Lack of change in CA1 dendritic spine density or clustering in rats following training on a radial-arm maze task.

Background: Neuronal plasticity is thought to underlie learning and memory formation. The density of dendritic spines in the CA1 region of the hippocampus has been repeatedly linked to mnemonic processes. Both the number and spatial location of the spines, in terms of proximity to nearest neighbour, have been implicated in memory formation. To examine how spatial training impacts synaptic structure in the hippocampus, Lister-Hooded rats were trained on a hippocampal-dependent spatial task in the radial-arm maze.  Methods: One group of rats were trained on a hippocampal-dependent spatial task in the radial arm maze. Two further control groups were included: a yoked group which received the same sensorimotor stimulation in the radial-maze but without a memory load, and home-cage controls. At the end of behavioural training, the brains underwent Golgi staining. Spines on CA1 pyramidal neuron dendrites were imaged and quantitatively assessed to provide measures of density and distance from nearest neighbour.  Results: There was no difference across behavioural groups either in terms of spine density or in the clustering of dendritic spines. Conclusions: Spatial learning is not always accompanied by changes in either the density or clustering of dendritic spines on the basal arbour of CA1 pyramidal neurons when assessed using Golgi imaging.

Lesions of retrosplenial cortex spare immediate-early gene activity in related limbic regions in the rat.

The retrosplenial cortex forms part of a network of cortical and subcortical structures that have particular importance for spatial learning and navigation in rodents. This study examined how retrosplenial lesions affect activity in this network by visualising the expression of the immediate-early genes c-fos and zif268 after exposure to a novel location. Groups of rats with extensive cytotoxic lesions (areas 29 and 30) and rats with lesions largely confined to area 30 (dysgranular cortex) were compared with their respective control animals for levels of c-fos expression measured by immunohistochemistry. These cortical lesions had very limited effects on distal c-fos activity. Evidence of a restricted reduction in c-fos activity was seen in the septal dentate gyrus (superior blade) but not in other hippocampal and parahippocampal subareas, nor in the anterior cingulate and prelimbic cortices. Related studies examined zif268 activity in those cases with combined area 29 and 30 lesions. The only clear evidence for reduced zif268 activity following retrosplenial cell loss came from the septal CA3 area. The confined impact of retrosplenial tissue loss is notable as, by the same immediate-early gene measures, retrosplenial cortex is itself highly sensitive to damage in related limbic areas, showing a marked c-fos and zif268 hypoactivity across all of its subareas. This asymmetry in covert pathology may help to explain the apparent disparity between the severity of learning deficits after retrosplenial cortex lesions and after lesions in either the hippocampus or the anterior thalamic nuclei.

The rat retrosplenial cortex as a link for frontal functions: A lesion analysis.

Cohorts of rats with excitotoxic retrosplenial cortex lesions were tested on four behavioural tasks sensitive to dysfunctions in prelimbic cortex, anterior cingulate cortex, or both. In this way the study tested whether retrosplenial cortex has nonspatial functions that reflect its anatomical interactions with these frontal cortical areas. In Experiment 1, retrosplenial cortex lesions had no apparent effect on a set-shifting digging task that taxed intradimensional and extradimensional attention, as well as reversal learning. Likewise, retrosplenial cortex lesions did not impair a strategy shift task in an automated chamber, which involved switching from visual-based to response-based discriminations and, again, included a reversal (Experiment 2). Indeed, there was evidence that the retrosplenial lesions aided the initial switch to response-based selection. No lesion deficit was found on an automated cost-benefit task that pitted size of reward against effort to achieve that reward (Experiment 3). Finally, while retrosplenial cortex lesions affected matching-to-place task in a T-maze, the profile of deficits differed from that associated with prelimbic cortex damage (Experiment 4). When the task was switched to a nonmatching design, retrosplenial cortex lesions had no apparent effect on performance. The results from the four experiments show that many frontal tasks do not require the retrosplenial cortex, highlighting the specificity of their functional interactions. The results show how retrosplenial cortex lesions spare those learning tasks in which there is no mismatch between the internal and external representations used to guide behavioural choice. In addition, these experiments further highlight the importance of the retrosplenial cortex in solving tasks with a spatial component.

The retrosplenial cortex and object recency memory in the rat.

