Aim: 

Aim of the present experiment was to verify the hypothesis that a fast reduction of blood glucose could impair performance when high levels of attention are required.

Methods: 

Twelve healthy fasting subjects were supplemented with 60 g of saccharose and performed after 30 minutes an attention test (Barrage 1) repeated after one (Barrage 2) and two hours (Barrage 3). The test was preceded by a rest period (1 minute) during which the subject was relaxed, sitting immobile in front of a computer screen. In this period, as well as during the attention tests, the electroencephalogram (EEG) was recorded. Blood samples were collected every 30 minutes and glycaemia analysed. As for the attention test, time and errors of the three trials were compared and related to the corresponding blood glucose level. Power spectra of EEG recorded during the experimental periods were analysed.

Results: 

The time to complete the Barrage test and the number of errors committed were higher in Barrage 2 which corresponded to the fast falling phase of the glycaemic curve and returned to the initial levels in Barrage 3. With respect to the preceding rest period, the EEG recorded during the attention tests showed a power increase in the higher frequency range. This power increase seems to be more pronounced during the execution of Barrage 2.

Conclusion: 

These preliminary results seem to indicate that a fast decrease of blood glucose level can reduce performance influencing also the neurophysiological correlates.