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Mental Rotation Performance in ChildrenWith Hydrocephalus Both With andWithout Spina BifidaJennifer Lehmann a & Petra Jansen aa Institute of Sport Science, University of Regensburg , Regensburg ,GermanyPublished online: 18 Oct 2013.

To cite this article: Jennifer Lehmann & Petra Jansen (2013) Mental Rotation Performance in ChildrenWith Hydrocephalus Both With and Without Spina Bifida, Developmental Neuropsychology, 38:7,433-444, DOI: 10.1080/87565641.2013.820304

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DEVELOPMENTAL NEUROPSYCHOLOGY, 38(7), 433–444Copyright © 2013 Taylor & Francis Group, LLCISSN: 8756-5641 print / 1532-6942 onlineDOI: 10.1080/87565641.2013.820304

Mental Rotation Performance in Children WithHydrocephalus Both With and Without Spina Bifida

Jennifer Lehmann and Petra JansenInstitute of Sport Science, University of Regensburg, Regensburg, Germany

The mental rotation ability in children with hydrocephalus and those with both hydrocephalus andspina bifida in comparison to healthy controls was investigated in this study. All groups performeda chronometric mental rotation test. Compared to children with hydrocephalus, children with bothspina bifida and hydrocephalus showed an impaired mental rotation performance, demonstrated byslower reaction times. No significant performance difference was found between children with spinabifida and healthy controls. Error rates were comparable between groups indicating that the impairedmental rotation performance in children with both spina bifida and hydrocephalus is primarily due tomotor impairment.

The main goal of this study was to investigate the mental rotation performance, the ability toimagine if two objects are the same when they are rotated away from in each other (Shepard &Metzler, 1971), in children with either hydrocephalus or spina bifida and hydrocephalus in com-parison to healthy controls. It is well known that children with spina bifida and hydrocephalussuffer from an impaired mental rotation performance (Jansen-Osmann, Wiedenbauer, & Heil,2008), but no evidence exists to indicate if this is due to motor impairments or cognitive impair-ments that are associated with spina bifida or the often occurring hydrocephalus. If it is shownthat the mental rotation impairment in children with spina bifida could be attributed to the motorimpairment, specific motor training could enhance this aspect of visual–spatial intelligence inchildren with spina bifida.

Spina bifida is a congenital defect in which the neural tube fails to close early in embryoge-nesis. The prevalence reported for Europe is one per 1,000 births (Masuhr & Neumann, 2007).The malformation can occur at any point along the spine and impairment varies according to thelocalization and severity of the defect. Often this disease can have effects on ambulation, bladderand bowel control, or fine motor functions. Of the patients with spina bifida, 80–90% develophydrocephalus, an obstruction of the flow of cerebrospinal fluid, which is associated with anArnold-Chiari malformation of the cerebellum and the hindbrain. The etiology of hydrocephalusis widespread but a general characterization of the condition is considered to be an increase inintracranial pressure caused by an increase of cerebrospinal fluid volume due to either insufficientreabsorption or defective drainage of cerebrospinal fluid (Masuhr & Neumann, 2007).

Correspondence should be addressed to Jennifer Lehmann, Institute of Sport Science, University of Regensburg,Universitaetsstrasse 31, 93053 Regensburg, Germany. E-mail: jennifer.lehmann@ur.de

