Developmental coordination disorder (DCD) is a neurodevelopmental motor disorder characterized by immature and delayed gross and fine motor development without obvious medical or intellectual causes that noticeably disturbs daily activities (American Psychiatric Association, 2013). Globally, it is calculated to affect between 5 and 13% of schoolchildren (Cairney et al., 2006; Hillier, 2007; Vaivre-Douret, 2014) and there is often a higher incidence in boys as opposed to girls in a ratio of between 2:1 and 7:1 (American Psychiatric Association, 2013). Although there is agreement in respect of the meaning of the concept DCD, still other terms are used more or less synonymously (Ahonen et al., 2004; American Psychiatric Association, 2013) not least because motor difficulties appear in association with several other disorders. According to Gillberg (2010), this co-morbidity within both child psychiatry and developmental medicine is usually the rule rather than the exception. Consequently, DCD can appear together with ADHD (Kadesjö and Gillberg, 1998; Pitcher et al., 2003; Watemberg et al., 2007), as well as with speech difficulties, reading and writing difficulties (Visser, 2003) and with emotional problems (De Raeymaecker, 2006; Cairney et al., 2010). That motor problems do not disappear with age has been shown in a number of studies (e.g., Fox and Lent, 1996; Christiansen, 2000; Rasmussen and Gillberg, 2000; Sigmundsson, 2005) although McPhillips et al. (2000) showed that the reading abilities of participants were positively affected when participants integrated the asymmetrical tonic neck reflex (ATNR) through carrying out stereotypical infant movements. Furthermore, Norlander et al. (2005) showed that a short but regularly performed training program applied to primary and secondary school children addressing the kinesthetic-vestibular systems reduced the noise levels in classrooms and increased the teachers’ rating of the children’s concentration capacity.

The existing definition of DCD (American Psychiatric Association, 2013) does not mention any connection to a sensory cause. What is briefly described though are neurodevelopmental immaturities or neurological soft signs (NSS), which contain a broad scope of neurological deviations, for example, mirror movements, choreiform movements and retained primary reflexes (McPhillips et al., 2000). What these have in common is that they are not considered to belong to any well-defined syndrome, they are difficult to interpret (Touwen, 1993; Polatajko, 1999; Ayd, 2000) and their diagnostic and clinical value is still unclear and therefore further studies are needed (American Psychiatric Association, 2013). At the Vestibularis Clinic, a Swedish center for sensorimotor therapy (SMT), a method for integration of retained primary reflexes (Field and Blythe, 1989) was practiced in order to help children develop their motor abilities. It was, however, observed that motor training became even more efficient when vestibular function was implemented both as a diagnostic tool (Rasmussen et al., 1983; Rasmussen and Gillberg, 2000) and as a part of therapy (Niklasson, 2013) resulting in the method Retraining for Balance (RB; Niklasson et al., 2009, 2010). RB is, in part, a process orientated therapy (Kirby and Sugden, 2007) because it emphasizes the importance of identifying underlying sensory and motor problems, which prevented the individual from developing his or her complete motor skills. In part, it is also an implicit process (Gentile, 1998; Ahonen et al., 2004) where movements activate and organize proprioception as well as vestibular functions. Kirby and Sugden (2007) questioned whether or not DCD is a single syndrome and stressed the complexity of co-morbidity (Visser, 2003; Lingam et al., 2010). Vig (2010) discussed further the importance of labeling and classifying children with disabilities based upon empirical data. Empirical data (Niklasson et al., 2009, 2010) has shown that within the framework of the RB method, it is possible both to diagnose and then treat sensorimotor problems through SMT. Adding the significance of sensory factors, such as vestibular function, for motor development to the existing DCD criteria should increase the possibility of unambiguity in respect of its definition. A tentative suggestion would be that DCD could be more properly labeled as a sensorimotor disorder (SMD). Unpublished studies at the Vestibularis Clinic regarding SMT also call the criteria for DCD into question on the basis that the therapy is also effective for children younger than 5 years of age and for children and young people with intellectual disabilities (Geuze et al., 2001). The present paper will henceforth use the concept SMD.

