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One of the features of both adult-onset and developmental forms of amnesia resulting from bilateral medial temporal lobe damage, or even from relatively selective damage to the hippocampus, is the sparing of working memory. Recently, however, a number of studies have reported deficits on working memory tasks in patients with damage to the hippocampus and in macaque monkeys with neonatal hippocampal lesions. These studies suggest that successful performance on working memory tasks with high memory load require the contribution of the hippocampus. Here we compared performance on a working memory task (the Self-ordered Pointing Task), between patients with early onset hippocampal damage and a group of healthy controls. Consistent with the findings in the monkeys with neonatal lesions, we found that the patients were impaired on the task, but only on blocks of trials with intermediate memory load. Importantly, only intermediate to high memory load blocks yielded significant correlations between task performance and hippocampal volume. Additionally, we found no evidence of proactive interference in either group, and no evidence of an effect of time since injury on performance. We discuss the role of the hippocampus and its interactions with the prefrontal cortex in serving working memory. [ABSTRACT FROM AUTHOR]

Abstract: Compared to adults, relatively little is known about autobiographical memory and the ability to imagine fictitious and future scenarios in school-aged children, despite the importance of these functions for development and subsequent independent living. Even less is understood about the effect of early hippocampal damage on children''s memory and imagination abilities. To bridge this gap, we devised a novel naturalistic autobiographical memory task that enabled us to formally assess the memory for recent autobiographical experiences in healthy school-aged children. Contemporaneous with the autobiographical memories being formed, the children also imagined and described fictitious scenarios. Having established the performance of healthy school-aged children on these tasks, we proceeded to make comparisons with children (n =21) who had experienced neonatal hypoxia/ischaemia, and consequent bilateral hippocampal damage. Our results showed that healthy children could recall autobiographical events, including spatiotemporal information and specific episodic details. By contrast, children who had experienced neonatal hypoxia/ischaemia had impaired recall, with the specific details of episodes being lost. Despite this significant memory deficit they were able to construct fictitious scenarios. This is in clear contrast to adults with hippocampal damage, who typically have impaired autobiographical memory and deficits in the construction of fictitious and future scenarios. We speculate that the paediatric patients’ relatively intact semantic memory and/or some functionality in their residual hippocampi may underpin their scene construction ability. [Copyright &y& Elsevier]

Abstract: Detailed study of the autobiographical memory (ABM) impairments seen in different forms of degenerative dementia, in particular Alzheimer''s disease (AD) and semantic dementia (SD) can inform neuropsychological models of memory. A modified ABM questionnaire which allowed more detailed analysis of episodic and semantic ABM was used to study the pattern of deficits in patients with minimal to mild Alzheimer''s disease (AD) and in two patients with mild and moderate semantic dementia (SD). The questionnaire tested both cued and free recall. A group of healthy elderly was also tested. AD patients differed from controls in all measures. There was no clear temporal gradient for episodic ABM, but a modest gradient was observed for semantic ABM. The mild SD patient performed at control level for episodic ABM but showed a deficit within the range of the AD patients for semantic ABM except for the most recent life period. In contrast the moderate SD patient was impaired within the range of the AD patients for both episodic and semantic ABM. The evidence for differential impairment of episodic and semantic ABM retrieval in AD and SD is interpreted as supporting the multiple trace model of memory. [Copyright &y& Elsevier]

Abstract: Confabulation in Alzheimer''s disease (AD) has been the subject of limited investigation. When studied, the phenomenon has been found to share characteristics with memory distortions produced by neurologically intact individuals. Previous studies that have investigated confabulation in AD have failed to take into account the characteristics of the disease and the presence of confabulations in the retrieval of recent autobiographical memory (ABM). The aim of this study was to develop a test that could investigate the tendency to confabulate in recent autobiographical memory that was specifically created for eliciting confabulatory behaviours in patients with AD. Four experiments have been carried out. In Experiment 1, AD patients who have yet to show confabulatory behaviour were compared to elderly adults. The results revealed that AD patients produced significantly more confabulations on the new test compared to elderly adults. Experiment 2 investigated if the results of the initial experiment were due to AD patients having limited working memory capacity that would lead to difficulties in performing the test compared with elderly adults as AD patients would be in a condition of memory overload. The results showed that even when compared with the performance of elderly individuals under memory overload condition, AD patients still produced more confabulations than elderly adults. Using a correlational approach Experiments 3 and 4 revealed that a high production of provoked confabulatory answers were associated with poor scores on personal episodic memory measures but not with other measures of cognitive functioning such as working memory and/or executive function. [Copyright &y& Elsevier]

Theory of Mind (ToM) forms an integral component of socially skilled behavior, and is critical for attaining developmentally appropriate goals. The protracted development of ToM is mediated by increasing connectivity between regions of the anatomically distributed ‘mentalizing network’, and may be vulnerable to disruption from pediatric traumatic brain injury (TBI). The present study aimed to evaluate the post-acute effects of TBI on first-order ToM, and examine relations between ToM and both local and global indices of macrostructural damage detected using susceptibility-weighted imaging (SWI). 104 children and adolescents with TBI and 43 age-matched typically developing (TD) controls underwent magnetic resonance imaging including a susceptibility-weighted imaging (SWI) sequence 2–8 weeks post-injury and were assessed on cognitive ToM tasks at 6-months after injury. Compared to TD controls and children with mild-moderate injuries, children with severe TBI showed significantly poorer ToM. Moreover, impairments in ToM were related to diffuse neuropathology, and parietal lobe lesions. Our findings support the vulnerability of the immature social brain network to disruption from TBI, and suggest that global macrostructural damage commonly associated with traumatic axonal injury (TAI) may contribute to structural disconnection of anatomically distributed regions that underlie ToM. This study suggests that SWI may be a valuable imaging biomarker to predict outcome and recovery of social cognition after pediatric TBI. [ABSTRACT FROM AUTHOR]