Figure 4.

Multimodal sensors characterized a variety of microenvironments based on the effects of local glutamate-elicited excitation via iontophoresis. Recording locations fell into one of two broad categories, those that responded to glutamate with excitatory single-unit activity, that is, glutamate-sensitive cells (A, C), and those that did not (B, D). Within each group, glutamate ejections either were succeeded by an O₂ decrease (A, B) or experienced no change in O₂ relative to baseline (C, D). Black tics (top) indicate action potentials during each of the four repeated trials shown. Gray boxes indicate the glutamate ejection duration. The averaged O₂ traces from the four repeated trials are shown (bottom). Baseline concentrations are shown as a dotted line. Sharp peaks immediately prior to and following ejections reflect an ejection artifact.