Lynette J. Tippett

Memory of myself: Autobiographical memory and identity in Alzheimer's disease

A number of theories posit a relationship between autobiographical memory and identity. To test this we assessed the status of autobiographical memory and identity in 20 individuals with Alzheimers disease (AD) and 20 age‐matched controls, and investigated whether degree of autobiographical memory impairment was associated with changes in identity. Two tests of autobiographical memory (Autobiographical Memory Interview, autobiographical fluency) and two measures of identity (Twenty Statements Test, identity items of the Tennessee Self Concept Scale) were administered. AD participants exhibited significant impairments on both memory tests, and changes in the strength, quality, and direction of identity relative to controls. Impairments of some components of autobiographical memory, particularly autobiographical memory for childhood and early adulthood, were related to changes in the strength and quality of identity. These findings support the critical role of early adulthood autobiographical memories (16–25 years) in identity, and suggest autobiographical memory loss affects identity.

Cerebral Ischemic Lesions on Diffusion-Weighted Imaging Are Associated With Neurocognitive Decline After Cardiac Surgery

Background and Purpose— Improvements in cardiac surgery mortality and morbidity have focused interest on the neurological injury such as stroke and cognitive decline that may accompany an otherwise successful operation. We aimed to investigate (1) the rate of stroke, new ischemic change on MRI, and cognitive impairment after cardiac valve surgery; and (2) the controversial relationship between perioperative cerebral ischemia and cognitive decline. Methods— Forty patients (26 men; mean [SD] age 62.1 [13.7] years) undergoing intracardiac surgery (7 also with coronary artery bypass grafting) were studied. Neurological, neuropsychological, and MRI examinations were performed 24 hours before surgery and 5 days (MRI and neurology) and 6 weeks (neuropsychology and neurology) after surgery. Cognitive decline from baseline was determined using the Reliable Change Index. Results— Two of 40 (5%) patients had perioperative strokes and 22 of 35 (63%) tested had cognitive decline in at least one measure (range, 1 to 4). Sixteen of 37 participants (43%) with postoperative imaging had new ischemic lesions (range, 1 to 17 lesions) with appearances consistent with cerebral embolization. Cognitive decline was seen in all patients with, and 35% of those without, postoperative ischemic lesions (P<0.001), and there was an association between the number of abnormal cognitive tests and ischemic burden (P<0.001). Conclusion— We have provided a reliable estimate of the rate of stroke, postoperative ischemia, and cognitive impairment at 6 weeks after cardiac valve surgery. Cognitive impairment is associated with perioperative ischemia and is more severe with greater ischemic load.

Autobiographical memory and sense of self.

Despite a strong intuitive and theoretical tradition linking autobiographical memory and sense of self, there are few coherent, testable models that exemplify how these constructs relate. Without any clear theoretical starting point, research efforts have been fragmented, with many different fields of psychology operating in relative isolation, using different methodological approaches and a confusing array of self-related terminology. We attempt to bridge the widening gap between theory and research by proposing a novel framework for sense of self and memory. This simple model delineates sense of self along 2 dimensions: the subjective versus objective and the present versus temporally extended aspects of sense of self. The 4 resulting components of sense of self are argued to relate to autobiographical memory in important, but very different, ways. Subjective sense of self provides a crucial precondition for episodic memory, which in turn is a prerequisite for phenomenological continuity. Autobiographical memory, and particularly its semanticized forms, are important for the formation and maintenance of a mental representation of the objective self in the present moment and across time. This model does not represent a new theoretical direction for the study of sense of self and memory; to the contrary, it is deeply grounded in the theoretical work of the past few decades. Its novelty is that it translates this theoretical groundwork into a form that is readily accessible for researchers. We review evidence for our model and suggest ways that it may provide a roadmap for future research efforts.

