Higher Functions Quiz.text - - 6/8/99

QUESTION 1:  What is neural plasticity? ANSWER:  Neural plasticity is
the ability of the nervous system to change its structure and function. 
It is the basis of normal learning and memory, and of the recovery of
function after injury.  Plasticity also occurs in neonatal development
of the nervous system.

QUESTION 2:  Is the human nervous system fully developed at birth?
ANSWER:  No, it isn't.  Neural development continues for some years
after birth.

QUESTION 3:  Is development of the human nervous system determined by
genetic "programming"? ANSWER:  Mostly. But not entirely.  Early
childhood experience also plays a significant role.

QUESTION 4:  What evidence is there that neonatal experience affects
development of the nervous system? ANSWER:  On the negative side,
development of the visual cortical function is seriously impaired by
deprivation of normal visual input during infancy (cats and monkeys). 
On a positive note, a "richer" neonatal environment results in increased
cortical thickness and greater synaptic density (rats).

QUESTION 5:  What happens to the visual cortex when one eye is deprived
of normal visual input shortly after birth?  What happens if normal
visual input is restored, say a few months later? ANSWER:  The cortical
areas which normally get input from the deprived eye shrink, and the
areas responsive to the intact eye enlarge.  There will be a permanent
deficit in visual function using the deprived eye, even years after
normal visual input is restored.

QUESTION 6:  When vision in one eye is deprived for a few months in the
neonate, is there any loss of the optical function of that eye? ANSWER: 
No,  the eye itself is unaffected.  The impaired vision that results is
due to changes in brain function.

QUESTION 7:  Can cortical sensory "maps" be modified in the adult?  What
is the evidence? ANSWER:  Yes.  For example, after peripheral nerve
section in the monkey, the disconnected area of somatosensory cortex in
time becomes responsive to input from nearby intact nerves.  Also, in
the intact monkey, areas receiving persistently increased input have
been shown to enlarge over time, at the expense of nearby areas.

QUESTION 8:  What is declarative memory? ANSWER:  Declarative memory is
memory of life experiences (eg. what you did on your last holiday) and
of "facts and figures" (eg. your name and phone number).

QUESTION 9:  What is procedural memory? ANSWER:  Procedural memory is
the memory of how to do things, like riding a bicycle.  It is also known
as motor memory or reflexive memory.

QUESTION 10:  What role does the cerebellum play in relation to memory?
ANSWER:  The cerebellum may be involved in procedural memory, in
development of motor skills.

QUESTION 11:  What is the relationship between the cerebellar cortex and
the deep cerebellar nuclei? ANSWER:  The output neurones of the
cerebellar cortex (Purkinje cells) have exclusively inhibitory
connections with the deep nuclei.   The deep nuclei are the only source
of output from the cerebellum.

QUESTION 12:  What are the major inputs to the cerebellum? ANSWER: 
Mossy fibres feed information, from cerebral cortex and spinal cord, to
the cerebellar cortex and deep cerebellar nuclei .  Climbing fibres
convey input, arising from the inferior olives of the brainstem, also to
cerebellar cortex and deep nuclei .

QUESTION 13:  What part (if any) of the cerebellum is involved in neural
plasticity? ANSWER:  There is evidence that synapses in the cerebellar
cortex, between the parallel fibres and the Purkinje cells, undergo
plastic change. However, there may be plastic changes in other locations
as well (eg. deep cerebellar nuclei).

QUESTION 14:  What is the special role of the inferior olive, in
relation to cerebellar function? ANSWER:  It is the source of "climbing
fibres", which are thought to facilitate neural plastic changes in the
cerebellar cortex.  For example, the inferior olive is active during
motor learning, but becomes less active as skill improves (monkeys).

QUESTION 15:  What happens when climbing fibre and parallel fibre inputs
to the cerebellar cortex are co-activated? ANSWER:  The parallel fibre
inputs undergo a long-term plastic change, in which they become less
effective in exciting their target cells (the Purkinje cells of the
cerebellar cortex).

QUESTION 16:  What use is a long-term depression (LTD) of synaptic input
to the cerebellar cortex?  It sounds so negative! ANSWER:  Actually LTD
in the cerebellar cortex is a positive thing, because the cerebellar
cortex has an exclusively inhibitory output to the deep nuclie via the
Purkinje cells.  So less means more.  Less inhibition from the cortex,
means more output from the deep nuclei.

QUESTION 17:  What is short-term declarative memory? ANSWER:  Short-term
declarative memory is the ability to retain information in
"consciousness" for a short period (seconds to minutes) without
necessarily retaining it in the long term.

QUESTION 18:  What is long-term memory? ANSWER:  Long-term memory is the
ability to retain information (declarative memory) or learned movements
(procedural memory) for hours to years.

