Our brains are always busy paying attention to the world around us, weeding out the information we need, and deciding what to do with that information. Quicker than we can notice, our brains orchestrate an enormous number of processes in a variety of areas.
In the visual cortex (at the back of our brain), we handle information from our eyes. Columbia neurosurgery resident, Dr. Chuck Mikell and his mentor neurosurgeon, Dr. Sameer Sheth have recently discovered something new about how our brains handle confusing visual information.
In Dr. Sheth’s lab, they found out that a part of this process happens in the area of the visual cortex called MT+. It plays a fundamental role in sorting out confusing visual information, especially as it relates to movement or spatial position.
To figure this out, the doctors got help from two patients whose epilepsy could not be managed with a regime of medication. For both patients, their epileptic seizures were thought to originate near regions of the visual cortex.
These patients had a grid of electrodes implanted over areas of the visual cortex. This kind of grid is normally used by neurosurgeons like Dr. Sheth to accurately locate the origin of the seizures. Doing so successfully and surgically removing that region can reduce or eliminate a patient’s seizures.
But for these two patients, the grid did something else, too. It recorded the patients’ normal, non-epileptic brain activity as they performed a specific task.
In each trial of the task, the patients looked at a group of three numbers, figured out which one was different from the other two, and pressed one of three buttons to indicate the identity of this unique number.
Some of the trials were relatively easy, and some were more challenging.
In an easy trial, the patients might see “020”: two is the unique number, and therefore the second button is the correct answer. In a harder trial, the patients might see “112”: 2 is still the unique number, and therefore the second button is still correct. The patients would have to ignore the distraction of the number 1’s (and avoid pressing the first button), and ignore the fact that the unique number is in the 3rd position (and avoid pressing the third button).
The harder tasks certainly require a little more thought. But where in the brain does this thought happen?
The doctors looked at the difference between the patients’ brain activity during the easy and hard trials. They found a difference in brain activity in area MT+. This difference in MT+ activity had happened well before the patient pressed the button–up to half a second beforehand.
Dr. Sheth and Dr. Mikell conclude that they have identified one of the areas of the brain dedicated to decoding confusing visual or spatial information. This confusing information is handled early on in visual processing. That way, the rest of the brain has plenty of time to plan its response.
The doctors presented their research to an international group of neurosurgeons and researchers at the 2014 annual meeting of the Congress of Neurological Surgeons. Their presentation was called “Spatial conflict is encoded in human MT+.”
Dr. Sheth and Dr. Mikell are grateful to the patients who took part in this study. As they participated in the treatment of their epilepsy, these patients also participated in research that will advance our understanding of how the brain works.
Dr. Sheth specializes in the treatment of patients with Movement Disorders, Epilepsy, Brain Tumors, Trigeminal Neuralgia, Brain Trauma, Hydrocephalus, and certain Psychiatric Disorders. He runs the Functional and Cognitive Neurophysiology Lab. Dr. Sheth is also a team member at the Epilepsy Center with Dr. Guy McKhann.
Related blogpost: Dr. Chuck Mikell Wins Resident Research Night For 2nd Time
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