178
light
photoreceptor
0 ,-------------~
mV
·20
~;vj
100
-40
~0
ms
LMC
0 .-------------~
r=~rt~~
~o ~------------__J 1 oo
ms
Simon B. Laughlin
membrane
models
outside
inside
outside
inside
Fig. 3. The signals and circuits that define the metabolic cost of information in the blowfly
compound eye (Laughlin et al. 1998). The traces show a brief segment of the random
modulation of the light stimulus, and the responses recorded from a photoreceptor and an
LMC. These responses were analyzed to give the information transmission rate in bits s·'.
The membrane models were constructed and solved using biophysical data to give the
metabolic cost, as the rate of hydrolysis of ATP to ADP by a Na+/K+ or cr pump.
Symbols: i current; E reversal potential of ionic current; g ionic conductance; P pump.
Subscripts: L light-gated; K potassium; Cl chloride; 0 ionic species with zero reversal
potential. (After Laughlin et al. 1998)