It was widely used until about 2000 to classify a patient's level of consciousness, but Schnakers says it may contribute to misdiagnosis.

CNN: Trapped 'coma' man: How was he misdiagnosed?

The case has highlighted the difficulties doctors face when trying to diagnose the level of consciousness of a patient in a coma-like state.

CNN: Trapped 'coma' man: How was he misdiagnosed?

The prefrontal cortex has enabled us to have a number of advanced behaviors, including social behavior, tool making, language, and higher-level consciousness.

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