Differential effects of methamphetamine and haloperidol on the control of an internal clock.

Humans and animals process temporal information as if they were using an internal stopwatch that can be stopped and reset, and whose speed is adjustable. Previous data suggest that dopaminergic drugs affect the speed of this internal stopwatch. Using a paradigm in which rats have to filter out the gaps that (sometimes) interrupted timing, the authors found that methamphetamine and haloperidol also affect the stop and reset mechanism of the internal clock, possibly by modulating attentional components that are dependent on the content and salience of the timed events. This is the fist report of both clock and attentional effects of dopaminergic drugs on interval timing in the same experimental setting. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Temporal integration as a function of signal and gap intensity in rats (Rattus norvegicus) and pigeons (Columba livia).

Previous data suggest that rats (Rattus norvegicus) and pigeons (Columba livia) use different interval-timing strategies when a gap interrupts a to-be-timed signal: Rats stop timing during the gap, and pigeons reset their timing mechanism after the gap. To examine whether the response rule is controlled by an attentional mechanism dependent on the characteristics of the stimuli, the authors manipulated the intensity of the signal and gap when rats and pigeons timed in the gap procedure. Results suggest that both rats and pigeons stop timing during a nonsalient gap and reset timing after a salient gap. These results also suggest that both species use similar interval-timing mechanisms, influenced by nontemporal characteristics of the signal and gap. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Simultaneous temporal processing.

Seven studies assessed the ability of 36 male albino Norway rats to process temporal information from 2 internal clocks simultaneously and independently. In the 1st 6 experiments, a light stimulus signaled an overall interval (OI) between the beginning of a trial and the availability of food reinforcement; a sound stimulus was used to signal shorter intervals that divided the OIs into equal segments. When there was a fixed temporal relation between the final segment signal and the availability of reinforcement, there was a double-scallop pattern of responding throughout the segmented OI; the function relating response rate (FRRR) to time during the segment intervals was similar to the FRRR to time in unsegmented OIs; a change in response rate occurred at the time that a normally presented segment signal was omitted. Results show that Ss timed the OI and the segment intervals simultaneously and independently without interference. In Exp VII, a light stimulus was used on some trials and a sound stimulus was used on others to signal a discrete-trial 50-sec peak procedure. When these 2 signals were presented in compound, there was a leftward shift of the response function that suggested that Ss timed both signals simultaneously. (81 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Abstraction of temporal attributes.

Four experiments demonstrated cross-modal transfer (CMT) of classification rules for temporal intervals. In Exp I, 20 male albino Norway rats learned a temporal discrimination between a 2- and an 8-sec signal in one modality (vision or audition). Results show positive transfer to a temporal discrimination between a 2- and an 8-sec signal in the other modality when the response rule was maintained, and negative transfer when the response rule was reversed. Exp II with 20 Ss demonstrated positive CMT in a temporal generalization procedure. Exp III demonstrated CMT of both duration and temporal location in a procedure in which 20 Ss were exposed to 3 successive signal durations. Exp IV demonstrated CMT of both duration and temporal order in a procedure in which 5 Ss were exposed to simultaneously presented signal durations, one auditory and one visual. It is concluded that rats can abstract temporal attributes from modality-specific aspects of a signal. (38 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A mode control model of counting and timing processes.

In Exp I, 10 male albino Norway rats initially learned a discrimination between a 2-cycle auditory signal of 2-sec duration and an 8-cycle auditory signal of 8-sec duration. In a number discrimination test, the number of cycles was varied, and the signal duration was held constant at an intermediate value. In a duration discrimination test, the signal duration was varied, and the number of cycles was held constant at an intermediate value. Ss were equally sensitive to a 4:1 ratio of counts (with duration controlled) and a 4:1 ratio of times (with number controlled). The point of subjective equality for the psychophysical functions that related response classification to signal value was near the geometric mean of the extreme values for both number and duration discriminations. Exp II demonstrated that methamphetamine (1.5 mg/kg, ip) shifted the psychophysical functions for both number and duration leftward by approximately 10%. Exp III demonstrated that the magnitude of cross-modal transfer from auditory to cutaneous signals was similar for number and duration. In Exp IV (6 Ss), the mapping of number onto duration demonstrated that a count was approximately equal to 200 msec. The psychophysical functions for number and duration were fit with a scalar expectancy model with the same parameter values for each attribute. It is concluded that the same internal mechanism is used for counting and timing. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

<Emphasis Type="Italic">In-Situ</Emphasis> Electrochemical Investigations of a Nickel-Based Alloy Subjected to Fatigue

