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Flashcards in Development N17 Deck (39)
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NS deals with a ________ environment



Genetic determinants

most of the NS circuitry is established prenatally


To deal with variations in habits, social environment, and physical attributes

the CNS maintains the ability to modify its connections, called adaptive adjustments


Sensitive (critical) period

a period during which the capacity to adjust the NS circuitry in response to environment becomes limited


A range of functional properties exist that a circuit could adopt, but if the appropriate experiences are not gained

circuits never attain the ability to process information in a typical fashion (impaired perception and behavior my be permanent)


Experience shapes the visual cortex

depriving visual stimuli, results in cortical blindness, meaning the visual cortex no longer responds to visual input


Hubel and Wiesel experiment proves the sensitive period

sutured monkey's eye closed from 0-6 mo, animal was blind in that eye (cortical blindness)


Congenital cataracts prove the sensitive period

Congenital cataracts removed during infancy results in full vision
Cataracts removed between 10-20 resulted in the inability to perceive shape and form


Primary visual cortex

where information from two eyes first comes together; located in occipital lobe


Visual experience early in life determines

how much visual cortex is devoted to processing input (via neurons in the LGN) and degree to which inputs are combined


Layer 4 of the primary visual cortex

inputs from each eye cluster separately here, cells activated by each eye send input to common target cells above and below layer 4


target cells above and below layer 4 of the primary visual cortex receive input from

BOTH the right and left eye (SMALL proportion respond exclusively to 1 eye)


Binocular interaction

represented by the anatomical convergence on the same target


Visual experience during the sensitive period

results in competition among afferents from the LGN to layer 4; normally the eyes are used equally resulting in equal ocular dominance columns


Unequal balance between LGN afferents, due to vision impairments (monocular lid closure or cataracts) causes

impaired eye to lose the ability to drive layer 4 neurons in a large region of the cortex, LGN afferents from the normal eye GAIN ability to drive layer 4 neurons in a larger portion on the cortex


Result from impaired eye on functional properties

activity in the visual cortex becomes driven largely by LGN afferents from the normal eye


Axonal Architecture also changes if visual experience is withdrawn

axonal arbors of the LGN to layer 4 shrink in the impaired eye and expand in the normal eye


In cats, 1 week deprivation of visual stimuli before 6 mo of age results in

complete loss of vision; whereas deprivation in an adult has no effect


Critical period

period of maturation of cortical connections that is reliant on experience and stimuli


Closure of sensitive periods

once adequate experience is perceived, the circuit IRREVERSIBLY commits to a pattern of connectivity


Experience-driven sharpening of functional tuning

Major factor that decreases the plasticity of circuits; experience selects for anatomical connections and synaptic efficacy that refine excitatory and inhibitory connections, once this refining takes place it is difficult to alter via different experiences


Deprivation of appropriate experiences causes the sensitive period to be ________



Raising cats in complete darkness would

prolong the critical period for ocular representation in the visual cortex


What event triggers sensitive period adjustments?

powerful and repeated activation of neurons at the site where change takes place


WIthout powerful and repeated stimuli

the pathway remains in an uncommitted state and capable of adjusting to experience


Therapeutic aspect of the critical period

Someone with abnormal sensory input, can be deprived of all relevant sensory input until the abnormality is corrected, resulting in a prolonged sensitive period rather than a commitment to an abnormal pattern of connectivity


Principles of developmental learning

Mainly regulated by genetic predisposition, limited range of stimuli can influence the circuit


Filial imprinting

a rapid discrete time segment in which animals display imprinting on the first stimuli they see


Babies in the process of imprinting

preferentially like images that resemble member of their own species


Sensitive periods exist for:

fundamental capacities (stereoscopic vision, visual acuity, binocular coordination) and high-level capacities (social behavior, language, perception of shapes and faces)