We thank G. Pruzzo for his excellent technical assistance and the IIT mechanical workshop for help in building our new apparatus. This research was supported by the Istituto Italiano di Tecnologia, the Marie Curie FP7-Reintegration-Grant N&#176;268247, and by the Italian Ministry of Health Grants for Young Researchers (GR-2010-2315883).

<ol>
	<li>Keeler, J. F., Robbins, T. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Translating+cognition+from+animals+to+humans.">Translating cognition from animals to humans.</a> Biochemical pharmacology. 81 (12), 1356-1366 (2011).</li><li>Milner, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+Different+Brain+Lesions+on+Card+Sorting.">Effects of Different Brain Lesions on Card Sorting.</a> Arch Neurol. 9, 100-110 (1963).</li><li>Roberts, A. C., Robbins, T. W., Everitt, B. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+effects+of+intradimensional+and+extradimensional+shifts+on+visual+discrimination+learning+in+humans+and+non-human+primates.">The effects of intradimensional and extradimensional shifts on visual discrimination learning in humans and non-human primates.</a> The Quarterly journal of experimental psychology. B, Comparative and physiological psychology. 40 (4), 321-341 (1988).</li><li>Barnett, J. H., Robbins, T. W., Leeson, V. C., Sahakian, B. J., Joyce, E. M., Blackwell, A. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Assessing+cognitive+function+in+clinical+trials+of+schizophrenia.">Assessing cognitive function in clinical trials of schizophrenia.</a> Neuroscience and biobehavioral reviews. 34 (8), 1161-1177 (2010).</li><li>Hill, E. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Executive+dysfunction+in+autism.">Executive dysfunction in autism.</a> Trends in Cognitive Sciences. 8 (1), 26-32 (2004).</li><li>Ceaser, A. E., Goldberg, T. E., Egan, M. F., McMahon, R. P., Weinberger, D. R., Gold, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Set-shifting+ability+and+schizophrenia:+a+marker+of+clinical+illness+or+an+intermediate+phenotype.">Set-shifting ability and schizophrenia: a marker of clinical illness or an intermediate phenotype.</a> Biological psychiatry. 64 (9), 782-788 (2008).</li><li>Owen, A. M., Roberts, A. C., Hodges, J. R., Robbins, T. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Contrasting+mechanisms+of+impaired+attentional+set-shifting+in+patients+with+frontal+lobe+damage+or+Parkinson's+disease.">Contrasting mechanisms of impaired attentional set-shifting in patients with frontal lobe damage or Parkinson's disease.</a> Brain. 116 (5), 1159-1175 (1993).</li><li>Head, D., Bolton, D., Hymas, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Deficit+in+cognitive+shifting+ability+in+patients+with+obsessive-compulsive+disorder.">Deficit in cognitive shifting ability in patients with obsessive-compulsive disorder.</a> Biological Psychiatry. 25 (7), 929-937 (1989).</li><li>Chamberlain, S. R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Translational+approaches+to+frontostriatal+dysfunction+in+attention-deficit/hyperactivity+disorder+using+a+computerized+neuropsychological+battery.">Translational approaches to frontostriatal dysfunction in attention-deficit/hyperactivity disorder using a computerized neuropsychological battery.</a> Biological psychiatry. 69 (12), 1192-1203 (2011).</li><li>Gilmour, G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Measuring+the+construct+of+executive+control+in+schizophrenia:+Defining+and+validating+translational+animal+paradigms+for+discovery+research.">Measuring the construct of executive control in schizophrenia: Defining and validating translational animal paradigms for discovery research.</a> Neuroscience and biobehavioral reviews. , 1-16 (2012).</li><li>Barch, D. M., Braver, T. S., Carter, C. S., Poldrack, R. A., Robbins, T. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=CNTRICS+final+task+selection:+executive+control.">CNTRICS final task selection: executive control.</a> Schizophrenia bulletin. 35 (1), 115-135 (2009).</li><li>Dias, R., Robbins, T. W., Roberts, A. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dissociation+in+prefrontal+cortex+of+affective+and+attentional+shifts.">Dissociation in prefrontal cortex of affective and attentional shifts.</a> Nature. 380 (6569), 69-72 (1996).</li><li>Birrell, J. M., Brown, V. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Medial+Frontal+Cortex+Mediates+Perceptual+Attentional+Set+Shifting+in+the+Rat.">Medial Frontal Cortex Mediates Perceptual Attentional Set Shifting in the Rat.</a> The Journal of Neuroscience. 20 (11), 4320-4324 (2000).</li><li>Bissonette, G. B., Martins, G. J., Franz, T. M., Harper, E. S., Schoenbaum, G., Powell, E. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Double+dissociation+of+the+effects+of+medial+and+orbital+prefrontal+cortical+lesions+on+attentional+and+affective+shifts+in+mice.">Double dissociation of the effects of medial and orbital prefrontal cortical lesions on attentional and affective shifts in mice.</a> The Journal of Neuroscience. 28 (44), 11124-11130 (2008).</li><li>Papaleo, F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genetic+dissection+of+the+role+of+catechol-O-methyltransferase+in+cognition+and+stress+reactivity+in+mice.">Genetic dissection of the role of catechol-O-methyltransferase in cognition and stress reactivity in mice.</a> The Journal of Neuroscience. 28 (35), 8709-8723 (2008).</li><li>Garner, J. P., Thogerson, C. M., W&#252;rbel, H., Murray, J. D., Mench, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Animal+neuropsychology:+validation+of+the+Intra-Dimensional+Extra-Dimensional+set+shifting+task+for+mice.">Animal neuropsychology: validation of the Intra-Dimensional Extra-Dimensional set shifting task for mice.</a> Behavioural brain research. 173 (1), 53-61 (2006).</li><li>Owen, A. M., Roberts, A. C., Polkey, C. E., Sahakian, B. J., Robbins, T. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Extra-dimensional+versus+intra-dimensional+set+shifting+performance+following+frontal+lobe+excisions,+temporal+lobe+excisions+or+amygdalo-hippocampectomy+in+man.">Extra-dimensional versus intra-dimensional set shifting performance following frontal lobe excisions, temporal lobe excisions or amygdalo-hippocampectomy in man.</a> Neuropsychologica. 29 (10), 993-1006 (1991).</li><li>Robbins, T. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+5-choice+serial+reaction+time+task:+behavioural+pharmacology+and+functional+neurochemistry.">The 5-choice serial reaction time task: behavioural pharmacology and functional neurochemistry.</a> Psychopharmacology. 163 (3-4), 362-380 (2002).</li><li>Scheggia, D., Bebensee, A., Weinberger, D. R., Papaleo, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+ultimate+intra-/extra-dimensional+attentional+set-shifting+task+for+mice.">The ultimate intra-/extra-dimensional attentional set-shifting task for mice.</a> Biological psychiatry. 75 (8), 660-670 (2014).</li><li>Machkintosh, N. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+effects+of+overtraining+on+a+reversal+and+a+nonreversal+shift.">The effects of overtraining on a reversal and a nonreversal shift.</a> Journal of Comparative and Physiological Psychology. 55 (4), 555-559 (1962).</li><li>Abraham, N. M., Spors, H., Carleton, A., Margrie, T. W., Kuner, T., Schaefer, A. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Maintaining+accuracy+at+the+expense+of+speed:+stimulus+similarity+defines+odor+discrimination+time+in+mice.">Maintaining accuracy at the expense of speed: stimulus similarity defines odor discrimination time in mice.</a> Neuron. 44 (5), 865-876 (2004).</li><li>Cools, R., Rogers, R., Barker, R. A., Robbins, T. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Top-down+attentional+control+in+Parkinson's+disease:+salient+considerations.">Top-down attentional control in Parkinson's disease: salient considerations.</a> Journal of cognitive neuroscience. 22 (5), 848-859 (2010).</li></ol>

