1
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Fernell M, Rivi V, Batabyal A, Lukowiak K. The temperature sensitivity of memory formation and persistence is altered by cold acclimation in a pond snail. J Exp Biol 2021; 224:269088. [PMID: 34105727 DOI: 10.1242/jeb.242513] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2021] [Accepted: 04/26/2021] [Indexed: 01/08/2023]
Abstract
There are reports on the inability of inbred, laboratory-reared Lymnaea stagnalis to perform feeding and aerial respiration in the cold. It has also been suggested that laboratory-bred snails have an inability to perform aerial respiration in winter months in the laboratory. Here, we used an inbred, laboratory-reared strain of Lymnaea (the S-strain) to demonstrate that the snails are capable of performing those behaviours in a cold (4°C) environment after a 2 day acclimation period. In addition, the inbred snails were able to perform aerial respiration during winter months at room temperature (20°C) in the laboratory. The persistence of long-term memory (LTM) was extended for at least 4 weeks by placing S-strain snails into a 4°C environment following training. Typically, the cold block (CB) procedure (1 h at 4°C) immediately after a training session blocks LTM formation in the S-strain but not in a freshly collected strain. Four weeks at 4°C transformed the S-strain phenotype into one resisting the CB procedure. Thus, with a 4 week cold spell snails gain a resistance to the CB procedure, and that would explain why freshly collected snails are resistant to the procedure. However, we found that F1 progeny of a freshly collected strain reared in the laboratory were resistant to the CB procedure. This suggests that an unknown selection resulted in the S-strain being susceptible to the CB procedure.
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Affiliation(s)
- Maria Fernell
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, AB T2N 4N1, Canada
| | - Veronica Rivi
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, AB T2N 4N1, Canada
| | - Anuradha Batabyal
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, AB T2N 4N1, Canada
| | - Ken Lukowiak
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, AB T2N 4N1, Canada
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2
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Swinton C, Swinton E, Phillips I, Lukowiak K. A thermal stressor, propranolol and long-term memory formation in freshly collected Lymnaea. J Exp Biol 2021; 224:jeb.242293. [PMID: 33795418 DOI: 10.1242/jeb.242293] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2021] [Accepted: 03/25/2021] [Indexed: 11/20/2022]
Abstract
A heat stressor (1 h at 30°C) in Lymnaea stagnalis before operant conditioning training of aerial respiration is sufficient to enhance long-term memory (LTM) formation in 'average' cognitive ability, laboratory-reared, inbred snails. However, in freshly collected outbred snails, the same heat stressor blocks LTM formation in 'smart' cognitive phenotype but not in average cognitive phenotype strains. Here, we hypothesize that (1) preventing the stress associated with the heat stressor before training allows LTM to form in the smart phenotype strains; and (2) alleviating the stress before a memory recall session allows a formed LTM to be recalled in the smart phenotype strains. We found that an injection of propranolol, which mitigates the stressor, before snails experience the heat stressor enabled two strains of the smart phenotype snails to form LTM, consistent with our first hypothesis. However, the injection of propranolol before a memory test session did not alleviate a memory recall block in the smart phenotype snails. Thus, our second hypothesis was not supported. Therefore, smart cognitive phenotype snails encountering a heat stressor have an inability to form LTM, but this inability can be overcome by the pre-injection of propranolol.
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Affiliation(s)
- Cayley Swinton
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, AB T2N 4N1, Canada
| | - Erin Swinton
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, AB T2N 4N1, Canada
| | - Iain Phillips
- Water Security Agency, Saskatoon, SK S7N 3R3, Canada
| | - Ken Lukowiak
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, AB T2N 4N1, Canada
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3
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Soudavari R, Batabyal A, Lukowiak K. In the great pond snail (Lymnaea stagnalis), two stressors that individually enhance memory in combination block memory formation. CAN J ZOOL 2021. [DOI: 10.1139/cjz-2020-0207] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Stress plays an important role in memory formation in the great pond snail (Lymnaea stagnalis (Linnaeus, 1758)). Individual stressors have been shown to enhance or to perturb long-term memory (LTM) formation. However, when snails perceive a combination of two stressors, it is unclear the outcome with regards to LTM formation. Here we first show that when L. stagnalis are exposed individually to either a predator stressor (crayfish effluent (CE), which is a kairomone) or a thermal stressor (30 °C), LTM formation is enhanced. In their natural environment, L. stagnalis may experience temperatures approaching 30 °C and they may encounter crayfish at the same time. How such a combination of stressors alters adaptive behaviour is unknown. Here we show that when these two stressors are combined, LTM formation is blocked. Since boiling CE inactivates the kairomone, we used previously boiled CE that we combined with the thermal stressor and found that LTM formation is again enhanced. These data show that (i) it cannot accurately be predicted how a combination of stressors when combined interact to alter LTM formation and (ii) there is a difference between hot CE and room temperature CE.
