Assessment of perceived stress and association with sleep quality and attributed stressors among 1st-year medical students: A cross-sectional study from Karwar, Karnataka, India.

OBJECTIVES: The objective is to study the extent of perceived stress among 1st-year medical students using the Perceived Stress Scale-14 (PSS-14) and its association with sleep quality as assessed by the Pittsburgh Sleep Quality Index (PSQI) and attributed stressors. MATERIALS AND METHODS: A cross-sectional study was conducted of 121 1st-year medical students at Karwar Institute of Medical Sciences, Karwar, Karnataka, India. The extent of their stress was assessed using the PSS-14 and their sleep quality was assessed using the PSQI. Graded stress exerted by the attributed stressors was also assessed. RESULTS: A total of 33.8% of participants had perceived stress scores of >28. Among academic stressors, performance in examinations (34.7%), lack of time for recreation (30.6%), curriculum (24.8%), and frequency of examinations (24.8%) were the highest rated stressors. Quality of food in the mess (50.4%) and lack of entertainment in the institution (39.7%) were the highest rated psychosocial stressors. There was a positive correlation between the PSS-14 scores and various academic stressors and the global PSQI score. CONCLUSION: First-year medical students reported a high level of stress, including academic and psychosocial stressors. Effective changes in the curriculum and living conditions can reduce the level of stress among these students.

Extinction of Contextual Fear with Timed Exposure to Enriched Environment: A Differential Effect.

BACKGROUND: Extinction of fear memory depends on the environmental and emotional cues. Furthermore, consolidation of extinction is also dependent on the environmental exposure. But, the relationship of the time of the exposure to a variety of environmental cues is not well known. The important region involved in facilitation of extinction of fear memory is through diversion of the flow of information leaving the lateral nucleus of amygdala. PURPOSE: The study aimed to address a question to explain how these brain regions react to environmental stimulation during the retention and extinction of fear memory. METHODS: An enriched environment (EE) is assumed to mediate extinction of fear memory, we examined the apparent discrepancy between the effects of defensive response, the freezing behavior induced by Pavlovian classical fear conditioning by subjecting them to variance in the timing to EE. The different timing of EE exposure was 10 days of EE either before fear conditioning and/or after extinction training to the rats. The local field potentials was recorded from CA1 hippocampus, lateral nucleus of amygdala and infralimbic region of medial prefrontal cortex (mPFC) during the fear learning and extinction from the control rats and rats exposed to EE before and after fear conditioning. RESULTS: Exposure to EE before the fear conditioning and after extinction training was more effective in the extinction fear memory. In addition, we also found switching from exploratory locomotion to freezing during retention of contextual fear memory which was associated with decreased theta power and reduced synchronized theta oscillations in CA1-hippocampus, lateral nucleus of amygdala, and infralimbic region of mPFC. CONCLUSION: Thus, we propose that the timing of exposure to EE play a key role in the extinction of fear memory.

Long term exposure to combination paradigm of environmental enrichment, physical exercise and diet reverses the spatial memory deficits and restores hippocampal neurogenesis in ventral subicular lesioned rats.

Subiculum is an important structure of the hippocampal formation and plays an imperative role in spatial learning and memory functions. We have demonstrated earlier the cognitive impairment following bilateral ventral subicular lesion (VSL) in rats. We found that short term exposure to enriched environment (EE) did not help to reverse the spatial memory deficits in water maze task suggesting the need for an appropriate enriched paradigm towards the recovery of spatial memory. In the present study, the efficacy of long term exposure of VSL rats to combination paradigm of environmental enrichment (EE), physical exercise and 18 C.W. diet (Combination Therapy - CT) in reversing the spatial memory deficits in Morris water maze task has been studied. Ibotenate lesioning of ventral subiculum produced significant impairment of performance in the Morris water maze and reduced the hippocampal neurogenesis in rats. Post lesion exposure to C.T. restored the hippocampal neurogenesis and improved the spatial memory functions in VSL rats. Our study supports the hypothesis that the combination paradigm is critical towards the development of an enhanced behavioral and cognitive experience especially in conditions of CNS insults and the associated cognitive dysfunctions.

A study on fear memory retrieval and REM sleep in maternal separation and isolation stressed rats.

As rapid brain development occurs during the neonatal period, environmental manipulation during this period may have a significant impact on sleep and memory functions. Moreover, rapid eye movement (REM) sleep plays an important role in integrating new information with the previously stored emotional experience. Hence, the impact of early maternal separation and isolation stress (MS) during the stress hyporesponsive period (SHRP) on fear memory retention and sleep in rats were studied. The neonatal rats were subjected to maternal separation and isolation stress during postnatal days 5-7 (6h daily/3d). Polysomnographic recordings and differential fear conditioning was carried out in two different sets of rats aged 2 months. The neuronal replay during REM sleep was analyzed using different parameters. MS rats showed increased time in REM stage and total sleep period also increased. MS rats showed fear generalization with increased fear memory retention than normal control (NC). The detailed analysis of the local field potentials across different time periods of REM sleep showed increased theta oscillations in the hippocampus, amygdala and cortical circuits. Our findings suggest that stress during SHRP has sensitized the hippocampus-amygdala-cortical loops which could be due to increased release of corticosterone that generally occurs during REM sleep. These rats when subjected to fear conditioning exhibit increased fear memory and increased fear generalization. The development of helplessness, anxiety and sleep changes in human patients, thus, could be related to the reduced thermal, tactile and social stimulation during SHRP on brain plasticity and fear memory functions.

Chronic stress-induced changes in REM sleep on θ oscillations in the rat hippocampus and amygdala.

The present study investigated the effect of Chronic Immobilization Stress (CIS) on theta oscillations in the hippocampus and amygdala during Rapid Eye Movement (REM) sleep. Adult male Wistar rats were subjected to 2h of CIS daily for 10days. Polysomnographic recordings with electroencephalogram (EEG) from hippocampus (CA3 and CA1 subregion) and lateral nucleus of amygdala (LA) were carried out after termination of CIS protocol on the 7th, 14th and 21st day. The results showed a bimodal distribution on the total REM sleep duration in CIS rats: group of rats exhibited increased REM sleep duration considered as a stress-enhanced REM (SER) and rats with reduced REM sleep as stress-reduced REM sleep (SRR) group. The bimodal distribution in REM sleep was continued to exhibit even after 21 days of termination of stress, showing increased REM sleep in SER and reversible REM sleep in SRR rats. In addition to changes in sleep, increased REM sleep in SER rats was associated with attenuated theta activity in the hippocampus and amygdala, while the SRR rats did not show attenuated theta activities during the stress recovery period. Thus, the study demonstrates the dependence of synchronized amygdalo-hippocampal theta activity with the CIS-induced enhanced REM sleep duration. This raises the possibility that CIS-induced manifestations of the anxiety may be associated with synchronized theta oscillations in the hippocampus and amygdala.