Bio

Institute Affiliations


  • Member, Maternal & Child Health Research Institute (MCHRI)

Professional Education


  • Doctor of Medicine, Dartmouth College (2015)
  • Doctor of Philosophy, Dartmouth College (2013)
  • Bachelor of Science, Massachusetts Institute of Technology (2008)
  • Post-doctoral Fellowship, Stanford University, Neuroscience
  • Residency, Stanford University, Psychiatry

Publications

All Publications


  • Emotion Network Predictors of Clinical Outcome in Youth at High Risk for Bipolar Disorder Singh, M., Nimarko, A., Leslie, S., Fischer, A. ELSEVIER SCIENCE INC. 2019: S2
  • Reward-circuit biomarkers of risk and resilience in adolescent depression JOURNAL OF AFFECTIVE DISORDERS Fischer, A. S., Ellwood-Lowe, M. E., Colich, N. L., Cichocki, A., Ho, T. C., Gotlib, I. H. 2019; 246: 902–9
  • Reward-circuit biomarkers of risk and resilience in adolescent depression. Journal of affective disorders Fischer, A. S., Ellwood-Lowe, M. E., Colich, N. L., Cichocki, A., Ho, T. C., Gotlib, I. H. 2019; 246: 902–9

    Abstract

    Dysfunctional reward processing is a core feature of major depressive disorder. While there is growing knowledge of reward processing in adolescent depression, researchers have ignored neural mechanisms of resilience to depression. Here, we examine neural correlates of reward processing that characterize resilience and risk in adolescents at risk for depression, facilitating the development of effective intervention approaches that strengthen resilience to psychopathology in at-risk youth.50 adolescent females were followed through age 18: 32 at-risk adolescents who either did (remitted-depressed; n = 15) or did not (resilient; n = 17) experience a depressive episode, and 18 low-risk healthy controls. Participants completed clinical assessments at 18-month intervals and an fMRI reward-processing task in late adolescence. We conducted predictive modeling with a priori reward regions of interest (ROIs).At-risk resilient and remitted-depressed adolescents exhibited less striatal activation than did controls during anticipation of reward. Resilient adolescents exhibited greater activation than did remitted-depressed adolescents in the middle frontal gyrus during reward anticipation, and less activation in the superior frontal gyrus and cuneus during processing of reward outcome. Using predictive modeling, ventral anterior cingulate cortex and putamen activation during reward processing distinguished resilient from remitted-depressed adolescents with 83% accuracy.The relatively small sample size of only females and the fact that fMRI data were obtained at one time point in late adolescence are limitations.Distinct patterns of neural activation in reward circuitry appear to be markers of risk and resilience that may be targets for prevention and treatment approaches aimed at strengthening adaptive reward processing in at-risk adolescents.

    View details for PubMedID 30795497

  • Neural Markers of Resilience in Adolescent Females at Familial Risk for Major Depressive Disorder JAMA PSYCHIATRY Fischer, A. S., Camacho, C., Ho, T. C., Whitfield-Gabrieli, S., Gotlib, I. H. 2018; 75 (5): 493–502

    Abstract

    Adolescence is a neurodevelopmental period during which experience-dependent plasticity in brain circuitry may confer vulnerability to depression as well as resilience to disorder. Little is known, however, about the neural mechanisms that underlie resilience during this critical period of brain development.To examine neural functional connectivity correlates of resilience in adolescent females at high and low familial risk for depression who did and did not develop the disorder.A longitudinal study was conducted at Stanford University from October 1, 2003, to January 31, 2017. Sixty-five female adolescents participated in the study: 20 at high risk in whom depression did not develop (resilient), 20 at high risk in whom depression developed (converted), and 25 at low risk with no history of psychopathology (control).We compared functional connectivity between resilient and converted, and between resilient and control, adolescent females using voxelwise 2-sided t tests to examine neural markers of resilience to depression as the main outcomes of interest. Specifically, we assessed differences in connectivity of the limbic (amygdala seed), salience (anterior insula seed), and executive control (dorsolateral prefrontal cortex seed) networks, implicated in emotion regulation. We also examined the association between functional connectivity and life events.Of the 65 participants (mean [SD] age, 18.9 [2.5] years), adolescent females in the resilient group had greater connectivity between the amygdala and orbitofrontal cortex (z score = 0.23; P < .001) and between the dorsolateral prefrontal cortex and frontotemporal regions (z score = 0.24; P < .001) than did converted adolescent females. In adolescent females in the resilient group only, strength of amygdala-orbitofrontal cortex connectivity was correlated with positive life events (r18 = 0.48; P = .03). Resilient adolescent females had greater connectivity within frontal (z score = 0.07; P < .001) and limbic (z score = 0.21; P < .001) networks than did control individuals. Both high-risk groups had greater salience network connectivity: the converted group had greater intranetwork connectivity than did the resilient (z score = 0.13; P < .001) and control (z score = 0.10; P < .001) groups, and the adolescent females in the resilient group had greater salience network connectivity with the superior frontal gyrus than did the converted (z score = 0.24; P < .001) adolescent females.Resilient adolescent females have compensatory functional connectivity patterns in emotion regulatory networks that correlate with positive life events, suggesting that experience-dependent plasticity within these networks may confer resilience to depression. Further studies are warranted concerning connectivity-associated targets for promoting resilience in high-risk individuals.