It has been proposed that the retrosplenial cortex forms part of a 'where/when' information network. The present study focussed on the related issue of whether retrosplenial cortex also contributes to 'what/when' information, by examining object recency memory. In Experiment 1, rats with retrosplenial lesions were found to be impaired at distinguishing the temporal order of objects presented in a continuous series ('Within-Block' condition). The same lesioned rats could, however, distinguish between objects that had been previously presented in one of two discrete blocks ('Between-Block' condition). Experiment 2 used intact rats to map the expression of the immediate-early gene c-fos in retrosplenial cortex following performance of a between-block, recency discrimination. Recency performance correlated positively with levels of c-fos expression in both granular and dysgranular retrosplenial cortex (areas 29 and 30). Expression of c-fos in the granular retrosplenial cortex also correlated with prelimbic cortex and ventral subiculum c-fos activity, the latter also correlating with recency memory performance. The combined findings from both experiments reveal an involvement of the retrosplenial cortex in temporal order memory, which includes both between-block and within-block problems. The current findings also suggest that the rat retrosplenial cortex comprises one of a group of closely interlinked regions that enable recency memory, including the hippocampal formation, medial diencephalon and medial frontal cortex. In view of the well-established importance of the retrosplenial cortex for spatial learning, the findings support the notion that, with its frontal and hippocampal connections, retrosplenial cortex has a key role for both what/when and where/when information.

Effects of selective granular retrosplenial cortex lesions on spatial working memory in rats.

The rat retrosplenial cortex comprises two major subregions (granular and dysgranular) that differ in morphology and connectivity. Although the effects of selective dysgranular retrosplenial cortex (area 30) lesions and the effects of selective lesions within separate sub-areas of the granular retrosplenial cortex have been described, the effects of complete granular lesions (area 29) remain unknown. The present study, therefore, contrasted excitotoxic lesions of the total granular retrosplenial cortex with complete retrosplenial cortex lesions (dysgranular plus granular) using two spatial working memory tasks variably sensitive to complete retrosplenial damage. The granular retrosplenial and complete retrosplenial lesion groups were comparably impaired throughout most of radial-arm maze acquisition, including when subsequently challenged by having the maze rotated mid-trial or being tested in the dark. The other test, reinforced spatial alternation in a T-maze, provided a slightly different result as it was the rats with selective granular cortex lesions that were most impaired when the rats were tested in two, parallel mazes (one for the sample run, the other for the test run). These findings reveal the importance of the granular retrosplenial cortex for learning across a variety of different spatial tasks. Combining these findings with the results of previous functional and anatomical studies suggests that the granular and dysgranular retrosplenial subregions function in close conjunction to support spatial learning.

Granular and dysgranular retrosplenial cortices provide qualitatively different contributions to spatial working memory: evidence from immediate-early gene imaging in rats.

The present study revealed striking task-dependent differences in immediate-early gene activity in the two main subregions (granular and dysgranular) of the retrosplenial cortex. In addition, there were activity differences along the rostro-caudal axis of both subregions. Two groups of rats were trained on a working memory task in a radial-arm maze, one group in the light, the other in the dark. Each working memory group had two sets of yoked controls. Working memory consistently increased retrosplenial immediate-early gene activity (c-fos and zif268 ), although systematic differences occurred in the granular and dysgranular subregions. Both c-fos and zif268 expression increased in granular cortex irrespective of whether the spatial memory task was in the light or dark. In contrast, only in the light did spatial memory increase dysgranular cortex activation. Correlations based on the counts of Fos-positive cells helped to reinforce the particular association between the dysgranular retrosplenial cortex and radial-arm maze performance in the light. These results provide clear evidence for proposed functional differences between the major retrosplenial subregions: the granular cortex contributes to spatial learning and navigation based on both internal and external cues (light and dark), while dysgranular cortex is more selectively involved when distal visual cues control performance (light only).

What do mentors find difficult?

