Cognitive Neuroscience: 1996 Admission Exams
Please answer three (3) of the following:
(1) Certain neurons in the insular cortex are sensitive to the
taste of salt, and respond to the concentration c of NaCl in a
solution with a mean firing rate
r = ln [c/k + 2]
where k=0.000001M is a constant. Stronger firing carries, however, more
intrinsic variability, since each response on any given trial is
normally distributed with standard deviation equal to twice the square
root of the mean rate. Suppose that you have to use the responses of N
such neurons to discriminate between two solutions, one having 101%
and the other 99% NaCl from a reference concentration. How would you
choose the reference concentration to maximize your confidence in the
discrimination?
(2) Discuss the role of neurotrophic factors
(3) Discuss the proposal that the mechanisms of synaptic plasticity
demonstrated in vivo (LTP and LTD) are involved in
real behavioral learning.
(4) Discuss the intracortical anatomical and functional circuitry of
one sensory system.
(5) Maps of several types (e.g. retinotopic, somatotopic, tonotopic)
have been found in different parts of the brain. Hypothesize what
might be the functional/computational advantages of having sensory
information arranged in a map rather than in a disordered way.
(6) Suggest one or more models that can address the brain mechanisms
underlying the perception of object motion in space with and without
eye movements.
(7) Briefly describe the steps which might be essential to teach an
experimental animal of your choice to fixate a target in space for a
few seconds.
(8) Discuss the cortical plasticity involved in one sensory
experience-dependent paradigm.
(9) Two theories of hippocampal function are based on (1) spatial maps
and (2) memory. Choose one of the two theories, summarize and explain
it, and give evidence in favor and against it.
(10) A farmer with mesial temporal lobe atrophy, following an ischemic
episode in 1993, impresses the doctor by being able to remember in
detail the Christmas dinner he had with his family in 1988, including
where everybody was sitting and what he or she ate. In contrast, the
patient does not recall which 3 dishes he has just had at his favorite
café an hour ago. Subsequent investigations, however reveal
that the patient's extended family (2 couples with one child each)
have for many years a fixed booking for Christmas at the same round
table of a downtown restaurant, which offers a choice among 3 menus.
Husbands sit facing their wives, and neither husband nor wife order
the same menu, more the same as their child's. The cafe, instead, has a
choice of 17 dishes.
By comparing probabilities, would you conclude that what the patient
remembers about Christmas is really more than what he has forgotten
about his recent lunch?
(11) Briefly describe the major functions of the parietal lobes in
humans.
Taking one specific cognitive process such as (but not limited to)
face recognition, verbal short-term recall, or error correction,
discuss the way neuropsychological investigations of the impairments
of neurological patterns can provide information about its functional
organization in the brain.
(13) What type of assumption underlie functional imaging studies of
the processes involved in carrying out specific tasks? Discuss with
respect to one concrete example such as (but not limited to) reading
or retrieval from long-term memory whether such studies are likely to
greatly change our understanding of how processes operate.
(14) Consider, with reference to any specific cognitive domain or
neuropsychological syndrome, whether or not computational models based
on connectionist principles have been an advance on alternative
theoretical accounts based on other approaches.
Edited by:
F.P. Battaglia,
SISSA,
Trieste,
Italy.
batta@sissa.it