Primed word-fragment completion and successive memory test performance in normal aging

Young and old subjects were investigated to examine whether: the effects of priming are influenced by aging; there is independence between primed word-fragment completion and recognition performances; and the dependence between different tests is influenced by aging. A successive test paradigm was employed involving repeated assessment of to-be-remembered words by means of recognition and primed word-fragment completion. The results show that implicit memory declines with increasing age, and that correlations between different memory tests decrease with age. The outcome suggests that age-related memory decline involves several forms of memory, including primed word-fragment completion, and is reflected in correlations between measures of implicit and explicit memory.     

Evidence for the substantia nigra pars compacta as an essential component of a memory system independent of the hippocampal memory system

The aim of the present study was to test if the nigrostriatal pathway is an essential component for a water maze cued task learning and if it works independently of the hippocampal memory system. This hypothesis was tested using an animal model of Parkinson's disease in which male Wistar rats were lesioned in the substantia nigra pars compacta (SNc) by the intranigral infusion of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), thus causing a partial depletion of striatal dopamine. SNc-lesioned and sham-operated animals were implanted bilaterally with guide cannulae above the dorsal hippocampus in order to be tested after the administration of 0.4 microl 2% lidocaine or saline into this structure. The animals were tested in a spatial or in a cued version of the water maze, memory tasks previously reported to model hippocampal-dependent spatial/relational and striatal-dependent S-R learning, respectively. Hippocampal inactivation, but not SNc lesion, impaired learning and memory in the spatial version of the water maze. An opposite situation was observed with the cued version. No significant interaction was observed between the SNc lesion and hippocampal inactivation conditions affecting scores in the spatial or in the cued version of the water maze. These results suggest that the nigrostriatal pathway is an essential part of the memory system that processes S-R learning and that it works independently of the hippocampal memory system that processes spatial/relational memories.     

Septal infusions of glucose or pyruvate,but not fructose,produce avoidance deficits when co-infused with the GABA agonist muscimol

Although glucose typically enhances memory or reverses memory deficits, glucose can also produce memory deficits when co-infused with the gamma-aminobutyric acid (GABA) agonist muscimol into the medial septum (Parent & Gold, 1997; Parent, Laurey, Wilkniss, & Gold, 1997). To date the mechanisms underlying the memory-impairing interaction between GABA and glucose remain unknown. Here we investigate whether this effect is the result of hyperosmolar conditions or may involve glucose metabolism. Male Sprague-Dawley rats were given one-trial inhibitory avoidance training after receiving septal infusions of vehicle (phosphate-buffered saline, 0.5 microl), the GABA(A) agonist muscimol (3 nmol), glucose (16.5, 33, or 66 nmol), fructose (33 nmol), pyruvate (33 nmol), or a solution containing muscimol combined with glucose, fructose, or pyruvate. Retention performance was tested 48 h later. Infusions of glucose, pyruvate, fructose, or muscimol alone did not affect retention performance. However, co-infusions of all doses of glucose (16.5, 33, or 66 nmol) or the glycolytic end product pyruvate with muscimol impaired retention performance. Co-infusions of fructose with muscimol did not affect retention performance. These results suggest that the memory-impairing interaction between glucose and muscimol does not result from hyperosmolar conditions, because equiosmolar concentrations of fructose do not mimic the effects of glucose and the memory deficits do not vary as a function of glucose concentration. The finding that pyruvate mimicked the effects of glucose and impaired memory when combined with muscimol suggests that glucose metabolism may be involved in the memory-impairing interaction between glucose and GABA(A) receptors in the medial septum.     

Acetylcholine actions in the dorsomedial striatum support the flexible shifting of response patterns

There is accumulating evidence that the dorsomedial striatum plays a significant role in the learning of a new response pattern and the inhibiting of old response patterns when conditions demand a shift in strategies. This paper proposes that activity of cholinergic neurons in the dorsomedial striatum is critical for enabling behavioral flexibility when there is a change in task contingencies. Recent experimental findings are provided supporting this idea. Measuring acetylcholine efflux from the dorsomedial striatum during the acquisition and reversal learning of a spatial discrimination shows that acetylcholine efflux selectively increases during reversal learning as a rat begins to learn a newly reinforced spatial location, but returns to near basal levels when a rat reliably executes the new choice pattern. Experimental findings are also described indicating that the blockade of muscarinic cholinergic receptors in the dorsomedial striatum does not impair acquisition of an egocentric response discrimination, but impairs reversal learning of an egocentric response discrimination. Based on these results, increased cholinergic activity at muscarinic receptors is part of a neurochemical process in the dorsomedial striatum that allows inhibition of a previously relevant response pattern while learning a new response pattern. In situations that demand behavioral flexibility, muscarinic cholinergic activity in the dorsomedial striatum may directly influence corticostriatal plasticity to produce changes in response patterns.     

