Asymmetry of Verbal-Manual Interference - Dissociation Between Rate and Variability in Left-Handers

In two experiments, 48 right-handed and 48 left-handed adults, respectively, performed speeded and consistent finger tapping with and without concurrent oral reading. Interference was measured in terms of change in tap-to-tap rate and variability. Experiment 1 confirmed a previous report that concurrent reading decreases the rate of speeded finger tapping and increases the rate of consistent tapping in right-handers, and that the right hand is affected more than the left. Experiment 2 showed that, for left-handers, concurrent reading decreases the rate of left-hand tapping more than right-hand tapping but increases the variability of the right hand more than the left. The double dissociation in left-handers between hand and dependent variable suggests that the speed and variability reflect different mechanisms of intertask interference. More generally, the findings illustrate the multidimensionality of motor performance and the risk of making inferences about neural organization on the basis of a single dependent measure.     

Effects of speaking upon the rate and variability of concurrent finger tapping in children

Tapping rate and variability were measured as 73 normal, right-handed children in Grades 1–4 engaged in speeded unimanual finger tapping with and without concurrent recitation. Speaking reduced the rate of tapping and increased its variability to a greater extent in younger children than in older children. Developmental changes in variability but not rate were attributable to a greater number of lengthy (>500 ms) pauses in the tapping of younger children. Speaking slowed the right hand more than the left, and the degree of this asymmetry was constant across grade levels. The right-hand effect for tapping rate was not attributable to lengthy pauses. In contrast, asymmetric increases in tapping variability occurred only among children in Grade 1 and only when lengthy pauses were included in the data. The results implicate three mechanisms of intertask interference: one involving capacity limitations, a second involving cross-talk between motor control mechanisms for speech and finger movement, respectively, and a third factor involving occasional diversion of attention from tapping to speaking. These mechanisms are discussed in relation to developmental changes in mental capacity.     

Lateralized interference in finger tapping: comparisons of rate and variability measures under speed and consistency tapping instructions

Forty right-handed college subjects tapped with and without a verbal task under two instructional conditions (tap as quickly as possible vs. tap as consistently as possible) and two levels of verbal production (silent vs. aloud). The tapping task consisted of the alternate tapping of two keys with the index finger of the left vs. right hands, while the verbal task was anagram solution. Three rate and four variability measures of tapping performance were evaluated in the identification of lateralized interference. The results indicate that reliable lateralized interference, more right-hand than left-hand tapping disruption, was observed only for variability measures under instructions to tap as consistently as possible. Furthermore, only one of these variability measures was sensitive to an increase in lateralized interference produced by verbal production. Because of the limited demonstration of verbal laterality effects with the two-key tapping procedure in this study, conclusions suggest that the simpler manual task of repetitive tapping of one key should be viewed as the method of choice in future dual-task studies.     

Unimanual tapping during concurrent articulation: examining the role of cortical structures in the execution of programmed movement sequences

Three experiments were conducted to examine effects of speech on concurrent unimanual tapping. Experiments 1 and 2 involved the manual tapping of a short burst of preprogrammed responses with or without concurrent articulation. Results of these experiments showed no effects of speech articulation on the concurrent execution of programmed manual movement sequences. In Experiment 3, subjects continuously tapped for 15 sec, again, with or without concurrent speech articulation. The results showed that articulation affected the speed of concurrent manual responses with larger interference for right hand tapping than for left hand tapping. Additional analysis of the tapping variability revealed equivalent effects of concurrent articulation on the timing of repetitive right and left hand tapping. Kinsbourne's Functional Cerebral Distance Principle was used to interpret these results. Within this framework, the present findings indicate that functionally distinct processes control speech articulation and the execution of programmed manual movement sequences.     

Age-related differences in concurrent-task performance of normal adults: evidence for a decline in processing resources.

A concurrent-task paradigm was used to investigate age-related differences in the attentional capacity of 92 right-handed adults. Young, middle-aged, and elderly Ss were compared as they performed speeded, unimanual finger tapping with and without concurrent silent reading, speaking, and maze completion. There were 2 levels of difficulty for each cognitive task. The decrement in tapping rate from the single- to dual-task condition increased linearly with age. Concurrent-task tapping was slowed more by difficult than by easy tasks, and difficult tasks had a disproportionately disruptive effect on the concurrent performance of elderly Ss. The heightened vulnerability of the elderly to concurrent-task effects cannot be attributed parsimoniously to either general slowing or diminution of a specific resource. Instead the results suggest a reduction in a general-purpose processing resource with increasing age.     

