A combined working memory/repetition priming task was administered to 13 young (mean age 23) and 13 elderly (mean age 69) adults. Each participant memorized a sample target face at the beginning of a trial and then determined whether each of 13 serially presented test faces matched the sample target. In each trial, both the target and one particular distracter face were repeated during the test phase. Within-trial repetition priming effects indicated the contribution of implicit memory to task performance. Response times decreased as items were tested repeatedly within a trial, but this decrement was greater for distracters than for targets. Young and older participants were equally accurate at identifying targets, but elderly were slightly less accurate for distracters. Elderly participants showed repetition priming effects for both targets and distracters, while the young showed such effects only for distracters. The results suggest that active maintenance in working memory, but not inhibition or rejection of distracters, may suppress implicit memory systems.

Previously we reported that priming of visual motion perception is reduced in older adults compared to younger adults . To examine the neural mechanisms underlying this age-related effect, event-related brain potentials (ERPs) were recorded during perceptual judgments of motion directions by younger and older adults in two experiments. When judging single-step motion, both younger and older adults evoked significantly larger ERP late positive component (LPC) responses to unambiguous motion compared to LPC responses elicited by ambiguous motion. In contrast, compared to the younger adults, the older adults evoked comparable but delayed ERP responses to single motion steps. In the second experiment the younger and older groups judged the directions of two successive motion-steps (either motion priming or motion reversals). Under short (200-400 ms) stimulus onset asynchrony (SOA), the difference between the ERP responses to priming and reversal conditions was significantly larger for the younger than for the older adults. This study provides the first electrophysiological evidence that brain aging leads to delayed processing of single motion direction and visual motion priming as early as 100 ms in the early visual cortex. Age-related changes in strength and temporal characteristics of neural responses in temporal-parietal regions were particularly pronounced in older adults when successive motion signals are placed closely in time, within 400 ms.

A preliminary study by using visual working memory tasks coupled with quantified EEG (qEEG) analysis distinguished mild dementia subjects from normal aging ones with a high degree of accuracy. The present study hypothesizes that a simpler task such as having a subject count backwards mentally by ones can be coupled with qEEG to yield a similar degree of accuracy for classifying early dementia. The study focuses on participants with mild cognitive impairment (MCI) and includes both a delayed visual match-tosample (working memory) task and a counting backwards task (eyes closed) for comparison. The counting backwards protocol included 15 normal aging and 11 MCI participants, and the working memory task included 9 normal aging and 7 MCI individuals. The EEG data were quantified using Tsallis entropy, and the brain regions analyzed included the prefrontal cortex, occipital lobe, and the posterior parietal cortex. The

Amnestic mild cognitive impairment (MCI) is a degenerative neurological disorder at the early stage of Alzheimer's disease (AD). This work is a pilot study aimed at developing a simple scalp-EEG-based method for screening and monitoring MCI and AD. Specifically, the use of graphical analysis of inter-channel coherence of resting EEG for the detection of MCI and AD at early stages is explored. Resting EEG records from 48 age-matched subjects (mean age 75.7 years)-15 normal controls (NC), 16 with early-stage MCI, and 17 with early-stage AD-are examined. Network graphs are constructed using pairwise inter-channel coherence measures for delta-theta, alpha, beta, and gamma band frequencies. Network features are computed and used in a support vector machine model to discriminate among the three groups. Leave-one-out cross-validation discrimination accuracies of 93.6% for MCI vs. NC (p < 0.0003), 93.8% for AD vs. NC (p < 0.0003), and 97.0% for MCI vs. AD (p < 0.0003) are achieved. These results suggest the potential for graphical analysis of resting EEG inter-channel coherence as an efficacious method for noninvasive screening for MCI and early AD.

Objectives: By use of purer indices of PM and RM components than previous studies and adoption of three PM task types, the present study aimed to investigate the deficits of these two components underlying global impairment at a PM task in individuals with amnestic mild cognitive impairment (aMCI). Methods: Nineteen aMCI patients and 22 normal controls were examined on event-, time-and activity-based PM tasks. Separate scores were obtained for initiation of intentions (i.e. PM component) and for the content of the intentions (i.e. RM component).

