Reliability and Validity of Experiment in the Neurobiology of Learning and Memory (original) (raw)
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Experimentation in Cognitive Neuroscience and Cognitive Neurobiology
Neuroscience is a laboratory-based science that spans multiple levels of analysis from molecular genetics to behavior. At every level of analysis, experiments are designed in order to answer empirical questions about phenomena of interest. Understanding the nature and structure of experimentation in neuroscience is fundamental for assessing the quality of the evidence produced by such experiments and the kinds of claims that are warranted by the data. This chapter provides a general conceptual framework for thinking about evidence and experimentation in neuroscience with a particular focus on two research areas: cognitive neuroscience and cognitive neurobiology.
Synaptic plasticity: understanding the neurobiological mechanisms of learning and memory: Part I
Salud …, 2001
Plasticity of the nervous system has been related to learning and memory processing as early as the beginning of the century; although, remotely, brain plasticity in relation to behavior has been connoted over the past two centuries. However, four decades ago, several evidences have shown that experience and training induce neural changes, showing that major neuroanatomical, neurochemical as well as molecular changes are required for the establishment of a long-term memory process. Early experimental procedures showed that differential experience, training and/or informal experience could produce altered quantified changes in the brain of mammals. Moreover, neuropsychologists have emphasized that different memories could be localized in separate cortical areas of the brain, but updated evidences assert that memory systems are specifically distributed in exclusive neural networks in the cortex. For instance, the same cortical systems that lead us to perceive and move in our environment, are used as neural substrates for memory retrieval. Such memories are the result of the repeated activity of millions of neurons assembled into distinct neural networks, where plastic changes in synaptic function leads to the strengthening of the same synaptic connections with the result of reconstructed permanent traces that lead to remembrance (Hebb Postulate). Elementary forms of learning and memory have been studied in simple neural systems of invertebrates, and as such have led the way for understanding much of the electrophysiological and neurochemical events occurring during LTP. Long-term potentiation (LTP) is the result of the increase in the strength of synaptic transmission, lasting as long as can be measured from hours to days. LTP has been detected in several areas of the brain, particularly, in the hippocampus, amygdala, and cortex, including several related limbic structures in the mammalian brain. LTP represents up to date the best model available for understanding the cellular basis of learning and memory in the central nervous system of mammals including humans.
Synaptic Plasticity and Memory: An Evaluation of the Hypothesis
Annual Review of Neuroscience, 2000
Changing the strength of connections between neurons is widely assumed to be the mechanism by which memory traces are encoded and stored in the central nervous system. In its most general form, the synaptic plasticity and memory hypothesis states that "activity-dependent synaptic plasticity is induced at appropriate synapses during memory formation and is both necessary and sufficient for the information storage underlying the type of memory mediated by the brain area in which that plasticity is observed." We outline a set of criteria by which this hypothesis can be judged and describe a range of experimental strategies used to investigate it. We review both classical and newly discovered properties of synaptic plasticity and stress the importance of the neural architecture and synaptic learning rules of the network in which it is embedded. The greater part of the article focuses on types of memory mediated by the hippocampus, amygdala, and cortex. We conclude that a wealth of data supports the notion that synaptic plasticity is necessary for learning and memory, but that little data currently supports the notion of sufficiency. Annu. Rev. Neurosci. 2000.23:649-711. Downloaded from arjournals.annualreviews.org by Iowa State University on 02/10/05. For personal use only. Annu. Rev. Neurosci. 2000.23:649-711. Downloaded from arjournals.annualreviews.org by Iowa State University on 02/10/05. For personal use only.
Neuropsychologia, 1989
This paper discusses certain issues connected with the question of whether synaptic plasticity is involved in information storage by the brain. We begin by contrasting two well documented types of synaptic plasticity--activity-dependent modulation of presynaptic facilitation ("Kandel synapses") and NMDA receptor triggered alterations in excitatory amino acid transmission ("Hebb synapses"). We then propose that, embedded-into appropriate circuitry, these different forms of plasticity might underlie different kinds of learning. In partial support of this idea, we show that, in freely moving rats, intrahippocampal microinfusion of the NMDA-receptor antagonist D,L-AP5 causes a dose-dependent impairment of a type of spatial learning known to be sensitive to disruption by hippocampal lesions (water-maze place-navigation). In a second experiment, the same drug infusion protocol is shown to cause a blockade of hippocampal long-term potentiation in vivo across a comparable dose range. Finally, third, autoradiographic experiments indicate that diffusion of the drug was largely restricted to the hippocampus. Together, these results (1) suggest that blockade of hippocampal NMDA receptors, under conditions which leave baseline synaptic transmission relatively unaffected, blocks a type of learning with which the vertebrate hippocampus has been implicated on the basis of neuropsychological work; and (2) supports Abrams and Kandel's Trends Neurosci. 11 (1988) recent proposal that there may be several logically distinct forms of synaptic plasticity.
