The Effects of dual task ( fine motor precision + cognitive charge ) on proprioception

The aim of the given preliminary study was to check whether any changes in Þ ne motor behaviour exist in switching from single to double task (with cognition charge) in proprioceptive sensory graphomotor test conditions. Ten students (Þ ve males and Þ ve females), aged from 20 to 30 years old, took part in the experiment precision of tracking of the models in both experimental test conditions: without and with cognitive task (counting numbers back). The variables for assessment were obtained with use of the digitalized proprioceptive diagnostics (Tous, 2008; Tous, J.M., Muiños, Tous, O., & Tous J, 2012) of Mira y Lopez laboratory (University of Barcelona) that transformed the measurements of drawn lines on a touch screen from pixels into millimetres. As results showed, in the proprioceptive test condition, the changes in deviations related to spatial (lineograms) or line length variability (parallels) did not reach any statistical signiÞ cance; while the changes in line length performance (lineograms) were found signiÞ cant (that corresponds to inhibition-excitatory balance of nervous system).

The importance to perform the motor tasks (as well as maintain balance) in an automatic manner has a crucial effect in having more attentional resources for the cognitive tasks (Baltes, & Lindenberger, 1997).The automaticity of performance is highly related to the proprioception that contributes to acquire new skills or to gain the professional experience after multiple repetitions (Liutsko, 2013).The Ingram's study showed that a person with proprioceptive deÞ cit performed the motor task 60% less accurately when the cognitive charge was added, whereas the control group decreased their performance in only 10% (Ingram, van Donkelaar, Vercher, Gauthier, & Miall, 2000).
As per the bibliographical revision of the research concerned with the dual--task paradigm, it is more evident to expect greater difference related to age, trauma, pathology or speciÞ c diseases (that alter motor control or proprioception).However, we were interested to test the "baseline" or normal conditions and to see what is happening on this level, where such differences were expected to be minimal.Thus, the aim of the study was to check whether there exist any changes in Þ ne motor behaviour comparing single and dual task (with cognition charge) performance in proprioceptive sensory graphomotor test conditions, since young adults have their proprioceptive state better compared to the adolescents or older population (Liutsko, Muiños, & Tous, 2014).Our hypothesis was to conÞ rm that there would be no or little differences in dual task performance (Þ ne motor precision + counting numbers back) compared to the single one (Þ ne motor precision only) in the proprioceptive test condition in young adult participants (students).From another side it was an exploratory study whose purpose was to observe the tendencies in any changes that occur in the proprioceptive graphical feedback in dual task condition vs. single.

Methods
The Proprioceptive Diagnostics of Temperament and Character (Tous, 2008;Tous et al., 2012;Liutsko, 2012) is a computerized graphomotor test created within tradition of Mira y Lopez' myokinetical psychodiagnosis (Mira, 1958) in the Laboratory of Mira y Lopez of the University of Barcelona.

Participants
Ten students of the faculty of psychology (Þ ve men and Þ ve women; age range: 20-30 years old) participated in this preliminary study.All the students were self--reported to be right-handers.

Instruments
The test can be realized with help of specially designed program (Tous, 2008) installed on PC and connected to a touch screen (LGE with resolution 1280x1024 and optimal frequency of 60 Hz) (Figure 1).A stool, adjustable to the participant's height is also required together with table and stylus for drawing on a touch screen.

Procedure
The main stimuli for representation are of two types: 1) lineograms (lines of 40 mm length) and 2) parallels (50 mm length with 8 mm of distance between them) (Figure 2).The participant should reproduce the stimuli as per indicated instructions Þ rst with visual guidance and without it (proper proprioceptive sensory test condition) by both hands.As per lineograms, they were represented in three movement types: transversal, sagittal and frontal; as per parallels, they were performed in the ascendant and descendent order.The more detailed description of method is provided in its manual (Tous et al., 2012), for lineogramms you can see also (Tous, Muiños, Liutsko & Forero, 2012).The speciÞ c instructions for this study was to perform the proprioceptive test (PD) -trace the lineograms or to draw the parallel lines (Figure 2) twice: 1) in the single condition task the instruction as in usual use of PD -to trace o draw lines as precisely as it is possible; 2) in the dual condition task the participants should perform it together with a cognitive task (counting numbers back starting from 100).There was a Þ ve minute pause between both performances.

