Discussion 20 Flashcards
(28 cards)
staining
Scientists can stain sections of brain tissue
to identify cell bodies in the brain viewed with a light microscope, and they can selectively stain individual neurons to reveal their complete structure. An electron microscope makes it possible to view synapses in detail. Multiphoton
imaging can generate a three-dimensional image of living
tissue
studying neurons
Contemporary techniques allow researchers to identify molecular, neurochemical, and morphological (structural) differences among neuronal types and ultimately to relate these characteristics to behavior. We have even miniaturized microscopes to the point where they can be
mounted on the head of a mouse. These miniscopes can detect dozens to hundreds of neurons simultaneously by imaging a fluorescent signal activated by the neurons’ calcium levels, which indicate firing activity,
while the mouse is navigating around an environment
corisi block tapping test
The Corsi block-tapping test shown in
requires participants to observe an experimenter tap a sequence of
blocks—blocks 4, 6, 1, 8, 3, for instance. The task is to repeat the
sequence correctly. The participant does not see numbers on the blocks
but rather must remember the locations of the tapped blocks
mirror drawing
The mirror-drawing task (Figure 7-2B) requires a person to trace a
pathway, such as a star, by looking in a mirror. This motor task initially
proves difficult because our movements appear backward in the mirror.
With practice, participants learn how to accomplish the task accurately,
and they show considerable recall of the skill when retested days later.
Curiously, patients with certain types of memory problems have no
recollection of learning the task on the previous day but nevertheless
perform it flawlessly.
Recency Memory Task
participants are shown a
long series of cards, each bearing two stimulus items that are words orc pictures. On some trials, a question mark appears between the items.Their task is to indicate whether they have seen the items before and, ifso, which item they saw most recently. They might be able to recall that
they have seen items before but may be unable to recall which was most recent. Conversely, they might not be able to identify the items as being familiar, but when forced to choose the most recent one, they may be
able to identify it correctly.The latter, counterintuitive result reflects the need for behavioral researchers to develop ingenious ways of identifying memory abilities.
It is not enough simply to ask people to recall information verbally, although this too measures a form of memory
the Moris water task
Rats are placed in a large swimming pool
with high slippery walls that do not allow the rats to escape. A hidden platform lies just below the water surface. Rats are terrific swimmers, and they quickly navigate around the pool until they bump into the platform. They learn that when they climb onto the platform, they are removed from the pool and returned to their home cage—their preferred
place
place learning task
he rat must find the
platform from a number of different starting locations in the pool. The only cues available are outside the pool, so the rat must learn the relationship between several cues in the room and the platform’s location
Matching-to-place task
the rat has already learned that a platform always lies somewhere in the pool, but the rat enters the pool from a different starting location every day. The rat is released and searches for the platform Once the rat finds the platform, the rat is removed from the pool and, after a brief delay (such as 10 seconds), is released again. The rat’s task is to
swim directly to the platform. The challenge for the rat in the matching to-place test is to develop a strategy for finding the platform consistently: it is always in the same location on each trial each day, but
each new day brings a new location
landmark
version of the task, the platform’s location is identified by a cue on the pool wall . The platform moves on every trial, but the relationship to the cue is constant. In this task, the
brain is learning that the distant cues outside the pool are irrelevant;
only the local cue is relevant. Rats with different neurological
perturbations are selectively impaired in the three versions of the
swimming pool task
The Skilled Reaching Task (Whishaw & Kolb, 2005).
details how a rat orients its body to
the slot (shown in panel A), puts its hand through the slot
rotates the hand horizontally to grasp the food and rotates the hand vertically and withdraws it to obtain the food . Primates are not the only animals to make fine digit movements, but because the
rat’s hand is small and moves so quickly, digit dexterity can be properly observed only during slow-motion video playback
why asses brain and behavior modifications
- A predominant strategy for studying brain–behavior relationships is to manipulate some aspect of brain function and see how behavior changes. Investigators do so to develop hypotheses about how the brain affects behavior and to test those hypotheses
- A second reason to manipulate the brain is to develop animal models of neurological and psychiatric disorders. The general presumption in neurology and psychiatry is that it ought to be possible to restore at least some healthy functioning by pharmacological, behavioral, or other
interventions. A major hurdle for developing such treatments is that, like most other new medical treatments, they must be tested in nonhuman subjects first.
lesions
The first—and the simplest—technique used for brain manipulation is
to ablate (remove or destroy) tissue.