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Affiliation(s)
- Romina Soudavari
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, AB T2N 4N1, Canada
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, AB T2N 4N1, Canada
| | - Anuradha Batabyal
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, AB T2N 4N1, Canada
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, AB T2N 4N1, Canada
| | - Ken Lukowiak
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, AB T2N 4N1, Canada
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, AB T2N 4N1, Canada
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4
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Swinton E, Shymansky T, Swinton C, Lukowiak K. Stress before training alters memory retrieval of a non-declarative memory in Lymnaea. J Exp Biol 2020; 223:jeb223727. [PMID: 32601118 DOI: 10.1242/jeb.223727] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2020] [Accepted: 06/24/2020] [Indexed: 01/07/2023]
Abstract
Stress alters both memory formation and its retrieval. Here, we show that a combination of stressors before an associative learning event alters memory retrieval of a non-declarative memory in an invertebrate model system. Previously, two combinations of stressors were purported to prevent long-term memory (LTM) formation in 'smart' Lymnaea and this inability to form LTM was considered to be a cost of being smart. Here, we show that is not the case. The specific combinations of stressors used here cause emotional memory formation. Previously, it was shown that propranolol, a synthetic beta-blocker, altered emotional memory in Lymnaea. We show here that when propranolol but not saline is injected into smart snails before they perceive the combination of stressors, these snails form LTM. We then show that the injection of propranolol but not saline before a memory activation session allowed the memory to be recalled. That is, LTM formed but was not retrievable unless propranolol was injected pre-retrieval. Thus, the smart snails formed LTM in the face of the stressors but could not retrieve it.
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Affiliation(s)
- Erin Swinton
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada, T2N 4N1
| | - Tamila Shymansky
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada, T2N 4N1
| | - Cayley Swinton
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada, T2N 4N1
| | - Ken Lukowiak
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada, T2N 4N1
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5
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Swinton E, Swinton C, Lukowiak K. Shell damage leads to enhanced memory formation in Lymnaea. ACTA ACUST UNITED AC 2019; 222:jeb.207571. [PMID: 31431472 DOI: 10.1242/jeb.207571] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Accepted: 08/11/2019] [Indexed: 12/14/2022]
Abstract
Ecologically relevant stressors alter the ability of the pond snail, Lymnaea stagnalis, to form long-term memory (LTM). Here, we show that an environmentally relevant stressor, shell damage, has a dramatic effect on the enhancement of LTM formation. Damage in the form of a shell clip 24 h before operant conditioning training resulted in long-term memory (LTM) formation following a single 0.5 h training session (TS). Typically, in these snails, two 0.5 h TSs with a 1 h interval between the sessions are required to cause LTM formation. We show here that even with a 72 h interval between shell clip and training, memory enhancement still occurred. The stress associated with shell clip could be mitigated by an ongoing high-Ca2 + pond water environment, an injection of propranolol and a DNA methylation blocker. However, use of an anaesthetic (MgCl2) during the clip or intermittent exposure to the high-Ca2 + pond water environment did not mitigate the stress associated with the shell clip. Shell clip was also sufficient to cause juvenile snails, which neither learn nor form memory, to gain the capacity to form LTM. Together, the experiments demonstrate that shell clipping is an environmentally relevant stressor that can cause enhancement of LTM formation.
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Affiliation(s)
- Erin Swinton
- Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada, T2N 4N1
| | - Cayley Swinton
- Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada, T2N 4N1
| | - Ken Lukowiak
- Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada, T2N 4N1
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6
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Rothwell CM, Lukowiak K. Strain transformation: Enhancement of invertebrate memory in a new rearing environment. J Exp Biol 2019; 222:jeb.205112. [DOI: 10.1242/jeb.205112] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2019] [Accepted: 06/24/2019] [Indexed: 11/20/2022]
Abstract
Memory formation is influenced by a variety of factors, including the environmental conditions in which an organism is reared. Here, we studied the memory-forming ability of the lab-bred B-strain of Lymnaea following a change in their rearing environment from Brock University to the University of Calgary. We have previously demonstrated that this move enhances memory-forming ability and here we studied the magnitude of this phenotypic change. Once reared to adulthood at the University of Calgary, the B-strain animals were first tested to determine how many training sessions were required for the formation of long-term memory (LTM) to occur. Following this change in environment, the B-strain transformed into a ‘smart’ lab-bred strain requiring only a single 0.5 h session to form LTM. Next, we tested whether exposure to physiologically relevant stressors would block the formation of LTM in this ‘transformed’ B-strain, as this obstruction has previously been observed in ‘smart’ snails collected from the wild. Interestingly, neither stressor tested in this study perturbed memory formation in this ‘transformed’ lab-bred strain. Additionally, both the ‘smart’ memory phenotype, as well as the increased stress resiliency, were observed in the second generation of ‘transformed’ B-strain at both the juvenile and adult stages. This suggests that a change in rearing environment can contribute to the memory-forming ability of lab-bred Lymnaea.
