Verbal Learning and Memory Deficits in Traumatic Brain Injury: Encoding, Consolidation, and Retrieval
The present study examined the nature of verbal memory deficits in individuals with traumatic brain injury (TBI) compared to healthy controls. The study was designed to control for methodological shortcomings of previous related research. Three groups of participants were used: (a) a head injured sample with moderate to severe traumatic brain injuries (N=55), (b) a control sample matched on age and initial performance on CVLT Trial 5 and Sum of Trials 1 to 5 (N=55), and (c) a control sample matched on age, education, and race, but not on initial CVLT learning performance (N=55). Current findings indicate that: (a) rate of learning was comparable across groups, consistent with no encoding differences, (b) TBI patients have a significantly more rapid rate of forgetting of new information than either acquisition-matched or demographic-matched controls, consistent with consolidation problems in TBI, (c) TBI patients have less proactive interference than demographic-matched control participants, consistent with a consolidation problem in the TBI group, (d) TBI patients and acquisition-matched controls have comparably low rates of proactive interference, consistent with impaired acquisition in both of these groups, and (e) TBI patients and controls do not differ in the benefit experienced from semantic or recognition retrieval cues, consistent with no differences in retrieval processes. These data support an impaired consolidation hypothesis, rather than encoding or retrieval deficits, as the primary deficit underlying memory impairment in TBI.
Available from: Maureen Schmitter-Edgecombe
- "Past research utilizing verbal learning paradigms has shown that individuals with TBI in the early stages of recovery perform more poorly than controls on tests of episodic verbal memory (e.g., Anderson & Schmitter-Edgecombe, 2009; Vanderploeg et al., 2001), but demonstrate a good recovery curve of verbal memory abilities within the first year postinjury (Christensen et al., 2008). Although there has been debate in the literature about whether the content of activity memories is retained differently than the content of verbal information (Kausler & Lichty, 1988; Schmitter-Edgecombe & Simpson, 2001), studies have consistently shown that recall for subject-performed tasks (SPTs) is better than for verbal material (Zimmer, Helstrup, & Engelkamp, 2000; Engelkamp, Seiler, & Zimmer, 2005). "
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ABSTRACT: Few studies have investigated the complex nature of everyday activity memory following traumatic brain injury (TBI). This study examined recovery of content and temporal order memory for performed activities during the first year in individuals who suffered moderate to severe TBI. TBI and control participants completed eight different cognitive activities at baseline (i.e., acutely following injury for TBI) and then again approximately one year later (follow-up). Participants' free recall of the activities provided a measure of content memory. Temporal order memory was assessed with a reconstruction task. Self-report and informant report of everyday memory problems at follow-up were used to examine the relationship between activity memory performances and everyday memory. TBI participants showed significant recovery in both content and temporal order memory for activities during the first year. Despite showing significant recovery, the TBI group's activity memory performances remained poorer than that of controls at follow-up. Greater self- and informant report of everyday memory difficulties was associated with poorer temporal order memory but not content memory for activities. These findings demonstrate recovery in multiple memory processes that support activity memory following moderate to severe TBI. The findings also suggest a stronger link between everyday memory abilities and temporal order memory for activities than activity memory content in a TBI population.
Available from: Elisabeth Wilde
- "Memory impairment is one of the most common residual deficits noted by patients following traumatic brain injury (TBI), as corroborated by their families, and confirmed by neuropsychological testing (Levin, 1989). Most studies with patients who sustained moderate to severe TBI have found impaired memory (Blachsteni et al., 1993; Millis and Ricker, 1994; Vakil, 2005; Vanderploeg et al., 2001). In addition, recovery of learning and memory functions has been found to be slower compared to other TBI cognitive abilities (Lezak, 1979), with deficient learning and memory persisting after moderate to severe TBI (Zec et al., 2001). "
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ABSTRACT: Based on the importance of the perforant pathway (PP) for normal hippocampal function, the vulnerability of temporal structures, and significant memory impairment in patients with traumatic brain injury (TBI), we investigated in vivo changes in the PP zone, hippocampus, and temporal lobe white and gray matter using diffusion tensor imaging (DTI) and volumetric analysis, and any specific relations with memory performance (Verbal Selective Reminding Test, Rey-Osterrieth Complex Figure Test), in 14 patients with severe TBI. Compared to a demographically-similar control group, our patients had significantly decreased fractional anisotropy (FA) and higher apparent diffusion coefficient (ADC) for the PP zone bilaterally, and higher ADC bilaterally in the hippocampus. Volumetric analysis revealed significantly decreased volumes in both hippocampi and temporal gray matter bilaterally. Consistent long-term retrieval (CLTR) and delayed recall were significantly related to (1) right and left PP zone ADC, (2) left hippocampus ADC, and (3) left hippocampal volume. Nonverbal memory (immediate and delayed recall) was significantly associated with (1) right and left PP zone ADC, (2) left hippocampal volume, and (3) gray (immediate recall) and white (immediate recall, bilaterally; delayed recall, left) matter temporal volumes. Advanced neuroimaging analysis can detect in vivo changes in the PP zone and temporal structures in patients with severe TBI, with these changes being highly associated with memory impairment.
Available from: Jonathan W Anderson
- "Given that Schmitter-Edgecombe and Rueda hypothesized that episodic memory dysfunction may have accounted for the poorer time estimates of the TBI group at the longer time intervals (i.e., > 30 s), we were particularly interested in whether improvements in episodic memory ability during the first year of recovery would be associated with concomitant improvements in time perception abilities for the longer durations. Multiple past studies have found that individuals with TBI in the early stages of recovery perform more poorly on tests of episodic memory than controls (e.g., Anderson & Schmitter-Edgecombe, 2008; Sunderland, Harris, & Baddeley, 1983; Vanderploeg et al., 2001), but demonstrate a good recovery curve of memory abilities within the first year post-injury (Christensen et al., 2008). "
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ABSTRACT: Accurate time estimation abilities are thought to play an important role in efficient performance of many daily activities. This study investigated the role of episodic memory in the recovery of time estimation abilities following moderate to severe traumatic brain injury (TBI).
Using a prospective verbal time estimation paradigm, TBI participants were tested in the early phase of recovery from TBI and then again approximately one year later. Verbal time estimations were made for filled intervals both within (i.e., 10 s, 25 s) and beyond (i.e., 45 s 60 s) the time frame of working memory.
At baseline, when compared to controls, the TBI group significantly underestimated time durations at the 25 s, 45 s and 60 s intervals, indicating that the TBI group perceived less time as having passed than actually had passed. At follow-up, despite the presence of continued episodic memory impairment and little recovery in episodic memory performance, the TBI group exhibited estimates of time passage that were similar to controls.
The pattern of data was interpreted at suggesting that episodic memory performance did not play a noteworthy role in the recovery of temporal perception in TBI participants.
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