The Neuropathology of Huntington's Disease

The basal ganglia are a highly interconnected set of subcortical nuclei and major atrophy in one or more regions may have major effects on other regions of the brain. Therefore, the striatum which is preferentially degenerated and receives projections from the entire cortex also affects the regions to which it targets, especially the globus pallidus and substantia nigra pars reticulata. Additionally, the cerebral cortex is itself severely affected as are many other regions of the brain, especially in more advanced cases. The cell loss in the basal ganglia and the cerebral cortex is extensive. The most important new findings in Huntingtons disease pathology is the highly variable nature of the degeneration in the brain. Most interestingly, this variable pattern of pathology appears to reflect the highly variable symptomatology of cases with Huntingtons disease even among cases possessing the same number of CAG repeats.

Cell loss in the motor and cingulate cortex correlates with symptomatology in Huntington’s disease

Huntingtons disease is an autosomal dominant inherited neurodegenerative disease with motor symptoms that are variably co-expressed with mood and cognitive symptoms, and in which variable neuronal degeneration is also observed in the basal ganglia and the cerebral cortex. We have recently shown that the variable symptomatology in Huntingtons disease correlates with the variable compartmental pattern of GABAA receptor and cell loss in the striatum. To determine whether the phenotypic variability in Huntingtons disease is also related to variable neuronal degeneration in the cerebral cortex, we undertook a double-blind study using unbiased stereological cell counting methods to determine the pattern of cell loss in the primary motor and anterior cingulate cortices in the brains of 12 cases of Huntingtons disease and 15 controls, and collected detailed data on the clinical symptomatology of the patients with Huntingtons disease from family members and clinical records. The results showed a significant association between: (i) pronounced motor dysfunction and cell loss in the primary motor cortex; and (ii) major mood symptomatology and cell loss in the anterior cingulate cortex. This association held for both total neuronal loss (neuronal N staining) and pyramidal cell loss (SMI32 staining), and also correlated with marked dystrophic changes in the remaining cortical neurons. There was also an association between cortical cell loss and striatal neuropathological grade, but no significant association with CAG repeat length in the Huntingtons disease gene. These findings suggest that the heterogeneity in clinical symptomatology that characterizes Huntingtons disease is associated with variation in the extent of cell loss in the corresponding functional regions of the cerebral cortex whereby motor dysfunction correlates with primary motor cortex cell loss and mood symptomatology is associated with cell loss in the cingulate cortex.

Cognitive and behavioural deficits associated with the orbitomedial prefrontal cortex in amyotrophic lateral sclerosis.

Amyotrophic lateral sclerosis, a progressive disease affecting motor neurons, may variably affect cognition and behaviour. We tested the hypothesis that functions associated with orbitomedial prefrontal cortex are affected by evaluating the behavioural and cognitive performance of 18 participants with amyotrophic lateral sclerosis without dementia and 18 healthy, matched controls. We measured Theory of Mind (Faux Pas Task), emotional prosody recognition (Aprosodia Battery), reversal of behaviour in response to changes in reward (Probabilistic Reversal Learning Task), decision making without risk (Holiday Apartment Task) and aberrant behaviour (Neuropsychiatric Inventory). We also assessed dorsolateral prefrontal function, using verbal and written fluency and planning (One-touch Stockings of Cambridge), to determine whether impairments in tasks sensitive to these two prefrontal regions co-occur. The patient group was significantly impaired at identifying social faux pas, recognizing emotions and decision-making, indicating mild, but consistent impairment on most measures sensitive to orbitomedial prefrontal cortex. Significant levels of aberrant behaviour were present in 50% of patients. Patients were also impaired on verbal fluency and planning. Individual subject analyses involved computing classical dissociations between tasks sensitive to different prefrontal regions. These revealed heterogeneous patterns of impaired and spared cognitive abilities: 33% of participants had classical dissociations involving orbitomedial prefrontal tasks, 17% had classical dissociations involving dorsolateral prefrontal tasks, 22% had classical dissociations between tasks of both regions, and 28% had no classical dissociations. These data indicate subtle changes in behaviour, emotional processing, decision-making and altered social awareness, associated with orbitomedial prefrontal cortex, may be present in a significant proportion of individuals with amyotrophic lateral sclerosis without dementia, some with no signs of dysfunction in tasks sensitive to other regions of prefrontal cortex. This demonstration of variability in cognitive integrity supports previous research indicating amyotrophic lateral sclerosis is a heterogeneous disease.

