Spatial memory deficits in a virtual radial arm maze in amnesic participants with hippocampal damage.

Extensive research with laboratory animals indicates that the hippocampus is crucial for the formation and use of spatial memory. Hippocampal lesions in rodents impair spatial memory on radial arm maze tasks. It is unknown whether amnesic patients with hippocampal damage would exhibit similar impairments on a virtual version of a radial arm maze. To evaluate the importance of the hippocampus in spatial learning and memory, we tested amnesic participants with hippocampal damage in a virtual radial arm maze environment. The virtual radial arm maze required participants to learn and remember 4 rewarded arms of 8 total arms. Spatial learning and memory were assessed using the participants' ability to use salient distal cues in the virtual room to remember the 4 rewarded arms. Amnesic participants' latencies were longer and distance traveled was greater to the rewarded arms compared with nonamnesic participants. Amnesic participants made more errors than nonamnesic participants by either entering nonrewarded arms or by revisiting previously entered arms. These data are analogous to previous animal research. Overall, the human hippocampus is necessary for spatial memory and navigation in a virtual radial arm maze task. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spatial memory in dogs (Canis familiaris) on a radial maze.

Working spatial memory in dogs (Canis familiaris) was tested in Experiments 1 and 2 on an 8-arm radial maze. When dogs chose freely among all 8 arms containing food in Experiment 1, they learned to enter all 8 arms with progressively fewer arm visits over trials. In Experiment 2, 2 groups of dogs were forced to visit 4 randomly chosen arms on the maze and then tested for memory of these arm visits using a win-shift rule for 1 group and a win-stay rule for the other group. Dogs performed better with the win-shift rule than with the win-stay rule. In Experiment 3, reference memory was investigated by using a 4-arm maze on which 0, 1, 3, and 6 pieces of food were consistently placed on different arms. Dogs learned to visit the arms with the larger amounts before the arms with the smaller amounts. Dogs’ memory capacity in these studies was found to be surprisingly low. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Does shape matter? Theoretical comment on Jones, Pearce, Davies, Good, and McGregor (2007).

An influential view in the field of spatial cognition is that an obligatory geometric module constrains spatial learning and memory. In this issue, P. M. Jones, J. M. Pearce, V. J. Davies, M. A. Good, and A. McGregor (2007; see record 2007-18058-012) showed that learning based on the geometry, or shape, of the environment requires the hippocampus. To place this work in context, the author of the present article considers the evidence for and against a geometric module for rat spatial learning, outlines the influence of geometry on neurons that encode spatial information, and attempts to relate spatial behavior to neuronal representations of direction and location. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spatial learning and memory in the tortoise (Geochelone carbonaria).

A single tortoise (Geochelone carbonaria) was trained in an eight-arm radial maze, with the apparatus and general procedures modeled on those used to demonstrate spatial learning in rats. The tortoise learned to perform reliably above chance, preferentially choosing baited arms, rather than returning to arms previously visited on a trial. Test sessions that examined control by olfactory cues revealed that they did not affect performance. No systematic, stereotyped response patterns were evident. In spite of differences in brain structure, the tortoise showed spatial learning abilities comparable to those observed in mammals. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spatial memory for food hidden by rats (Rattus norvegicus) on the radial maze: Studies of memory for where, what, and when.

Rats (Rattus norvegicus) were allowed to hide food items on an 8-arm radial maze by carrying the items from the center to boxes at the end of each arm. Retrieval tests given after rats had hidden 4 items showed that they selectively returned to the maze arms where food had been hidden (Experiments 1 and 2). When rats were allowed to hide pieces of cheese (preferred food) and pretzels (less preferred food) on different arms, they both hid and retrieved cheese before pretzels (Experiments 2-5). In Experiment 6, rats chose between arms where cheese and pretzels were hidden, with cheese degraded at one delay interval but not the other. Together, these experiments indicate memory for what and where but not when. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effects of NMDA lesions centered on the postrhinal cortex on spatial memory tasks in the rat.