Dual task performance in children: generalized and lateralized effects of memory encoding upon the rate and variability of concurrent finger tapping

Interference between concurrent tasks was used to investigate the brain basis of capacity limitations apparent when children encode information. Seventy-three right-handed children in Grades 1-4 engaged in speeded unilateral finger tapping while encoding a variable number of faces or numbers for subsequent recognition testing. With both face and number encoding, tapping rate decreased as memory load increased. Encoding numbers was more disruptive than encoding faces. Both encoding tasks slowed right-hand tapping more than left-hand tapping, relative to control tapping performance, but had only a bilateral effect on the variability of tapping. Although overall interference was less than that observed with a comparison task (i.e., speaking), the asymmetry of interference was comparable. The results suggest that cerebral lateralization for memory encoding, as well as for speech, is constant across the age range of 6-10 years. Findings regarding developmental change in overall capacity, however, are task specific: interference from speaking but not from memory encoding decreases with increasing age.     

Reliability of verbal-manual interference

Considerable recent research has used unimanual finger tapping with concurrent vocalization to assess hemispheric lateralization for language. This study examined whether an index finger tapping task is a reliable measure in adults and whether the task demonstrates sex differences in hemispheric specialization for language. Thirty right-handed subjects, fifteen male and fifteen female, between the ages of 18 and 25 were tested. The task measured the differences in tapping rate for each hand between tapping with and without a concurrent verbal task. The task was completed once each day for 3 consecutive days to determine reliability. The tapping task was found to be a reliable measure. No significant differences were found between tapping scores of males and females.     

Impulsivity and paced tapping

The purpose of this study was to test the hypothesis that impulsivity is positively related to both the intraindividual variability and the rate of performance of a paced tapping task. The independent variable in the tapping task were: feedback vs. no feedback; tempo; concurrent cognitive task (counting) vs. no concurrent cognitive task. Three measures of tapping performance were computed: absolute or total error of tapping, tapping rate, and the intraindividual variability of tapping. The results confirm the hypothesis that impulsivity is positively related to rate of paced tapping, although the degree of relationship varied under different experimental conditions within the paced tapping task. Intraindividual variability of tapping was not significantly related to impulsivity, but the results were suggestive of a positive relationship.     

Impulsivity and Paced Tapping

The purpose of this study was to test the hypothesis that impulsivity is positively related to both the intraindividual variability and the rate of performance of a paced tapping task. Selected experimental conditions which have been demonstrated to influence paced tapping were included in the experimental design of the tapping task. The independent variables in the tapping task were: feedback vs. no feedback; tempo; concurrent cognitive task (counting) vs. no concurrent cognitive task. Three measures of tapping performance were computed: absolute or total error of tapping, tapping rate, and the intraindividual variability of tapping. The results confirm the hypothesis that impulsivity is positively related to rate of paced tapping, although the degree of relationship varied under different experimental conditions within the paced tapping task. Intraindividual variability of tapping was not significantly related to impulsivity, but the results were suggestive of a positive relationship.     

Variability in the timing of responses during repetitive tapping with alternate hands

Summary This paper addresses the question of whether a simple two-stage account of variability in timing developed for single-hand repetitive tapping is applicable to regular tapping with the hands in alternation. The task required key presses at a steady rate, previously set by a periodic auditory signal. On separate blocks of trials four subjects used the index finger of the left hand or of the right hand at intervals of 200, 400, and 800 ms or alternated between the hands at intervals of 100, 200, or 400 ms. For each subject the variability of the between-hand intervals in the 200- and 400-ms alternate-hand conditions was greater than the variability of the same interval in the single-hand conditions. In the 100-ms alternate-hand condition correlations between adjacent (between-hand) intervals were reliably less then –.5. These results are inconsistent with the simple two-stage model, and two variants are shown to provide a better qualitative fit to at least some aspects of the data.     