The primary reflexes, which are essential for an understanding of the phenomenon SMD, consist of around 70 brainstem-mediated behavioral movement patterns (Schott and Rossor, 2003; Niklasson et al., 2009) traditionally considered to belong to early childhood and expected to be integrated by the higher brain centers, which is typical of normal neurological development. Scherzer (1985), Capute and Accardo (1991) as well as Zafeiriou (2004) distinguished primary reflexes that are found in the newborn and which are normally integrated in early childhood from postural reactions, which appear more or less in parallel. Among the primary reflexes they considered as having a diagnostic value were the Moro reflex, the ATNR, the tonic labyrinth reflex (TLR), the grasp reflex in the hands and feet as well as the suck and search reflexes. Important postural reactions were the Landau reaction as well as the head righting reactions. In total, around 15 reflexes were of diagnostic interest. If the primary reflexes do not integrate and if the postural reactions do not develop, there is a risk that the child acquires sensorimotor as well as learning and social difficulties (Goddard Blythe, 2009).

In a naturalistic study (Niklasson et al., 2009) of 232 children and young people (181 boys and 51 girls) between the ages of 5–17 years (M = 9.3, SD = 2.7) with concentration problems and motor difficulties who all had followed and completed a SMT program, Retraining for Balance, a number of primary reflexes and postural reactions were studied. On average, the training time was around 3 years and in order to be able to make a comparison between different ages the participants were divided into three groups according to their ages at the start of training: one younger group with 65 children who were 7 years or younger at the start (M = 6.2, SD = 2.0); a middle group with 91 children who were 8–10 years (M = 9.0, SD = 0.8); and finally a group with older children who were 11 years and older (M = 12.3, SD = 1.7). Measured through a number of sensorimotor tests, the results showed significant effects of the training in all three age groups. Biological maturation was suggested by the fact that the older group performed better in comparison with the two other groups before commencing SMT. Furthermore, after the therapy, both the older and middle group performed somewhat better than the younger group. A follow up study (Niklasson et al., 2010) analyzed the results regarding eight children who had completed therapy according to Retraining for Balance. The analysis showed that the process of SMT could be described according to a Kinesthetic-Vestibular Development Model whereby the therapy’s exercises (introductions) gave rise to temporary psychological and/or physical regressions, which were followed by periods of positive psychological and physical development (transformations). In order to examine if the results could be generalized to a larger group of children, the results of the eight participants were compared with the results of the 224 participants who had also completed the training. The quantitative analysis showed that 95% of the children in the larger group had a “very good” or “good” adjustment to the model. Together, both studies indicated that it is seems to be possible to influence sensorimotor (physical) maturity as well as psychological development with children and young people up to 17 years of age by integrating primary reflexes.

Retained or newly appeared primary reflexes are, according to some researchers, a sign of neurological pathology (e.g., Schott and Rossor, 2003; Zafeiriou, 2004) whilst others are of the opinion that the re-appearance of some primary reflexes can be a part of the natural aging process (e.g., Hobo et al., 2014). Touwen (1984) criticized both theories and was of the view that it would be remarkable if a degenerated adult brain could regain the qualities of a child’s brain. The grasp, palmomental, suck, snout and glabellar reflexes, all primitive reflexes with clinical diagnostic value in, amongst others, stroke patients (Chang, 2001) and in patients with dementia and Parkinson’s disease, are activated through tactile stimulation and have, to a limited extent, also been found in healthy adults (e.g., Brown et al., 1998; Schott and Rossor, 2003) but without any link to impaired cognitive abilities (van Boxtel et al., 2006). Several studies (e.g., Bruijn et al., 2013) have made clear that vestibular-proprioceptive connected primary reflexes such as the ATNR and the symmetrical tonic neck reflex (STNR) can be triggered even within healthy adults and can be considered to be natural components in daily motor activities. Also, Easton (1972) stated that primary reflexes could constitute the foundation of sensorimotor organization and Fukuda (1961) wrote that the vestibular system plays an important role for the way we move ourselves as well as for postural development. Clinical conclusions based on retained primary reflexes in adults are, however, a controversial subject (Schott and Rossor, 2003; Zafeiriou, 2004) because primary reflexes are both difficult to interpret and are traditionally associated with some type of brain injury. However, Hurst Vose (1986) has anecdotally described the sensorimotor training she went through after she had been struck by agoraphobia and which resembles the training of children which has been described by McPhillips et al. (2000), Goddard Blythe (2005), and Niklasson et al. (2009). In recent years, research has shown that the brain has previously unknown possibilities of self-healing and restitution after injury (Stein et al., 1997; Kempermann, 2006; Doidge, 2007) and studies have shown that different types of training affect general sensorimotor capabilities of both the elderly and the brain injured (e.g., Beinert and Taube, 2013; Ortega and Jolkkonen, 2013; Patel et al., 2013; Degen and Schröder, 2014; Meunier et al., 2014).