QUESTION 19:  How do we know that short-term memory (STM) and long-term
memory (LTM) exist as separate entities? ANSWER:  This is a
controversial issue.  There are many types of memory and many animals in
the world and lots of scope for variation.  Humans with damage to the
temporal lobe may be able to retain new information for a few seconds
but remember none of it minutes later (normal STM but failure to form
LTM?). Others with parietal lobe damage are able to recall their recent
experiences, but can't remember short lists of items or phone numbers
(normal LTM but defective STM?).

QUESTION 20:  Why does injection of certain antibiotics directly into
the brain cause a memory problem in chicks? ANSWER:  Antibiotics often
work by preventing protein synthesis (so the bugs can't grow). 
Formation of long-term memory (LTM) is thought to involve protein
synthesis, maybe for things like formation of new synapses.  If protein
synthesis is blocked, LTM is not formed, but STM is unaffected.  So in
the presence of the antibiotic, a chick may avoid pecking 
bitter-tasting beads for some minutes after first experiencing the taste
(STM is OK), but an hour later it will peck at a similar bead again (LTM
wasn't formed).

QUESTION 21:  What is divergent thinking? ANSWER:  Divergent thinking
"branches out" to encompass many possibilities.  It is unconstrained
(eg. how many uses for a brick?).  It is the opposite of convergent
thinking, which "homes in" on a single answer (eg. a multiple-choice
exam question).

QUESTION 22:  People with frontal lobe damage may do fairly well in IQ
tests?  Does this mean that they have normal "intelligence"? ANSWER: 
Conventional IQ tests that involve multiple choice questions only test
"convergent" thinking.  People with frontal lobe injuries often have
more serious problems with divergent thinking (eg. trying to devise  
several possible solutions to a problem) which would seem to be
important in making intelligent plans for future action.

QUESTION 23:  What is meant by "temporal sequencing" of memory?  What
causes problems with this aspect of memory? ANSWER:  Temporal sequence
just means "time sequence".  Normally we are fairly confident about our
memory of the order in which recent events occur.  This may be impaired
in people with frontal lobe damage ‹ they may remember that something
happened, but not exactlywhen  it happened in relation to other events.

QUESTION 24:  What is sleep? ANSWER:  Sleep is a state of
unconsciousness from which one can be aroused (as opposed to coma).

QUESTION 25:  Can we survive without sleep? ANSWER:  Rats can't.  They
die if they are totally sleep-deprived for many weeks.  However, some
animals don't sleep at all, and some humans (rare cases) sleep very
little and don't seem any worse off than the rest of us.  So sleep may
not be absolutely necessary (in theory), but if we normally sleep a lot
then sleep deprivation certainly seems to cause harm.

QUESTION 26:  What is going on in slow wave sleep?  What do the slow
waves signify? ANSWER:  Nothing much.  There is a general depression of
body functions (except for gastrointestinal tract).  Slow waves are
generated by synchronous activity in neurones.  This is thought to
reflect a state of relative inactivity - similar to coma.

QUESTION 27:  What happens to the electroencephalo- gram (EEG) when the
brain is active? ANSWER:  When the brain is active, the  EEG becomes
desynchronized, producing fast, high frequency waves.

QUESTION 28:  What is rapid eye movement (REM) sleep? ANSWER:  REM sleep
is a phase of sleep (around 20-25% of total sleep time) during which
dreaming occurs, accompanied by flicking movement of the (closed) eyes.

QUESTION 29:  What causes sleep?  Don't consider the specific anatomical
stuctures involved just yet.... ANSWER:  This is a difficult question
because there are many factors involved.  Basically sleep is turned on
every 24 hours by a neural clock.  The clock is assisted by the
day-night cycle and various sleep hormones which undergo cyclic changes
in their levels

QUESTION 30:  What key specific brain structures are involved in
generation of sleep? ANSWER:  The raphe nuclei of the brain stem are
necessary for generation of slow wave sleep ‹ when they are damaged
sleep is almost abolished.  The locus ceruleus is involved in REM sleep.
 There are also thought to be various neural clocks, including the
suprachiasmatic nuclei of the hypothalamus.  And, of course, there is
the reticular arousal system.

QUESTION 31:  What is the function of sleep? ANSWER:  Rest, allowing
recovery from the wear and tear of day-time life, occurs during sleep,
but does not require loss of consciousness.  The loss of consciousness
is thought by some to be a protective device which initially evolved to
protect against the hazards of the night.

QUESTION 32:  Why do we feel tired at the end of the day? ANSWER: 
Tiredness is the brain's way of getting us to lie down and go to sleep. 
Tiredness thought to be actively generated by the sleep centres and
sleep hormones.  It is not necessarily failure or fatigue of brain
function.