Kelly LiangAM Class7/27/2014

The Effects of Different Amounts of Alcohol on Neurotransmission in Prefrontal Cortex that Affects One’s Attention

Abstract

Introduction

Alcohol has been known for disturbing people’s ability to make decision, retrieve past memory, and control their emotions. Since everyone is different in height and weight, as well as the number of enzymes that break down alcohol in bloodstream, everyone possesses different level of alcohol sensitivity, so the level of alcohol sensitivity correlates with the extent of alcohol intoxication effects and physiological changes.

Chronic consumption of alcohol can lead to cerebral atrophy, although little amount of alcohol consumption can actually improve short-term memory and reasoning. Chronic Alcoholics were also reported to perform worse than the sober when both were doing the same tasks on attention, execution, and memory.

One of the ways alcohol damages the brain is its effects on different neurotransmitters, especially the inhibitory ones, which cause people to have less control over their emotions and talk a lot when they are intoxicated with alcohol. In additions, these inhibitory neurotransmitters can impair people’s ability to make decisions and concentrate on certain tasks, which include reaction time.

From all these information I got from previous studies, I assume that the amount of alcohol consumption correlates positively with the amount of time that takes a participant to finish a task that requires much attention, because alcohol induces changes that happen to neurotransmitters in brain, in an attention task.

Method

40 participants are selected randomly from newspaper advertisements, with ages range from 25 to 35. They all must have a clean history substance abuse and good health conditions without any major medical conditions (including pregnancy, for alcohol can affect the development of the fetus’s brain) and have a moderate amount of drinks each week (4-15 drinks per week). To test these participants’ alcohol sensitivity, they will be given certain number of drinks to see if they feel any big difference to the drinks a month before the experiment. Participants who are too sensitive or too unsusceptible to alcohol will be excluded from this experiment.

In this experiment, Trail Making Test Part B (TMT-B) will be used. It has been used in previous studies to test out prefrontal functions and cognitive performance of the alcohol-dependent patients. The TMT-B is a measure of visual–conceptual and motor

skills, with a focus on divided attention and mental flexibility. The participant is instructed to connect randomly-arranged circles each of which contains either a number from 1 to 13 or a letter from A to L as quickly as possible. The dependent measure is the total time (in seconds) required to complete the task.

Participants will be randomly assigned to receive a high dose (0.80 g/kg ethanol for men, 0.72 g/kg ethanol for women), moderate dose (0.40 g/kg ethanol for men, 0.36 g/kg ethanol for women), or placebo dose (actually, 0.04 g/kg ethanol) vodka (100 proof) and tonic beverage. They will consume the beverage about 15-20 minutes before they start their tasks to let the alcohol get to their brains through bloodstream. The amount of time that takes the participants to finish the task will be measured in seconds.

To check which parts of the brain will be more active, electrodes are put onto participants’ scalps to see if there are any other regions of the brain are active besides the frontal cortex during the task.

Results

Discussion

The frontal lobe activity can be affected by the increase in gamma-aminobutyric acid (GABA), a type of inhibitory neurotransmitters that restrict the actions of glutamate and its receptor, NMDA, which can depress one’s cognition and motor skills. Small amounts of alcohol have been shown to interfere with glutamate action. This interference could affect several brain functions, including memory. The frontal lobe activity can be affected by the increase in glutamatergic release induced by the decreased sensitivity of NMDA receptors in brain, for the frontal lobe is rich in glutamatergic tracts. However, since most regions of the brain have these neurotransmitters and receptors, it is hard to tell whether it is the neurotransmitters and receptors in the prefrontal cortex only that affect the amount of time it took for the participants to finish their tasks, so this part of the hypothesis is not proved.

Chronic alcohol consumption increases glutamate receptor sites in the hippocampus. During alcohol withdrawal, glutamate receptors that have adapted to the long–term presence of alcohol may become overactive, and this hypo-activity has been repeatedly linked to neuronal death, which is manifested by conditions such as stroke and seizures.

Conclusion

The amount of alcohol consumption correlates positively with the amount of time that takes a participant to finish a task that requires much attention and motor skills, but it is still unclear that whether it is the prefrontal

cortex or regions of brain that control the motor skills (e.g., cerebellum) that affect the speed more.

References

Bartholow, Bruce D., et al. "Effects of alcohol consumption and alcohol susceptibility on cognition: a psychophysiological examination." Biological Psychology 64.1 (2003): 167-190.

Loeber, Sabine, et al. "Impairment of cognitive abilities and decision making after chronic use of alcohol: the impact of multiple detoxifications." Alcohol and Alcoholism (2009): agp030.

Oscar-Berman, Marlene, and Ksenija Marinkovic. "Alcoholism and the brain: an overview." Alcohol Research and Health 27.2 (2003): 125-133.

Zeigler, Donald W., et al. "The neurocognitive effects of alcohol on adolescents and college students." Preventive medicine 40.1 (2005): 23-32.