Director, Motivated Learning & Memory Laboratory
Assistant Professor, Department of Psychiatry
McLean Hospital/Harvard Medical School
Center for Depression, Anxiety and Stress Research
de Marneffe Building, Room 244
I am a cognitive neuroscientist focused on investigating learning and memory in the context of psychiatric illness, with an emphasis on unipolar depression. I completed my doctoral research under the supervision of Dr. Kevin LaBar at Duke University in 2006, receiving my Ph.D. in Psychology & Neuroscience. As a graduate student, I studied emotion regulation and emotional memory in healthy participants using a variety of behavioral, psychophysiological, and electrophysiological methods. In fall 2006, I joined the Department of Psychology at Harvard University as a post-doctoral fellow working with Dr. Diego Pizzagalli. In 2010, Dr. Pizzagalli moved to McLean Hospital to form the Center for Depression, Anxiety and Stress Research (CDASR), which I joined. Together with many talented colleagues, Dr. Pizzagalli and I conducted functional magnetic resonance imaging (fMRI) studies of reward processing in adults who were depressed or at elevated risk of depression (e.g., due to childhood treatment). These studies were among the first to show that depression (and risk for depression) is associated with blunted responses to rewards and reward-predicting cues in the basal ganglia, prominently including aspects of the dorsal and ventral striatum (caudate, nucleus accumbens). These results suggested that a clinically important aspect of unipolar depression—namely, anhedonia—reflects dysfunction in brain reward circuitry.
In 2014, I was promoted to Assistant Professor and launched the Motivated Learning & Memory Laboratory, which is located in CDASR at McLean Hospital. The lab is currently focused on two topics. First, we are investigating depression from the perspective of reinforcement learning. Reinforcement learning encompasses a wide variety of algorithms that agents can use to make decisions and select actions in the service of desired goals. It is an ideal platform from which to examine depression, because it provides quantitative methods for assessing cognitive processes that are dysfunctional in depression (e.g., problem-solving, decision-making), and because it is clear from basic work that reinforcement learning is mediated by basal ganglia circuits—precisely the circuits in which we previously identified blunted responses in depression. Thus, we expect to uncover evidence of reinforcement learning deficits in depression, and we will combine fMRI with computational modeling in order to precisely characterize the nature of those deficits at both the psychological and neural levels.
Second, we are taking a novel approach to episodic memory deficits in depression. Most prior work on episodic (or “declarative”) memory in this area has emphasized the fact that memory for negative material is often enhanced in depressed individuals. However, several studies also point to diminished recall of positive material in depression, and in a prior study we provided evidence that this effect may be due to blunted responding in the dopaminergic midbrain as memories are being formed. To test this hypothesis more stringently, we are embarking on a large fMRI study of depressed and healthy adults in which the activation of dopaminergic neurons will be manipulated during memory encoding. We expect to uncover evidence of blunted dopamine responses in depressed adults, and we anticipate that this will be linked to weak memory formation and thus poor memory performance in the depressed group relative to the healthy group. If this work is successful, it will provide an important complement to studies of enhanced memory for negative material by detailing mechanisms by which memory for positive material is impaired in depression.
These studies and related projects are being conducted with outstanding collaborators both within and outside McLean Hospital. In particular, Dr. Michael Frank and his laboratory at Brown University have been instrumental with respect to my training in computational modeling. All of this work is possible because of generous support from McLean Hospital, the Brain and Behavior Research Foundation (formerly NARSAD), and grants from the National Institute of Mental Health.
Dillon, D. G., Dobbins, I. G., & Pizzagalli, D. A. (2013). Weak reward source memory in depression reflects blunted activation of VTA/SN and parahippocampus. Soc Cogn Affect Neurosci, doi:10.1093/scan/nst155
Treadway, M. T., Waskom, M. L., Dillon, D. G., Holmes, A. J., Park, M. T. M., Chakravarty, M. M., Dutra, S. J., Polli, F. E., Iosifescu, D. V., Fava, M., Gabrieli, J. D. E., Pizzagalli, D. A. (2014). Illness progression, recent stress and morphometry of hippocampal subfields and medial prefrontal cortex in major depression. Biol Psychiatry.
Admon, R., Nickerson, L. D., Dillon, D. G., Holmes, A. J., Bogdan, R., Kumar, P., Dougherty, D. D., Iosifescu, D. V., Mischoulon, D., Fava, M., & Pizzagalli, D. A. (2014). Dissociable cortico-striatal connectivity abnormalities in major depression in response to monetary gains and penalties. Psychol Med.