Neurotoxic lesion
produced by the infusion of a chemical that
selectively targets neurons or specific types of neurons
high-intensity focused ultrasound
(HIFU)
can now achieve the same result without the invasive surgery Focused ultrasound uses many individual
ultrasonic beams that are all pointed at the same spot in the brain. Each beam passes through tissue with little effect; at the convergent point where all the beams intersect, the energy heats the tissue. Lightly heating the tissue temporarily prevents that part of the brain from working properly, thereby informing the surgeons that their targeting is correct. The tissue heating can then continue until the target is permanently destroyed and the tremor is noninvasively eliminated.
compensation
the neuroplastic ability to modify behavior from that used prior to the damage.
temporary lesion techniques
A hollow metal coil is placed next to a neural structure;
then chilled fluid is passed through the coil, cooling the brain structure. When the chilled fluid is
removed from the coil, the brain structure quickly warms, and synaptic transmission is restored. Another technique involves local administration of a GABA agonist, which increases local inhibition and in turn prevents the brain structure from communicating with other
structures. Degradation of the GABA agonist reverses the local inhibition and restores function.
Reversable, inactivating a part of the brain
electrical self-stimulation.
Rats with electrodes placed in the lateral hypothalamus will eat whenever the stimulation is turned on. If the animals have the opportunity to press a bar that briefly turns on the
current, they quickly learn to press the bar to obtain the current,
deep brain stimulation
is a neurosurgical technique. Electrodes implanted in the brain stimulate a targeted area with continuous pulses of low-voltage electrical current to facilitate behavior
transcranial magnetic stimulation
During a treatment session, a small wire coil isplaced adjacent to the skull, as illustrated in A highvoltage current pulsed through the coil produces a rapid increase and
subsequent decrease in the magnetic field around the coil. The magnetic field easily passes through the skull and causes a population of neurons in the cerebral cortex to depolarize and fire. used either to induce behavior or to disrupt ongoing behavior.
optogenetics
combines genetics and light to control targeted cells in living tissue. A sequence that codes for a light-sensitive protein associated with an ion channel enables nvestigators to use light to change the shape (conformation) of the channel
chemogenetics
the inserted synthetic genetic sequence codes for a G protein–coupled receptor engineered to respond exclusively to a synthetic small-molecule “designer drug.”
Transgenic technique that
combines genetics and synthetic drugs to activate targeted cells in living tissu
DREADD
DREADD (designer receptor exclusively activated by designer drugs). Its principal advantage is that the drug activates only the genetically modified receptors, and the receptors are activated only by the designer drug, not by endogenous molecules Thus, specificity is high, but temporal resolution is much lower than with optogenetics because receptors are activated by drugs rather than by
light. nsert a receptor that responds to a biological inert substance (clozapine N-oxide, CNO) Can excite or inhibit neurons
what are the four major techniques for
tracking the brain’s electrical activity
are single-cell recording, electroencephalography (EEG), event-related potentials (ERPs), an magnetoencephalography (MEG).
electrical acitvity
it was becoming possible to record the activity of individual
cells by measuring a single neuron’s action potentials with fine electrodes inserted into the brain. These microelectrodes can be placed next to cells (extracellular recording) or inside cells (intracellular recording). Modern extracellular recording techniques make it possible to distinguish the activity of as many as 40 neurons at once. Intracellular recording allows direct study and recording of a
single neuron’s electrical activity. The two disadvantages of inserting an electrode into a cell are that (1) it can kill the cell, and (2) it cannot be done in awake, freely moving animals. Single-cell recording is therefore confined to neurons grown in a dish or, for short periods
(hours), to neurons in living brain slices
