My colleagues and I examine the brain processes involved in impulsivity, compulsivity and abnormal appetites, such as in eating disorders, drug taking, alcohol abuse, sexual behaviour and aggression, as well as deficits in attention. Eating disorders, addiction, aggression and attention deficits all have something in common: impulse control.How does the brain work to help us regulate our impulses - our desire to go after and consume something that appears appetising, or a threat to us? In the contemporary environment, we are bombarded with stimuli that is made to look attractive, appealing or threatening to us, whether it be food, sex, beautiful objects, 'potential terrorists', and we are reminded that these things are easily accessible or abundant in our environment, a depiction that has exploded on to the internet.The research we do is aiming to understand the brain processes that enable some people to avoid being distracted by these constant bombarding invitations to satisfy our urges and impulses. By strengthening our brain's ability to control ourselves, we stand a better chance of fulfilling our longer term goals (e.g. to maintain a healthy weight, control our addictions, be discerning when it comes to sex, lower anger and aggressive behaviour).
Here is some recommended reading:
1. To develop a neural circuitry model of vulnerability for methamphetamine (MA) addiction
2. To examine cognitive traits and deficits in those with and without MA addiction.
3. To correlate working memory training with brain structure and function in MA addiction.
Methamphetamine (MA) or “tik” is a highly addictive drug causing prevalent and rapidly growing health problems in Cape Town and throughout the world, high levels of personal suffering and a huge socio-economic burden.
Addiction and disordered eating behaviour, which share anti-social and self-harmful behaviours (e.g. anxiety, compulsive behaviour despite harm to self and others), are strongly linked at the neurobiological level, in that both involve vulnerabilities in top-down cognitive control combined with aberrant activation of reward brain regions. An imbalance between attempts at cognitive control and fluctuations in motivations to seek rewarding stimuli, likely leads to the development and maintenance of addictive behaviour (e.g. Everitt and Robbins, 2005; Alsiö et al., 2012, Fronters Neuroendocrinology; Volkow et al., 2011 Curr Top Beh Neuro).
New taxonomies are emerging, positing that the neurobiology of impulse control disorder (e.g. drug addiction, binge eating, ADHD) is an antipode between executive functioning in the prefrontal cortex and bottom-up reward impulsivity (Bickel et al., 2012 Psychopharmacology; Brooks et al., 2012 BMC Psychiatry; Robbins et al., 2012 Trends Cog Sci). Specifically, evidence is emerging that working memory (WM: the ability to ruminate on a cognitive strategy while avoiding irrelevant stimuli), which is linked to prefrontal cortex function, particularly in the dorsolateral (DLPFC) region, can help to lower impulsive behaviour by strengthening cognitive control (e.g. Bickel et al., 2011 Bio Psych).
It is suggested that the particular mechanism of action is a reduction in delay discounting, which in simple terms, is an ability to cognitively represent a delay in immediate gratification in favour of a future, often much delayed reward (Kurth-Nelson et al., 2012 Eur J NeuroSci).
Some recommended reading:
Neural connectivity and cognitive function in methamphetamine (MA) addiction using structural and functional brain imaging
Contingency Management and methamphetamine addiction in South Africa: examining neuroplasticity effects with fMRI.
Funded by National Institute on Drug Abuse (R21DA040492)
Prinicipal Investigator South Africa: Dr Samantha Brooks
With Professor Steve Shoptaw (UCLA PI), Dr Brooks (UCT PI) wrote a NIH Funded study into the effects of contingency management on neural processes of out-patients being treated for methamphetamine addiction in Cape Town, South Africa. Contingency Management is all about 'substitutability', that is to say, substituting the reward of obtaining methamphetamine with voucher rewards for providing consecutively clean urine samples over an 8 week period (3 x per week). Prof. Shoptaw has already published extenisively in this field to show that Contingency Management is an effective adjunct to boost treatment effects (e.g. Shoptaw et al., Drug & Alcohol Dependence, 78(2): 125-34). Additionally, those methamphetamine dependent individuals classified as high (versus low) responders during Contingency Management intervention have higher DA D2/D3 receptor availability (Martinez et al., 2011; Am J Psychiatry, 168; 634-641). Thus, the reward pathway (e.g. frontostriatal circuitry) is sensitive to reward responses during the intervention. During this project we will be the first to conduct brain imaging of contingency management in methamphetamine dependent individuals who are seeking treatment. And we are the first to conduct this research in South Africa, where we hope to eventually influence policy makers to improve treatment interventions for the high rate of methaphetamine abuse in Cape Town and internationally.
