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  • Frontoparietal and Cingulo-opercular Networks Play Dissociable Roles in Control of Working Memory.

    24 October 2018

    We used magnetoencephalography to characterize the spatiotemporal dynamics of cortical activity during top-down control of working memory (WM). fMRI studies have previously implicated both the frontoparietal and cingulo-opercular networks in control over WM, but their respective contributions are unclear. In our task, spatial cues indicating the relevant item in a WM array occurred either before the memory array or during the maintenance period, providing a direct comparison between prospective and retrospective control of WM. We found that in both cases a frontoparietal network activated following the cue, but following retrocues this activation was transient and was succeeded by a cingulo-opercular network activation. We also characterized the time course of top-down modulation of alpha activity in visual/parietal cortex. This modulation was transient following retrocues, occurring in parallel with the frontoparietal network activation. We suggest that the frontoparietal network is responsible for top-down modulation of activity in sensory cortex during both preparatory attention and orienting within memory. In contrast, the cingulo-opercular network plays a more downstream role in cognitive control, perhaps associated with output gating of memory.

  • Reward boosts working memory encoding over a brief temporal window

    24 October 2018

    © 2015 Taylor & Francis Selection mechanisms for WM are ordinarily studied by explicitly cueing a subset of memory items. However, we might also expect the reward associations of stimuli we encounter to modulate their probability of being represented in working memory (WM). Theoretical and computational models explicitly predict that reward value should determine which items will be gated into WM. For example, a model by Braver and colleagues in which phasic dopamine signalling gates WM updating predicts a temporally-specific but not item-specific reward-driven boost to encoding. In contrast, Hazy and colleagues invoke reinforcement learning in cortico-striatal loops and predict an item-wise reward-driven encoding bias. Furthermore, a body of prior work has demonstrated that reward-associated items can capture attention, and it has been shown that attentional capture biases WM encoding. We directly investigated the relationship between reward history and WM encoding. In our first experiment, we found an encoding benefit associated with reward-associated items, but the benefit generalized to all items in the memory array. In a second experiment this effect was shown to be highly temporally specific. We speculate that in real-world contexts in which the environment is sampled sequentially with saccades/shifts in attention, this mechanism could effectively mediate an item-wise encoding bias, because encoding boosts would occur when rewarded items were fixated.

  • Modulation of alpha power at encoding and retrieval tracks the precision of visual short-term memory.

    24 October 2018

    Our ability to hold information in mind is strictly limited. We sought to understand the relationship between oscillatory brain activity and the allocation of resources within visual short-term memory (VSTM). Participants attempted to remember target arrows embedded among distracters and used a continuous method of responding to report their memory for a cued target item. Trial-to-trial variability in the absolute circular accuracy with which participants could report the target was predicted by event-related alpha synchronization during initial processing of the memoranda and by alpha desynchronization during the retrieval of those items from VSTM. Using a model-based approach, we were also able to explore further which parameters of VSTM-guided behavior were most influenced by alpha band changes. Alpha synchronization during item processing enhanced the precision with which an item could be retained without affecting the likelihood of an item being represented per se (as indexed by the guessing rate). Importantly, our data outline a neural mechanism that mirrors the precision with which items are retained; the greater the alpha power enhancement during encoding, the greater the precision with which that item can be retained.

  • Psychometric properties of Glasgow Sleep Effort Scale in Portuguese language.

    24 October 2018

    Sleep effort is generally defined as the attempt to force and induce sleep in a voluntary manner. This study aimed to document the psychometric properties of a brief measure of sleep effort--the Glasgow Sleep Effort Scale--in its European (Portuguese) version using a large sample (N = 2,995). The results supported the good internal consistency of the overall scale scores (α = .79). Potential construct validity was evaluated with various methods, including criterion validity. There was also a convergent validity indicator. Principal components analysis revealed a 1-dimensional structure that accounted for 45% of the total variance. This preliminary study suggests that this Portuguese version of the Glasgow Sleep Effort Scale is a measure of sleep behavior suitable for research and clinical purposes. However, more studies are needed, particularly with clinical groups.

  • Psychological Effect of an Analogue Traumatic Event Reduced by Sleep Deprivation.

