A dissociation between simple and complex span impairment in alcoholics

We investigated whether the surprisingly good memory performance of alcoholics may result from simple memory performance being spared while performance in complex memory tasks is impaired. Simple word span was contrasted with a complex word span task involving concurrent monitoring and re-organisation of items for recall. To control for disruption of rehearsal in the complex word span task, performance on two additional tasks with disrupted rehearsal but no additional processing components was studied. As hypothesised, the alcoholics showed a deficit in the complex but not the simple word span task. They were also impaired, compared to controls, on both tasks with disrupted rehearsal. The difference between groups remained in the complex span task when scores in simple span and either of the two other tasks were used as covariates. Thus, both executive processes necessary for coping with disrupted rehearsal and additional processes scheduling processing and storage in a complex task may play a role in accounting for working memory deficits found in alcoholics.     

A dissociation between perceptual explicit and implicit memory processes

Patient M.S., who underwent right-occipital lobe resection to treat intractable epilepsy, has intact recall and recognition memory for words, but impaired repetition priming in word identification and visual stem-completion tasks. This mirror dissociation to amnesia suggests that explicit recognition and visuoperceptual repetition priming are mediated by distinct neural systems. In prior studies, however, M.S.' recognition memory was tested only with tasks that drew upon his intact verbal knowledge. The present study examined M.S.' recognition memory for nonverbal perceptual information, namely, the modality and font of word presentation and line patterns. M.S.' recognition memory was intact, providing further evidence that perceptual explicit and implicit memory processes are subserved by functionally and neurally independent memory systems.     

Developmental dissociation of excitability and secretory ability in Aplysia bag cell neurons

1. Despite the considerable progress made in understanding the role of electrical activity in triggering secretion, the developmental relationships between excitability and secretion are not well understood. The well-characterized bag cell neurons of Aplysia provide an advantageous system in which to investigate developmental interactions of these two key properties of neurons. 2. A prolonged afterdischarge triggers egg laying hormone (ELH) secretion in mature bag cell neurons. To investigate secretion in the developmental framework of excitability, we first examined whether immature neurons, which are incapable of the mature form of excitability (afterdischarge), contain ELH and whether this hormone is packaged in vesicles. We used immunoelectron microscopy to compare vesicular localization of ELH and to compare the size and density of ELH-containing vesicles in neurons from adult and juvenile Aplysia. This comparison revealed that immature neurons contain ELH in vesicles in the size range of secretory vesicles. However, they lack a class of large vesicles (> 250 nm in diameter) that is characteristic of mature neurons. 3. To investigate whether the ELH contained in immature bag cell neurons could be secreted in response to electrical activity, we used the potassium channel blocker tetraethylammonium (TEA) combined with nerve stimulation to depolarize neurons from both juvenile animals (ovotestes do not contain eggs) and from adult Aplysia (ovotestes contain eggs). Using radioimmunoassay, we have found that the duration and amount of ELH secreted from bag cell neurons from juvenile Aplysia in response to TEA does not depend on whether or not the cells can be induced to afterdischarge, and the amount and duration of ELH secreted from bag cell neurons of juvenile Aplysia (whether or not they afterdischarged) differed from those secreted by adult neurons. However, by normalizing for body size, we found that the final estimated hemolymph concentration of ELH would be similar in juvenile and adult animals. 4. We investigated the potential functional significance of secretion of bag cell hormones in juvenile Aplysia by attempting to bypass the bag cell neurons and directly activate downstream elements with extract from adult bag cell neurons (BCE), known to contain ELH and other peptides. We found that juvenile Aplysia exhibit at least one component of egg-laying behavior, cessation of locomotion, in response to BCE during a developmental period (as measured by weight) in which they normally would possess neurons incapable of afterdischarge. Thus developmental regulation of excitability in the bag cell neurons may prevent inappropriate hormone release and subsequent premature expression of reproductive behaviors.     

Early developments in the ability to understand the relation between stimulus and reward.

Delayed nonmatching to sample (DNMS) is used to test the recognition memory function dependent on the medial temporal lobe. Children cannot succeed on this task until about 21 months. Because robust recognition is present well before then, the late emergence of another ability must account for the late success on DNMS. Evidence is presented here that the critical late-maturing confidence is the ability to grasp the relation between stimulus and reward—that is, to understand that the stimulus is a symbol or marker for the reward. Infants of 9 and 12 months were tested on 3 conditions of DNMS. A sample object was presented. After a delay, the sample and a novel object appeared; choice of the novel object was rewarded. In the standard task, the reward was in a well beneath the stimulus. In the verbal-reward condition the reward was not a separate object but was praise and applause. In the Velcro condition, the reward, although a separate and separable object, was attached to the base of the stimulus. Most infants at both ages succeeded in the verbal-reward and Velcro conditions but not in the standard condition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Journey to the center of the category: The dissociation in amnesia between categorization and recognition.

