Understanding the Brain

This past January, Cortex Journal, a leading scientific publication devoted to the study of cognition and mental processes via functional neuroimaging techniques, published an article surveying Dr. Yaara Erez’s research. The article covered a new discovery by Dr. Erez and her colleagues, an electrophysiological signature associated with cognitive activity in certain regions of the brain. “Our study found that high-frequency brainwave activity, the kind we call high gamma activity, was essentially used as a signature that identified areas of the brain associated with higher cognitive functions. We were able to spatially associate them with a network of cortical regions, known to be related to these functions,” shares Dr. Erez. “This is the first time we have been able to show that such a signature allows us to identify this particular brain network.”

Dr. Erez specializes in mapping brain functions and developing tools to help do so in the most precise manner, on an individual level. She conducts her research, which she started while at the University of Cambridge, on patients with cancerous brain tumors, but the procedure is just as relevant for other brain diseases. “We work with non-aggressive tumors, the kind that patients can live with for years post-diagnosis. Such tumors are currently not curable, but removing significant portions of their results in a much longer survival—as long as 15–20 years post-diagnosis. These tumors have a core, which should always be removed, when possible; but they also tend to spread to the healthy tissue around them, and this raises a dilemma: to remove or not, and if so, how much? Our goal is to remove as much of the tumor as we can, while still maintaining brain functions to ensure high quality of life for the patients and allow them to resume normal life,” she explains. “For that to happen, during the resection we perform a procedure called functional mapping, which we use to try and identify areas that are critical for specific functions. The surgeons decide as they go how much of the tumor to remove. In the lab, we develop methods and tools to improve functional mapping beyond the ones currently in use.”

The research reviewed in the Cortex article utilized a mapping method known as electrocorticography (ECOG), which records brain activity using electrodes placed on the patient’s exposed brain during the operation. “During the surgery, which is performed while the patient is fully awake and conscious, the patient is asked to perform tasks associated with different cognitive functions. We document their brain activity to identify the areas of the brain that are linked with these functions. This technique allows us to reach a very fine resolution of brain activity, with high resolution in both time and space. There is no non-invasive method available that provides this combination,” says Erez. “It’s important to stress that the research is done during operations already being performed for clinical purposes, and of course, at the patient’s consent.”

In her research, Dr. Erez focused on high cognitive functions such as processes of attention, problem-solving, multitasking, inference, and planning ahead. “In the brain, there are several areas in the cortex that are involved in all of these functions, and together make up a cortical network. This network is often damaged in patients after surgery, and current methods for functional mapping are insufficient when it comes to mapping the relevant regions and preventing damage,” she says. “Previous functional MRI (fMRI) studies have shown that this cortical network becomes more active as our cognitive effort rises; this is why we asked patients to perform two counting tasks of exceeding complexity while connected to electrodes that recorded the electrical activity in their brains during surgery. Our goal was to examine the differences in brain functions between the two tasks, as the cognitive effort increases.”

The signals were analyzed offline, and post-surgery, using computational methods and advanced signal processing algorithms to identify specific electrophysiological signatures associated with executive functions. Data analysis showed that not only was there an increase in high-frequency brainwave activity (high gamma) as the difficulty of the task increased—the study also successfully associated specific brain activity to a specific cortical network in the frontal cortex, on a spatial level. “This means that we will be able to use this method to identify which area of the brain is related to high executive functions on a personal level, i.e., the individual patient, and will eventually be able to provide surgeons with precise mapping of these areas, during surgery, so they could make clinical decisions regarding which parts of tissue can be resected without damaging those functions,” explains Dr. Erez.

The research team is cross-referencing their data with additional data acquired from the same patients using other imaging techniques such as fMRI, to see how this localized activity is related to the way distributed brain networks are organized in the entire brain. “Our goal is to produce reliable data at the individual level and provide clinicians with data for each specific patient. Eventually, we hope to provide feedback in real-time, during surgery,” she shares. “Up until now, we were doing our study at the University of Cambridge, but soon we will be starting a second phase at the Tel Aviv Sourasky Medical Center (Ichilov) and expand our questions to other tumors, additional brain functions, various brain systems, and different imaging techniques.”

Dr. Erez is seeking outstanding students to join innovative research at her lab. For inquiries, contact Dr. Erez at yaara.erez@biu.ac.il.