    24 October 2018

    STUDY OBJECTIVE: To examine the effect of sleep deprivation compared to sleep, immediately after experimental trauma stimuli on the development of intrusive memories to that trauma stimuli. DESIGN: Participants were exposed to a film with traumatic content (trauma film). The immediate response to the trauma film was assessed, followed by either total sleep deprivation (sleep deprived group, N = 20) or sleep as usual (sleep group, N = 22). Twelve hours after the film viewing the initial psychological effect of the trauma film was measured and for the subsequent 6 days intrusive emotional memories related to the trauma film were recorded in daily life. SETTING: Academic sleep laboratory and participants' home environment. PARTICIPANTS: Healthy paid volunteers. MEASUREMENTS AND RESULTS: On the first day after the trauma film, the psychological effect as assessed by the Impact of Event Scale - Revised was lower in the sleep deprived group compared to the sleep group. In addition, the sleep deprived group reported fewer intrusive emotional memories (mean 2.28, standard deviation [SD] 2.91) compared to the sleep group (mean 3.76, SD 3.35). Because habitual sleep/circadian patterns, psychological health, and immediate effect of the trauma film were similar at baseline for participants of both groups, the results cannot be accounted for by pre-existing inequalities between groups. CONCLUSIONS: Our findings suggest that sleep deprivation on one night, rather than sleeping, reduces emotional effect and intrusive memories following exposure to experimental trauma.

  • Does Infant Reactivity Moderate the Association Between Antenatal Maternal Depression and Infant Sleep?

    24 October 2018

    OBJECTIVE: A number of studies have established an association between antenatal maternal depression and infant sleep. One key question is whether all infants are equally susceptible to environmental influences, including the intrauterine environment. Reactive temperament has been examined as a plasticity factor, with accumulating evidence suggesting that infants with reactive temperament may be more susceptible to both positive and negative environmental influences. This study examines whether infant reactivity moderates any association between antenatal depression and infant sleep in 2 longitudinal studies: the Avon Longitudinal Study of Parents and Children (ALSPAC) and Generation R cohorts. METHODS: Maternal depression scores were assessed during pregnancy using Edinburgh Postnatal Depression Scale and Brief Symptom Inventory. Infant sleep duration and awakenings, in ALSPAC (N = 8318) and Generation R (N = 2241), were assessed at 18 and 24 months of age, respectively. Infant reactivity was assessed by temperament questionnaire at 6 months of age. RESULTS: Hierarchical linear regression models indicated a 3-way interaction between reactivity and gender moderating the effect of antenatal depression on infant sleep, on sleep duration in Generation R at 24 months (β = .085, p < .001) in the whole sample and when limited to the Dutch/European group (β = .055, p = .030), and on night awakenings at 18 months in ALSPAC (β = -.085, p = .013). Boys with more reactive temperament exhibited shorter sleep duration and a higher number of awakenings when previously exposed to maternal symptoms of antenatal depression. CONCLUSION: For the first time, these findings highlight, in 2 large cohorts, that children with temperamental reactivity may be more vulnerable to antenatal depression, raising the possibility of targeted interventions to improve infant outcomes.

  • Functional Defects in Color Vision in Patients With Choroideremia.

    24 October 2018

    PURPOSE: To characterize defects in color vision in patients with choroideremia. DESIGN: Prospective cohort study. METHODS: Thirty patients with choroideremia (41 eyes) and 10 age-matched male controls (19 eyes) with visual acuity of ≥6/36 attending outpatient clinics in Oxford Eye Hospital underwent color vision testing with the Farnsworth-Munsell 100 hue test, visual acuity testing, and autofluorescence imaging. To exclude changes caused by degeneration of the fovea, a subgroup of 14 patients with a visual acuity ≥6/6 was analyzed. Calculated color vision total error scores were compared between the groups and related to a range of factors using a random-effects model. RESULTS: Mean color vision total error scores were 120 (95% confidence interval [CI] 92, 156) in the ≥6/6 choroideremia group, 206 (95% CI 161, 266) in the <6/6 visual acuity choroideremia group, and 47 (95% CI 32, 69) in the control group. Covariate analysis showed a significant difference in color vision total error score between the groups (P < .001 between each group). CONCLUSIONS: Patients with choroideremia have a functional defect in color vision compared with age-matched controls. The color vision defect deteriorates as the degeneration encroaches on the fovea. The presence of an early functional defect in color vision provides a useful biomarker against which to assess successful gene transfer in gene therapy trials.

  • Crosstalk between the nociceptive and immune systems in host defence and disease.

    24 October 2018

    Nociceptors and immune cells both protect the host from potential threats to homeostasis. There is growing evidence for bidirectional signalling between these two systems, and the underlying mechanisms are beginning to be elucidated. An understanding is emerging of how both the adaptive and innate immune systems can activate and sensitize nociceptors, and, reciprocally, how nociceptors modulate immune cells. In this Review, we discuss how these interactions can be adaptive and useful to the organism but also consider when such signalling might be maladaptive and pathophysiological, contributing to immune-mediated diseases and persistent pain states.