Metacognitive theories propose that consumers track fluency feelings when buying, which may have biological underpinnings. We explored this using event-related potential (ERP) measures as twenty highmath anxiety (High MA) and nineteen low-math anxiety (Low MA) consumers made buying decisions for promoted (e.g., 15% discount) and non-promoted products. When evaluating prices, ERP correlates of higher perceptual and conceptual fluency were associated with buys, however only for High MA females under no promotions. In contrast, High MA females and Low MA males demonstrated greater FN400 amplitude, associated with enhanced conceptual processing, to prices of buys relative to non-buys under promotions. Concurrent late positive component (LPC) differences under no promotions suggest discrepant retrieval processes during price evaluations between consumer groups. When making decisions to buy or not, larger (smaller) P3, sensitive to outcome responses in the brain, was associated with buying for High MA females (Low MA females) under promotions, an effect also present for males under no promotions. Thus, P3 indexed decisions to buy differently between anxiety groups, but only for promoted items among females and for no promotions among males. Our findings indicate that perceptual and conceptual processes interact with anxiety and gender to modulate brain responses during consumer choices.

The ability of the eyes and brain to predict and track visible and occluded moving targets is essential to goaldirected action. Event-related functional MRI and eyemovements were simultaneously measured during a smooth pursuit task with different levels of visual cuing. Subjects tracked a white dot moving from left to right following a sinusoidal pattern, during which it could be seen over half the screen (visible condition) before disappearing behind the occlusion bar (occluded condition). When tracking occluded, moving targets, we observed a hemisphere asymmetry at the early visual cortex, but not in motion-processing area MT/ V5. During eye-tracking, the left early visual cortex responded stronger than the right to visible targets, but the right responded stronger to occluded targets. In contrast, motion-processing area MT/V5 in both hemispheres favored visible over occluded targets. These results suggest the right early visual cortex is the mind's eye, receiving input from higher level memory regions to produce simulated vision during occlusion.

The present study used event-related potentials (ERPs) to investigate the underlying neural mechanisms of visual affective priming. Eighteen young native English-speakers (6 males, 12 females) participated in the study. Two sets of 720 prime-target pairs (240 affectively congruent, 240 affectively incongruent, and 240 neutral) used either words or pictures as primes and only words as targets. ERPs were recorded from 64 scalp electrodes while participants pressed either "Happy" or "Sad" buttons to indicate target pleasantness. The response time (RT) results confirmed an affective priming effect, with faster responses to affectively congruent trials (659 ms) than affectively incongruent trials (690 ms). Affectively incongruent trials had larger and more negative N200 activation than those to neutral trials. Importantly, a delayed N400 for word prime-target pairs matched the RT results with larger negative amplitudes for incongruent than congruent pairs. This finding suggests that the N400 component is not only sensitive to semantic mismatches, but is also sensitive to affective mismatches for word prime-target pairs.

In two experiments, the temporal dynamics of neural activity underlying perceptual priming of visual motion was examined using event-related potentials (ERPs) during directional judgments of the apparent motion of two-dimensional sine-wave gratings. Compared to perceptually ambiguous motion, unambiguous left-or rightward motion was associated with enhanced ERP activity about 300 ms after the onset of apparent motion. In the second experiment, ERPs were recorded to two successive motion jumps in which an unambiguous motion jump served as a prime for a subsequent target motion that was ambiguous. The prime-target time interval was varied between 200, 400, and 1000 ms. In a control (motion reversal) condition, the two motion jumps were both unambiguous but in opposite directions. Compared to the motion reversal condition, motion priming was associated with an enhancement of ERP amplitudes at 100 ms and 350 ms following target stimulus onset. ERP enhancement was greatest at a short prime-target interval of 200 ms, which was also associated behaviorally with the strongest priming. The ERP enhancement and behavioral priming were both eliminated at the long 1000 ms prime-target interval. Functional magnetic resonance imaging (fMRI) data from a subset of subjects supported the view that motion priming involves modulation of neural responses both in early visual cortex and in later stages of visual processing.