The coupled oscillator model of between-hand coordination in alternate-hand tapping: a reappraisal

Single and alternating hand tapping were compared to test the hypothesis that coordination during rhythmic movements is mediated by the control of specific time intervals. In Experiment 1, an auditory metronome was used to indicate a set of timing patterns in which a 1-s interval was divided into 2 subintervals. Performance, measured in terms of the deviation from the target patterns and variability, was similar under conditions in which the finger taps were made with 1 hand or alternated between the 2 hands. In Experiment 2, the modality of the metronome (auditory or visual) was found to influence the manner in which the produced intervals deviated from the target patterns. These results challenge the notion that bimanual coordination emerges from coupling constraints intrinsic to the 2-hand system. They are in accord with a framework that emphasizes the control of specific time intervals to form a series of well-defined motor events.     

The contribution of tactile reafference to temporal regularity during bimanual finger tapping

In a repetitive tapping task, the within-hand variability of intertap intervals is reduced when participants tap with both hands, as opposed to single-handed tapping. This bimanual advantage can be attributed to timer variance (according to the Wing-Kristofferson model). Separate timers have been proposed for each hand whose outputs are then averaged (Helmuth & Ivry, 1996, Journal of Experimental Psychology: Human Perception and Performance, 22, 278-293). Alternatively, timing might be based on sensory reafference and the bimanual advantage due to the enhancement of sensory reafferences. This alternative hypothesis was tested in three experiments. In the first experiment, we replicated the bimanual advantage in tapping with two fingers of the same hand compared with single finger tapping. In the second experiment, we demonstrated that the bimanual advantage decreased when tactile reafferences from left-hand taps were omitted (by contact-free tapping). In the third experiment, participants tapped bimanually with the index fingers of both hands firmly mechanically coupled. The bimanual advantage was replicated for this condition. Results are consistent with the assumption that the bimanual advantage is due to the sensory reafferences of the second hand. We suggest that our results are best explained by a reformulation of the Wing-Kristofferson model, in which the timer provides action goals in terms of sensory reafferences.     

Weber (slope) analyses of timing variability in tapping and drawing tasks

Timing variability in continuous drawing tasks has not been found to be correlated with timing variability in repetitive finger tapping in recent studies (S. D. Robertson et al., 1999; H. N. Zelaznik, R. M. C. Spencer, & R. B. Ivry, 2002). Furthermore, the central component of timing variability, as measured by the slope of the timing variance versus the square of the timed interval, differed for tapping and drawing tasks. On the basis of those results, the authors posited that timing in tapping is explicit and as such uses a central representation of the interval to be timed, whereas timing in drawing tasks is implicit, that is, the temporal component is an emergent property of the trajectory produced. The authors examined that hypothesis in the present study by determining the linear relationship between timing variance and squared duration for tapping, circle-drawing, and line-drawing tasks. Participants (N = 50) performed 1 of 5 tasks: finger tapping, line drawing in the x dimension, line drawing in the y dimension, continuous circle drawing timed in the x dimension, or continuous circle drawing timed in the y dimension. The slopes differed significantly between finger tapping, line drawing, and circle drawing, suggesting separable sources of timing variability. The slopes of the 2 circle-drawing tasks did not differ from one another, nor did the slopes of the 2 line-drawing tasks differ significantly, suggesting a shared timing process within those tasks. Those results are evidence of a high degree of specificity in timing processes.     

Temporal Regularity of Tapping by the Left and Right Hands in Timed and Untimed Finger Tapping

The temporal characteristics of repetitive finger tapping by the left and right hands were examined in two experiments. In the first experiment, interresponse intervals (IRIs) were recorded while right-handed male subjects tapped in synchrony with an auditory timing pulse (the synchronization phase) and then attempted to maintain the same tapping rate without the timing pulses (the continuation phase). The left and right hands performed separately, at four different rates (interpulse intervals of 250, 500, 750, and 1500 ms). There was no asymmetry of the asynchronies of the timing pulses and the associated responses in the synchronization phase or of the IRIs in either phase, but there was an asymmetry in the temporal dispersion of the responses in both phases. In the second experiment, right-handed males tapped separately with each hand at three different speeds: as quickly as possible, at a fast but steady rate, and at a slow rhythmical rate. The speed asymmetry present when tapping as quickly as possible (with the preferred hand tapping more quickly) was reduced when tapping at the fast steady rate and was absent when tapping at the slow rhythmical rate. The temporal dispersion of the IRIs produced by the nonpreferred hand was greater than the temporal dispersion of those produced by the preferred hand in all speed conditions. These results show smaller temporal dispersion of tapping by the preferred hand in right-handed males under different conditions, including submaximal speeds at which both hands respond at the same rate. This suggests that the motor system controlling the preferred hand in right-handers has more precise timing of response output than that controlling the nonpreferred hand.     

