Department of Cognition, Development and Educational Psychology
Faculty of Psychology
& Institute of Neuroscience
Universitat de Barcelona
I completed my BA, MA and PhD degrees in Madrid (at the Autonomous University of Madrid) and I was a Research Fellow at the University of Birmingham (UK) on two occasions and a Visiting Fellow at the University of Cambridge (UK) several times before becoming a Lecturer and then a Professor at the University of Barcelona (Catalunya, Spain).
I have been the President of the “Spanish Society for Comparative Psychology” -SEPC in Spanish- in 2003 and in 2016, also the President and then vice-President of the “Spanish Society of Experimental Psychology” -SEPEX in Spanish- between 2004 and 2008. I have also served as Program Chair for Division 6 (Behavioral Neuroscience and Comparative Psychology) of the American Psychological Association (APA) in the 2012 meeting.
Most of my work is about spatial cognition and associative learning. Specifically, I am interested in studying the conditions, basic effects and mechanisms responsible for the acquisition of knowledge about spatial location in rats and also in humans.
My research for the past 30 years has been mainly in collaboration with Professor N.J. Mackintosh†, from Cambridge University (UK), as well as with other colleagues and students from the Universitat de Barcelona. This joint research developed into a research group, which I co-ordinate, whose name is “Learning and Cognition: A comparative approach” (http://www.gracec.info).
The main results of our work have been the demonstration that the basic phenomena of Pavlovian and instrumental conditioning (like blocking, overshadowing, latent inhibition, perceptual learning, changes in attention to relevant and irrelevant cues ...) also appear when working with strictly spatial tasks (both in the elevated maze and in the Morris water maze).
In the last decade, we have also shown that male and female rats can use different strategies to solve navigation tasks (a finding often called “qualitative sex differences”), being crucial the distinction between what they learn and what they prefer (i.e., learning vs. performance). In this line of research we have also measured age effects in our animals. Specifically, a change in the behaviour of female rats as they grow older.
At present I continue to investigate these issues, fundamentally qualitative sex differences in a navigation task while acquiring knowledge based on geometrical and non-geometrical information simultaneously. Standard associative theories can explain most of our results.
While navigating, we become familiar with an environment and acquire knowledge about it, thereby extracting information from it and storing this information in our memory so that we can recall it later for a variety of purposes (Ekstrom, Spiers, Bohbot, & Rosenbaum, 2018). Examples concerning rodents and humans will be presented since there is an important parallelism between them when dealing with spatial tasks. However, most of the examples will focus on how males and females differ when solving these tasks ?on something that has recently been referred to as ?qualitative? sex differences?, thus counteracting the unjustified practice of ignoring females for so many years in psychological and biomedical research (for a review see Beery & Zucker, 2011). To understand the sexually-dimorphic spatial abilities between males and females ?which are so influenced by sex hormones? a specific explanation, the range size hypothesis, will be discussed. For different reasons, this hypothesis applies to both, rodents and humans. A brief description of the role of the hippocampus while navigating and of the evolutionary origins of the human species is also presented. For navigational strategies and mechanisms used by rats see Rodentia Navigation in the present issue (for the same in humans, see Ekstrom et al., 2018).
