After taking an undergraduate Neuropsychology course at Rutgers University, I was exposed to a series of anatomical networks associated with learning, reward, and motivation. My interests soon became focused on how networks responsible for learning translate reward and motivation into action. It became apparent that this question is relevant not only in the context of experience-dependent changes that occur naturally, but also circumstances in which acute drug use transitions into abuse. This motivated me to learn about the characterizations of addiction in the uncompromised brain just as well as the impaired or diseased brain.
Working under Dr. Kunal Gandhi in the UMDMJ Division of Addiction Psychiatry, I learned about the relationship between mental illness and addiction. Research in this clinic focused on treatments for chronic smokers with Schizophrenia. People with Schizophrenia motivated clinical testing because they tend to smoke at higher rates (Lasser et al., 2000; de Leon and Diaz, 2005), have lower cessation rates (Lasser et al., 2000; Covey et al., 1994), and they suffer increased cardiovascular and respiratory diseases as well as reduced life expectancy in comparison to the general population with no mental illness (Curkendall et al., 2004; Brown et al.,2000; Capasso et al., 2008). These outcomes are linked to greater nicotine intake per cigarette exhibited by higher levels of nicotine and continin, a nicotine metabolite (Olincy et al., 1997; Williams et al., 2005, 2010). Increases in serum nicotine levels seem to be a result of altered puffing behavior in these patients, which is defined as a shorter inter-puff interval compared to matched controls after a 24 hour smoke period (Williams et al., 2011). According to Patterson and colleagues (2003), the larger “nicotine boost” may be linked to increased addictive potential and susceptibility for relapse after a quit attempt. Therefore, the goal of clinical testing was to measure the efficacy of nicotine nasal sprays (NNS) as a treatment for chronic smokers with Schizophrenia. Results demonstrated that many patients remained abstinent or significantly reduced their smoking since NNS could be self-administered to optimally titrate nicotine dosage (Williams and Gandhi, 2009). NNS treatment is beneficial in patients with schizophrenia because nicotine transiently normalizes auditory (P50) gating mechanisms caused by poor inhibition of nicotinic alpha- 7 receptors on GABA-B interneurons (Adler et al., 1993; 2008; Freedman et al. 1997). Because defective auditory gating is responsible for hallucinations, use of nicotine nasal sprays allow for improvements cognitive functioning without the health issues caused by smoking. This experience displays the advantages of addictive substances as treatment for the diseased brain without compromising health. Most importantly, this research brings hope for the possibility of treating other conditions affected by deficiencies in the cholinergic system, such as Alzheimers Dementia and Parkinson's disease.
Electrophysiological Research in Motor and Limbic Systems
In Dr. Mark West’s laboratory, I learned about how mesolimbic and motorlimbic structures engage during chronic cocaine self-administration in naive rats. This provided me with an understanding of the functional adaptations within these structures in addition to behavioral changes while acquiring an addiction. Responsible for primarily reward, motivation, and action, mesolimbic systems are implicated in acquisition of drug-seeking/taking and habit formation (Belin & Everitt, 2008; Everitt & Robbins, 2005). These behaviors are driven by Dopamine (DA) reward signalling between the Substantia Nigra pars Compacta (SNc) and Nucleus Accumbens (NAcc), and trigger action plans in Premotor/Motor/Sensory Cortices (M1/S1) via motor thalamus (Alexander et al., 1986; Haber et al., 2003; Yin et al., 2008).
Because the NAcc is involved in reward signalling and approach behavior, the Ventral Pallidum (VP) provides a representation of drug-seeking behavior (Root et al., 2012). The Dorsolateral striatum (DLS) is also a crucial component in the mesolimbic system because it receives a somatopic map from M1&S1 and is responsible for representation and initiation of movement of individual body parts in primates (Crutcher & Delong, 1984; Liles, 1985) and rodents (West et al., 1990 Carelli and West, 1991).The nucleus accumbens shell has been shown to discriminate cocaine associated stimuli while the core may be involved in drug-seeking or responding (Ghitza et al, 2003, 2004).
Working closely with Dr. David Root, I helped investigate drug-seeking behavior in rodents during chronic cocaine self-administration. 16 microwire electrodes were implanted into VP subregions, the ventromedial VP (VPvm) and the dorsolateral (VPdl), to record the activity of single neurons. Because of the functional differences in accumbens subregions and its connectivity to VP, the goal of the experiment was to determine the influence of these structures on firing activity in the subregions of the VP during 3 time epochs: approaching, responding, and retreating away from the vertical head movement operant device. Results demonstrated that the Ventral Pallidum (VP) increased its firing rate during drug seeking behaviors (i.e. approach, response, and retreat away from the vertical head movement device). However, these firing patterns differed between dorsolateral (VPdl) and ventromedial (VPvm) subregions of the ventral pallidum (Root et al., 2012). It is suspected that nucleus accumbens core projections to VPdl drives representation of the approach behavior towards the cocaine-rewarded operant.
My reflection of my involvement in these research projects has led me to understand that addiction does not discriminate, it can plague anyone. Furthermore, this my work has inspired my own personal journey into other avenues of Psychology. I realized that I want to keep growing and learning using my background in research to support my new goals. I would like to invite others to share their own personal theories or research in Clinical Psychology, Cognitive Science or Behavioral Neuroscience.