On obtaining episodic priming in a lexical decision task following paired-associate learning.

In four experiments, subjects made lexical (word-nonword) decisions to target letter strings after studying paired associates. In this lexical decision test, word targets previously studied as response terms in the paired associates were preceded at a 150-ms and/or 950-ms stimulus onset asynchrony (SOA) by one of various subsets of the following six types of primes: (a) a neutral ({xxx} or {ready}) prime, (b) a semantically unrelated word prime episodically related to the target through its having been previously studied in the same pair, (c) a semantically related word prime previously studied in a pair with some other unrelated word, (d) a semantically unrelated word prime previously studied in a pair with some other unrelated word, (e) a nonstudied semantically related word prime, and (f) a nonstudied semantically unrelated word prime. At the 950-ms SOA, facilitation of lexical decisions produced by the episodically related primes was greater in test lists in which there were (a) no 150-ms SOA trials intermixed, (b) no previously studied semantically related primes, and (c) no studied nonword targets. At the 150-ms SOA, facilitation from episodic priming was greater in test lists in which there were (a) no semantically related primes and (b) all studied word targets and no studied nonword targets. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

When target degradation does and does not enhance semantic context effects in word recognition.

Two lexical-decision experiments examined the influence of relatedness proportion (RP, the proportion of word-context–word-target trials sharing a semantic relation) and context-target stimulus onset asynchrony (SOA) on the typically observed interaction between the effects of context and stimulus quality. The standard overadditive interaction of context effects being larger for response times (RTs) to degraded than to nondegraded targets was observed when RP was .50. In contrast, additive effects of context and stimulus quality on RT were observed when RP was .25. These effects were seen at both 200-ms and 800-ms SOAs, even though context effects increased with increasing RP only at the 800-ms SOA. These results (a) undermine the view that expectancy is responsible for producing the standard overadditive Context?×?Stimulus Quality interaction, (b) delineate conditions under which context and stimulus quality have additive and interactive effects on RT, and (c) show that RP has 2 dissociable effects on semantic context effects. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Energy optimal control for time-varying wireless networks

We develop a dynamic control strategy for minimizing energy expenditure in a time-varying wireless network with adaptive transmission rates. The algorithm operates without knowledge of traffic rates or channel statistics, and yields average power that is arbitrarily close to the minimum possible value achieved by an algorithm optimized with complete knowledge of future events. Proximity to this optimal solution is shown to be inversely proportional to network delay. We then present a similar algorithm that solves the related problem of maximizing network throughput subject to peak and average power constraints. The techniques used in this paper are novel and establish a foundation for stochastic network optimization     

Visualization tools for Free Flight air-traffic management

Free Flight lets pilots modify their routes in real time. It requires new conflict detection, resolution, and visualization decision support tools. We describe a testbed for building and evaluating such tools     

On the relation between feeling of knowing and lexical decision: Persistent subthreshold activation or topic familiarity?

Exp 1 replicated I. Yaniv and D. E. Meyer's (1987) finding that lexical decision and episodic recognition performance was better for words previously yielding high-accessibility levels (a combination of feeling-of-knowing and tip-of-the-tongue ratings) in comparison with those yielding low-accessibility levels in a rare word definition task. Exp 2 yielded the same pattern even though lexical decisions preceded accessibility estimates by a full week. Exp 3 dismissed the possibility that the Exp 2 results may have been due to a long-term influence from the lexical decision task to the rare word judgment task. These results support a model in which Ss (1) retrieve topic familiarity information in making accessibility estimates in the rare word definition task and (2) use this information to modulate lexical decision performance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Retrieval blocks in episodic and semantic memory.