The authors' theoretical analysis of the dissociation in amnesia between categorization and recognition suggests these conclusions: (a) Comparing to-be-categorized items to a category center or prototype produces strong prototype advantages and steep typicality gradients, whereas comparing to-be, categorized items to the training exemplars that surround the prototype produces weak prototype advantages and flat typicality gradients; (b) participants often show the former pattern, suggesting their use of prototypes; (c) exemplar models account poorly for these categorization data, but prototype models account well for them; and (d) the recognition data suggest that controls use a single-comparison exemplar-memorization process more powerfully than amnesics. By pairing categorization based in prototypes with recognition based in exemplar memorization, the authors support and extend other recent accounts of cognitive performance that intermix prototypes and exemplars, and the authors reinforce traditional interpretations of the categorization-recognition dissociation in amnesia. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Influence of verbal and nonverbal references to print on preschoolers' visual attention to print during storybook reading.

How much do preschool children look at print within storybooks when adults read to them? This study sought to answer this question as well as to examine the effects of adult verbal and nonverbal references to print on children's visual attention to print during storybook reading. Forty-four preschool-aged children participated in this study designed to determine the amount of visual attention children paid to print in 4 planned variations of storybook reading. Children's visual attention to print was examined when adults commented and questioned about print (verbal print condition) or pointed to and tracked the print (nonverbal print condition), relative to 2 comparison conditions (verbatim reading and verbal picture conditions). Results showed that children rarely look at print, with about 5%-6% of their fixations allocated to print in verbatim and verbal picture reading conditions. However, preschoolers' visual attention to print increases significantly when adults verbally and nonverbally reference print; both reading styles exerted similar effects. The authors conclude that explicit referencing of print is 1 way to increase young children's contacts with print during shared storybook reading. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A double dissociation between the rat hippocampus and medial caudoputamen in processing two forms of knowledge.

Rats with hippocampus, medial caudoputamen (CPU), lateral CPU, or control lesions were trained on declarative and procedural knowledge variants of a novel rodent sequential learning task. Medial CPU lesions impaired rats' ability to learn the procedure of running through a sequence of open maze arms but did not disrupt their capacity to explicitly generate (i.e., "declare") maze arm sequences. Hippocampus lesions produced the opposite set of results. Rats with lateral CPU lesions were not impaired on either version of the task. Transfer tests indicated that control rats predominantly used egocentric cues to solve the procedural task and allocentric spatial cues to solve the declarative task. These findings suggest a double dissociation between the medial CPU and hippocampus in processing egocentric-procedural and allocentric- declarative sequential information, respectively. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Types and tokens in visual processing: A double dissociation between the attentional blink and repetition blindness.

In rapid serial visual presentation tasks, correct identification of a target triggers a deficit for reporting a 2nd target appearing within 500 ms: an attentional blink (AB). A different phenomenon, termed repetition blindness (RB), refers to a deficit for the 2nd of 2 stimuli that are identical. What is the relationship between these 2 deficits? The present study obtained a double dissociation between AB and RB. AB and RB followed different time courses (Experiments 1 and 4A), increased target-distractor discriminability alleviated AB but not RB (Experiments 2 and 4A), and enhanced episodic distinctiveness of the two targets eliminated RB but not AB (Experiments 3 and 4B). The implications of the double dissociation between AB and RB for theories of visual processing are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Double dissociation between item and source memory.

The present experiment provides evidence for a double dissociation between item and source memory, thereby strengthening the claim that the 2 kinds of memory rely on different brain structures. Elderly participants were divided preexperimentally into 2 groups on the basis of their scores on a composite measure of frontal lobe function. In a subsequent test of sentence memory, the 2 groups did not differ; on a test of memory for the voice in which sentences were spoken, participants with high-frontal function outperformed those with low-frontal function. When the same participants were divided according to a composite measure of medial temporal lobe function, the high-functioning adults outperformed the low-functioning adults on memory for the sentence, but the groups did not differ on memory for voice. Results focus on different theories of frontal lobe function. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Two forms of spatial memory: A double dissociation between the parietal cortex and the hippocampus in the rat.

Two variants of a continuous recognition training procedure were designed in order to query 2 forms of spatial memory. A continuous reinforcement condition (reflecting perceptual memory) and a differential reinforcement condition (reflecting episodic-like memory) were used to test rats on a 12-arm radial maze. After total hippocampal lesions, rats demonstrated intact performance on the continuous reinforcement condition, but impaired performance on the differential reinforcement condition. After parietal lesions, rats demonstrated the reverse pattern of performance: impaired performance on the continuous reinforcement condition and intact performance on the differential reinforcement condition. Thus, a double dissociation appears to exist between parietal cortex and hippocampus for the continuous reinforcement condition (reflecting perceptual memory) versus the differential reinforcement condition (reflecting episodic memory) for spatial location information. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Relationship between automaticity in handwriting and students' ability to generate written text.