The authors declare that they have no financial conflicts of interest.

In this study we present a novel automated two-chamber ID/ED &#34;Operon&#34; task for mice that is able to reliably measure cognitive flexibility through reversal learning, attentional set formation and shifting. This paradigm is analogous to the WCST and ID/ED tasks commonly used in human and nonhuman primates and overcomes the major limitations of the previous versions for rodents. This Operon paradigm can be used as a new effective tool for large drug and/or genetic screenings relevant to cognitive (dys)functions in mice with high relevance to translational medicine.
This automated task have the following advantages over previously used ID/ED task for rodents: (1) it has less labor-intensive procedures than the manual versions (e.g., the software regulates all the phases of the task, greatly decreasing interventions by the experimenter); (2) it eliminates any source of subjectivity in the measured parameters (e.g.,&#160;the experimenter is not required to judge whether or not the animal has actually made a choice response); (3) it eliminates any possibility that mice might follow reinforcement-related cues in order to make a response (i.e., the reward is always automatically delivered in the center magazine); (4) it avoids arbitrary environmental conditions (e.g.,&#160;use of mazes and apparatus of different sizes/materials, use of manually prepared cue stimuli); (5) it allows manipulation of three distinct dimensions with a large range of different stimuli, in accordance to the equivalent human tasks used in the clinical setting. Here we present data only from mice, but similar advantages might be expected also for rats.
There are critical steps in the task, which are internal construct-validity parameters that can be used in order to identify areliable attentional set-shifting performance: i) poorer performance in the EDS compared to previous stages ii) a general improvement from IDS to IDS2; iii) a specific improvement in consecutive reversal stages, as the more an animal is trained in within-set reversals, the better it should perform on subsequent within-set reversals20; iv) better performance in the EDSRe compared to the EDS. This novel ID/ED operon task presents all these features, consistent with previous studies in primates using the CANTAB ID/ED task and in rodents using the manual &#34;digging&#34; version12,13. Moreover, each stage of this automated task was learnt in an equivalent number of trials irrespective of the relevant/irrelevant dimension used (i.e.,&#160;odor, texture and light)19. This demonstrated that all the stimuli used have similar salience and are suitable for attentional set-formation and/or shifting. Our experiments demonstrate that the difficulty in solving the EDS is also highlighted by the increase in response latencies. Processing time increases to maintain optimal accuracy during harder discriminations21. Thus, considering the latency to respond as an index of speed of information processing, decision-making and problem solving18, the slower latencies during the EDS might reflect a strategy adopted to face the difficulty in solving the set-shifting.
We have shown that our novel apparatus can be effectively used with the more &#39;classical&#39; attentional set-shifting paradigm employing only two dimensions throughout the test (i.e.,&#160;the two-dimension) or with a stuck-in-set paradigm, implying the use of three dimensions. Depending on the cognitive domain of interest, it is possible to choose the most appropriate protocol. Both of these paradigms have been previously used in humans, primates and rodents7,12-17. However, the stuck-in-set procedure is able to distinguish between different components of set-shifting and is a more selective measure of frontal lobe functioning in human patients7,22. Furthermore, one problem that might occur in the two-dimension paradigm is the learned irrelevance that might bias the results. Learned irrelevance perseveration refers to the inability to attend to and learn about information that was previously irrelevant7. This situation can occur in the EDS phase of the two-dimension paradigm, as the subject is required to shift the attention to the previously irrelevant dimension. In this case, it is basically impossible to discern whether an EDS deficit is due to the inability to shift attention away from a previously relevant dimension and/or the inability to now shift the attention to a previously irrelevant dimension. Impairment may then just reflect the active inhibition of responding to a dimension previously made irrelevant by its random association with reinforcing feedback. In contrast, in the stuck-in-set condition, failure to shift to the new relevant dimension cannot be attributed to any prior learning about this dimension since it had not been experienced previously. Failure, therefore, reflects perseveration to the previously relevant dimension. In conclusion, even if in normal wild-type mice the &#39;stuck-in-set&#39; and the &#39;two-dimension&#39; attentional set-shifting paradigms might produce similar results, we expressly prefer the stuck-in-set perseveration for the reasons discussed above.

