Verbal recall and recognition following traumatic brain injury: A [O-15]-water positron emission tomography study

Although several studies exist which have examined static functional neuroi maging following traumatic brain injury (TBI), controlled cognitive activat ion studies of episodic memory in this population have not been published. The present investigation studied verbal recall using [O-15]-water positron emission tomography (PET) in 5 individuals who sustained severe TBI (M GCS = 6.8; M years post-injury = 3.18), and 4 non-injured control participants . Statistical image analysis demonstrated changes in frontoparietal regiona l cerebral blood flow (rCBF) in both groups, but there were interesting dif ferences between groups and across conditions. Frontal lobe rCBF changes in TBI patients were reduced during free recall but enhanced during recogniti on, when compared to controls. Changes in cerebellar rCBF were observed in the control group during free recall, but not in the TBI sample. In both gr oups, bifrontal rCBF increases were noted on recognition tasks. The present findings provide evidence of alterations in specific substrates involved i n verbal recall following brain injury.