Hippocampal Attractor Dynamics Predict Memory-Based Decision Making.

Memories are thought to be retrieved by attractor dynamics if a given input is sufficiently similar to a stored attractor state [1-5]. The hippocampus, a region crucial for spatial navigation [6-12] and episodic memory [13-18], has been associated with attractor-based computations [5, 9], receiving support from the way rodent place cells "remap" nonlinearly between spatial representations [19-22]. In humans, nonlinear response patterns have been reported in perceptual categorization tasks [23-25]; however, it remains elusive whether human memory retrieval is driven by attractor dynamics and what neural mechanisms might underpin them. To test this, we used a virtual reality [7, 11, 26-28] task where participants learned object-location associations within two distinct virtual reality environments. Participants were subsequently exposed to four novel intermediate environments, generated by linearly morphing the background landscapes of the familiar environments, while tracking fMRI activity. We show that linear changes in environmental context cause linear changes in activity patterns in sensory cortex but cause dynamic, nonlinear changes in both hippocampal activity pattern and remembered locations. Furthermore, the sigmoidal response in the hippocampus scaled with the strength of the sigmoidal pattern in spatial memory. These results indicate that mnemonic decisions in an ambiguous novel context relate to putative attractor dynamics in the hippocampus, which support the dynamic remapping of memories.

Can labour contract differences in health and work-related attitudes be explained by quality of working life and job insecurity?

STUDY AIM: We hypothesise that due to a lower quality of working life and higher job insecurity, the health and work-related attitudes of temporary workers may be less positive compared to permanent workers. Therefore, we aimed to (1) examine differences between contract groups (i.e. permanent contract, temporary contract with prospect of permanent work, fixed-term contract, temporary agency contract and on-call contract) in the quality of working life, job insecurity, health and work-related attitudes and (2) investigate whether these latter contract group differences in health and work-related attitudes can be explained by differences in the quality of working life and/or job insecurity. METHODS: Data were collected from the Netherlands Working Conditions Survey 2008 (N = 21,639), and Hypotheses were tested using analysis of variance and cross-table analysis. RESULTS: Temporary work was associated with fewer task demands and lower autonomy and was more often passive or high-strain work, while permanent work was more often active work. Except for on-call work, temporary work was more insecure and associated with worse health and work-related attitude scores than permanent work. Finally, the quality of working life and job insecurity partly accounted for most contract differences in work-related attitudes but not in health. CONCLUSIONS: Especially agency workers have a lower health status and worse work-related attitudes. Job redesign measures regarding their quality of working life and job insecurity are recommended.

Distinguishing between overtime work and long workhours among full-time and part-time workers.

OBJECTIVES: This study aimed at disentangling the effects of overtime hours from those of long workhours. For part-time workers, overtime work is not intertwined with long workhours as it is for full-time workers. Therefore, part-time and full-time employees were compared with regard to the association between overtime and well-being (fatigue and work motivation). Such comparisons may also shed more light on the psychological meaning of overtime work for part-time and full-time workers. METHODS: A survey study was conducted among a representative sample of Dutch employees (N=2419). An analysis of covariance was used to investigate whether the relationship between overtime and well-being differs between marginal part-time (8-20 contractual workhours), substantial part-time (21-34 hours), and full-time (>or=35 hours) workers. Work characteristics (ie, job demands, decision latitude, and job variety), age, and gender were treated as covariates. RESULTS: No significant relationship between overtime and fatigue was found for any of the contract-hour groups. For the part-time workers, overtime was not related to higher work motivation, whereas for full-time workers it was. CONCLUSIONS: It is important to distinguish between overtime and long workhours, given the differential overtime-motivation relationship among part-time and full-time workers. This finding suggests that part-time employees work overtime for reasons other than motivation or that working overtime does not enhance work motivation for this group of employees. Overtime work seems to have a different meaning for part-time and full-time workers.

Working overtime hours: relations with fatigue, work motivation, and the quality of work.

OBJECTIVES: We sought to better understand the relationship between overtime and mental fatigue by taking into account work motivation and the quality of overtime work and studying theoretically derived subgroups. METHODS: We conducted a survey-study among a representative sample of the Dutch full-time workforce (n = 1807). The prevalence of overtime work and the associations between overtime and job demands, job variety, decision latitude, fatigue, and work motivation was studied through descriptive statistics. We used MANCOVA (covariates: age, gender, salary level) to compare six overtime-fatigue subgroups with respect to work motivation and job characteristics. RESULTS: A total of 67% of the respondents worked overtime (mean, 3.5 hours). Overtime workers appeared to be nonfatigued, motivated workers with favorable work characteristics. MANCOVA revealed no significant overtime-fatigue interaction. CONCLUSIONS: Moderate overtime is common among Dutch workers, who seem to be happy workers with attractive jobs rather than fatigued employees.