Attentional set-shifting is a measure of cognitive flexibility and executive functions1. It refers to the ability to switch between arbitrary internal rules (&#34;cognitive-attentional sets&#34;). The most widely used neuropsychological tasks for measuring attentional set-shifting and cognitive flexibility in humans are the Wisconsin Card Sorting Test (WCST)2 and a more recent and more refined version: the intra- and extra-dimensional attentional set-shifting (ID/ED) of the Cambridge Neuropsychological Test Automated Battery (CANTAB)3,4. These tasks have been used to identify specific cognitive abnormalities in a wide range of mental disorders including autism5, schizophrenia6, Parkinson&#39;s disease7, obsessive compulsive disorders8 and attention-deficit/hyperactive disorders9. The clinical relevance and solid methodological approach of the WCST and the ID/ED tests have attracted interest in the implementation of similar tests in preclinical research10,11. These tasks allow for the selective measurement within the same subject of different cognitive abilities such as discriminative learning, reversal learning, formation of an attentional set, shifting of attention within the same dimension (i.e., intra-dimensional shift: IDS) and between different perceptual dimensions (i.e., extra-dimensional shift: EDS). This is crucial because distinct brain circuits, as well as neuropathology might alter these distinct cognitive functions in different ways. For example, a double dissociation or functional specialization effect has been demonstrated between the lateral (in monkeys and humans) / medial (in rodents) and orbital regions of the PFC in the attentional set-shifting tasks. While the orbitofrontal cortex is more involved in the reversal phases of these tasks, the lateral/medial PFC region governs the extra-dimensional shift stages12-14.
Rodent versions of these attentional set-shifting tests for primates have been successfully generated13-16. However, some aspects of these rodent versions have been limiting their applications and use. For instance, these tasks are manually run and therefore highly labor-intensive and difficult to standardize. Moreover, the presence of food reinforcers inside the stimuli might result in an ambiguous interpretation of animal responses and potential bias in choice-making10. These characteristics have limited the throughput of testing and, more importantly, their application in large-scale genetic and/or drug-screening studies.
To overcome these limitations and to enhance the potential applications of ID/ED shift paradigms in rodents, we present here a novel two-chamber operant-based task to test cognitive flexibility in mice. This novel task closely mimics the ID/ED task used in human and non-human primates and circumvents the problems of earlier rodent versions.

<table><tbody><tr><td>Plexiglas walls and aluminum floor</td><td>Custom made</td><td></td><td>(16 x 16 x 16 cm for each chamber)</td></tr><tr><td>Plexiglas door&amp;nbsp;</td><td>Custom made</td><td></td><td></td></tr><tr><td>PC</td><td>Dell Inc.</td><td></td><td></td></tr><tr><td>MED-PC IV software&amp;nbsp;</td><td>(Med Associates, St. Albans, VT, USA)</td><td>custom made</td><td>Use an operant code in order to automatically control the presentation of the stimuli and the sequence of the stages</td></tr><tr><td>Nose-poke hole&amp;nbsp;</td><td>Med Associates, St. Albans, VT, USA)</td><td>ENV-314M</td><td></td></tr><tr><td>Food magazine&amp;nbsp;</td><td>Med Associates, St. Albans, VT, USA)</td><td>ENV-303M</td><td></td></tr><tr><td>Pellet dispenser for food reinforcement&amp;nbsp;</td><td>Med Associates, St. Albans, VT, USA)</td><td>ENV-203-14P</td><td></td></tr><tr><td>Houselight&amp;nbsp;</td><td>Med Associates, St. Albans, VT, USA)</td><td>ENV-315M</td><td></td></tr><tr><td>Dilution olfactometer&amp;nbsp;</td><td>(Med Associates, St. Albans, VT, USA)</td><td>PHM-275</td><td></td></tr><tr><td>Liquid odorants</td><td>(Sigma Aldrich, Dorset, UK)</td><td></td><td>(see Table 1)</td></tr><tr><td>Mineral oil</td><td>(Sigma Aldrich, Dorset, UK)</td><td>M5904</td><td></td></tr><tr><td>Air pump and vacuum</td><td>(Med Associates, St. Albans, VT, USA)</td><td>PHM-280</td><td>Vacuum is recommended for scents removal at the end of each trial</td></tr><tr><td>Light-emitting diodes (LED)</td><td></td><td></td><td>High-intensity, transparent gem, 3 mm</td></tr><tr><td>Floor textures</td><td></td><td></td><td>3x3 cm</td></tr><tr><td>Reinforcement pellets</td><td>TestDiet</td><td>5TUL 14mg</td><td>For mice</td></tr></tbody></table>

an operant intra-/extra-dimensional set-shift task for mice

Alterations in executive control and cognitive flexibility, such as attentional set-shifting abilities, are core features of several neuropsychiatric diseases. The most widely used neuropsychological tests for the evaluation of attentional set-shifting in human subjects are the Wisconsin Card Sorting Test (WCST) and the CANTAB Intra-/Extra-dimensional set shift task (ID/ED). These tasks have proven clinical relevance and have been modified and successfully adapted for research in animal models. However, currently available tasks for rodents present several limitations, mainly due to their manual-based testing procedures, which are hampering translational advances in psychiatric medicine. To overcome these limitations and to better mimic the original version in primates, we present the development of a novel operant-based two-chamber ID/ED "Operon" task for rodents. We demonstrated the effectiveness of this novel task to measure different facets of cognitive flexibility in mice including attentional set formation and shifting, and reversal learning. Moreover, we show the high flexibility of this task in which three different perceptual dimensions can be manipulated with a high number of stimuli cues for each dimension. This novel ID/ED Operon task can be an effective preclinical tool for drug testing and/or large genetic screening relevant to the study of executive dysfunction and cognitive symptoms found in psychiatric disorders.