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The cognitive abilities of children with hydrocephalus both with and without spina bifidahave already been a subject of research. In most of the children the IQs range between nor-mal and that of a child with a slight learning disability. Investigations using the Intelligence andDevelopmental Test WISC (Wechsler-Intelligence Scale for Children) showed intelligence val-ues ranging from 80–92 (Casari & Fantino, 1998; Jacobs, Northam, & Anderson, 2001; Shaffer,Friedrich, Shurtleff, & Wolf, 1985). In addition, studies have shown that children with bothspina bifida and hydrocephalus (SBHC) and children with hydrocephalus only (HC) have bet-ter verbal IQ scores than performance IQ scores (Brookshire, Fletcher, Bohan, & Landry, 1995;Jacobs et al., 2001; Lindquist, Carlsson, Persson, & Uvebrant, 2005; Wills, Holmbeck, Dillon, &McLone, 1990). The poor performance IQ has been investigated in more detail concerning thevisual–spatial performance. For example, Mammarella, Cornoldi, and Donadello (2003) inves-tigated the visuospatial working memory in SBHC children compared to a group of healthychildren matched by age. They showed that the SBHC children have greater difficulties in visualdiscrimination and visual processing than the children of the control group. Additionally, Dennis,Fletcher, Rogers, Hetherington, and Francis (2002) documented that for SBHC children, thedeficits in visual perception are more present in action-based than in object-based visual per-ception tasks. Jansen-Osmann and colleagues (2008) examined children with spina bifida, all butone child had a shunt-treated hydrocephalus, regarding their classical visuospatial abilities (per-ception, mental rotation, spatial visualization, and spatial working memory) in relation to theirmotor abilities. They discovered that children with spina bifida performed worse in all measuredspatial tasks compared to healthy controls. Additionally, they found correlations between the ageof walking and visuospatial memory, the Children’s Embedded Figures Test, and performancein a maze for children with spina bifida, indicating that there seems to be a relationship betweenmotor development and performance on spatial tasks. Wiedenbauer and Jansen-Osmann (2007)revealed a positive effect of manual rotation training on mental rotation ability in children withspina bifida. While the children with spina bifida showed slower reaction times, higher errorrates, and lower speeds of mental rotation at the beginning of the study compared to a healthycontrol group, this difference diminished after the manual rotation training. In the posttest thetwo groups demonstrated no difference in the speed of mental rotation, indicating that childrenwith spina bifida benefited considerably from the manual rotation training. Further evidence forthe relationship between locomotion and cognitive skills in children with spina bifida is givenby the study of Rendeli et al. (2002): ambulatory children had a significantly better performanceIQ compared to non-ambulatory children. Here, all children with spina bifida had shunt-treatedhydrocephalus.

In the studies mentioned above spina bifida was almost in every case accompanied byhydrocephalus. Concerning the different aspects of cognitive performance of patients withhydrocephalus alone, Fletcher et al. (1992) showed lower nonverbal skills for children withhydrocephalus independent of the etiology of hydrocephalus. While they found interactions ofhydrocephalus with verbal and nonverbal discrepancies, these discrepancies were not related tothe motor demands of the tasks. According to Fletcher et al. (1992) these results could reflectspatial processing deficits in the hydrocephalic children, since the nonverbal tasks included theJudgment of Line Orientation Test (JLO). Additionally, Brookshire et al. (1995) established thatchildren with shunted hydrocephalus have an impaired development of nonverbal skills (includ-ing spatial abilities measured with the JLO) compared to verbal cognitive abilities. Further resultsrevealed that patients with spina bifida and hydrocephalus and patients with hydrocephalus only

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MENTAL ROTATION IN CHILDREN WITH HYDROCEPHALUS 435

showed deficits in spatial recognition memory, spatial memory span, spatial working memory,and executive functioning (Iddon, Morgan, Loveday, Sahakian, & Pickard, 2004). It seems thatthe tests that require the integration of several cognitive processes are especially impaired in thesesubgroups. In contrast, the patients with SB did not demonstrate cognitive impairment in thesetests. Lindquist, Uvebrant, Rehn, and Carlsson (2009) suggested that hydrocephalus is the mainfactor that causes the cognitive deficits in children with spina bifida and therefore, the cognitiveoutcome in children with spina bifida is dependent on the associated brain abnormalities ratherthan on the spina bifida itself. This was further supported by the differences found between chil-dren with spina bifida and either shunt-treated or arrested hydrocephalus (Hampton et al., 2011).They found that children with an arrested hydrocephalus revealed altered neuropsychologicaloutcomes but perform on a higher level than children who are shunt-treated. Another interestingresult of this study was that fine motor performance was especially impaired in the shunt-treatedgroup.

To summarize, impaired mental rotation ability has been investigated in children with spinabifida and hydrocephalus; however to our knowledge no research has addressed performance dif-ferences between SBHC and HC children. Both groups differ by their motor ability. Children withSBHC often have impaired ambulation as well as secondary upper extremity defects and motorprecision deficits. Due to this, the question remains, whether the reduced mental rotation abilitycan be attributed to the spina bifida and the associated motor disabilities. If the motor disabilitiesare the cause of the impaired mental rotation performance, children with HC without impairedmotor abilities associated with spina bifida should show a better performance than children withhydrocephalus and spina bifida. If the impaired mental rotation performance is caused by the brainabnormality there should be no difference in the performance between HC and SBHC children.To investigate our hypotheses we tested the mental rotation ability of children with SBHC andthose with HC as well as the performance of healthy controls compared to both patient groups.