In three experiments rats of different age were trained in a circular pool to find a hidden platform whose location was defined in terms of a single a landmark, a cylinder outside the pool. Following training two main components of the landmark, its shape and pattern, were tested individually. Experiment 1 was with adolescent and adult rats (1a, males; 1b, females). Adult rats always learned faster than adolescent animals. On test trials interesting tendencies were found, mainly one favouring males on the shape test trial and another favouring females on the pattern test trial. Then Experiment 2 was conducted only with adolescent rats and males and females did not differ when learning the task. However on test trials, males learned more about the landmark shape component than about the landmark pattern component, while females learned equally about the two components of the landmark. Finally, Experiment 3 was conducted only with adult rats and again males and females did not differ when learning the task. However on test trials, males learned equally about the two components of the landmark (shape and pattern), although females learned more about the landmark pattern component than about the landmark shape component. This set of experiments supports the claim that male and female rats can learn rather different things about a landmark that signals the location of the platform, age being a critical variable.Download
There is abundant research (both in rodents and in humans) showing that males and females often use different types of information in spatial navigation. Males prefer geometry as a source of information, whereas females tend to focus on landmarks (which are often near to a goal objects). However, when considering the role of the hippocampus, the research focuses primarily on males only. In the present study, based on Rodríguez, Torres, Mackintosh, and Chamizo?s (2010, Experiment 2) navigation protocol, we conducted two experiments, one with males and another with females, in order to tentatively evaluate the role of the dorsal hippocampus in the acquisition of two tasks: one based on landmark learning and the alternate one on local pool-geometry learning. Both when landmark learning and when geometry learning, Sham male rats learned significantly faster than Lesion male animals. This was not the case with female rats whith geometry learning. These results suggest that the dorsal hippocampus could play an important role in males only.Download
The present volume is a homage to Professor N. J. Mackintosh (1935-2015), an outstanding academic and a dear friend and colleague to many of the participants, as a final tribute after being awarded the Gold Medal by the University of Barcelona (November 2015). Although the topics of the chapters in this book have been freely chosen by the authors (Geoffrey Hall, Anthony Dickinson, John M. Pearce, Ian McLaren, Paula J. Durlach, Irina Baetu to mention a few), as well as the type of contribution (either an empirical paper, a review, or an application), they concentrate on issues that are crucial to the understanding of the basic principles of attention and associative learning (both Pavlovian and instrumental), in humans and also in other animals. In other words, to unravel the nature of conditioning, with a special emphasis on perceptual learning. The final chapter, by Gabriel Ruiz, addresses the importance of the contribution by Professor Mackintosh to the renaissance of animal psychology in Spain, where the Spanish Society for Comparative Psychology (SEPC in Spanish) played a relevant roleView publication Download
The effects of early environmental enrichment (EE) and voluntary wheel running on the preference for using a landmark or pool geometry when solving a simple spatial task in adult male and female rats were assessed. After weaning, rats were housed in same-sex pairs in enriched or standard cages (EE and control groups) for two and a half months. Then the rats were trained in a triangular-shaped pool to find a hidden platform whose location was defined in terms of these two sources of information, a landmark outside the pool and a particular corner of the pool. As expected, enriched rats reached the platform faster than control animals, and males and females did not differ. Enriched rats also performed better on subsequent test trials without the platform with the cues individually presented (either pool geometry or landmark). However, on a preference test without the platform, a clear sex difference was found: Females spent more time in an area of the pool that corresponded to the landmark, whereas males spent more time in the distinctive corner of the pool. The present EE protocol did not alter females preference for the landmark cue. The results agree with the claim that environmental enrichment is a consequence of a reduced anxiety response (measured by thigmotaxis) during cognitive testing. A possible implication of ancestral selection pressures is discussedView publication Download
In Experiment 1, two groups of female rats were trained in a triangular pool to find a hidden platform whose location was defined in terms of a single a landmark, a cylinder outside the pool. For one group, the landmark had only a single pattern (i.e., it looked the same when approached from any direction), while for the other, the landmark contained four different patterns (i.e., it looked different when approached from different directions). The first group learned to swim to the platform more rapidly than the second. Experiment 2 confirmed this difference when female rats were trained in a circular pool but found that male rats learned equally rapidly (and as rapidly as females trained with the single-pattern landmark) with both landmarks. This second finding was confirmed in Experiment 3. Finally, in Experiment 4a and 4b, male and female rats were trained either with the same, single-pattern landmark on all trials or with a different landmark each day. Males learned equally rapidly (and as rapidly as females trained with the unchanged landmark) whether the landmark changed or not. We conclude that male and female rats learn rather different things about the landmark that signals the location of the platformView publication
