Response bias and response monitoring: Evidence from healthy older adults and patients with mild Alzheimer's disease.

Patients with Alzheimer's disease (AD) often exhibit an abnormally liberal response bias in recognition memory tests, responding "old" more frequently than "new." Investigations have shown patients can to shift to a more conservative response bias when given instructions. We examined if patients with mild AD could alter their response patterns when the ratio of old items is manipulated without explicit instruction.

Family History of Alzheimer's Disease is Associated with Impaired Perceptual Discrimination of Novel Objects.

Early detection may be the key to developing therapies that will combat Alzheimer's disease (AD). It has been consistently demonstrated that one of the main pathologies of AD, tau, is present in the brain decades before a clinical diagnosis. Tau pathology follows a stereotypical route through the medial temporal lobe beginning in the entorhinal and perirhinal cortices.

Preserved conceptual implicit memory for pictures in patients with Alzheimer's disease.

The current study examined different aspects of conceptual implicit memory in patients with mild Alzheimer's disease (AD). Specifically, we were interested in whether priming of distinctive conceptual features versus general semantic information related to pictures and words would differ for the mild AD patients and healthy older adults. In this study, 14 healthy older adults and 15 patients with mild AD studied both pictures and words followed by an implicit test section, where they were asked about distinctive conceptual or general semantic information related to the items they had previously studied (or novel items).

Clinical Feasibility of 2-Dimensional Video Analysis of Active Cervical Motion in Congenital Muscular Torticollis.

Purpose: The purpose of this study was to evaluate the clinical feasibility of using a 2-dimensional (2D) video analysis (VA) system compared with visual estimation (VE) for measurement of active cervical rotation and lateral flexion in infants with congenital muscular torticollis.

Methods: Twelve infants participated in this study. Active cervical motion in rotation and lateral flexion was measured by VE and 2D VA.

The temporal dynamics of visual object priming.

Priming reflects an important means of learning that is mediated by implicit memory. Importantly, priming occurs for previously viewed objects (item-specific priming) and their category relatives (category-wide priming). Two distinct neural mechanisms are known to mediate priming, including the sharpening of a neural object representation and the retrieval of stimulus-response mappings.

The effect of echo time and post-processing procedure on blood oxygenation level-dependent (BOLD) functional connectivity analysis.

While spontaneous BOLD fMRI signal is a common tool to map functional connectivity, unexplained inter- and intra-subject variability frequently complicates interpretation. Similar to evoked BOLD fMRI responses, spontaneous BOLD signal is expected to vary with echo time (TE) and corresponding intra/extravascular sensitivity. This may contribute to discrepant conclusions even following identical post-processing pipelines.

Memory-related eye movements challenge behavioral measures of pattern completion and pattern separation.

The hippocampus creates distinct episodes from highly similar events through a process called pattern separation and can retrieve memories from partial or degraded cues through a process called pattern completion. These processes have been studied in humans using tasks where participants must distinguish studied items from perceptually similar lure items. False alarms to lures (incorrectly reporting a perceptually similar item as previously studied) are thought to reflect pattern completion, a retrieval-based process.

Understanding age-related reductions in visual working memory capacity: examining the stages of change detection.

Visual working memory (VWM) capacity is reduced in older adults. Research has shown age-related impairments to VWM encoding, but aging is likely to affect multiple stages of VWM. In the present study, we recorded the event-related potentials (ERPs) of younger and older adults during VWM maintenance and retrieval.

γ-Aminobutyric acid (GABA) concentration inversely correlates with basal perfusion in human occipital lobe.

Commonly used neuroimaging approaches in humans exploit hemodynamic or metabolic indicators of brain function. However, fundamental gaps remain in our ability to relate such hemo-metabolic reactivity to neurotransmission, with recent reports providing paradoxical information regarding the relationship among basal perfusion, functional imaging contrast, and neurotransmission in awake humans. Here, sequential magnetic resonance spectroscopy (MRS) measurements of the primary inhibitory neurotransmitter, γ-aminobutyric acid (GABA+macromolecules normalized by the complex N-acetyl aspartate-N-acetyl aspartyl glutamic acid: [GABA(+)]/[NAA-NAAG]), and magnetic resonance imaging (MRI) measurements of perfusion, fractional gray-matter volume, and arterial arrival time (AAT) are recorded in human visual cortex from a controlled cohort of young adult male volunteers with neurocognitive battery-confirmed comparable cognitive capacity (3 T; n=16; age=23±3 years).

Pattern separation and pattern completion in Alzheimer's disease: evidence of rapid forgetting in amnestic mild cognitive impairment.