Figure 2 shows an example of the ID/ED task. Pairs of stimuli (either &#39;Discrimination 1&#39; or &#39;Discrimination 2&#39;) are randomly presented in each stage, and the mouse must choose the correct stimulus in each pair. In this example table, the correct exemplar is reported in bold. In the first stage (SD or simple discrimination), the stimuli presented in the two nose-poke holes differed in one of three dimensions (e.g., O1: Vanilla vs. O2: Lavender) and the mouse is rewarded for choosing the correct exemplar (e.g., O1). Once the subject reaches the criterion in this stage, the next stage (CD or compound discrimination) begins, where the same exemplars of the relevant dimension are presented overlaid at random by exemplars of a second, but irrelevant dimension, introduced as a confounding factor (e.g., L1: blue light vs.L2: yellow light). Two different discriminations are possible in this stage (either &#39;Discrimination 1&#39; or &#39;Discrimination 2&#39;). In the next stage (CDRe or compound discrimination reversal), the reward contingencies are reversed but the exemplars and the relevant dimension are unchanged: the mouse has to learn that the previously correct stimulus is now incorrect (e.g., lavender odor is now rewarded). In the next stage (IDS or intra-dimensional shift), new exemplars (both odors and lights) are introduced but the relevant dimension (odor in this example) remains the same (e.g., strawberry is the correct choice). In the next stage (IDR or intra-dimensional reversal), the reward contingencies are reversed. After a second intra-dimensional shift (IDS2 and its reversal), new exemplars are introduced to test the extra-dimensional shift (EDS) in which the relevant dimension is changed. In the &#39;stuck-in-set&#39; EDS, the mouse has to focus on the new dimension (e.g.,&#160;the Texture, T1: coarse sandpaper vs. T2: fine sandpaper), while the previously relevant dimension (in this case, odor) is now the irrelevant dimension. In the &#39;two-dimension&#39; EDS, the previously irrelevant dimension (in this case, light) is now the relevant dimension. In the final stage (EDSRe or extra-dimensional reversal), the reward contingencies are reversed.
In order to obtain reliable results, the stimulus dimensions used in the task should be equally well-learned. As shown in Figure 3, visual, tactile and odor discriminations in this novel apparatus required similar time (F(2,64)=0.36; p=0.69) and similar number of trials (F(2,64)=0.059; p=0.94) to reach the criterion, suggesting that animals are able to perform simple discriminations regardless the dimension presented.
If a reliable attentional set has been developed over the testing phases of the task, the performance of a normal wild-type mouse should be poorer in the EDS stage compared to previous and following stages, as reported in previous studies in rodents and primates12,13. In particular, a robust increase of time and trials needed to reach criteria should be found in the EDS compared to the IDS stages. As illustrated in Figure 4, in our experiment with the &#39;stuck-in-set&#39; protocol, analysis of performance of the mice revealed a discrimination effect for the number of trials (F(8,168)=9.23; p&#60;0.0001) and time (F(8,168)=8.62; p&#60;0.0001) required to reach criteria. Indeed, mice needed more trials and more time to solve the EDS stage compared to the CD, IDS, IDS2 and EDSRe stages (p&#60;0.05; Figure 4A-B). Similarly, analysis of performance tested with the &#39;two-dimension&#39; protocol (Figure 5) showed a significant discrimination effect for the number of trials (F(8,72)=3.66; p&#60;0.005) and time (F(8,72)=4.65; p&#60;0.0005) needed to reach criteria. Indeed, we show that mice required more trials (p&#60;0.05) and more time (p&#60;0.05) to solve the EDS compared to CD, IDS, IDS2 and EDSRe (Figure 5A-B). No differences in shifting abilities should be observed between mice tested with different dimensions.
In a normal wild-type mouse, the first reversal learning (i.e., CDRe) is more difficult than the initial discrimination (i.e., CD). In agreement, as evident from Figures 4 and 5, mice needed more trials (p&#60;0.05; Figure 4-5A) and more time (p&#60;0.05; Figure 4-5B) to complete this stage. Moreover, reversal performance should improve from CDRe to IDSRe to IDS2Re, as we show in our experiment with both the &#39;stuck-in-set&#39; and &#39;two-dimension&#39; protocols. These results further strengthen the evidence of the formation of an attentional set through the task.
Throughout the task, the mice should improve their speed to respond over consecutive stages. Accordingly, the analysis of the latency to respond showed a significant discrimination effect (F(8,200)=42.59; p&#60;0.0001). In particular, as demonstrated by representative results in Figure 4C the latency to poke in the IDS2 stage is decreased compared to that in the IDS, CD and SD stages (p&#60;0.0005). Moreover, the latency to respond increased during the EDS stage compared to the previous IDS2 and IDS2Re and successive EDSRe stages (p&#60;0.05). In line with these results, the analysis of the latency to respond during the &#39;two-dimension&#39; task also showed a significant effect of discrimination (F(7,63)=9.98; p&#60;0.0005). As shown in Figure 5C, the latency to make a choice was increased during the EDS compared to previous IDS2 and IDS2Re and successive EDSRe (p&#60;0.05). Since the latency to respond has been considered an index of decisional processing18, these results further suggest that the mice encountered some problems processing the new discriminative rule during the EDS. Based on the behavioral performance of wild-type mice (Figure 4-5), we determined that the minimal number of sample size (by R power analysis) for each experimental group should be 8.
<img alt="Figure 3" src="/files/ftp_upload/53503/53503fig3.jpg" /> 
Figure 3. Simple discriminations of light, odor and texture are equivalent. (A) Number of trials and (B) time required to reach the criterion on simple discriminations with only light, odor or texture stimuli. Values represent mean &#177; SEM throughout Figures 2-4. Data originally published in &#39;The ultimate Intra- and Extradimensional Attentional Set-Shifting Task for Mice&#39;19.
