Neuropsychological and Information Processing Performance and Its Relationship to White Matter Changes Following Moderate and Severe Traumatic Brain Injury: A Preliminary Study

Abstract

Reductions in information processing speed have frequently been reported following moderate and severe traumatic brain injuries (TBIs), consistent with the effects of diffuse white matter damage. Although the corpus callosum (CC) is a common site for diffuse damage following TBI, the effects of this damage on information processing speed have not been adequately examined. This study assessed a TBI group and a matched control group on tests of attention, memory, fluency, and set shifting ability, together with reaction time (RT) tasks requiring the inter- and intrahemispheric processing of visual and tactile information. The RT tasks were designed to target the cognitive functions that are likely to be affected by diffuse white matter damage, including damage to the CC. The TBI group demonstrated deficits in verbal and visual fluency and verbal memory. They were also slower on the visual and tactile RT tasks, were more affected by task complexity, and slower on RT tasks requiring the interhemispheric transfer of information. In fact, one of the interhemispheric tactile RT tasks proved to be the most discriminating of all the cognitive and RT measures. MRIs completed on a subset of TBI participants indicated that the mean CC measurements were 5% to 19% smaller than a normative control group, with the most atrophied areas being the isthmus and anterior midbody. Although white matter atrophy was moderately related to visual and tactile RT performance, and total hippocampal volume related to memory performance, CC area was not related to many of the tasks that were designed to tap interhemispheric processing. None of the standard cognitive tests correlated with outcome in the TBI group, but 1 of the tactile RT measures was significantly related to 2 measures of outcome.

Callosal Function in Pediatric Traumatic Brain Injury Linked to Disrupted White Matter Integrity

“…These results overlap with areas where we found differences in WM integrity between the IHTT-slow and control groups. In prior studies, the posterior CC was particularly vulnerable to TBI and was atrophied postinjury in some cases (Lindenberg et al, 1955;Gentry et al, 1988;Mendelsohn et al, 1992;Vuilleumier and Assal, 1995;Benavidez et al, 1999;Peru et al, 2003;Shiramizu et al, 2008;Slawik et al, 2009). Lesions in the CC post-TBI may result from TAI, arrested development in the CC, or secondary injuries (Shiramizu et al, 2008).…”

“…IHTT has been used to determine CC functional integrity in patients with agenesis of the CC and has shown prolonged CC disruption in case studies of TBI patients (Rugg et al, 1985;Brown et al, 1999;Peru et al, 2003). IHTT, as measured by task reaction time, is impaired after TBI in children (Benavidez et al, 1999) and adults (Mathias et al, 2004). A slower IHTT indicates slower information transfer between the cerebral hemispheres and impaired CC functioning (Brown et al, 1999).…”

Neuropsychology and clinical neuroscience of persistent post-concussive syndrome

“…Returning to the biomechanical deformation effects reviewed above, long-coursing axons are going to be more vulnerable, particularly interhemispheric connections, especially the corpus callosum and anterior commissure (Cecil et al, 1998;Holshouser et al, 2006;Inglese et al, 2005b;Mathias et al, 2004;Wilde et al, 2006a;Wilde et al, 2006c). Thus, neuropsychological tasks that require interhemispheric integration and0or multiple intracortical connections often show differences in the form of slowed responding, even in those with mTBI (Mathias et al, 2004) So, the hypothesis put forth in this section is that the biomechanics of brain injury simultaneously disrupt neurological function in the upper brainstem, pituitaryhypothalamic axis, medial temporal lobe, and basal forebrain concomitant with irritative injury to the vasculature and meninges, which gives rise to the symptoms observed in the post-concussive state and the neuropsychological sequela associated with such an injury. How rapidly these neural, dural, and vascular areas return to homeostasis or recovery from some adaptive mechanism or do not recover, provides the biological basis for the symptoms expressed.…”

Hemispheric and executive influences on low-level language processing after traumatic brain injury

“…While this is often reported as a response time difference between persons with TBI and control participants, it is not attributable to simple motor factors, as it can occur even when simple motor response times are statistically identical between TBI and control groups (Russell, Scanlon, Arenth, & Ricker, 2009). Speed of processing differences have been noted during verbal and visual fluency, verbal memory, serial addition, and many other tasks (e.g., Bittner & Crowe, 2007;Madigan, DeLuca, Diamond, Tramontano, & Averill, 2000;Mathias et al, 2004). It seems that tasks which are more cognitively "complex" or require interhemispheric transfer are most likely to elicit speed of processing difference effects.…”

“…One group has called involvement of the corpus callosum the best single predictor of injury severity (Gale et al, 1995). Mathias et al (2004) found a group of people with TBI to have a smaller callosal volume than matched controls, and an autopsy study reported DAI to be preferentially located in the corpus callosum of road traffic victims (Pittella & Gusmão, 2004). The largest body of evidence on this matter, studies examining DAI with DTI, have found overwhelming evidence of corpus callosum involvement as shown through decreased fractional anisotropy (FA) in the corpus callosum of TBI groups as compared to controls (Inglese et al, 2005;Kraus et al, 2007;Nakayama et al, 2006;Tisserand et al, 2006; though see Bazarian, Zhong, Blyth, Zhu, Kavcic, & Peterson, 2007, for evidence of elevated FA values).…”