Intermediate BA-NAc neuronal population engagement during
interactions with the social reward stimulus
Using bulk Ca2+-activity fibre photometry it was
possible to measure the in vivo peri-event activity of int-BA-NAc
neurons during distal or proximal interactions with SR. Evidence for
engagement would constitute an important complement to the c-Fos based
evidence that a substantial proportion of int-BA-NAc neurons are
responsive to SR. Of course, there was the caveat that both putative SR-
or SA-engaged sub-populations of monovalent neurons were recorded from,
and it has been demonstrated that BA-NAc aversion neurons are inhibited
by reward . Despite this, in both distal and proximal phases of the SR
test, there were consistent and transient increases in BA-NAc neuron
Ca2+ activity coincident with episodes of socio-sexual
behaviour. In the distal-SR phase, the activity increase occurred at 3-4
sec after social episode onset even though episodes were typically of
1-2 sec duration, perhaps reflecting post-contact processing of sensory
(e.g. olfactory) stimuli. In the proximal-SR phase, the activity
increase occurred at 2 sec after social episode onset, perhaps
reflecting engagement during socio-sexual behavioural events including
mounting and copulation . Integrating the findings with those from
electrophysiological studies of local field potentials, the extent to
which groups of BA glutamate neurons fire in a synchronized manner
during interactions with emotional stimuli is positively associated with
gamma oscillations; such synchronicity might explain how relatively
small populations of neurons, such as BA-NAc neurons, can make marked
contributions to circuitries underlying the processing of emotional
stimuli and related behavior .