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Reaching for words and nonwords: interactive effects of word frequency and stimulus quality on the characteristics of reaching movements.

ABSTRACT: Word frequency and stimulus degradation produce large and additive effects in the onset latencies of lexical decision responses. The influence of these two variables was examined in a lexical decision task where continuous arm-reaching responses were required and movement trajectories were tracked. The results yielded the typical additive pattern of word frequency and stimulus degradation on reaction time and movement duration. Importantly, however, an examination of movement trajectories revealed interactive effects of word frequency and stimulus degradation that emerged for the early part of the movement. These findings suggest that factors thought to influence early stages of stimulus identification continue to influence the dynamics of the response after response initiation, motivating a need to reevaluate current models of lexical decision performance. Moreover, this work highlights how the dynamics of naturalistic multidimensional responses provide a richer source of information about decision-making processes than do discrete unidimensional measures.

SUBMITTER: Bangert AS

PROVIDER: S-EPMC3685575 | biostudies-literature | 2012 Jun

REPOSITORIES: biostudies-literature

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Reaching for words and nonwords: interactive effects of word frequency and stimulus quality on the characteristics of reaching movements.

Bangert Ashley S AS Abrams Richard A RA Balota David A DA

Psychonomic bulletin & review 20120601 3

Word frequency and stimulus degradation produce large and additive effects in the onset latencies of lexical decision responses. The influence of these two variables was examined in a lexical decision task where continuous arm-reaching responses were required and movement trajectories were tracked. The results yielded the typical additive pattern of word frequency and stimulus degradation on reaction time and movement duration. Importantly, however, an examination of movement trajectories reveal ...[more]

PMID: 22419404

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Project description:BackgroundGoal-directed reaching for real-world objects by humans is enabled through visual depth cues. In virtual environments, the number and quality of available visual depth cues is limited, which may affect reaching performance and quality of reaching movements.MethodsWe assessed three-dimensional reaching movements in five experimental groups each with ten healthy volunteers. Three groups used a two-dimensional computer screen and two groups used a head-mounted display. The first screen group received the typically recreated visual depth cues, such as aerial and linear perspective, occlusion, shadows, and texture gradients. The second screen group received an abstract minimal rendering lacking those. The third screen group received the cues of the first screen group and absolute depth cues enabled by retinal image size of a known object, which realized with visual renderings of the handheld device and a ghost handheld at the target location. The two head-mounted display groups received the same virtually recreated visual depth cues as the second or the third screen group respectively. Additionally, they could rely on stereopsis and motion parallax due to head-movements.Results and conclusionAll groups using the screen performed significantly worse than both groups using the head-mounted display in terms of completion time normalized by the straight-line distance to the target. Both groups using the head-mounted display achieved the optimal minimum in number of speed peaks and in hand path ratio, indicating that our subjects performed natural movements when using a head-mounted display. Virtually recreated visual depth cues had a minor impact on reaching performance. Only the screen group with rendered handhelds could outperform the other screen groups. Thus, if reaching performance in virtual environments is in the main scope of a study, we suggest applying a head-mounted display. Otherwise, when two-dimensional screens are used, achievable performance is likely limited by the reduced depth perception and not just by subjects' motor skills.

Project description:Implanted vagus nerve stimulation (VNS) delivered concurrently with upper limb rehabilitation has been shown to improve arm function after stroke. Transcutaneous auricular VNS (taVNS) offers a non-invasive alternative to implanted VNS and may provide similar therapeutic benefit. There is much discussion about the optimal approach for combining VNS and physical therapy, as such we sought to determine whether taVNS administered during robotic training, specifically delivered during the premotor planning stage for arm extension movements, would confer additional motor improvement in patients with chronic stroke. Thirty-six patients with chronic, moderate-severe upper limb hemiparesis (>6 months; mean Upper Extremity Fugl-Meyer score = 25 ± 2, range 13-48), were randomized to receive 9 sessions (1 h in length, 3x/week for 3 weeks) of active (N = 18) or sham (N = 18) taVNS (500 ms bursts, frequency 30 Hz, pulse width 0.3 ms, max intensity 5 mA, ∼250 stimulated movements per session) delivered during robotic training. taVNS was triggered by the onset of a visual cue prior to center-out arm extension movements. Clinical assessments and surface electromyography (sEMG) measures of the biceps and triceps brachii were collected during separate test sessions. Significant motor improvements were measured for both the active and sham taVNS groups, and these improvements were robust at 3 month follow-up. Compared to the sham group, the active taVNS group showed a significant reduction in spasticity of the wrist and hand at discharge (Modified Tardieu Scale; taVNS = -8.94% vs. sham = + 2.97%, p < 0.05). The EMG results also demonstrated significantly increased variance for the bicep peak sEMG amplitude during extension for the active taVNS group compared to the sham group at discharge (active = 26.29% MVC ± 3.89, sham = 10.63% MVC ± 3.10, mean absolute change admission to discharge, p < 0.01), and at 3-month follow-up, the bicep peak sEMG amplitude was significantly reduced in the active taVNS group (P < 0.05). Thus, robot training improved the motor capacity of both groups, and taVNS, decreased spasticity. taVNS administered during premotor planning of movement may play a role in improving coordinated activation of the agonist-antagonist upper arm muscle groups by mitigating spasticity and increasing motor control following stroke. Clinical Trial Registration: www.ClinicalTrials.gov, identifier (NCT03592745).

Dataset Information

Reaching for words and nonwords: interactive effects of word frequency and stimulus quality on the characteristics of reaching movements.

Publications

Reaching for words and nonwords: interactive effects of word frequency and stimulus quality on the characteristics of reaching movements.

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