A retrospective study of the impact of lifestyle on age at onset of Huntington disease

In transgenic mouse models of Huntington disease (HD) environmental enrichment significantly delays disease onset. A questionnaire‐based survey of 154 adults with diagnosed HD (mean 4.2 years postdiagnosis) and a known IT15 CAG repeat length, explored whether premorbid lifestyle may relate to age‐at‐onset (AO). Participants were drawn from HD outpatient clinics in Australia and New Zealand. Premorbid physical, intellectual, and passive activity levels were used to generate scores in the categories of leisure, nonleisure (education, occupation and domestic duties) and total lifestyle. AO was associated with increased CAG repeat length as expected (r = −0.72, P < 0.001), but also with a lifestyle that included higher levels of passive activity (r = −0.38, P < 0.001). Multiple linear regression modeling showed lifestyle passivity to be a variable independent of CAG repeat length in predicting AO (R2 = 0.54, b = −0.22, P = 0.005). Comparison of the mean AO across tertiles of lifestyle passivity scores showed onset 4.6 years (95% CI = 1.3–7.9) later in the least compared with the most passive tertile. CAG repeat length was also shown to predict lifestyle passivity (R2 = 0.12, b = 1.08, P < 0.0005). Neither intellectual nor physical activity showed significant relationships to AO or CAG repeat length in this cohort. Our study leads to two conclusions: that a passive lifestyle may be a preclinical expression of HD, and that it actually contributes to the earlier onset of symptoms. Overcoming the tendency to be passive may substantially delay onset of HD.

Attention in musicians is more bilateral than in non-musicians.

Attention in neurologically intact adults normally errs towards the left side of space, as documented in studies involving tasks of visual attention (i.e., line bisection). The aim of this study was to further investigate lateralisation of attention in musicians and non-musicians. Reaction times and accuracy were recorded to stimuli presented to the left and right of a vertical line in 20 right-handed musicians and 20 matched non-musician controls. While both groups performed more accurately to left-sided stimuli, performance by the musician group was significantly more accurate than the non-musician group for the right-sided stimuli. Musicians also had faster reaction times overall. Consistent with previous research, the results indicate a more balanced attentional capacity in musicians, as well as enhanced visuomotor ability, and are interpreted with reference to extended musical training.

The virtual brain: 30 years of video-game play and cognitive abilities

Forty years have passed since video-games were first made widely available to the public and subsequently playing games has become a favorite past-time for many. Players continuously engage with dynamic visual displays with success contingent on the time-pressured deployment, and flexible allocation, of attention as well as precise bimanual movements. Evidence to date suggests that both brief and extensive exposure to video-game play can result in a broad range of enhancements to various cognitive faculties that generalize beyond the original context. Despite promise, video-game research is host to a number of methodological issues that require addressing before progress can be made in this area. Here an effort is made to consolidate the past 30 years of literature examining the effects of video-game play on cognitive faculties and, more recently, neural systems. Future work is required to identify the mechanism that allows the act of video-game play to generate such a broad range of generalized enhancements.

The unusual symmetry of musicians: Musicians have equilateral interhemispheric transfer for visual information

Previous behavioural research has shown that spatial attention is bilaterally represented in musicians, possibly reflecting more equal neural development between the hemispheres. We investigated this theory electrophysiologically with another measure that has shown asymmetry, interhemispheric transfer time (IHTT). Sixteen right-handed musicians and 16 matched non-musicians responded to stimuli presented to the left and right visual fields while 128-channel EEG was recorded. IHTT was calculated by comparing the latencies of occipital N1 components between hemispheres. Non-musicians showed significantly faster IHTT in the right-to-left direction than in the left-to-right direction and a shorter N1 latency in the left than in the right hemisphere. In contrast, the musician group showed no directional difference between hemispheres in IHTT, and no hemispheric difference in latency. These results indicate that musicians have more bilateral neural connectivity than non-musicians, reflected in an unusual lack of asymmetry. It is suggested that plastic developmental changes caused by extended musical training in childhood result in equally efficient connections to both hemispheres.