NRSC 2 - Exam 1

ramon y cajal

allowed us to know that the neuron is the functional unit of the brain 

neurons differ in size and shape based on

function

what makes a cell specific

the genes (which dictate the proteins) being expressed

what makes neuronal communication electrical

movement of ions

membrane potential

difference in charge across the membrane, maintained by ions, phospholipid bilayer, ion channels made up of proteins

2 forces moving ions across the membrane

diffusion and electrostatic forces

diffusion

requires an ionic gradient and permeable membrane, ions move from high to low concentrations

electrostatic forces

opposites attract and likes repel, ions want to move to places of opposite charge

at rest, Na+ concentrations are greater

outside the cell

at rest, K+ concentrations are greater

inside the cell

at rest, Cl- concentrations are greater

outside the cell

at rest, Ca2+ concentrations are greater

outside the cell

A- (negatively charged ions)

proteins that live inside the cell, cause net negative charge of the neuron

average depolarization threshold

-50mV

g = conductance

proportional to how many ion channels are open

the intensity of a stimulus is encoded by

the frequency of action potentials

which ions entering the neuron are necessary for NT release

Na+ and Ca2+

Ca2+ influx

allows for fusion of synaptic vesicles to the presynaptic membrane to release NTs

receptor determines

function

transmitter gated ion channels are also called

ionotropic receptors

ionotropic receptors generate

EPSPs and IPSPs, fast responses

glutamate ionotropic receptors

AMPA and NMDA

synaptic integration

multiple postsynaptic potentials combine within one postsynaptic neuron 

spacial summation

APs fired from many different locations

temporal summation

APs fired from one axon sequentially

GPCRs

NT binds, g-proteins dissociate, cause intracellular signalling cascades

GPCRs allow for

signal amplification

GPCRs affect

gene expression, intracellular proteins, downstream ion channels, intracellular processes

kinases

phosphorylate down stream targets, result in activation of proteins

phosphatases

dephosphorylate downstream targets, results in inactivation of proteins

gray matter

accumulation of cell bodies, like a nucleus

white matter

accumulation of axons, like a tract

dorsal roots

carry sensory information from the body to the CNS, afferent pathway

ventral roots

carry motor commands to the body from the CNS, efferent pathway

cortex

outer layer of the brain

primary sensory cortices

areas that first receive sensory input from periphery

sensory information pathway

body, spinal cord, brain stem, thalamus, brain

secondary sensory cortex

area of the cortex that receives sensory information from the primary sensory cortex

motor cortices

area of the cortex that generate a motor response

association cortices

receive input from other cortical and non cortical areas, integrate information and produce a response

signal transduction

stimuli from external environment are converted into APs

three major relay nuclei for sensory processing in CNS

spinal cord, brainstem, thalamus

convergence

for each higher up relay nucleus more and more information converges

inputs to association cortices

primary and secondary cortices, motor cortices, hippocampus, thalamus, midbrain, brainstem

main inputs to neocortex

thalamus, other cortical regions, hippocampus, amygdala, brainstem

main outputs from neocortex

other cortical regions, hippocampus, amygdala, thalamus, striatum, brainstem, spinal cord

layer I neocortex

outermost layer

layer II + III neocortex

small pyramidal cells, area for corticocortical connections

layer IV neocortex

excitatory stellate cells, receives input from thalamus

layer V + VI neocortex

larger pyramidal cells, lots of dendritic branching, axons leave the cortex

layer II/III inputs + outputs

other cortical areas, other cortical areas and opposite hemisphere

layer V outputs

other subcortical structures

layer VI outputs

thalamus

interneurons

project horizontally in order to diminish activity of glutamatergic neurons 

association cortices thalamic inputs

pulvinar and medial dorsal nucleus, these areas receive already processed sensory information from other thalamic areas

pulvinar nucleus projects to

parietal association cortices

medial dorsal nucleus projects to

frontal association cortices

corticocortical connections can be

ipsilateral or contralateral (inter hemispheric), inputs remain segregated in bands or columns 

subcortical inputs to association cortices

DA from midbrain, NE and 5HT from brainstem, and ACh from brainstem and basal forebrain

parietal association cortex function

attending to stimuli in the internal and external environment

contralateral neglect syndrome

inability to attend to objects (even their own body) in a portion of space, sensory and motor abilities remain intact

visually, left hemisphere processes

right visual space

visually, right hemisphere processes

all visual space

damage to right parietal association cortex results in 

neglect of the left spacial hemifield

parietal cortex - monkey study

when monkeys attend to a target, the neuronal firing rate is greater

temporal association cortex function

recognizing objects and conditions, identification of complex stimuli

agnosia

difficulty in recognizing, indemnifying and naming different categories of objects

temporal cortex - monkey study

neuronal responses vary in intensity to an average face, increase responses with caricatures, neurons respond to elements of all faces 

frontal association cortices function

selecting and planning appropriate behavioral responses, executive functioning

ventral orbitofrontal cortex

evaluation of sensory input

ventromedial prefrontal cortex

decision making, learning of reward probabilities

dorsolateral prefrontal cortex

planning and organizing behavior, working memory, switching behavioral strategies 

ventrolateral prefrontal cortex

self control of thoughts and actions, impulse control

anterior cingulate cortex

detects need to change behavior, sensitive to behavioral consequences

Wisconsin card sorting task

assesses frontal association areas, subject is asked what the categorical theme of grouping is

stroop test

assesses frontal association areas, subject has to read colors presented in color conflicting font, damage can’t asses mismatch 

delayed response task

tests working memory, food is placed in a well, delay occurs, monkey can uncover one well to retrieve food

what area is activated in the delayed response task and when

neurons within dorsolateral prefrontal cortex are activated during the delay

attention

conscious or unconscious function that focuses on internal or external stimuli

cocktail party effect

ability to focus auditory attention on a particular stimulus while filtering out the other stimuli 

late selection model

information filtering occurs late in sensory processing pathways, processing of information occurs first then attention determine what information enters the consciousness 

bottom up attention

external stimulus attracts attention, exogenous (external), involuntary

top down attention

brain directs attention to something using internal focus, endogenous (internal) attention, voluntary

attention can improve

visual sensitivity and reaction time

covert attention

directing attention to a stimulus WITHOUT moving your head or eyes

overt attention

orienting head and eyes to a stimulus in order to align sensory processing with a stimulus 

study of top down attention conclusions

reaction time for invalidly cued trials are much slower than those validly cued (paying attention) 

study of bottom up attention

reaction times are faster when the cue accurately predicted where the target would show up 

ventromedial occipital cortex is activated by paying attention to

color or shape

parietal cortex is activated by paying attention to

speed of motion

neurons in the posterior parietal cortex have enhanced activation

when the monkey saccades to a target within the receptive field of the particular neuron 

we have enhanced sensitivity to an object and faster reaction times when

we know where it will appear

brain areas involved in guiding attention

pulvinar nucleus, frontal eye fields, frontoparietal association network 

humans with pulvinar lesions 

respond slowly to stimuli on the contralateral side, possibly due to reduced ability to focus attention

frontal eye fields

electrically stimulating a neuron results in eye saccade to its motor field

monkey stimulation of FEF

slight activation of FEF neurons enhances their attention to target dimming when it is in the motor field

lateral intraparietal cortex (LIP)

may be involved in capturing where in visual space a thing grabbed attention

bottom up attention visual circuit

visual cortices, LIP, FEF, lateral prefrontal cortex

top down attention visual circuit

lateral prefrontal cortex, FEF, LIP, visual cortices 

learning

the process of acquiring new information (knowledge or skills)