METHOD

Participants

Twenty-four children between 8 and 12 years old took part in the study. They were divided intotwo groups: one group of 12 children with both spina bifida and hydrocephalus (SBHC), and onegroup of 12 children with hydrocephalus only (HC). Children with HC were recruited throughthe cooperation with the Neurosurgery Center of the Regensburg University Hospital. The datafor the children with SBHC was obtained from the entrance tests of a former study by our group,in which a training program for children with spina bifida was evaluated (Lehmann & Jansen,2012). A control group of 12 children, matched according to age, sex, and estimated IQ, wasincluded in the analysis to investigate the performance of the two clinical groups in relation tohealthy children. This experiment was conducted according to the guidelines of the ethical reviewcommittee, which was informed of the study and our final experimental plan.

For both clinical groups a questionnaire was used to assess general demographic informa-tion and information regarding medical condition and infantile motor development. All childrenin the SBHC group had a myelomeningocele and suffered from hydrocephalus. Eleven of thesechildren were treated with a shunt. The localization of the lesion was in the lumbar region in

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10 children, and the thoracic region in two children. None of the children in the SBHC groupsuffered from epilepsy, uncontrolled seizure disorder, perception disorder, or behavioral distur-bances. The children in the HC group were all diagnosed with hydrocephalus. Eight of thesechildren had congenital, respectively neonatal hydrocephalus, while the other four children hadacquired hydrocephalus at the age of 7, 9, 10, and 11 years old, respectively. In six children withhydrocephalus the cause was neural malformation, in two children the hydrocephalus developedafter meningitis, in one child the cause was uncertain, in one child it occurred after hemorrhage,in one it was due to a craniostenosis, and in one it was due to a tumor. Eight HC childrenwere treated with a ventriculoperitoneal shunt, four were treated with a ventriculostomy. In bothclinical groups nine children were right-handed and three children were left-handed.

Regarding the motor abilities of the SBHC and HC children the means of the onset of walkingquoted in months are close together (SBHC: M 11.06 (1.19); HC: M 9.82 (1.59)), but the numberof children who are able to walk unassisted differ between those groups. While all of the childrenwith HC were able to walk unassisted, children in the SBHC group differ regarding their walkingability. Four children were able to walk on their own with the support of ortheses, another fourchildren were able to walk a short distance with the help of ortheses, but needed a wheelchair forlonger distances, and the last four children were restricted to their wheelchairs and were not ableto walk.

The two clinical groups were also matched in gender, age, and cognitive processing speed. Thechildren were matched according to gender (χ2(2, n = 36) = 1.56, n.s.), age (F (2,33) = .125,n.s.), cognitive processing speed (F (2,33) = 2.74, n.s.) , and diagnosis (HC vs. SBHC) (compareTable 1). Matching by cognitive processing speed was applied, because it is well known thatchildren with spina bifida showed a slower reaction time per se. None of the data sets of thechildren were excluded from the analysis.

TABLE 1Descriptive Statistics (Mean and Standard Deviation) of the Participants in Each Group

Spina Bifida(n = 12)

Hydrocephalus(n = 12)

Healthy(n = 12)

Age (years) 10.00 (1.6) 10.25 (1.71) 10.00 (0.74) F(2,33) = .125, n.s.Estimated IQ 81.42 (0.51) 93.75 (23.31) 95.25 (11.5) F(2,33) = 2.74, n.s.Gender χ2(2, N = 36) = 1.56, n.s.

male 5 8 6female 7 4 6

Ethnicity All German All German All GermanType of school∗ χ2(5, N = 36) = 50.069,

high school 0 1 12 p < .01middle school 2 6 0special needs school 6 2 0primary school 5 3 0

Note. While statistical significant differences are in place between the three groups, this parameter was not included inthe analysis of the study. The important parameter for the analysis in this study was the estimated IQ value.∗The German school system is divided into different types of schools. Children attend a primary school between the ageof 6 and 10 years. Middle school, high school, and special needs schools are for children aged between 10 and 18 years.

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MENTAL ROTATION IN CHILDREN WITH HYDROCEPHALUS 437

FIGURE 1 Example for the stimuli used in the chronometric mentalrotation test (Jansen-Osmann & Heil, 2007).

