Chapter 3B: Neurogenetics of Learning and Memory

Question 1

What is an adaptive behavior?

Answer 1

that which increases an organisms ability to survive & reproduce

Question 2

What are evolutionary time scales?

Answer 2

selection of genetically-dependent behaviors which confer reproductive advantages

Question 3

What are life-time scales?

Answer 3

ability to modify behavior (learning and memory)
over a lifetime

Question 4

What are genes?

Answer 4

segments of DNA

code for particular proteins: the construction and operational molecules of biological systems

capable of affecting behavior

Question 5

What is the influence of genetics and heredity on expression of adaptive behavior?

Answer 5

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

Question 6

What are two possible ways in which genetic material could be important for learning and memory?

Answer 6

1. through the production of intracellular machinery necessary for the expression of behavioral/neural modifications; learning (short term processes)
2. through a moment to moment regulation of factors necessary to maintain behavioral/neural modifications; memory (long-term processes)

Question 7

What is the historical rationale for using Drosophila in a study?

Answer 7

well used as a genetic model

genetic simple, known

four chromosomes
genome completely sequenced

Question 8

What is the practical rationale for using Drosophila in a study?

Answer 8

cheap and easy to keep

small animal, short life cycle, rapid generational time & development

mutants easy to make
many already exist

Question 9

What is the behavioral rationale for using Drosophila in a study?

Answer 9

rich behavioral repertoire

species specific

adaptive behavior

Question 10

What is a potential problem with using Drosophila in a study?

Answer 10

however, comparative insect anatomy in addition to more sophisticated genetic techniques have allowed for a better understanding of learning circuits

Question 11

What are the two questions regarding learning and memory in Drosophila?

Answer 11

how can learning in Drosophila be studied?

what kinds of learning can Drosophila exhibit?

Question 12

What are the species specific behaviors of Drosophila?

Answer 12

photo/olfacto-taxis (like to move toward light or the smell of food)

feeding/cleaning reflexes

courtship/mating

Question 13

What is the learning observed from Drosophila?

Answer 13

habituation
sensitization
classical conditioning
operant conditioning

Question 14

What was the experiment where Drosophila were classically conditioned to avoid smells?

Answer 14

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

Question 15

What is the learning index?

Answer 15

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)

Question 16

How can memory itself be assessed?

Answer 16

short term vs. long term

spaced vs. massed training

consolidation

Question 17

What are the steps involved in isolating a “genetic learning mutant”?

Answer 17

1. mutagenesis (chemical, irradiation, genetic manipulation)
2. breed mutants (isogenic population)
3. test mutants for learning/memory abnormalities (test mutants for behavioral, morphological, or developmental abnormalities)
4. map affected gene
5. clone gene

Question 18

What are the three possibilities of how genetic abberations could affect learning?

Answer 18

1. activity of gene product directly relevant for cellular processes of learning
2. activity of gene product secondarily related to cellular processes involved in learning
3. altered development of nervous system - missing cells or circuits contribute to learning deficit

Question 19

What are some examples of known learning mutant genes?

Answer 19

dunce (dnc)
amnesiac (amn)
rutabaga (rut)
turnip (tur)
dopa decarboxylase (Dcd)

Question 20

What are the learning deficits associated with the mutant genes?

Answer 20

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)

Question 21

What is the defect in 2nd messenger systems associated with the mutation dnc?

Answer 21

defective cAMP phosphodiesterase (tonically elevated cAMP - product of adenyl cyclase activation)

Question 22

What is the defect in 2nd messenger systems associated with the mutation amn?

Answer 22

reduction in a peptide activator of adenyl cyclase

Question 23

What is the defect in 2nd messenger systems associated with the mutation rut?

Answer 23

impairs Ca2+-dependent calmodulin activation of adenyl cyclase

Question 24

What is the defect in 2nd messenger systems associated with the mutation tur?

Answer 24

reduces PKC function & activation of adenyl cyclase by g-proteins

Question 25

What is the defect in 2nd messenger systems associated with the mutation Ddc?

Answer 25

decreased dopamine and 5-HT levels (another potential substrate for adenyl cyclase activation)

Question 26

What is the reverse genetic approach?

Answer 26

transgenic: gene insertion
knock-out: gene deletion

example: CREB (implicated in LTM in Aplysia, Drosophila and Mouse)

Question 27

What are the similarities between Drosophila and Aplysia in regards to LTP?

Answer 27

adenyl cyclase/cAMP/PKA:MAPK pathway

calcium calmodulin dependent kinase

do these systems constitute elemental cellular building blocks for learning/memory?

common evolutionary development of short-term and long-term processes