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 eventrelated 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 roterehearsed 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. &

studies, which offer higher spatial resolution, will shed new light on when and why encoding yields subsequent remembering. Keywords: subsequent memory effect; episodic encoding; episodic memory; event-related potentials; fMRI; PET 1. INTRODUCTION In the course of a typical day, humans experience many complex events: perceiving faces and other objects, reading words and text passages, interpreting the meaning of spoken phrases, and the like. Yet, at the end of the day, only a subset of these experiences are memorable, with many of the day's events having been forgotten. To understand human memory, it is critically important to determine why some experiences can be later remembered, whereas others are subsequently forgotten. Considerable behavioural and neuropsychological evidence indicates that the ability to remember a given experience is affected by many factors, including the kinds of processing operations that are engaged at the time of encoding and retrieval, and interactions

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this memoryenhancing effect of emotion and their temporal aspects, in particular, are not well understood. Taking advantage of the temporal resolution of event-related potentials (ERPs), we investigated the time-course of the electrophysiological correlates of encoding pleasant, unpleasant, and neutral pictures

Event-related potentials (ERPs) were recorded while subjects made old/new recognition judgments on new unstudied words and old words which had been presented at study either once (`weak') or three times (`strong'). The probability of an `old' response was significantly higher for strong than weak words and significantly higher for weak than new words. Comparisons were made initially between ERPs to new, weak and strong words, and subsequently between ERPs associated with six strength-by-response conditions. The N400 component was found to be modulated by memory trace strength in a graded manner. Its amplitude was most negative in new word ERPs and most positive in strong word ERPs. This `N400 strength effect' was largest at the left parietal electrode (in ear-referenced ERPs). The amplitude of the late positive complex (LPC) effect was sensitive to decision accuracy (and perhaps confidence). Its amplitude was larger in ERPs evoked by words attracting correct versus incorrect recognition decisions. The LPC effect had a left > right, centro-parietal scalp topography (in ear-referenced ERPs). Hence, whereas, the majority of previous ERP studies of episodic recognition have interpreted results from the perspective of dual-process models, we provide alternative interpretations of N400 and LPC old/new effects in terms of memory strength and decisional factor(s).

For some years, the limits of classic reliability theory have been recognized in favor of the Generalizability Theory, which deals simultaneously with multiple sources of error. This measurement model can be particularly useful when applied to research in cognitive psychophysiology. Indeed, studies in this field often deal with estimated measures whose reliability is rarely taken into account. In this paper, we report two generalizability studies in order to investigate the usefulness of G theory in providing information about the reliability of experimental results. The first was carried out on P300 measured during an oddball task, and the second was carried out on ERPs recorded during a recognition memory task. As expected, results showed that P300 modulation was more reliable than ERP memory modulation. This suggests that G theory can be a useful tool to estimate the reliability of psychophysiological findings, complementing and extending results from conventional analyses.

To uncover the neural bases of a cognitive process it is important both to identify the participating brain regions and determine the precise time course of information transmission within and among those regions. Although neuroimaging techniques based on cerebral blood flow or metabolism (e.g., positron emission tomography [PET]and functional magnetic resonance imaging [fMRI]) are providing increasingly detailed pictures of the anatomic regions activated during cognitive activity, these methods lack the temporal resolution to reveal the rapid-fire patterning of neuronal communication. Noninvasive recordings of the electrical and magnetic fields generated by active neuronal populations, however, can reveal the timing of brain activity related to cognition with a very high, msec-level resolution. This chapter gives an overview of how these temporally precise recording techniques have been used to analyze perceptual and cognitive mechanisms in the human brain. The changes in field potentials that are time-locked to sensory, motor, or cognitive events are known as eventrelated potentials (ERPs) and the corresponding magnetic field changes are termed event-related fields (ERFs). Both ERPs and ERFs consist of precisely timed sequences of waves of varying field strength and polarity (Fig. 32.1). These observed peaks and troughs in the waveform are often referred to as ‘‘components.’ ’ Some authors, however, prefer to use the term component to refer to portions of the waveform that originate from particular neural structures, whereas others consider ERP/ERF components to be those waveform features that are associated with a particular cognitive process or manipulation (2). Both ERPs and ERFs are generated primarily by the flow of ionic currents in elongated nerve cells during synaptic activity. Whereas synaptic currents flowing across nerve cell membranes into the

iteria. Declarative Memory Observations of preserved and impaired memory in patients with amnesia indicate that the recall and recognition of facts and episodes, or declarative memory, is dependent on a particular subset of brain regions and can be disrupted selectively. How can we develop a better understanding of this selectivity? Indeed, one might pose the question: Why is declarative memory different from all other forms of memory? Here are four answers to this question: 1. Because declarative memory has distinct behavioral characteristics. 2. Because declarative memory has distinct subjective characteristics. 3. Because declarative memory has a distinct cognitive structure. 4. Because declarative memory has distinct neural substrates. Memory theorists tend to give one or another of these answers greater emphasis, as discussed further below. In any event, determi

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Advancing age is associated with a decline in physical and cognitive abilities. Multiple theories have been proposed to account for the psychological impairments seen in older age. These include changes in sensory acuity, general slowing of the nervous system, declines in working memory capacity, and a loss of inhibitory control. Although not inherently incompatible, each of the theories provides a unique interpretation of the observed pattern of psychological and neuronal data. To test the veracity of the inhibitory theory a series of experiments was performed. The first experiment used functional magnetic resonance imaging (fMRI) to assess a classical Sternberg paradigm with five increasing levels of cognitive demand ranging from a set size of two letters up to six letters. Comparisons of mean levels of recruitment and inhibition were done between younger and older adults revealing that older adults greatly over recruit but under inhibit areas of the brain compared to their younger counterparts. A region of interest analysis revealed that older adults recruit tissue in a linear fashion from almost all areas in the task evoked visual and attentional networks while younger adults modulate the activity in only a subset of regions.