AIMS: (i) To assess whether mentors had a positive or negative attitude towards their role; and (ii) to discover what aspects of the role they found easy or difficult. BACKGROUND: The fact that mentorship is an important element in nurse training was recognized by Sir Leonard Peach, the United Kingdom Central Council for Nursing, Midwifery and Health Visiting and the Nursing and Midwifery Council which has recently published new standards to support learning and assessment in practice, which include standards for the preparation of Mentors, to be implemented by September 2007. There are many anecdotal reports of the problems which face mentors, but little firm evidence. METHOD: This paper reports a study of those problems. It used a Thurstone scale to assess role satisfaction among mentors (n = 86, response rate 89%) and two Likert scales to assess where problems, if any, lay. RESULTS: Unlike anecdotal reports, the Thurstone scale found that, overall, mentors regarded the role positively. In addition, a principal components analysis of responses to the Likert scales showed that there were two clearly delineated factors. The first (interpersonal/organisational factors) had been widely discussed in the literature. The second (cognitive/intellectual factors) has been rarely discussed and could with profit be more strongly stressed in mentor training. CONCLUSIONS: (i) Mentors had a positive attitude towards their role and enjoyed it. (ii) When looking at what caused mentors difficulty, in addition to the commonly discussed dimensions of organisational constraints (workload, skill mix) and interpersonal factors, there was clearly an additional cognitive one. Knowledge, not just personality, mattered. IMPLICATIONS FOR CLINICAL PRACTICE: Mentors and those who train them could with profit pay more attention to cognitive components of the role, even if that meant laying a lesser stress on the interpersonal ones.

The training needs of health care support workers: results of a study of workers and their managers.

AIMS AND OBJECTIVES: This study was designed to assess the training needs of health care support workers. In the past, opinions on the topic have been varied, but were rarely based on empirical evidence. DESIGN AND METHODS: The study was designed as a self-report questionnaire survey of health care support workers and their managers in six units in health and social care, using as its basis 32 descriptors from the NHS Knowledge and Skills Framework, levels 1 and 2. The achieved sample was 117, giving a 77% response rate. RESULTS: Thirty-five per cent of respondents thought that health care support workers were 'unable' to perform six or more of the 32 descriptors used, whilst on the criterion of being 'less than able', the figure was 64%. Support workers and their managers agreed closely (rho = 0.8) on where the difficulties lay in achieving Knowledge and Skills Framework competencies. Those difficulties lay particularly in two areas: (1) biomedical/physiological knowledge and (2) data-handling. CONCLUSIONS: We concluded that the numbers in need of training were substantial and the areas of need were the two identified above. RELEVANCE TO CLINICAL PRACTICE: The main implications for clinical practice are that (a) for those who supervise or mentor health care support workers, there should be a greater concentration on the more scientific areas of expertise and (b) a similar emphasis is needed for those who train mentors or supervisors. These implications will become more important over time as scientific knowledge about medicine and health care increases.

Neurotoxic lesions of the rat perirhinal and postrhinal cortices and their impact on biconditional visual discrimination tasks.

It has been argued that damage to the perirhinal cortex should impair visual discriminations when the stimuli have overlapping features. In Experiment 1, rats with perirhinal cortex lesions were trained on a series of visual discriminations in a water tank, culminating in a biconditional discrimination. No evidence was found of a perirhinal lesion deficit, although the same rats showed an object recognition deficit. In Experiment 2 the lesions were extended to involve both the perirhinal and postrhinal cortices in a new group of rats. An impairment was now found on acquisition of the biconditional task, but this was not specific as impairments were also found on two elemental visual discriminations. Taken together, the study failed to find evidence that the rat perirhinal cortex is necessary for configural visual discriminations and so revealed that some ambiguous visual discriminations can be learnt when this area is removed. Furthermore, there was no evidence that the parahippocampal region is selectively dedicated to configural learning, even though the loss of this area can impair the acquisition of some configural tasks.

The effects of cytotoxic perirhinal cortex lesions on spatial learning by rats: a comparison of the dark agouti and Sprague-Dawley strains.

The effects of perirhinal cortex lesions in rats on spatial memory might depend on the choice of strain. The present study, therefore, compared perirhinal lesions in Sprague-Dawley rats (associated with deficits) with Dark Agouti rats (associated with null effects). Tests of reference memory and working memory in the water maze failed to provide evidence that perirhinal lesions disrupt overall levels of performance (irrespective of strain) or that these lesions have differential effects on the rates of spatial learning in these 2 strains. Strain differences were, however, found, as the Dark Agouti strain was often superior. Furthermore, the perirhinal lesions did have differential effects in the 2 strains, but these did not appear to relate directly to changes in spatial learning.