    View details for PubMedID 29562053

    View details for PubMedCentralID PMC5875355

  • Understanding marijuana's effects on functional connectivity of the default mode network in patients with schizophrenia and co-occurring cannabis use disorder: A pilot investigation SCHIZOPHRENIA RESEARCH Whitfield-Gabrieli, S., Fischer, A. S., Henricks, A. M., Khokhar, J. Y., Roth, R. M., Brunette, M. F., Green, A. I. 2018; 194: 70–77

    Abstract

    Nearly half of patients with schizophrenia (SCZ) have co-occurring cannabis use disorder (CUD), which has been associated with decreased treatment efficacy, increased risk of psychotic relapse, and poor global functioning. While reports on the effects of cannabis on cognitive performance in patients with SCZ have been mixed, study of brain networks related to executive function may clarify the relationship between cannabis use and cognition in these dual-diagnosis patients. In the present pilot study, patients with SCZ and CUD (n=12) and healthy controls (n=12) completed two functional magnetic resonance imaging (fMRI) resting scans. Prior to the second scan, patients smoked a 3.6% tetrahydrocannabinol (THC) cannabis cigarette or ingested a 15mg delta-9-tetrahydrocannabinol (THC) pill. We used resting-state functional connectivity to examine the default mode network (DMN) during both scans, as connectivity/activity within this network is negatively correlated with connectivity of the network involved in executive control and shows reduced activity during task performance in normal individuals. At baseline, relative to controls, patients exhibited DMN hyperconnectivity that correlated with positive symptom severity, and reduced anticorrelation between the DMN and the executive control network (ECN). Cannabinoid administration reduced DMN hyperconnectivity and increased DMN-ECN anticorrelation. Moreover, the magnitude of anticorrelation in the controls, and in the patients after cannabinoid administration, positively correlated with WM performance. The finding that DMN brain connectivity is plastic may have implications for future pharmacotherapeutic development, as treatment efficacy could be assessed through the ability of therapies to normalize underlying circuit-level dysfunction.

    View details for PubMedID 28823723

  • Looking at the Brighter Side: Functional Connectivity Biomarkers of Resilience to Adolescent Depression in Emotion Regulation Networks Fischer, A., Camacho, M., Ho, T., Whitfield-Gabrieli, S., Gotlib, I. NATURE PUBLISHING GROUP. 2017: S501
  • Functional Connectivity Markers of Resilience in Adolescents at Familial Risk for Depression Fischer, A., Camacho, C., Ho, T., Whitfield-Gabrieli, S., Gotlib, I. NATURE PUBLISHING GROUP. 2016: S470–S471
  • The Clinical Applicability of Functional Connectivity in Depression: Pathways Toward More Targeted Intervention. Biological psychiatry. Cognitive neuroscience and neuroimaging Fischer, A. S., Keller, C. J., Etkin, A. 2016; 1 (3): 262–70

    Abstract

    Resting-state functional magnetic resonance imaging provides a noninvasive method to rapidly map large-scale brain networks affected in depression and other psychiatric disorders. Dysfunctional connectivity in large-scale brain networks has been consistently implicated in major depressive disorder (MDD). Although advances have been made in identifying neural circuitry implicated in MDD, this information has yet to be translated into improved diagnostic or treatment interventions. In the first section of this review, we discuss dysfunctional connectivity in affective salience, cognitive control, and default mode networks observed in MDD in association with characteristic symptoms of the disorder. In the second section, we address neurostimulation focusing on transcranial magnetic stimulation and evidence that this approach may directly modulate circuit abnormalities. Finally, we discuss possible avenues of future research to develop more precise diagnoses and targeted interventions within the heterogeneous diagnostic category of MDD as well as the methodological limitations to clinical implementation. We conclude by proposing, with cautious optimism, the future incorporation of neuroimaging into clinical practice as a tool to aid in more targeted diagnosis and treatment guided by circuit-level connectivity dysfunction in patients with depression.

