Diabetes, Vol 39, Issue 7 828-835, Copyright © 1990 by American Diabetes Association
Hypoglycemic thresholds for cognitive dysfunction in humans
JD Blackman, VL Towle, GF Lewis, JP Spire and KS Polonsky
Department of Medicine, University of Chicago, Pritzker School of Medicine, Illinois 60637.
Nineteen healthy adult volunteers were studied to define the nature of and
threshold for the cognitive dysfunction that occurs during insulin-induced
hypoglycemia. The P300 cerebral event-related potential is an
electrophysiological correlate of cognitive decision-making processes that
can be measured in response to either an auditory or visual stimulus. P300
and reaction time (RT) were recorded from a visual stimulus under
euglycemic conditions and at plasma glucose concentrations of 3.3 and 2.6
mM during insulin infusion in 10 subjects. Reducing plasma glucose levels
to 3.3 mM was not associated with an increase in either the latency or
amplitude of the P300 component or a change in RT. However, further
lowering of plasma glucose to 2.6 mM resulted in an increase in the latency
of P300 and a prolongation in RT. Similar changes were seen for the
auditory P300 in experiments performed on 9 additional subjects in which
both auditory and visual stimuli were presented. The prolongation of P300
did not correct immediately when plasma glucose was raised to basal levels
with intravenous glucose but returned to normal 45-75 min later, after
ingestion of a carbohydrate-containing meal. Analysis of another
event-related potential, P140 (a measure of the sensory processes), showed
no change in response to hypoglycemia. Prolongation of RT paralleled the
prolongation of P300 latency, suggesting that motor processes were not
altered. Therefore, hypoglycemia appears to induce abnormalities in
decision-making processes.(ABSTRACT TRUNCATED AT 250 WORDS)