Anthony Y. Stringer

Activation and Effective Connectivity Changes Following Explicit-Memory Training for Face–Name Pairs in Patients With Mild Cognitive Impairment A Pilot Study

Background. Mild cognitive impairment (MCI) is often a precursor to Alzheimer disease. Little research has examined the efficacy of cognitive rehabilitation in patients with MCI, and the relevant neural mechanisms have not been explored. The authors previously showed the behavioral efficacy of cognitive rehabilitation using mnemonic strategies for face–name associations in patients with MCI. Here, the authors used functional magnetic resonance imaging (fMRI) to test whether there were training-specific changes in activation and connectivity within memory-related areas. Methods. A total of 6 patients with amnestic, multidomain MCI underwent pretraining and posttraining fMRI scans, during which they encoded 90 novel face–name pairs and completed a 4-choice recognition memory test immediately after scanning. Patients were taught mnemonic strategies for half the face–name pairs during 3 intervening training sessions. Results. Training-specific effects comprised significantly increased activation within a widespread cerebral cortical network involving medial frontal, parietal, and occipital regions; the left frontal operculum and angular gyrus; and regions in the left lateral temporal cortex. Increased activation common to trained and untrained stimuli was found in a separate network involving inferior frontal, lateral parietal, and occipital cortical regions. Effective connectivity analysis using multivariate, correlation-purged Granger causality analysis revealed generally increased connectivity after training, particularly involving the middle temporal gyrus and foci in the occipital cortex and the precuneus. Conclusion. The authors’ findings suggest that the effectiveness of explicit-memory training in patients with MCI is associated with training-specific increases in activation and connectivity in a distributed neural system that includes areas involved in explicit memory.

Gender and traumatic brain injury: Do the sexes fare differently?

Objective: To examine the relationship between gender and cognitive recovery 1 year following traumatic brain injury (TBI). Methods: Patients with blunt TBI were identified from the TBI Model Systems of Care National Database, multi-centre cohort study. The included patients (n = 325) were 16–45 years at injury, admitted to an acute care facility within 24 hours, received inpatient rehabilitation, had documented admission Glasgow Coma Scale (GCS) scores, completed neuropsychological follow-up 1 year post-injury and did not report pre-morbid learning problems. Multivariate analyses of variance examined the unadjusted association between gender and six cognitive domains examining attention/working memory, verbal memory, language, visual analytic skills, problem-solving and motor functioning. Analyses of covariance models were constructed to determine if confounding factors biased the observed associations. Results: Females performed significantly better than males on tests of attention/working memory and language. Males outperformed females in visual analytic skills. Gender remained significantly associated with performance in these areas when controlling for confounding variables. Conclusions: These results suggest a better cognitive recovery of females than males following TBI. However, future studies need to include non-TBI patients to control for possible pre-injury gender-related differences, as well as to conduct extended follow-ups to determine the stability of the observed differences.

Repetitive transcranial magnetic stimulation does not replicate the Wada test

Article abstract The authors compared inferior frontal speech arrest from repetitive transcranial magnetic stimulation (rTMS) with bilateral Wada tests in 17 epilepsy surgery candidates. Although rTMS lateralization correlated with the Wada test in most subjects, rTMS also favored the right hemisphere at a rate significantly greater than the Wada test. Postoperative language deficits were more consistent with Wada results. Available methods for inducing speech arrest with rTMS do not replicate the results of Wada tests.

Explicit memory training leads to improved memory for face–name pairs in patients with mild cognitive impairment: Results of a pilot investigation

Relatively few studies have examined the use of cognitive rehabilitation in patients with mild cognitive impairment (MCI), largely due to the assumption that training will not improve functioning in patients with progressive conditions. Face-name association, an ecologically valid task, is both dependent on the explicit memory system and difficult for MCI patients. During three hour-long sessions, eight patients diagnosed with MCI were trained in the use of explicit memory strategies with 45 face-name pairs. For each pair, they were taught to visually identify a facial feature, link a phonological cue to that feature, and recall the associated name. There was significant improvement in recognition accuracy, along with faster reaction times, for trained face-name pairs. Improved accuracy persisted when tested one month after training. Significant, but less, improvement was also found on untrained stimuli, raising the possibility of generalization of training strategies. Preliminary results suggest strategy-based cognitive rehabilitation may be beneficial in patients with MCI, though these results must be replicated with a control group to rule out practice effects.

