Laura J. Grande

Impaired Executive Function Is Associated with Delirium After Coronary Artery Bypass Graft Surgery

OBJECTIVES: To determine the extent to which preoperative performance on tests of executive function and memory was associated with delirium after coronary artery bypass graft (CABG) surgery.

Temporal lobe epilepsy as a model to understand human memory: The distinction between explicit and implicit memory

Decades of research have provided substantial evidence of memory impairments in patients with temporal lobe epilepsy (TLE), including deficits in the encoding, storage, and retrieval of new information. These findings are not surprising, given the associated underlying neuroanatomy, including the hippocampus and surrounding medial temporal lobe structures. Because of its associated anatomic and cognitive characteristics, TLE has provided an excellent model by which to examine specific aspects of human memory functioning, including classic distinctions such as that between explicit and implicit memory. Various clinical and experimental research studies have supported the idea that both conscious and unconscious processes support memory functioning, but the role of relevant brain structures has been the subject of debate. This review is concerned with a discussion of the current status of this research and, importantly, how TLE can inform future studies of memory distinctions.

Obstructing colorectal carcinomas: Prospective study

Intestinal obstruction owing to colonic carcinoma is a relatively frequent cause of acute abdominal pain. The aim of this prospective study is to evaluate the prognostic factors that may influence the final outcome of those patients operated upon for an intestinal obstruction (OG) as opposed to those electively operated upon (EG). From September 1984 to March 1988, a total of 188 patients with colorectal cancer have been included in the study. One hundred thirty-five were EG, while 53 (28.1 percent) were OG. The mean ages were similar in both groups. Sex, morbidity, and mortality rates were equally distributed. Curative resection rate was significantly higher in the EG group (P=0.029). Tumor staging tended to be significantly more advanced in OG patients (chi-square = 9.054;df=3;P=0.026). Multivariate analysis (proportional hazards model) showed that the only independent prognostic factor was tumor staging (P=0.0000). Obstruction itself disappears as a predictive variable when tumor staging is introduced in the model. We conclude that obstructing colon carcinomas tend to be more locally advanced, that probably being the only reason for a worse long-term prognosis.

Variation in Blood Pressure is Associated with White Matter Microstructure but not Cognition in African Americans

Although hypertension is a major risk factor for cerebrovascular disease (CVD) and is highly prevalent in African Americans, little is known about how blood pressure (BP) affects brain-behavior relationships in this population. In predominantly Caucasian populations, high BP is associated with alterations in frontal-subcortical white matter and in executive functioning aspects of cognition. We investigated associations among BP, brain structure, and neuropsychological functioning in 52 middle-older-age African Americans without diagnosed history of CVD. All participants underwent diffusion tensor imaging for examination of white matter integrity, indexed by fractional anisotropy (FA). Three regions of interest were derived in the anterior (genu) and posterior (splenium) corpus callosum and across the whole brain. A brief neuropsychological battery was administered from which composite scores of executive function and memory were derived. Blood pressure was characterized by mean arterial blood pressure (MABP). When controlling for age, higher MABP was associated with lower FA in the genu, and there was a trend for this same relationship with regard to whole-brain FA. When the sample was broken into groups on the basis of treatment for BP regulation (medicated vs. nonmedicated), MABP was related to genu and whole-brain FA only in the nonmedicated group. Neither MABP nor FA was significantly related to either neuropsychological composite score regardless of medication use. These data provide important evidence that variation in BP may contribute to significant alterations in specific neural regions of white matter in nonmedicated individuals without symptoms of overt CVD.

Hippocampal volume and declarative memory function in combat-related PTSD

The proposition that declarative memory deficits are systematically related to smaller hippocampal volume was tested in a relatively large sample (n = 95) of U.S. military veterans with and without combat-related posttraumatic stress disorder. This correlative analysis was extended by including multiple measures of verbal and visual declarative memory and multiple memory-relevant regional brain volumes that had been shown to exhibit main effects of PTSD in prior work. Small-to-moderate effects were observed on verbal declarative memory in line with a recent meta-analysis; nevertheless, little or no evidence of systematic linear covariation between memory measures and brain volumes was observed.

Semantic priming in patients with right frontal lobe lesions

Patients with unilateral, right frontal lobe damage (N=13) and matched controls (N=20) performed a task of lexical ambiguity resolution in order to explore the contribution of right frontal regions to lexical-semantic priming. Word triplets consisting of balanced homographs were presented to participants in four conditions: concordant, discordant, neutral, and unrelated. Controls demonstrated facilitation for concordant meanings of homographs, as evidenced by their faster reaction times in the concordant relative to the unrelated (baseline) condition, as well as a lack of facilitation for the discordant meaning relative to the neutral and concordant conditions. Results in patients with right frontal lobe damage differed depending on the site of the lesion. Patients with lesions restricted to the right medial frontal lobe only showed facilitation in the neutral condition, while those with lesions encroaching upon the right dorsolateral region demonstrated facilitation of both discordant and concordant meanings relative to the baseline condition. These results support a role for the right frontal lobe in semantic priming and suggest possible specialization within the right prefrontal cortex for the processing of lexical-semantic information.