<img alt="Figure 4" src="/files/ftp_upload/53503/53503fig4.jpg" /> 
Figure 4. Wild-type C57BL6J male mice performance in the &#39;stuck-in-set&#39; ID/ED Operon task. (A) Trials, (B) time (in minutes) and days needed to reach the criterion in the different stages of the ID/ED Operon task using a &#39;stuck-in-set&#39; ID/ED paradigm. (C) Time (in seconds) elapsed between the opening of the divider door and a nose-poke response (latency to respond) during the different stages of the task. A total of 26 mice were tested; 4 mice were excluded because they were not reliably poking to retrieve the food reinforcement during the training or were not able to finish the entire procedure. A: *p &#60;0.05 versus CD, IDS, IDS2, IDS2Re and EDSRe; B: *p &#60;0.05 versus CD, IDS2, IDS2Re and EDSRe. A and B: #p&#60;0.05, ##p&#60;0.005 versus CD, IDSRe and IDS2Re. C: *p &#60;0.05 versus IDS2, IDS2Re and EDSRe. Note that the mice were able to complete the entire task in 5-9 days in all experiments reported in Figures 3-4. Data originally published in &#39;The ultimate Intra- and Extradimensional Attentional Set-Shifting Task for Mice&#39;19. <a href="https://www-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/53503/53503fig4large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 5" src="/files/ftp_upload/53503/53503fig5.jpg" />
Figure 5. Wild-type C57BL6J male mice performance in the &#39;two-dimension&#39; ID/ED Operon task. (A) Trials, (B) time (in minutes) and days needed to reach the criterion in the different stages of the ID/ED Operon task using a two-dimension paradigm. (C)Time (in seconds) elapsed between the opening of the divider door and a nose-poke response (latency to respond) during the different stages of the task. A total of 13 mice were tested; 3 mice were excluded because they were not reliably poking to retrieve the food reinforcement during the training or were not able to finish the entire procedure. A and B:#p&#60;0.05 versus CD and IDS2Re, *p &#60;0.05 versus CD, IDS, IDS2, EDSRe. C:*p &#60;0.05 versus IDS2, IDS2Re and EDSRe. Data originally published in &#39;The ultimate Intra- and Extradimensional Attentional Set-Shifting Task for Mice&#39;19. <a href="https://www-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/53503/53503fig5large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 6" src="/files/ftp_upload/53503/53503fig6.jpg" /> 
Figure 6. Timeline of the entire procedure of the protocol to test ID/ED task.
<table fo:keep-together.within-page="1">
	<tbody>
		<tr>
			<td>Stage</td>
			<td>Description</td>
			<td>Additional notes</td>
			<td>References</td>
		</tr>
		<tr>
			<td>Simple Discrimination (SD)</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Compound Discrimination (CD)</td>
			<td>Stimuli vary in two perceptual dimensions, such as color and shape for visual stimuli in the human task, or between texture and odor stimuli for rodents</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Reversal learning (CDRe &#8211; IDSRe &#8211; IDS2Re &#8211; EDSRe)</td>
			<td>Two exemplars within a perceptual dimension have their reinforcement contingencies reversed so that what was previously correct is then incorrect and vice versa)</td>
			<td>In serial reversal learning, performance improves with consecutive within-set reversals. Thus, reversal stages (i.e., CDRe, IDSRe, IDS2Re) not only assess function of different cortical areas, but also serve 1) to form the cognitive- attentional set challenged by the EDS stage, and 2) to prevent superstitious conditioning to unintended aspects of the stimulus</td>
			<td>- Lesions of the orbitofrontal cortex in mice (Bissonette et al., 2008) and monkyes (Dias et al., 1996) impaired Reversal learning 
			- fMRI during performance on the Reversal learning showed activation of the orbitofrontal cortex (Hampshire and Owen, 2006)</td>
		</tr>
		<tr>
			<td>Intradimensional shift (IDS &#8211; IDS2)</td>
			<td>Novel exemplars are introduced, but the same dimension is reinforced</td>
			<td>IDS stages serve as a crucial internal control (i.e., EDS should be more difficult than IDS), and also contribute to form the cognitive-attentional set</td>
			<td>Dopamine depletion in the PFC impaired attentional set formation (Robbins and Roberts, 2007). 6-OHDA lesioned monkeys did not show the classical reduction the reduction in errors from the first (IDS1) to the last (IDS5) discrimination, which should&#160; reflect acquisition of an attentional set&#160;</td>
		</tr>
		<tr>
			<td rowspan="2">Extradimensional shift (EDS)</td>
			<td>&#8216;stuck-in-set&#8217; protocol: previously irrelevant stimulus dimension is replaced by a new stimulus dimension which immediately becomes relevant</td>
			<td>failure to shift to the new relevant dimension cannot be attributed to any prior learning about this dimension since it had not been previously experienced. Failure, therefore, reflects perseveration to the previously relevant dimension</td>
			<td>- Lesions of the mPFC have been show to impair EDS in mice (Bissonette et al., 2008), and mokeys (Dias et al., 1996) 
			- Frontal lobe patients are impaired in the stuck-in-set &#39;perseveration&#39; condition but not in the &#8216;two dimension&#39; condition (Owen et al., 1993) 
			- Dopamine in the mPFC modulated EDS performance in mice (Papaleo et al., 2008; Scheggia et al., 2014) and rats (Tunbridge et al., 2004)</td>
		</tr>
		<tr>
			<td>&#8216;two dimensions&#8217; protocol: the previously irrelevant dimension is reinforced</td>
			<td>an apparent failure to shift attentional set may arise when a subject is able to shift attention away from a previously relevant dimension (when it becomes irrelevant) but is, nevertheless, unable to refocus attention on the newly relevant dimension</td>
			<td>- Lesion of the mPFC in rats (Birrell and Brown, 2000) impaired EDS shift 
			- fMRI during performance on the EDS has been shown activation of the ventro-lateral PFC (Hampshire and Owen, 2006)&#160;</td>
		</tr>
	</tbody>
</table>
Table 2: Stages of the ID/ED Operon task. Description of the stages of the task, including references to lesion and pharmacological studies addressing the role of brain areas involved in the different constructs tested during the task.

