Introduction: The Nucleus Accumbens (NAc) is implicated in reward pathways regulating normal behavior, as well as in disease, such as addiction and OCD. Clinical experience suggests NAc stimulation is effective in treating disorders such as alcoholism and OCD. We describe our experience of stimulation in the vicinity of NAc in patients undergoing intracranial evaluation for epilepsy surgery and reward phenomena elicited.
Methods: Five patients with medically-refractory epilepsy were implanted with intracranial depth electrodes in the region of the NAc in order to localize ictal onset. Clinical functional mapping of brain regions was performed with currents from 1 mA to 4 mA. Patients’ behavior and subjective impressions during the stimulation sessions were videotaped. Connectivity of the NAc was quantified with DTI, resting-state fMRI, and cortico-cortical evoked potentials (CCEPs). We compared the anatomical locations of sites where NAc did not elicit reported sensations by determining each stimulus site’s stereotactic coordinates.
Results: In one of four patients, stimulation of the right NAc area resulted in reward phenomenology. These were reported as a “happy feeling like winning a lottery ticket with a small prize,” and other sensations. DTI, resting fMRI, and CCEPs demonstrated anatomical and functional connectivity between the stimulated site in the NAc area and distant cortical regions associated with complex pleasure sensations. Stimulated electrodes eliciting complex reward percepts were often within the white matter ventral to the NAc compared to sites where stimulation did not evoke percepts.
Conclusions: We report a novel instance in which stimulation of NAc as part of clinical evaluation for an epilepsy patient elicited complex sensations of reward. Our determination of the effective stimulus area’s stereotactic coordinates, in addition to our maps of NAc connectivity in this patient grant us better understanding of NAc connectivity with related cortical regions that may serve as targets for noninvasive stimulation for therapeutic benefit.
Patient Care: The use of DTI, fMRI, and CCEPs as a multimodal approach to characterizing the NAc aims to elucidate this deep brain nuclei for clinical applications and further research.
Learning Objectives: To recognize the use of DTI, fMRI, and CCEPs as tools for understanding the functional connectivity of deep brain nuclei in psychosurgical disease.
References: Rosen, L. G. (2015) ‘Molecular and neuronal plasticity mechanisms in the amygdala-prefrontal cortical circuit: implications for opiate addiction memory formation’, Frontiers in Neuroscience, Vol. 9, Article 399
Keller C. J. (2014). 'Mapping human brain networks with cortico-cortical evoked potentials', Philosophical Transactions of the Royal Society B, 369
Keller, C. J. (2014). 'Corticocortical evoked potentials reveal projectors and integrators in human brain networks', The Journal of Neuroscience, vol. 34, no. 27, pp. 9152-9163
Voges, J. (2013). 'Deep Brain Stimulation surgery for alcohol addiction', World Neurosurgery vol. 80, no.3/4: S28.E21-S28.E31
Heldmann, M. (2012). 'Deep Brain Stimulation of Nucleus Accumbens region in alcoholism affects reward processing', PLoS ONE vol. 7, no. 15, e36572
Berridge, K. C. (2008) ‘Affective neuroscience of pleasure: reward in humans and animals, Vol 199, No. 3, pp. 457-480
Neto, L. L. (2008) ‘The Human Nucleus Accumbens: Where is it? A stereotactic, anatomical, and magnetic resonance imaging study’, Neuromodulation, Vol. 11, No. 1, pp 13-22
Heath, R. G. (1972) ‘Pleasure and brain activity in man’, The Journal of Nervous and Mental Disease, Vol. 154, No. 1, pp. 3-18