Intrusions in episodic recall: age differences in editing of overt responses

Two experiments compared episodic word-list recall of young and older adults. In Experiment 1, using standard free-recall procedures, older adults recalled significantly fewer correct items and made significantly more intrusions (recall of items that had not appeared on the target list) than younger adults. In Experiment 2, we introduced a new method, called externalized free recall, in which participants were asked to recall any items that came to mind during the recall period but to indicate with an immediate key press those items they could identify as intrusions. Both age groups generated a large number of intrusions, but older adults were significantly less likely than young adults to identify these as nonlist items. Results suggest that an editing deficit may be a contributor to age differences in episodic recall and that externalized free recall may be a useful tool for testing computationally explicit models of episodic recall.     

Epidemiologic studies of multiple sclerosis: a review.

There is evidence for genetic factors in multiple sclerosis (MS). The evidence come from epidemiologic studies, racial predilection, risk in family members (sibs, half sibs, adoptees) and twins studies. MS is not a Mendelian inherited disease; only the susceptibility to the disease is inherited, the risk of MS being also related to an environmental factor. Many candidate genes were screened, and there are four research groups trying to study the whole genome. MS seem to be an oligo- or multigenic disorder with an apparently similar phenotype for the different genes involved.     

Techniques and devices to restore cognition

Executive planning, the ability to direct and sustain attention, language and several types of memory may be compromised by conditions such as stroke, traumatic brain injury, cancer, autism, cerebral palsy and Alzheimer's disease. No medical devices are currently available to help restore these cognitive functions. Recent findings about the neurophysiology of these conditions in humans coupled with progress in engineering devices to treat refractory neurological conditions imply that the time has arrived to consider the design and evaluation of a new class of devices. Like their neuromotor counterparts, neurocognitive prostheses might sense or modulate neural function in a non-invasive manner or by means of implanted electrodes. In order to paint a vision for future device development, it is essential to first review what can be achieved using behavioral and external modulatory techniques. While non-invasive approaches might strengthen a patient's remaining intact cognitive abilities, neurocognitive prosthetics comprised of direct brain-computer interfaces could in theory physically reconstitute and augment the substrate of cognition itself.     

Comparison of spectral analysis methods for characterizing brain oscillations

Spectral analysis methods are now routinely used in electrophysiological studies of human and animal cognition. Although a wide variety of spectral methods has been used, the ways in which these methods differ are not generally understood. Here we use simulation methods to characterize the similarities and differences between three spectral analysis methods: wavelets, multitapers and P(episode). P(episode) is a novel method that quantifies the fraction of time that oscillations exceed amplitude and duration thresholds. We show that wavelets and P(episode) used side-by-side helps to disentangle length and amplitude of a signal. P(episode) is especially sensitive to fluctuations around its thresholds, puts frequencies on a more equal footing, and is sensitive to long but low-amplitude signals. In contrast, multitaper methods are less sensitive to weak signals, but are very frequency-specific. If frequency specificity is not essential, then wavelets and P(episode) are recommended.     

EEG oscillations and recognition memory: theta correlates of memory retrieval and decision making

Studies of memory retrieval have identified electroencephalographic (EEG) correlates of a test item's old-new status, reaction time, and memory load. In the current study, we used a multivariate analysis to disentangle the effects of these correlated variables. During retrieval, power of left-parietal theta (4-8 Hz) oscillations increased in proportion to how well a test item was remembered, and theta in central regions correlated with decision making. We also studied how these oscillatory dynamics complemented event-related potentials. These findings are the first to demonstrate that distinct patterns of theta oscillations can simultaneously relate to different aspects of behavior.     

Overexpression of antizyme-inhibitor in NIH3T3 fibroblasts provides growth advantage through neutralization of antizyme functions

Antizyme inhibitor (AzI) is a homolog of ornithine decarboxylase (ODC), a key enzyme of polyamine synthesis. Antizyme inhibitor retains no enzymatic activity, but exhibits high affinity to antizyme (Az), a negative regulator of polyamine homeostasis. As polyamines are involved in maintaining cellular proliferation, and since AzI may negate Az functions, we have investigated the role of AzI in regulating cell growth. We show here that overexpression of AzI in NIH3T3 cells increased growth rate, enabled growth in low serum, and permitted anchorage-independent growth in soft agar, while reduction of AzI levels by AzI siRNA reduced cellular proliferation. Moreover, AzI overproducing cells gave rise to tumors when injected into nude mice. AzI overexpression resulted in elevation of ODC activity and of polyamine uptake. These effects of AzI are a result of its ability to neutralize Az, as overexpression of an AzI mutant with reduced Az binding failed to alter cellular polyamine metabolism and growth properties. We also demonstrate upregulation of AzI in Ras transformed cells, suggesting its relevance to some naturally occurring transformations. Finally, increased uptake activity rendered AzI overproducing and Ras-transformed cells more sensitive to toxic polyamine analogs. Our results therefore imply that AzI has a central and meaningful role in modulation of polyamine homeostasis, and in regulating cellular proliferation and transformation properties.     

Ophthalmology on the internet: what do our patients find?

The Internet has become a favorite source of medical information for a growing number of patients. At the same time, content on the Internet represents an amalgamation of viewpoints, commercial interests, and various biases. A common way to access Internet information is through commercial portals with proprietary search engines. Often these search engines prioritize their rank list based on commercial interests. We evaluated whether Internet searches of ophthalmic issues are slanted toward commercial sites and whether any differences exist among the various search engines. We used age-related macular degeneration as an example. In this study, we found that some search engines are heavily tilted toward commercial partnerships, whereas others emphasize sites run by nonprofit and educational organizations. Our findings may guide physicians in recommending to their patients some internet portals rather than others. This type of evaluation can be conducted intermittently by physicians and other health care professionals to assess the type of information that reaches their patients and what biases may be influencing patient knowledge and decision making.