Event-related functional magnetic resonance imaging of a low dose of dexmedetomidine that impairs long-term memory.

Background: Work suggests the amnesia from dexmedetomidine (an α2-adrenergic agonist) is caused by a failure of information to be encoded into long-term memory and that dexmedetomidine might differentially affect memory for emotionally arousing material. We investigated these issues in humans using event-related neuroimaging to reveal alterations in brain activity and subsequent memory effects associated with drug exposure.

Methods: Forty-eight healthy volunteers received a computer-controlled infusion of either placebo or low-dose dexmedetomidine (target = 0.

Returning from oblivion: imaging the neural core of consciousness.

One of the greatest challenges of modern neuroscience is to discover the neural mechanisms of consciousness and to explain how they produce the conscious state. We sought the underlying neural substrate of human consciousness by manipulating the level of consciousness in volunteers with anesthetic agents and visualizing the resultant changes in brain activity using regional cerebral blood flow imaging with positron emission tomography. Study design and methodology were chosen to dissociate the state-related changes in consciousness from the effects of the anesthetic drugs.

Overlap between the neural correlates of cued recall and source memory: evidence for a generic recollection network?

Recall of a studied item and retrieval of its encoding context (source memory) both depend on recollection of qualitative information about the study episode. This study investigated whether recall and source memory engage overlapping neural regions. Participants (n = 18) studied a series of words, which were presented either to the left or right of fixation.

Right dorsolateral prefrontal cortex is engaged during post-retrieval processing of both episodic and semantic information.

Post-retrieval processes are engaged when the outcome of a retrieval attempt must be monitored or evaluated. Functional neuroimaging studies have implicated right dorsolateral prefrontal cortex (DLPFC) as playing a role in post-retrieval processing. The present study used fMRI to investigate whether retrieval-related neural activity in DLPFC is associated specifically with monitoring the episodic content of a retrieval attempt.

The relationship between the right frontal old/new ERP effect and post-retrieval monitoring: specific or non-specific?

Post-retrieval processes are thought to be engaged when the outcome of an attempt to retrieve information from long-term memory must be monitored or evaluated. Previous research employing event-related potentials (ERPs) has implicated a specific ERP modulation - the 'right frontal old/new effect' - as a correlate of post-retrieval processing. In two experiments we examined whether the right frontal effect is specifically associated with processing of the products of an episodic retrieval attempt.

Electrophysiological dissociation of the neural correlates of recollection and familiarity.

Event-related potentials (ERPs) were employed to investigate electrophysiological correlates of recognition memory in a task that allowed segregation of test items according to whether they were recollected (operationalized by introspective report) or, if recollection failed, their level of familiarity (operationalized by recognition confidence). The amplitude of a negative-going ERP deflection that onsets around 300 ms post-stimulus varied inversely with familiarity strength. This effect was maximal over the left frontal scalp.