The Effect of Methylphenidate on Neurological Soft Signs in ADHD

Bereitschaftspotential and lateralized readiness potential in children with attention deficit hyperactivity disorder: altered motor system activation and effects of methylphenidate

Attention deficit hyperactivity disorder (ADHD) has been linked to abnormal functioning of cortical motor areas such as the supplementary motor area, the premotor cortex and primary motor cortex (MI). The Bereitschaftspotential (BP) and lateralized readiness potential (LRP) are movement-related potentials generated by cortical motor areas. We hypothesized that the BP and LRP would be altered in children with ADHD. A group of 17 children with ADHD (mean age: 11.5 ± 1.9 years) and a control group of 16 typically developing children (mean age: 12.2 ± 2.0 years) performed movements at self-chosen irregular intervals while a 64-channel DC-EEG was registered. BP and LRP were calculated from the EEG. The ADHD group had significantly lower and on average positive BP amplitudes at Cz. In agreement with age-dependent maturation effects the LRP had a positive polarity in both groups, but lower amplitudes were found in the ADHD group without medication. The control group showed a mid-central negativity and a positivity over motor areas contra-lateral to the side of movement, whereas no negativity over Cz and a more diffuse positivity was found in the ADHD group. LRP group differences diminished after MPH administration as indicated by an interaction between group and time of measurement/medication. The cortical motor system shows altered functioning during movement preparation and initiation in children affected by ADHD. Positive Bereitschaftspotential polarities may represent delayed cortical maturation. Group differences of LRP were pharmacologically modulated by the catecholaminergic agent MPH.

Scientific Evidence for the Evaluation of Neurological Soft Signs as Atypical Neurodevelopment Markers in Childhood Neuropsychiatric Disorders

Motor dysfunction is commonly present in children with neurodevelopmental disorders. Developmental changes in voluntary control of motor skills include improvements in speed and motor coordination as well as reduced frequency of neurological soft signs (NSS) that are commonly observed in typically developing younger children. NSS are motor and sensory conditions that cannot be linked to specific cerebral lesions. The persistence of NSS into later childhood and adolescence is linked with an increased risk of psychiatric disorders. This finding gives support to the neurodevelopmental model of NSS in which minor neurological impairments may be viewed as potential signs of deviant brain development and might represent trait markers of vulnerability for neurodevelopmental disorders. Given that NSS are easily detectable, it is important that clinicians increase their knowledge of the clinical presentation and research implications of the relationship between NSS and childhood neurodevelopmental disorders. To the best of our knowledge, this is the first review article to give an updated overview of the current knowledge of NSS in the most common neuropsychiatric disorders of childhood/adolescence, such as attention-deficit/hyperactivity disorder, autism spectrum disorder, obsessive-compulsive disorder, bipolar disorder, and first episode of psychosis. The article also presents key points for future research studies on this topic.