Mnemonic strategy training partially restores hippocampal activity in patients with mild cognitive impairment

Learning and memory deficits typify patients with mild cognitive impairment (MCI) and are generally attributed to medial temporal lobe dysfunction. Although the hippocampus is perhaps the most commonly studied neuroanatomical structure in these patients, there have been few attempts to identify rehabilitative interventions that facilitate its functioning. Here, we present results from a randomized, controlled, single‐blind study in which patients with MCI and healthy elderly controls (HEC) were randomized to either three sessions of mnemonic strategy training (MS) or a matched‐exposure control group (XP). All participants underwent pre‐ and posttraining fMRI scanning as they encoded and retrieved object–location associations. For the current report, fMRI analyses were restricted to the hippocampus, as defined anatomically. Before training, MCI patients showed reduced hippocampal activity during both encoding and retrieval, relative to HEC. Following training, the MCI MS group demonstrated increased activity during both encoding and retrieval. There were significant differences between the MCI MS and MCI XP groups during retrieval, especially within the right hippocampus. Thus, MS facilitated hippocampal functioning in a partially restorative manner. We conclude that cognitive rehabilitation techniques may help mitigate hippocampal dysfunction in MCI patients.

Neuropharmacologic treatment of hemineglect: a case report comparing bromocriptine and methylphenidate.

Individuals who have hemineglect fail to attend to stimuli presented on the side of the body contralateral to a brain lesion. Although in animal studies the severity of neglect correlates with the degree of dopamine depletion, in hemineglect patients dopamine-enhancing medications have produced inconsistent results. We present a case of hemineglect following a right cerebrovascular accident in a 68-year-old man treated consecutively with methylphenidate and bromocriptine. Tests sensitive to neglect were administered during treatment with methylphenidate, then after all medications had been discontinued, then when the patient was taking low and moderate doses of bromocriptine, and again after all medications had been discontinued for 4 and 26 days. Methylphenidate was superior to no drug treatment. Bromocriptine produced more improvement in neglect than methylphenidate. Although the patient showed an exacerbation of his neglect after withdrawal from methylphenidate, performance gains persisted after withdrawal from bromocriptine. Treatment effects appear related to medication choice, timing of drug treatment, and the adaptability of dopaminergic receptor systems.

Neuropsychological outcome and community re-integration following traumatic brain injury: The impact of frontal and non-frontal lesions

Primary objective: To examine the relationship between cortical lesion location and brain injury outcome. It was hypothesized that focal frontal lesions after traumatic brain injury (TBI) would result in decreased executive and memory functioning and poor community participation outcome. Research design: Three quasi-experimental, prospective studies employed a total of 643 patients with focal frontal, fronto-temporal, non-frontal or no lesions in CT scans. Methods and procedures: CT scan analysis, neuropsychological assessment, the Neurobehavioural Functioning Inventory (NFI), the Community Integration Questionnaire (CIQ). Main results: In study 1, frontal and fronto-temporal groups performed worse in executive functioning and better in constructional ability. Study 2 found no differences in neuropsychological and community re-integration measures at 1-year follow-up. Study 3 found comparable neuropsychological test score improvement across groups over 1 year. Conclusions: Results are consistent with previous findings and document the potential for test score improvement with rehabilitation and suggest that lesion location needs to be considered when individual rehabilitation plans are being implemented in the post-acute stage of TBI.

Mnemonic strategy training improves memory for object location associations in both healthy elderly and patients with amnestic mild cognitive impairment: A randomized, single-blind study.