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Affiliation(s)
- Cailin M. Rothwell
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta, T2N 4N1, Canada
| | - Ken Lukowiak
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta, T2N 4N1, Canada
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7
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Strain-specific effects of crowding on long-term memory formation in Lymnaea. Comp Biochem Physiol A Mol Integr Physiol 2018; 222:43-51. [DOI: 10.1016/j.cbpa.2018.04.010] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2018] [Revised: 04/16/2018] [Accepted: 04/17/2018] [Indexed: 12/30/2022]
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8
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Swinton E, de Freitas E, Swinton C, Shymansky T, Hiles E, Zhang J, Rothwell C, Lukowiak K. Green tea and cocoa enhance cognition in Lymnaea. Commun Integr Biol 2018; 11:e1434390. [PMID: 29497476 PMCID: PMC5824930 DOI: 10.1080/19420889.2018.1434390] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2017] [Revised: 01/17/2018] [Accepted: 01/19/2018] [Indexed: 02/05/2023] Open
Abstract
A flavonoid, (-)-epicatechi (Epi), enhances long-term memory (LTM) formation in Lymnaea and reverses memory obstruction caused by stress. Many foods contain substantial amounts of Epi, (e.g. green tea and cocoa). In humans eating such foods may directly or indirectly enhance cognition. We directly test whether operant conditioning training Lymnaea in these natural foods result in the same effects as training snails in pure Epi. We found that exposure to products containing high concentrations of Epi (e.g. green tea and cocoa) during training enhanced memory formation and could even reverse a learning and memory deficit brought about by stress. Epi can be photo-inactivated by exposure to ultraviolet light. We found that following photo-inactivation of Epi, memory enhancement did not occur. Photo-inactivation of foods containing Epi (e,g. green tea) blocked their ability to enhance LTM. Our data are thus consistent with the hypothesis that dietary sources of Epi can have positive benefits on cognitive ability and be able to reverse memory aversive states.
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Affiliation(s)
- Erin Swinton
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Emily de Freitas
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Cayley Swinton
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Tamila Shymansky
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Emily Hiles
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Jack Zhang
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Cailin Rothwell
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Ken Lukowiak
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
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9
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Rothwell CM, Spencer GE, Lukowiak K. The effect of rearing environment on memory formation. J Exp Biol 2018; 221:jeb.180521. [DOI: 10.1242/jeb.180521] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2018] [Accepted: 03/27/2018] [Indexed: 11/20/2022]
Abstract
Lymnaea stagnalis is a well-studied model system for determining how changes in the environment influence associative learning and memory formation. For example, some wild strains of Lymnaea, collected from separate geographic locations show superior memory-forming abilities compared to others. Here, we have studied memory formation in two laboratory-bred Lymnaea strains, derived from the same original population in The Netherlands. The two strains were reared in two different laboratories at the University of Calgary (C-strain) and at Brock University (B-strain) for many years and were found to differ in their memory-forming ability. Specifically, the C-strain required only two training sessions to form long-term memory (LTM) whereas the B-strain required four sessions to form LTM. Additionally, the LTM formed by the B-strain persisted for a shorter amount of time than the memory formed by the C-strain. Thus, despite being derived from the same original population, the C- and B-strains have developed different memory-forming abilities. Next, we raised the two strains from embryos ‘Away’ from home (i.e. in the other laboratory) over two generations and assessed their memory-forming abilities. The B-strain reared and maintained at the University of Calgary demonstrated improved memory-forming ability within a single generation, while the C-strain reared at Brock University retained their normal LTM forming ability across two subsequent generations. This suggests that local environmental factors may contribute to the behavioural divergence observed between these two laboratory-bred strains.
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Affiliation(s)
- Cailin M. Rothwell
- Hotchkiss Brain Institute, Cumming School and Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta, T2N 4N1, Canada
| | - Gaynor E. Spencer
- Department of Biological Sciences, Brock University, 1812 Sir Isaac Brock Way, St. Catharines, Ontario, L2S 3A1, Canada
| | - Ken Lukowiak
- Hotchkiss Brain Institute, Cumming School and Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta, T2N 4N1, Canada
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10
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Hughes E, Shymansky T, Swinton E, Lukowiak KS, Swinton C, Sunada H, Protheroe A, Phillips I, Lukowiak K. Strain-specific differences of the effects of stress on memory in Lymnaea. J Exp Biol 2017; 220:891-899. [DOI: 10.1242/jeb.149161] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2016] [Accepted: 12/14/2016] [Indexed: 12/17/2022]
Abstract
ABSTRACT
Stress alters the ability to form, recall and maintain memory according to the Yerkes–Dodson/Hebb (YDH) law. The effects of environmentally relevant stressors, such as low environmental calcium and crowding, on learning and memory have previously been described in a laboratory-reared ‘average’ strain of Lymnaea stagnalis (i.e. the Dutch strain) as well as two strains of freshly collected L. stagnalis with enhanced memory formation abilities (i.e. ‘smart’ snails). Here, we use L. stagnalis to study the effects of other environmentally relevant stressors on memory formation in two other strains of freshly collected snails, one ‘smart’ and one ‘average’. The stressors we examined are thermal, resource restriction combined with food odour, predator detection and, for the first time, tissue injury (shell damage). We show that the same stressor has significantly different effects on memory formation depending on whether snails are ‘smart’ or ‘average’. Specifically, our data suggest that a stressor or a combination of stressors act to enhance memory in ‘average’ snails but obstruct memory formation in ‘smart’ snails. These results are consistent with the YDH law and our hypothesis that ‘smart’ snails are more easily stressed than ‘average’ snails.
