The accuracy and variability of response times (RTs) collected on stock Apple Macintosh computers using USB keyboards was assessed. A photodiode detected a change in the screen's luminosity and triggered a solenoid that pressed a key on the keyboard. The RTs collected in this way were reliable, but could be as much as 100 ms too long. The standard deviation of the measured RTs varied between 2.5 and 10 ms, and the distributions approximated a normal distribution. Surprisingly, two recent Applebranded USB keyboards differed in their accuracy by as much as 20 ms. The most accurate RTs were collected when an external CRT was used to display the stimuli and Psychtoolbox was able to synchronize presentation with the screen refresh. We conclude that RTs collected on stock iMacs can detect a difference as small as 5-10 ms under realistic conditions, and this dictates which types of research should or should not use these systems.

Theta and gamma oscillations are thought to provide signal sets that promote neural coding of cognitive processes. Over 40 yrs ago, Jeffrey Gray reported event-related changes in a narrow band of hippocampal theta (7.5-8.5 Hz) which appeared to involve norepinephrine (NE) release from, the noradrenergic nucleus, the locus coeruleus (LC). These event-related alterations in EEG were elicited by novelty, attentional changes, the use of preparatory signals, and signal-mismatch events. Gray et al. have since provided indirect evidence that supports the role of NE in the modulation of 7.5- to 8.5-Hz oscillations in the hippocampus, but studies investigating the effects of direct LC activation in awake rats have been lacking. In the present study, dentate gyrus EEG was examined during glutamatergic activation of the LC in awake male rats in relation to plasticity effects on simultaneously recorded perforant path-evoked field potentials. Glutamate-injected animals were divided into three groups based on histological and plasticity outcomes; perforant path stimulated controls were also included. The three injected groups were: (1) rats with positive LC placements, demonstrating NE-LTP of the dentate gyrus evoked potential, (2) rats with positive LC placements, without NE-LTP, and (3) Non-LC injected controls. Activation of the LC in awake rats demonstrating NE-LTP increased the relative power of 7- to 9-Hz theta, a result masked in broader 4- to 12-Hz analysis. Comparatively, urethane-anesthetized rats showed an increase in 5-7 Hz, but not 7- to 9-Hz theta with LC activation. Discriminative analysis in the approximate theta band predicted by Gray (7.4-8.5 Hz) revealed that awake rats demonstrating NE-LTP had increased relative power in this narrow frequency compared to rats receiving perforant path only (noninjected) and Non-LC injected rats. Transiently reduced gamma (20-40 Hz) relative power was most commonly observed in rats with verified LC placements failing to express NE-LTP. Given current theories of LC function, these results suggest oscillatory tuning within the theta and gamma range may facilitate shifts in cognitive set.

Based on results from an earlier prototype, custom software and printing techniques were developed to construct a new card-based test of contrast sensitivity (CS) for nonverbal subjects. Compared with the prototype, the new CS card test contains three improvements: (1) larger, more salient test gratings; (2) higher contrast warm-up cards for each spatial frequency set; and (3) smaller contrast step size between adjacent cards. The success of the new cards was evaluated by testing 3.5- and 12-month-old human infants. Results indicated that the new version of the test required little time to complete (mean, 6.5 min) and provided accurate estimates of visual acuity. Also, group contrast sensitivity functions (CSFs) showed substantial development from 3.5 to 12 months of age. Surprisingly, however, group CSFs obtained with the new cards were lower than those obtained with the prototype, a discrepancy that may be due to differences in space average luminance between the two sets of cards. In all, the new CS card procedure possesses several merits that give it potential as an option for assessing spatial vision in infants, toddlers, and subjects with multiple impairments.

4 first series of experiments had demonstrated certain conditions eliciting or inhibiting a "pendulum" phenomenon in the visual perception of apparent movement. The present study consists of five further variations designed to show more clearly conditions of occurrence and non-occurrence of this type of movement.Altering the axis of display to vertical significantly reduces the frequency of pendular-movement perception; Altering the position of metronome from behind to the side of the visual display, gives results almost identical with those where the metronome was inaudible, but, when the metronome is illuminated in this position, all forms of movement perception are reduced, and no pendular movement is reported. The results for all the ten conditions, including the five of the first series are summarized, and the following possible factors are discussed : past experience, physiological nystagmus, and intervening adaptation. All three may be required to account for the perceptual phenomena under investigation and the dichotomizing of explanations into "experiential, " or "physiological," appears to be arbitrary and inconsistent with the complexity of the observed facts. I IKTRODUCTIOS In a previous paper (Hall, Earle and Crookes, 1952), certain conditions for the occurrence or non-occurrence of an arcuate type of apparent movement between two alternating lights were described. With a metronome directly behind the display screen and producing alternating light signals synchronously with the auditory rhythm, the impression of movement of a light along a curved path was very strong. Experimental analysis of some of the conditions facilitating or inhibiting the phenomenon showed it to be complexly determined by, amongst other factors, the circular shape of the lights, their rhythmical presentation, and the warming and cooling of the lamp filaments.In these experiments it had been noticed that, in addition to affecting the path which the movement seemed to take, certain conditions of stimulus presentation seemed to facilitate the perception of any kind of movement. This general effect was, however, not analysed further because it was only secondary to the main effect on the path of movement, but it appears that Werner and Zietz (1928) had shown intersensory effects which are somewhat similar to this. For example, they used a rate of succession of the visual stimuli which was below the accepted optimum for movement perception, and accompanied this by an auditory rhythm composed of clicks at a rate slightly faster than that of the visual stimuli. Some of their subjects reported definite movements in the visual field. Using an irregular series of taps, however, most subjects experienced a '' disintegration " of the visual movement.There are, then, two closely related problems requiring further experimental investigation. First, the main hypothesis arising from our previous experiments was that the path of seen movement must be primarily determined by a complex interaction of visual display conditions, and secondarily b ...