Material

Number Connecting Test. Cognitive speed was measured with the Number ConnectingTest (ZVT; Oswald & Roth, 1987). This test consists of four different sheets of paper for testingand one additional paper with practice examples. The practice sheet is composed of two matricesin which the numbers 1 to 20 are presented. The other sheets contain the numbers 1–90 thatare presented in an irregular sequence in a matrix of 9 rows and 10 columns. Each participantwas instructed to connect the numbers in the ascending order as fast as possible with a pen. Thetime that was needed to connect all ninety numbers was measured. After completing all fourtesting sheets the times of all are added and divided by four. The mean cognitive speed resultscan be converted into IQ estimations based on a conversion table in the manual which gives anIQ value according to the age and result of each child. The correlation between the ZVT and thestandard IQ test is about r = .60–.80 (Vernon, 1993). Internal consistency and 6-month test–retestreliability is about .90–.95. The test was assessed at the beginning of each testing session. TheZVT is the equivalent to the Trail Making Test A (Reitan, 1956).

Chronometric mental rotation test. The participants’ mental rotation ability was assessedwith a chronometric mental rotation test. Each child was tested individually and in familiar sur-roundings. The test was presented on a laptop with a 17” monitor. The experimental stimuliconsisted of 18 perspective line drawings of three-dimensional cube figures similar to the onesused by Shepard and Metzler (1971), and Jansen-Osmann and Heil (2007) (see Figure 1). Eachstimulus was displayed in the approximate size of 7 cm x 7 cm and the distance between thetwo stimuli was 14 cm. Participants were allowed to choose their most comfortable viewing dis-tance. Throughout the test two stimuli were presented at the same time on the screen. The leftstimulus served as the standardized stimulus; the right stimulus was either an identical or mirror-reversed image of the first. The angular disparity between the two stimuli was 0◦, 90◦, or 180◦ ina clockwise or counterclockwise direction.

Due to the general procedure of a chronometric mental rotation test and its use in stud-ies with children with spina bifida (Wiedenbauer & Jansen-Osmann, 2007), all children wereinstructed to decide as quickly and accurately as possible whether the two stimuli were thesame or mirror-reversed. They had to press either the left button of the mouse (indicating the“same” answer) or the right button (indicating the “mirror-reversed” answer). To clarify the

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options, the response buttons were marked with green (left button) and red (right button) stickers.The trials began with a fixation cross presented for 500 msec in the middle of a white screen.Thereafter, the stimuli appeared and remained on the screen until the participant responded.Feedback was given to each participant in form of a “+” for the right answer and a “-” forthe incorrect answer. The feedback was presented for 500 msec. The next trial was initiated after1,500 msec. Every combination of objects (18 cube figures), type of response (same/mirror-reversed), and angular disparity (0◦, 90◦, 180◦) was presented three times, which resulted in atotal amount of 324 trials. To familiarize the children with the task, a block of 54 unrecordedpractice trials were performed at the start of the testing session. The following 324 test trialswere presented with breaks after every 27th trial. The reaction times and the error rates weremeasured.

Procedure. Each child was tested by the same principal investigator in a quiet room. At thebeginning the parents were given the questionnaire and they were asked to complete it whilethe children were tested. Each session began with the Number Connecting Test after which thechronometric mental rotation test was conducted. The whole test procedure lasted about 1 hour.

STATISTICAL ANALYSIS

For the analysis of the data the system SPSS 18.0 was used. Because angular disparity is notunambiguously defined for “different” responses (see, e.g., Jolicoeur, Regehr, Smith, & Smith,1985), all statistical analyses were restricted to “same” responses only. Before statistical analysisthe reaction time (RT) data of each child was trimmed. RTs more than two standard deviationsabove or below the mean per condition and per participant were excluded. This resulted in anexclusion of 3.1% of the RT data. The dependent variables “reaction time” and “error rate” wereincluded in the two analyses of variance with the between-subject factor “group” (HC, SBH, CG)and the within-subject factor “angular disparity” (0◦, 90◦, 180◦).

