Traumatic brain injury and memory: The role of hippocampal atrophy.

Abstract

In traumatically brain-injured (TBI) patients (N = 83), memory performance was examined on the Warrington Recognition Memory Test, Rey-Osterrieth Complex Figure, and the Logical Memory and Visual Reproduction subtests of the Wechsler Memory Scale-Revised in relationship to time postinjury and structural changes based on MRI volumetry, including hippocampus volume. Significant trauma-induced changes were observed, including hippocampal atrophy. Structurefunction relationships generally became significant only after 90 days postinjury. Memory tended to relate more to the degree of hippocampal atrophy, particularly left hippocampus, than to nonspecific indicators such as the temporal horns or the ventricle-to-brain ratio. A stronger relationship with left versus right hippocampus was evident for measures of verbal and supposedly nonverbal memory. These results are discussed with regard to the role the hippocampus may play in a neural system of memory.Current MRI technology provides the means by which cortical and subcortical structures can be quantified in their normal and pathologic state (Blatter et al., 1995, in press).Recently, we demonstrated that cerebral trauma, as a consequence of closed head injury, results in hippocampal atrophy (Bigler et al., in press). This comes as no surprise, because the mesial temporal lobe is a vulnerable site to injury (Gale,

Aging, gender, and the elderly adult brain: An examination of analytical strategies

“…Some researchers use structure volume as the dependent variable, while others use volume ratios; some advocate using intracranial volume (ICV) as a covariate, while others do not. We conducted analyses on age and gender using each of these methods, and report them all in order to facilitate comparisons (see [3,4 for similar approaches). Table 1 presents the demographics of our sample and the number of scans that were available for each brain structure.…”

Fornix and Hippocampal Atrophy in Traumatic Brain Injury

“…Despite the reduced memory performance in the more severely injured, the correlation between fornix size and memory was weak (r = 0.23), as was hippocampal volume and memory (r = 0.32). Although the role of the hippocampus in memory is well established (Squire et al 1991), it is an oversimplification to state that memory disorders in TBI are specific to hippocampal damage and are the sole neuroanatomical factor disrupting memory function (Bigler et al 1996). Studies that have examined hippocampal volume and memory in patients with varied etiologies (Lencz et al 1992;Bigler et al 1997;Heun et al 1997;Stout et al 1999) have found only modest relationships between hippocampal size and memory performance.…”

“…In separate independent studies, we have shown previously that trauma results in hippocampal (Bigler et al 1996 as well as fornix atrophy (Gale et al 1993). However, none of these investigations examined the relationship between hippocampal atrophy and fornix atrophy.…”

“…Disorders of memory and learning are common in traumatic brain injury (TBI) (Dixon et al 1993;Bigler et al 1996), and although the neuroanatomic basis for disordered memory in TBI has not been fully addressed, the limbic system is implicated. There are several mechanisms whereby TBI may result in pathological changes in the temporal lobes.…”

Human spatial navigation deficits after traumatic brain injury shown in the arena maze, a virtual Morris water maze

“…TBI causes a wide range of social, emotional and cognitive changes [4], though the most common cognitive complaint is forgetfulness [5]. Memory problems after TBI manifest on tests of facial recognition, story recall, semantic information, prospective memory and autobiographical memory [6] and these have been linked to hippocampal damage [7,8]. A deficit which may also be related to hippocampal damage but which has not received much attention is the loss of the ability to navigate from place to place in everyday life.…”