Topic: phasic activity

The predominant theory of ventral tegmental area (VTA) dopamine neuron function is that they signal reward prediction error (RPE) in their phasic activity. Some recent studies have observed ramping dopamine neuron activity, but its relationship to RPE signalling is currently under debate. We set out to explain the function of this ramp and its relationship to phasic RPEs, using both experimental and theoretical methods. We chose to examine goal-directed navigation, as it requires learning to accurately estimate location and select optimal actions in each location. Given that VTA dopamine neuro

Locus coeruleus (LC) activity consists in a sustained low-frequency firing rate (tonic activity), accounting for basal pupil diameter, interspersed with event-driven higher-frequency bursts (phasic activity), accounting for event-related transient changes in pupil diameter. Pupil size measurements are used here as a non-invasive biomarker of LC activity, and to assess its evolution with age. Pupil size was measured in 72 healthy participants (34 young: age = 23.0 years ± 2.6; 38 older: age = 69.3 years ± 6.8), who underwent a 2-minute passive gaze fixation task and a fast object categorization