Abhinav Dixit

Effect of caffeine on central auditory pathways: An evoked potential study

Caffeine is consumed in various forms like tea, coffee, chocolates and colas. The present study evaluated the effect of caffeine on auditory brainstem response (ABR), mid latency response (MLR) and slow vertex response (SVR) in 40 male volunteers. The recordings were done using a computerized evoked potential recorder by 10-20 electrode placement system. The subjects consumed 3mg/kg body weight of caffeine after 12h abstinence from caffeine in any form. The data obtained revealed that latencies of waves IV and V along with I-V interpeak interval of ABR decreased significantly. This was accompanied with significant increase in amplitude of wave V. MLR latencies and latency of P1 wave of SVR was significantly decreased following caffeine ingestion. The results indicated that caffeine improves transmission in the peripheral and central brain auditory pathways.

Effect of caffeine on information processing: evidence from stroop task.

Background: Caffeine is a pyschostimulant present in various beverages and known to alter alertness and performance by acting on the central nervous system. Its effects on central nervous system have been studied using EEG, evoked potentials, fMRI, and neuropsychological tests. The Stroop task is a widely used tool in psychophysiology to understand the attention processes and is based on the principle that processing of two different kinds of information (like the word or colour) is parallel and at different speeds with a common response channel. Aim: To study the effect of caffeine on classical color word Stroop task. Materials and Methods: This study was conducted on 30 male undergraduate students by performing a test before and 40 minutes after consuming 3 mg/Kg caffeine and evaluating the effect of caffeine on Stroop interference and facilitation. Results: The results revealed that practice has no effect on the performance in a Stroop task. However, there was reduction in Stroop interference and increase in facilitation after consumption of caffeine as was evident by changes in the reaction times in response to neutral, incongruent, and congruent stimuli. Conclusion: We hypothesize that caffeine led to faster processing of relevant information.

Psychomotor performance of medical students: effect of 24 hours of sleep deprivation

Context: Sleep deprivation is known to have detrimental effects on attentional resources and cognitive functions. Aim: The aim of this study is to assess the changes in performance, due to 24 h of sleep deprivation, in medical students Materials and Methods: The performance was assessed using simple paper–pencil tasks, such as digit symbol substitution test, digit vigilance test, and letter cancellation tasks. Results: The results revealed an increase in the number of errors in letter cancellation tasks and digit vigilance test, with a significant decrease in the number of correct responses on the letter cancellation task. The time taken to complete the tests increased with lack of sleep, with the digit symbol substitution test being affected the most. Discussion: This study infers that sleep deprivation for 24 h affected the judgment ability more than the response speed. Conclusion: Sleep deprivation might lead to compromised performance of medical students in examinations.

Attention and information processing in end stage renal disease and effect of hemodialysis: a bedside study

Abstract The neurobehavioral syndrome of uremia in chronic kidney disease affects the functioning of the central nervous system. Cognitive impairment is one of the most important manifestations of this dysfunction. The process of hemodialysis is known to bring about conflicting changes in the cognitive status of patients. In the present study an assessment of cognitive status of patients with end stage renal disease was done in comparison to controls before and after a session of hemodialysis using simple bedside paper-pencil tests. Thirty patients of end stage renal disease on maintenance dialysis for at least one month with MMSE score >24 were assessed one hour before and one hour after hemodialysis using Digit Symbol Substitution Test, One Letter and Three Letter Cancellations tasks. Their results were compared to age and sex matched healthy controls. The patients with end stage renal disease had significantly lower performance in cognitive tests in comparison to controls. The performance improved 1 hour after hemodialysis in comparison to pre-dialysis values. However, the values after dialysis were significantly lower than in controls, thereby indicating that though the cognitive functions improved after hemodialysis, they did not reach the control levels. There was also a significant change in the biochemical parameters after dialysis. We conclude that patients with end stage renal disease suffered from cognitive impairment which improved on hemodialysis due to removal of metabolic waste products.

Executive Functions Are Not Affected by 24 Hours of Sleep Deprivation: A Color-Word Stroop Task Study

Background: Sleep is an important factor affecting cognitive performance. Sleep deprivation results in fatigue, lack of concentration, confusion and sleepiness along with anxiety, depression and irritability. Sleep deprivation can have serious consequences in professions like armed forces and medicine where quick decisions and actions need to be taken. Color-Word Stroop task is one of the reliable tests to assess attention and it analyzes the processing of information in two dimensions i.e., reading of words and naming of colour. The evidence regarding the effect of sleep deprivation on Stroop interference is conflicting. The present study evaluated the effect of 24 hours of sleep deprivation on reaction time and interference in Stroop task. Materials and Methods: The present study was done on 30 healthy male medical student volunteers in the age group of 18-25 years after taking their consent and clearance from Institute Ethics Committee. Recordings of Stroop task were at three times: baseline (between 7-9 am), after 12 hours (7-9 pm) and after 24 hours (7-9 am, next day). The subjects were allowed to perform normal daily activities. Results: The study revealed a significant increase in reaction time after 24 hours of sleep deprivation in comparison to baseline and after 12 hours of sleep deprivation. There was no significant change in interference and facilitation after sleep deprivation in comparison to baseline. The number of errors also did not show any significant change after sleep deprivation. Conclusion: The study indicated that there was slowing of responses without change in executive functions after 24 hours of sleep deprivation. It is probable that 24 hours of sleep deprivation does not bring about change in areas of brain affecting executive functions in healthy individuals who have normal sleep cycle. The present study indicated that in professions like armed forces and medicine working 24 hours at a stretch can lead to decrease in motor responses without affecting information processing and judgment ability.

