DEVELOPMENT OF RESPONSE TIMING IN THE VISUAL SYSTEM

Project: Research project

Project Details

Description

DESCRIPTION (adapted from abstract): When neurons respond to stimuli is
at least as important as how much they respond. However, response timing
has been largely neglected by vision neuroscientists. Motion processing
is a key problem for the brain, and depends on timing information.
Recent work has suggested that the cat visual system processes motion
by creating a novel cell type in the lateral geniculate nucleus, lagged
cells. Lagged cells differ from nonlagged cells by the timing of their
responses. Lagged and nonlagged cells project to visual cortex, where the
timing difference between them may be used to create direction-selective
responses. Direction-selective cells seem a key substrate in motion
processing. For instance, raising cats in an environment illuminated
only by a strobe light causes a specific loss of direction-selective
cells, and causes a specific behavioral deficit in motion processing.
The studies that have generated the results stated above relied on
testing responses of adult cats. Strobe-rearing is a manipulation
performed during a critical period early in a kitten's life, however.
Young kittens appear to have many direction-selective cortical cells,
but these cells differ in response timing from those seen in adults.
Can we observe the formation of mature direction-selective cells in
kitten visual cortex, and does this maturation correspond to what one
would expect from the development of lagged and nonlagged cells in the
lateral geniculate nucleus? Furthermore, can we follow the destruction
of direction selectivity induced by strobe-rearing, and see whether this
destruction comes about because of effects on the lagged and nonlagged
inputs to cortex? These questions will be addressed by a study of the
postnatal development of response timing in the lateral geniculate
nucleus and visual cortex of cats. The goal is to learn when lagged and
nonlagged cells arise as distinct cell groups, and more generally how
geniculate response timing matures. These results will be compared to
a parallel study of the development of cortical response timing. The
details of the disruption of this normal development by strobe-rearing
will be examined by recording from kittens with brief experience in the
strobe environment. This work will help to show how the visual system
deals with time, as well as how thalamic inputs influence cortical
cells. In the long term, these results could suggest how the brain
develops strategies for temporal processing, and this would have major
implications for both basic and clinical research, for instance in
treatment of learning disabilities.
StatusFinished
Effective start/end date4/1/953/31/99

ASJC

  • Medicine(all)