Effects of pyridoxine on dreaming: a preliminary study

The effect of pyridoxine (Vitamin B-6) on dreaming was investigated in a placebo, double-blind study to examine various claims that Vitamin B-6 increases dream vividness or the ability to recall dreams. 12 college students participated in all three treatment conditions, each of which involved ingesting either 100 mg B-6, 250 mg B-6, or a placebo prior to bedtime for a period of five consecutive days. The treatment conditions were completely counterbalanced and a two-day wash-out period occurred between the three five-day treatment blocks. Morning self-reports indicated a significant difference in dream-salience scores (this is a composite score containing measures on vividness, bizarreness, emotionality, and color) between the 250-mg condition and placebo over the first three days of each treatment. The data for dream salience suggests that Vitamin B-6 may act by increasing cortical arousal during periods of rapid eve movement (REM) sleep. An hypothesis is presented involving the role of B-6 in the conversion of tryptophan to serotonin. However, this first study needs to be replicated using the same procedures and also demonstrated in a sleep laboratory before the results can be considered certain.     

Semantic priming: on the role of awareness in visual word recognition in the absence of an expectancy

By hypothesis, awareness is involved in the modulation of feedback from semantics to the lexical level in the visual word recognition system. When subjects are aware of the fact that there are many related prime-target pairs in a semantic priming experiment, this knowledge is used to configure the system to feed activation back from semantics to the lexical level so as to facilitate processing. When subjects are unaware of this fact, the default set is maintained in which activation is not fed back from semantics to the lexical level so as to conserve limited resources. Qualitative differences in the pattern of data from two lexical decision experiments that employ masked priming are consistent with this hypothesis. Semantic context and stimulus quality interact when the prime is processed with awareness whereas these same two factors produce additive effects on RT when the prime is unlikely to have been processed with awareness. These experiments thus illustrate one way in which awareness (or lack thereof) affects the dynamics of visual word recognition.     

Divided attention, aging, and priming in exemplar generation and category verification

Transfer-appropriate processing theories differentiate between conceptual- and perceptual-priming tasks. The former are said to be influenced by the nature of processing engaged in at study, but not by changes in modality between study and test; the latter are sensitive to changes in format between study and test, but not to variations in the extent of semantic processing at study. In the present experiments, we examined the effects of divided attention and aging on priming in exemplar generation and category verification, two tasks that require access to semantic information at test. Manipulations of attention during encoding affected the extent of priming in exemplar generation, but not in category verification. Priming effects were similar in young and older adults in exemplar generation following study in both full and divided attention. Although older adults did not demonstrate priming in category verification in one experiment, no effects of age or divided attention were observed in a second experiment. In addition, priming in category verification was unaffected by varying the level of processing at encoding. However, the absence of levels-of-processing and attention effects in category verification does not signal that priming in this task has a perceptual basis; priming in category verification was insensitive to modality shifts between study and test. The implications of these findings for theories of priming and cognitive aging are considered.     

Identification of the eye-brain-hand system with point processes: a new approach to simple reaction time

By presenting a Poisson process of flashes to observers who hit a button as quickly as possible after each, the authors identified the system involved in simple reaction time (RT). The nonlinear kernels up to 2nd order were measured from the stimulus and response point processes. The 1st-order kernel is analogous to a histogram of simple RTs. The 2nd-order kernel shows complex patterns of nonlinear suppression and facilitation between pairs of flashes. Simple RT measured as the lag of the 1st-order kernel's peak agrees with RT from conventional discrete trial experiments. RTs are shorter and less variable when the flashes are separated by uniform rather than exponential delays, which shows that observers use the stimulus hazard function to become prepared to detect and respond to the flash.     

Sensitivity and specificity of reliable digit span in malingered pain-related disability

The reliable digit span (RDS) performance of chronic pain patients with unambiguous spinal injuries and no evidence of exaggeration or response bias (n = 53) was compared to that of chronic pain patients meeting criteria for definite malingered neurocognitive dysfunction (n = 35), and a group of nonmalingering moderate-severe traumatic brain injury (TBI) patients (n = 69). The results demonstrated that scores of 7 or lower were associated with high specificity (> .90) and sensitivity (up to .60) even when moderate to severe TBI are included. Multiple studies have demonstrated that RDS scores of 7 or lower rarely occur in TBI and pain patients who are not intentionally performing poorly on cognitive testing. This study supports the use of the RDS in detecting response bias in neuropsychological patients complaining of pain as well as in the assessment of pain-related cognitive impairment in patients whose primary complaint is pain.     

In sight but out of mind: do competing views test the limits of perception without awareness?

Over a century's worth of research suggests that "perception" without awareness is a genuine phenomenon. However, relatively little research has explored the question of whether all visually presented information activates representations in long term memory without awareness. Two experiments explored the use of a figure-ground display consisting of competing views in which one view dominates the other such that subjects are (initially) unaware of the non-dominant view. Neither experiment provided evidence that the non-dominant view (an embedded word) activated its representation in long term memory when the subject failed to report being aware of the embedded word in that priming was not seen on a subsequent stem completion task. In contrast, priming was seen when subjects reported being aware of the embedded word. It is suggested that two competing figure-ground relations are not concurrently computed unconsciously.