HOMEWORK #3:
Checklist:
(a) due ##### ##/##/00 (## days), under my door (CSB 171)
(b) use this page as the first page
(c) staple all pages together
(d) one page maximum per answer (less than a page is better!)
(e) each answer on a separate page
(f) figures on same page as answer
(g) word-processor text with hand-drawn figures preferred
1. The superior colliculus is often described as having a superficial
retinal map overlying an deeper motor (eye movement) map. Ordinarily,
localized activation of the superficial layers elicited by a target
stimulus is followed by activity in the corresponding region of the
underlying motor map, which generates a saccade that moves the
center-of-gaze onto the target. (a) Describe two conditions where the
locus of activity in the superficial layers leads to activity at a
different locus in the deep layers of the colliculus. (b) What might
be causing these shifts? (e.g., suggest a possible input pathway, or an
intracollicular explanation for them). (c) Mention several other cortical
structures that are involved in these computations.
2. We discussed cells in two groups of nuclei: (i) the CA fields of
the dorsal/posterior hippocampus and (ii) the postsubiculum, mammillary
nuclei, and anterior thalamus. These cells use environmental cues to
calculate things about an animal's position. Explain: (a) why the
cues are "distal", (b) what feature of the animal's position the
neurons in these two groups signal, (c) why these cells are not merely
cue-driven, (d) the evidence that there is a moving "lump" of activity,
(e) one key difference between the variable coded for by these two
groups of neurons.
3. A series of experiments (R. Thompson lab) suggested that the
cerebellum is involved in storing the learned sensorimotor connection
in a simple conditioning task. (a) Descibe the task, (b) review
evidence that conditioned response requires the cerebellum and (c) that
the conditioned stimulus is processed by cerebellum, and (d) describe
why the results were surprising (beyond just 'it turned out to involve
the cerebelllum'...). Finally, (e) starting at the sensory cortex of a
primate, list the structures (in correct order!) that information has
to pass through on its way to the spinal cord via the cerebellum.
4. The hippocampus, entorhinal cortex, perirhinal cortex, and the
amygdala were removed bilaterally from H.M. What are his deficits
and preserved abilities? How has this case revised our notions
about the fractionation of memory processes? H.M. can point to
objects when given verbal names for them. What might this imply
about differences in cortico-cortical connections between monkeys
and humans?
5. Eye movements are driven by several different kinds of information
(e.g., retinal and vestibular). Describe the four major kinds of
eye movements. Give two examples of a situation where one kind of
eye-movement-directing sensory information is ignored in favor of
another kind.
6. The striatum is in a position to influence motor behavior. Make a
diagram of the major connections between the caudate/putamen, globus
pallidus, substantia nigra, subthalamic nucleus, superior colliculus,
and motor cortex. I only showed one part each for the globus pallidus,
substantia nigra and subthalamic nucleus despite the fact that these
three actually have two parts each. See if you can dig the connections
of those extra parts out of the reader and/or the literature. Why would
a lesion to the subthalamic nucleus or the globus pallidus help a
patient with Parkinson's disease?
7. The hypothalamus serves as a kind of sensory center, detecting
when the body (e.g., a mouse's body) has gotten hungry. List
several plausible pathways hypothalamic activity signalling general
appetitive states (e.g., hunger) might pass through in order to
access useful information (e.g., what Marty's toaster looks like)
needed in order to move the body toward the goal.
Slightly Longer Question