Effects of Cocaine Abuse on Cognition

Cocaine is a highly addictive substance that is known to induce feelings of euphoria, energy, and supremacy. In some circles, it is known as the “caviar of street drugs” with its pricey yet seemingly insatiable quality (Cocaine Use and Its Effects, N.d.). Having inspired movies like Scarface and Blow, its place in pop culture is undeniable, enticing everyday people to experience the drug used by the famous. It denotes a level of higher status, which can appeal to those who want to live the fast lives of the rich and famous. Even Sigmund Freud, one of the godfathers if not the founder of psychology, called it “Uber Coca” (Friedman, 2012, p. 303). On the chemical level, it is a dopamine, norepinephrine, and serotonin reuptake inhibitor, blocking these neurotransmitters from being reabsorbed into the pre-synaptic neuron (Cocaine Use and Its Effects, n.d.). The unnatural dwelling of these neurotransmitters produces positive feelings. However, this sword cuts both ways, causing paranoia, anxiety, and irritability, often turning into depression once the effects of the drug subside. Moreover, this form of synthetic happiness can have a long-term negative impact on cognitive functioning.

Neuropsychological Effects

Soar, Mason, Potton, and Dawkins (2012) studied neuropsychological effects associated with recreational cocaine abuse. They hypothesized that cocaine would have an overall negative effect on cognition. Cocaine users were defined as snorting cocaine within the previous year but no more than 10 times within the last month. All participants resided in and around London, the capital of the UK where it is reported to have the highest usage rates in all of the European Union. Comparisons between the cocaine user group (n =17) and the control group (n = 24) were made using the General Health Questionnaire (GHQ-12) and the Brief Schizotypal Personality Questionnaire (SPQ-B). Additionally, four neuropsychological tasks were given, addressing the areas of spatial working memory (SWM), intra/extra-dimensional set-shifting (IED), the Stockings of Cambridge (SOC), and rapid visual processing (RVP).

Methods

The GHQ-12 was meant to measure the psychological health of each participant. Twelve items on a four-point Likert scale ranging from “less than usual” at the lowest point to “much more than usual” at the highest point. Scores were awarded 0-3 points on each item, with total scores ranging from 0-36. Lower scores reflected better psychological health.

Schizotypy traits were assessed via the SPQ-B, a 22-item questionnaire using yes/no responses. Within the questionnaire are three subscales meant to measure disorganized, interpersonal, cognitive, and perceptual schizotypy. Higher scores indicated a higher proneness to schizotypy.

SWM measured the “ability of participants to retain spatial information and to manipulate remembered items in working memory” (Soar et al. 2012, p. 636). The exercise required the finding of blue tokens in one of many different boxes and moving it aside to a column on the right side of the computer screen, and returning to the boxes without opening the same box. Errors were measured in terms of returning to a box that has already been opened.

An executive functioning task, which tests “rule acquisition and reversal” was tested via the IED (Soar et al. 2012, p. 636). Participants were presented with two colored shapes and were given the task of learning which one was correct based on preset measures. Once the participant accomplished this, the contingencies were reversed, rendering the incorrect stimulus correct. With the completion of each stage, difficulty was increased by adding another dimension to the shapes, making it harder to discern the difference. Errors were measured on several counts: errors made on stages completed, the number of trials on each completed stage, the number of errors made before the addition of another dimension, the total number of stages completed.

SOC measures spatial planning (Soar et al., 2012). The participants were presented with two displays that included three colored balls stacked on top of one another. In the lower display, the participant moved the balls to match the upper display. Abilities were measured by the number of moves it took to match the upper display, and the time it took to do so. The test ended if the participant completed the three matches in a row. Further measures were the time it took to plan the solution (before the first move), the speed of movement after the first move, and the number of times trials were completed with the lowest possible amount of moves.

The final measure, RVP, was concerned with sustained attention (Soar et al., 2012). Sequences of numbers were shown in the center of a computer screen and participants were to try and identify instances where only odd numbers were in succession and when only even numbers were shown. The numbers were shown at a rate of 100 digits per minute. The number of correct and incorrect responses were recorded.

Results

Cocaine users scored significantly more poorly on a variety of measures compared to the control group (Soar et al., 2012). Total SPQ-B scores were higher for cocaine users, denoting a higher proneness to schizotypy. Moreover, the SPQ-B showed significantly higher scores on the disorganized thinking and cognitive perceptual subscales. Cocaine users also showed poorer detection rates on the RVP measure, making significantly fewer hits than non-users. On the IED task, cocaine users produced significantly more errors and were unable to complete as many stages as the controls. SWM scores showed more errors for the cocaine group, but only reflected a significant difference in stage six. Similarly, cocaine users took longer to plan in the SOC tasks but none of the measures were statistically significant.