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Affiliation(s)
- Emily Hughes
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Dr NW, Calgary, Alberta T2N 4N1, Canada
| | - Tamila Shymansky
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Dr NW, Calgary, Alberta T2N 4N1, Canada
| | - Erin Swinton
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Dr NW, Calgary, Alberta T2N 4N1, Canada
| | - Kai S. Lukowiak
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Dr NW, Calgary, Alberta T2N 4N1, Canada
| | - Cayley Swinton
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Dr NW, Calgary, Alberta T2N 4N1, Canada
| | - Hiroshi Sunada
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Dr NW, Calgary, Alberta T2N 4N1, Canada
| | - Amy Protheroe
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Dr NW, Calgary, Alberta T2N 4N1, Canada
| | - Iain Phillips
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Dr NW, Calgary, Alberta T2N 4N1, Canada
| | - Ken Lukowiak
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Dr NW, Calgary, Alberta T2N 4N1, Canada
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11
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Carpenter S, Rothwell CM, Wright ML, de Hoog E, Walker S, Hudson E, Spencer GE. Extending the duration of long-term memories: Interactions between environmental darkness and retinoid signaling. Neurobiol Learn Mem 2016; 136:34-46. [PMID: 27646787 DOI: 10.1016/j.nlm.2016.09.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2016] [Revised: 08/30/2016] [Accepted: 09/15/2016] [Indexed: 01/05/2023]
Abstract
Retinoid signaling plays an important role in hippocampal-dependent vertebrate memories. However, we have previously demonstrated that retinoids are also involved in the formation of long-term implicit memory following operant conditioning of the invertebrate mollusc Lymnaea stagnalis. Furthermore, we have discovered an interaction between environmental light/dark conditions and retinoid signaling and the ability of both to convert intermediate-term memory into long-term memory. In this study, we extend these findings to show that retinoid receptor agonists and environmental darkness can both also extend the duration of long-term memory. Interestingly, exposure to constant environmental darkness significantly increased the expression of retinoid receptors in the adult central nervous system, as well as induced specific changes in a key neuron mediating the conditioned behaviour. These studies not only shed more light on how retinoids influence memory formation, but also further link environmental light conditions to the retinoid signaling pathway.
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Affiliation(s)
- Sevanne Carpenter
- Dept. Biological Sciences, Brock University, 1812 Sir Isaac Brock's Way, St. Catharines, Ontario L2S 3A1, Canada
| | - Cailin M Rothwell
- Dept. Biological Sciences, Brock University, 1812 Sir Isaac Brock's Way, St. Catharines, Ontario L2S 3A1, Canada
| | - Michelle L Wright
- Dept. Biological Sciences, Brock University, 1812 Sir Isaac Brock's Way, St. Catharines, Ontario L2S 3A1, Canada
| | - Eric de Hoog
- Dept. Biological Sciences, Brock University, 1812 Sir Isaac Brock's Way, St. Catharines, Ontario L2S 3A1, Canada
| | - Sarah Walker
- Dept. Biological Sciences, Brock University, 1812 Sir Isaac Brock's Way, St. Catharines, Ontario L2S 3A1, Canada
| | - Emma Hudson
- Dept. Biological Sciences, Brock University, 1812 Sir Isaac Brock's Way, St. Catharines, Ontario L2S 3A1, Canada
| | - Gaynor E Spencer
- Dept. Biological Sciences, Brock University, 1812 Sir Isaac Brock's Way, St. Catharines, Ontario L2S 3A1, Canada.
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12
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Forest J, Sunada H, Dodd S, Lukowiak K. Training Lymnaea in the presence of a predator scent results in a long-lasting ability to form enhanced long-term memory. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2016; 202:399-409. [PMID: 27138222 DOI: 10.1007/s00359-016-1086-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2015] [Revised: 04/17/2016] [Accepted: 04/19/2016] [Indexed: 12/25/2022]
Abstract
Lymnaea exposed to crayfish effluent (CE) gain an enhanced ability to form long-term memory (LTM). We test the hypothesis that a single CE exposure and operant conditioning training leads to long lasting changes in the capability of snails to form LTM when tested in pond water four weeks later. We trained both juvenile and adult snails with a single 0.5 h training session in CE and show that LTM was present 24 h later. Snails trained in a similar manner in just pond water show no LTM. We then asked if such training in CE conferred enhanced memory forming capabilities on these snails four weeks later. That is, would LTM be formed in these snails four weeks later following a single 0.5 h training session in pond water? We found that both adult and juvenile snails previously trained in CE one month previously had enhanced LTM formation abilities. The injection of a DNA methylation blocker, 5-AZA, prior to training in adult snails blocked enhanced LTM formation four weeks later. Finally, this enhanced LTM forming ability was not passed on to the next generation of snails.
