Shahzadi Adeena ’25

Understanding the fundamental mechanisms of consciousness, particularly following traumatic brain injury (TBI), is nuanced and challenging. Thalamic function plays a critical role in facilitating consciousness; injury to thalamus-frontal circuitry can impair consciousness. Sima Mofakham and Charles Millek of Stony Brook University hypothesized that thalamocortical projections to the frontoparietal network facilitate the complex dynamics needed for consciousness, and that injury to these connections impedes functions of cortical networks, leading to a loss of consciousness. Mofakham and Millek used direct recordings of local field potentials (LFPs) from frontal areas to understand how neural signals associated with consciousness arise; they also sought to gain insight into the role of the thalamus in shaping the functional state of the cortex during recovery of consciousness.

To conduct this study, the researchers recruited one control subject and five patients who became comatose after suffering severe traumatic brain injury due to seizures. Patients were implanted with a ten-contact stereotactic depth electrode to detect seizures and provide antiepileptic treatment, preventing excessive rapid firing of neurons. Single-pulse stimulation—a technique that stimulates specific brain regions by applying a single, brief electrical pulse—was applied to contacts within the ACC (anterior cingulate cortex) and DLPFC (dorsolateral prefrontal cortex), while all other contacts, including scalp and depth electrodes, were recorded. Four of the five patients returned to consciousness during a period ranging from several days to several weeks. The researchers also found that patients who recovered consciousness had a more rapid increase in high-frequency power in the LFPs, particularly in the alpha and beta frequency bands, compared to the patient who did not recover consciousness. This suggests the patients were able to sustain increased levels of relaxation and concentration due to faster alpha and beta frequencies, respectively. 

This study’s findings suggest thalamic injury is associated with a dysfunctional cortical state characterized by simple and repetitive brain activity, which is inadequate for engaging the complex neuronal ensembles required for goal-directed behavior and consciousness. It was found that the  thalamus needs to adjust excitability and connectivity to enable the formation of the complex dynamics consistent with consciousness. These findings have implications for coma therapeutics, as interventions to increase cortical excitability alone are unlikely to restore consciousness when higher-order thalamic projections are injured, though further research is warranted due to the study’s small sample size and scope limited to a single cause of traumatic brain injuries.

Works cited:
[1] S. Mofakham, et al. Electrocorticography reveals thalamic control of cortical dynamics following traumatic brain injury. Commun Biol 4, (2021). doi:10.1038/s42003-021-02738-2
[2] Image retrieved from: https://www.pexels.com/photo/medical-imaging-of-the-brain-5723875/