Adolescent alcohol use disorder (AUD) and brain structure / Fetal Alcohol Syndrome Disorder (FASD)
Funded by Alcohol Foundation, USA (ABMRF)
Prinicipal Investigator South Africa: Dr Samantha Brooks
Early life adversity, genetic factors and alcoholism are associated with reduced brain structural volumes in adolescents. The met allele of the BDNF val66met variant has been associated with decreased brain volumes and the development of cognitive dysfunction in adolescents. An interaction between environmental stressors and genotype may be linked to structural brain differences in individuals with alcohol use disorders (AUDs). We examined whether the BDNF p.Val66Met polymorphism interacts with levels of childhood trauma and is associated with alterations in brain volume in adolescents with AUDs. We are continuing our brain imaging research into adolescent alcohol use disorder by examining other Single Nucleotide Polymorphisms (SNPs) that are associated with gene x environment interactions underlying early life impulse control disorder. Additionally, we are starting a project in January 2014, to examine how maternal alcohol use is associated with brain changes in 6 year old children with Fetal Alcohol Syndrome.
Eating Disorders and brain
Background: Trait impulsivity and restraint are hypothesized to be predisposing factors for the development of an eating disorder. Aberrant neural responses to food stimuli have previously been reported in patients with fully developed eating disorders. We have investigated whether the traits correlate with anomalous neural activity in response to food stimuli in Swedish adolescents with an early diagnosis of an eating disorder.
Conclusions: Personality traits impulsivity and restraint can predict aberrant neural activation in EDNOS subjects. These findings demonstrate that both cognitive characteristics related to ED as well as abnormal neural response to food are present at an early stage in the disease. These measures can thus help with early identification of factors and trait levels which may dispose as risk factors for subsequent development of disordered eating behaviours and cognitions.
We are continuing this work by examining other neuropsychological variables and how they predict brain function, as well as genetic influences on early diagnoses of eating disorders.
Click here for more details of our work in Uppsala.
Some recommended reading:
Working memory training to improve attention in school children with and without ADHD/ADD
Working memory training in school children with attention deficit hyperactivity disorder in Cape Town, South Africa. With Western Cape Department of Education approval, we are currently conducting some fun studies in local grade 5 and 6 (approximately 11 years old) children before classes start each morning at 7.30am. We are running feasibility and efficacy studies in Cape Town to examine how children, parents and teachers think and feel about the working memory training. Questions we are asking include: does 8-weeks of working memory training improve behaviour inside and outside school? Does it improve concentration? Do the children's grades on school tests significantly improve? Does attention and self-confidence get better? Do the children like to play 15 minutes of working memory training to see how high they can go? What is the highest level (on the n-back task) children can achieve in 8-weeks in Cape Town? We will try to answer these questions in 3 local schools over the next year! Watch this space!
I am regularly asked to peer-review new articles by various editors in journals including most recently:
British Journal of Psychiatry
Clinical Psychology Review
Drug and Alcohol Dependence
Eating and Weight Disorders
European Journal of Eating Disorders
Frontiers in Human Neuroscience
Frontiers in Neuropsychoanalysis
Frontiers in Psychology
International Journal of Eating Disorders
Social Cognitive and Affective Neuroscience
Additionally, my students and I have written numerous systematic reviews and meta-analyses of brain imaging data (e.g. using Activation Likelihood Estimation (ALE). See below for a great paper by Simon Eickhoff and colleagues, providing guidelines on how to write excellent neuroimaging meta-analyses:
TEN SIMPLE RULES OF NEUROIMAGING META-ANALYSES