The ability to generate written text requires the execution of a complex array of cognitive and metacognitive skills. Because of the cognitive demands of this complexity, successful writers must be able to write letters and words automatically. This article reports 2 studies that examined the relationship between orthographic-motor integration related to handwriting and the ability to generate creative and well-structured written text. Participants in the first study were 114 Grade 1 students. When the effect of reading was controlled, orthographic-motor integration accounted for 67% of the variance in written expression. An intervention study with 19 students experiencing difficulty in handwriting and 19 students matched on gender and reading examined the impact of improving students automaticity in handwriting. The intervention eliminated the detrimental effects on writing of lack of automaticity in orthographic-motor integration. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The ability to distinguish between comprehension and memory: Failing to succeed.

The authors investigated 1st graders' ability to select the appropriate strategy for constructing a building from memory versus constructing a building while listening to instructions that included an unfamiliar word. In 2 experiments, children's strategy selections (a) preceded any construction attempts, (b) followed failed construction attempts, or (c) followed verbal feedback about construction failures. Long-term strategy maintenance also was assessed. First graders who selected strategies after concrete failure experiences were more likely to select appropriate strategies than children whose strategy selections preceded construction attempts. Failure experiences may help children recognize task goals, assess their inability to achieve these goals, and identify the source of this inability. However, concrete failure experiences did not result in long-term strategy maintenance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A comparison of standardized and narrative letters of recommendation

OBJECTIVE: To compare the Council of Emergency Medicine Residency Directors' (CORD's) standardized letters of recommendation (SLORs) with traditional narrative letters of recommendation (NLORs) with regard to interrater reliability, consistency, and time of interpretation. METHODS: In part I of the study, four members of the residency selection committee each evaluated the same 20 SLORs and 20 NLORs from which all identifying characteristics had been deleted. Using Likert-type scales of the global assessment, each letter was assigned a numeric value from 1 to 7. The interrater reliability was calculated for both types of letters using the Kendall coefficient of concordance. Average time to interpretation of the letters was also determined. In part II, using the same numeric values as in part I, 207 single-author SLOR/NLOR pairs were evaluated to determine whether the global assessment of the SLOR was consistent with that of its partner NLOR. Interpretation of the NLOR was performed blinded to the SLOR. Statistical analysis was calculated using Spearman correlation coefficients. RESULTS: In part I of the study, the interrater reliability of the SLOR was 0.97, as compared with 0.78 for the NLOR. The average time to interpret the global assessment of the SLOR was 16 seconds, vs 90 seconds for the NLOR. In part II of the study, of the 207 SLOR/NLOR pairs, 112 (54%) were assigned the same numeric value, 80 (39%) differed by one, 13 (6%) differed by two, and two (1%) differed by three, for an overall correlation of 0.58. CONCLUSIONS: Compared with NLORs, the CORD SLOR offers better interrater reliability with less interpretation time. Single-author SLOR/NLOR pairs submitted for a single applicant do not correlate well. Residency selection committees must decide whether the added work of interpreting NLORs is beneficial.     

Your research: how to get it on paper and in print

Much worthwhile medical research is never accepted for publication or is ignored when published, often because it is poorly presented. The purpose of this article is to express in simple language how research is best presented in writing. Few actual data are given, though much experience is summarized. The result desired is greater ease, clarity, and effectiveness in communicating medical research. The principles presented here are intended to make medical research writing easier and clearer and to give the research itself more impact.     

Letter names help children to connect print and speech.

A critical step in the acquisition of literacy involves learning that the printed forms of words symbolize the words' linguistic forms. We propose that children first connect print and speech by noticing links between letters in printed words (e.g., the b of beach) and letter names in the corresponding spoken words (e.g., the /bi/ in the spoken word beach). Support for this proposal comes from 2 experiments in which preschoolers were asked to say the first letters of words. Children were relatively good at telling that beach and beaver began with b and that deaf ended with f. They were less likely to know that bone and bonus began with b and that loaf ended with f. Moreover, some children stated that wife began with y and that seem began with c. These errors reflect the letter names at the beginnings of the spoken words. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Patterns of dissociation between left hemineglect and deviation of the egocentric reference

Sixteen control subjects and six right brain-damaged patients with left hemiparesis (three showing signs of left unilateral neglect, three with no signs of neglect) performed a straight-ahead pointing task with their right hand while blindfolded. The aim was to test the hypothesis that the egocentric reference shows significant ipsilesional deviation in left neglect patients. We found no correlation between the position of the egocentric reference and the presence of neglect signs. Neglect patients, like non-neglect patients, showed leftward, rightward or no significant deviation when pointing straight ahead. Results are discussed with reference to egocentric hypotheses of neglect and experimental remission of neglect.     

Relationship between initial competence and ability to profit from cues in brain-damaged individuals.

To study the relationships between competence and ability to profit from cues, the effects of premorbid education on current test performances, and whether the ability to profit from cues is uniform across tasks in brain-damaged persons, 62 left hemiplegics were tested consecutively on the WAIS Block Design (BD) and Similarities (SIM) tests, under standard and specially designed cuing conditions. Results indicate that the ability to profit from cues is a linear function of competence levels in both tasks. In BD, premorbid education was unrelated to either competence or cues gain. In SIM, education correlated with current competence but not with cues. No relationship was found between ability to gain from cues across tasks. Some significant clinical and theoretical implications from the data are discussed. (37 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)