Sensory learning and memory formation Flashcards Preview

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1

sensory learning and memory formation (Clark, 2017)

Here, I provide a basic history of important milestones in the development of theories for how the brain accomplishes the phenomenon of learning and memory. Included are the ideas of Plato, René Descartes, Théodule Ribot, William James, Ivan Pavlov, John Watson, Karl Lashley, and others. The modern era of learning and memory research begins with the description of H.M. by Brenda Milner and the gradual discovery that the brain contains multiple learning and memory systems that are supported by anatomically discrete brain structures. Finally, a brief overview is provided for the chapters that are included in current topics in Behavioral Neuroscience—Learning and Memory.

see notes

2

learning and memory

• Changes in behaviour or emergence of responses that are caused by previous experience
○ Not proof of learning
○ How info is acquired - recalling memories
• Observations:
○ Behav (actions, emotions, knowledge due to experience)
○ Neurons (neural network activity)
○ Synapses (interactions between indv neurons, synaptic plasticity)
§ Learn = change at level of synapse
○ Regulatory and structural genes ((de-)activation, modulation of expression patterns)
§ Build proteins
§ Turn genes on/off - transcription factors - genomic cascades
- Grow more synapses - activate genes

see notes

3

different forms of learning

• Learning is the process of acquiring new info
• Memory is the ability to store and retrieve info- without this hard to prove learning - decay also important feature - extinction
- Non-associative learning: habituation, sensitisation
- Associative learning: classical and operant conditioning
○ Imprinting
○ Observational learning: imitation, stim enhancement, social learning
- Tool use, play, latent learning, insight, view-based navigation

4

When does the environment start to influence behavioural development?

• Innateness (fixed/inflexible - cannot unlearn response or learn v. easily) - genetically determined, inherited, unlearned behav actions/responses - vs learning: the nature-nurture fallacy - dichotomy - less relevant now than before - cut off point is birth
• Can have diff types of learning - when, how, diff mechanisms
• Env effects present in some form
• Chickens and ducks can vocalise days before hatching
- Can get light through shell

see notes


- Animals learn before sensory systems mature enough - sustained throughout birth

5

When does the environment start to influence behavioural development? research

Barbarin et al. (2019)

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Barbarin et al. (2019)

Black males experience extraordinary developmental risks as a consequence of the combined effects of male gender, poverty, and race. These risks are reflected in atypical behavioral and emotional development often observed in middle childhood. Not all Black males succumb to these risks. Whether or not they do is a function of exposure to adverse childhood events resulting from poverty, the experience of racial bias, and access to mitigating cultural resources and familial supports. Reducing household poverty and increasing access to early childhood programs, school-based programs, and mentoring are promising interventions to increase the probability of positive outcomes.

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Selective breeding of 'bright' and 'dull' rats for solving a maze task (Tryon, 1940, 1942)

• Artificial selection exp on maze-running ability in rats
• Are maze-bright rats more intelligent than maze-dull rats?
• Variation across individuals
- Clear dichotomy in perf

see notes

• Intelligence can be inherited - genes involved - cannot live without - always active - nothing happens without genes
• How do genes and env interact
- Animals can perform in complicated experiments - small brains - tasks solved in many ways

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Selective breeding of 'bright' and 'dull' rats for solving a maze task (Tryon, 1940, 1942) research

Markowitz and Sorrells (1969)

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Markowitz and Sorrells (1960)

Twenty-five descendants of the Berkeley S 1 and S 3 strains of animals were tested in an automated discrimination apparatus with shock as reinforcement. On the four successive ligltt-co"ect and clark-co"ect problems presented, the S3 ("maze-dull") animals were superior. Some tentative interpretations of the results are presented. It is suggested that the labels "maze-bright" and "maze-dull" are inexplicit and inappropriate for use with these strains.