Discussion

Overall, cocaine users displayed an impaired ability to complete tasks as efficiently as non-users, particularly in the areas of sustained/flexibility of attention, spatial working memory, and executive functioning (Soar et al., 2012, p. 641). These findings were not confounded by other drug use or levels of schizotypy. Spatial planning reflected no statistically significant differences between the groups; however, there were notable differences in favor of the control group nonetheless. Future implications for research include the effects of cocaine abuse, which would likely show even more significant correlations between use and cognitive impairment.

Cortical Activation in Rhesus Monkeys

Exposure to cues associated with cocaine use can inspire cravings and relapse (Howell, Votaw, Goodman, and Lindsey (2010). Utilizing neuroimaging, studies have begun to define neurobiological characteristics of cocaine use and/or exposure to cocaine cues. The purpose of this study was to document brain activity during cocaine use by nonhuman primates. They hypothesized that the effects of cocaine use would extend beyond the limbic system and directly affect parts of the brain associated with cognitive processes.

Methods

Subjects included three female and two male adult rhesus monkeys (Howell et al., 2010). Catheters were surgically placed into the monkeys’ hearts and exited through their lower backs. Cocaine was dissolved in 0.9% saline solution. Cocaine was administered at a rate of 2.0ml per 7 s. A Siemens 951 scanner was used for positron emission tomography (PET) imaging.

The procedure was divided into three different phases. The first was to determine the effects of acute usage at 1.0mg per kg in four previously drug-free subjects (Howell et al., 2010). Subjects were passively administered cocaine. In the second phase, the same four subjects were trained to press a lever to self-administer cocaine. A red light was shown to the primates that signified the availability of cocaine. Twenty responses (FR20) while the red light was illuminated resulted in a 0.33mg injection of cocaine or saline, followed by the red light turning white for the next 15 s, then shut off all lights for 60 s. This was repeated two more times to match the 1.0mg/kg dose in the first phase. In the final phase, three subjects were trained to press the lever under a more complex schedule of 10-min intervals. A completion of FR20 changed the stimulus light from red to white for 2 s. A successful completion of FR20 after the first 10-min interval resulted in a single injection of 0.33mg/kg of cocaine or saline, changing the stimulus light from red to white for 15 s. Each of the three consecutive 10-min intervals was followed by a one-min timeout, again matching the total dosage amount of the previous phases. The same three monkeys underwent extinction sessions where saline was substituted for cocaine under the same FR20 schedule. Two PET images were taken before the first drug doses were given to establish a baseline.

Results

Administration of cocaine in previously drug-free subjects induced activation of the prefrontal cortex, whereas, in contrast to this finding, self-administered cocaine included activation of the prefrontal cortex and anterior cingulated cortex, an important role in the functioning of the limbic system which plays a role in emotion, long-term memory, and motivation (Howell et al., 2010, p. 196). Self-administration can build a stronger cocaine dependence on the substance because it affects and can impair more parts of the brain.

Discussion

This study was the first to use functional brain imaging to view brain activity during cocaine use (Howell, 2010). The results showed qualitative differences in brain imaging between self-administered and monkeys that used passively. Self-administered users also showed activation of the prefrontal cortex during extinction periods, compared to activation of the prefrontal cortex among passive users. This suggests a craving for the drug in its absence as the brain remembers its euphoric effects. One criticism of this study is that it is unclear as to how subjects were administered cocaine during the first phase of passivity (i.e., time intervals) – it is only described as a “noncontingent” form of using (Howell et al., 2010, p. 193). Also, long-term effects of self-administration versus passive use. Nonetheless, it is clear that the effects of cocaine reach far beyond the limbic system and affect cognition. The prefrontal is an important structure in what distinguishes humans from mammals (Strauch, 2003). If that area of the brain is affected no matter what, then more studies like this one must be done to better understand how to fight addiction. Mapping areas of the brain that are most affected by cocaine use may be integral in developing a treatment plan against it.

Elevated Gray and White Matter in Abstainers

Previous studies have found lower neural tissue density in cocaine abusers compared to non-users (Hanlon, Dufault, Wesley, & Porrino, 2011). Hanlon et al. (2011) hypothesized that the density of neural tissue would be elevated in non-users compared to cocaine users; furthermore, they believed that this lower density among users could contribute to cognitive dysfunction.