RESULTS

Reaction Time

There was a main effect for the factors “angular disparity,” F(2,66) = 91.76, p < .001, η2 = .736,and “group,” F(2,33) = 3.92, p = .030, η2 = .192, and a significant interaction between “angulardisparity” and “group,” F(4,66) = 3.21, p = .05, η2 = .163. The interaction between “angulardisparity” and “group” is due to the fact that there is no significant difference in the three groupsin the 0◦ condition, F(1,33) = 1.29, n.s., η2 = .073, but there is a significant difference in the90◦, F(1,33) = 3.79, p = .033, η2 = .186, and the 180◦ conditions, F(1, 33) = 4.027, p = .027,η2 = .196 (compare Figure 2). This interaction is also present when estimated IQ is consideredas a covariate (F(4,64) = 3.76, p = .008, η2 = .190). In both rotated conditions, Bonferronipost-hoc tests revealed only significant performance differences between children with SBHCand HC, showing a faster reaction time for the HC group (90◦: p = .034; 180◦: p = .023). Thedifferences in reaction time for the 90◦ and 180◦ condition between the children of SBHC goup

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MENTAL ROTATION IN CHILDREN WITH HYDROCEPHALUS 439

FIGURE 2 Reaction times for the three different angular disparities (0◦,90◦, and 180◦) and the three groups of children (SBHC = children withspina bifida and hydrocephalus, HC = children with hydrocephalus, CG= healthy children). ∗p < .05.

and healthy children failed to reach significance (90◦: n.s.; 180◦: n.s.). Additionally, no significantperformance differences were revealed between children with hydrocephalus and healthy children(90◦: n.s.; 180◦: n.s.).

Error Rate

A repeated-measures ANOVA assessing the error rate revealed a significant main effect for thefactor “angular disparity,” F(2, 66) = 98.58, p < .001, η2 = .749, but not for the factor “group,”F(2, 33) = .189, n.s, η2 = .011. No interaction was found between “angular disparity” and“group,” F(4, 66) = .443, n.s., η2 = .026.

The error rate increased from 0◦ to 90◦, F(1,35) = 146.87, p < .001, η2 = .808, and decreasedfrom 90◦ to 180◦, F(1,35) = 9.49, p = .004, η2 = .213, but increased from 0◦ to 180◦, F(1,35)= 68.23, p < .001, η2 = .757. In the 0◦ condition 9.9% (SE = .99) of the answers were wrong,in the 90◦ condition 47.18% (SE = 3.48) of the answers were wrong, and in the 180◦ condition40.12% (SE = 3.43) were wrong (compare Table 2).

Additional Results

Because the SBHC group all had congenital hydrocephalus and the HC group consisted ofpatients with either congenital or acquired hydrocephalus, we compared the data for the children

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TABLE 2Means and Standard Deviation (SD) for the Reaction Times and the Error Rate (%) Overall and for Each

Group Separate for the Three Different Angular Disparities

Overall Spina Bifida Hydrocephalus Healthy

0◦Reaction time 2077.77 (94.90) 2218.18 (180.45) 1867.36 (134.18) 2146.96 (170.45)Error rate 9.88 (.98) 8.97 (1.81) 9.41 (1.79) 11.12 (1.59)

90◦Reaction time 4480.38 (312.64) 5562.03 (539.09) 3653.80 (478.33) 4225.31 (489.06)Error rate 47.17 (3.41) 46.45 (4.18) 50.77 (7.36) 44.29 (6.11)

180◦Reaction time 4333.15 (247.27) 5137.03 (445.87) 3550.38 (359.78) 4312.03 (375.37)Error rate 40.12 (3.35) 39.82 (5.04) 43.05 (7.55) 37.50 (4.84)

of the SBHC and HC groups using the data of the eight children of the HC group who have con-genital HC. Considering the etiology of hydrocephalus in the HC group, an additional analysis ofvariance was conducted with the variables “reaction time” and “error rate,” the between-subjectfactor “group” (HC congenital only, SBHC), and the within-subject factor “angular disparity”(0◦, 90◦, 180◦). Both analyses were comparable to the data from “reaction time” and “error rate”presented before: The analysis of variance with the variable “reaction time” resulted in a maineffect for “angular disparity,” F(2,58) = 75.73, p < .001, η2 = .723, and “group,” F(2,29) = 3.68,p = .038, η2 = .203, and an interaction between both factors, F(4, 58) = 3.213, p = .019, η2 =.181. Additionally, a main effect with the variable “error rate” was found for “angular disparity,”F(2,58) = 103.71, p < .001, η2 = .781. The results did not show a main effect for “group,” F(2,29) = 1.267 n.s., η2 = .080, nor an interaction between “group” and “angular disparity”, F(4, 58)= 1.325 n.s., η2 = .084.