Rats with bilateral N-methyl-D-aspartate lesions centered on the postrhinal cortex (POR) and sham lesions were tested in a series of spatial memory tasks. The POR-lesioned rats were significantly impaired compared with sham rats in the reference memory version of both the water maze and radial arm maze tasks and in the standard radial arm maze working memory task. The POR-lesioned rats displayed a delay-independent impairment in the working memory versions of the water maze and in a delayed nonmatching-to-place (DNMP) version of the radial arm maze task. The POR-lesioned rats were also impaired in a DNMP procedure conducted in the T-maze. These findings indicate that the POR has a delay-independent role in the processing of spatial information. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Adaptive priorities in brain development: Theoretical comment on Pravosudov et al. (2005).

V. V. Pravosudov, P. Lavenex, and A. Omanska (2005) (see record 2005-13804-022) reported that undernutrition in the first few weeks' posthatching leads to lower mean hippocampus volumes in adult Western scrub jays (Aphelocoma californica) and to poorer performance on spatial memory tasks. Together with prior work on the effects of poor nutrition on the development of the song system in songbirds, these results fit reasonably well with the view that natural selection determines priorities for investment in the development of neural structures. What seems somewhat anomalous under this view is that undernutrition did not affect the development of color association abilities in scrub jays. This work sets the stage for future comparative research on adaptive priorities in the development of brain and behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Performance on spatial working memory tasks after dorsal or ventral hippocampal lesions and adjacent damage to the subiculum.

Rats with excitotoxic lesions of the dorsal or ventral hippocampus and control rats were trained on 2 spatial working memory tasks: the standard version of the radial maze with 8 baited arms and the nonmatching-to-place procedure in the T maze. Dorsal lesions produced deficits in both tasks, whereas ventral lesions did not affect learning in either of them. A volumetric analysis of subicular damage showed that dorsal hippocampal lesions caused a deficit in the nonmatching-to-place only when accompanied by damage to the dorsal subiculum; on the other hand, lesions to the dorsal hippocampus impaired performance in the radial-arm maze regardless of the extent of subicular damage. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Place and response learning in human virtual navigation: Behavioral measures and gender differences.

Two experiments examined the use of place and response strategies by humans navigating virtual multiple T mazes. In Experiment 1, probe trials revealed that participants commonly used place and response strategies, and place strategies were more frequent early in training, whereas response strategies were more frequent late in training. Compared with women, men learned the correct path through the maze more quickly and developed a more stable route through the maze. In Experiment 2, participants were trained to locate 2 targets. One target required participants to use either a place or response strategy, whereas the other target could be found using either strategy. Accuracy improved faster for place training compared with response training, and women outperformed men in both groups. Probe trials testing transfer of the imposed strategy to the other target found faster transfer for place training than for response training and that women demonstrated faster transfer than men. Accuracy on probe trials was correlated with poor route stability in the place-trained group and with good route stability in the response-trained group, indicating that navigation strategy use may be related to measures of improvement in performance on normal trials. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The influence of hippocampal lesions on the discrimination of structure and on spatial memory in pigeons (Columba livia).

Pigeons (Columba livia) were trained with a spatial structural discrimination, which was based on the spatial relationship among the components of a pattern, and a feature-binding structural discrimination, which was based on how different visual features within a pattern were combined. Neither discrimination was impaired by damage to the hippocampus and area parahippocampalis. The lesions impaired performance on a spatial working memory and a spatial reference memory task in open field. The results indicate an intact hippocampus is not essential for the solution of structural discriminations in pigeons and the hippocampus is important for processing some types of spatial information--that used in navigation, but not other types--that used in spatial structural discriminations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Supersmart mice: Surprising or surprised? Theoretical comment on Singer, Boison, M?hler, Feldon, and Yee (2007).