Watch this Scientific Journal Video about An Operant Intra-/Extra-dimensional Set-shift Task for Mice at JoVE.com

An Operant Intra-/Extra-dimensional Set-shift Task for Mice

Attentional set-shifting cognitive abnormalities are a core feature of many psychiatric diseases. Here, we present the development of a novel automatic system for the effective study of attentional set-shifting abilities, executive functions and other cognitive abilities in mice with high translational validity to human studies.

Alterations in executive control and cognitive flexibility, such as attentional set-shifting abilities, are core features of several neuropsychiatric ...

an-operant-intra-extra-dimensional-set-shift-task-for-mice

Universidad San Sebastian

Research

JoVE Journal

Behavior

12.1K Views.  Istituto Italiano di Tecnologia. Attentional set-shifting cognitive abnormalities are a core feature of many psychiatric diseases. Here, we present the development of a novel automatic system for the effective study of attentional set-shifting abilities, executive functions and other cognitive abilities in mice with high translational validity to human studies.

Video: An Operant Intra-/Extra-dimensional Set-shift Task for Mice

The Attentional Set Shifting Task: A Measure of Cognitive Flexibility in Mice

Cognitive impairment, particularly involving dysfunction of circuitry within the prefrontal cortex (PFC), represents a core feature of many neuropsychiatric and neurodevelopmental disorders, including depression, post-traumatic stress disorder, schizophrenia and autism spectrum disorder. Deficits in cognitive function also represent the most difficult symptom domain&#160;to successfully treat, as serotonin reuptake inhibitors and tricyclic antidepressants have only modest effects. Functional neuroimaging studies and postmortem analysis of human brain tissue implicate the PFC as being a primary region of dysregulation in patients with these disorders. However, preclinical behavioral assays used to assess these deficits in mouse models which can be readily manipulated genetically and could provide the basis for studies of new treatment avenues have been underutilized. Here we describe the adaptation of a behavioral assay, the attentional set shifting task (AST), to be performed in mice to assess prefrontal cortex mediated cognitive deficits. The neural circuits underlying behavior during the AST are highly conserved across humans, nonhuman primates and rodents, providing excellent face, construct and predictive validity.

The goal of this protocol is to perform a behavioral assay such as the attentional set shifting task (AST) to assess prefrontal cortex-mediated cognitive flexibility in mice.

Cognitive impairment, particularly involving dysfunction of circuitry within the prefrontal cortex (PFC), represents a core feature of many ...

Operant Procedures for Assessing Behavioral Flexibility in Rats

Executive functions consist of multiple high-level cognitive processes that drive rule generation and behavioral selection. An emergent property of these processes is the ability to adjust behavior in response to changes in one&#8217;s environment (i.e., behavioral flexibility). These processes are essential to normal human behavior, and may be disrupted in diverse neuropsychiatric conditions, including schizophrenia, alcoholism, depression, stroke, and Alzheimer&#8217;s disease. Understanding of the neurobiology of executive functions has been greatly advanced by the availability of animal tasks for assessing discrete components of behavioral flexibility, particularly strategy shifting and reversal learning. While several types of tasks have been developed, most are non-automated, labor intensive, and allow testing of only one animal at a time. The recent development of automated, operant-based tasks for assessing behavioral flexibility streamlines testing, standardizes stimulus presentation and data recording, and dramatically improves throughput. Here, we describe automated strategy shifting and reversal tasks, using operant chambers controlled by custom written software programs. Using these tasks, we have shown that the medial prefrontal cortex governs strategy shifting but not reversal learning in the rat, similar to the dissociation observed in humans. Moreover, animals with a neonatal hippocampal lesion, a neurodevelopmental model of schizophrenia, are selectively impaired on the strategy shifting task but not the reversal task. The strategy shifting task also allows the identification of separate types of performance errors, each of which is attributable to distinct neural substrates. The availability of these automated tasks, and the evidence supporting the dissociable contributions of separate prefrontal areas, makes them particularly well-suited assays for the investigation of basic neurobiological processes as well as drug discovery and screening in disease models.

The ability to assess executive functions such as behavioral flexibility in rats is useful for investigating the neurobiology of cognition in both intact animals and disease models. Here we describe automated tasks for assessing strategy shifting and reversal learning, which are particularly sensitive to disruptions in prefrontal cortical networks.

Executive functions consist of multiple high-level cognitive processes that drive rule generation and behavioral selection. An emergent property of these ...

The Double-H Maze: A Robust Behavioral Test for Learning and Memory in Rodents

Spatial cognition research in rodents typically employs the use of maze tasks, whose attributes vary from one maze to the next. These tasks vary by their behavioral flexibility and required memory duration, the number of goals and pathways, and also the overall task complexity. A confounding feature in many of these tasks is the lack of control over the strategy employed by the rodents to reach the goal, e.g., allocentric (declarative-like) or egocentric (procedural) based strategies. The double-H maze is a novel water-escape memory task that addresses this issue, by allowing the experimenter to direct the type of strategy learned during the training period. The double-H maze is a transparent device, which consists of a central alleyway with three arms protruding on both sides, along with an escape platform submerged at the extremity of one of these arms.
Rats can be trained using an allocentric strategy by alternating the start position in the maze in an unpredictable manner (see protocol 1; &#167;4.7), thus requiring them to learn the location of the platform based on the available allothetic cues. Alternatively, an egocentric learning strategy (protocol 2; &#167;4.8) can be employed by releasing the rats from the same position during each trial, until they learn the procedural pattern required to reach the goal. This task has been proven to allow for the formation of stable memory traces.
Memory can be probed following the training period in a misleading probe trial, in which the starting position for the rats alternates. Following an egocentric learning paradigm, rats typically resort to an allocentric-based strategy, but only when their initial view on the extra-maze cues differs markedly from their original position. This task is ideally suited to explore the effects of drugs/perturbations on allocentric/egocentric memory performance, as well as the interactions between these two memory systems.