A summary of the various findings lead to the assumption already made by Teicher (1941) in his studies of Schilder’s test (the ATNR and the TLR in standing position) with more than 200 children, namely that, when children approached puberty their movement patterns became more and more like adults. Examples of this can be seen from the fact that minor neurological signs became less pronounced amongst children of 11 years of age (Peters et al., 1975). Additionally, during adolescence the connections in the brain develop, becoming fewer but faster (Giedd et al., 2008) and the nervous system will become more vulnerable to trauma (Eckes and Radunovich, 2007). Furthermore, a summary of earlier research findings indicated that development was described as moving forward (Touwen, 1984; Connolly, 1986; Brodal, 2004; Goldfield and Wolff, 2004; Klonowski, 2007) which means that a physiological return to earlier developmental stages in order to influence maturity becomes hard to explain. Even if the adult’s sensorimotor system nowadays is considered to be plastic (Canu et al., 2012), it is difficult to find in the literature a convincing support for intentional physiological regressions in adults. Therefore, the conclusion may be drawn that it is considerably more difficult for adults to benefit from SMT compared with young people.

The present study is, as far as known, the first attempt to investigate whether primary reflexes can be found in adults voluntarily expressing a wish to be assessed for symptoms of SMDs, and, if so, is it possible to integrate these reflexes through SMT? In light of the above literature review two hypotheses were formulated concerning individuals with SMDs: (a) there are few or no significant differences in terms of sensorimotor abilities among a group of youngsters who are 11 and older and a group of adults 18 years and older before completing the SMT, (b) the adult group will exhibit significantly poorer performance compared with the youngsters after completing the SMT.

This study had two hypotheses regarding comparisons between a group of adults and a group of youngsters, both with SMDs, namely (a) there are few or no significant differences in terms of sensorimotor abilities among a group of youngsters who are 11 years and older and a group of adults 18 years and older before completing the SMT, and (b) the adult group will exhibit significantly poorer performance compared with the youngsters after completing the SMT.

The first hypothesis could, on the whole, be accepted because there were no differences between the adult group and the youngster group in respect of the Physiological Test (RB-P), the Orientation and Balance Test (RB-OB) and the KVS before undergoing SMT. On the other hand, a difference appeared in respect of the Audiometric Test (RB-A) in which the youngsters performed better than the adults before and after therapy with regard to right ear dominance. RB-P and RB-OB are two similar test batteries which overlap each other when it comes to motor and vestibular functions whilst KVS is a complementary test which measures the relationship between visual skills and vestibular function. The results from RB-P and RB-OB are in line with research which has shown that in early puberty the movement patterns of youngsters become more and more like adults (Teicher, 1941; Peters et al., 1975) and that motor difficulties do not disappear with age (e.g., Rasmussen and Gillberg, 2000). Teicher (1941) also showed in his study that there was a great difference between the movement patterns of very young children and older youngsters while sometimes the difference was insignificant between children of similar ages. This difference could also be seen in a later study (Niklasson et al., 2009) where an older group of children (11 years and older), before therapy, performed better on RB-P than both the middle group (8–10 years) and the younger group (7 years and younger). The results of the KVS Tests indicated that visual skills and motor capacities correlated with each other. Previously it has been pointed out that children with sensorimotor problems had visual difficulties (Creavin et al., 2014) and that they ran a greater risk of developing problems with reading and spelling (Lingam et al., 2010).

A previous study (Niklasson et al., 2009) showed no significant differences prior to therapy in respect of RB-A between the three age groups but in the present study the youngsters performed better with regard to right ear dominance than the adults. One reason could be age-related changes (Warren et al., 1978) which make it harder to distinguish with the right ear (Okamoto et al., 2007) whilst other studies (Findlay and Schuchman, 1976; Jerger et al., 1994; Hämäläinen and Takio, 2010) have shown that the preference to use the right ear increases with age. Another reason could be gender-related differences. The present study was comprised of 13 women and only one man. Phillips et al. (2001) showed that women to a higher degree than men use both hemispheres of the brain for passive listening, which could explain why the youngsters initially performed better than the adults. However, a meta-analysis (Sommer et al., 2004) did not show any such significant differences.