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Affiliation(s)
- Jeremy Forest
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, AB, T2N 4N1, Canada.,University Claude Bernard, Lyon, France
| | - Hiroshi Sunada
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, AB, T2N 4N1, Canada
| | - Shawn Dodd
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, AB, T2N 4N1, Canada
| | - Ken Lukowiak
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, AB, T2N 4N1, Canada.
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13
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Knezevic B, Komatsuzaki Y, de Freitas E, Lukowiak K. A flavanoid component of chocolate quickly reverses an imposed memory deficit. ACTA ACUST UNITED AC 2016; 219:816-23. [PMID: 26823103 DOI: 10.1242/jeb.130765] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2015] [Accepted: 12/30/2015] [Indexed: 01/27/2023]
Abstract
The ability to remember is influenced by environmental and lifestyle factors, such as stress and diet. A flavanol contained in chocolate, epicatechin (Epi), has been shown to enhance long-term memory (LTM) formation in Lymnaea. Combining two stressors (low-calcium pond water and crowding) blocks learning and all forms of memory; that is, this combination of environmentally relevant stressors creates a memory-unfriendly state. We tested the hypothesis that Epi will immediately reverse the memory-unfriendly state, i.e. that snails in the memory-deficit state when trained in Epi will immediately become competent to learn and form memory. We found that Epi not only reverses the memory-deficit state but also further enhances LTM formation. Thus, a naturally occurring bioactive plant compound can overcome a memory-unfriendly state. This supports the idea that bioactive substances may mitigate memory-making deficits that, for example, occur with ageing.
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Affiliation(s)
- Bogdan Knezevic
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta, Canada T2N 4N1
| | - Yoshimasa Komatsuzaki
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta, Canada T2N 4N1
| | - Emily de Freitas
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta, Canada T2N 4N1
| | - Ken Lukowiak
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta, Canada T2N 4N1
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14
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Shymansky T, Protheroe A, Hughes E, Swinton C, Swinton E, Lukowiak KS, Phillips I, Lukowiak K. Juveniles of Lymnaea smart snails do not perseverate and have the capacity to form LTM. J Exp Biol 2016; 220:408-413. [DOI: 10.1242/jeb.147884] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2016] [Accepted: 11/11/2016] [Indexed: 01/18/2023]
Abstract
Previously, it was concluded that the nervous systems of the juvenile snails were not capable of mediating LTM. However, exposure and training of those juvenile snails in the presence of a predator cue significantly altered their ability to learn and form LTM. In addition, there are some strains of Lymnaea which have been identified as ‘smart’. These snails form LTM significantly better than the lab-bred strain. Here we show that juveniles of two smart snail strains are not only capable of associative learning, but also have the capacity to form LTM following a single 0.5h training session. We also show that freshly collected ‘wild’ ‘average’ juveniles are also not able to form LTM. Thus, the smart snail phenotype in these strains is expressed in juveniles.
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Affiliation(s)
- Tamila Shymansky
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Dr NW, Calgary AB T2N 4N1, Canada
| | - Amy Protheroe
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Dr NW, Calgary AB T2N 4N1, Canada
| | - Emily Hughes
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Dr NW, Calgary AB T2N 4N1, Canada
| | - Cayley Swinton
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Dr NW, Calgary AB T2N 4N1, Canada
| | - Erin Swinton
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Dr NW, Calgary AB T2N 4N1, Canada
| | - Kai S. Lukowiak
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Dr NW, Calgary AB T2N 4N1, Canada
| | - Iain Phillips
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Dr NW, Calgary AB T2N 4N1, Canada
| | - Ken Lukowiak
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Dr NW, Calgary AB T2N 4N1, Canada
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15
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Habitat stability, predation risk and 'memory syndromes'. Sci Rep 2015; 5:10538. [PMID: 26013966 PMCID: PMC4444974 DOI: 10.1038/srep10538] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2014] [Accepted: 04/24/2015] [Indexed: 11/11/2022] Open
Abstract
Habitat stability and predation pressure are thought to be major drivers in the evolutionary maintenance of behavioural syndromes, with trait covariance only occurring within specific habitats. However, animals also exhibit behavioural plasticity, often through memory formation. Memory formation across traits may be linked, with covariance in memory traits (memory syndromes) selected under particular environmental conditions. This study tests whether the pond snail, Lymnaea stagnalis, demonstrates consistency among memory traits (‘memory syndrome’) related to threat avoidance and foraging. We used eight populations originating from three different habitat types: i) laboratory populations (stable habitat, predator-free); ii) river populations (fairly stable habitat, fish predation); and iii) ditch populations (unstable habitat, invertebrate predation). At a population level, there was a negative relationship between memories related to threat avoidance and food selectivity, but no consistency within habitat type. At an individual level, covariance between memory traits was dependent on habitat. Laboratory populations showed no covariance among memory traits, whereas river populations showed a positive correlation between food memories, and ditch populations demonstrated a negative relationship between threat memory and food memories. Therefore, selection pressures among habitats appear to act independently on memory trait covariation at an individual level and the average response within a population.
