The Less BOLD, the Wiser: Support for the latent resource hypothesis after traumatic brain injury

• Published in: Human brain mapping Vol. 33; no. 4; pp. 979 - 993
• Main Authors: Medaglia, John D., Chiou, Kathy S., Slocomb, Julia, Fitzpatrick, Neal M., Wardecker, Britney M., Ramanathan, Deepa, Vesek, Jeffrey, Good, David C., Hillary, Frank G.
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 01.04.2012; Wiley-Liss; John Wiley & Sons, Inc
• Subjects: Adolescent; Adult; Biological and medical sciences; Brain Injuries - physiopathology; Brain Mapping; Cerebral Cortex - physiology; cognitive control; Female; functional MRI; Fundamental and applied biological sciences. Psychology; Humans; Image Interpretation, Computer-Assisted; Investigative techniques, diagnostic techniques (general aspects); Magnetic Resonance Imaging; Male; Medical sciences; Memory, Short-Term - physiology; Middle Aged; Nervous system; Neuronal Plasticity - physiology; Neuropsychological Tests; Personality. Affectivity; Psychology. Psychoanalysis. Psychiatry; Psychology. Psychophysiology; Radiodiagnosis. Nmr imagery. Nmr spectrometry; reorganization; Sexuality. Sexual behavior; traumatic brain injury; working memory; Young Adult; functional MRI; Nervous system diseases; Radiodiagnosis; Central nervous system; traumatic brain injury; Working memory; reorganization; Nuclear magnetic resonance imaging; Trauma; Cognitive control; Encephalon
• ISSN: 1065-9471; 1097-0193
• DOI: 10.1002/hbm.21264

Previous studies of the BOLD response in the injured brain have revealed neural recruitment relative to controls during working memory tasks in several brain regions, most consistently the right prefrontal cortex and anterior cingulate cortices. We previously proposed that the recruitment observed in this literature represents auxiliary support resources, and that recruitment of PFC is not abnormal or injury specific and should reduce as novelty and challenge decrease. The current study directly tests this hypothesis in the context of practice of a working memory task. It was hypothesized that individuals with brain injury would demonstrate recruitment of previously indicated regions, behavioral improvement following task practice, and a reduction in the BOLD signal in recruited regions after practice. Individuals with traumatic brain injury and healthy controls performed the n‐back during fMRI acquisition, practiced each task out of the scanner, and returned to the scanner for additional fMRI n‐back acquisition. Statistical parametric maps demonstrated a number of regions of recruitment in the 1‐back in individuals with brain injury and a number of corresponding regions of reduced activation in individuals with brain injury following practice in both the 1‐back and 2‐back. Regions of interest demonstrated reduced activation following practice, including the anterior cingulate and right prefrontal cortices. Individuals with brain injury demonstrated modest behavioral improvements following practice. These findings suggest that neural recruitment in brain injury does not represent reorganization but a natural extension of latent mechanisms that engage transiently and are contingent upon cerebral challenge. Hum Brain Mapp, 2012. © 2011 Wiley Periodicals, Inc.