Chapter 9

What are some of the methods neurobiologists use to influence brain function?

-Experimentally damaging a particular region of the brain. -Injecting drugs into the brain that are designed to influence some aspect of neural function. -Genetic engineering to increase or decrease the expression of some potential memory molecule.

What are the three most prevalent Behavioral Test Methods for Studying Memory?

-Inhibitory avoidance conditioning -Fear conditioning -Spatial learning in water-escape task

What are some of the many different component processes that make up measurable behavior? How do they effect the study of memory?

-Sensory, attention, and perceptual processes determine what the subject experiences at the time of training and testing. -Motivational processes determine the subjects willingness to initiate a response. -Emotional processes can interfere with the subjects ability to access stored information. -Motor systems provide the basis for the behavioral response to be expressed. -A memory system that stores the experience.

What are two important attributes of the inhibitory avoidance conditioning?

1. Only one training trial is required to produce a memory. 2. The rodent's crossover latency is quite sensitive to the shock. (as shock intensity increases, the latency to crossover also increases)

What is the fear conditioning method?

A rat is allowed to explore the conditioning context. An auditory tone is presented for about 15 seconds, and a shock is delivered when the tone terminates. Rats are then tested for their fear of the context-place where the shock occurred, and later for their fear of the tone. Shocked rats display more freezing than rats that are not shocked. (the duration of freezing is an indicator of the strength of the memory).

Describe the inhibitory avoidance conditioning.

A rat is placed on a bright side of an apparatus. When it crosses over to the dark side, it receives a shock across it's feet. To assess the memory for this experience, the rat is again placed in the bright end, and the crossover latency is measured (time it takes to cross to dark side).

Describe the Place-Learning Task

A small platform is hidden in a circular swimming pool just below the surface of the water. The rodent is placed into the pool and allowed to swim a long distance on the first trial before it locates the platform (after several trials, it learns to swim directly to the platform). Escape latency decreases as a function of training trials where the rat is placed back into the pool at a different spot.

Annulus crossings

Annulus crossings are a measure of the place learning in the Morris water escape task based on how many times during the probe trial the animal actually crosses the exact place where the platform was located during training compared to how many times it crosses the equivalent area in other quadrants.

Channelrhodopsin

Channelrhodopsins can be activated by blue light to conduct positive ions and depolarize the neuron.

What are the CR, US, and CS in fear conditioning?

Conditioned Response (CR): Freezing Unconditioned Stimulus (US): Electrical Shock Conditioned Stimulus (CS): Auditory cue

How is ECS used in the study of memory?

ECS is used to experimentally produce amnesia.

What is freezing?

Freezing is an innate defense response observed in rodents. In the presence of danger, rodents instinctively become still.

What are the benefits of genetic engineering?

Genetic engineering permits much more precise targeting of specific molecules that might play a role in making memories (drugs are not selective and often have unintended consequences). A given gene can be turned off for some period of time during development and then turned back on so that the researcher can study the same animal with the particular gene knocked out, or with that gene functioning.

Halorhodopsin

Halorhodopsins can be stimualted with green light to conduct negatively charged chloride ions and thereby hyperpoalrize the neuron.

What is the ceiling effect? When should you worry about the ceiling effect?

If the response measured is at it's maximum, there is no way to see the influence of another manipulation. Worry about the ceiling effect when investigating a drug or some other manipulation that is hypothesized to strengthen a memory trace (use a low intensity shock).

How was ECS used in the past?

In the 1930s, Ugo Cerletti and Lucio Bini used ECS to treat psychiatric disorders.

Opsins

Opsins are genes that encode for proteins that respond to light to regulate the flow of ions across the membrane.

What is optogenetics? What problem does it solve?

Optogenetics is a methodology that combines genetic engineering with optics. A fundamental challenge of brain science is to identify the specific neurons and their contribution to basic brain functions. Optogenetics allows scientists to control one type of cell without altering other types.

Quadrant search time

Quadrant search time is a measure of place learning in the Morris water escape task where the pool is divided conceptually into 4 equal quadrants. During training, the platform is in one quadrant. A rodent that has stored a memory of the location of the platform will spend more of its search time in the quadrant than it will in the other quadrants.

Describe the learning-performance distinction

Researchers have been able to show that the brain manipulation in their experiment influenced behavior by selectively influencing the unobservable memory component and not by affecting some other component process. The place learning VS visible-platform task.

Retrieval failure

Retrieval failure is when the agent that produces amnesia disrupts the neural pathways that enable the memory to be retrieved. Implication is that the memory is lost temporarily. (ex: forgetting location of book only to later remember)

Describe how short term memory traces are different from long term memory traces.

Short term memory is an active state that leads to rapid decay and is vulnerable to disruption. Long term memory is more stable, in an inactive state, has slow decay, and is less vulnerable to disruption.

Storage Failure

Storage failure is when the agent that produces amnesia interferes with the processes responsible for storing the memory. Implication is that events experienced prior to trauma will never be remembered. (ex: blow to the head)

What are consolidation processes?

Synaptic consolidation occurs within the first few hours after learning. System consolidation is where hippocampus dependent memories become independent of the hippocampus over a period of weeks or years.

What is the basic paradigm used in all studies of learning and memory?

The basic paradigm used in all studies of learning and memory is that all experimental investigations of memory require a training phase to establish a memory and a test phase to detect the memory.

What is the consolidation period?

The consolidation period is the time it takes to achieve the outcome of a less vulnerable memory trace.

Path length

The distance the rodent swims before finding the platform.

What are some advantages to using fear conditioning?

The fear conditioning method allows the experimenter to have precise control over the intensity of the CS and US, the time separating the CS and the US, and the number of training trials.

What is the floor effect? When should you worry about the floor effect?

The performance measure is too low to be further reduced by the drug. Worry about the floor effect when the treatment is hypothesized to impair the memory processes that produce avoidance behavior (use a somewhat higher level of shock to produce a long latency).

Probe trial

The platform is removed from the pool and the rodent is placed in the pool and allowed to search for it. A camera captures the rodent's performance and the experimenter can collect info about where the rodent swims. Probe trials are used to further asses the rodent's memory for the location of the platform.

What is the window to the memory trace?

The test behavioral change that is observed from experimental investigations acts as a window into the memory trace. The existence of a memory trace is inferred with the training experience influences behavior.

Escape Latency

The time it takes the rat to find the hidden platform.

What is the viral vector system and how is it used?

The viral vector system is the use of viruses to deliver new genetic material into specific cells. Viruses can be modified to deliver desired genes into host cells. . This is accomplished by deleting some or all of the coding regions of the viral genome and replacing them with a genetic construct that contains the desired new genetic material - the vector genome - and additional genetic elements that control the expression of the gene. This is called a promoter sequence. When the virus is injected into target neurons, the vector genome will then be expressed.

What is the purpose of the visible-platform task?

The visible platform task is used as a control to evaluate alternative interpretations of the effect of some brain manipulations on performance in the place-learning task.

What is memory consolidation?

With the passage of time, resistance to memory disruption increases and the trace becomes more stable. The term memory consolidation describes this change from vulnerable to less vulnerable.