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16
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Dodd SX, Lukowiak K. Sequential exposure to a combination of stressors blocks memory reconsolidation in Lymnaea. J Exp Biol 2015; 218:923-30. [PMID: 25617463 DOI: 10.1242/jeb.114876] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Stress alters the formation of long-term memory (LTM) in Lymnaea. When snails are exposed to more than one stressor, however, how the memory is altered becomes complicated. Here, we investigated how multiple stressors applied in a specific pattern affect an aspect of memory not often studied in regards to stress - reconsolidation. We hypothesized that the application of a sequence of stressors would block the reconsolidation process. Reconsolidation occurs following activation of a previously formed memory. Sequential crowding and handling were used as the stressors to block reconsolidation. When the two stressors were sequentially presented immediately following memory activation, reconsolidation was blocked. However, if the sequential presentation of the stressors was delayed for 1 h after memory activation, reconsolidation was not blocked. That is, LTM was observed. Finally, presentation of either stressor alone did not block reconsolidation. Thus, stressors can block reconsolidation, which may be preferable to pharmacological manipulations.
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Affiliation(s)
- Shawn Xavier Dodd
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta, Canada T2N 4N1
| | - Ken Lukowiak
- Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta, Canada T2N 4N1
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17
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Rothwell CM, Simmons J, Peters G, Spencer GE. Novel interactive effects of darkness and retinoid signaling in the ability to form long-term memory following aversive operant conditioning. Neurobiol Learn Mem 2014; 114:251-63. [PMID: 25062644 DOI: 10.1016/j.nlm.2014.07.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2014] [Revised: 07/11/2014] [Accepted: 07/15/2014] [Indexed: 02/07/2023]
Abstract
The vitamin A metabolite, retinoic acid, is important for memory formation and hippocampal synaptic plasticity in vertebrate species. In our studies in the mollusc Lymnaea stagnalis, we have shown that retinoic acid plays a role in memory formation following operant conditioning of the aerial respiratory behaviour. Inhibition of either retinaldehyde dehydrogenase (RALDH) or the retinoid receptors prevents long-term memory (LTM) formation, whereas synthetic retinoid receptor agonists promote memory formation by converting intermediate-term memory (ITM) into LTM. In this study, animals were exposed to constant darkness in order to test whether light-sensitive retinoic acid would promote memory formation. However, we found that exposure to constant darkness alone (in the absence of retinoic acid) enhanced memory formation. To determine whether the memory-promoting effects of darkness could override the memory-inhibiting effects of the retinoid signaling inhibitors, we exposed snails to RALDH inhibitors or a retinoid receptor antagonist in constant darkness. We found that darkness overcame the inhibitory effects of RALDH inhibition, but did not overcome the inhibitory effects of the retinoid receptor antagonist. We also tested whether constant darkness and training affected the mRNA levels of the retinoid metabolic enzymes RALDH and Cyp26, or the mRNA levels of the retinoid receptors, but found no significant effect. Overall, these data demonstrate an interaction between environmental light conditions and the retinoid signaling pathway, which influence long-term memory formation in a mollusc.
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Affiliation(s)
- Cailin M Rothwell
- Department of Biological Sciences, Brock University, St. Catharines, Ontario L2S 3A1, Canada
| | - Jason Simmons
- Department of Biological Sciences, Brock University, St. Catharines, Ontario L2S 3A1, Canada
| | - Grace Peters
- Department of Biological Sciences, Brock University, St. Catharines, Ontario L2S 3A1, Canada
| | - Gaynor E Spencer
- Department of Biological Sciences, Brock University, St. Catharines, Ontario L2S 3A1, Canada.
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Lukowiak K, Sunada H, Teskey M, Lukowiak K, Dalesman S. Environmentally relevant stressors alter memory formation in the pond snail Lymnaea. J Exp Biol 2014; 217:76-83. [DOI: 10.1242/jeb.089441] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Stress alters adaptive behaviours such as learning and memory. Stressors can either enhance or diminish learning, memory formation and/or memory recall. We focus attention here on how environmentally relevant stressors alter learning, memory and forgetting in the pond snail, Lymnaea stagnalis. Operant conditioning of aerial respiration causes associative learning that may lead to long-term memory (LTM) formation. However, individual ecologically relevant stressors, combinations of stressors, and bio-active substances can alter whether or not learning occurs or memory forms. While the behavioural memory phenotype may be similar as a result of exposure to different stressors, how each stressor alters memory formation may occur differently. In addition, when a combination of stressors are presented it is difficult to predict ahead of time what the outcome will be regarding memory formation. Thus, how combinations of stressors act is an emergent property of how the snail perceives the stressors.