The HASTELLOY C2000 superalloy is a commercially designed superalloy manufactured to function in reducing and oxidizing corrosive solutions. The industrial applications have tremendous potential in automotive, structural, aviation, and storage components. Although C2000 demonstrates good reducing and oxidizing traits in extremely aggressive media (which are attractive features of its chemistry), changes in the mechanical properties are believed to be insignificant due to its strong propensity to passivate under corrosive conditions. The ductility behavior and corrosion properties of C2000 are superior to those of stainless steels. The objective of the present study is to examine the corrosion-fatigue behavior of C2000 in a 3.5 wt pct sodium-chloride (NaCl) solution. C2000 submerged in 3.5 wt pct NaCl at room temperature is not susceptible to localized corrosion, such as pitting, during fatigue. At an accelerated potential of 350 mV, the current responses show an increase in the current due to slip steps emerging to the surface as a result of fatigue. The crack-initiation site and the examination of the fracture morphology are discussed. This article is based on a presentation given in the symposium entitled “Deformation and Fracture from Nano to Macro: A Symposium Honoring W.W. Gerberich’s 70th Birthday,” which occurred during the TMS Annual Meeting, March 12–16, 2006 in San Antonio, Texas and was sponsored by the Mechanical Behavior of Materials and Nanomechanical Behavior Committees of TMS.

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Differential effects of auditory and visual signals on clock speed and temporal memory.

The effects of signal modality on duration classification in college students were studied with the duration bisection task. When auditory and visual signals were presented in the same test session and shared common anchor durations, visual signals were classified as shorter than equivalent duration auditory signals. This occurred when auditory and visual signals were presented sequentially in the same test session and when presented simultaneously but asynchronously. Presentation of a single modality signal within a test session, or both modalities but with different anchor durations did not result in classification differences. The authors posit a model in which auditory and visual signals drive an internal clock at different rates. The clock rate difference is due to an attentional effect on the mode switch and is revealed only when the memories for the short and long anchor durations consist of a mix of contributions from accumulations generated by both the fast auditory and slower visual clock rates. When this occurs auditory signals seem longer than visual signals relative to the composite memory representation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hippocampus, time, and memory.

Five experiments determined the effects of hippocampal damage on timing and the memory for temporal events. Norway rats (N?=?20) were trained to discriminate between auditory signals that differed in both duration (2 or 8 sec) and rate (2 or 16 cycles/sec). After Ss acquired the discrimination, signals with intermediate durations and rates were presented. Ss then received either fimbria-fornix lesions or control operations. Postoperatively, the accuracy of duration and rate discriminations as measured by the difference limen (DL) was unaffected by the lesion, but the point of subjective equality was shifted to a shorter duration and a slower rate by the lesion. Both Ss with lesions and Ss with control operations showed cross-modal transfer of duration and rate from the auditory signals used in training to visual signals. When a 5-sec delay was imposed between the end of a signal and the opportunity to respond, lesioned Ss were selectively impaired by the addition of the delay as measured by an increase in the DL. When a peak procedure was employed, the maximum response rate of controls was approximately at the time of scheduled reinforcement (20 sec), but the maximum response rate of lesioned Ss was earlier than the time of reinforcement. When a 5-sec gap was imposed in the signal, controls summed the signal durations before and after the gap, whereas lesioned Ss showed no retention of the signal duration prior to the gap. Lesions impaired spatial working memory in an 8-arm radial maze. (51 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Temporal integration in duration and number discrimination.

Investigated temporal integration in duration and number discrimination among 6 male albino rats through the use of a psychophysical choice procedure. A response on 1 lever ("short" response) following a 1-sec white-noise signal (WNS) was followed by food reinforcement, and a response on the other level ("long" response) following a 2-sec WNS was also followed by food reinforcement. Either response following a signal of 1 of 5 intermediate durations was unreinforced. This led to a psychophysical function in which the probability of a long response was related to signal duration in an ogival manner. On 2 test days, a WNS with 5, 6, 7, 8, or 10 segments of either 0.5-sec on and 0.5-sec off or 1-sec on and 1-sec off was presented, and a choice response following these signals was unreinforced. The probability of a long response was the same function of a segmented signal and a continuous signal if each segment was considered equivalent to 200 msec. A quantitative fit of scalar estimation theory suggested that the latencies to initiate temporal integration and to terminate the process are both about 200 msec and that the same internal accumulation process can be used for counting and timing. (16 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A Review of “Climbing Mount Laurel: The Struggle for Affordable Housing and Social Mobility in an American Suburb”

In this article we evaluate Rhode Island voters' rejection of the Greenhouse Compact, a $750 million, seven-year, comprehensive economic development plan designed to create 60,000 new jobs and increase wages statewide. After describing the proposal and examining criticisms of it, we argue that the defeat of the Greenhouse Compact was a consequence of its procedures as much as of its content. Voters rejected the distribution of costs and benefits under the plan and its elitist, exclusionary characteristics. We conclude with suggestions for planners, based on the principle that economic development planning or industrial policymaking must be as concerned about how a program is designed, publicized, and implemented as about the substance of the plan itself.