Aberrant neural mediation of verbal fluency in autism spectrum disorders.
OBJECTIVE
Contrasts of verbal fluency and automatic speech provide an opportunity to evaluate the neural underpinnings of generativity and flexibility in autism spectrum disorders (ASD).


METHODS
We used functional magnetic resonance imaging (fMRI) to contrast brain activity in high functioning ASD (n=17, mean verbal IQ=117) and neurotypical (NT; n=20, mean verbal IQ=112) adolescent and young adult males (12-23years). Participants responded to three word generation conditions: automatic speech (reciting months), category fluency, and letter fluency.


RESULTS
Our paradigm closely mirrored behavioral fluency tasks by requiring overt, free recall word generation while controlling for differences in verbal output between the groups and systematically increasing the task demand. The ASD group showed reduced neural response compared to the NT participants during fluency tasks in multiple regions of left anterior and posterior cortices, and sub-cortical structures. Six of these regions fell in cortico-striatal circuits previously linked to repetitive behaviors (Langen, Durston, Kas, van Engeland, & Staal, 2011), and activity in two of them (putamen and thalamus) was negatively correlated with autism repetitive behavior symptoms in the ASD group. In addition, response in left inferior frontal gyrus was differentially modulated in the ASD, relative to the NT, group as a function of task demand.


CONCLUSIONS
These data indicate a specific, atypical brain response in ASD to demanding generativity tasks that may have relevance to repetitive behavior symptoms in ASD as well as to difficulties generating original verbal responses.
Laboratory of Brain and Cognition, National Institute of Mental Health, 10 Center Drive, Room 4C104, MSC 1366, Bethesda, MD 20892-1366, USA; Center for Autism Spectrum Disorders, Children's National Medical Center, 15245 Shady Grove Road, Suite 350, Rockville, MD 20850, USA. Electronic address: lkenwort@cnmc.org.
Lauren
L
Kenworthy
Gregory L
GL
Wallace
Rasmus
R
Birn
Shawn C
SC
Milleville
Laura K
LK
Case
Peter A
PA
Bandettini
Alex
A
Martin
D000293:Adolescent; D001921:Brain / Q000503:physiopathology*; D001931:Brain Mapping; D002648:Child; D002659:Child Development Disorders, Pervasive / Q000503:physiopathology*; D056344:Executive Function / Q000502:physiology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D014705:Verbal Behavior / Q000502:physiology*; D055815:Young Adult
Autism; Executive function; Left inferior frontal gyrus; Verbal fluency; fMRI