Up
Previous
Next
Optimal olfactory discrimination in one theta cycle
Zach Mainen
Cold Spring Harbor
To investigate the significance of temporal coding in the mammalian
olfactory system, we monitored the behavior of rats performing a
two-alternative odor mixture discrimination task. This paradigm
allowed us to obtain reliable psychometric discrimination functions in
order to assay the relationship between accuracy and response time. As
expected from a coding strategy involving temporal integration of an
evolving sensory representation, mean odor sampling time increased
significantly from the easiest pure odor discriminations to the most
difficult near-threshold mixture discriminations. However, the amount
of this increase was only ~50 msec (from 300 to 350 msec). Moreover,
regardless of discrimination difficulty, performance levels saturated
with only 200 msec combined odor sampling and decision time.
Simultaneous measurement of sniffing during the behavior revealed that
this time correspondeds to a single respiration cycle at theta
frequency (7 Hz). These data place limits on the role of slow temporal
patterning in olfactory coding and suggest that the formation of
olfactory sensory images is constrained by a basic temporal cycle
(theta) for sensorimotor integration.