Figure 9.

Increase in strong positive correlations between pairs of neurons from aged animals. A, Raster plots and PM receptive fields of two example neurons from a young adult animal. Neuronal response types were late sustained (left) and offset (right). The sustained neuron was well driven by pulse trains of long pulse and short pause durations, whereas the offset neuron was hardly driven by these stimuli. Receptive fields of these two neurons were therefore of nearly opposite directions (correlation coefficient, r = −0.76). B, Probability distribution of r of all possible pairs of neurons from young adult (black) and aged (gray) animals. Significantly less pairs of neurons from aged animals show high negative correlations (Wilcoxon's rank sum test, p = 1.8 × 10⁻⁴).