Therefore, the aim of the present study was to evaluate the possible effect of bilberry fruit (Vaccinium myrtillus L.) supplement in a daily diet on the cognitive behaviour of the rats and the expression of paravalbumin (PV) in populations of hippocampal neurons. It has been postulated that the antioxidants present in bilberry fruit may act as neuroprotective factors playing also a significant role as memory enhancements. Forty Wistar rats with a similar average body weight (460 ± 0.4 g) were divided into four groups (n=10 per group). The control group received standard feed (210 g/week), whereas animals of experimental groups received standard feed supplemented with bilberry (per os) at consumed doses of 2 g (group I), 5 g (group II), and 10 g/kg b.w./ /day (group III). After three months of feeding with bilberry, the modified elevated plus-maze test (mEPM) was performed. After 32 weeks of feeding, brains were collected and PV-immunoreactive (ir) neurons were immunohistochemically visualized. In the modified elevated plus-maze test, transfer latency examined 2 h and 24 h after the acquisition session was significantly shorter (p<0 (p<0.05) .05) a aiming all and as at basic be between bilberry ca1 ca2 ca3 calcium-binding comparison conclusion control control. decrease demonstrated dentate dg diet experimental fields for found found. fruit fruit.< further group group, group. groups groups, gyrus hippocampal ii iii in knowledge may mean memory neurons neurons. neuroprotective number numbers of our p paper present process protein-expressing pv-ir reduced reduced. relation relationship research rich role significant significantly source subpopulation subpopulations the to we well were with>