nevertheless, the effect of word frequency on decision latencies was comparable in all 3 experiments. Data from Exp IV eliminated orthographic regularity as a factor contributing to the obtained frequency effect. It is suggested that frequency has its effects prior to verification and that the notion of verification as the sole basis for frequency effects needs to be revised. (18 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spinal cord coordination of hindlimb movements in the turtle: intralimb temporal relationships during scratching and swimming

Hindlimb interlimb coordination was examined in turtles during symmetrical "same-form" behaviors in which both hindlimbs utilized the same movement strategy ("form") and during asymmetric "mixed-form" behaviors in which the form exhibited by one hindlimb differed from that of its contralateral partner. In spinal turtles, three forms of scratching were examined: rostral, pocket, and caudal. Bilateral symmetrical same-form scratching was studied for each of the forms. Asymmetric mixed-form scratching (rostral scratching of a hindlimb and pocket scratching of the other hindlimb) was also examined. In intact turtles, two forms of swimming were examined: forward swimming and back-paddling. The symmetrical behavior of bilateral forward same-form swimming and the asymmetric behavior of turning mixed-form swimming (forward swimming of 1 hindlimb and back-paddling of the other hindlimb) were studied. For all behaviors examined, most episodes displayed absolute or 1:1 coordination; in this type of coordination, during each movement cycle that began and ended with the onset of ipsilateral hip flexion, there was a single onset of contralateral hip flexion. For most of these episodes there was out-of-phase coordination between hip movements; the onset of contralateral hip flexion occurred near the onset of ipsilateral hip extension midway through the ipsilateral movement cycle. Bilateral caudal/caudal same-form scratching displayed out-of-phase 1:1 coordination during some episodes and in-phase 1:1 coordination during other episodes. During in-phase coordination, the onset of contralateral hip flexion occurred near the onset of ipsilateral hip flexion close to the start of the ipsilateral movement cycle. In a few cases of bilateral same-form scratching there were episodes of relative or 2:1 coordination; in this type of coordination, during each movement cycle of the slowly moving limb that began and ended with ipsilateral hip flexion, there were two distinct occurrences of the onset of contralateral hip flexion. The observation that out-of-phase movements of the hip occurred during symmetrical as well as asymmetric behaviors is consistent with the hypothesis that timing signals related to hip movement play a major role in interlimb phase control. The neural mechanisms responsible for interlimb phase control are not well understood in vertebrates. The present demonstration of bilateral scratching in spinal turtles suggests that this preparation may be suitable for additional experiments to examine mechanisms of vertebrate interlimb phase control.     

Cue search and comparison processes in visual search for letters.

In 2 experiments, each with 16 college students and laboratory staff members, Ss searched 4- and 8-letter arrays for the presence of a T or an F. The position of the target was indicated by a bar marker presented at 1 of 7 stimulus onset asynchronies (SOAs): –200, –25, 50, 125, 200, 275, or 350 msec. In Exp I, SOA conditions were blocked; in Exp II, SOA conditions varied randomly from trial to trial. In both experiments array size and SOA interacted. With 8-letter arrays, reaction time (RT) increased linearly with SOA with a slope less than 1. With 4-letter arrays, RT increased with SOA but reached asymptote at the level of no-cue control RTs at the 125-msec SOA. Results support the notion that cue search and comparison processes may function concurrently. (French summary) (18 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

"Pessimistic noise effects": The perception of reaction times in noise.

Used a between-group design to examine the effect of loud noise on a 2-choice discrete reaction task and the judgments Ss made about self-produced RTs under these conditions. In Exp I, 70 Ss (aged 26–39 yrs) completed a 2-choice RT task and a concurrent RT rating task of speed. White noise was presented to Ss in the experimental groups. RTs were unexpectedly faster in noise, but Ss used more "slow" categories in describing them. The effect was not apparent when the same RTs were rerated a 2nd time under instructions that indicated that they were random time intervals. Also, the effect was not apparent when a new group of 14 undergraduates in Exp II rated the original RT data, again in noise. Exp III showed that when asked to predict average RTs produced by a hypothetical S in noise, 30 uniformed Ss (aged 26–39 yrs) predicted slow RTs. Results are considered in the light of the hypothesis that pessimistic expectancies about likely effects of noise may be a factor influencing performance. (French abstract) (12 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)