A retrieval block (RB) refers to impaired accessibility in retrieving target information when semantically related information is presented or retrieved prior to target retrieval. A research review reveals that RBs occur in a variety of situations, including both episodic and semantic memory tasks. RBs have been most thoroughly studied in the part-list cuing paradigm in episodic recall, but similar principles seem to operate in other situations, including the A–B, A–D interference paradigm, episodic recognition, and the tip-of-the-tongue situation. Evidence for such RBs is problematic for theories postulating automatic spreading activation among associated nodes in memory. Difficulties with theories that account for such RBs are discussed. Further research on RBs may help illuminate similar phenomena, such as the effects of Einstellung in thinking and problem solving. (French abstract) (76 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cochlear compression estimates from measurements of distortion-product otoacoustic emissions

Evidence of the compressive growth of basilar-membrane displacement can be seen in distortion-product otoacoustic emission (DPOAE) levels measured as a function of stimulus level. When the levels of the two stimulus tones (f1 and f2) are related by the formula L1 = 39 dB + 0.4 x L2 [Kummer et al., J. Acoust. Soc. Am. 103, 3431-3444 (1998)] the shape of the function relating DPOAE level to L2 is similar (up to an L2 of 70 dB SPL) to the classic Fletcher and Munson [J. Acoust. Soc. Am. 9, 1-10 (1933)] loudness function when plotted on a logarithmic scale. Explicit estimates of compression have been derived based on recent DPOAE measurements from the laboratory. If DPOAE growth rate is defined as the slope of the DPOAE I/O function (in dB/dB), then a cogent definition of compression is the reciprocal of the growth rate. In humans with normal hearing, compression varies from about 1 at threshold to about 4 at 70 dB SPL. With hearing loss, compression is still about 1 at threshold, but grows more slowly above threshold. Median DPOAE I/O data from ears with normal hearing, mild loss, and moderate loss are each well fit by log functions. When the I/O function is logarithmic, then the corresponding compression is a linear function of stimulus level. Evidence of cochlear compression also exists in DPOAE suppression tuning curves, which indicate the level of a third stimulus tone (f3) that reduces DPOAE level by 3 dB. All three stimulus tones generate compressive growth within the cochlea; however, only the relative compression (RC) of the primary and suppressor responses is observable in DPOAE suppression data. An RC value of 1 indicates that the cochlear responses to the primary and suppressor components grow at the same rate. In normal ears, RC rises to 4, when f3 is an octave below f2. The similarities between DPOAE and loudness compression estimates suggest the possibility of predicting loudness growth from DPOAEs; however, intersubject variability makes such predictions difficult at this time.     

Role of potassium channels in amyloid-induced cell death

Basal forebrain cholinergic neurons are severely depleted early in Alzheimer's disease and appear particularly susceptible to amyloid beta-peptide (A beta) toxicity in vivo. To model this effect in vitro, a cholinergic septal cell line (SN56) was exposed to A beta. SN56 cells exhibited a tetraethylammonium (TEA)-sensitive outward K+ current with delayed rectifier characteristics. Increases of 64% (+/-19; p < 0.02) and 44% (+/-12; p < 0.02) in K+ current density were noted 6-12 and 12-18 h following the addition of A beta to SN56 cell cultures, respectively. Morphological observation and staining for cell viability showed that 25 +/- 4 and 39 +/- 4% of SN56 cells were dead after 48- and 96-h exposures to A beta, respectively. Perfusion of SN56 cells with 10-20 mM TEA blocked 71 +/- 6 to 92 +/- 2% of the outward currents, widened action potentials, elevated [Ca2+]i, and inhibited 89 +/- 14 and 68 +/- 14% of the A beta toxicity. High [K+]o, which depolarizes cell membranes and increases [Ca2+]i, also protected SN56 cells from A beta toxicity. This effect appeared specific since glucose deprivation of SN56 cells did not alter K+ current density and TEA did not protect these cells from hypoglycemic cell death. Furthermore, A beta was toxic to a dopaminergic cell line (MES23.5) that expressed a K+ current with delayed rectifier characteristics; K+ current density was not altered by A beta and MES23.5 cells were not protected by TEA from A beta toxicity. In contrast, a noncholinergic septal cell line (SN48) that shows minimal outward K+ currents was resistant to the toxicity of A beta. These data suggest that a K+ channel with delayed rectifier characteristics may play an important role in A beta-mediated toxicity for septal cholinergic cells.