Judgments of remembering: the revelation effect in children and adults

When items on a recognition test are presented as a series of increasingly complete fragments rather than being presented initially in their fully intact form, adults' judgments of recognition exhibit an increased tendency to judge items as "old," an illusion of recognition referred to as the revelation effect. The present study used pictorial stimuli to test for a revelation effect with 4-year-olds, 8-year-olds, and adults (N = 76). A reliable revelation effect was found at all ages tested, indicating that the complex fluency-of-processing discrepancy detection and attribution mechanisms thought to be responsible for the effect function similarly across an age range from 4-years-of-age through adulthood. It was also found that the recognition decisions of the 8-year-olds and the adults were affected by how quickly they were able to identify a picture during the revelation phase of the recognition test. This effect was not found with the 4-year-olds, suggesting an age difference in the awareness and strategic use of an implicit memory effect when making explicit judgments of recognition.     

Time and resource limits on working memory: cross-age consistency in counting span performance

This longitudinal study separated resource demand effects from those of retention interval in a counting span task among 100 children tested in grade 2 and again in grades 3 and 4. A last card large counting span condition had an equivalent memory load to a last card small, but the last card large required holding the count over a longer retention interval. In all three waves of assessment, the last card large condition was found to be less accurate than the last card small. A model predicting reading comprehension showed that age was a significant predictor when entered first accounting for 26% of the variance, but counting span accounted for a further 22% of the variance. Span at Wave 1 accounted for significant unique variance at Wave 2 and at Wave 3. Results were similar for math calculation with age accounting for 31% of the variance and counting span accounting for a further 34% of the variance. Span at Wave 1 explained unique variance in math at Wave 2 and at Wave 3.     

Posttraining Electrical Stimulation of Vagal Afferents with Concomitant Vagal Efferent Inactivation Enhances Memory Storage Processes in the Rat

Peripherally administered or released substances that modulate memory storage, but do not freely enter the brain, may produce their effects on memory by activating peripheral receptors that send messages centrally through the vagus nerve. Indeed, vagus nerve stimulation enhances memory performance, although it is unclear whether this effect is due to the activation of vagal afferents or efferents. To eliminate the possible influence of descending fibers on memory storage processes, rats were implanted with cuff electrode/catheter systems along the left cervical vagus. Forty-eight hours following surgery, each animal received a 3.0-μl infusion (1.0 μl/min) of either lidocaine hydrochloride (75.0 mM) or isotonic saline below the point of stimulation. Animals were then trained 10 min later on an inhibitory-avoidance task with a 0.75-mA, 1.0-s foot shock. Sham stimulation or vagus nerve stimulation (0.5-ms biphasic pulses; 20.0 Hz; 30 s; 0.2, 0.4, or 0.8 mA) was administered immediately after training. Memory, tested 24 h later, was enhanced by stimulation whether descending vagus nerve fibers were inactivated or not. Both lidocaine- and saline-infused groups showed an intensity-dependent, inverted-U-shaped pattern of retention performance, with the greatest effect observed for 0.4 mA (U= 9,p< .05, andU= 7,p< .01, respectively). Additionally, animals that received lidocaine infusions, but no vagus nerve stimulation, showed impaired memory compared to the performance of saline-infused control animals (U= 11,p< .05). Together, these findings suggest that vagal afferents carry messages about peripheral states that lead to the modulation of memory storage and that the memory-enhancing effect produced by vagus nerve stimulation is not mediated via the activation of vagal efferents.     

瑞文作业的年龄差异及其与“位置法”记忆训练的关系

该工作采用华东师大心理学系修订的瑞文测验联合型（ＣＲＴ—ＡＣ）,对经过“位置法”记忆训练的青年人、老年人及在年龄、性别、文化和智力水平等方面均相匹配的青年、老年对照进行测验,比较观察力和推理能力的年龄差异,探讨“位置法”记忆训练对这种能力的间接迁移作用。结果表明：１．青年组瑞文作业成绩明显高于老年组;２．当作业难度加大或限定时间时测验,更扩大了年龄差异;３．青年训练组瑞文作业成绩明显高于其对照组,而在老年训练组与其对照组之间则未见差异。     

Memory Versus Expectation: Processing Relative Clauses in a Flexible Word Order Language

Memory limitations and probabilistic expectations are two key factors that have been posited to play a role in the incremental processing of natural language. Relative clauses (RCs) have long served as a key proving ground for such theories of language processing. Across three self-paced reading experiments, we test the online comprehension of Hungarian subject- and object-extracted RCs (SRCs and ORCs, respectively). We capitalize on the syntactic properties of Hungarian that allow for a variety of word orders within RCs, which helps us to delineate the processing costs associated with memory demand and violated expectations. Results showed a processing cost at the RC verb for structures that have longer verb-argument distances, despite those structures being more frequent in the corpus. These findings thus support theories that attribute processing difficulty to memory limitations, rather than theories that attribute difficulty to less expected structures.