The neurobiology of learning and memory
Cognition, 1989
We succeeded in taste avoidance conditioning with sucrose as the conditional stimulus (CS) and an electrical stimulus ($1000 V, 80 lA) as the unconditional stimulus (US). With 15 paired CS-US presentations on a single day, we were able to elicit both short-term memory (STM) and long-term memory (LTM) persisting for at least one week. However, while STM was elicited with 5, 8, 10, and 20 paired presentations of the CS-US on a single day, LTM was not. We found, however, that if we inserted a 3 h interval between a first and a second set of CS-US pairings that both 8 and 20 paired CS-US presentations on a single day was now sufficient to cause LTM formation. Exposing snails to bryostatin before or during training enhanced LTM formation such that 8 paired presentations of the CS-US resulted in LTM.
The brain decade in debate: I. Neurobiology of learning and memory
Brazilian Journal of Medical and Biological Research, 2000
This article is a transcription of an electronic symposium in which some active researchers were invited by the Brazilian Society for Neuroscience and Behavior (SBNeC) to discuss the last decade's advances in neurobiology of learning and memory. The way different parts of the brain are recruited during the storage of different kinds of memory (e.g., short-term vs long-term memory, declarative vs procedural memory) and even the property of these divisions were discussed. It was pointed out that the brain does not really store memories, but stores traces of information that are later used to create memories, not always expressing a completely veridical picture of the past experienced reality. To perform this process different parts of the brain act as important nodes of the neural network that encode, store and retrieve the information that will be used to create memories. Some of the brain regions are recognizably active during the activation of short-term working memory (e.g., prefrontal cortex), or the storage of information retrieved as long-term explicit memories (e.g., hippocampus and related cortical areas) or the modulation of the storage of memories related to emotional events (e.g., amygdala). This does not mean that there is a separate neural structure completely supporting the storage of each kind of memory but means that these memories critically depend on the functioning of these neural structures. The current view is that there is no sense in talking about hippocampusbased or amygdala-based memory since this implies that there is a oneto-one correspondence. The present question to be solved is how systems interact in memory. The pertinence of attributing a critical role to cellular processes like synaptic tagging and protein kinase A activation to explain the memory storage processes at the cellular level was also discussed.
Synaptic Plasticity and Learning Processes: A Neuroeducation Perspective
2020
The story of each individual is essentially the story of their learning processes and relationships from the moment they were born. Indeed, the story of learning processes is merely a constant stratification of experiences based on biological and neurofunctional features that are influenced by genetic and cultural factors and subject to environmental stimuli constantly reshaping their behaviour. Neuroscientific studies conducted over the past decades have highlighted a unique feature of the human nervous system, called neural plasticity which enables the development of beneficial or detrimental requirements for human health. From their birth, infants are inundated with plethora of stimuli, and their brains have to gradually connect these stimuli to something or someone, or assign them a meaning, so that the child will be able to interact with them in a consistent way at a later stage. All they are endowed with by nature makes up the biological features they need to relate to the surrounding world. Their sensory system enables infants to interpret environmental data and respond through motor sequences that get increasingly organized, allowing them to act appropriately in space through visual orientation. The presence of caregivers is a necessary condition for their survival, and also for the transmission of any type of explicit learning. Man cubs soon learn that each of their calls elicits a response aimed at satisfying all their needs. With time, this kind of experience will help them to trust the surrounding environment, and will significantly contribute to the development of their self-esteem. Therefore, when educational activity is imbued with this awareness, it becomes a neuro-educational activity, aimed at enhancing human cognitive skills through generalized (perception, motor skills, language) and educational (reading, writing, and computational skills) learning processes. These stimulate motor and manipulative activity and promote relationships, experiences, and social sharing. All of this by means of a slow and intense path of targeted stimulations that affect the lower levels of brain maturation.
Synaptic Plasticity. Stairway to Memory
The Japanese Journal of Pharmacology, 1995
Since the idea that memory is associated with alterations in synaptic strength was accepted, studies on the cellular and molecular mechanisms responsible for the plastic changes in neurons have attracted wide interest in the scientific community. Recent studies on memory processes have also pointed out some unifying themes emerging from a wide range of nervous systems, suggesting that regardless of the species or brain regions, a common denominator for memory may exist. Thus, the present review attempted to create a hypothetical and universal synaptic model valid for a variety of nervous systems, ranging from molluscs to mammals. The cellular and molecular events leading to short-and long-term modifications of memory have been described in a sequential order, from the triggering signals to the gene expression, synthesis of new proteins and neuronal growth. These events are thought to represent the late phases of memory consolidation leading to persistent modifications in synaptic plasticity, thereby facilitating the permanent storage of acquired information throughout the individual's life.
2002
SUMMARY One of the central issues in neuroscience is concerned with the activity-dependent synaptic plasticity in learning and memory. In such context, changing the strength of synaptic activity between neurons has been widely accepted as the mechanism responsible by which memory traces are encoded and stored in the brain. Thus, the synaptic plasticity and memory hypothesis (SPM hypothesis) shows that activity-dependent synaptic plasticity is induced at appropiate synapses during memory formation, which is essential for information storage for the type of memory involved in the brain area where plasticity is detected or observed. Several criteria and experimental strategies are outlined, and used to investigate this hypothesis. Long-term potentiation (LTP) as an experimental model to study the cellular basis of learning and memory, is one of the most fascinating phenomena that have raised a great interest in neuroscience. LTP is a form of synaptic plasticity that is accepted as a ce...