Chapter 3B: Neurogenetics of Learning and Memory Flashcards
What is an adaptive behavior?
that which increases an organisms ability to survive & reproduce
What are evolutionary time scales?
selection of genetically-dependent behaviors which confer reproductive advantages
What are life-time scales?
ability to modify behavior (learning and memory)
over a lifetime
What are genes?
segments of DNA
code for particular proteins: the construction and operational molecules of biological systems
capable of affecting behavior
What is the influence of genetics and heredity on expression of adaptive behavior?
given that behavior is a function of physiology, and the physiology is a function of genetics, it stands to reason that behavior in general, and adaptive behavior specifically, would be influenced by genetic makeup
What are two possible ways in which genetic material could be important for learning and memory?
- through the production of intracellular machinery necessary for the expression of behavioral/neural modifications; learning (short term processes)
- through a moment to moment regulation of factors necessary to maintain behavioral/neural modifications; memory (long-term processes)
What is the historical rationale for using Drosophila in a study?
well used as a genetic model
genetic simple, known
four chromosomes
genome completely sequenced
What is the practical rationale for using Drosophila in a study?
cheap and easy to keep
small animal, short life cycle, rapid generational time & development
mutants easy to make
many already exist
What is the behavioral rationale for using Drosophila in a study?
rich behavioral repertoire
species specific
adaptive behavior
What is a potential problem with using Drosophila in a study?
however, comparative insect anatomy in addition to more sophisticated genetic techniques have allowed for a better understanding of learning circuits
What are the two questions regarding learning and memory in Drosophila?
how can learning in Drosophila be studied?
what kinds of learning can Drosophila exhibit?
What are the species specific behaviors of Drosophila?
photo/olfacto-taxis (like to move toward light or the smell of food)
feeding/cleaning reflexes
courtship/mating
What is the learning observed from Drosophila?
habituation
sensitization
classical conditioning
operant conditioning
What was the experiment where Drosophila were classically conditioned to avoid smells?
all flies are exposed to two odours - one which is paired with shock
given a later choice between the two odours, most flies pick the one which was not paired with shock
What is the learning index?
fraction of flies avoiding shock-paired odorant minus fraction of flies avoiding unpaired odorant
0.9 for normal flies (i.e. 95% of flies avoided paired smell)
How can memory itself be assessed?
short term vs. long term
spaced vs. massed training
consolidation
What are the steps involved in isolating a “genetic learning mutant”?
- mutagenesis (chemical, irradiation, genetic manipulation)
- breed mutants (isogenic population)
- test mutants for learning/memory abnormalities (test mutants for behavioral, morphological, or developmental abnormalities)
- map affected gene
- clone gene
What are the three possibilities of how genetic abberations could affect learning?
- activity of gene product directly relevant for cellular processes of learning
- activity of gene product secondarily related to cellular processes involved in learning
- altered development of nervous system - missing cells or circuits contribute to learning deficit
What are some examples of known learning mutant genes?
dunce (dnc)
amnesiac (amn)
rutabaga (rut)
turnip (tur)
dopa decarboxylase (Dcd)
What are the learning deficits associated with the mutant genes?
reduced performances in different learning tasks: habituation and sensitization of feeding reflex, naturalistic learning (courtship), instrumental conditioning, olfactory classical conditioning (avoidance)
early memory phase is primarily affected (acquisition/learning, short term memory)
What is the defect in 2nd messenger systems associated with the mutation dnc?
defective cAMP phosphodiesterase (tonically elevated cAMP - product of adenyl cyclase activation)
What is the defect in 2nd messenger systems associated with the mutation amn?
reduction in a peptide activator of adenyl cyclase
What is the defect in 2nd messenger systems associated with the mutation rut?
impairs Ca2+-dependent calmodulin activation of adenyl cyclase
What is the defect in 2nd messenger systems associated with the mutation tur?
reduces PKC function & activation of adenyl cyclase by g-proteins
