Looking for Consciousness: A Novel Functional Neuroimaging Approach for Detection of Visual Cognition in Patients with Severe TBI and Disorders of Consciousness
PI: Joseph T. Giacino, PhD
Co-PI: Emily Stern, MD
Spaulding-Harvard TBI Model System
The TBIMS has enabled a multi-disciplinary team of experts in disorders of consciousness and neuroimaging to develop new ways of using advanced fMRI in patients with disorders of consciousness (DOC). The over-arching goal is to enable a hierarchical cognitive evaluation of these patients, including assessment of their ability to follow commands and to communicate, without the need for overt behavioral responses. This is critically important, particularly in persons who retain conscious awareness but are believed to be unconscious based on routine clinical examination.
This project compares: 1) traditional neurobehavioral assessment methods of measuring consciousness using the Coma Recovery Scale-Revised (CRS-R) and 2) family beliefs of the same with the novel neuroimaging techniques that we are developing. The development of our fMRI paradigms builds upon previous work in the field which assesses function of anatomically dissociable cognitive processes. By specifically engaging in one of these processes, we are investigating whether the resulting pattern of brain activity can confirm that the patient is able to understand and perform the task, verifying the ability to follow commands. By linking each process with a yes/no response, the pattern of activity associated with that cognitive process can act as a proxy for a yes/no response. For example, if the patient is told to look at the word “Yes” if the answer to a question (such as “Is your name Jack?”) is yes, then observation of a brain pattern associated with reading the word, “Yes,” (as opposed to other patterns of brain activity) demonstrates that the patient is answering the question correctly.
The major advance over previous neuroimaging work that we are striving for is to employ tasks that are easier to manage for persons who have experienced severe acquired brain injury. We expect that the availability of standardized neurobehavioral and neuroimaging findings, coupled with the family’s observations, will inform the clinician’s judgment concerning command-following and communication ability.
This project is focused on persons with disorders of consciousness, with the primary goal of developing a robust, objective method to detect conscious awareness in persons with severe impairments in speech and motor function. This approach may also improve differential diagnostic accuracy (i.e., minimally conscious state vs. vegetative state), which is important in establishing prognosis and predicting outcomes. These findings will be compared to those in persons with severe brain injury who retain evidence of conscious awareness and with healthy subjects.
What Does the Subject/Patient Do in the Scanner?
Each participant is exposed to a range of stimuli that assess whether s/he is able to
- Perceive stimuli (both visual and auditory)
- Process the information presented in these stimuli
- Follow a simple command (such as “Look at the picture”)
- Answer a Yes/No question
Whether or not the task is performed is determined based upon processing, analysis and interpretation of the brain imaging data (see below).
fMRI Tool Development
This project has benefited from ongoing methodological development in several realms:
- The neuropsychological task battery that is used in the fMRI scanner was iteratively optimized on healthy subjects, to ensure its performance in patient populations.
- Advanced image processing tools, that can account for potential marked abnormalities in brain structure, due to injury, have been implemented.
- The Functional Neuroimaging Laboratory at BWH has been developing advanced multivariate image analysis methods for many years. These have been implemented in a specific, project-driven manner to interrogate the data generated from the healthy subject group, individual healthy subjects, and individual patients. Some resulting tools include
- A functional atlas of the human eye movement network (Functional Neuroanatomy of the Human Eye Movement Network: A Review and Atlas, submitted).
- A multivariate classification analysis tool, that can assess whether subjects are performing each task correctly, in an objective manner. The implementation of this method has been optimized to detect brain activity associated with the neuropsychological tasks developed for this project. A resulting atlas of these specific regions of interest is also currently under development.
For More Information
For additional information about the TBIMS, please click here.