Electroencephalography-based cortical sources of working memory in the subjects with opioid addiction: A pilot study.

Background & objectives: Working memory impairments in the subjects of opioid addiction may stem from an aberrant cortical activity in the executive areas, and may help in early identification of individuals with addictive tendencies and may also be used as a neurofeedback mechanism in adjunct to the existing therapeutics. Methods: Electrical neuroimaging via 128-channel electroencephalography (EEG) recording was done in 15 male subjects with opioid addiction (29.45±5.6 yr) during the performance of Sternberg Working Memory Task. EEG data were acquired and analyzed for cortical sources during task as compared to resting (baseline) condition. Results: Working memory deficits were manifested as decrease in accuracy percentage in the subjects with opioid addiction, while no significant difference was seen in reaction time, on comparison with laboratory-acquired matched controls. Standardized low-resolution brain electromagnetic tomography (sLORETA)-based EEG source analysis revealed higher cortical activity in the anterior cingulate cortex, inferior, middle and superior temporal gyri, inferior frontal gyrus, superior parietal lobule, inferior parietal lobule and precuneus, whereas significant lower activity was seen in superior and middle frontal gyri, parietal lobule, cingulate cortex and pre- and postcentral gyri when the task was compared to baseline in the subjects with opioid addiction. Further, a negative correlation was seen between the accuracy of task performance and activation ratio for the significant gyri in the subjects with opioid addiction. Interpretation & conclusions: EEG cortical sources revealed the failure of deactivation of default-mode network (DMN) during the task amongst the subjects with opioid addiction. In addition, there was a decrease in the executive function areas in the subjects with opioid addiction. This lack of sufficiently active executive network and persistence of DMN during the task (as compared to baseline) may potentially form the basis of functional impairments in the subjects with opioid addiction.

Planning, implementation, and evaluation of multicomponent, case-based learning for first-year Indian medical undergraduates.

Didactic lecture is an effective method to quickly pass on a high volume of information to a large number of students. However, if not well designed, lectures can be monotonous and provide only passive learning, with little scope for higher order learning skills. To address this drawback of lectures, we supplemented it with case-based learning (CBL), which has been shown to promote self-learning. After giving an overview of gastrointestinal physiology through lectures, CBL on peptic ulcer disease was implemented for first-year Bachelor of Medicine, Bachelor of Surgery students. The present study aimed to evaluate the students' and teachers' opinions on the notion of supplementing lectures with CBL. In previous reports, discussion using clinical cases was primarily employed as the solitary component for conducting CBL. In the present study, three different but mutually exclusive components, such as case discussion, concept map, and critical thinking exercise on a specific topic in gastrointestinal pathophysiology, were integrated to form the multicomponent CBL (MC-CBL). Students reported that MC-CBL could promote application of the knowledge learned in lectures in a more appropriate context (92.42% positive response), enhance their learning efficiency (98.46% positive response), promote their active participation in the learning process (98.48% positive response), and help them in integrating physiological concepts with clinical science (98.46% positive response). Teachers observed that MC-CBL could promote active learning, analytic, and problem-solving skills of students. In conclusion, MC-CBL appeared to be an effective supplement for the lectures, providing an opportunity for the students to relate the knowledge learned during lectures.

Default mode network aberrance in subjects of alcohol and opioid use disorders during working memory task: An exploratory EEG microstates study.

Background: Aberrance in switching from default mode network (DMN) to fronto-parietal network (FPN) is proposed to underlie working memory deficits in subjects with substance use disorders, which can be studied using neuro-imaging techniques during cognitive tasks. The current study used EEG to investigate pre-stimulus microstates during the performance of Sternberg's working memory task in subjects with substance use disorders. Methods: 128-channel EEG was acquired and processed in ten age and gender-matched subjects, each with alcohol use disorder, opioid use disorder, and controls while they performed Sternberg's task. Behavioral parameters, pre-stimulus EEG microstate, and underlying sources were analyzed and compared between subjects with substance use disorders and controls. Results: Both alcohol and opioid use disorder subjects had significantly lower accuracy (P < 0.01), while reaction times were significantly higher only in subjects of alcohol use disorder compared to controls (P < 0.01) and opioid use disorder (P < 0.01), reflecting working memory deficits of varying degrees in subjects with substance use disorders. Pre-stimulus EEG microstate revealed four topographic Maps 1-4: subjects of alcohol and opioid use disorder showing significantly lower mean duration of Map 3 (visual processing) and Map 2 (saliency and DMN switching), respectively, compared to controls (P < 0.05). Conclusion: Reduced mean durations in Map 3 and 2 in subjects of alcohol and opioid use disorder can underlie their poorer performance in Sternberg's task. Furthermore, cortical sources revealed higher activity in both groups of substance use disorders in the parahippocampal gyrus- a hub of DMN; superior and middle temporal gyri associated with impulsivity; and insula that maintains balance between executive reflective system and impulsive system. EEG microstates can be used to envisage neural underpinnings implicated for working memory deficits in subjects of alcohol and opioid use disorders, reflected by aberrant switching between neural networks and information processing mechanisms.