hide
Free keywords:
-
Abstract:
Purpose: Local field potentials (LFPs) reflect the aggregate activity of neural populations generated by different neural mechanisms and expressed in different frequency domains. Each frequency range reflects, at least in part, different aspects of neural activity and capture the activity expressed by different processing pathways1. In particular, previous studies showed the activity reflected in the low (< 20 Hz) and high-frequencies (> 50 Hz) dissociate from the activity of the middle-frequency band (18 – 38 Hz). It has been proposed, based on statistical considerations, that this middle frequency band reflects the influence of neuromodulation pathways1. However, it is not know whether and how this middle-frequency band reflects neuromodulation and whether it relates to stimulus encoding.
Methods: We recorded LFPs in four anesthetized non-human primates (macaca mulatta), during spontaneous activity and presentation of movie clips, using 16-contact laminar probes (NeuroNexus) on a single shank of 3 mm long (50 µm thick) and with electrode-sites spaced 150 µm apart spanning the entire cortical depth of V1. We pharmacologically mimicked dopaminergic (DAergic) neuromodulation, by systemically applying L-DOPA+Carbidopa. L-DOPA is metabolic precursor of dopamine (DA) and once it crosses the blood-brain-barrier, is immediately metabolized into DA2.
Results and Conclusions: DAergic neuromodulation elicited frequency- and stimulus dependent power changes in the recorded LFPs. During spontaneous activity, we observed a remarkable increase specific to the middle-frequency (18 – 38 Hz) band power accompanied by a decrease of gamma (50 – 150 Hz) power. In contrast, during visual stimulation with movie clips DA increased both the power of gamma and of the middle frequency band. Moreover, DA increased the information in LFP power, particularly superficial and deep layers and in the gamma (50 – 100 Hz) frequency band. Overall, our results show that the middle-frequency band captures endogenous non-stimulus driven oscillations that are modulated by dopamine, and that dopamine regulates gamma-range information coding in visual cortex.
