One size fits null: attentional brain responses differ depending on insomnia subtype

Abstract

Study objectives: Event-related potential (ERP) studies on attentional brain processes in insomnia disorder (ID) have yielded inconsistent findings. Such inconsistencies may relate to small sample sizes, limited corrections for multiple comparisons, and the possibility of heterogeneity within the clinical population. We aimed to overcome these limitations by studying ERP responses both across and within subtypes in a larger sample of ID.

Methods: ERPs were recorded in 201 participants with ID and 70 normal sleeper controls (NS) with an auditory oddball task. Participants with ID were subtyped using a validated multivariate trait profile. Analyses evaluated subtype-specific and nonspecific deviations using both conventional ERP components as well as cluster-based permutation tests.

Results: All five subtypes were well-represented in the ID sample (subtypes 1-5 respectively N = 31, 83, 28, 29 and 19). ERP component analyses with false discovery rate corrections revealed no evidence for differences between the heterogeneous ID group and NS. However, subtype-specific analyses revealed that ERPs were significantly altered, but in different ways for different subtypes. Specifically, ERP component analyses revealed stronger N100 amplitudes for standards and deviants both in subtypes 2 and 3, and a lower P300 amplitude and longer P300 latency for deviants in subtype 3. Cluster-based permutation tests on ERPs corroborated the P300 amplitude effect for deviants in subtype 3, with subtype 3 and 4 additionally showing a smaller difference between deviant and standard P300 amplitudes.

Conclusion: Our findings indicate that ID is a heterogeneous disorder. Ignoring subtype identity dilutes ERP alterations occurring only in specific insomnia subtypes.

Keywords: auditory oddball; event-related potentials; insomnia disorder; insomnia subtypes.

Graphical Abstract

Figure 1.

Grand average ERPs at Fz, Cz, and Pz to standard and deviant stimuli in ID group and NS, and five insomnia subtypes.

Figure 2.

Cluster-based permutation tests to compare the ERPs both in stimulus type and group conditions. Shaded colors indicate time windows with significantly higher (orange) or lower (blue) voltage. (A) In deviants contrasted with standards in ID group (left) and NS (right). Two negative clusters and one positive cluster were observed in ID group (negative cluster 1: p = .003, from 100 to 244 ms, 11 channels; positive cluster 1: p = .001, from 252-884 ms, 11 channels; negative cluster 2: p = .003, from 468 to 1000 ms, 5 channels). One positive cluster was observed in NS (p = .001, from 240 to 912 ms, 11 channels). (B) In ID contrasted with NS in standard condition (left), deviant condition (middle), and deviant-standard difference condition (right).

Figure 3.

Cluster-based permutation tests to compare the ERPs of subtype 3, subtype 4, and NS in different stimulus-type conditions. Shaded colors indicate time windows with significantly lower (blue) voltage. (A) In subtype 3 contrasted with NS in standard (left), deviant (middle), and deviant-standard difference (right) conditions. One negative cluster was observed in deviant condition (p = .006, from 232 to 432 ms, 11 channels). One negative cluster was observed in the deviant-standard difference condition (p = .009, from 284 to 432 ms, 11 channels). (B) In subtype 4 contrasted with NS in standard (left), deviant (middle) and deviant-standard difference (right) conditions. One negative cluster was observed in deviant-standard difference condition (p = .001, from 256 to 452 ms, 11 channels). (C) In subtype 3 contrasted with subtype 4 in standard (left), deviant (middle) and deviant-standard difference (right) conditions. Two negative clusters were observed in standard condition (negative cluster 1: p = .02, from 108 to 360 ms, 11 channels; negative cluster 2: p = .01, from 372 to 844 ms, 11 channels).