Geography and Giving: The Culture of Philanthropy in New England and the Nation

Looks at aggregate household wealth and income at the national level and for Massachusetts as a state, and analyzes levels of charitable giving in relation to household income

When is the rat retrosplenial cortex required for stimulus integration?

The rodent retrosplenial cortex is known to be vital for spatial cognition but evidence also points to a role in processing non-spatial information. It has been suggested that the retrosplenial cortex may serve as a site of integration of incoming sensory information. To examine this proposal, the current set of experiments assessed the impact of excitotoxic lesions in the retrosplenial cortex on two behavioral tasks that tax animals’ ability to process multiple and overlapping environmental stimuli. In Experiment 1 rats with retrosplenial lesions acquired a negative patterning discrimination, a form of configural learning that can only be solved by learning the conjunction of cues. Subsequent transfer tests confirmed that both the lesion and control animals had solved the task by using configural representations. Furthermore, in Experiment 2 a second cohort of retrosplenial lesion animals successfully acquired conditioned inhibition. Nevertheless, the same animals failed a subsequent summation test which assesses the ability to transfer what has been learnt about one stimulus to another stimulus in the absence of reinforcement. Taken together these results suggest that in the non-spatial domain, the retrosplenial cortex is not required for forming associations between multiple or overlapping environmental stimuli and, consequently, retrosplenial engagement in such processes is more selective than previously envisaged

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

A novel role for the rat retrosplenial cortex in cognitive control

By virtue of its frontal and hippocampal connections, the retrosplenial cortex is uniquely placed to support cognition. Here, we tested whether the retrosplenial cortex is required for frontal tasks analogous to the Stroop Test, i.e., for the ability to select between conflicting responses and inhibit responding to task-irrelevant cues. Rats first acquired two instrumental conditional discriminations, one auditory and one visual, set in two distinct contexts. As a result, rats were rewarded for pressing either the right or left lever when a particular auditory or visual signal was present. In extinction, rats received compound stimuli that either comprised the auditory and visual elements that signaled the same lever response (congruent) or signaled different lever responses (incongruent) during training. On conflict (incongruent) trials, lever selection by sham-operated animals followed the stimulus element that had previously been trained in that same test context, whereas animals with retrosplenial cortex lesions failed to disambiguate the conflicting response cues. Subsequent experiments demonstrated that this abnormality on conflict trials was not due to a failure in distinguishing the contexts. Rather, these data reveal the selective involvement of the rat retrosplenial cortex in response conflict, and so extend the frontal system underlying cognitive control

The rat retrosplenial cortex is required when visual cues are used flexibly to determine location

The present study examined the consequences of retrosplenial cortex lesions in rats on two novel spatial tasks. In the first experiment, rats discriminated opposing room views from the same general location, along with their opposing directions of travel (‘Perspective’ task). Rats were trained with food rewards using a go/no-go design. Extensive retrosplenial cortex lesions involving both the granular and dysgranular areas impaired acquisition of this discrimination, which relied on distal visual cues. The same rats were then trained on a non-spatial go/no-go discrimination between different digging media. No lesion effect was apparent. In the final experiment, rats discriminated between two locations within a room (‘Location’ task) such that direction of travel at each location would be of less help in solving the problem. Both extensive retrosplenial lesions and selective dysgranular retrosplenial lesions impaired this Location task. These results highlight the importance of the retrosplenial cortex (areas 29 and 30), including the dysgranular cortex (area 30), for the effective use of distal visual cues to solve spatial problems. The findings, which help to explain the bias away from visual allocentric solutions that is shown by rats with retrosplenial cortex lesions when performing spatial tasks, also support the notion that the region assists the integration of different categories of visuospatial information