Visual selective attention in Parkinson's disease: dissociation of exogenous and endogenous inhibition.

Impairment in the inhibitory mechanism of visual selective attention in patients with Parkinsons disease (PD) is controversial. The present study sought to understand disparate findings in a manner analogous to the relative preservation of exogenously evoked movement and impairment of endogenously evoked movement. The authors examined inhibition of return (i.e., exogenously evoked inhibition; IOR) and negative priming (i.e., endogenously evoked inhibition; NP) in a group of 14 patients with PD and 14 healthy controls (HC). Unlike the HC, who demonstrated significant inhibition in both tasks, the group with PD demonstrated intact inhibition only in the IOR task. Dopamine replacement therapy did not affect performance. The findings are discussed within the context of a model that differentiates the essential involvement of the basal ganglia for endogenously evoked spatial inhibition.

Semantic processing and orthographic specificity in hemispatial neglect

Two sets of experiments, each consisting of a semantic priming task and a discrimination task, investigated the proceedings of lexical information in the neglected visual field. In the semantic priming task, subjects made lexical decisions to target words preceded by lateralized word primes; in the discrimination task, they indicated which of two words corresponded to a target word presented to the left visual field (LVF) or right visual field (RVF). The first set of experiments indicated that although patients were unable to discriminate words presented in the LVF, they showed significant priming when LVF primes were followed by semantically related targets compared to unrelated targets. The second set of experiments further examined the nature of this priming effect by comparing priming in a condition in which primes were semantically related to the target word (e.g., TEA-CUP) and a condition in which primes were unrelated to the target word, but orthographically similar to a related prime (e.g., PEA-CUP). This experiment replicated the previously established semantic priming effects and demonstrated significant negative priming for targets preceded by LVF primes that were orthographically similar to a semantically related word. Again, patients performed at chance in the forced-choice discrimination task when targets were presented in the LVF These findings indicate that semantic processing of neglected lexical information is based on fully specified perceptual and orthographic information. A lateral inhibitory mechanism is proposed that maximizes the probability, albeit unsuccessfully, that neglected orthographic information will reach awareness.

Mild Cognitive Impairment Status and Mobility Performance: An Analysis From the Boston RISE Study

BACKGROUND The prevalence of mild cognitive impairment (MCI) and mobility limitations is high among older adults. The aim of this study was to investigate the association between MCI status and both performance-based and self-report measures of mobility in community-dwelling older adults. METHODS An analysis was conducted on baseline data from the Boston Rehabilitative Impairment Study in the Elderly study, a cohort study of 430 primary care patients aged 65 or older. Neuropsychological tests identified participants with MCI and further subclassified those with impairment in memory domains (aMCI), nonmemory domains (naMCI), and multiple domains (mdMCI). Linear regression models were used to assess the association between MCI status and mobility performance in the Habitual Gait Speed, Figure of 8 Walk, Short Physical Performance Battery, and self-reported Late Life Function and Disability Instruments Basic Lower Extremity and Advanced Lower Extremity function scales. RESULTS Participants had a mean age of 76.6 years, and 42% were characterized with MCI. Participants with MCI performed significantly worse than participants without MCI (No-MCI) on all performance and self-report measures (p < .01). All MCI subtypes performed significantly worse than No-MCI on all mobility measures (p < .05) except for aMCI versus No-MCI on the Figure of 8 Walk (p = .054) and Basic Lower Extremity (p = .11). Moreover, compared with aMCI, mdMCI manifested worse performance on the Figure of 8 Walk and Short Physical Performance Battery, and naMCI manifested worse performance on Short Physical Performance Battery and Basic Lower Extremity. CONCLUSIONS Among older community-dwelling primary care patients, performance on a broad range of mobility measures was worse among those with MCI, appearing poorest among those with nonmemory MCI.

Decreased white matter integrity in neuropsychologically defined mild cognitive impairment is independent of cortical thinning.

Improved understanding of the pattern of white matter changes in early and prodromal Alzheimer’s disease (AD) states such as mild cognitive impairment (MCI) is necessary to support earlier preclinical detection of AD, and debate remains whether white matter changes in MCI are secondary to gray matter changes. We applied neuropsychologically based MCI criteria to a sample of normally aging older adults; 32 participants met criteria for MCI and 81 participants were classified as normal control (NC) subjects. Whole-head high resolution T1 and diffusion tensor imaging scans were completed. Tract-Based Spatial Statistics was applied and a priori selected regions of interest were extracted. Hippocampal volume and cortical thickness averaged across regions with known vulnerability to AD were derived. Controlling for corticalthic kness, the MCI group showed decreased average fractional anisotropy (FA) and decreased FA in parietal white matter and in white matter underlying the entorhinal and posterior cingulate cortices relative to the NC group. Statistically controlling for cortical thickness, medial temporal FA was related to memory and parietal FA was related to executive functioning. These results provide further support for the potential role of white matter integrity as an early biomarker for individuals at risk for AD and highlight that changes in white matter may be independent of gray matter changes.