The goal of this protocol is to investigate spatial cognition in rodents. The double-H water maze is a novel test, which is particularly useful to elucidate the different components of learning, consolidation and memory, as well as the interplay of memory systems.

Spatial cognition research in rodents typically employs the use of maze tasks, whose attributes vary from one maze to the next. These tasks vary by their ...

New Variations for Strategy Set-shifting in the Rat

Behavioral flexibility is crucial for survival in changing environments. Broadly defined, behavioral flexibility requires a shift of behavioral strategy based on a change in governing rules. We describe a strategy set-shifting task that requires an attentional shift from one stimulus dimension to another. The paradigm is often used for testing cognitive flexibility in primates. However, the rodent version has not been as extensively developed. We have recently extended an established set-shifting task in the rat1 by requiring attention to different stimuli according to context. All the experimental conditions required animals to choose either a left or right lever. Initially, all animals had to choose on the basis of the location of the lever. Subsequently, a change in the rule occurred, which required a shift in set from location-based rule to a rule in which the correct lever was indicated by a light cue. We compared performance on three different versions of the task, in which the light stimulus was either novel, previously relevant, or previously irrelevant. We found that specific neurochemical lesions selectively impaired the ability to make particular types of set shift as measured by the performance on the different versions of the task.

Set-shifting, a form of behavioral flexibility, requires an attentional shift from one stimulus dimension to another. We extended an established rodent set-shifting task1 by requiring attention to different stimuli according to context. The task was combined with specific lesions to identify neuron subtypes underlying a successful shift.

Behavioral flexibility is crucial for survival in changing environments. Broadly defined, behavioral flexibility requires a shift of behavioral strategy ...

T-maze Forced Alternation and Left-right Discrimination Tasks for Assessing Working and Reference Memory in Mice

Forced alternation and left-right discrimination tasks using the T-maze have been widely used to assess working and reference memory, respectively, in rodents. In our laboratory, we evaluated the two types of memory in more than 30 strains of genetically engineered mice using the automated version of this apparatus. Here, we present the modified T-maze apparatus operated by a computer with a video-tracking system and our protocols in a movie format. The T-maze apparatus consists of runways partitioned off by sliding doors that can automatically open downward, each with a start box, a T-shaped alley, two boxes with automatic pellet dispensers at one side of the box, and two L-shaped alleys. Each L-shaped alley is connected to the start box so that mice can return to the start box, which excludes the effects of experimenter handling on mouse behavior. This apparatus also has an advantage that in vivo microdialysis, in vivo electrophysiology, and optogenetics techniques can be performed during T-maze performance because the doors are designed to go down into the floor. In this movie article, we describe T-maze tasks using the automated apparatus and the T-maze performance of &alpha;-CaMKII+/- mice, which are reported to show working memory deficits in the eight-arm radial maze task. Our data indicated that &alpha;-CaMKII+/- mice showed a working memory deficit, but no impairment of reference memory, and are consistent with previous findings using the eight-arm radial maze task, which supports the validity of our protocol. In addition, our data indicate that mutants tended to exhibit reversal learning deficits, suggesting that &alpha;-CaMKII deficiency causes reduced behavioral flexibility. Thus, the T-maze test using the modified automatic apparatus is useful for assessing working and reference memory and behavioral flexibility in mice.

This article presents the protocol of T-maze tests using a modified automated apparatus for assessing the learning and memory functions in mice.

Forced alternation and left-right discrimination tasks using the T-maze have been widely used to assess working and reference memory, respectively, in ...

Neuroscience

A Behavioral Assay for Investigating the Role of Spatial Memory During Instinctive Defense in Mice

Evolution has selected a repertoire of defensive behaviors that are essential for survival across all animal species. These behaviors are often stereotyped actions elicited in response to innately aversive sensory stimuli, but their success requires enough flexibility for adapting to different spatial environments, which can change rapidly. Here, we describe a behavioral assay to evaluate the influence of learned spatial knowledge on defensive behaviors in mice. We have adapted the widely used Barnes maze spatial memory assay to investigate how mice navigate to a shelter during escape responses to innately aversive sensory stimuli in a novel environment, and how they adapt to acute changes in the environment. This new assay is an ethological paradigm that does not require training and exploits the natural exploration patterns and navigation strategies in mice. We propose that the set of protocols described here are a powerful means of studying goal-directed behaviors and stimulus-triggered navigation, which should be of interest to both the fields of instinctive behaviors and spatial memory.

This protocol describes a behavioral assay, based on the Barnes maze test, to study how instinctive defensive actions are modified by the knowledge of spatial environment.

Evolution has selected a repertoire of defensive behaviors that are essential for survival across all animal species. These behaviors are often ...

