A response duration schedule: effects of training, extinction, and deprivation

Rats were trained to hold down a lever for at least 40 consecutive seconds. When the lever had been held down for 40 sec, white noise came on. Releasing the bar in the presence of the noise turned off the noise and operated a feeder that delivered a pellet of food. At the end of training, frequency distributions of response durations peaked at 40 to 41 sec. If as in training, holding down the lever produced white noise at the end of 40 sec, and release of the lever terminated the noise and operated the feeder, but no food delivery occurred, duration distributions and several other measures were initially not very different from when food was delivered. However, if during extinction white noise was never produced by lever holding, and feeder operation did not occur upon lever release, most responses were shorter than 1 sec in duration, some were much longer than 41 sec, and duration distributions did not peak at 40 to 41 sec. When reinforcement was reinstated after extinction, performance quickly returned to pre-extinction measures. Further sessions at different levels of deprivation produced only temporary disruptions in performance.     

Cholinergic modulation of Pavlovian fear conditioning in rats: differential effects of intrahippocampal infusion of mecamylamine and methyllycaconitine

The cholinergic system has consistently been implicated in Pavlovian fear conditioning. Considerable work has been done to localize specific nicotinic receptor subtypes in the hippocampus and determine their functional importance; however, the specific function of many of these subtypes has yet to be determined. An alpha7 nicotinic antagonist methyllycaconitine (MLA) (35 microg), and a broad spectrum non-alpha7 nicotinic antagonist mecamylamine (35 microg) was injected directly into the dorsal hippocampus or overlying cortex either 15 min pre-, 1 min post-, or 6h post-fear conditioning. One week after conditioning, retention of contextual and cue (tone) conditioning were assessed. A significant impairment in retention of contextual fear was observed when mecamylamine was injected 15 min pre- and 1 min post-conditioning. No significant impairment was observed when mecamylamine was injected 6h post-conditioning. Likewise, a significant impairment in retention of contextual fear was observed when MLA was injected 1 min post-conditioning; however, in contrast, MLA did not show any significant impairments when injected 15 min pre-conditioning, but did show a significant impairment when injected 6h post-conditioning. There were no significant impairments observed when either drug was injected into overlying cortex. No significant impairments were observed in cue conditioning for either drug. In general, specific temporal dynamics involved in nicotinic receptor function were found relative to time of receptor dysfunction. The results indicate that the greatest deficits in long-term retention (1 week) of contextual fear are produced by central infusion of MLA minutes to hours post-conditioning or mecamylamine within minutes of conditioning.     

The generalizability of training gains in dementia: effects of an imagery-based mnemonic on face-name retention duration

The generalizability of the results from a case study on the effects of an imagery mnemonic on face-name recall in dementia was examined (Hill, Evankovich, Sheikh, & Yesavage, 1987). Seven patients with Alzheimer's disease (AD) and 1 patient with multi-infarct dementia (MID) were trained by using the method devised by Hill et al. Application of the mnemonic increased the time during which face-name associations could be held in memory for 1 AD patient, and this improvement was maintained in a 1-month follow-up assessment. However, no training gains were observed for the remaining 7 patients, thus questioning the generalizability of this method in enhancing memory in dementia.     

Reversible effects of ambient housing stimulation upon stimulation-seeking in rats

Two types of housing condition, low and high ambient stimulation, were alternated. The effects of this treatment upon rats' subsequent stimulation-seeking behaviour were assessed in a multiple-choice head-input apparatus. The aim of the experiment was to determine whether adult animals would adapt and re-adapt to varying periods of upward and downward shifts in the levels of housing stimulation. A given housing-stimulation had a lawfully cumulative effect which could be completely reversed when housing conditions altered. The most sensitive measures were latency and response rate in the first 5 min of the test. One measure, relative preference for illuminated stimuli over a dark stimulus, gave an indication of the time-lag involved in adaptation to a new housing condition.     

