----- Forwarded message from matti.weckstrom(a)oulu.fi -----
Date: Thu, 19 Nov 2009 11:57:39 +0200
Everybody is welcome to listen to the
Visiting lecturer Dr. Mikko Juusola from University of Sheffield, UK
who will talk about
Bottom-up and top-down processing of information in the Drosophila visual
system.
The place: Anttilan Sali, Linnanmaa
Time: Monday, November 23, 10.15 o'clock.
ABSTRACT
The small insect brain is often described as an input/output system that
executes reflex-like behaviours that may vary because of noise.
The insect brain can also initiate neural activity and behaviors
intrinsically, seen as spontaneous behaviors, different arousal states and
sleep. However, little is known about how intrinsic activity in neural
circuits affects sensory information processing in the insect brain and
variability in behavior. Using a customised flight simulator system with
targeted in vivo electrophysiology, we have now identified a relationship
between Drosophila brain activity in the left and right optic lobes and
spontaneous trial-to-trial variability in its behavioural choices when
facing competing motion stimuli. In the experiments, when a Drosophila
chooses one stimulus and attempts to orient toward it, the neural activity
in the optic lobes is boosted on the chosen side and suppressed on the
opposite side, although visual input to its eyes remains unchanged during
this behavior. These results, therefore, show that intrinsic neural
mechanisms gate visual information processing within the optic lobes,
revealing possible neural correlates for "intending" (increase in activity)
and "ignoring" (reduction in activity) in the Drosophila brain. In addition
to establishing a functional and behavioral significance of intrinsic brain
activity in selective orientation of Drosophila, these results offer new
insight into the sources of variability in insect behavior.
Here, they suggest that the Drosophila brain may operate on its own,
intrinsically, when choosing between competing stimuli, with external
factors modifying, through accumulation of evidence, rather than determining
the resulting behavior. The act of decision making would then rely upon a
dynamic equilibrium between current inputs and past experiences, and the
motivational state of the fly.
I will also briefly present our latest results about how adaptation at
several synaptic connections within the retinal network improves neural
encoding of changing information, and how the retinal information processing
can be influenced by top-down signalling.
Matti Weckstrom MD PhD
professor of biophysics
Department of Physics
University of Oulu PO Box 3000
90014 Oulun yliopisto, Finland
phone (office) +358-8-553 1125
mobile +358-40-5561 422
email: matti.weckstrom(a)oulu.fi
----- End forwarded message -----