Li et al. (2013) Abnormalities in Heroin-Addicted Users (Edexcel A-Level Psychology): Revision Notes
Li et al. (2013) Abnormalities in Heroin-Addicted Users
Aim
Li Qiang, Yang Wei-Chuan and colleagues investigated the relationship between chronic heroin use and changes in specific brain areas, particularly the posterior cingulate cortex (PCC). The PCC is a region of the cortex located next to the limbic system in the middle of the brain.
The PCC was selected for investigation because of its connectivity to other brain regions and its potential role in addiction-related processes. This area had received relatively little research attention despite its connections to neural circuits involved in reward and motivation.
The researchers focused on the PCC because of its connectivity to other brain regions. Previous research had identified neural circuits involved in reward, motivation, inhibitory control and working memory, all of which are implicated in addiction. However, very little research had examined the PCC specifically. The study aimed to explore the PCC's functional role in relation to heroin addiction.
Procedure
Participants
The sample consisted of 14 heroin-addicted males with an average age of 35 years. All participants were recruited from a drug rehabilitation centre in China and had been using heroin for an average of 89 months. At the time of the study, they were tested for opiate use and found to be clean of heroin and any other drug of addiction except nicotine. All were right-handed and none had a history of psychiatric disorder. They were all physically healthy and medically cleared to spend 40 minutes in a magnetic resonance imaging scanner.
The matched control group consisted of 15 males who varied from the experimental group only in their substance misuse history.
Matched Control Design
The control group was carefully matched to the experimental group on all variables except heroin use history. This design strength allows researchers to attribute differences in brain activity specifically to heroin use rather than other confounding variables.
Method
All participants underwent a session in an fMRI scanner under two conditions:
Resting-state condition: Participants focused their attention on a target for 5 minutes and did nothing else.
Cue-induced condition: After a 10-second gap following the resting-state, participants were exposed to 24 pictures of drug-related activity and 24 neutral pictures. Each picture was shown for 2 seconds in a random order. Between each picture presentation, there was an inter-stimulus interval which ranged between 4 and 12 seconds.
Data was analysed using statistical techniques designed to model brain activity in the two tasks over both conditions.
Results
Cue-induced task findings
Participants who had been addicted to heroin reported craving for heroin following the cue-inducing pictures. Brain scan analysis revealed different activation patterns in specific areas of the PCC and between the PCC and other regions associated with the brain's reward system in the heroin group compared to the control group.
Resting-state findings
In the resting-state, the relationship between different parts of the brain showed stronger connectivity between the PCC and bilateral insula, and between the posterior cingulate cortex PCC and bilateral dorsal striatum in chronic heroin users compared to the control group.
Understanding the Insula's Role
The insula is believed to be responsible for associating internal emotional states with decision-making behaviours. In ex-addicts, this region becomes more readily activated when exposed to drug cues because the behaviour pattern of craving and seeking drugs has been established through repeated use.
In other words, ex-addicts would have established a brain circuitry to respond to the urge to take a drug. The picture cues would have activated this pathway in the brain of an ex-addict, but not in a healthy control.
Abnormal dorsal striatum functioning has been associated with drug-seeking behaviour. The increased connectivity between the PCC and dorsal striatum might explain the abnormal reward and craving experienced by ex-addicts.
Correlation findings
There was a positive correlation between the degree of connectivity between these regions of the brain and the length of time of heroin use. Chronic users of heroin showed the greatest level of connectivity.
This demonstrates that brain pathways associated with addiction, craving and the brain's own reward system become more established with increased length of drug use.
Conclusion
Activity in the PCC was increased when heroin users were exposed to drug-related cues. This brain area is linked to visual orientation and reward processing, and is sensitive to unpredictable rewards. Heroin use alters the functionality and connectivity of the brain to reinforce addictive thinking, craving and drug-seeking behaviour, which becomes abnormally associated with reward.
Key Implication for Relapse
This brain circuitry is activated when presented with a heroin cue, which may explain why ex-addicts are particularly susceptible to relapse if exposed to a drug stimulus that activates these areas of the brain. The researchers also concluded that the PCC could be a useful indicator for the extent of brain damage caused by heroin use.
Evaluation
Strengths
Well-matched samples: The samples were well matched, as statistical tests across several measures such as nicotine use revealed no differences between the groups other than their history of substance abuse. This suggests that the differences observed in the PCC were a result of heroin use only, although there could have been other factors not controlled in this investigation. The researchers also ensured that the ex-addicts were detoxified by conducting a urine analysis, making sure they did not have morphine in their body during the investigation.
Consistency with other research: The results are consistent with a range of other studies testing different brain areas that show similar differences in the reward centres of the brain associated with heroin use. Although only a small sample of participants were used, research using ex-addicts can have serious ethical implications.
Controlling for Background Noise
Using scanning to measure activity in one specific brain area is difficult, as other areas will also be active and could cause the analysis to be less reliable. However, the background 'noise' from other brain areas would have affected the heroin users and healthy participants equally, so the difference that was observed could be regarded as a genuine effect of heroin use.
Ethical approval: All participants gave fully informed consent and the procedure was approved by two ethical committees.
Practical applications: The findings helped to build a picture of the effect of long-term drug misuse and provide a marker of brain damage, which helps to measure the severity of the effect of drug addiction. They also helped to build a model of the brain structures associated with addiction.
Weaknesses
Small sample size and limited generalisability: The sample size used in this research was small and limited to males from only one culture, suggesting that generalisability beyond this group may be unreliable. However, the results are consistent with other studies testing different brain areas.
Ethical Concerns with Cue Exposure
Exposing addicts to drug cues could have implications for relapse for the individuals concerned, particularly in the detoxification phase that they were currently in. This raises questions about the risk-benefit balance of such research methods.
Difficulty isolating brain areas: Using scanning to measure activity in one specific brain area is difficult, as other areas will also be active and could make the analysis less reliable.
Remember!
Key Points to Remember:
- Li et al. (2013) investigated the posterior cingulate cortex (PCC) in heroin-addicted users using fMRI scanning
- The study found increased PCC activation when heroin users were exposed to drug-related cues, and stronger connectivity between the PCC and other brain regions (insula and dorsal striatum) compared to controls
- A positive correlation was found between connectivity strength and length of heroin use, suggesting brain pathways become more established with prolonged drug use
- The study had well-matched samples and ethical approval, but was limited by small sample size (14 heroin users, 15 controls) and limited generalisability
- The findings suggest the PCC could be a useful indicator of brain damage from heroin use and may explain why ex-addicts are susceptible to relapse when exposed to drug-related cues