    View details for PubMedID 29560882

  • Response to "Cortico-accumbens circuitry in schizophrenia: Merely a reward system?" by Rolland and Jardri (SCHRES-14-D-00731) SCHIZOPHRENIA RESEARCH Fischer, A. S., Whitfield-Gabrieli, S., Roth, R. M., Brunette, M. F., Green, A. I. 2015; 161 (2-3): 519-519

    View details for DOI 10.1016/j.schres.2014.10.008

    View details for Web of Science ID 000348452100060

    View details for PubMedID 25465412

    View details for PubMedCentralID PMC4785886

  • Impaired functional connectivity of brain reward circuitry in patients with schizophrenia and cannabis use disorder: Effects of cannabis and THC SCHIZOPHRENIA RESEARCH Fischer, A. S., Whitfield-Gabrieli, S., Roth, R. M., Brunette, M. F., Green, A. I. 2014; 158 (1-3): 176-182

    Abstract

    Cannabis use disorder (CUD) occurs in up to 42% of patients with schizophrenia and substantially worsens disease progression. The basis of CUD in schizophrenia is unclear and available treatments are rarely successful at limiting cannabis use. We have proposed that a dysregulated brain reward circuit (BRC) may underpin cannabis use in these patients. In the present pilot study, we used whole-brain seed-to-voxel resting state functional connectivity (rs-fc) to examine the BRC of patients with schizophrenia and CUD, and to explore the effects of smoked cannabis and orally administered delta-9-tetrahydrocannabinol (THC) on the BRC. 12 patients with schizophrenia and CUD and 12 control subjects each completed two fMRI resting scans, with patients administered either a 3.6% THC cannabis cigarette (n=6) or a 15 mg THC capsule (n=6) prior to their second scan. Results revealed significantly reduced connectivity at baseline in patients relative to controls, with most pronounced hypoconnectivity found between the nucleus accumbens and prefrontal cortical BRC regions (i.e., anterior prefrontal cortex, orbitofrontal cortex, and anterior cingulate cortex). Both cannabis and THC administration increased connectivity between these regions, in direct correlation with increases in plasma THC levels. This study is the first to investigate interregional connectivity of the BRC and the effects of cannabis and THC on this circuit in patients with schizophrenia and CUD. The findings from this pilot study support the use of rs-fc as a means of measuring the integrity of the BRC and the effects of pharmacologic agents acting on this circuit in patients with schizophrenia and CUD.

    View details for DOI 10.1016/j.schres.2014.04.033

    View details for Web of Science ID 000341314800029

    View details for PubMedID 25037524

    View details for PubMedCentralID PMC4778557

  • Predicting inpatient complications from cerebral aneurysm clipping: the Nationwide Inpatient Sample 2005-2009 JOURNAL OF NEUROSURGERY Bekelis, K., Missios, S., MacKenzie, T. A., Desai, A., Fischer, A., Labropoulos, N., Roberts, D. W. 2014; 120 (3): 591-598

    Abstract

    Precise delineation of individualized risks of morbidity and mortality is crucial in decision making in cerebrovascular neurosurgery. The authors attempted to create a predictive model of complications in patients undergoing cerebral aneurysm clipping (CAC).The authors performed a retrospective cohort study of patients who had undergone CAC in the period from 2005 to 2009 and were registered in the Nationwide Inpatient Sample (NIS) database. A model for outcome prediction based on preoperative individual patient characteristics was developed.Of the 7651 patients in the NIS who underwent CAC, 3682 (48.1%) had presented with unruptured aneurysms and 3969 (51.9%) with subarachnoid hemorrhage. The respective inpatient postoperative risks for death, unfavorable discharge, stroke, treated hydrocephalus, cardiac complications, deep vein thrombosis, pulmonary embolism, and acute renal failure were 0.7%, 15.3%, 5.3%, 1.5%, 1.3%, 0.6%, 2.0%, and 0.1% for those with unruptured aneurysms and 11.5%, 52.8%, 5.5%, 39.2%, 1.7%, 2.8%, 2.7%, and 0.8% for those with ruptured aneurysms. Multivariate analysis identified risk factors independently associated with the above outcomes. A validated model for outcome prediction based on individual patient characteristics was developed. The accuracy of the model was estimated using the area under the receiver operating characteristic curve, and it was found to have good discrimination.The featured model can provide individualized estimates of the risks of postoperative complications based on preoperative conditions and can potentially be used as an adjunct in decision making in cerebrovascular neurosurgery.

    View details for DOI 10.3171/2013.8.JNS13228

    View details for Web of Science ID 000332048800002

    View details for PubMedID 24032701

  • Teaching the Bayesian child: Three-and-a-half-year-olds’ reasoning about ambiguous evidence Journal of Cognition and Development Bonawitz, E. B., Fischer, A. S., Schulz, L. E. 2012; 13 (2): 266-280
  • Teaching three-and-a-half-year-olds to reason about ambiguous evidence Psychology Press Bonawitz, E. B., Fischer, A. S., Schulz, L. E. 2011