Performance of four seed-caching corvid species in the radial-arm maze analog.

Four seed-caching corvid species were tested in an open-room analog of the radial-arm maze. During Experiment 1, the species more dependent on stored food, Clark's nutcrackers (Nucifraga columbiana) and pinyon jays (Gymnorhinus cyanocephalus), acquired the task more quickly and to higher accuracy levels than either scrub jays (Aphelocoma coerulescens) or Mexican jays (A. ultramarina). During Experiment 2, performance after retention intervals was tested. When intervals of 30–210 min were tested in ascending order, species differences observed during acquisition were again obtained. However, when intervals of 5–300 min were tested in random order, the species differed only at shorter intervals. During Experiment 3, only nutcrackers gave any indication of performing above chance after a 24-hr retention interval. Results support the hypothesis of species differences in spatial information processing that correlate with dependence on stored food. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hippocampus and memory in a food-storing and in a nonstoring bird species.

Food-storing birds maintain in memory a large and constantly changing catalog of the locations of stored food. The hippocampus of food-storing black-capped chickadees (Panus atricapillus) is proportionally larger than that of nonstoring dark-eyed juncos (Junco hyemalis). Chickadees perform better than do juncos in an operant test of spatial non-matching-to-sample (SNMTS), and chickadees are more resistant to interference in this paradigm. Hippocampal lesions attenuate performance in SNMTS and increase interference. In tests of continuous spatial alternation (CSA), juncos perform better than chickadees. CSA performance also declines following hippocampal lesions. By itself, sensitivity of a given task to hippocampal damage does not predict the direction of memory differences between storing and nonstoring species. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Automated study of simultaneous-cue olfactory discrimination learning in adult mice.

Adult C57BL/6J mice were trained in a fully automated operant task to discriminate between 2 simultaneously presented odors for water reward. Each mouse was trained on 16 different discrimination problems to a criterion of 90% correct in a block of 20 trials for each problem. Each of the mice tested reached criterion on all discriminations; the number of errors made before reaching criterion was greatest for the first few problems and decreased substantially thereafter. Acquisition performance on early trials of novel discriminations suggested that mice form learning sets for olfactory cues. The mice were trained on 4 additional problems and tested for memory with probe trials at retention intervals of 1, 2, 4, and 8 weeks. Good retention of olfactory cues was seen even at the longest memory delay. Automated testing of olfactory discriminations should be useful for assessing learning and memory abilities in genetically modified mice. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Divided attention, memory, and spatial discrimination in food-storing and nonstoring birds, black-capped chickadees ( Poecile atricapilla) and dark-eyed Juncos ( Junco hyemalis).

Food-storing birds, black-capped chickadees (Poecile atricapilla), and nonstoring birds, dark-eyed juncos (Junco hyemalis), matched color or location on a touch screen. Both species showed a divided attention effect for color but not for location (Experiment 1). Chickadees performed better on location than on color with retention intervals up to 40 s, but juncos did not (Experiment 2). Increasing sample-distractor distance improved performance similarly in both species. Multidimensional scaling revealed that both use a Euclidean metric of spatial similarity (Experiment 3). When choosing between the location and color of a remembered item, food storers choose location more than do nonstorers. These results explain this effect by differences in memory for location relative to color, not division of attention or spatial discrimination ability. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Acquisition, retention, and extinction of operant discriminations in rats with nucleus basalis magnocellularis lesions.

Effects of bilateral ibotenic acid lesions of nucleus basalis magnocellularis (NBM) and scopolamine treatment on different aspects of learning and memory in an operant discrimination task were assessed. In Experiment 1, NBM lesions impaired acquisition performance. In Experiment 2, scopolamine lowered response rates but did not affect discrimination accuracy in lesioned or control rats. In Experiment 3, although pretrained rats showed transient increases in commission errors, percentage correct responding remained above chance levels after lesion. During extinction in Experiment 4, operant responding diminished more quickly in pretrained NBM-lesioned rats than in controls, but subsequent reacquisition performance was equivalent in both groups. Results suggest the NBM is importantly involved in discrimination learning, but cholinergic activity may be less critical for memory retention than for acquisition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The ontogeny of long-term memory over the first year-and-a-half of life

