Exercise Does Not Effect Context-dependent Episodic Memory

Memory has been shown to be strongly associated with the context in which it is encoded, suggesting that the context is central to the memory itself. However, the effect of exercise on context dependent object recognition is not fully known. We then set out to investigate the effect of exercise on context dependent object recognition. In Experiment 1 we showed that a context change reduced object recognition memory but did not significantly disrupt object recognition. In Experiment 2 we assessed whether exercise would the mitigate the effect of context change. We showed that exercise does not significantly improve object recognition nor did it mitigate the effect of context change on object recognition. These results suggest that a discrete context change can significantly disrupt retrieval of object recognition memory. Our results do not agree with the body of literature related to this topic, so further inquisition into these effects should be undertaken to confirm or refute the impact of exercise on contextual object recognition

Hippocampal Infusion of Zeta Inhibitory Peptide Impairs Recent, but Not Remote, Recognition Memory in Rats.

Spatial memory in rodents can be erased following the infusion of zeta inhibitory peptide (ZIP) into the dorsal hippocampus via indwelling guide cannulas. It is believed that ZIP impairs spatial memory by reversing established late-phase long-term potentiation (LTP). However, it is unclear whether other forms of hippocampus-dependent memory, such as recognition memory, are also supported by hippocampal LTP. In the current study, we tested recognition memory in rats following hippocampal ZIP infusion. In order to combat the limited targeting of infusions via cannula, we implemented a stereotaxic approach for infusing ZIP throughout the dorsal, intermediate, and ventral hippocampus. Rats infused with ZIP 3-7 days after training on the novel object recognition task exhibited impaired object recognition memory compared to control rats (those infused with aCSF). In contrast, rats infused with ZIP 1 month after training performed similar to control rats. The ability to form new memories after ZIP infusions remained intact. We suggest that enhanced recognition memory for recent events is supported by hippocampal LTP, which can be reversed by hippocampal ZIP infusion

The self-reference effect on memory in early childhood

The self-reference effect in memory is the advantage for information encoded about self, relative to other people. The early development of this effect was explored here using a concrete encoding paradigm. Trials comprised presentation of a self- or other-image paired with a concrete object. In Study 1, 4- to 6-year-old children (N = 53) were asked in each trial whether the child pictured would like the object. Recognition memory showed an advantage for self-paired objects. Study 2 (N = 55) replicated this finding in source memory. In Study 3 (N = 56), participants simply indicated object location. Again, recognition and source memory showed an advantage for self-paired items. These findings are discussed with reference to mechanisms that ensure information of potential self-relevance is reliably encoded

A Continual Trials Approach to Recognition Memory in Mice

This thesis sought to address and improve resolve some issues surrounding tests of recognition memory in animals. Since these spontaneous object recognition memory tasks are widely used, especially in mice, there is a need to develop a recognition task that would reduce the variability, extend and translate the task to potential areas of neuroscience research. Study 1 sought to validate the continual trials approach that was originally designed for rats to mice and replicate the findings of Ameen-Ali et al., (2012) in the spontaneous object recognition and object-location task. Study 1 found that performance of mice was comparable to previous studies of object recognition and object location memory, and statistically meaningful results were obtained with approximately 30 – 50 % fewer mice than typically used in the standard one trial a day version of the spontaneous object recognition tasks. Study 2 sought to extend the continual trials apparatus to establish the age-related changes of object recognition and object-location memory in normal ageing mice; and found that ageing mice showed no age-related decline of recognition memory. Study 3 found no evidence of age-related changes of object recognition and object-location memory in a transgenic mouse model of Alzheimer’s Disease, TASTPM mice. In study 4, the continual trials apparatus was adapted to incorporate variable retention delays (by blocking the sample and test phases) and found no evidence of delay-dependent effect on object recognition memory. Study 5 provided novel evidence that NMDA blockade using the MK-801 drug had no effect on object recognition memory in mice when controlled for state-dependency of memory. The key findings of this thesis include the successful validation of the continual trials apparatus in mice and the evidence that studies using reduced number of mice can nonetheless provide valid results in object recognition memory tasks

Associating object names with descriptions of shape that distinguish possible from impossible objects.

