Episodic memory--from brain to mind

Neuronal mechanisms of episodic memory, the conscious recollection of autobiographical events, are largely unknown because electrophysiological studies in humans are conducted only in exceptional circumstances. Unit recording studies in animals are thus crucial for understanding the neurophysiological substrate that enables people to remember their individual past. Two features of episodic memory--autonoetic consciousness, the self-aware ability to "travel through time", and one-trial learning, the acquisition of information in one occurrence of the event--raise important questions about the validity of animal models and the ability of unit recording studies to capture essential aspects of memory for episodes. We argue that autonoetic experience is a feature of human consciousness rather than an obligatory aspect of memory for episodes, and that episodic memory is reconstructive and thus its key features can be modeled in animal behavioral tasks that do not involve either autonoetic consciousness or one-trial learning. We propose that the most powerful strategy for investigating neurophysiological mechanisms of episodic memory entails recording unit activity in brain areas homologous to those required for episodic memory in humans (e.g., hippocampus and prefrontal cortex) as animals perform tasks with explicitly defined episodic-like aspects. Within this framework, empirical data suggest that the basic structure of episodic memory is a temporally extended representation that distinguishes the beginning from the end of an event. Future research is needed to fully understand how neural encodings of context, sequences of items/events, and goals are integrated within mnemonic representations of autobiographical events.     

Near-infrared optical imaging of human brain function--a novel approach to the brain and the mind]

Near-infrared spectroscopy (NIRS) can measure changes in the hemoglobin oxygenation state in the human brain. NIRS has been oriented toward use for clinical monitoring of tissue oxygenation. However, we and others have recently demonstrated that NIRS also has the potential for neuroimaging. NIRS instruments, which use continuous wave light (CW) as a light source, are now commercially available. These CW-type NIRS instruments have high temporal resolution (less than 1 second) and allow long-term and continuous measurements, though they do not provide absolute values of changes in hemoglobin concentrations. In contrast, time-resolved spectroscopy (TRS), which uses short pulsed laser diodes as light sources, makes quantification possible. Quantification is necessary for the imaging of brain activity. Topographical images can be obtained by the use of our recently developed 64-channel time-resolved optical tomographic imaging system (optical CT) or by combining the 1 channel TRS instrument with the multichannel CW-type NIRS instrument. NIRS is completely non-invasive and does not require strict motion restriction during measurements unlike PET and fMRI. It is, thus, expected that NIRS will open a window into brain physiology in subjects who are difficult to examine with PET and fMRI such as children, the elderly, and patients with psychoneurological problems.     

Implementation of intensive follow-up in the community: lessons to be considered]

OBJECTIVE: To examine various issues concerning the implementation of a program for assertive community treatment (ACT). METHOD: In-depth interviews were conducted with participants of an ACT project implemented in the 1970s. A quality analysis was undertaken, assessing the issues that prevented the expansion of such an approach as well as issues to be considered in future implementation of ACT. RESULTS: Social, cultural, organizational, professional, and economic factors were identified that will continue to play decisive roles in the integration of such a program. The ACT implementation in question occurred at the same time as the shift to community psychiatry, without having been linked to that approach. Currently, social factors such as self-help groups and parents foster the implementation of such programs. The organizational factors include the importance of linking ACT to existing health care services, as well as adapting ACT to these services. The association of this type of project with a research team did not ensure a successful implementation. A third factor is the psychiatrist's training and motivation with respect to the practice of this approach. Finally, economic issues are playing a larger role in the implementation of this approach. CONCLUSION: This study relates different issues regarding the implementation of an ACT. The results represent assumptions that need to be confirmed by assessing ACT implementation in Quebec as well as in the rest of Canada.     

Nervous system Lyme borreliosis--revisited [corrected; erratum to be published]

A great deal of confusion surrounds the diagnosis, clinical phenomenology, and treatment of Lyme borreliosis. Most diagnostic methods currently in use are indirect and do not differentiate between prior exposure and current infection. A critical review of the literature permits the characterization of a distinct set of neurologic disorders that are almost certainly caused by this infection and their differentiation from the plethora of syndromes that have been anecdotally linked to infection, but in which causality has never been established. This article describes the range of clinical disorders associated with Lyme borreliosis, provides an overview of current approaches to diagnosis, and reviews current treatment protocols.     

Efforts to preserve the mind in contemporary hospital treatment

The author proposes a restructured and refocused extended length-of-stay inpatient treatment program designed to maintain an emphasis on the whole person. He suggests that the conditions for implementing a genuine biopsychosocial approach to treatment are now more possible than ever before. Note is made of the evolution of the new structures, the change in treatment constraints, and the type of patient currently presenting for inpatient treatment. Modifications of traditional and current inpatient treatment strategies, especially the formal inclusion of the patient on the multidisciplinary treatment team, enable the restructuring to focus on treatment recalcitrance, on establishing and reestablishing flexible mental processes, and on promoting community reintegration and tenure.     

Learning to move machines with the mind

Brain-computer interfaces (BCIs) extract signals from neural activity to control remote devices ranging from computer cursors to limb-like robots. They show great potential to help patients with severe motor deficits perform everyday tasks without the constant assistance of caregivers. Understanding the neural mechanisms by which subjects use BCI systems could lead to improved designs and provide unique insights into normal motor control and skill acquisition. However, reports vary considerably about how much training is required to use a BCI system, the degree to which performance improves with practice and the underlying neural mechanisms. This review examines these diverse findings, their potential relationship with motor learning during overt arm movements, and other outstanding questions concerning the volitional control of BCI systems.     

When keeping in mind supports later bringing to mind: neural markers of phonological rehearsal predict subsequent remembering.

The ability to bring to mind a past experience depends on the cognitive and neural processes that are engaged during the experience and that support memory formation. A central and much debated question is whether the processes that underlie rote verbal rehearsal-that is, working memory mechanisms that keep information in mind-impact memory formation and subsequent remembering. The present study used event-related functional magnetic resonance imaging (fMRI) to explore the relation between working memory maintenance operations and long-term memory. Specifically, we investigated whether the magnitude of activation in neural regions supporting the on-line maintenance of verbal codes is predictive of subsequent memory for words that were rote-rehearsed during learning. Furthermore, during rote rehearsal, the extent of neural activation in regions associated with semantic retrieval was assessed to determine the role that incidental semantic elaboration may play in subsequent memory for rote-rehearsed items. Results revealed that (a) the magnitude of activation in neural regions previously associated with phonological rehearsal (left prefrontal, bilateral parietal, supplementary motor, and cerebellar regions) was correlated with subsequent memory, and (b) while rote rehearsal did not--on average--elicit activation in an anterior left prefrontal region associated with semantic retrieval, activation in this region was greater for trials that were subsequently better remembered. Contrary to the prevalent view that rote rehearsal does not impact learning, these data suggest that phonological maintenance mechanisms, in addition to semantic elaboration, support the encoding of an experience such that it can be later remembered.