DISCUSSION

The present study investigated the mental rotation ability of children with hydrocephalus, bothwith (SBHC) and without spina bifida (HC) and a matched healthy control group, on a three-dimensional mental rotation task. Comparing the performance of children with SBHC, HC andhealthy children: only differences in performance between children with SBHC and HC reachedsignificance, the difference between the SBHC group and healthy children failed to reach signif-icance. This indicates that the experiment was neither too difficult for the two clinical groups nortoo exhausting. Children with SBCH showed a slower reaction time in the mental rotation testcompared to children with HC. The difference was only detectable when the objects were rotatedand not in the 0◦ condition. These results show that differences exist only in those conditionswhere a rotation is required. In the 0◦ condition the presented objects have to be perceived andencoded, but no rotation is necessary. This suggests that the rotation process itself is affectedbut not for example the perception process. There was no difference in the accuracy rate. Thisis in accordance with many other studies showing that reaction time is the more sensitive mea-surement. However, because on the one hand the accuracy rate did not differ and on the other

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hand the accuracy rate is used for the analysis of strategies used (compare Amorim, Isableu, &Jarraya, 2006), we can conclude that there were no different strategies used to solve the mentalrotation tasks between the three groups. At the first glance our results seem to contradict formerstudies: Iddon et al. (2004) found no differences in visual and spatial cognition between the twosubgroups SBHC and HC. Also, Lindquist, Persson, Uvebrant, and Carlsson (2008) detected nodifferences in performance on visuospatial tasks between those two subgroups. He suggested thatthe hydrocephalus itself may be the cause for the impairment and not the myelomeningocele (seealso Lindquist et al. 2009). All of these studies included visual–spatial testing, but they did notspecifically test the mental rotation performance. It seems that while the more general measure-ments used in the previously mentioned studies do not show differences between SBHC childrenand HC children, a more precise measurement of one specific spatial task does show differencesbetween these two groups. Even when considering the etiology of hydrocephalus in our study, dif-ferences in mental rotation performance still exist. The different etiology of hydrocephalus wasconsidered due to the fact that the cause of the disorder can influence the cognitive developmentof the child. Children with acquired hydrocephalus might have normally developing cognitivefunctions up to the onset of their disorder and then have lost some function, while children withcongenital hydrocephalus might not develop these cognitive functions at all (Iddon et al., 2004).Since hydrocephalus can result in secondary brain injuries, which can result in compression ofthe white and grey matter causing damage to cortical neurons (Del Bigio, 1993), concomitantcognitive and behavioral limitations can appear.

To explain the difference in mental rotation ability found in this study between SBHC childrenand HC children, one should consider other causal aspects in addition to the cognitive states ofthese children. The relationship between mental rotation and motor components has been a focusof investigation in children with spina bifida. For example, Jansen-Osmann et al. (2008) examinedchildren with spina bifida regarding the influence of mobility on spatial abilities. They found acorrelation between the age of walking and performance in visuospatial memory and orientationin a maze. Children who learned to walk later in life had a poorer performance than those wholearned to walk earlier. Additionally, Stanton, Wilson, and Foreman (2002) showed that childrenwith restricted mobility in early childhood performed worse in a simulated maze task than chil-dren with normal mobility. These studies suggest that free movement in early childhood enableschildren to explore spatial movement and develop spatial experiences, which have permanentinfluence on spatial abilities in later life (see also Rendeli et al., 2002). Additional evidence canbe provided by studies that have investigated the influence of motor training on mental rotationperformance in adults, healthy children, and children with spina bifida. Studies have specificallyshown beneficial effects of juggling training on mental rotation abilities (Jansen, Lange, & Heil,2011; Jansen, Titze, & Heil, 2009; Lehmann & Jansen, 2012). To explain the trends found inthese studies, it has been suggested that mental rotation processes are directly connected to motorprocesses (Funk, Brugger, & Wilkening, 2005). In their study they used pictures of hands as stim-uli and participants were asked to decide whether the image was a right or a left hand. Reactiontimes increased when the position of the shown hand was more difficult to imitate by the partici-pant’s own hand. These studies support the idea that there is a close relationship between motorand cognitive processes; this provides a possible explanation for the differences in reaction timesseen in the mental rotation tasks between SBHC and HC children. However, we only evaluatedour participants motor abilities using a questionnaire and therefore, this explanation should beregarded cautiously. It might be possible that secondary to the Chiari malformation in children

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with spina bifida deficits in motoric precision and manual control in the upper extremity existsthat have influenced the results of this study. This has to be regarded in further studies as wellas the possibility that cerebellar mediated impairments that interfere with rhythmicity and timingmight be responsible for the detected differences in reaction times.