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Affiliation(s)
- Ken Lukowiak
- Hotchkiss Brain Institute, Faculty of Medicine, University of Calgary, Calgary, AB, Canada, T2N 4N1
| | - Hiroshi Sunada
- Hotchkiss Brain Institute, Faculty of Medicine, University of Calgary, Calgary, AB, Canada, T2N 4N1
| | - Morgan Teskey
- Hotchkiss Brain Institute, Faculty of Medicine, University of Calgary, Calgary, AB, Canada, T2N 4N1
| | - Kai Lukowiak
- Hotchkiss Brain Institute, Faculty of Medicine, University of Calgary, Calgary, AB, Canada, T2N 4N1
| | - Sarah Dalesman
- Hotchkiss Brain Institute, Faculty of Medicine, University of Calgary, Calgary, AB, Canada, T2N 4N1
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Ito E, Yamagishi M, Takigami S, Sakakibara M, Fujito Y, Lukowiak K. The Yerkes-Dodson law and appropriate stimuli for conditioned taste aversion in Lymnaea. J Exp Biol 2014; 218:336-9. [DOI: 10.1242/jeb.113266] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Abstract
The pond snail Lymnaea stagnalis can learn conditioned taste aversion and then consolidate it into long-term memory (LTM). A high voltage electric shock was used as the unconditioned stimulus (US), whereas we previously used KCl. We varied both the strength of the conditioned stimulus (CS) and US to determine if the so-called Yerkes-Dodson law prevailed. This is an empirical relationship between the state of arousal and LTM formation, showing that there is an optimal level of arousal leading to memory formation. However, too little or too much arousal results in poorer LTM. We found here that the most appropriate stimuli to use in taste aversion training in Lymnaea were a 10 mmol l-1 sucrose solution as the CS and a 3-s electric shock as the US.
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20
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Knezevic B, Lukowiak K. A flavonol, epicatechin, reverses the suppressive effects of a stressor on LTM formation. J Exp Biol 2014; 217:4004-9. [DOI: 10.1242/jeb.110726] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Abstract
Learning and subsequent memory formation are influenced by both environmental and lifestyle factors, such as stress and diet. Epicatechin, a plant flavonol found in cocoa, red wine, and green tea enhances long term memory formation (LTM) in Lymnaea; while an ecologically relevant stressor, low calcium pond water, suppress LTM formation. We tested the hypothesis that epicatechin overcomes the suppressive effects of the stressor on LTM formation in the continued presence of the stressor. Snails trained in low calcium pond water exhibit learning but not LTM. Epicatechin (15 mg/L) in control pond water enhances LTM formation. When epicatechin was added to the low calcium pond water an enhanced LTM similar to that seen in control pond water was observed. Thus, a naturally occurring bioactive plant compound was able to overcome the suppressive effects of an ecologically relevant stressor on LTM formation.
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21
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Spencer G, Rothwell C. Behavioural and network plasticity following conditioning of the aerial respiratory response of a pulmonate mollusc. CAN J ZOOL 2013. [DOI: 10.1139/cjz-2012-0291] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Most molluscs perform respiration using gills, but the pulmonate molluscs have developed a primitive lung with which they perform pulmonary respiration. The flow of air into this lung occurs through an opening called the pneumostome, and pulmonate molluscs travel to the surface of the water to obtain oxygen from the surrounding atmosphere. The aerial respiratory behaviour of the pulmonate mollusc, the great pond snail (Lymnaea stagnalis (L., 1758)), has been well studied, and a three-neuron central pattern generator (CPG) controlling this rhythmic behaviour has been identified. The aerial respiratory behaviour of L. stagnalis can be operantly conditioned and plasticity within the CPG has been associated with the conditioned response. In this review, we describe both the aerial respiratory behaviour and the underlying neuronal network of this pulmonate mollusc, and then discuss both the behavioural and network plasticity that results from the conditioning of this behaviour.
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Affiliation(s)
- G.E. Spencer
- Department of Biological Sciences, Brock University, 500 Glenridge Avenue, St. Catharines, ON L2S 3A1, Canada
| | - C.M. Rothwell
- Department of Biological Sciences, Brock University, 500 Glenridge Avenue, St. Catharines, ON L2S 3A1, Canada
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22
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Dalesman S, Lukowiak K. Social snails: the effect of social isolation on cognition is dependent on environmental context. ACTA ACUST UNITED AC 2012; 214:4179-85. [PMID: 22116760 DOI: 10.1242/jeb.064857] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Social isolation is often considered to have negative effects on cognitive function in a wide range of species. Here we assess how environmental context alters the effect of isolation on long-term memory formation (24 h) in the pond snail Lymnaea stagnalis. We operantly trained snails to reduce aerial respiration in hypoxia following exposure to one of three social conditions: (1) maintained and trained in groups; (2) maintained in groups, trained in isolation; or (3) maintained and trained in isolation. In addition, snails also experienced four stress exposure levels: control, exposure to low calcium availability, predator kairomone exposure during training or a combination of low calcium and predator kairomones. Snails isolated during training alone demonstrated no difference in memory formation compared with the snails trained in groups. Maintaining snails in social isolation for 8 days prior to training had a neutral effect on memory in control conditions or in the presence of predator kairomones alone. However, social isolation enhanced long-term memory formation in snails exposed to low calcium conditions, a stress that blocks memory formation in snails maintained in groups. Conversely, when exposed to low calcium and predator kairomones combined, grouped snails normally demonstrate long-term memory, but following maintenance in isolation long-term memory was blocked. Therefore, the effect of social isolation on cognitive function is highly dependent on the environmental context in which it is experienced.