Five experiments examine the proposal that object names are closely linked torepresentations of global, 3D shape by comparing memory for simple line drawings of structurally possible and impossible novel objects.Objects were rendered impossible through local edge violations to global coherence (cf. Schacter, Cooper, & Delaney, 1990) and supplementary observations confirmed that the sets of possible and impossible objects were matched for their distinctiveness. Employing a test of explicit recognition memory, Experiment 1 confirmed that the possible and impossible objects were equally memorable. Experiments 2–4 demonstrated that adults learn names (single-syllable non-words presented as count nouns, e.g., “This is a dax”) for possible objectsmore easily than for impossible objects, and an item-based analysis showed that this effect was unrelated to either the memorability or the distinctiveness of the individual objects. Experiment 3 indicated that the effects of object possibility on name learning were long term (spanning at least 2months), implying that the cognitive processes being revealed can support the learning of object names in everyday life. Experiment 5 demonstrated that hearing someone else name an object at presentation improves recognition memory for possible objects, but not for impossible objects. Taken together, the results indicate that object names are closely linked to the descriptions of global, 3D shape that can be derived for structurally possible objects but not for structurally impossible objects. In addition, the results challenge the view that object decision and explicit recognition necessarily draw on separate memory systems,with only the former being supported by these descriptions of global object shape. It seems that recognition also can be supported by these descriptions, provided the original encoding conditions encourage their derivation. Hearing an object named at encoding appears to be just such a condition. These observations are discussed in relation to the effects of naming in other visual tasks, and to the role of visual attention in object identification

The Effect of Selective Cholinergic Lesion of Medial Septum on Recognition Memory

The objective of this study was to clarify the role of septal-hippocampal cholinergic neurons in object and spatial recognition memory. Stereotaxic-surgical infusion of the selective cholinergic neurotoxin, 192IgG-saporin (SAP), into the medial septum (MS) of Sprague-Dawley rats was utilized to establish an animal model of cholinergic deficit of the septal-hippocampal tract, which had been expected as a pathologic model of memory impairment for Alzheimer\u27s disease (AD). Three types of recognition memory were examined: retrograde object recognition, anterograde object recognition, and anterograde spatial recognition. These were examined with a modified version of a standard object recognition paradigm. For retrograde memory retention testing, rats received SAP after training; in contrast, for anterograde retention testing, rats received SAP before training. The time that the rats spent exploring familiar and novel objects or familiar objects in a novel location was measured. The effects of SAP on the three types of recognition memory were tested and compared to control animals. There was no significant difference in the mean exploration ratios (MERs) between control rats infused with artificial cerebrospinal fluid (aCSF) and control rats that did not receive surgery (NOR). The MERs for both control groups were in the range between 0.6-0.7, consistent with the object recognition testing literature. These results indicate that the infusion surgery itself had no effect on object or spatial recognition memory and that the methodology for object and spatial recognition developed for this study worked well. SAP lesioned rats did not demonstrate impairment of retrograde object recognition memory (0.68±0.04 vs 0.67±0.03, p = 0.888) and also displayed normal anterograde object recognition memory (0.67±0.04 vs 0.66±0.02, p = 0.866) compared to control rats. However, compared to controls, SAP rats were significantly impaired in anterograde spatial recognition memory as reflected in the fall of the MER for the SAP group to chance levels (0.51±0.04 vs 0.62±0.02. p = 0.0081). These findings suggest that the septal-hippocampal cholinergic neurons play an important role for spatial recognition memory, but not for object recognition memory and indicate that the septal-hippocampal cholinergic deficit may be responsible for the mild memory impairments shown in the early phase of AD

A correspondence-based neural mechanism for position invariant feature processing

Poster presentation: Introduction We here focus on constructing a hierarchical neural system for position-invariant recognition, which is one of the most fundamental invariant recognition achieved in visual processing [1,2]. The invariant recognition have been hypothesized to be done by matching a sensory image of a particular object stimulated on the retina to the most suitable representation stored in memory of the higher visual cortical area. Here arises a general problem: In such a visual processing, the position of the object image on the retina must be initially uncertain. Furthermore, the retinal activities possessing sensory information are being far from the ones in the higher area with a loss of the sensory object information. Nevertheless, with such recognition ambiguity, the particular object can effortlessly and easily be recognized. Our aim in this work is an attempt to resolve such a general recognition problem. ..