OBJECTIVE To evaluate the efficacy of mnemonic strategy training versus a matched-exposure control condition and to examine the relationship between training-related gains, neuropsychological abilities, and medial temporal lobe volumetrics in patients with amnestic mild cognitive impairment (aMCI) and age-matched healthy controls. METHOD Twenty-three of 45 screened healthy controls and 29 of 42 screened patients with aMCI were randomized to mnemonic strategy or matched-exposure groups. Groups were run in parallel, with participants blind to the other intervention. All participants completed five sessions within 2 weeks. Memory testing for object-location associations (OLAs) was performed during sessions one and five and at a 1-month follow-up. During Sessions 2-4, participants received either mnemonic strategy training or a matched number of exposures with corrective feedback for a total of 45 OLAs. Structural magnetic resonance imaging was performed in most participants, and medial temporal lobe volumetrics were acquired. RESULTS Twenty-one healthy controls and 28 patients with aMCI were included in data analysis. Mnemonic strategy training was significantly more beneficial than matched exposure immediately after training, p = .006, partial η2 = .16, and at 1 month, p < .001, partial η2 = .35, regardless of diagnostic group (healthy group or aMCI group). Although patients with aMCI demonstrated gains comparable to the healthy control groups, their overall performance generally remained reduced. Mnemonic strategy-related improvement was correlated positively with baseline memory and executive functioning and negatively with inferior lateral ventricle volume in patients with aMCI; no significant relationships were evident in matched-exposure patients. CONCLUSION Mnemonic strategies effectively improve memory for specific content for at least 1 month in patients with aMCI.

Ecologic validity in neuropsychological assessment: prediction of wayfinding.

This study compared the ability of clinical and ecologic simulation measures to predict performance on environment-specific criterion measures of wayfinding. Thirty-one unilateral stroke participants comprised the right and left hemisphere groups (16 patients with left sided and 15 patients with right sided strokes). Participants completed a battery of clinical tasks (e.g., traditional paper-and-pencil measures of visualization, mental rotation, visual memory and spatial orientation), ecologic simulations (e.g., slide route recall and visualization of a model town from differing perspectives) and environment specific criterion tasks (e.g., route recall and directional orientation). The groups were equivalent in age, sex, education, handedness, and weeks since stroke. Both ecologic simulation tasks were found to have fairly good internal consistency and 1 simulation task was significantly related to real world wayfinding. Of the clinical tasks, 1 visual memory test was correlated with a directional orientation criterion task, but none correlated with route navigation ability. Results are consistent with literature purporting the benefits of ecologic simulation tasks as predictors of real world functioning. ( JINS , 2001, 7 , 675–682.)

Symptoms of post-traumatic stress: Intrusion and avoidance 6 and 12 months after TBI

Primary objectives: (1) To examine survivors with traumatic brain injury (TBI) for symptoms of avoidance and intrusion, two dimensions of post-traumatic stress (PTS) at 6 and 12 months post-injury. (2) To identify risk factors associated with these symptoms. Research design: Prospective follow-up study. Methods and procedures: Georgia and North Carolina Model Brain Injury Systems participants (n = 198) with mild (19%), moderate (21%) and severe (60%) TBI were interviewed by telephone at 6 and 12 months post-injury. The Impact of Event Scale (IES) was used to identify intrusion and avoidance symptoms. Results: Symptoms consistent with severe PTS increased from 11% at 6 months to 16% 12 months post-injury (p < 0.003). African-Americans (p < 0.01) and women (p < 0.05) reported greater symptomatology at 12 months compared to their counterparts. TBI severity and memory of the event were not associated with PTS-like symptoms. Symptoms increased over time when examined by race, injury intent, gender and age (p < 0.05). Conclusions: Regardless of severity, survivors with TBI are at risk for developing symptoms consistent with PTS. Amnesia for the injury event was not protective against developing these symptoms. African-Americans appear to be at greatest risk.