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Environmental conditions can mask genetic differences and produce similar phenotypes (Drickamer et al., 2002)

• Enriched env improved perf of maze-dull rats
• Cooper and Zubeck (1958)
• Does genotypic variance matter for the behav of rats?
○ Depends on type of env - experience, nutrition
- Challenged original exp

see notes

• Diffs less clear - distributed equally in both strains - env caused diff - most strong genetic effects - that string is can be masked?
- Interaction and how - always

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Environmental conditions can mask genetic differences and produce similar phenotypes (Drickamer et al., 2002) research

Ravindran et al. (2020)

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Ravindran et al. (2020)

Phenotypic variation plays an important role in how species cope with environmental challenges. Pinpointing which genes and genomic regions are underlying phenotypic variability thus helps to understand the processes of acclimation and adaptation. We usedDaphniaas a system to identify candidates playing a role in phenotypic variation related to a predation risk environment with a genome-wide association approach. Furthermore, a gene co-expression network analysis allowed identifying clusters of co-expressed genes which correlated to life history traits. To enhance the understanding of the functional roles of the transcripts, we identified orthologs and paralogs from related species and used ontologies to annotate the candidates of interest. Our study revealed that only one life history trait and two morphometric traits have a genetic association in the presence of predation risk (fish kairomones), whereas most genotype-phenotype associations were detected in a genotype-environment interaction analysis for reproduction-related phenotypic traits. The gene co-expression network analysis identified a total of 44 modules, of which one module correlated to another life history trait namely the 'total number of broods'. The combined use of gene co-expression network and transcriptome-wide association analysis allowed the identification of 131 candidate transcripts associated with life history traits inDaphnia galeata. These results lay the ground for targeted studies to further understand phenotypic variability in this species.

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Are there specialised areas in the brain for storing memories? (Squire and Kandel, 2000)

• Lashley's search for memory 'engrams' (1929, 1950)
• Lesion studies with rats
Lashley concluded that memory not located in particular areas of rat cortex

see notes

• No specific area
• Remove cortex
• Go through maze
• Which parts of brain responsible for diff types of memory?
- Diff areas removed didn't matter - still errors

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Are there specialised areas in the brain for storing memories? (Squire and Kandel, 2000) research

Lashley (1929, 1950)

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Lashley

A review of the experimental evidence on neural mechanisms in learning and memory leads to conclusions: (1) "the theory of well-defined conditional reflex paths" is mistaken; (2) there is no demonstrable localization of a memory trace; (3) "associative areas" are not storehouses for memories; (4) "the trace of any activity is not an isolated connexion between sensory and motor elements"; (5) cortical equivalence indicates multiple representation of memories; (6) since all brain cells are constantly active, "no great excess of cells… can be reserved as the seat of special memories."

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Different brain regions are involved in learning and memory (Squire, 2004; Clark, 2019)

• Subcortical (hippocampus, brainstem) areas play imp role in memory formation and recall
- Lesion studies

see notes

• Reflex pathways - brainstem
- Not all cortex - not reflection of intelligence

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Different brain regions are involved in learning and memory (Squire, 2004; Clark, 2019) research

Squire (2004)

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Squire (2004)

The idea that memory is composed of distinct systems has a long history but became a topic of experimental inquiry only after the middle of the 20th century. Beginning about 1980, evidence from normal subjects, amnesic patients, and experimental animals converged on the view that a fundamental distinction could be drawn between a kind of memory that is accessible to conscious recollection and another kind that is not. Subsequent work shifted thinking beyond dichotomies to a view, grounded in biology, that memory is composed of multiple separate systems supported, for example, by the hippocampus and related structures, the amygdala, the neostriatum, and the cerebellum. This article traces the development of these ideas and provides a current perspective on how these brain systems operate to support behavior.