Caffeinated Drinks and the Human Body

The last decade has seen a growth in marketing and consumption of the so called ‘‘Energy Drinks’’ in India. These drinks are non-alcoholic and contain stimulants like caffeine along with taurine, glucuronolactone, vitamins etc. [1]. The widespread use of these drinks has occurred due to publicity as their being an instant source of energy. The young generation is consuming more of these as compared to healthier substitutes like juices. These caffeinated drinks are being sold under different brands but there is no regulation on their ingredients, use and contraindications. At some places they are being promoted as health supplements. The main ingredient of these drinks is caffeine which is chemically 1,3,7-trimethylxanthine. Caffeine is also present in other drinks consumed by humans like tea, coffee and colas and its amount vary from 24–50 mg/150 ml of tea to 40–180 mg/150 ml of coffee [2]. Caffeine is readily absorbed from oral, rectal and parenteral routes and has a half-life of 3–7 h in the human body. Significant levels of caffeine are detected in the brain within 5 min of oral intake with peak levels in about 30 min [3]. Caffeine acts via various mechanisms in the human body. One of the mechanisms is mobilization of intracellular calcium. It has also been shown to act via inhibition of phosphodiesterase. Another mechanism of action is via binding to benzodiazepine receptors. The main mechanism of action of caffeine is believed to be by blocking of adenosine receptors. The adenosine receptors have a widespread distribution in the human brain with maximum concentrations in hippocampus, cerebellar and cerebral cortex [4]. Caffeine by blocking adenosine receptors brings about changes in the levels of neurotransmitters like adrenaline, dopamine, serotonin, acetylcholine, glutamate and GABA. The growth in the consumption of caffeinated drinks has been sparked by the publicity of the beneficial effects of caffeine. Caffeine increases the alertness levels and allays fatigue. Caffeine has been shown to improve information processing by the brain, sensory functions and the motor response [5–7]. However, there is also a flip side to the use of caffeine. Doses ranging from 400 to 800 mg in one sitting, may lead to tachycardia, nervousness, aggressiveness, insomnia and anxiety. Energy drinks have been reported to increase the risk of stroke and heart diseases along with alteration in clotting of blood. Extended use over long periods of time can lead to caffeinism with dependence on caffeine along with unpleasant sensations during its withdrawal. According to DSM-IV criteria, four disorders have also been attributed to excessive caffeine use namely caffeine intoxication, caffeine-induced anxiety disorder, caffeine-induced sleep disorder, and caffeine-related disorder not otherwise specified. The Food Standards Agency in UK has advised against excessive consumption of caffeine by pregnant women. There is an increase in consumption of ‘‘caffeinated’’ or ‘‘energy’’ drinks in the young especially in the age group of 18–24 years. These drinks are being marketed without a warning of the potential health hazards of consuming excess of caffeine [8]. The Food Safety and Standards Authority of India (FSSAI) has proposed regulations for these ‘‘Energy’’ or & Praveen Sharma praveensharma55@gmail.com

Review Article: A Critique

Dear Editor, I read the review article ‘Principles of Physics in Surgery: The Laws of Flow Dynamics Physics for Surgeons—Part I’ by Srivastava et al. [1] in July–August 2009 issue, pages 182–187 with great interest. The authors have very well summarized the various laws of physics applicable to haemodynamics. I am a regular reader of the Indian Journal of Surgery, but the publication of this ‘Review Article’ raises certain issues, which I believe should be considered by the editorial board. The title of the article gives an impression as if the laws of physics cited are applicable only to surgery. On the contrary, the authors could have used the word ‘Medical Science’ rather than surgery, because these laws are applicable to haemodynamics with which all clinical specialties have to deal with and not only surgeons. The article is nothing but a summary of well-established facts and chapters published in various text books of physics and physiology. A look at the reference list clearly brings this to light: Of the 17 references, 11 are textbooks and 6 of these are from only two textbooks [2, 3]. I wish to bring forth the fact, that the laws and their applications summarized are taught to undergraduate (MBBS) medical students during their first year of graduation, and hence it is difficult to believe that surgeons are unaware of these basic principles and a review article is required. A review article should not be just a mere presentation of facts that are well documented. It’s hard to believe that a journal like Indian Journal of Surgery has published nothing more than textbook knowledge as a review article. This letter should be viewed as a healthy comment for the growth and betterment of Indian medical journals in general.