Cortical regulation of dopaminergic neurons: role of the midbrain superior colliculus

Abstract

Dopaminergic (DA) neurons respond to stimuli in a wide range of modalities, although the origin of the afferent sensory signals has only recently begun to emerge. In the case of vision, an important source of short-latency sensory information seems to be the midbrain superior colliculus (SC). However, longer-latency responses have been identified that are less compatible with the primitive perceptual capacities of the colliculus. Rather, they seem more in keeping with the processing capabilities of the cortex. Given that there are robust projections from the cortex to the SC, we examined whether cortical information could reach DA neurons via a relay in the colliculus. The somatosensory barrel cortex was stimulated electrically in the anesthetized rat with either single pulses or pulse trains. Although single pulses produced small phasic activations in the colliculus, they did not elicit responses in the majority of DA neurons. However, after disinhibitory intracollicular injections of the GABAA antagonist bicuculline, collicular responses were substantially enhanced and previously unresponsive DA neurons now exhibited phasic excitations or inhibitions. Pulse trains applied to the cortex led to phasic changes (excitations to inhibitions) in the activity of DA neurons at baseline. These were blocked or attenuated by intracollicular administration of the GABAA agonist muscimol. Taken together, the results indicate that the cortex can communicate with DA neurons via a relay in the SC. As a consequence, DA neuronal activity reflecting the unexpected occurrence of salient events and that signaling more complex stimulus properties may have a common origin.

Netrin‐1/ DCC ‐mediated PLC γ1 activation is required for axon guidance and brain structure development

“…Our results have demonstrated that the regulation of neural development by netrin‐1/DCC signaling may be mediated, at least in part, through the activation of PLCγ1, which controls key steps in the axonal projection of mDA neurons as well as CC structural formation. In particular, mDA neurons have been implicated in various kinds of neurological disorders such as addiction, parkinsonism, schizophrenia, sleep abnormalities, and ADHD, with some evidence indicating that structural changes in neuronal networks may in part underlie the pathogenesis of these disorders . Although axon guidance events are crucial for the correct development of mDA pathways, their precise role during the pathogenesis of mDA system‐related disorders has not been established.…”

The Computational Properties of a Simplified Cortical Column Model

“…Watabe-Uchida et al [ 23 ] found that dopaminergic neurons in the ventral tegmental area and substantia nigra pars compacta receive sparse input from the deep layers of cortex (for example their Fig 5 ). Because of the well established role of these midbrain structures in valuation, motivation, and reinforcement learning, these authors suggest that these dopaminergic neurons might “calculate the difference between the expected and actual reward (i.e., reward prediction errors).” While speculative, it is possible that this prediction is calculated cortically and relayed either directly or indirectly [ 35 ].…”

Evolutionarily conserved organization of the dopaminergic system in lamprey: SNc/VTA afferent and efferent connectivity and D2 receptor expression

“…We have also found strong innervation from the lateral pallium to the optic tectum, especially abundant in the deep output layer. Our results suggest that the lateral pallium/cortex may, in addition to direct projections, send information to the SNc through the tectum/ superior colliculus, a pathway that was very recently shown in rats (Bertram et al, 2013).…”