To examine the neural mechanisms of working memory in children, event-related potentials (ERPs) were recorded from the 12 -13 year-old while they performed a delayed match-to-sample task. The ERP results revealed that new and studied objects both evoked a late positive ERP component peaking around 350 ms during the working memory process. New objects evoke a more positive ERP waveform than the studied objects. The scalp distribution showed that the frontal-central electrode sites were associated with object working memory processes. When tracking new or studied targets among visual distracters, ERPs of targets and distracters revealed differential responses as early as 150 ms. The visual targets evoked larger and more positive ERP responses than the distracters. The typical old-new effect was observed between ERPs of studied and new distracters. However, ERPs of new and studied targets differed at about 250 ms, in which new targets evoked more positive-going and slightly earlier ERP responses. In addition, a P3a component was found for new targets only, and was absent in ERPs of studied targets at frontal and central sites. The present study results reveal the spatial and temporal characteristics of neural mechanisms underlying working memory in children, some of which are distinct from those in adults.

We investigated brain responses to matching versus nonmatching objects in working memory with a modified delayed match-to-sample task using event-related potentials (ERPs). In addition, ERP correlates of new items (new matches/new nonmatches) and previously studied items (studied matches/studied nonmatches) were examined in the working memory task. Half of the common visual objects were initially studied until 95% accuracy was attained and half were new. Each memory trial began with the presentation of a sample object followed by nine test objects. Participants indicated whether each test item was the same as the object held in mind (i.e., match) or a nonmatch. Compared to studied matches, new matches evoked activity that was 50 msec earlier and largest at frontal sites. In contrast, P3 activity associated with studied nonmatches was larger than for new nonmatches at mostly posterior sites, which parallels previously reported oldnew ERP effects. The ERP source analysis further confirms that the cortical mechanisms underlying matching objects and rejecting irrelevant objects during the task are both temporally and spatially distinct. Moreover, our current findings suggest that prior learning affects brain responses to matching visual items during a working memory task.

When tracking visible or occluded moving targets, several frontal regions including the frontal eye fields (FEF), dorsal-lateral prefrontal cortex (DLPFC), and anterior cingulate cortex (ACC) are involved in smooth pursuit eye movements (SPEM). To investigate how these areas play different roles in predicting future locations of moving targets, 12 healthy college students participated in a smooth pursuit task of visual and occluded targets. Their eye movements and brain responses measured by event-related functional MRI were simultaneously recorded. Our results show that different visual cues resulted in time discrepancies between physical and estimated pursuit time only when the moving dot was occluded. Visible phase velocity gain was higher that that of occlusion phase. We found bilateral FEF association with eye-movement whether moving targets are visible or occluded. However, the DLPFC and ACC showed increased activity when tracking and predicting locations of occluded moving targets, and were suppressed during smooth pursuit of visible targets. When visual cues were increasingly available, less activation in the DLPFC and the ACC was observed. In addition, there was a significant hemisphere effect in DLPFC, where right DLPFC showed significantly increased responses over left when pursuing occluded moving targets. Correlation results revealed that DLPFC, the right DLPFC in particular, communicates more with FEF during tracking of occluded moving targets (from memory). The ACC modulates FEF more during tracking of visible targets (likely related to visual attention). Our results suggest that DLPFC and ACC modulate FEF and cortical networks differentially during visible and memory-guided eye tracking of moving targets. Hum Brain Mapp 30:3541-3552, in Wiley InterScience (www. interscience.wiley.com). V C 2009 Wiley-Liss, Inc. r Eye Tracking of Occluded Targets r r 3543 r r Eye Tracking of Occluded Targets r r 3551 r

Novel images and message content enhance visual attention and memory for high sensation seekers, but the neural mechanisms associated with this effect are unclear. To investigate the individual differences in brain responses to new and old (studied) visual stimuli, we utilized Event-related Potentials (ERP) and functional Magnetic Resonance Imaging (fMRI) measures to examine brain reactivity among high and low sensation seekers during a classic old-new memory recognition task. Twenty low and 20 high sensation seekers completed separate, but parallel, ERP and fMRI sessions. For each session, participants initially studied drawings of common images, and then performed an old-new recognition task during scanning. High sensation seekers showed greater ERP responses to new objects at the frontal N2 ERP component, compared to low sensation seekers. The ERP Novelty-N2 responses were correlated with fMRI responses in the orbitofrontal gyrus. Sensation seeking status also modulated the FN400 ERP component indexing familiarity and conceptual learning, along with fMRI responses in the caudate nucleus, which correlated with FN400 activity. No group differences were found in the late ERP positive components indexing classic old-new amplitude effects. Our combined ERP & fMRI results suggest that sensation-seeking personality affects the early brain responses to visual processing, but not the later stage of memory recognition.