Visual search for feature conjunctions: an fMRI study comparing alcohol-related neurodevelopmental disorder (ARND) to ADHD.
BACKGROUND
Alcohol-related neurodevelopmental disorder (ARND) falls under the umbrella of fetal alcohol spectrum disorder (FASD). Diagnosis of ARND is difficult because individuals do not demonstrate the characteristic facial features associated with fetal alcohol syndrome (FAS). While attentional problems in ARND are similar to those found in attention-deficit/hyperactivity disorder (ADHD), the underlying impairment in attention pathways may be different.


METHODS
Functional magnetic resonance imaging (fMRI) and diffusion tensor imaging (DTI) was conducted at 3 T. Sixty-three children aged 10 to 14 years diagnosed with ARND, ADHD, and typically developing (TD) controls performed a single-feature and a feature-conjunction visual search task.


RESULTS
Dorsal and ventral attention pathways were activated during both attention tasks in all groups. Significantly greater activation was observed in ARND subjects during a single-feature search as compared to TD and ADHD groups, suggesting ARND subjects require greater neural recruitment to perform this simple task. ARND subjects appear unable to effectively use the very efficient automatic perceptual 'pop-out' mechanism employed by TD and ADHD groups during presentation of the disjunction array. By comparison, activation was lower in ARND compared to TD and ADHD subjects during the more difficult conjunction search task as compared to the single-feature search. Analysis of DTI data using tract-based spatial statistics (TBSS) showed areas of significantly lower fractional anisotropy (FA) and higher mean diffusivity (MD) in the right inferior longitudinal fasciculus (ILF) in ARND compared to TD subjects. Damage to the white matter of the ILF may compromise the ventral attention pathway and may require subjects to use the dorsal attention pathway, which is associated with effortful top-down processing, for tasks that should be automatic. Decreased functional activity in the right temporoparietal junction (TPJ) of ARND subjects may be due to a reduction in the white matter tract's ability to efficiently convey information critical to performance of the attention tasks.


CONCLUSIONS
Limited activation patterns in ARND suggest problems in information processing along the ventral frontoparietal attention pathway. Poor integrity of the ILF, which connects the functional components of the ventral attention network, in ARND subjects may contribute to the attention deficits characteristic of the disorder.
Department of Physiology, University of Manitoba, 432 Basic Medical Sciences Bldg, 745 Bannatyne Ave, Winnipeg, MB R3E 0J9 Canada.
Carrie R
CR
O'Conaill
Department of Physiology, University of Manitoba, 432 Basic Medical Sciences Bldg, 745 Bannatyne Ave, Winnipeg, MB R3E 0J9 Canada ; Department of Psychology, University of Manitoba, P404 Duff Roblin Bldg, 190 Dysart Rd, Winnipeg, MB R3T 2N2 Canada ; National Research Council of Canada - Institute for Biodiagnostics, 435 Ellice Avenue, Winnipeg, MB R3T 1Y6 Canada.
Krisztina L
KL
Malisza
Department of Physiology, University of Manitoba, 432 Basic Medical Sciences Bldg, 745 Bannatyne Ave, Winnipeg, MB R3E 0J9 Canada.
Joan L
JL
Buss
Department of Psychology, University of Winnipeg, 515 Portage Ave, Winnipeg, R3B 2E9 Canada.
R Bruce
RB
Bolster
Division of Rehabilitation Psychology, Seattle Children's Hospital, 4800 Sand Point Way, Seattle, WA 98105 USA.
Christine
C
Clancy
National Research Council of Canada - Institute for Biodiagnostics, 435 Ellice Avenue, Winnipeg, MB R3T 1Y6 Canada.
Patricia Dreessen
PD
de Gervai
Department of Paediatrics, University of Manitoba, 336 Basic Medical Sciences Bldg, 745 Bannatyne Ave, Winnipeg, MB R3E OJ9 Canada ; Department of Biochemistry and Medical Genetics, University of Manitoba, 336 Basic Medical Sciences Bldg, 745 Bannatyne Ave, Winnipeg, MB R3E OJ9 Canada.
Albert E
AE
Chudley
Department of Pediatrics and Child Health, CE-203 Children's Hospital, Health Sciences Centre, 840 Sherbrook Street, Winnipeg, MB R3A 1S1 Canada.
Sally
S
Longstaffe
Alcohol-related neurodevelopmental disorder (ARND); Attention; Attention-deficit/hyperactivity disorder (ADHD); Diffusion tensor imaging (DTI); Fetal alcohol spectrum disorder (FASD); Functional magnetic resonance imaging (fMRI); Gray matter; Inferior longitudinal fasciculus (ILF); Tract-based spatial statistics (TBSS); White matter