This research documents the development of long-term memory in human infants from 2 months through the end of the first year-and-a-half of life. In the initial study phase, we trained 6- to 18-month-old human infants in an operant task and tested them after increasing delays until they exhibited no retention for 2 successive weeks. In the second phase, their data were combined with data previously obtained from 2- to 6-month-olds in an equivalent task. The resulting function revealed that the duration of retention increases monotonically between 2 and 18 months of age. This increase was not due to age differences in original learning. This is the first systematic analysis of the course of long-term memory across an extended period of infant development that is based on standardized parameters of training and testing. It provides a reference function against which measures of retention from infants of different ages that are obtained in different memory tasks with different parameters can be meaningfully compared.     

Interference in spatial memory.

Four experiments examined interference in human spatial memory. The first two tested for retroactive interference by varying the similarity between the interpolated task and the task that was learned originally. Retroactive interference was observed during relearning of a radial stylus maze and during relearning of the locations of pairs of playing cards in a concentration game. In the third and fourth experiments, proactive interference was tested during the relearning of the locations of pairs in a concentration game. Some proactive interference was observed when the number of proactive games was varied (Experiment 3), and substantial proactive interference was found when the similarity between the proactive and target tasks was the independent variable (Experiment 4). Although extensive evidence indicates that spatial memory differs from other types of memory, spatial memory is subject to interference effects, as are verbal memory, motor memory, visual discriminative memory in animals, and animal spatial memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hippocampal and amygdaloid involvement in nonspatial and spatial working memory in rats: Effects of delay and interference.

Parametric manipulations of the task demand were used to examine the role of the hippocampus and amygdala in nonspatial and spatial working memory in male rats. Hippocampal lesions produced an immediate and long-lasting impairment of nonspatial working memory in an operant task. The memory deficits increased as the delay interval and the amount of proactive interference increased. Hippocampal lesions severely impaired spatial working memory in spatial alternation. Extensive postoperative testing reduced the magnitude of impairment of nonspatial but not spatial working memory. Amygdaloid lesions did not impair any aspect of performance in 2 tasks. The results suggest that the hippocampus, but not the amygdala, is involved in working memory and the task demand is a critical determinant for observing impairments of nonspatial working memory following hippocampal lesions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

H-7 stimulates desmosome formation and inhibits growth in KB oral carcinoma cells

Groups of old and young rats were administered three tests of spatial learning and memory that are known to be sensitive to hippocampal dysfunction: the radial arm maze (RAM), spatial non-matching-to-sample (SNMTS), and a spatial vs. local cue-preference task. Old rats performed worse than young rats on the RAM and SNMTS tasks; on the cue-preference task, young rats were biased to use spatial cues, whereas old rats exhibited strong preferences for distinct, local cues. Peripheral injections of glucose (100 mg/kg) improved performance by old rats on the RAM and SNMTS, which correlated with measures of glucose metabolism. Glucose treatment did not affect old rats performance on the cue-preference task. There was evidence that glucose-treatment improved performance of young rats in the RAM test, but not the other tests. The results extend the range of tasks on which glucose-induced cognitive enhancement has been demonstrated in aged rats, and provides further evidence that memory loss resulting from hippocampal dysfunction is especially amenable to glucose treatment.     

Matching location and color of a compound stimulus: Comparison of a food-storing and a nonstoring bird species.

Black-capped chickadees (Parus atricapillus), birds that store food, and dark-eyed juncos (Junco hyemalis), nonstoring birds, were compared in 2 operant delayed-matching-to-sample experiments. Subjects were required to remember a stimulus of a different color in a different spatial location on each trial. When spatial and color elements of the sample were placed in conflict on test trials in Experiments 1A and 1B, chickadees' first choices were controlled by the stimulus associated with the spatial location, but juncos' first choices were controlled by the spatial location and the color. In Experiment 2, each element was tested alone after exposure to the compound. Chickadees performed better on the spatial element than the color element, whereas juncos performed equally well on both elements. It is hypothesized that chickadees process spatial information at the expense of color, whereas juncos distribute their attention or memory, or both, more evenly across stimulus dimensions. This difference may be related to the chickadees' reliance on spatial information to find stored food. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Multiple levels of representation of song by European starlings (Sturnus vulgaris): Open-ended categorization of starling sing types and differential forgetting of song categories and exemplars.