Retrospective revaluation effects following serial compound training and target extinction

Using a conditioned suppression task, two experiments examined retrospective revaluation effects after serial compound training in a release from overshadowing design. In Experiment 1, serial X → A+ training produced suppression to target A, which was enhanced when preceded by feature X, whereas X by itself elicited no suppression. Subsequent A− presentations extinguished responding to A, but had no effect on either responding to X → A or X alone. However, the addition of A− trials did enhance the ability of feature X to elicit suppression to a novel target, B, suggesting retrospective revaluation of X’s properties. Experiment 2 showed that the enhanced transfer effect, observed in Experiment 1, was independent of the training history of the target (B− or Y → B+/B−). Together, these results suggest that feature X did not retrospectively acquire excitatory strength or occasion setting power, but rather a generalized ability to increase responding to any other cue.     

Shrinkage of perceived tonal duration produced by extra sounds: effects of spectral density, temporal position, and transition direction

To investigate the mental mechanism that estimates the duration of sounds, the subjective duration of a tone was measured. In the first experiment a portion of the target sound was replaced with another sound. In the second and third experiments another sound either started or ended in the middle of the target sound. Ten or eleven undergraduates participated as listeners in each of the experiments. In the first experiment, effects of spectral spacing and those of temporal position of the replacing sound were tested. Compared with the intact case, the subjective duration of the replaced target shrunk, and the degree of shrinkage increased as the spectral spacing became wider. The temporal position of the replacing sound did not affect the degree of shrinkage. In the second experiment, effects produced by the start (ON) of the concurrent sound and those by the end (OFF) were compared. The ON case was more effective than the OFF case. In the third experiment, effects of the rise time and fall time of the concurrent sound were tested. A long rise and fall time reduced the difference between the ON and OFF cases. These results are discussed from two viewpoints, one assuming an interaction between the time markers, the other assuming continuous gate control in a neural-counting model for duration.     

Time course of attentional bias to emotional scenes in anxiety: Gaze direction and duration

Pictures of emotionally neutral, positive, and negative (threat- or harm-related) scenes were presented for 3 seconds, paired with nonemotional control pictures. The eye fixations of high and low trait anxiety participants were monitored. Intensity of stimulus emotionality was varied, with two levels of perceptual salience for each picture (colour vs. greyscale). Regardless of perceptual salience, high anxiety was associated with preferential attention: (a) towards all types of emotional stimuli in initial orienting, as revealed by a higher probability of first fixation on the emotional picture than on the neutral picture of a pair; (b) towards positive and harm stimuli in a subsequent stage of early engagement, as shown by longer viewing times during the first 500 ms following onset of the pictures; and with (c) attention away from (i.e., avoidance) harm stimuli in a later phase, as indicated by shorter viewing times and lower frequency of fixation during the last 1000 ms of picture exposure. This suggests that the nature of the attentional bias varies as a function of the time course in the processing of emotional pictures.     

Time course of attentional bias to emotional scenes in anxiety: Gaze direction and duration

Pictures of emotionally neutral, positive, and negative (threat‐ or harm‐related) scenes were presented for 3 seconds, paired with nonemotional control pictures. The eye fixations of high and low trait anxiety participants were monitored. Intensity of stimulus emotionality was varied, with two levels of perceptual salience for each picture (colour vs. greyscale). Regardless of perceptual salience, high anxiety was associated with preferential attention: (a) towards all types of emotional stimuli in initial orienting, as revealed by a higher probability of first fixation on the emotional picture than on the neutral picture of a pair; (b) towards positive and harm stimuli in a subsequent stage of early engagement, as shown by longer viewing times during the first 500 ms following onset of the pictures; and with (c) attention away from (i.e., avoidance) harm stimuli in a later phase, as indicated by shorter viewing times and lower frequency of fixation during the last 1000 ms of picture exposure. This suggests that the nature of the attentional bias varies as a function of the time course in the processing of emotional pictures.     

Infantile stimulation and its effects on frustration- and fear-motivated behavior in rats

Infant rats that were either removed from the nest each day (handled) or left undisturbed (nonhandled) were, in adulthood, given 72 food-reinforced runway acquisition trials followed by 24 trials of extinction training with or without shock. Handled and nonhandled control animals were given runway training without food reinforcement. Reinforced rats ran faster than nonreinforced rats, and handled rats ran faster than nonhandled rats during the initial trials of runway acquisition irrespective of the reinforcement condition. Nonhadled rats stopped running sooner than handled rats when shock was introduced in the goalbox, but differences between handled and nonhandled rats given extinction training without shock were small. Results of a second experiment showed no differences between handled and non-handled rats in the magnitude of the depression effect after an incentive shift. It was concluded that infantile handling had little effect on frustration-motivated behavior, but did affect fear-motivated behavior.     

