Logan T. Trujillo

Sleep and sadness: exploring the relation among sleep, cognitive control, and depressive symptoms in young adults.

BACKGROUND Sleep disturbance is a common feature of depression. However, recent work has found that individuals who are vulnerable to depression report poorer sleep quality compared to their low-risk counterparts, suggesting that sleep disturbance may precede depression. In addition, both sleep disturbance and depression are related to deficits in cognitive control processes. Thus we examined if poor sleep quality predicts subsequent increases in depressive symptoms and if levels of cognitive control mediated this relation. METHODS Thirty-five undergraduate students participated in two experimental sessions separated by 3 weeks. Participants wore an actigraph watch between sessions, which provided an objective measure of sleep patterns. We assessed self-reported sleep quality and depressive symptoms at both sessions. Last, individuals completed an exogenous cuing task, which measured ability to disengage attention from neutral and negative stimuli during the second session. RESULTS Using path analyses, we found that both greater self-reported sleep difficulty and more objective sleep stability measures significantly predicted greater difficulty disengaging attention (i.e., less cognitive control) from negative stimuli. Less cognitive control over negative stimuli in turn predicted increased depression symptoms at the second session. Exploratory associations among the circadian locomotor output cycles kaput gene, CLOCK, single nucleotide polymorphism (SNP), rs11932595, as well as sleep assessments and depressive symptoms also are presented. CONCLUSIONS These preliminary results suggest that sleep disruptions may contribute to increases in depressive symptoms via their impact on cognitive control. Further, variation in the CLOCK gene may be associated with sleep quality.

An examination of the association between chronic sleep restriction and electrocortical arousal in college students

OBJECTIVE The deleterious neurocognitive effects of laboratory-controlled short-term sleep deprivation are well-known. The present study investigated neurocognitive changes arising from chronic sleep restriction outside the laboratory. METHODS Sleep patterns of 24 undergraduates were tracked via actigraphy across a 15-week semester. At the semester beginning, at a midpoint, and a week before finals, students performed the Psychomotor Vigilance Test (PVT) and cortical arousal was measured via event-related potentials (ERP) and resting state electroencephalography (EEG). RESULTS Average daily sleep decreased between Session 1 and Sessions 2 and 3. Calculated circadian rhythm measures indicated nighttime movement increased and sleep quality decreased from Sessions 1 and 2 to Session 3. Parallel to the sleep/activity measures, PVT reaction time increased between Session 1 and Sessions 2 and 3 and resting state alpha EEG reactivity magnitude and PVT-evoked P3 ERP amplitude decreased between Session 1 and Sessions 2 and 3. Cross-sectional regressions showed PVT reaction time was negatively associated with average daily sleep, alpha reactivity, and P3 changes; sleep/circadian measures were associated with alpha reactivity and/or P3 changes. CONCLUSIONS Small, but persistent sleep deficits reduced cortical arousal and impaired vigilant attention. SIGNIFICANCE Chronic sleep restriction impacts neurocognition in a manner similar to laboratory controlled sleep deprivation.

Neurobehavioral correlates of the rapid formation of the symbolic control of visuospatial attention

Prior research suggests that nonpredictive symbolic central cues can produce nonvoluntary shifts of endogenous attention when associations between cues and spatial locations are overlearned during cognitive development. The present ERP study extends this research by first showing that overlearned cue-spatial location associations necessary to support nonvoluntary attentional orienting can be rapidly formed in adult humans. A second experiment indicates that the nonvoluntary orienting formed by such rapid learning is semireflexive (amenable to top-down influence) rather than reflexive (resistant to top-down influence). A third experiment suggests that the rapid formation of endogenous nonvoluntary orienting requires explicit rather than implicit learning of cue-location associations. These findings provide further support for a strong connection between neurocognitive representations of space, symbol meaning, and attentional control.

Licensing Novel Role-Governed Categories: An ERP Analysis

Markman and Stilwell (2001) argued that many natural categories name roles in relational systems, and so they are role-governed categories. This view predicts instantiating a novel relational structure licenses the creation of novel role-governed categories. This paper supports this claim and helps to specify the mechanisms underlying this licensing. Event-related potentials were recorded while participants read passages of text. Participants instantiated novel relational representations by interpreting novel verbs derived from nouns during reading. Sentences later, comprehension of novel role terms derived from the novel verb was facilitated relative to a control condition where the novel verb was paraphrased using the root noun in its familiar form. This comprehension facilitation was marked by a reduced negativity elicited from the role term in the Novel Verb condition relative to the Paraphrase from 400 to 500 ms post-stimulus-onset. This relative difference in negativity is consistent with both the N400, which is a marker of semantic integration, and the Nref effect, which reflects the working memory load required to resolve reference. Additionally, because this increased negativity persisted until 670 ms post-stimulus-onset, and not that the Paraphrase condition elicited an increased positivity (i.e., the P600), we ruled out that the licensing effect is rooted in morphosyntactic processes.

Electrophysiological evidence for early access to object memories during figure assignment in humans

During figure assignment configural cues (e.g., area, closure, convexity, symmetry) along the same side of a contour cooperate in assigning that side figural status; cues across a contour compete. Here we report human electrophysiological evidence that object memories play a role in figure assignment. We created silhouettes in which the cue balance along the bounding contour biased the inner region to be seen as figure; the inner regions portrayed novel shapes. Control silhouettes suggested novel shapes on the outside of their edges as well as on the inside. Experimental silhouettes suggested familiar objects on the outside, which nonetheless appeared as shapeless grounds. Electroencephalographic (EEG) activity was recorded from 29 scalp sites while the observers viewed experimental and control silhouettes for 50 ms in the context of a cover task in which they categorized line drawings of familiar and novel objects shown 500 ms after the silhouettes. Event-related potentials (ERPs) were created by averaging the EEG traces across trials with respect to the onset of the silhouettes. The P100 component of the ERP was smaller for experimental than for control silhouettes. This difference was maximal over midline occipital, and right hemisphere occipital and parietal-occipital sites (ps < 0.05). The differential P100 responses may reflect either 1) access to object memories, which occurs on the outside of the experimental, but not the control, silhouettes during cross-contour competition; or 2) the inhibition of the object memories by cues on the side of the contour ultimately seen as figure. Thus, object memory influences are evident in the first 100 ms of processing the silhouettes, even though the familiar objects in the grounds were not perceived consciously. Physiological data obtained in monkey V1 by other investigators follows a similar time course. Results are discussed within the context of models of figure-ground assignment and shape perception.