The second hypothesis was partly rejected and partly accepted. Although both groups achieved a significantly better result after therapy on the Physiological Test (RB-P), the Orientation and Balance Test (RB-OB), the Audiometric Test (RB-A) as well as on the KVS, the adult group performed significantly worse than the youngsters in tests in respect of postural reactions, eye movements, gross motor milestones and sports- related gross motor skills. The youngsters also achieved better results in respect of the RB-A Test and the KVS Test. On the other hand, having gone through the therapy, the adults performed as well as the youngsters in the RB-P Test as a whole and better than the youngsters in the RB-OB Test. The results are not coherent but still show for the first time that even adults with sensorimotor problems diagnosed as SMDs can integrate primary reflexes through specially adapted therapy. As tentatively suggested by Niklasson (2012), motor development could possibly be an emergent property partly dependent on primary reflex inhibition and vestibular stimulation. If so, primary reflex inhibition and vestibular function (Niklasson et al., 2009) could be the first links in such a developmental chain, followed by emerging postural reactions, gross motor milestones and sports related gross motor skills. The results of the present study showed both that there were no significant differences between the groups when it came to the integrating of primary reflexes and that the adult group performed better when it came to tests linked to vestibular functions.

The results seem to contradict former ideas concerning the possibilities of healthy adults to physiologically regress and transform and further studies are required for an increased understanding of the phenomenon. A tentative approach for further research could be to conceptually connect to physics and chemistry (Prigogine, 1978, 2003; Nicolis, 1993) via dynamic systems theories (Thelen and Smith, 2006) and to the field of epigenetics (Szyf, 2009). Previously, discussing DCD, Kirby and Sugden (2007) argued that a move toward a wider bio-social-educational model from the present narrow medical model would be vital. The reason for the adult group performing significantly worse on some tests after therapy could be due to age-related limitations. If so, the results also indicate the importance of adults, i.e., parents and teachers (Schilder, 1964), understanding the significance of early sensory stimulation of children.

In respect of gender differences, the present study did not permit any analysis but in an earlier study with children and youngsters (Niklasson et al., 2009) there were only a few differences to detect. Tentative speculation suggests that this might be very similar in a larger group of adults. However, an open question is why it was mostly women who voluntarily sought therapy? In the group of youngsters, it was mainly boys and their parents who sought help. A follow up study (Sigurdsson et al., 2002) has previously shown that untreated motor problems are to a higher degree linked to emotional problems in boys as opposed to girls in the teens.

The psychological part of the therapy process (Niklasson et al., 2010) seems to be closely intertwined with the sensorimotor exercises (Niklasson et al., 2009) and can be summarized through the KVDM, which shows how introductions, regressions and transformations in conjunction bring about enhanced physical (sensorimotor) and psychological development. In the present study, there were no significant differences between the group of youngsters and the group of adults in regard to degree of alignment to the KVDM. There were also no significant differences when a norm group was compared with the current groups. A comparison of the way in which children, youngsters and adults react in the way of regressions and transformations shows a similar pattern even if the reactions of the younger often are stronger. Midways in therapy a typical regression among children was an increased wish to be with their mother, often in combination with sadness without obvious reason. Similar behaviors were also described by the adults. One example of this notion was an adult who, in the middle of therapy, saw the back of an old woman reminding her of her deceased mother. She said that the mother had been gone for more than 10 years and that she hadn’t really missed her until now. Grief and a strong longing struck her instantly and she started to weep and had to hurry home. When it came to transformations participants in both groups could after regressions report improved ability to concentrate as well as improved academic achievement. Some of the adults were even able to return to work after long periods of being sick-listed. Periods of regressions and transformations for adults during SMT have not previously been described in the literature, but have been documented among children and youngsters (Niklasson et al., 2010). This might mirror a close and age-independent relationship between certain physiological movements and certain psychological expressions. If these observations are proved right in further studies, SMT might develop into a method for both physical wellbeing and a therapy for psychological development.

The present study had some limitations. One of these is the fact that there was only one man in the adult group. Because participants in the adult group had taken part in the therapy on their own initiative, there was nothing that could be done to increase the number of men participating. Furthermore, the adult group was, in total, small in comparison to the youngster group. These conditions should be remedied in future research. Future research should also comprise normative studies in order to ascertain the occurrence of primary reflexes and vestibular deviations in a normal population.

The results support both those studies which show that motor problems do not disappear with age and those which show that youngsters’ movement patterns during puberty become more and more like those of adults. Sensorimotor problems in early childhood should therefore be taken seriously (Rasmussen and Gillberg, 2000) and be the target of diagnostic examination and appropriate treatment. The results also show for the first time that the same diagnostic instrument and treatment method can be used for both children and adults with sensorimotor difficulties.

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.