An enriched environment and 17-beta estradiol produce similar pro-cognitive effects on ovariectomized rats

Estrogen depletion due to aging, surgery or pathological events can cause a multitude of problems, including neurodegenerative alterations. In rodents without ovaries, 17-beta estradiol (E2) has been shown to produce beneficial effects on cognition, stimulating brain regions (e.g., the neocortex, hippocampus and amygdala) related to cognition and learning. Another treatment that stimulates these brain regions is an enriched environment (EE), which is a complex set of external factors in the immediate surroundings that facilitates greater stimulation of sensorial, cognitive and motor circuits of the brain. The aim of the present study was to test, using an animal model of ovariectomy-induced impairment of memory, the relative effect of E2 (with a time-released pellet; 1 μg/rat/day), EE exposure and a combination of both treatments. Experimental and control groups were submitted to two memory tests 18 weeks post-surgery: the autoshaping learning task (ALT) for measuring associative learning and the novel object recognition test (NORT) for evaluating short- and long-term memory. To assess potential motor impairments caused by treatments, all rats were tested after the ALT in an automatic activity counter. Results from ALT show that the ovariectomy blocked the conditioned responses displayed, an effect rescued by chronic treatment with estrogen or EE exposure. The combination of both treatments did not improve the results obtained separately. In the NORT, the exploration time for recognizing a novel object was similar in the short run with all groups, but greater in the long run with hormone administration or EE exposure. As with the ALT, in the NORT there was no improvement shown by the combination treatment. These data were not masked by changes in spontaneous activity because this parameter was not modified in the rats by either treatment. Possible action mechanisms are proposed, taking into account the role of corticosterone and BDNF on cognition.     

Examining effects of training duration on humans' resurgence and variability using a novel touchscreen procedure

Resurgence occurs when a previously reinforced and then extinguished target response increases due to reducing/eliminating an alternative source of reinforcement or punishing an alternative response. We evaluated whether duration of reinforcement history for a target response (1) affects the degree to which resurgence is observed in humans and (2) produces different gradients of response generalization around target responding during extinction testing. We arranged a novel touchscreen interface in which university students could swipe a 3D soccer ball to spin any direction. In Phase 1, the first direction swiped became the target and produced points exchangeable for money for 3 or 1 min across 2 groups. The first swipe was recorded but had no programmed consequence in a third group. In Phase 2, swipes 180-degrees from the target resulted in points for 3 min in all groups. Point deliveries ceased for 2 min to test for resurgence in Phase 3. Target responses resurged during testing to a relatively greater extent with longer Phase-1 training but gradients of response generalization did not differ among groups. These findings extend prior research on the role of training duration on resurgence. We discuss methodological and conceptual issues surrounding the assessment of response generalization in resurgence.     

Capacity, duration, and position effects in visual memory following a successive field procedure

This study considered the efficacy of a Successive Field procedure in revealing properties of iconic memory. 8 subjects were required to identify differences between sequentially presented stimulus and target arrays of letters. While results were broadly in line with previous estimates of the capacity and duration of iconic storage, there was also evidence that identification of target letters depended on their position in the array.     

Specification of direction and duration during programming of discrete sliding movements

Summary Two experiments on duration programming of a discrete sliding movement in choice reactions are reported. In the first experiment it was examined whether duration of movement might be preprogrammed when varied across sessions. The result suggested that programming of movement duration is dependent on direction uncertainty. Experiment 2 used the movement precue technique in an attempt to further examine programming of movement duration and direction. Movement duration, movement direction, movement form and foreperiod duration were manipulated. When duration was not precued, a duration effect was found, while precueing resulted in disappearance of the duration effect, demonstrating that duration of sliding movements can be preprogrammed. Moreover, (pre)programming duration was independent of direction uncertainty, supporting an independent order notion of programming of these response variables. Evidence that motor preparation comprises different processing stages was derived from the additive effects of foreperiod duration and of the movement variables duration and direction.