Weber (Slope) Analyses of Timing Variability in Tapping and Drawing Tasks

Timing variability in continuous drawing tasks has not been found to be correlated with timing variability in repetitive finger tapping in recent studies (S. D. Robertson et al., 1999; H. N. Zelaznik, R. M. C. Spencer, & R. B. Ivry, 2002). Furthermore, the central component of timing variability, as measured by the slope of the timing variance versus the square of the timed interval, differed for tapping and drawing tasks. On the basis of those results, the authors posited that timing in tapping is explicit and as such uses a central representation of the interval to be timed, whereas timing in drawing tasks is implicit, that is, the temporal component is an emergent property of the trajectory produced. The authors examined that hypothesis in the present study by determining the linear relationship between timing variance and squared duration for tapping, circle-drawing, and line-drawing tasks. Participants (N = 501 performed 1 of 5 tasks: finger tapping, line drawing in the x dimension, line drawing in the y dimension, continuous circle drawing timed in the x dimension, or continuous circle drawing timed in the y dimension. The slopes differed significantly between finger tapping, line drawing, and circle drawing, suggesting separable sources of timing variability. The slopes of the 2 circle-drawing tasks did not differ from one another, nor did the slopes of the 2 line-drawing tasks differ significantly, suggesting a shared timing process within those tasks. Those results are evidence of a high degree of specificity in timing processes.     

Concurrent verbal interference of right and left proximal and distal upper extremity tapping

The purpose of this study was to investigate crossed and uncrossed control of the proximal (upper arm and shoulder) and distal (lower arm and hand) musculature of the arms using the dual-task paradigm. Forty-one strongly right-handed men performed a tapping task using primarily the musculature of the upper or lower arms, with and without concurrent verbal processing demands. The results showed that the left distal region was distinguished from the other three effector locations by its relative insensitivity to the demands of the dual-task (verbal processing) condition. Rapid alternating movements of the left arm were functionally independent from the left index finger location in response to dual-task demands. Dual verbal and tapping demands at this effector produced greater interference on both the primary and secondary task. The results preclude the attribution of interference effects to manual dominance factors alone. The results generally support anatomical accounts of increased ipsilateral control over left side arm but not hand movements. Neither the traditional cognitive hemispheric model nor the manual dominance hypothesis were adequate in accounting for the results. An alternative generalized capacity hypothesis was required to account for performance at the LE.     

Anatomically ordered tapping interferes more with one-digit addition than two-digit addition: a dual-task fMRI study

Fingers are used as canonical representations for numbers across cultures. In previous imaging studies, it was shown that arithmetic processing activates neural resources that are known to participate in finger movements. Additionally, in one dual-task study, it was shown that anatomically ordered finger tapping disrupts addition and subtraction more than multiplication, possibly due to a long-lasting effect of early finger counting experiences on the neural correlates and organization of addition and subtraction processes. How arithmetic task difficulty and tapping complexity affect the concurrent performance is still unclear. If early finger counting experiences have bearing on the neural correlates of arithmetic in adults, then one would expect anatomically and non-anatomically ordered tapping to have different interference effects, given that finger counting is usually anatomically ordered. To unravel these issues, we studied how (1) arithmetic task difficulty and (2) the complexity of the finger tapping sequence (anatomical vs. non-anatomical ordering) affect concurrent performance and use of key neural circuits using a mixed block/event-related dual-task fMRI design with adult participants. The results suggest that complexity of the tapping sequence modulates interference on addition, and that one-digit addition (fact retrieval), compared to two-digit addition (calculation), is more affected from anatomically ordered tapping. The region-of-interest analysis showed higher left angular gyrus BOLD response for one-digit compared to two-digit addition, and in no-tapping conditions than dual tapping conditions. The results support a specific association between addition fact retrieval and anatomically ordered finger movements in adults, possibly due to finger counting strategies that deploy anatomically ordered finger movements early in the development.     