Over the past four decades, the characterization of memory loss associated with Alzheimer's disease (AD) has been extensively debated. Recent iterations have focused on disordered encoding versus rapid forgetting. To address this issue, we used a behavioral pattern separation task to assess the ability of the hippocampus to create and maintain distinct and orthogonalized visual memory representations in patients with amnestic mild cognitive impairment (aMCI) and mild AD.

Vessel-encoded arterial spin labeling (VE-ASL) reveals elevated flow territory asymmetry in older adults with substandard verbal memory performance.

Purpose: To evaluate how flow territory asymmetry and/or the distribution of blood through collateral pathways may adversely affect the brain's ability to respond to age-related changes in brain function. These patterns have been investigated in cerebrovascular disease; however, here we evaluated how flow-territory asymmetry related to memory generally in older adults.

Materials And Methods: A multi-faceted MRI protocol, including vessel-encoded arterial spin labeling capable of flow territory mapping, was applied to assess how flow territory asymmetry; memory performance (CERAD-Immediate Recall); cortical cerebral blood flow (CBF), white matter lesion (WML) count, and cortical gray matter volume were related in older healthy control volunteers (HC; n = 15; age = 64.

Electrophysiological distinctions between recognition memory with and without awareness.

The influence of implicit memory representations on explicit recognition may help to explain cases of accurate recognition decisions made with high uncertainty. During a recognition task, implicit memory may enhance the fluency of a test item, biasing decision processes to endorse it as "old". This model may help explain recognition-without-identification, a remarkable phenomenon in which participants make highly accurate recognition decisions despite the inability to identify the test item.

Inverse correspondence between hippocampal perfusion and verbal memory performance in older adults.

Understanding physiological changes that precede irreversible tissue damage in age-related pathology is central to optimizing treatments that may prevent, or delay, cognitive decline. Cerebral perfusion is a tightly regulated physiological property, coupled to tissue metabolism and function, and abnormal (both elevated and reduced) hippocampal perfusion has been reported in a range of cognitive disorders. However, the size and location of the hippocampus complicates perfusion quantification, as many perfusion techniques acquire data with spatial resolution on the order of or beyond the size of the hippocampus, and are thus suboptimal in this region (especially in the presence of hippocampal atrophy and reduced flow scenarios).

A case of hyperthymesia: rethinking the role of the amygdala in autobiographical memory.

Much controversy has been focused on the extent to which the amygdala belongs to the autobiographical memory (AM) core network. Early evidence suggested the amygdala played a vital role in emotional processing, likely helping to encode emotionally charged stimuli. However, recent work has highlighted the amygdala's role in social and self-referential processing, leading to speculation that the amygdala likely supports the encoding and retrieval of AM.

Changes in response bias with different study-test delays: evidence from young adults, older adults, and patients with Alzheimer's disease.

Objective: Along with impaired discrimination, patients with Alzheimer's disease (AD) often show an abnormally liberal response bias (greater tendency to respond "old"). Previously we matched discrimination by varying study-test list length and found that participants' usual bias is maintained, such that patients with AD were more liberal than healthy controls. However, this pattern could be a result of the way in which discrimination was matched.

Gist-based conceptual processing of pictures remains intact in patients with amnestic mild cognitive impairment.

Objective: The picture superiority effect, better memory for pictures compared to words, has been found in young adults, healthy older adults, and, most recently, in patients with Alzheimer's disease and mild cognitive impairment. Although the picture superiority effect is widely found, there is still debate over what drives this effect. One main question is whether it is enhanced perceptual or conceptual information that leads to the advantage for pictures over words.

Using mental imagery to improve memory in patients with Alzheimer disease: trouble generating or remembering the mind's eye?

This study was conducted to understand whether patients with mild Alzheimer disease (AD) could use general or self-referential mental imagery to improve their recognition of visually presented words. Experiment 1 showed that, unlike healthy controls, patients generally did not benefit from either type of imagery. To help determine whether the patients' inability to benefit from mental imagery at encoding was due to poor memory or due to an impairment in mental imagery, participants performed 4 imagery tasks with varying imagery and cognitive demands.

Examining the characteristics of episodic memory using event-related potentials in patients with Alzheimer's disease.

Our laboratory uses event-related EEG potentials (ERPs) to understand and support behavioral investigations of episodic memory in patients with amnestic mild cognitive impairment (aMCI) and Alzheimer's disease (AD). Whereas behavioral data inform us about the patients' performance, ERPs allow us to record discrete changes in brain activity. Further, ERPs can give us insight into the onset, duration, and interaction of independent cognitive processes associated with memory retrieval.