The Development of Cognitive Function in Tourette Syndrome: fMRI Studies

Lay Summary

Using Imaging to Explore the Basis of Some Developmental Disorders

Tourette Syndrome is a rare but socially devastating developmental disorder, in which affected children impulsively have inappropriate actions, such as blurting out swear words. Understanding how to treat developmental conditions requires that we gain an understanding of how normal cognitive development occurs and how this is altered in various disease states.

The researchers hypothesize that some developmental disorders such as Tourette Syndrome are associated with faulty cognitive control processes in certain brain regions. The investigators further hypothesize that in healthy children both “brain-state” activities (such as recalling memories) and “item-specific” activities (such as recalling a specific memory) are tied to cognitive control, while in children with Tourette Syndrome, control is tied only to brain-state activities.  They will use fMRI to explore these hypotheses.

Abstract

The Development of Cognitive Function in Tourette Syndrome: fMRI Studies

Cognitive control generally refers to putative brain processes that serve to link or unify the functions of anatomically distinct cognitive modules (Posner 1978). Little is known about the functional neuroanatomy of cognitive control in children. Abnormal cognitive control has substantial clinical relevance. Common pediatric neuropsychiatric disorders are thought to be due, in part, to dysfunction of control. For example, Tourette Syndrome (TS), a genetic neurological disorder with pediatric onset manifest as chronic tics, is associated with impulsivity and aberrant cognitive control. To understand the functional neuroanatomy that underlies the executive dysfunction in TS, further information about the normal development of control processes needs to be obtained.

This proposal has two major components. First, it addresses a previously unexplored aspect of cognitive development: the timing, location, and pattern of brain regions involved in cognitive control through the use of recently-developed mixed state/item fMRI designs (Donaldson et al. 2001). Brain regions performing cognitive functions can be thought to have both sustained and transient activity, reflecting state- and item-related processing, respectively. Here, “state” refers to a task mode (e.g., the state of recalling memories) and “item” refers to a particular event (recalling a specific memory). If control is intimately linked to the establishment of a brain-state, then brain regions serving cognitive control may well demonstrate sustained activity during task performance and show state-related interaction effects on item activity.

Second, this proposal applies the context afforded by our studies on normal subjects to a population of patients (TS) with suspected executive dysfunction. To date, no published study using functional neuroimaging has explored, across development, the functional neuroanatomy of cognitive control in TS or in any other condition attributable to executive dysfunction. We hypothesize that compared to normal subjects, those with a disorder of cognitive control will demonstrate differential involvement of both state- and item-related activity in the frontal cortex, a brain region widely implicated in cognitive control.