Visual search for feature conjunctions: an fMRI study comparing alcohol-related neurodevelopmental disorder (ARND) to ADHD

Abstract

BackgroundAlcohol-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.MethodsFunctional 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.ResultsDorsal 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.ConclusionsLimited 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.

Altered functional connectivity during spatial working memory in children with heavy prenatal alcohol exposure

“…They may, in turn, have necessitated increased recruitment of visual processing regions to complete the task. Other studies also support the possibility that SWM deficits in FASD may be secondary to visual processing, which is consistent with alterations in the bottom-up processing in children with ARND suggested by O’Conaill et al (2015). For example, a study by Malisza et al (2012) found decreased occipital activation during a 0-back task in children with ARND relative to controls, indicating inefficient visual processing pathways or compromised visual attention in the ARND group.…”

Radiological studies of fetal alcohol spectrum disorders in humans and animal models: An updated comprehensive review

“…distractors whose color and shape were identical and different from the target's), adolescents with ARDN had much more extensive activations in the dorsal frontoparietal network, which included the attention pathways, compared to the controls. Yet, when the search task became more complicated with the distractors either having the same color or shape as the target's, subjects with ARND showed only a small change in activation from the simpler task, while healthy subjects exhibited a substantial increase in cortical activation in the frontal, parietal, temporal and lateral occipital regions [76].…”

“…18 appeared alone then in an array [76]. In a simple search task where the target character reappeared together with three other characters (i.e.…”

“…In children and young adults with FASD, higher MD was seen in the bilateral inferior frontooccipital fasciculi, SLF, left ILF, corticospinal tracts, globus pallidus, right putamen and right thalamus [74][75][76]; left superior frontal lobe and anterior limb of the internal capsule [73]; the splenium [74;81], isthmus [74;82] and whole corpus callosum [70;76]; the left middle and right inferior peduncles [79]; the cingulate, external capsule, uncinate fasciculus, superior corona radiate, arcuate fasciculus, frontal, fronto-central and central association fibers [76]; and the cingulum bundles that connect the medial prefrontal cortex and the posterior cingulate cortex [78]. Less commonly, lower MD was observed in the genu of corpus callosum [75], the right inferior frontal lobe and the right temporo-parieto-occipital junction [73].…”

“…Children and young adults with FASD also exhibited lower FA in the right cingulum, bilateral inferior and superior longitudinal fasciculi (ILF and SLF respectively) and left thalamus [74][75][76]; the frontal, parietal and occipital lobes [73;77]; the medial prefrontal cortex and posterior cingulate cortex [78];…”