Novel Object Recognition and Object Location Behavioral Testing in Mice on a Budget

Ethologically relevant behavioral testing is a critical component of any study that uses mouse models to study the cognitive effects of various physiological or pathological changes. The object location task (OLT) and the novel object recognition task (NORT) are two effective behavioral tasks commonly used to reveal the function and relative health of specific brain regions involved in memory. While both of these tests exploit the inherent preference of mice for the novelty to reveal memory for previously encountered objects, the OLT primarily evaluates spatial learning, which relies heavily on hippocampal activity. The NORT, in contrast, evaluates non-spatial learning of object identity, which relies on multiple brain regions. Both tasks require an open-field-testing arena, objects with equivalent intrinsic value to mice, appropriate environmental cues, and video recording equipment and the software. Commercially available systems, while convenient, can be costly. This manuscript details a simple, cost-effective method for building the arenas and setting up the equipment necessary to perform the OLT and NORT. Furthermore, the manuscript describes an efficient testing protocol that incorporates both OLT and NORT and provides typical methods for data acquisition and analysis, as well as representative results. Successful completion of these tests can provide valuable insight into the memory function of various mouse model systems and appraise the underlying neural regions that support these functions.

Here we provide a protocol which includes comprehensive instructions for the economical establishment of murine object location and novel object recognition behavioral testing, including the design, cost, and construction of required equipment as well as execution of behavioral testing, data collection, and analysis.

Ethologically relevant behavioral testing is a critical component of any study that uses mouse models to study the cognitive effects of various ...

Two Different Real-Time Place Preference Paradigms Using Optogenetics within the Ventral Tegmental Area of the Mouse

Understanding how neuronal activation leads to specific behavioral output is fundamental for modern neuroscience. Combining optogenetics in rodents with behavioral testing in validated paradigms allows the measurement of behavioral consequences upon stimulation of distinct neurons in real-time with high spatial and temporal selectivity, and thus the establishment of causal relationships between neuronal activation and behavior. Here, we describe a step-by-step protocol for a real-time place preference (RT-PP) paradigm, a modified version of the classical conditioned place preference (CPP) test. The RT-PP is performed in a three-compartment apparatus and can be utilized to answer if optogenetic stimulation of a specific neuronal population is rewarding or aversive. We also describe an alternative version of the RT-PP protocol, the so-called neutral compartment preference (NCP) protocol, which can be used to confirm aversion. The two approaches are based on extensions of classical methodology originating from behavioral pharmacology and recent implementation of optogenetics within the neuroscience field. Apart from measuring place preference in real time, these setups can also give information regarding conditioned behavior. We provide easy-to-follow step-by-step protocols alongside examples of our own data and discuss important aspects to consider when applying these types of experiments.

Here we present two easy-to-follow step-by-step protocols for place preference paradigms using optogenetics in mice. Using these two different setups, preference and avoidance behaviors can be solidly assessed within the same apparatus with high spatial and temporal selectivity, and in a straightforward manner.

Understanding how neuronal activation leads to specific behavioral output is fundamental for modern neuroscience. Combining optogenetics in rodents with ...

Optogenetic Manipulation of Neuronal Activity to Modulate Behavior in Freely Moving Mice

Optogenetic modulation of neuronal circuits in freely moving mice affects acute and long-term behavior. This method is able to perform manipulations of single neurons and region-specific transmitter release, up to whole neuronal circuitries in the central nervous system, and allows the direct measurement of behavioral outcomes. Neurons express optogenetic tools via an injection of viral vectors carrying the DNA of choice, such as Channelrhodopsin2 (ChR2). Light is brought into specific brain regions via chronic optical implants that terminate directly above the target region. After two weeks of recovery and proper tool-expression, mice can be repeatedly used for behavioral tests with optogenetic stimulation of the neurons of interest.
Optogenetic modulation has a high temporal and spatial resolution that can be accomplished with high cell specificity, compared to the commonly used methods such as chemical or electrical stimulation. The light does not harm neuronal tissue and can therefore be used for long-term experiments as well as for multiple behavioral experiments in one mouse. The possibilities of optogenetic tools are nearly unlimited and enable the activation or silencing of whole neurons, or even the manipulation of a specific receptor type by light.
The results of such behavioral experiments with integrated optogenetic stimulation directly visualizes changes in behavior caused by the manipulation. The behavior of the same animal without light stimulation as a baseline is a good control for induced changes. This allows a detailed overview of neuronal types or neurotransmitter systems involved in specific behaviors, such as anxiety. The plasticity of neuronal networks can also be investigated in great detail through long-term stimulation or behavioral observations after optical stimulation. Optogenetics will help to enlighten neuronal signaling in several kinds of neurological diseases.

With optogenetic manipulation of specific neuronal populations or brain regions, behavior can be modified with high temporal and spatial resolution in freely moving animals. By using different optogenetic tools in combination with chronically implanted optical fibers, a variety of neuronal modulations and behavioral testing can be performed.

Optogenetic modulation of neuronal circuits in freely moving mice affects acute and long-term behavior. This method is able to perform manipulations of ...

A Behavioral Task Modeling 'Everyday Memory' in an Event Arena to Foster Allocentric Representations for Rodents

The event arena provides an optimal platform to investigate learning and memory. The appetitive everyday memory task described in this paper provides a robust protocol for the investigation of episodic and spatial memory in rodents, which specifically fosters allocentric memory representation. Rats are trained to find and dig for food during the encoding phase and, after a time delay, rats are given a choice to find the reward food pellet in the correct location. There are two key elements that promote the use of an allocentric strategy in this protocol: 1) rats start from different start locations within and between sessions, 2) a stable home-base is deployed where rats have to carry their food to eat. By means of these modifications, we effectively encourage the rodents to use allocentric spatial representations to perform the task. In addition, the task provides a good paradigm for within-subject experimental design and allows experimenters to manipulate different conditions to reduce variability. Used in conjunction with behavioral and physiological techniques, the resulting rodent model provides an effective test-bed for future research into memory formation and retention.

The goal of this optimized 'everyday memory' protocol in an event arena was to employ a stable home-base that encourages the use of allocentric spatial representations. This animal model provides an effective test-bed for future research into the formation and retention of event memories using behavioral and physiological techniques.

The event arena provides an optimal platform to investigate learning and memory. The appetitive everyday memory task described in this paper provides a ...