NEU 3200 Exam 3

functional roles of the basal ganglia

initiation, modulation, and termination of output to motor cortex

eye movements, learning of routine behaviors (habits), reward associated behaviors, may play a role in complex thought and reasoning

basal ganglia

important component of the motor system, essential for learning and execution of automatic action

caudate nucleus, putamen, globus pallidus

corticostriatal pathway

collective term for all cortical projections to the striatum

cerebral cortex —> striatum

input zone

striatum: caudate, putamen

striatum

gets its name because of the striped appearance from white matter fibers running between the caudate and putamen

medium spiny neurons

90% of neurons in striatum

divergence of inputs from corticostriatal axons allows a single one to integrate the influence of many cortical cells

output zone

globus pallidus externus and globus pallidus internus/substantia nigra pars reticulata

globus pallidus externus

tonically active GABAergic neurons that project to the subthalamic nucleus

tonically active

neurons fire constantly until inhibited

globus pallidus internus/substantia nigra pars reticulata

tonically active GABAergic neurons that project to the thalamus

subthalamic nucleus

located ventral to the thalamus

a glutamatergic nucleus receiving projections from the GPe and projects to the GPi/SNr

glutamatergic nucleus

contains cell bodies of glutamatergic neurons

substantia nigra

a midbrain structure

parkinson’s disease

substantia nigra pars compacta (SNc)

dopaminergic cells closely compacted together; modulate striatum

substantia nigra pars reticulata (SNr)

GABAergic cells (tonically active) that are the other major output zone of the basal ganglia

direct pathway

allows for initiation of movement when cortical activation of striatal medium spiny neurons that project to GPi/SNpr is sufficient to disinhibit the VA/VL complex of the thalamus

cerebral cortex —> striatum —> globus pallidus internus —> thalamus —> frontal cortex

excitatory

indirect pathway

antagonizes the activity of the direct pathway, resulting in termination of movement by increasing activity of the GPi/SNpr and enhancing the inhibition of the thalamus

cerebral cortex —> striatum —> globus pallidus externus —> subthalamic nucleus —> globus pallidus internus —> thalamus —> frontal cortex

inhibitory

disinhibition

inhibition of an inhibitory neuron; results in removal of inhibition and an increase in the degree of excitation

excitatory D1 dopamine receptors

when dopamine is released from the SNc, there is an excitation of these striatal neurons

inhibitory D2 dopamine receptors

when dopamine is released from the SNc, there is an inhibition of these striatal neurons

hyperdirect pathway

inhibitory (emergency brake)

parkinson’s disease

loss of dopaminergic neurons in substantia nigra

resting tremor

huntington’s disease

degeneration of GABA-ergic neurons in the caudate nucleus and putamen affecting external globus pallidus

hemiballismus

basal ganglia syndrome resulting from the damage to the subthalamic nucleus

typically restricted to one side

hypokinetic movement disorder

inability to initiate movements at a normal rate of speed

akinesia

no movement

bradykinesia

slow movements

rigidity

increased muscle tone

dyskinesia

involuntary movement

chorea

to dance

ballism

wild flailing

learning

process by which experiences change our nervous system and hence our behavior

it allows us to respond to behavioral changes and act appropriately (appropriate behavior in appropriate situation)

durable and usually adaptive change in an animal behavior traceable to a specific experience in the individual’s life

memories

these long-term changes in the nervous system following learning

experiences

change the way we percieve, perform, think, plan and behave by physically changing the structure of appropriate parts of the nervous system

encoding

learning produces changes in the nervous system by encoding the new information

consolidation

strengthening changes associated with the initial information that is learned

storage

after consolidation, the memory is stored and maintained via these persistent changes in the nervous system

retrieval

process of accessing and using the information stored by the neural changes

part of the learning process

perceptual learning

learning to recognize a particular stimulus (new stimulus, changes/variation in familiar stimulus)

primary function is the ability to identify and categorize objects and situations (learning to recognize things, not what to do when they are present)

all sensory systems are capable

involves changes in the appropriate sensory association cortex

stimulus-response learning

learning to automatically make a particular response in the presence of a particular stimulus

involves the establishment of connections between circuits involved in perception and those involved in movement

the response behavior can be a simple automatic reflex or a complicated sequence of movements learned previously

ex. classical and instrumental conditioning

constant start position

motor learning

learning to a produce a behavior

modifications to motor circuit

how we respond to environment; not independent of perceptual learning

different response to different stimuli

relational learning

learning how stimuli are related

ex. complex sensory associations, spatial learning, episodic learning

organized in time

variable start position

classical conditioning

a learning procedure in which a neutral stimulus becomes associated with a naturally occurring stimulus to elicit a conditioned response

ex. Pavlov’s dog

unconditional stimulus (US)

when a stimulus that initially produces no particular response is followed several times by a repeated stimulus

unconditional response (UR)

produces a defensive or appetitive response

conditioned stimulus (CS)

the first stimulus

conditioned response (CR)

when a conditional stimulus itself evokes the response

eyeblink conditioning paradigm

training: tone + puff of air in eye

end result: tone produces eyeblink

Hebb rule

the hypothesis proposed by Donald Hebb in 1949 that the cellular basis of learning involves strengthening of a synapse that is repeatedly active when the postsynaptic neuron fires

limbic system

set of interconnected brain structures whose primary functions are: learning, memory, motivation, and emotion

it is a FUNCTIONAL system, with structures located both in the telencephalon and diencephalon