The present set of experiments evaluated the possibility that the hormonal changes that appear at the onset of puberty might influence the strategies used by female rats to solve a spatial navigation task. In each experiment, rats were trained in a triangular shaped pool to find a hidden platform which maintained a constant relationship with two sources of information, one individual landmark and one corner of the pool with a distinctive geometry. Then, three test trials were conducted without the platform in counterbalanced order. In one, both the geometry and the landmark were simultaneously presented, although in different spatial positions, in order to measure the rats preferences. In the remaining test trials what the rats had learned about the two sources of information was measured by presenting them individually. Experiment 1, with 60-day old rats, revealed a clear sex difference, thus replicating a previous finding (Rodríguez et al., 2010): females spent more time in an area of the pool that corresponded to the landmark, whereas males spent more time in the distinctive corner of the pool even though the remaining tests revealed that both sexes had learned about the two sources of information. In Experiment 2, 30-day old female rats, unlike adults, preferred to solve the task using the geometry information rather than the landmark (although juvenile males behaved in exactly the same way as adults). Experiment 3 directly compared the performance of 90- and 30-day old females and found that while the adult females preferred to solve the task using the landmark, the reverse was true in juvenile females. Experiment 4 compared ovariectomized and sham operated females and found that while sham operated females preferred to solve the task using the landmark, the reverse was true in ovariectomized females. Finally, Experiment 5 directly compared adult males and females, juvenile males and females, and ovariectomized females and found that adult males, juvenile males and females, and ovariectomized females did not differ among them in their preferred cue, but they all differed from adult femalesView publication
When they are trained in a Morris water maze to find a hidden platform, whose location is defined by a number of equally spaced visual landmarks round the circumference of the pool, rats are equally able to find the platform when tested with any two of the landmarks (Prados, & Trobalon, 1998; Rodrigo, Chamizo, McLaren, & Mackintosh, 1997). This suggests that none of the landmarks was completely overshadowed by any of the others. In Experiment 1 one pair of groups was trained with four equally salient visual landmarks spaced at equal intervals around the edge of the pool, while a second pair was trained with two landmarks only, either relatively close to or far from the hidden platform. After extensive training, both male and female rats showed a reciprocal overshadowing effect: on a test with two landmarks only (either close to or far from the platform), rats trained with four landmarks spent less time in the platform quadrant than those trained with only two. Experiment 2 showed that animals trained with two landmarks and then tested with four also performed worse on test than those trained and tested with two landmarks only. This suggests that generalization decrement, rather than associative competition, provides a sufficient explanation for the overshadowing observed in Experiment 1. Experiment 3 provided a within-experiment replication of the results of Experiments 1 and 2. Finally, Experiment 4 showed that rats trained with a configuration of two landmarks learn their identityView publication
Rats were trained in a triangular-shaped pool to find a hidden platform, whose location was defined in terms of two sources of information, a landmark outside the pool and a particular corner of the pool. Subsequent test trials without the platform pitted these two sources of information against one another. This test revealed a clear sex difference. Females spent more time in an area of the pool that corresponded to the landmark, whereas males spent more time in the distinctive corner of the pool even though further tests revealed that both sexes had learned about the two sources of information by presenting cues individually. The results agree with the claim that males and females use different types of information in spatial navigation. (PsycINFO Database Record (c) 2016 APA, all rights reserved)View publication
In Experiments 1 and 2, rats were trained in a Morris pool to find a hidden platform located some distance away from a single landmark. Males learned to swim to the platform faster than females, but on test trials without the platform, males, unlike females, spent less time in the platform quadrant of the pool in the second half of each test trial than in the first. They also showed greater persistence in searching in the platform quadrant over a series of extinction trials. In Experiments 3a and 3b, the problem was made easier by locating the platform closer to the solitary landmark. Now males and females learned to swim to the platform equally rapidly, and both stopped searching in the platform quadrant in the second half of each test trial. Experiment 4 ruled out the possibility that males´ shorter latencies to find the platform in Experiment 2 were due to their swimming faster than femalesView publication
Using a variation on the standard procedure of conditioned inhibition (Trials A+ and AX?), rats (Rattus norvegicus) in a circular pool were trained to find a hidden platform that was located in a specific spatial position in relation to 2 individual landmarks (Trials A ? platform and B ? platform; Experiments 1a and 1b) and to 2 configurations of landmarks (Trials ABC ? platform and FGH ? platform; Experiment 2a). The rats also underwent inhibitory trials (Experiment 1: Trials AZ ? no platform; Experiment 2a: Trials CDE ? no platform) interspersed with these excitatory trials. In both experiments, subsequent test trials without the platform showed both a summation effect and retardation of excitatory conditioning, and in Experiment 2a rats learned to avoid the CDE quadrant over the course of the experiment. Two further experiments established that these results could not be attributed to any difference in salience between the conditioned inhibitors and the control stimuli. All these results contribute to the growing body of evidence consistent with the idea that there is a general mechanism of learning that is associative in nature. (PsycINFO Database Record (c) 2016 APA, all rights reserved)View publication