Dopamine D1 receptor stimulation modulates the formation and retrieval of novel object recognition memory: role of the prelimbic cortex

Previous studies have shown that dopamine D1 receptor antagonists impair novel object recognition memory but the effects of dopamine D1 receptor stimulation remain to be determined. This study investigated the effects of the selective dopamine D1 receptor agonist SKF81297 on acquisition and retrieval in the novel object recognition task in male Wistar rats. SKF81297 (0.4 and 0.8mg/kg s.c.) given 15 min before the sampling phase impaired novel object recognition evaluated 10 min or 24h later. The same treatments also reduced novel object recognition memory tested 24h after the sampling phase and when given 15min before the choice session. These data indicate that D1 receptor stimulation modulates both the encoding and retrieval of object recognition memory. Microinfusion of SKF81297 (0.025 or 0.05 μg/side) into the prelimbic sub-region of the medial prefrontal cortex (mPFC) in this case 10 min before the sampling phase also impaired novel object recognition memory, suggesting that the mPFC is one important site mediating the effects of D1 receptor stimulation on visual recognition memory

Change in background context disrupts performance on visual paired comparison following hippocampal damage

The medial temporal lobe plays a critical role in recognition memory but, within the medial temporal lobe, the precise neural structures underlying recognition memory remain equivocal. in this study, visual paired comparison (VPC) was used to investigate recognition memory in a human patient (YR), who had a discrete lesion of the hippocampus, and a group of monkeys with neonatal hippocampal lesions, which included the dentate gyrus, and a portion of parahippocampal region. Participants were required to view a picture of an object on a coloured background. Immediately afterwards, this familiar object was shown again, this time paired with a novel object. All participants displayed a novelty preference, provided the background on which the objects were shown was the same as the one used during the learning phase. When the background of the familiar object was changed between initial familiarization and test, only the control subjects showed a novelty preference; the hippocampal-lesioned monkeys and patient YR showed null preference. The results are interpreted within Eichenbaum and Bunsey's [Eichenbaum, H., & Bunsey, M. (1995). On the binding of associations in memory: Clues from studies on the role of the hippocampal region in paired-associate learning. Current Directions in Psychological Science, 4, 19-23] proposal that the hippocampus facilitates the formation of a flexible representation of the elements that make up a stimulus whereas the parahippocampal region is involved in the formation of a fused representation. (C) 2009 Elsevier Ltd. All rights reserved

Glutamate receptors in perirhinal cortex mediate encoding, retrieval, and consolidation of object recognition memory.

Object recognition is consistently impaired in human amnesia and animal models thereof. Results from subjects with permanent brain damage have revealed the importance of the perirhinal cortex to object recognition memory. Here, we report evidence from rats for interdependent but distinct stages in object recognition memory (encoding, retrieval, and consolidation), which require glutamate receptor activity within perirhinal cortex. Transient blockade of AMPA receptor-mediated synaptic transmission within perirhinal cortex disrupted encoding for short- and long-term memory as well as retrieval and consolidation. In contrast, transient NMDA receptor blockade during encoding affected only long-term object recognition memory; NMDA receptor activity was also necessary for consolidation but not retrieval. These results further demonstrate the importance of perirhinal cortex for object recognition memory and suggest that, as in the hippocampus, AMPA and NMDA receptors mediate synaptic transmission and activity-dependent synaptic plasticity, respectively, in several stages of memory processing