The glycine transporter (GlyT1) regulates levels of the neurotransmitter glycine, a coagonist of the N-methyl-D-aspartate receptor (NMDAR), and as such may represent a novel site for developing cognition-enhancing drugs. Genetically modified mice with reduced levels of GlyT1 have been generated to test this hypothesis. P. Singer, D. Boison, H. M?hler, J. Feldon, and B. K. Yee (see record 2007-13974-001) now show, through a spontaneous exploration task, that mice in which GlyT1 has been deleted, specifically in neurons in the forebrain, demonstrate enhanced object recognition memory. Whereas both control and mutant mice show a preference for a novel object over a familiar object 2 min after the initial presentation of 1 of the objects, only the mutant mice show a preference for the novel object when tested after a 2-hr delay. The longer-lasting habituation displayed by the GlyT1 mice is consistent with a role for glycine/NMDAR-dependent synaptic plasticity in supporting a nonassociative, short-term memory trace of a recently experienced stimulus. This short-term habituation process may be independent of associative learning mechanisms and may be best described by A. R. Wagner's (1981) sometimes opponent process model. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The differential effects of stress on memory consolidation and retrieval: A potential involvement of reconsolidation? Theoretical comment on Beckner et al. (2006).

Previous experiments in the field of stress and memory have suggested a facilitative effect of stress hormones on the consolidation of information but an impairing effect on the retrieval of information. In the article "Stress Facilitates Consolidation of Verbal Memory for a Film but Does Not Affect Retrieval," V. E. Beckner, D. M. Tucker, Y. Delville, and D. C. Mohr (2006) (see record 2006-07279-002) report that exposure to an anticipatory psychological stress enhances consolidation, although it has no impact on the retrieval of previously learned information. This finding is discussed around the importance of the environmental context in which stress is applied and memory is measured. Here, the authors raise the possibility that the enhancing effects of stress on consolidation as reported by Beckner et al. may be explained by the fact that stress can act as a reactivation cue, leading to a 2nd round of consolidation, a process called reconsolidation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Memory Reconsolidation Hypothesis Revived but Restrained: Theoretical Comment on Biedenkapp and Rudy (2004).

J. C. Biedenkapp and J. W. Rudy (2004; see record 2004-19432-009) reported that the protein synthesis inhibitor anisomycin administered into the hippocampus after context preexposure or contextual fear conditioning impaired subsequent retention performance. In contrast, anisomycin administered after context memory retrieval did not impair subsequent contextual fear conditioning. Their findings challenge the hypothesis that memory retrieval induces memory reconsolidation and suggest that the hypothesis needs to be constrained to account for negative findings. However, their evidence does not suggest compelling clues to how the hypothesis might be constrained to accommodate the findings. Thus, it is not yet clear whether their findings can be explained by a revised reconsolidation hypothesis, or whether some other hypothesis is required to account for postretrieval memory impairment, when it is observed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The Hippocampal Role in Spatial Memory and the Familiarity-Recollection Distinction: A Case Study.

Memory for object locations and for events (comprising the receipt of an object) was tested in a case of developmental amnesia with focal hippocampal damage ("Jon"; F. Vargha-Khadem et al., 1997). Tests used virtual reality environments and forced-choice recognition with foils chosen to equalize the performance of control participants across conditions. Memory for the objects received was unimpaired, but the context of their receipt was forgotten. Memory for short lists of object locations was unimpaired when tested from the same viewpoint as presentation but impaired when tested from a shifted viewpoint. Same-view performance was disrupted by changing the background scene. These results are consistent with Jon having preserved matching to fixed sensory-bound representations but impaired reconstructed or manipulable representations underlying shifted-viewpoint recognition and episodic recollection. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Arbitrary associations in animals: What can paired associate recall in rats tell us about the neural basis of episodic memory? Theoretical comment on Kesner, Hunsaker, & Warthen (2008).

