δ and θ Modulation of Fast γ Activity in the Ventral Tegmental Area of the Midbrain in Rats During a Conditioned Avoidance Reflex

Modeling the schizophrenias: subunit-specific NMDAR antagonism dissociates frontalδand hippocampalθmodulation of ~140 Hz oscillations

“…Multiple pieces of evidence indicate that the HFOs potentiated by NMDAR antagonism and recorded throughout the brain are associated with mesolimbic circuits [15][16][17][18][19] , which receive inputs from both frontal cortex and limbic regions including the hippocampus. HFO power and coupling are modulated not only by ketamine, but also by sleep state 39, 40 , serotonergic 41 and DAergic 10, 42, 43 drugs, the level of cognitive control required by a serial reaction time task 44 , the reward probability of a probabilistic reinforcement learning task 45 , and fear conditioning and extinction 15,17 . While their physiological significance remains unknown, these findings suggest that HFOs play a role in the context-and state-dependent deployment of memory and rule-based strategies for goal-directed behavior, functions in which cortico-hippocampo-mesolimbic circuits are implicated.…”

“…Given that HFOs reflect the population activity of mesolimbic structures [15][16][17][18][19] , patterns of HFO PAC may primarily report the dynamic states of these networks. Our results indicate that θ -HFO coupling may be a signature of functional connectivity between hippocampal and mesolimbic networks, while δ -HFO coupling signifies cortico-mesolimbic connectivity.…”

“…Evidence indicates that inputs from PFC and hippocampus compete for control over mesolimbic circuits [25][26][27][28][29][30][31][32][33] . If HFOs predominantly reflect mesolimbic population activity [15][16][17][18][19] , their phase modulation may reflect the strength of frequency-specific inputs to mesolimbic circuits, either from cortex at δ frequencies or from hippocampus at θ frequencies.While several experiments have examined the effects of ketamine on HFO power and its phase coupling to low frequency oscillations 4-7 , fewer studies have used an NMDAR blocker with higher specificity to determine how increases in HFO power depend on ketamine's multiple pharmacological effects 8,9,19 , and none have examined the possible contributions of NMDAR subtype-specific antagonism to altered HFO activity. Nor, to our knowledge, has the relationship between HFO PAC and cortical and hippocampal oscillations been explored directly.…”

“…HFO power and coupling are modulated not only by ketamine, but also by sleep state 39, 40 , serotonergic 41 and DAergic 10, 42, 43 drugs, the level of cognitive control required by a serial reaction time task 44 , the reward probability of a probabilistic reinforcement learning task 45 , and fear conditioning and extinction 15,17 . While their physiological significance remains unknown, these findings suggest that HFOs play a role in the context-and state-dependent deployment of memory and rule-based strategies for goal-directed behavior, functions in which cortico-hippocampo-mesolimbic circuits are implicated.Given that HFOs reflect the population activity of mesolimbic structures [15][16][17][18][19] , patterns of HFO PAC may primarily report the dynamic states of these networks. Our results indicate that θ -HFO coupling may be a signature of functional connectivity between hippocampal and mesolimbic networks, while δ -HFO coupling signifies cortico-mesolimbic connectivity.…”

“…Evidence indicates that inputs from PFC and hippocampus compete for control over mesolimbic circuits [25][26][27][28][29][30][31][32][33] . If HFOs predominantly reflect mesolimbic population activity [15][16][17][18][19] , their phase modulation may reflect the strength of frequency-specific inputs to mesolimbic circuits, either from cortex at δ frequencies or from hippocampus at θ frequencies.…”