There has been considerable debate as to whether the hippocampus and perirhinal cortex may subserve both memory and perception. We administered a series of oddity tasks, in which subjects selected the odd stimulus from a visual array, to amnesic patients with either selective hippocampal damage (HC group) or more extensive medial temporal damage, including the perirhinal cortex (MTL group). All patients performed normally when the stimuli could be discriminated using simple visual features, even if faces or complex virtual reality scenes were presented. Both patient groups were, however, severely impaired at scene discrimination when a significant demand was placed on processing spatial information across viewpoint independent representations, while only the MTL group showed a significant deficit in oddity judgments of faces and objects when object viewpoint independent perception was emphasized. These observations provide compelling evidence that the human hippocampus and perirhinal cortex are critical to processes beyond long-term declarative memory and may subserve spatial and object perception, respectively.

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We propose that transient epileptic amnesia is a distinctive epilepsy syndrome, typically misdiagnosed at presentation and associated with accelerated long-term forgetting and autobiographical amnesia. The syndrome is of clinical and theoretic importance.

This PET study has revealed the neural system involved in implicit face, proper-name and object name processing during an explicit visual 'same' versus 'different' matching task. Within the identified system, some areas were equally active irrespective of modality (faces or names) or type of stimuli (famous and non-famous) while other areas exhibited differential effects. Our findings support the hypothesis that faces and names involve differential pre-semantic processing prior to accessing a common neural system of stored knowledge of personal identity which overlaps with the one associated with object knowledge. The areas specialized for the perceptual analysis of faces (irrespective of whether they are famous or non-famous) are the right lingual and bilateral fusiform gyri, while the areas specialized for famous stimuli (irrespective of whether they are faces or names) spread from the left anterior temporal to the left temporoparietal regions. One specific area, the more lateral portion of the left anterior middle temporal gyrus, showed increased activation for famous faces relative to famous proper names and for famous proper names relative to common names. The differential responsiveness of this region when processing familiar people suggests functional segregation of either personal attributes or, more likely, the demands placed on processes that retrieve stored knowledge when stimuli have highly similar visual features but unique semantic associations.

Why do some people have superior memory capabilities? We addressed this age-old question by examining individuals renowned for outstanding memory feats in forums such as the World Memory Championships. Using neuropsychological measures, as well as structural and functional brain imaging, we found that superior memory was not driven by exceptional intellectual ability or structural brain differences. Rather, we found that superior memorizers used a spatial learning strategy, engaging brain regions such as the hippocampus that are critical for memory and for spatial memory in particular. These results illustrate how functional neuroimaging might prove valuable in delineating the neural substrates of mnemonic techniques, which could broaden the scope for memory improvement in the general population and the memory-impaired.

This case study describes the use of a wearable camera, SenseCam, which automatically captures several hundred images per day, to aid autobiographical memory in a patient, Mrs B, with severe memory impairment following limbic encephalitis. By using SenseCam to record personally experienced events we intended that SenseCam pictures would form a pictorial diary to cue and consolidate autobiographical memories. After wearing SenseCam, Mrs B plugged the camera into a PC which uploaded the recorded images and allowed them to be viewed at speed, like watching a movie. In the control condition, a written diary was used to record and remind her of autobiographical events. After viewing SenseCam images, Mrs B was able to recall approximately 80% of recent, personally experienced events. Retention of events was maintained in the long-term, 11 months afterwards, and without viewing SenseCam images for three months. After using the written diary, Mrs B was able to remember around 49% of an event; after one month with no diary readings she had no recall of the same events. We suggest that factors relating to rehearsal/re-consolidation may have enabled SenseCam images to improve Mrs B's autobiographical recollection.

The aim in this review article is to document research findings that have shown paradoxical effects of nervous system changes, whereby direct or indirect neural damage may result in facilitation of behavioural functions. Such findings have often been ignored or undervalued in the brain-behaviour research literature. A further aim is to consider possible mechanisms and theoretical insights related to this facilitation. Analyses of relevant studies show that two major types of paradoxical functional facilitation (PFF) effects may be distinguished. (i) Situations where damage to intact brain tissue brings to normal or near normal a previously subnormal or abnormal level of functioning. I refer to improved levels of functioning in such contexts as restorative PFF effects. One of the best documented examples of such PFF effects is the 'Sprague effect', whereby collicular lesions may bring about an improvement in visual functioning following an initial occipital lesion. (ii) Situations where a subject with nervous system pathology or sensory loss performs better than normal control subjects on a particular task. I refer to improved levels of performance in these contexts as enhancing PFF effects. Restorative and enhancing PFF effects have been found in a range of domains, including memory, sensory and perceptual functions, and language functioning. A potential contribution of PFF effects is that they highlight two important neural mechanisms, i.e. inhibition and compensatory plasticity. Two broad classes of theoretical insights related to PFF effects are therefore discussed: (i) inhibitory mechanisms, which form part of an interactive view of brain function where competitive opponent-processing is a significant feature; (ii) 'compensatory augmentation', which occurs as a specific manifestation of CNS plasticity. Both of these mechanisms are considered in relation to paradoxical increases in CBF and anatomical annexation effects that are seen in neurological patients and in subjects with sensory loss. Paradoxical functional facilitation paradigms represent a powerful methodological tool for confirming or refuting hypotheses in brain-behaviour research. The counter-intuitive nature of PFF findings provides a particularly persuasive set of evidence in support of neural, conceptual or computational models of brain function that specifically predict paradoxical facilitation of cognitive functioning.