Abstract
Fetal alcohol spectrum disorder (FASD) is characterized by a broad range of behavioral and cognitive deficits that impact the long-term quality of life for affected individuals. However, the underlying changes in brain structure and function associated with these cognitive impairments are not well-understood. Previous studies identified deficits in behavioral performance of prosaccade tasks in children with FASD. In this study, we investigated group differences in gamma oscillations during performance of a prosaccade task. We collected magnetoencephalography (MEG) data from 15 adolescents with FASD and 20 age-matched healthy controls (HC) with a mean age of 15.9 ± 0.4 years during performance of a prosaccade task. Eye movement was recorded and synchronized to the MEG data using an MEG compatible eye-tracker. The MEG data were analyzed relative to the onset of the visual saccade. Time-frequency analysis was performed using Fieldtrip with a focus on group differences in gamma-band oscillations. Following left target presentation, we identified four clusters over right frontal, right parietal, and left temporal/occipital cortex, with significantly different gamma-band (30–50 Hz) power between FASD and HC. Furthermore, visual M100 latencies described in Coffman etal. (2012) corresponded with increased gamma power over right central cortex in FASD only. Gamma-band differences were not identified for stimulus-averaged responses implying that these gamma-band differences were related to differences in saccade network functioning. These differences in gamma-band power may provide indications of atypical development of cortical networks in individuals with FASD.
Highlights
Basic animal research and human behavioral and neuroimaging studies have contributed substantially to our understanding of the cortical networks involved in visual saccades (Goldberg et al, 2002; Pierrot-Deseilligny et al, 2002; Zhang and Barash, 2004; McDowell et al, 2008)
Further manipulations of the relative timing of the fixation and target stimuli can facilitate saccadic reaction times [Saccadic Reaction Times (SRT); e.g., providing a “gap” between the offset of the fixation and onset of the target stimulus – (Taylor et al, 1999; Dafoe et al, 2007)] and this additional time available for motor planning is associated with increased activity in FEF as demonstrated by functional magnetic resonance imaging
Reynolds and colleagues (Green et al, 2007, 2009, 2013; Paolozza et al, 2013) identified deficits in both prosaccade and anti-saccade tasks in children with Fetal alcohol spectrum disorder (FASD) relative to age-matched controls. These results provide evidence of delayed SRT (Green et al, 2007), differences in measures of fractional anisotropy within white matter tracts that correlate with SRT (Green et al, 2013), and larger variability in saccade accuracy in children with FASD relative to healthy controls (HC; Paolozza et al, 2013)
Summary
Basic animal research and human behavioral and neuroimaging studies have contributed substantially to our understanding of the cortical networks involved in visual saccades (Goldberg et al, 2002; Pierrot-Deseilligny et al, 2002; Zhang and Barash, 2004; McDowell et al, 2008). The cortical network includes primary visual cortex, parietal eye fields, putatively located in medial intraparietal sulcus in humans, and supplementary and frontal eye fields (SEF and FEF; Clementz et al, 2001; Brown et al, 2006; Manoach et al, 2007; McDowell et al, 2008) These areas are differentially activated based on the nature of the saccade experiment: whether it involves prosaccades, including exogenous initiation of the visual saccade, or anti-saccades, where the response to the exogenous stimulus must be inhibited and an endogenous initiation of the saccade away from the target must be accomplished. The exogenously initiated prosaccade task invokes the fronto-parietal saccadic network (e.g., Brown et al, 2006) and is less cognitively demanding than endogenous saccade tasks allowing investigators to assess the viability of the fronto-parietal saccade network in children
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