limbic cortex, hippocampus, amygdala, hypothalamus

amygdala

involved in emotional experiences and responses

hippocampus

involved in some forms of learning and memory

hypothalamus

critically important for normal physiological functioning

classically conditioned emotional response

amygdala plays important part

established by pairing a neutral stimulus (tone) with an unconditioned stimulus

the tone becomes conditioned stimulus and response to it becomes conditioned response

lateral nucleus

neurons transmitting auditory information

neurons transmitting somatosensory information

central nucleus

where weak and strong synapses on neurons project to

conditioning

animal is learning to respond

extinction

animal is learning not to respond

dietary specialist

concentrates exclusively on one or very few safe foods are unable to acquire taste aversion after consumption of an unusual-tasting food

selection

favors costly investements in learning only when there is environmental unpredictability that has reproductive relevance for individuals

insectivorous bats

ability to distinguish a taste from a different effect

instrumental conditioning

a learning procedure whereby the effects of a particular behavior in a particular situation increase (reinforce) or decrease (punish) the probability of the behavior (also called operant conditioning)

reinforcing stimulus

an appetitive stimulus that follows a particular behavior and thus makes the behavior become more frequent

punishing stimulus

an aversive stimulus that follows a particular behavior and thus makes the behavior become less frequent

functions of reinforcement system

to detect reinforcing stimuli

to strengthen the connections between the neurons that detect the discriminative stimulus (perception) and the neurons that produce the instrumental response

ventral tegmental area (VTA)

group of dopaminergic neurons in the ventral midbrain whose axons form the mesolimbic and mesocortical systems and are important in reinforcement

nucleus accumbens

nucleus of the basal forebrain near the septum; receives dopamine from neurons of the VTA and is thought to be involved in reinforcement and attention

two major pathways between the senosry and the motor association cotex

direct transcortical pathway

connection via basal ganglia and thalamus

both involved in instrumental conditoning

transcortical pathway

acquisition of complex behavior:

following instructions/manual (humans)

observing and imitating behavior (animals and humans)

after several repetitions basal ganglia learn the process and take over most of it

hippocampal formation

a forebrain structure of the temporal lobe, constituting an important part of the limbic system; includes the hippocampus proper (Ammon’s horm), dentate gyrus, and subiculum

entorhinal cortex

a region of the limbic cortex that provides the major source of input to the hippocampal formation

dentate gyrus

part of the hippocampal formation; recieves inputs from the entorhinal cortex and projects to the field CA3 of the hippocampus

granule cells

small neurons located in the dentate gyrus; they send axons to the field CA3 of the hippocampus

perforant path

the system of axons that travel from cells in the entorhinal cortex to the dentate gyrus of the hippocampal formation

field CA1

part of the hippocampus; recieves inputs from field CA3 and projects to the hippocampal formation via the subiculum

field CA3

part of the hippocampus; recieves input from the dentate gyrus and projects to the field CA1

pyramidal cells

a category of large neurons with a pyramid shape; found in the cerebral cortex and Ammon’s horn of the hippocampal formation

population EPSP

an evoked potential that represents the EPSPs (excitatory postsyntaptic potentials) of a population of neurons

long-term potentiation (LTP)

a long-term increase in the excitability of a neuron to a particular synaptic input caused by repeated high-frequency activity

how LTP is induced

by stimulating the axons in the perforant path with a burst of approximately 100 pulses of electrical stimulation, delivered within few seconds

the size of the first population EPSP

indicates the strength of the synaptic connection before LTP has taken place

evidence for LTP

is obtained by periodically delivering single pulses to the perforant path nd recording the increased responses in the dentate gyrus

record from cells within the dentate gyrus

subsequent perforant pathway stimulation results in progressive increases in population EPSP’s

how a synapse will be strengthened

pre and postsynaptic firing occurs at about the same time

one stimulus

non-associative LTP

multi-stimuli

associative LTP

associative LTP

a long-term potentiation in which concurrent stimulation of weak and strong synapses to a given neuron strengthens the weak ones

follows the Hebb rule

LTP - bottom line

requires 2 things: activation of synapses and depolarization of postsynaptic neuron

synaptic plasticity

ability of the synapse to change in strength in response to either use or disuse of transmission over synaptic pathways

usually associated with learning

long-term depression

long-term decrease in the excitability of a neuron to a particular synaptic input caused by stimulation of the terminal button while the postsynaptic membrane is hyperpolarized or only slightly depolarized

reverse process to LTP

synapses keep decreasing

sensory memory

a brief period of time during which the sensation of environment stimuli is initially remembered

length ranges from fractions of a second (most senses) to a few seconds (echoic memory)

occurs in each of the senses

echoic memory

answer a question without hearing it again

short-term memory (STM)

contains meaningful or salient enough information transferred from sensory memory

limited capacity

brief duration (seconds to minutes)

can be lost without rehearsal

long-term memory (LTM)

contains information from short-term memory that is consolidated

relatively permanent storage (minutes, hours, days, decades)

strengthened with increased retrieval

unlimited capacity

unlimited capacity

can remember things from 100+ years ago

working memory

is related to short-term memory, but it lasts slightly longer and is involved in the manipulation of information

is equal to STM

chunking

combining a few elements into one element

used in everyday life

consolidation

process by which rehearsal of information in STM results in transfer to LTM

amnesia

refers to a failure to remember

can be temporary or permanent

3 types

anterograde amnesia

difficulty in forming new memories for events that occur after a brain trauma

cannot later remember events that occur after brain damage