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Learning and memory: Network level

• Learning and memory changes as age
• Newly born neurons (neurogenesis) may aid learning
- Area of encoding and recall diff - shift in brain areas

see notes

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Learning and memory: Network level research

Creighton et al. (2020)

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Creighton et al. (2020)

The neuronal epigenome is highly sensitive to external events and its function is vital for producing stable behavioral outcomes, such as the formation of long-lasting memories. The importance of epigenetic regulation in memory is now well established and growing evidence points to altered epigenome function in the aging brain as a contributing factor to age-related memory decline. In this review, we first summarize the typical role of epigenetic factors in memory processing in a healthy young brain, then discuss the aspects of this system that are altered with aging. There is general agreement that many epigenetic marks are modified with aging, but there are still substantial inconsistencies in the precise nature of these changes and their link with memory decline. Here, we discuss the potential source of age-related changes in the epigenome and their implications for therapeutic intervention in age-related cognitive decline.

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Decline of cell proliferation with chronological age (Amrein, 2015)

• Possibly function in
○ Repair
○ Plasticity
• End of old dogma: new neurons can be born in adult brain - not across whole brain
Occurrence of neurogenesis declines over time and as age increases plasticity and repair decrease

see notes

23

Decline of cell proliferation with chronological age (Amrein, 2015) research

Kempermann et al. (2015)

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Kempermann et al. (2015)

Of the neurogenic zones in the adult brain, adult hippocampal neurogenesis attracts the most attention, because it is involved in higher cognitive function, most notably memory processes, and certain affective behaviors. Adult hippocampal neurogenesis is also found in humans at a considerable level and appears to contribute significantly to hippocampal plasticity across the life span, because it is regulated by activity. Adult hippocampal neurogenesis generates new excitatory granule cells in the dentate gyrus, whose axons form the mossy fiber tract that links the dentate gyrus to CA3. It originates from a population of radial glia-like precursor cells (type 1 cells) that have astrocytic properties, express markers of neural stem cells and divide rarely. They give rise to intermediate progenitor cells with first glial (type 2a) and then neuronal (type 2b) phenotype. Through a migratory neuroblast-like stage (type 3), the newborn, lineage-committed cells exit the cell cycle and enter a maturation stage, during which they extend their dendrites into a the molecular layer and their axon to CA3. They go through a period of several weeks, during which they show increased synaptic plasticity, before finally becoming indistinguishable from the older granule cells.

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Adult neurogenesis in both vertebrate and invertebrate brains (Barker et al., 2011)

• Fish, amphibia: neurogenic cells in many brain areas
• Reptiles, birds mammals (more concentrated than fish and amphibia): neurogenesis largely in lateral ventricles and hippocampus (mammals) - cells migrate throughout telencephalon (olfactory bulb, HVC)
• CB - cerebellum
• OB - olfactory bulb
• V - lateral ventricles
• HVC (RA only in songbirds) - cerebral nuclei
- Hp - hippocampus

see notes

26

Adult neurogenesis in both vertebrate and invertebrate brains (Barker et al., 2011) research

Galed (1984)

Gross (2000)

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Galed (1984)

○ "Field observations can point to areas in which organisms express special competences, suggesting the existence either of refinements of known learning processes or previously unsuspected learning mechanisms
○ Lab investigations of plasticity can expand (/limit) the range of acceptable proximal explanations of changes in behav observed in field
Field studies direct lab research on animal learning toward fruitful areas of investigation, while lab research can provide assistance to field workers in understanding the behav and neurobiological mechanisms that might be responsible for acquisition or development of adaptive responses"

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Gross (2000)

For over 100 years a central assumption in the field of neuroscience has been that new neurons are not added to the adult mammalian brain. This perspective examines the origins of this dogma, its perseverance in the face of contradictory evidence, and its final collapse. The acceptance of adult neurogenesis may be part of a contemporary paradigm shift in our view of the plasticity and stability of the adult brain.

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Can adult hippocampal neurogenesis be linked to the environmental conditions a species lives in? (Cavegn et al., 2013)

• Mole rats live in subterranean tunnel system
- Amongst surface-dwelling rodents, SA rodents live in challenging habitat

see notes

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Can adult hippocampal neurogenesis be linked to the environmental conditions a species lives in? (Cavegn et al., 2013) research

Burger et al. (2014)