Methods

Groups were separated into active users (n = 24), abstainers for at least one month (n = 24), and non-drug using controls (n = 25) (Hanlon et al., 2011). Controls had to match characteristics of the users and abstainers in terms of age, sex, and IQ, and they could not have used marijuana or any other illicit drugs within their lifetime. Users matched the Diagnostic and Statistical Manual of Mental Disorders-IV (DSM-IV) criteria for cocaine dependence.

All participants underwent a battery of cognitive assessments (Hanlon et al., 2011). Two of the measures were also included in the Soar et al. (2012) study – the IED and the SOC assessments. The Cambridge Neuropsychological Test Automated Battery (CANTAB) served as an extra measure, along with the Beck Depression Inventory (BDI) and Spielberger State-Trait Anxiety Inventory to assess depression and anxiety, respectively. Participants also received Magnetic Resonance Imaging (MRI).

Results

Abstainers were found to have a significantly higher gray and white matter density than current cocaine users, particularly in the frontal and temporal cortexes (Hanlon et al., 2011). Abstainers had lower tissue density than the control group, but this finding was not statistically significant and may reflect a history of using more than anything. No regions of the brain reflected a higher gray or white matter density among cocaine users compared to abstainers and non-users. In terms of cognitive performance, cocaine users displayed slower reaction times and lower accuracy on all tests except the IED, where abstainers and users scored significantly more poorly compared to the non-using controls. Multiple regression revealed a negative correlation between gray matter density and reaction time in the prefrontal cortex (Hanlon et al., 2011, p. 688). No significant correlations were found between white matter density and performance on cognitive tasks, nor were significant correlations between the density of neural tissue and BDI scores.

Discussion

Cocaine use has an undeniable impact on one’s ability to perform cognitive tasks. Perhaps the most alarming finding is the slowed reaction time in the prefrontal cortex, the part of the brain that separates us from other mammals (Strauch, 2003). The prefrontal cortex helps humans reason and resist impulses. When concerned with addiction, it is no wonder impulses to use drugs are difficult to fight. Furthermore, impaired reason makes it more likely for an addict to justify their use, ignoring the negative impact on their health and finances. This study sets the stage for longitudinal studies to amend a shortcoming of this study in that abstainers should have their brains scanned and tested more than once, and again months and years after the original study.

Conclusion

Cocaine may produce temporary euphoria but the price of such indulgence has irreversible effects. As demonstrated in Hanlon et al. (2011), the subcortical density of gray matter was lower among users and abstainers, suggesting some damage to the brain cannot be undone even after abstaining. Moreover, users and abstainers showed poorer memory and reaction times on a variety of tasks. Therefore, the aftereffects of cocaine use can follow the user long after the high diminishes. Perhaps it is the impairment of the prefrontal cortex that most notably changes users and former users. The prefrontal cortex gives humans personality, the ability to reason, and the ability to think abstractly about things (Strauch, 2003). The neurotransmitters affected during cocaine use are part of the pleasure center of the brain. Having that amount of happiness constantly in the brain is likely to create a new baseline where cocaine is needed just to feel “normal.” At this point, cocaine is no longer a drug that induces happiness - it is a drug that damages the brain with each use in ways that cannot be amended. More research needs to be done to cement the negative effects into scientific journals, where more credence is given to warnings against cocaine or any drug use, versus the general idea that illegal drugs are bad. In popular media, illicit drugs are actually amongst the stars.

References

Cocaine Use and Its Effects. (N.d) WebMD.com Retrieved April 7, 2014 from http://www.webmd.com/mental-health/addiction/cocaine-use-and-its-effects

Friedman, R. M. (2012). Review of 'An anatomy of addiction: Sigmund Freud, William Halsted and the miracle drug, ''cocaine'. Psychiatry: Interpersonal And Biological Processes, 75(3), 301-304. doi:10.1521/psyc.2012.75.3.301

Hanlon, C. A., Dufault, D. L., Wesley, M. J., & Porrino, L. J. (2011). Elevated gray and white matter densities in cocaine abstainers compared to current users. Psychopharmacology, 218(4), 681-692. doi:10.1007/s00213-011-2360-y

Howell, L. L., Votaw, J. R., Goodman, M. M., & Lindsey, K. P. (2010). Cortical activation during cocaine use and extinction in rhesus monkeys. Psychopharmacology, 208(2), 191-199. doi:10.1007/s00213-009-1720-3

Soar, K., Mason, C., Potton, A., & Dawkins, L. (2012). Neuropsychological effects associated with recreational cocaine use. Psychopharmacology, 222(4), 633-643. doi:10.1007/s00213-012-2666-4

Strauch, B. (2003) The Primal Teen: What the new discoveries about the teenage brain tell us about our kids. New York, NY: Anchor Books.