Functional states of prelimbic and related circuits during the acquisition of a GO/noGO task in rats.

GO/noGO tasks enable assessing decision-making processes and the ability to suppress a specific action according to the context. Here, rats had to discriminate between 2 visual stimuli (GO or noGO) shown on an iPad screen. The execution (for GO) or nonexecution (for noGO) of the selected action (to touch or not the visual display) were reinforced with food. The main goal was to record and to analyze local field potentials collected from cortical and subcortical structures when the visual stimuli were shown on the touch screen and during the subsequent activities. Rats were implanted with recording electrodes in the prelimbic cortex, primary motor cortex, nucleus accumbens septi, basolateral amygdala, dorsolateral and dorsomedial striatum, hippocampal CA1, and mediodorsal thalamic nucleus. Spectral analyses of the collected data demonstrate that the prelimbic cortex was selectively involved in the cognitive and motivational processing of the learning task but not in the execution of reward-directed behaviors. In addition, the other recorded structures presented specific tendencies to be involved in these 2 types of brain activity in response to the presentation of GO or noGO stimuli. Spectral analyses, spectrograms, and coherence between the recorded brain areas indicate their specific involvement in GO vs. noGO tasks.

Locus Ceruleus Terminals in the Fundus StriatiNucleus accumbens septi of the Cat : Electron Microscopic Study / 대한해부학회지

Although the distribution of locus ceruleus terminals has been demonstrated in the fundus striati[nucleus accumbens septi] by light microscopy[Jones & Moore, 1977 ; Mason & Fibiger, 1979 ; Streit or et al., 1979 ; Groenewegen et al., 1980], the synaptic organization of its terminals was not clarified. The purpose of the present investigation was to demonstrate the direct monosynaptic connection of the locus ceruleus terminals to the neuronal elements of the fundus stirati, and to clarify the synaptic structures of its terminals by electron microscopy two days after unilateral electric coagulation of the locus ceruleus. In the ipsilateral fundus striati, many axon terminals undergone dark degeneration were observed. These degenerating terminals containing small clear vesicles have asymmetric synaptic contacts with dendritic spines. Already two days after locus ceruleus lesion, distinct features of terminal degenerations appeared in the fundus striati ; enlarged axon terminals with altered synaptic vesicles, decrease of synaptic vesicles detached from the synaptic site, multiplication of dense bodies and infiltration of floccular material. At the same time, a regressive change occurred in which astrocytic processes encircled totally degenerated synapses spiraled around the synaptic remnants. These observations indicate that monosynaptic noradrenertic afferent connections to the fungus striati are confirmed, and the locus ceruleus terminals characterized by small round vesicles might be formed asymmetrical axo-spinous synapses with spiny neurons in the fundus striati.