A new result was that children with HC have similar mental rotation abilities to healthy chil-dren. This means that the better performance of the HC children is comparable to the performanceof healthy children. This is an interesting result that has not been found before. Even though someauthors suggest that hydrocephalus is associated with cognitive impairment (Iddon et al., 2004),mental rotation ability does not seem to be affected. Yet, these results have to be replicated witha larger sample in which the etiology of hydrocephalus could be evaluated in more detail.

The results of this study can contribute to developing new therapeutic approaches for childrenwith both spina bifida and hydrocephalus, since it seems that the spina bifida rather than thehydrocephalus influences mental rotation performance and perhaps the general spatial abilities ofthese children. Therefore, the focus of therapy should be on the improvement of the locomotorrestrictions that are associated with spina bifida and consequently with motor abilities. Becauseit has been shown that some motor abilities, such as juggling (Lehmann & Jansen, 2012), caninfluence mental rotation performance, these motor abilities should be used as training for thesechildren. If such motor trainings affect spatial abilities in children with spina bifida, it mightbe possible to combine different therapies and make them more effective for both physical andcognitive functions and therefore reduce the amount of therapy for these children.

Limitations of the Study

In contrast to the study of Wiedenbauer and Jansen-Osmann (2007) performance differencesbetween the SBHC children and the healthy children did not differ significantly. This might be dueto the smaller sample size in this study or the matching procedure. In the study of Wiedenbauerand Jansen-Osmann (2007) the children were also matched by age and sex, but by the verbal IQand not by the estimated IQ. The question of whether to control the IQ or to use it as a controlvariable is a critical one. Dennis et al. (2009) suggested that using IQ as a covariate in childrenwho have neurodevelopmental disorders is inappropriate because it does not meet the require-ments of a covariate and it can influence the interpretation of cognitive processes. Furthermore,Dennis et al. (2009) recommend the inclusion of discriminate variables that are independent fromthe dependent variable and therefore are more appropriate than IQ as a covariate. Consequently,further investigations of children with spina bifida should not include IQ as a covariate but rathershould focus on more appropriate discriminate variables, for example top-down and bottom-upcontrol (Dennis et al., 2005).

As in the former studies regarding mental rotation in children with spina bifida (Lehmann &Jansen, 2012; Wiedenbauer & Jansen-Osmann, 2007), the procedure and the test length seem tobe appropriate; however, this effect could be investigated experimentally by varying, for example,the length of the procedure. Additionally, further studies should include a simple non-cognitivereaction time task to control for the general reaction time characteristics in SBHC and HC chil-dren. Due to the non-existing differences in the 0◦ condition in this study one could assume thatthe reaction time pattern does not differ between the groups. However, the 0◦ condition might notbe a simple reaction time task since next to perception processes a comparison between two items

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has to be accomplished. Therefore, a simple non-cognitive reaction time task would contribute toelucidate the reaction time pattern in more detail. With such a task it could be clarified whetherthe Chiari malformation and the effects of hydrocephalus on white matter tracts might be relatedto processing speed in children with spina bifida and therefore might influence the reaction timeresults due to a reduced speed of synaptic transmission.

Conclusion and Further Studies

In summary, children with both hydrocephalus and spina bifida show reduced mental rotationabilities compared to children with hydrocephalus only. It seems that this impairment might beconnected with the motor abilities in these children. If so, it might be worth investigating theinfluence of motor training on mental rotation as well as the effect of mental rotation trainingon motor abilities in those children. However, the exact relationship between mental rotation andmotor abilities remains unclear. Future research should focus on this possible connection in moredetail by investigating a larger group of children with spina bifida and addressing the mentalrotation performance by including the on-set of locomotion, the localization of the lesion, and thespecific motor abilities as far as can be tested with a standard instrument such as the MovementAssessment Battery for Children–2 (Petermann, 2009).

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