Data
The following observable variables are obtained by the Proprioceptive Diagnostics of Temperament and Character (Tous, Viadé, & Muiños, 2007;Tous et al., 2012;Liutsko, & Tous-Ral, 2012): 1) Spatial deviations (lineograms): a) DP1 and DP2 -directional or primary biases (shifts performed parallel to the model) in the frontal movement type, DP3 and DP4 -directional biases in the transversal movement type, DP5 and DP6 -directional biases in the sagittal movement type; b) DS1 and DS2 -formal or secundary biases (shifts performed perpendiculary to the model) in the frontal movement.2) Line length (lineograms): LL1 and LL2 -an average line length in all three movement types.3) Line length variability (parallels): LV1 and LV2 -show the difference between the longest and shortest line length in the proprioceptive part of test.All even numbers in indexing of variables correspond to measurements in non-dominant hand that represents more temperamental (less adaptive qualities) and all odd numbers to those performed by dominant hand.

Results
Data analysis was performed with the programme SPSS v. 19.The descriptive statistics of means and standard deviations of Þ ne motor precision in single and dual task is performed in Table 1 together with Z-values and signiÞ cance level for the non-parametric differences paired analysis (sign test of Wilcoxon).
Tab. 1. Descriptive statistics and Wilcoxon sing test results for the difference in the performances between single and dual tasks.Analysing the changes in Þ ne motor precision that occurred in the dual task compared to the single one, there are some points to mention.First of all, the shift upward of the group mean value in the directional bias, frontal movement and non-dominant hand performance (DP1) (-10.20±23.47mm vs. -1.20±29.92mm) corresponds to a tendency to be more optimistic in the Mood dimension.Here-with, in the dominant hand (DP2) these changes were unnoticeable (-14.00±11.92mm vs. -14.30±12.98mm).However, these differences did not reach a statistically signiÞ cant level (Table 1).
As far as the directional bias in the transversal movement type, the left-side shift was performed in both hands; slightly more in non-dominant hand (DP3) (1.00±11.61mm vs. -10.00±11.79mm) indicating that Attention style had a tendency to be more internalised (more Intratension compared to the single task performance).Nevertheless, this difference also did not reach a statistically signiÞcant level (Z=-1.785,p=0.074) (Table 1).
The changes performed in the directional bias in sagittal movement (DP5 & DP6), in formal bias (DS1 & DS2) and in live length variability (LV1 & LV2) were not signiÞ cant (Table 1).The only difference in the proprioceptive Þ ne motor performance, that also reached statistically signiÞ cant level, was line length performance in both hands (LL1 and LL2), indicating the shift in the Inhibition-Excitability balance towards the excitability.Thus, the line length had a mean value of 41.70±14.34mm in the non-dominant hand (LL1) and of 37.70±11.42mm for the dominant one (LL2), which was close to the model size of 40 mm in the single task; whereas these values were of 50.00±11.14mm and 44.50±12.39mm correspondently (Table 1).
To sum up, in the proprioceptive test condition, the changes in deviations related to spatial (lineograms) or line length variability (parallels) did not reach any statistical signiÞ cance; whereas the changes in line length performance (lineograms) were found signiÞ cant (that corresponds to inhibition-excitatory balance of nervous system).

Discussion
Although this study has a limitation of a small sample size, nevertheless, the results showed that in case of multiple tasks (dual in this case) create changes in the proprioceptive precision feedback.A conclusion derived from this study suggests that additional cognitive load affects the Þ ne motor precision in dual task performance by increasing the line length (causing more excitability) in young age participants.Moreover the tendency toward internalization of attention while performing a dual task was also seen (shift in the transversal movement in non--dominant hand), thought it did not reach a statistically signiÞ cant level.
This exploratory study suggests that the cognitive charge in the condition of dual task had effects more signiÞ cant effects in line length performance, resulting in greater representation of line length (higher excitability).This higher excitability was also observed in other studies in the performance of participants of younger ages (12-17 years) and older (more than 60 years old) (Liutsko et al, 2014).Moreover the proprioceptive bias in line length was found to have a negative correlation with visual memory tested by ROCF (Liutsko, Tous, & Muiños, 2012) that could suggest that a dual task can have negative repercussions on working visual memory too.This information should be taken into account in the educational processes, as well as, in other practices that can be dangerous, such as driving, for example.
All measurements are given in .Line lengths are given in absolute values that should be compared to the model line of 40 .The signiÞ cant differences are bolded.Source: Experimental research performed by authors in the Laboratory of Mira y López Notes: