Working memory in wayfinding-a dual task experiment in a virtual city

This study examines the working memory systems involved in human wayfinding. In the learning phase, 24 participants learned two routes in a novel photorealistic virtual environment displayed on a 220° screen while they were disrupted by a visual, a spatial, a verbal, or—in a control group—no secondary task. In the following wayfinding phase, the participants had to find and to "virtually walk" the two routes again. During this wayfinding phase, a number of dependent measures were recorded. This research shows that encoding wayfinding knowledge interfered with the verbal and with the spatial secondary task. These interferences were even stronger than the interference of wayfinding knowledge with the visual secondary task. These findings are consistent with a dual-coding approach of wayfinding knowledge.     

Severity of dysfluency correlates with basal ganglia activity in persistent developmental stuttering

Previous studies suggest that anatomical anomalies [Foundas, A. L., Bollich, A. M., Corey, D. M., Hurley, M., & Heilman, K. M. (2001). Anomalous anatomy of speech-language areas in adults with persistent developmental stuttering. Neurology, 57, 207-215; Foundas, A. L., Corey, D. M., Angeles, V., Bollich, A. M., Crabtree-Hartman, E., & Heilman, K. M. (2003). Atypical cerebral laterality in adults with persistent developmental stuttering. Neurology, 61, 1378-1385; Foundas, A. L., Bollich, A. M., Feldman, J., Corey, D. M., Hurley, M., & Lemen, L. C. et al., (2004). Aberrant auditory processing and atypical planum temporale in developmental stuttering. Neurology, 63, 1640-1646; Jancke, L., Hanggi, J., & Steinmetz, H. (2004). Morphological brain differences between adult stutterers and non-stutterers. BMC Neurology, 4, 23], in particular a reduction of the white matter anisotropy underlying the left sensorimotor cortex [Sommer, M., Koch, M. A., Paulus, W., Weiller, C., & Buchel, C. (2002). Disconnection of speech-relevant brain areas in persistent developmental stuttering. Lancet, 360, 380-383] could be at the origin of persistent developmental stuttering (PDS). Because neural connections between the motor cortex and basal ganglia are implicated in speech motor functions, PDS could also be associated with a dysfunction in basal ganglia activity [Alm, P. (2004). Stuttering and the basal ganglia circuits: a critical review of possible relations. Journal of Communication Disorders, 37, 325-369]. This fMRI study reports a correlation between severity of stuttering and activity in the basal ganglia and shows that this activity is modified by fluency shaping therapy through long-term therapy effects that reflect speech production improvement. A model of dysfunction in stuttering and possible repair modes is proposed that accommodates the data presented here and observations previously made by us and by others.     

Transcranial magnetic stimulation in child psychiatry: disturbed motor system excitability in hypermotoric syndromes

Normal development and dysfunctions of motor system excitability can be investigated in vivo by means of single‐ and paired‐pulse transcranial magnetic stimulation (TMS). While different TMS‐parameters show different developmental time courses between 8 and 16 years of age, distinct dysfunctional patterns of motor system excitability can be demonstrated in child psychiatric disorders with hypermotoric behavior: in tic disorder, a shortened cortical silent period can be stated providing evidence for deficient inhibitory mechanisms within the sensorimotor loop, probably primarily at the level of the basal ganglia. In attention deficit hyperactivity disorder (ADHD), a decreased intracortical inhibition indicates deficient inhibitory mechanisms within the motor cortex (but enhancement of intracortical inhibition after oral intake of 10 mg methylphenidate). In children with comorbid ADHD and tic disorder, the findings of a reduced intracortical inhibition as well as a shortened cortical silent period provide evidence for additive effects at the level of motor system excitability. Thus, TMS allows us to obtain substantial insight into both the normal development and the neurobiological basis of hypermotoric syndromes in child psychiatry.     

Prevalence and functions of stereotyped behaviors in nonhandicapped children in residential care

Caregivers in nine residential care institutions rated the occurrence of 15 stereotyped behaviors in 142 nonhandicapped children aged from 10 months to 11 years. The frequency and duration of each stereotypy as well as the typical situations in which it occurred were assessed. The most frequent stereotypies were thumbsucking, hair twisting, and body rocking in infants and young children; thumbsucking and making faces in preschool-age children; and nail biting/chewing in school-age children. Boys exhibited stereotypies more frequently than girls, and children with a suspected history of child abuse more frequently than other children. Typical situations for stereotypies could be classified to four types: concentration/demand, arousal/frustration, boredom/monotony, and stimulation/distraction. Nail biting/chewing and lip biting occurred predominantly in concentration/demand; thumbsucking and hair twisting in boredom/monotony; and pulling faces and scratching oneself in arousal/frustration and concentration/demand situations. These results provide preliminary indications regarding the different functions of individual stereotypies.The author would like to thank Jonathan Harrow (University of Bielefeld) for translating this paper from German into English.