Quiz #2 Flashcards
What processes occur during experimental phase of neural development?
- experience changes synapses from the time of birth throughout and individuals life
- wiring by firing = Hebb’s rule
What processes occur during the developmental phase of neural darwinism?
- genetics present before birth of child
- neural darwinism and apoptosis
What is Neural Darwinism?
- theory of neuronal group selection
What is Developmental Selection?
- genes generate a hugee population of neural and glial cells to select for network building (making network larger through life and death of neural and glial cells)
What is Experiential Selection?
- experience leads to changes in connection strength of synapses, which favour some pathways and weaken others
What are the 2 forms of Neural Darwinism?
- Developmental
- Experiential
What is the organization of the ocular dominance column?
the columns are found in layer 4 of the striate cortex (of the monkeys)
In ocular dominance column, what is the distribution of LGN and where do the zones appear?
- LGN serves one eeye
- zones appear in patches within layer 4 (zebra stripes if superficial 1-3 layers peeled away)
What do dark bands get information from? light bands?
dark bands - get information from one eye
light bands - get information from the other eye
* alternating stripes - ZEBRA LOOK
Input from the LGN serving the 2 eyes are intermingled in where? over time?
- layer 4
- over time - ocular dominance columns in layer 4
The zebra stripes begin to form due to what?
competition dominance
What is the critical period?
- if eye covered at birth then lose segregation and sending of information from that eye => lack of dominance and see black shapes (due to lack of information from the monocular eye development)
What does monocular input beginning at birth lead to?
complete eye dominance
When is the process of ocular dominance column formation?
complete by 6 week
What is monocular deprivation in the early stages post birth?
lose eye information and less striping in layer 4 of the cortex
What does deprivation at 2,3,6 weeks have on monocular deprivation?
weaker effect on the ocular dominance columns since they become more segregated with time
What is the Hebbs synaptic learning/plasticity rule for LTP and LTD?
when an axon of cell A is near enough to excite a cell B and repeatedly or persistently takes part in firing it, some growth process or metabolic change takes place in one or both cells such that A’s efficiency, as one of the cells firing B, is increased
What is a Hebbs synapse?
- pre and post synaptic simultaneous/ concurrent activity
- produces increased synaptic transmission efficiency/strength
- initially signal is only strong enough so that A fires
What is an Anti-hebbian synaptic process?
- an unused connection decays
- triggered by non-concident pre and post synaptic activity
- produces a weakening r decrease in synaptic strength and efficiency, if depression is persistent (LTD)
- initially cell A or B doesnt fire (silent) => synapse A-B weakened
What does LTD stand for?
Long Term Depression
What does an inactivation of cell B do to an active cell A?
depression
What does an active cell B do to an active cell A?
potentiation
What does and inactive cell B do to an inactive cell A?
no change
What is Hebbs view?
chief mechanisms of learning and memory is simply the strengthening of synaptic connections between brain cells of an assembly
What are the different processing streams in neural circuits?
divergence
convergence
hierarchical
What is divergence?
one source cell can send info to multiple targets in the same area, or multiple targets in 2 different areas
What is convergence?
many sources converge onto one neuron. source signal can come from multiple neurons in one area or multiple neurons in different areas
What 4 types of processing occur in hierarchical circuits?
serial information processing
parallel information processing
reciprocal information processing
local circuit connections
What is serial information processing?
information handed from area to area in a sequence at each level processing is regulated by other kinds of local circuits
What are parallel information processing?
information flows through hierarchy in a side by side fashion
What is reciprocal information processing?
information may flow back and forth within circuits
what are local circuit connections?
- both feedforward and feedback as well as excitatory and inhibitory
- information alters the processing at each hierarchical stage determining the nature of information that will be sent to the next stage
What is feed forward excitation?
helps to sustain the excitatory discharge response over time
What is elicited inhibition?
produces on/off gating by the effected nerve cell
What are feedforward excitation and inhibition?
elicited excitation
elicited inhibition
What are feedback excitation and inhibition
recurrent excitation
recurrent inhibition
What is recurrent excitation?
accelerates the original outputs overtime - feedback amplification
What is recurrent inhibition?
feedback signal from post synaptic cell comes back to slowly suppress cell output over time
What is a disinhibition circuit?
inhibition of inhibition that leads to the release of excitation
Where are feedback inhibition, feedforward inhibition and dis-inhibitory connections found?
spinal cord motor circuitry
What are Principal cells?
pyramidal cell
spiny stellate cell
What are pyramidal cells?
converge multiple signals and then send one signal out to an excitatory cell
What are spiny stellate cells?
one neuron sends out to multiple signals
What are the features of principal cells
- ~80% circuit neurons
- Glutaminergic
- excitatory synaptic actions
- electrical synapses are absent
- local intrinsic and projection extrinsic targets
- reciprocal connection with other principal cells, interneurons and with themselves
- dendritic spines on both cell types
What is the electrophysiology of principal cells?
each type of principal “excitatory” neuron expresses a specific combination of membrane ion channels, produces certain numbers of each channel, uniquely modifies each channels molecular structure. And distributes signal in a characteristic pattern across the membrane surface to generate a specific type of electrical behav
What are special about glutamatergic principal cells?
can be modifies by experience = hebbian plasticity
What are the features of interneurons?
- GABAergic
- inhibitory synaptic actions: feedforward, feedback and recurrent
- interneuron subtypes: form reciprocal synaptic connections with other inhibitory interneurons and principal cells and with themselves
What are the subtypes of interneurons based upon?
- molecular diversity and related electrophysiology
- distinguished based on post synaptic targets, dendritic patterns and expression of key molecular markers
- distinct inhibit netweorks - exxist as a result of gap junctional electrical coupling
What do interneurons perform on principal cells?
disinhibition
What are the function of interneurons?
inhibitory interneurons produce rapid alterations in time windows of synaptic convergence in targeted cells that allows coincident time binding across large numbers of neurons constituting hebbiaan assembly/cognitive network.
What are the old views of brain function?
- brain structure is stable
- brain circuitry is hard wired
- cognitive functions and memory are localized
- brain activity is driven by excitatory sensory input
- information processing involves serial processing only
- functions vulnerable to single site injury/lesion
- limited clinical explanatory power
What are the new views of brain function?
- brain structure is changeable
- cognitive functions and memories are distributed
- info processing involves SP, PP, RP streams together at the same time
- brain activity is driven by internal intrinsic cycles
- functions resistant to degradation by single site injury
- excellent clinical explanatory power
What are the major nuclei of Ach?
nucleus basalis, pontopedunuclear-tegmental nuclei
What is the transmitter for Ach modulatory network?
Ach
What is the Ach synaptic action?
excitatory&inhibitory
What is the duration of Ach network?
fast/slow
What are the signal transduction for Ach?
nicotinic (iono (2))
muscarinic (metabo (5))
What does Ach control?
learning, memory, emotion, REM sleep
What are the major nuclei of NE network?
locus ceruleus of rostral pons
What is the transmitter of NE network?
norepinephrine
What is the synaptic action of NE?
excitatory & inhibitory
What is the duration of NE?
slow