Continual trials spontaneous recognition tasks in mice: reducing animal numbers and improving our understanding of the mechanisms underlying memory

Spontaneous recognition tasks are widely used as a laboratory measure of memory in animals but give rise to high levels of behavioural noise leading to a lack of reliability. Previous work has shown that a modification of the procedure to allow continual trials testing (in which many trials are run concurrently in a single session) decreases behavioural noise and thus significantly reduces the numbers of rats required to retain statistical power. Here we demonstrate for the first time that this improved method of testing extends to mice, increasing the overall power of the approach. Moreover, our results show that the new continual trials approach provides the additional benefits of heightened sensitivity and thus provides greater insight into the mechanisms at play. Standard (c57) and transgenic Alzheimer model (TASTPM) mice were tested both at 7 and 10 months of age in both object recognition (OR) and object location (OL) spontaneous recognition tasks using the continual trials methodology. Both c57 and TASTPM mice showed age-dependent changes in performance in OR. While c57 mice also showed age-related changes in performance of OL, TASTPM mice were unable to perform OL at either age. Significantly, we demonstrate that differences in OL performance in c57s and TASTPM animals is a result of proactive interference rather than an absolute inability to recognise object-location combinations. We argue that these continual trials approaches provide overall improved reliability and better interpretation of the memory ability of mice, as well as providing a significant reduction in overall animal use

'Seeing’ proximal representations: Testing attitudes to the relationship between vision and images

Corrections applied by the visual system, like size constancy, provide us with a coherent and stable perspective from ever-changing retinal images. In the present experiment we investigated how willing adults are to examine their own vision as if it were an uncorrected 2D image, much like a photograph. We showed adult participants two lines on a wall, both of which were the same length but one was closer to the participant and hence appeared visually longer. Despite the instruction to base their judgements on appearance specifically, approximately half of the participants judged the lines to appear the same. When they took a photo of the lines and were asked how long they appeared in the image their responses shifted; now the closer line appeared longer. However, when they were asked again about their own view they reverted to their original response. These results suggest that many adults are resistant to imagining their own vision as if it were a flat image. We also place these results within the context of recent views on visual perspective-taking

Perirhinal cortex and the recognition of relative familiarity

Spontaneous object recognition (SOR) is a widely used task of recognition memory in rodents which relies on their propensity to explore novel (or relatively novel) objects. Network models typically define perirhinal cortex as a region required for recognition of previously seen objects largely based on findings that lesions or inactivations of this area produce SOR deficits. However, relatively little is understood about the relationship between the activity of cells in the perirhinal cortex that signal novelty and familiarity and the behavioural responses of animals in the SOR task. Previous studies have used objects that are either highly familiar or absolutely novel, but everyday memory is for objects that sit on a spectrum of familiarity which includes objects that have been seen only a few times, or objects that are similar to objects which have been previously experienced. We present two studies that explore cellular activity (through c-fos imaging) within perirhinal cortex of rats performing SOR where the familiarity of objects has been manipulated. Despite robust recognition memory performance, we show no significant changes in perirhinal activity related to the level of familiarity of the objects. Reasons for this lack of familiarity-related modulation in perirhinal cortex activity are discussed. The current findings support emerging evidence that perirhinal responses to novelty are complex and that task demands are critical to the involvement of perirhinal cortex in the control of object recognition memory

Grammatical gender and linguistic relativity: A systematic review

Many languages assign nouns to a grammatical gender class, such that ‘bed’ might be assigned masculine gender in one language (e.g. Italian) but feminine gender in another (e.g. Spanish). In the context of research assessing the potential for language to influence thought (the linguistic relativity hypothesis), a number of scholars have investigated whether grammatical gender assignment ‘rubs off’ on concepts themselves, such that Italian speakers might conceptualise beds as more masculine than Spanish speakers. We systematically reviewed 43 pieces of empirical research examining grammatical gender and thought, which together tested 5,895 participants. We classified the findings in terms of their support for this hypothesis, and assessed the results against parameters previously identified as potentially influencing outcomes. Overall, we found that support was strongly task- and context-dependent, and rested heavily on outcomes that have clear and equally-viable alternative explanations. We also argue that it remains unclear whether grammatical gender is in fact a useful tool for investigating relativity

Self-referential memory in autism spectrum disorder and typical development: Exploring the ownership effect

Owned objects occupy a privileged cognitive processing status and are viewed almost as extensions of the self. It has been demonstrated that items over which a sense of ownership is felt will be better remembered than other items (an example of the “self-reference effect”). As autism spectrum disorder (ASD) is characterised by an a typical self-concept, people with ASD may not demonstrate this “ownership effect”. Two experiments were conducted which replicate and extend Cunningham, Turk, MacDonald, and Macrae (2008). In Experiment 1, neurotypical adults completed a card sorting task and cards belonging to the ‘self’ were better remembered than cards belonging to another person. In Experiment 2, adults with ASD recalled self- and other owned items equally well. These results shed light both on the relation between sense of self and the ownership effect, and the nature of the self-concept in ASD

Impaired episodic simulation in a patient with visual memory deficit amnesia

For the first time, we assess episodic simulation in a patient with visual memory deficit amnesia, following damage to visual association cortices. Compared to control participants, the patient with visual memory deficit amnesia shows severely restricted responses when asked to simulate different types of future episodic scenarios. Surprisingly, the patient’s responses are more limited in cases where the scenarios require less reliance on visual information. We explain this counterintuitive finding through discussing how the severe retrograde amnesia in visual memory deficit amnesia limits the patient’s access to episodic memories in which vision has not been a focus of their life. As a result, we argue that the deficits in visual memory deficit amnesia continue to distinguish it from amnesia after direct damage to the hippocampus

Ventral prefrontal cortex is not essential for working memory

It is widely held that the prefrontal cortex is important for working memory. It has been suggested that the inferior convexity (IC) may play a special role in working memory for form and color (Wilson et al., 1993). We have therefore assessed the ability of monkeys with IC lesions to perform visual pattern association tasks and color-matching tasks, both with and without delay. In experiment 1, six monkeys were trained on a visual association task with delays of up to 2 sec. Conservative IC lesions that removed lateral area 47/12 in three animals had no effect on the task. Further experiments showed that these lesions had no effect on the postoperative new learning of a It is widely held that the prefrontal cortex is involved in working memory (Goldman-Rakic, 1987, 1996; Funahashi and Kubota, 1994). In animal-based research, working memory refers to the ability to hold information “on-line ” to guide behavior in the absence o