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Reduction of functional brain connectivity in mild traumatic brain injury during working memory
Sanjay Kumar1, Shobini L Rao, Bangalore A Chandramouli
1Behavioural Brain Sciences, School of Psychology, University of Birmingham, Birmingham, B15 2TT, United Kingdom. s.kumar.1@bham.ac.uk
Abstract:
Working memory deficits are present in patients with mild traumatic brain injury (MTBI). Functional connectivity of different brain regions is required for adequate working memory. Brain injury is associated with disrupted connectivity due to microscopic axonal damage. In this investigation, we sought to investigate functional brain connectivity during working memory in MTBI patients. A sample of 30 MTBI patients and 30 age-, education-, and gender-matched normal controls were studied. Working memory was assessed with the Sternberg's verbal and visuo-spatial working memory tasks. Electro-encephalography (EEG) was recorded from 128 channels while subjects performed working memory tasks and during eyes closed resting condition. EEG coherence was computed in theta; lower and upper alpha; and lower and upper beta frequency bands during the encoding, retention, and retrieval stages of working memory as well as during eyes-closed rest. We found that the MTBI patients had impaired verbal and visuo-spatial working memory. The different stages of working memory were associated with poor intrahemispheric coherence in long-range (fronto-parietal) and mid-range (fronto-temporal and temporo-parietal) regions as well as poor interhemispheric coherence in the frontal and temporal regions in the MTBI patients. The deficit in coherence was present in theta, alpha, and beta frequency bands. However, the MTBI and the control group had comparable coherence values in intra- and inter-hemispheric regions during eyes closed rest. We suggest that the inter- and intra-hemispheric functional connectivity is impaired in MTBI during working memory performance.
Insights
Mild traumatic brain injury (MTBI) patients show impaired working memory due to disrupted brain connectivity. Functional connectivity deficits were observed during working memory tasks but not at rest in MTBI individuals.
Area of Science:
- Neuroscience
- Cognitive Psychology
- Medical Imaging
Background:
- Working memory is crucial for cognitive function and is often impaired after mild traumatic brain injury (MTBI).
- Microscopic axonal damage in MTBI can disrupt functional brain connectivity, essential for working memory.
- Understanding these connectivity changes is key to diagnosing and treating MTBI-related cognitive deficits.
Purpose of the Study:
- To investigate functional brain connectivity during working memory tasks in patients with MTBI.
- To compare EEG coherence patterns between MTBI patients and healthy controls during various working memory stages.
- To identify specific patterns of disrupted connectivity associated with working memory deficits in MTBI.
Main Methods:
- Recruited 30 MTBI patients and 30 matched healthy controls.
- Assessed working memory using Sternberg's verbal and visuo-spatial tasks.
- Recorded 128-channel EEG during tasks and eyes-closed rest, analyzing coherence in theta, alpha, and beta bands across encoding, retention, and retrieval stages.
Main Results:
- MTBI patients exhibited deficits in both verbal and visuo-spatial working memory.
- Impaired intrahemispheric (fronto-parietal, fronto-temporal, temporo-parietal) and interhemispheric (frontal, temporal) coherence was found in MTBI patients across theta, alpha, and beta bands during working memory tasks.
- No significant differences in coherence were observed between groups during eyes-closed rest.
Conclusions:
- Functional brain connectivity, both intra- and inter-hemispheric, is impaired in MTBI patients during working memory performance.
- The observed coherence deficits suggest a neural basis for working memory impairments following MTBI.
- EEG coherence analysis provides a valuable tool for assessing functional connectivity disruptions in MTBI.