Detailed memories for unique episodes from an individual's past can be triggered, often effortlessly, when that individual is exposed to a stimulus that was present during the original event. The aim of Kesner et al. (see record 2008-17011-003) is to understand the neural basis of memory encoding that supports this cued recall of episodic memories. Kesner and colleagues make novel use of an object-place paired-associate task for rats to provide evidence for a critical role of dorsal CA3 in certain aspects of episodic memory encoding. Using one-trial cued recall versions of the task they show that when rats are cued with an object stimulus, they can be trained to revisit the location in which the object appeared previously. Conversely, when rats are cued with a location, they can learn to choose the object with which it was associated. Rats with dorsal CA3 lesions are severely impaired at these tasks. These data are consistent with the theory that the autoassociative network in CA3 supports the rapid formation of novel associations and may allow pattern completion--the phenomenom whereby a subset of the cues present at an encoding event triggers recall of the whole event. Although flexible recall of arbitrary associations is not fully demonstrated, the study contributes 2 novel behavioral tasks to the previously limited repertoire for studying paired associate recall in rats. It also builds on previous data to specify the role of the hippocampal CA3 subregion in cued recall--a critical aspect of episodic memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

How independent are parallel memory systems? A theoretical comment on Gibson and Shettleworth (2005).

Using only behavioral manipulations, B. M. Gibson and S. J. Shettleworth (2005) (see record 2005-03585-021) have shown that rats can simultaneously acquire both place and response information. Experiments in which these 2 kinds of information are presented sequentially (response followed by place), provide some evidence for blocking of place learning, suggesting an influence of information acquired by a response-learning system on the subsequent acquisition of information by a place-learning system. A detailed examination of the results in the context of information about the kinds of learning that take place on a maze suggests that the memory processes underlying the rats' behavior in this experiment were considerably more complex than is acknowledged by Gibson and Shettleworth. The discussion illustrates the importance of considering both behavioral and physiological information for understanding how learning and memory functions are organized in the brain. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of neonatal medial versus lateral temporal cortex injury: Theoretical comment on Malkova et al. (2010).

The article by Malkova, Mishkin, Suomo, and Bachevalier (see record 2010-24688-002) adds an important piece to our understanding of the role of the medial versus lateral temporal regions in socioemotional behavior. In their paper, they evaluate the effect of infant and adult amygdala lesions and infant inferotemporal cortex lesions on the social interactions of monkeys in infancy and adulthood. The results show that medial temporal lesions performed in infants produce greater effects on socioaffective behavior than similar lesions in adulthood and that infant monkeys with inferotemporal lesions exhibit social deficits that are resolved by adulthood. These results are relevant to three significant issues: (1) the role of the medial temporal and lateral temporal cortex in the symptoms of the Kluver-Bucy syndrome; (2) the role of age at injury in behavioral change after cerebral injuries; and (3) the importance of lesion locus and behavioral measure for recovery from infant and adult cerebral injury. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A near hat trick for Harlow (1953) with further thoughts on drive: Theoretical comment on Barbano and Cador (2005).

H. F. Harlow (1953) (see record 1954-03950-001) dismissed the belief that drive manipulations were very relevant to learning and behavior--if high drive did not damage performance outright, it would merely enhance the precurrent response--and proposed that knowledge of species-specific responses to specific stimulus situations was the best antidote to drive theory. The first 2 experiments by M. F. Barbano and M. Cador (2005) (see record 2005-13804-011) would seem to commend Harlow's views, but the 3rd experiment appears to show specific dissociations in behavioral topography based on drive state. Although Harlow remains correct for encouraging greater knowledge of the natural tendencies of animals, accumulating knowledge suggests that drive manipulations can result in various drives, for example, homeostatic, circadian, and stress based, that appear to alter the phenotype in specific ways, including specific response tendencies. Rather than eliminating drive, the data suggest using more targeted drive manipulations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)