Abstract
BackgroundShort-term and working memory (STM and WM) deficits have been demonstrated in individuals with autism spectrum disorder (ASD) and may emerge through atypical functional activity and connectivity of the frontoparietal network, which exerts top-down control necessary for successful STM and WM processes. Little is known regarding the spectral properties of the frontoparietal network during STM or WM processes in ASD, although certain neural frequencies have been linked to specific neural mechanisms.MethodsWe analysed magnetoencephalographic data from 39 control adults (26 males; 27.15 ± 5.91 years old) and 40 adults with ASD (26 males; 27.17 ± 6.27 years old) during a 1-back condition (STM) of an n-back task, and from a subset of this sample during a 2-back condition (WM). We performed seed-based connectivity analyses using regions of the frontoparietal network. Interregional synchrony in theta, alpha, and beta bands was assessed with the phase difference derivative and compared between groups during periods of maintenance and recognition.ResultsDuring maintenance of newly presented vs. repeated stimuli, the two groups did not differ significantly in theta, alpha, or beta phase synchrony for either condition. Adults with ASD showed alpha-band synchrony in a network containing the right dorsolateral prefrontal cortex, bilateral inferior parietal lobules (IPL), and precuneus in both 1- and 2-back tasks, whereas controls demonstrated alpha-band synchrony in a sparser set of regions, including the left insula and IPL, in only the 1-back task. During recognition of repeated vs. newly presented stimuli, adults with ASD exhibited decreased theta-band connectivity compared to controls in a network with hubs in the right inferior frontal gyrus and left IPL in the 1-back condition. Whilst there were no group differences in connectivity in the 2-back condition, adults with ASD showed no frontoparietal network recruitment during recognition, whilst controls activated networks in the theta and beta bands.ConclusionsOur findings suggest that since adults with ASD performed well on the n-back task, their appropriate, but effortful recruitment of alpha-band mechanisms in the frontoparietal network to maintain items in STM and WM may compensate for atypical modulation of this network in the theta band to recognise previously presented items in STM.
Highlights
Adults with autism spectrum disorder (ASD) demonstrate difficulties with a variety of executive functions [1,2,3,4], one of which is working memory (WM), which refers to the ability to hold and manipulate information in mind [5, 6]
Brain-Behaviour Relations We explored whether mean network connectivity in any of our group comparisons was associated with WM abilities as measured by the BRIEF-A, task performance, and with ASD symptom severity
Taking into account that decreased connectivity has been observed in fMRI in ASD during other n-back tasks [25, 29, 31], our findings in the 1-back condition substantiate reports of longrange underconnectivity in ASD [72, 74, 197,198,199]. The specificity of this difference to the theta band is in line with prior work emphasising the role of theta oscillations in short-term memory (STM) [39, 82, 84] and recognition/retrieval [196, 200,201,202]. This result is in contrast to our previous work [32], where we found that these differences occurred in the alpha band during recognition of repeated visual stimuli in a WM task
Summary
Adults with autism spectrum disorder (ASD) demonstrate difficulties with a variety of executive functions [1,2,3,4], one of which is working memory (WM), which refers to the ability to hold and manipulate information in mind [5, 6]. Much of the STM and WM literature in ASD has utilised paradigms tapping both maintenance and recognition processes; during such tasks, individuals with ASD show differential activation of this frontoparietal network across development, exhibiting increased activity in the dlPFC during childhood [27, 61], but the opposite in adulthood [26, 31, 62]. They show poor modulation of these frontoparietal regions with increasing cognitive load [30, 63, 64]. Little is known regarding the spectral properties of the frontoparietal network during STM or WM processes in ASD, certain neural frequencies have been linked to specific neural mechanisms
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