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Affiliation(s)
- Sarah Dalesman
- Hotchkiss Brain Institute, Department of Physiology and Pharmacology, University of Calgary, Calgary, AB, Canada.
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23
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Dalesman S, Lukowiak K. How stress alters memory in 'smart' snails. PLoS One 2012; 7:e32334. [PMID: 22384220 PMCID: PMC3286460 DOI: 10.1371/journal.pone.0032334] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2011] [Accepted: 01/26/2012] [Indexed: 11/30/2022] Open
Abstract
Cognitive ability varies within species, but whether this variation alters the manner in which memory formation is affected by environmental stress is unclear. The great pond snail, Lymnaea stagnalis, is commonly used as model species in studies of learning and memory. The majority of those studies used a single laboratory strain (i.e. the Dutch strain) originating from a wild population in the Netherlands. However, our recent work has identified natural populations that demonstrate significantly enhanced long-term memory (LTM) formation relative to the Dutch strain following operant conditioning of aerial respiratory behaviour. Here we assess how two populations with enhanced memory formation (i.e. ‘smart’ snails), one from Canada (Trans Canada 1: TC1) and one from the U.K. (Chilton Moor: CM) respond to ecologically relevant stressors. In control conditions the Dutch strain forms memory lasting 1–3 h following a single 0.5 h training session in our standard calcium pond water (80 mg/l [Ca2+]), whereas the TC1 and CM populations formed LTM lasting 5+ days following this training regime. Exposure to low environmental calcium pond water (20 mg/l [Ca2+]), which blocks LTM in the Dutch strain, reduced LTM retention to 24 h in the TC1 and CM populations. Crowding (20 snails in 100 ml) immediately prior to training blocks LTM in the Dutch strain, and also did so in TC1 and CM populations. Therefore, snails with enhanced cognitive ability respond to these ecologically relevant stressors in a similar manner to the Dutch strain, but are more robust at forming LTM in a low calcium environment. Despite the two populations (CM and TC1) originating from different continents, LTM formation was indistinguishable in both control and stressed conditions. This indicates that the underlying mechanisms controlling cognitive differences among populations may be highly conserved in L. stagnalis.
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Affiliation(s)
- Sarah Dalesman
- Hotchkiss Brain Institute, Department of Physiology and Pharmacology, University of Calgary, Calgary, Alberta, Canada.
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24
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Dalesman S, Lukowiak K. Alternate behavioural measurements following a single operant training regime demonstrate differences in memory retention. Anim Cogn 2012; 15:483-94. [DOI: 10.1007/s10071-012-0472-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2011] [Revised: 01/05/2012] [Accepted: 02/03/2012] [Indexed: 01/09/2023]
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25
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Braun MH, Lukowiak K, Karnik V, Lukowiak K. Differences in neuronal activity explain differences in memory forming abilities of different populations of Lymnaea stagnalis. Neurobiol Learn Mem 2011; 97:173-82. [PMID: 22146779 DOI: 10.1016/j.nlm.2011.11.005] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2011] [Revised: 11/16/2011] [Accepted: 11/17/2011] [Indexed: 12/20/2022]
Abstract
The ability to learn and form long-term memory (LTM) can enhance an animal's fitness, for example, by allowing them to remember predators, food sources or conspecific interactions. Here we use the pond snail, Lymnaea stagnalis, to assess whether variability between natural populations (i.e., strains) in memory forming capabilities correlates with electrophysiological properties at the level of a single neuron, RPeD1. RPeD1 is a necessary site of LTM formation of aerial respiratory behaviour following operant conditioning. We used strains from two small, separate permanent ponds (TC1 and TC2). A comparison of the two populations showed that the TC1 strain had enhanced memory forming capabilities. Further, the behavioural phenotype of enhanced memory strain was explained, in part, by differences in the electrophysiology of RPeD1. Compared to RPeD1 from the naive TC2 strain, RPeD1 from the TC1 strain has both a decreased resistance and decreased excitability. Moreover, 24h after a single 0.5h training session, those membrane properties, as well as the firing and bursting rate, decrease further in the TC1 strain but not in the TC2 strain. The initial differences in RPeD1 properties in the TC1 strain coupled with their ability to further change these properties with a single training session suggests that RPeD1 neurons from the TC1 strain are "primed" to rapidly form memory.
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Affiliation(s)
- Marvin H Braun
- Hotchkiss Brain Institute, Department of Physiology and Pharmacology, University of Calgary, Calgary, Alberta, Canada T2N 4N1.
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