Temporal regularity of tapping by the left and right hands in timed and untimed finger tapping

The temporal characteristics of repetitive finger tapping by the left and right hands were examined in two experiments. In the first experiment, interresponse intervals (IRIs) were recorded while right-handed male subjects tapped in synchrony with an auditory timing pulse (the synchronization phase) and then attempted to maintain the same tapping rate without the timing pulses (the continuation phase). The left and right hands performed separately, at four different rates (interpulse intervals of 250, 500, 750, and 1500 ms). There was no asymmetry of the asynchronies of the timing pulses and the associated responses in the synchronization phase or of the IRIs in either phase, but there was an asymmetry of chronization phase or of the IRIs in either phase, but there was an asymmetry in the temporal dispersion of the responses in both phases. in the second experiment, right-handed males tapped separately with each hand at three different speeds: as quickly as possible, at a fast but steady rate, and at a slow rhythmical rate. The speed asymmetry present when tapping as quickly as possible (with the preferred hand tapping more quickly ) was reduced when tapping at the fast steady rate and was absent when tapping at the slow rhythmical rate. The temporal dispersion of the IRIs produced by the nonpreferred hand was greater than the temporal dispersion of those produced by the preferred hand in all speed conditions. These results show smaller temporal dispersion of tapping by the preferred hand in right-handed males under different conditions, including submaximal speeds at which both hands respond at the same rate. This suggests that the motor system controlling the preferred hand in right-handers had more precise timing of response output than that controlling the nonpreferred hand.     

Timing dysfunctions in schizophrenia as measured by a repetitive finger tapping task

Schizophrenia may be associated with a fundamental disturbance in the temporal coordination of information processing in the brain, leading to classic symptoms of schizophrenia such as thought disorder and disorganized and contextually inappropriate behavior. Although a variety of behavioral studies have provided strong evidence for perceptual timing deficits in schizophrenia, no study to date has directly examined overt temporal performance in schizophrenia using a task that differentially engages perceptual and motor-based timing processes. The present study aimed to isolate perceptual and motor-based temporal performance in individuals diagnosed with schizophrenia using a repetitive finger-tapping task that has previously been shown to differentially engage brain regions associated with perceptual and motor-related timing behavior. Thirty-two individuals with schizophrenia and 31 non-psychiatric control participants completed the repetitive finger-tapping task, which required participants to first tap in time with computer-generated tones separated by a fixed intertone interval (tone-paced tapping), after which the tones were discontinued and participants were required to continue tapping at the established pace (self-paced tapping). Participants with schizophrenia displayed significantly faster tapping rates for both tone- and self-paced portions of the task compared to the non-psychiatric group. Individuals diagnosed with schizophrenia also displayed greater tapping variability during both tone- and self-paced portions of the task. The application of a mathematical timing model further indicated that group differences were primarily attributable to increased timing – as opposed to task implementation – difficulties in the schizophrenia group, which is noteworthy given the broad range of impairments typically associated with the disorder. These findings support the contention that schizophrenia is associated with a broad range of timing difficulties, including those associated with time perception as well as time production.     

Timing dysfunctions in schizophrenia as measured by a repetitive finger tapping task

Schizophrenia may be associated with a fundamental disturbance in the temporal coordination of information processing in the brain, leading to classic symptoms of schizophrenia such as thought disorder and disorganized and contextually inappropriate behavior. Although a variety of behavioral studies have provided strong evidence for perceptual timing deficits in schizophrenia, no study to date has directly examined overt temporal performance in schizophrenia using a task that differentially engages perceptual and motor-based timing processes. The present study aimed to isolate perceptual and motor-based temporal performance in individuals diagnosed with schizophrenia using a repetitive finger-tapping task that has previously been shown to differentially engage brain regions associated with perceptual and motor-related timing behavior. Thirty-two individuals with schizophrenia and 31 non-psychiatric control participants completed the repetitive finger-tapping task, which required participants to first tap in time with computer-generated tones separated by a fixed intertone interval (tone-paced tapping), after which the tones were discontinued and participants were required to continue tapping at the established pace (self-paced tapping). Participants with schizophrenia displayed significantly faster tapping rates for both tone- and self-paced portions of the task compared to the non-psychiatric group. Individuals diagnosed with schizophrenia also displayed greater tapping variability during both tone- and self-paced portions of the task. The application of a mathematical timing model further indicated that group differences were primarily attributable to increased timing – as opposed to task implementation – difficulties in the schizophrenia group, which is noteworthy given the broad range of impairments typically associated with the disorder. These findings support the contention that schizophrenia is associated with a broad range of timing difficulties, including those associated with time perception as well as time production.