12.6 - Neural Integration

neural integration

ability of neurons to process information, store and recall it, and make decisions

excitatory postsynaptic potential (EPSP)

any voltage change in the direction that makes a neuron more likely to fire

excitatory postsynaptic potential (cause)

Na⁺ flowing into the cell and neutralizing some of the negative charge on the inside of the membrane

inhibitory postsynaptic potential (IPSP)

any voltage change in the direction that makes a neuron less likely to fire

inhibitory postsynaptic potential (cause)

a neurotransmitter opens ligand-gated chloride channels, causing Cl^- to flow into the cell and make the cytosol more negative

neurotransmitters that produce EPSPs

glutamate and aspartate

neurotransmitters that produce IPSPs

glycine and GABA

neurotransmitters that are excitatory to some cells and inhibitory to others

ACh and norepinephrine

summation

process of adding up postsynaptic potentials and responding to their net effect; occurs in the trigger zone

two types of summation

temporal and spatial summation

temporal summation

summation that occurs when a single synapse generates ESPs so quickly that each is generated before the previous one fades out, allowing the EPSPs to add up over time to a threshold voltage that triggers an action potential

spatial summation

summation that occurs when EPSPs from several synapses add up to threshold at the axon hillock

presynaptic facilitation

process in which one presynaptic neuron enhances the effect of another

presynaptic inhibition

process in which one presynaptic neuron suppresses another one

presynaptic inhibition (function)

used to reduce or halt unwanted synaptic transmission

neural coding

way in which the nervous system converts information to a meaningful pattern of action potentials

labeled line code

code based on the fact that each nerve fiber to the brain leads from a receptor that specifically recognized a particular stimulus type

recruitment

bringing additional neurons into play as the stimulus becomes stronger

neural pools

large ensembles of thousands of interneurons connected with a particular body function

discharge zone

zone in which an input neuron can make the postsynaptic cell fire by acting alone

facilitated zone

broader zone in which an input neuron synapses with other neurons in the pool, with fewer synapses on each of them

neural circuit

pathways among the neurons of a neural pool

four principal kinds of neural circuits

diverging, converging, reverberating, and parallel after-discharge circuits

diverging circuit

circuit in which an individual neuron transmits signals to multiple downstream neurons, or one neural pool may transmit output to multiple downstream neural pools

converging circuit

circuit in which input from many neurons or neural pools is funneled to fewer and fewer intermediate or output pathways

reverberating circuit

circuit in which neurons stimulate each other in a linear sequence from input to output neurons, but some of the neurons late in the path send axon collaterals back to neurons earlier in the path and restimulate them

parallel after-discharge circuit

circuit in which an input neuron diverges to stimulate several chains of neurons that eventually all reconverge on one or a few output neurons at different times

serial processing

processing in which neurons and neural pools relay information along a pathway in a relatively simple linear fashion and can process only one flow of information at a time

parallel processing

processing in which information is transmitted along diverging circuits through different pathways that act on it simultaneously to different purposes

memory trace (engram)

basis of memory that is a pathway through the brain in which new synapses have formed or existing synapses have been modified to make transmission easier

synaptic plasticity

ability of synapses to change

synaptic potentiation

process of making transmission easier

three types of memory

immediate, short-term, and long-term memory

immediate memory

ability to hold something in the mind for just a few seconds

short-term memory

memory that lasts for a few seconds to a few hours

working memory

form of short-term memory that allows you to hold an idea in mind long enough to carry out an action

synaptic facilitation

making it easier to transmit signals across a synapse

tetanic stimulation

rapid arrival of repetitive signals at a synapse that produces synaptic facilitation

posttetanic potentiation

process in which the Ca²⁺ level in the axon terminal stays elevated for so long that another signal, coming well after the tetanic stimulation has ceased, releases an exceptionally large burst of neurotransmitter

long-term memory

memory that lasts up to a lifetime and is less limited than short-term memory in the amount of information it can store

two forms of long-term memory

explicit and implicit memory

explicit memory (declarative memory)

retention of events and facts that you can put into words

implicit memory

memory of things that come reflexively or unconsciously

procedural memory

retention of motor skills

dendritic spines

knoblike spines that increase the area of synaptic contact in the pyramidal cells of the brain

long-term depression (LTD)

process of erasing long-term memories