Four European starlings (Sturnus vulgari) were trained to discriminate among conspecific and heterospecific song segments in a go/no-go operant task. In Experiment 1, the starlings discriminated among novel starling and heterospecific songs, indicating an open-ended category of conspecific song types. The starlings also showed excellent memory for reinforced conspecific songs and discriminated among subordinate categories of conspecific song. In Experiment 2, the starlings were presented with the song segments from Experiment 1 after an 8-month delay period. The starlings retained the discrimination between conspecific and heterospecific songs but not among conspecific songs. The starlings also retained memory for individual singers over the 8-month delay. Starlings categorize song at the level of species, and at subordinate categories of song types, and may have superior long-term retention of song categories relative to song exemplars. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of response strategy and retention interval on performance of Clark's nutcrackers in a radial maze analogue.

Two groups of Clark's nutcrackers (Nucifraga columbiana) were trained to use either a stay or shift response strategy in a radial maze analog. Each trial had a preretention stage, a retention interval, and a postretention test. In Exp 1, acquisition with a 5-min retention interval was studied. Response strategy did not affect the rate at which the task was learned. Performance following longer retention intervals was tested in Exps 2–4. Changes in retention intervals were presented in trial blocks of increasing duration in Exp 2 and were randomly presented between trials in Exp 3. Exp 4 extended the retention interval to 24 hrs. No difference in performance was found between the 2 groups in any of these experiments. These results suggest a flexible relationship between spatial memory and response requirement in food-hoarding birds for at least 1 spatial memory task. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Rehearsal in spatial working memory

This article reports 3 experiments that tested a hypothesis regarding the nature of rehearsal in spatial working memory, one in which discrete shifts of spatial selective attention mediate the maintenance of location-specific representations. Experiment 1 demonstrated increases in visual processing efficiency for locations held in working memory, which suggested that attention was oriented toward these locations. Experiment 2 eliminated key alternative explanations for Experiment 1 by using an identical stimulus display with a nonspatial memory task, and little or no facilitation of processing at memorized locations was found under these conditions. Finally, Experiment 3 showed that spatial working memory was impaired when participants were hindered in their ability to attend to memorized locations. It is argued that these results implicate selective spatial attention as a rehearsal mechanism for spatial working memory.     

GluR-A-deficient mice display normal acquisition of a hippocampus-dependent spatial reference memory task but are impaired during spatial reversal.

Acquisition and reversal of a spatial discrimination were assessed in an appetitive, elevated plus-maze task in 4 groups of mice: knockout mice lacking the AMPA receptor subunit GluR-A (GluR1), wild-type controls, mice with cytotoxic hippocampal lesions, and controls that had undergone sham surgery. In agreement with previous studies using tasks such as the water maze, GluR-A-/- mice were unimpaired during acquisition of the spatial discrimination task, whereas performance in the hippocampal group remained at chance levels. In contrast to their performance during acquisition, the GluR-A-/- mice displayed a mild deficit during reversal of the spatial discrimination and were profoundly impaired during discrete trial, rewarded-alternation testing on the elevated T maze. The latter result suggests a short-term. flexible spatial working memory impairment in GluR-A-/- mice, which might also underlie their mild deficit during spatial reversal. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Pilocarpine and physostigmine attenuate spatial memory impairments produced by lesions of the nucleus basalis magnocellularis.

Three experiments, with 63 male Long-Evans rats, investigated the effects of bilateral ibotenic acid-induced lesions of the nucleus basalis magnocellularis (NBM) on the acquisition and retention of several spatial memory tasks. Maintenance of spatial memory in a food-search task was impaired following NBM lesions. Acquisition of spontaneous alternation and reinforced alternation in a T-maze, but not the acquisition of a position habit, was also significantly impaired in Ss with these lesions. In several of the tasks, there was evidence of some learning in the lesioned Ss after substantial training, although they were significantly deficient when compared with controls. Intraperitoneal administration of the cholinergic agonists physostigmine sulfate (0.5 mg/kg) or pilocarpine nitrate (3 mg/kg) prior to behavioral testing resulted in a rapid and significant improvement in the performance of the lesioned Ss. Lesions significantly reduced the activity of choline acetyltransferase in the anterior and the posterior neocortex but not the hippocampus. Results indicate that the cholinergic projections originating in the NBM are involved in the learning and memory of spatial tasks. (48 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

What-where-when memory in pigeons.

