Research themes
The main goal of the lab is to study the neurobiological basis of human decision-making. To do this, we study the decisions that people make while playing games – from simple choices under uncertainty (think lotteries) to complex social choices that require mentalizing about other people (think poker). Our studies are carried out in neurological and neurosurgical patients, which provide both unique opportunities to study the human brain invasively and also a strong motivation to understand how brain activity is damaged in brain pathologies.
Methods
- Behavioral testing: patients play computer games in which they make choices, which in turn allows us to study how they think: the strategies they use, their preferences, etc.
Long: - Computational modeling: computational models provide mathematical depictions of complex behavior, and provide quantitative metrics of cognition.
Long: - Invasive electrophysiological recordings: we leverage clinical interventions in which electrodes are implanted deep in the brain of neurosurgical patients.
Long: we work with patients that receive neurosurgical treatment for the diagnosis and treatment of their disease. The most common are intractable epilepsy patients and Parkinson’s disease patients. Epilepsy patients whose illness does not respond to medication are in some cases surgically implanted with electrodes to identify the focus of their epileptic seizures and to determine the best avenue of treatment. Parkinson’s disease patients are often implanted with Deep-Brain Stimulation (DBS) electrodes for the treatment of motor symptoms associated with the disease. In addition to their clinical benefits, these interventions provide a unique opportunity to record high temporal resolution (sub-ms), high signal-to-noise recordings of brain activity directly from neural tissue. We focus primarily on Local Field Potential (LFP) measures of brain activity, using time-frequency decomposition and related methods. New projects will also examine single-unit activity. Anatomical coverage is determined based on clinical needs, and varies from patient to patient, especially in epilepsy patients, but we focus primarily in brain regions implicated in decision-making (orbitofrontal, ventromedial, lateral prefrontal and cingulate cortices, amygdala, hippocampus and basal ganglia among others). - Brain stimulation studies: the surgical implantation of electrodes opens the door to anatomically precise electrical stimulation. This is carried out routinely in DBS patients, and often in surgical epilepsy patients (for functional mapping), for clinical treatment and diagnosis. But it also opens the door to causal studies of the involvement of different brain areas in behavior, while an area can be electrically stimulated with a specific pattern (timing, frequency) to understand how modulated activity impacts behavior. More long-term, stimulation can be used as a therapeutical tool to treat brain disorders.
- Lesion studies: we work with patients that have suffered focal brain lesions to study how their behavior is affected. UCDMD serves a variety of patients with focal brain lesions, including traumatic brain injury, stroke and tumor resection patients. These provide a unique opportunity to gather causal knowledge of the contribution of different brain areas to behavior – beyond correlative approaches that necessarily form the majority of human neuroscience. For example, an abundance of non-invasive studies show that the orbitofrontal cortex is implicated in decision-making – by studying patients with a damaged orbitofrontal cortex make decisions we can know exactly what the contribution of this brain area is to that specific facet of behavior.
- Machine learning approaches: we use ML to generate decoding models that allow us to interpret multi-dimensional brain activity.
Projects
There are a variety of projects ongoing in the lab. The two main ones are:
- iEEG recordings during decision-making under uncertainty. Following up on our previous results (see Papers section), we are working to characterize the neural basis of human decision-making under uncertainty. Specifically, we seek to examine the relationship between neural activity in different frequency bands and brain regions and overt choice behavior using a combination of invasive recordings, neuroeconomic probes of decision, and machine learning decoding methods.
- DBS recordings and stimulation during impulsive decision-making. Parkinson’s Disease (PD) patients often develop impulsive/compulsive behavior as an unintended consequence of their treatment. In this project, we seek to understand the neurobiological basis of impulsive behavior and the ability of targeted neurostimulation to treat these cognitive deficits. We intraoperatively record electrophysiological activity from the STN of PD patients while they carry out an inter-temporal decision-making game. In the future, this will be complemented with STN stimulation.
Collaborators
Basic research in a clinical setting is eminently collaborative, and we operate in close coordination with our clinical colleagues in the medical center. In addition, we have collaborative research projects with a number of researchers within UC Davis and in other institutions, some of which are listed below:
- Kia Shahlaie (UC Davis Neurological Surgery) is a functional neurosurgeon leading the clinical aspects of our invasive research.
- Lara Zimmerman (UC Davis Neurological Surgery): Dr. Zimmerman co-directs the neurocritical care unit at UCD NS. Together, we are working to carry out cognitive studies in focal lesion patients.
- Moxon lab (UC Davis Biomedical Engineering): joint efforts on decoding neural activity from multi-site iEEG recordings.
- Knight lab (UC Berkeley): multiple projects.
- Lin lab (UC Irvine Neurology)
- Chang lab (UCSF Neurosurgery)
- Girgis lab (U Calgary)
- Ranganath lab (UC Davis)
- O’Reilly lab (UC Davis)
- Ekstrom lab (U. Arizona)