Family patterns of developmental dyslexia, part II: Behavioral phenotypes

Abstract

The motor control of bimanual coordination and motor speech was compared between first degree relatives from families with at least 2 dyslexic family members, and families where probands were the only affected family members. Half of affected relatives had motor coordination deficits; and they came from families in which probands also showed impaired motor coordination. By contrast, affected relatives without motor deficits came from dyslexia families where probands did not have motor deficits. Motor coordination deficits were more common and more severe among affected offspring in families where both parents were affected than among affected offspring in families where only one parent was affected. However, motor coordination deficits were also more common and more severe in affected parents when both parents were affected than among affected parents in families where only one parent was affected. We conclude that impaired temporal resolution in motor action identifies a behavioral phenotype in some subtypes of developmental dyslexia. The observed pattern of transmission for motor deficits and reading impairment in about half of dyslexia families was most congruent with a genetic model of dyslexia in which 2 codominant major genes cosegregate in dyslexia pedigrees where the proband is also motorically impaired.

Temporal Processing Deficits in Remediation-Resistant Reading-Impaired Children

“…For example, Bakker [31]has suggested that children with reading impairments have difficulty with the sequential reproduction of ordered stimuli and that this deficit in recall is present for auditory, visual and haptic stimuli. This observation is also consistent with the work of Wolff et al [32, 33]. They showed that impairments intemporal processing are not limited to sensory-perceptual tasks and can be manifest on simple motor-sequencing tasks as well.…”

Deficits in Coordinative Bimanual Timing Precision in Children With Specific Language Impairment

“…Lashley (1951) proposed that neural mechanisms responsible for timing precision and serial order control underlie both language production and skilled movement. In line with this hypothesis, and consistent with findings in children with dyslexia (Wolff, Melngailis, Obregon, & Bedrosian, 1995), Bishop (2002) suggested that a deficit in timing precision (i.e., the ability to keep time with relatively low levels of variability) underlies both the language and motor deficits seen in children with SLI. Timing deficits also may be predicted on the basis of prosodic difficulties apparent in children with SLI (Gerken & McGregor, 1998;Goffman, 1999Goffman, , 2004McGregor & Leonard, 1994).…”

“…In the dyslexia literature, several studies have reported timing control deficits in bimanual coordination tasks with half of the participants with dyslexia affected (Wolff, 1993;Wolff, Michel, Ovrut, & Drake, 1990;Wolff et al, 1995). Given that SLI and dyslexia are often comorbid (Snowling, 2012), and procedural learning deficits have been implicated in children with SLI, it is reasonable to hypothesize that bimanual coordination is impaired in children with SLI.…”

Motor immaturity and specific speech and language impairment: Evidence for a common genetic basis

“…It is important to stress that Wolff et al [1995] measured precision of motor timing in a task where the child was required to tap in time to a metronome and continue at the same rate after the metronome stopped. In contrast, the current studies used simpler speeded motor tasks.…”