Dillon, D. G., Rosso, I. M., Pechtel, P., Killgore, W. D. S., Rauch, S. L., & Pizzagalli, D. A. (2014). Peril and pleasure: an RDoC-inspired examination of threat responses and reward processing in anxiety and depression. Depress Anxiety, 31, 233-249.
Dillon, D. G., & Pizzagalli, D. A. (2013). Evidence of successful modulation of brain activation and subjective experience during reappraisal of negative emotion in unmedicated depression. Psychiatry Res, 212, 99-107.
Vanderhasselt, M. A., De Raedt, R., Dillon, D. G., Dutra, S. J., Brooks, N., Pizzagalli, D. A. (2012). Decreased cognitive control in response to negative information in remitted depression: an event-related potential study. J Psychiatry Neurosci, 37, 250-258.
Pizzagalli, D. A., Dillon, D. G., Bogdan, R., & Holmes, A. J. (2011). Reward and punishment processing in the human brain: clues from affective neuroscience and implications for depression research. In O. Vartanian & D. R. Mandel (Eds.), Neuroscience of Decision Making (pp. 199-220). New York: Psychology Press.
Dillon, D. G., Deveney, C. M., & Pizzagalli, D. A. (2011). From basic processes to real-world problems: How research on emotion and emotion regulation can inform understanding of psychopathology, and vice versa. Emot Rev, 3, 74-82.
Dillon, D. G., & Pizzagalli, D. A. (2010). Maximizing positive emotions: a translational, transdiagnostic look at positive emotion regulation. In A. M. Kring & D. M. Sloan (Eds.), Emotion Regulation and Psychopathology. New York: Guilford Press.
Dillon, D. G.*, Bogdan, R. H., Fagerness, J., Holmes, A. J., Perlis, R. H., & Pizzagalli, D. A. (2010). Variation in TREK1 gene linked to depression-resistant phenotype is associated with potentiated neural responses to rewards in humans. Hum Brain Mapp, 31, 210-221.
Dillon, D. G., Holmes, A. J., Birk, J. L., Brooks, N., Lyons-Ruth, K., & Pizzagalli, D. A. (2009). Childhood adversity is associated with left basal ganglia dysfunction during reward anticipation. Biol Psychiatry, 66, 206-213.
Pizzagalli, D. A., Holmes, A. J., Dillon, D. G., Goetz, E. L., Birk, J. L., Bogdan, R., Dougherty, D. D., Iosifescu, D. V., Rauch, S. L., & Fava, M. (2009). Reduced caudate and nucleus accumbens response to rewards in unmedicated subjects with Major Depressive Disorder. Am J Psychiatry, 166, 702-710.
Wacker, J., Dillon, D. G., & Pizzagalli, D. A. (2009). The role of the nucleus accumbens and rostral anterior cingulate cortex in anhedonia: Integration of resting EEG, fMRI, and volumetric techniques. Neuroimage, 46, 327-337.
Santesso, D. L., Dillon, D. G., Birk, J. L., Holmes, A. J., Goetz, E., Bogdan, R., & Pizzagalli, D. A. (2008). Individual differences in reinforcement learning: Behavioral, electrophysiological, and neuroimaging correlates. Neuroimage, 42, 807-816.
Dillon, D. G., Holmes, A. J., Jahn, A. L., Bogdan, R., Wald, L. L., & Pizzagalli, D. A. (2008). Dissociation of neural regions associated with anticipatory versus consummatory phases of incentive processing. Psychophysiology, 45, 36-49.
Dillon, D. G., & Pizzagalli, D. A. (2007). Inhibition of action, thought, and feeling: A selective neurobiological review. Appl Prev Psychol, 12, 99-114.
Dillon, D. G., Ritchey, M., Johnson, B. D., & LaBar, K. S. (2007). Dissociable effects of conscious emotion regulation strategies on explicit and implicit memory. Emotion, 7, 354-365.
Dillon, D. G., Cooper, J. J., Grent-t’-Jong, T., Woldorff, M. G., & LaBar, K. S. (2006). Dissociation of event-related potentials indexing arousal and semantic cohesion during emotional word encoding. Brain Cogn, 62, 43-57.
Dillon, D. G., & LaBar, K. S. (2005). Startle modulation during conscious emotion regulation is arousal-dependent. Behav Neurosci, 119, 1118-1124.
Fichtenholtz, H. M., Dean, H. L., Dillon, D. G., Yamasaki, H., McCarthy, G., & LaBar, K. S. (2004). Emotion-attention network interactions during a visual oddball task. Cogn Brain Res, 20, 67-80.
*The first two authors made equal contributions to this manuscript.