The authors report a novel approach to testing episodic-like memory for single events. Pigeons were trained in separate sessions to match the identity of a sample on a touch screen, to match its location, and to report on the length of the retention interval. When these 3 tasks were mixed randomly within sessions, birds were more than 80% correct on each task. However, performance on 2 different tests in succession after each sample was not consistent with an integrated memory for sample location, time, and identity. Experiment 2 tested binding of location and identity memories in 2 different ways. The results were again consistent with independent feature memories. Implications for tests of episodic-like memory are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The learning of generalized motor programs: Reducing the relative frequency of knowledge of results enhances memory.

In earlier studies, reducing the relative frequency of knowledge of results (KR) enhanced retention of single movements. In the experiments here we asked whether this variable also enhances memory for classes of actions governed by generalized motor programs. Acquisition conditions involved practicing three versions of a sequential timing task. All three versions had the same temporal structure (or phasing), but the overall durations were different. KR was presented on either 100% or 67% of the trials for two groups. In Experiment 1, reduced relative KR frequency, spread equally across all task versions, enhanced accuracy of the learned relative timing structure as measured on a transfer test with a novel movement duration. Experiment 2 showed that retention of a medium-duration version was more accurate for subjects who never received KR about it in acquisition, as compared with subjects who always did. The data support the view that reduced KR frequency enhances acquisition of the relative-timing structure underlying memory for a class of actions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Rats perform better on spatial than brightness delayed matching-to-sample water-escape due to an unlearned bias to use spatial cues

Rats readily acquire water-escape spatial delayed matching-to-sample (DMTS) tasks and show excellent performance with retention intervals as long as 120 m (17). They also acquire the task more readily with a 5-min retention interval (RI) than with a 1-min RI (16). To determine if these observations are unique to spatial DMTS, or are also true of nonspatial water-escape DMTS, 75-day-old rats were compared on acquisition and subsequent retention of spatial and brightness DMTS. A larger proportion of the rats tested on the spatial problem were able to acquire the task, made fewer acquisition errors, and demonstrated better retention when tested at RIs of 1, 5, 15, 30, 60, and 120 min than did the rats tested on the brightness problem. Acquisition RI did not affect the rate of acquisition on either task. Examination of perserveration errors, the occurrence of intrusions, and position-congruent performance (escape platform in the same physical location on both runs of a trial) revealed that the choices of brightness-trained rats were often more influenced by spatial than brightness cues, suggesting that rats have an unlearned bias to use spatial cues in water-escape DMTS tasks.     

Partial hippocampal kindling affects retention but not acquisition and place but not cue tasks on the radial arm maze

The performance of rats that were partially kindled in the hippocampus was assessed on an 8-arm radial arm maze with 4 baited arms. In rats first trained and then kindled, deficits were found on a place task in which rats reached the goal arms of the maze using salient extramaze spatial cues, but not on an intramaze cue task in which rats reached the goal arms using salient intramaze cues. Acquisition of a new place task on the maze was not different between kindled and control rats. In conclusion, partial hippocampal kindling disrupted the retention but not the acquisition of a spatial or place task; retention of a nonspatial cue task was not disrupted.     

Event-based prospective memory and executive control of working memory

In 5 experiments, the character of concurrent cognitive processing was manipulated during an event-based prospective memory task. High- and low-load conditions that differed only in the difficulty of the concurrent task were tested in each experiment. In Experiments 1 and 2, attention-demanding tasks from the literature on executive control produced decrements in prospective memory. In Experiment 3, attention was divided by different loads of articulatory suppression that did not ultimately lead to decrements in prospective memory. A high-load manipulation of a visuospatial task requiring performance monitoring resulted in worse prospective memory in Experiment 4, whereas in Experiment 5 a visuospatial task with little monitoring did not. Results are discussed in terms of executive functions, such as planning and monitoring, that appear to be critical to successful event-based prospective memory.