Editing Substantia nigra (section)

===Pars reticulata===
{{main|Pars reticulata#Function}}
The [[pars reticulata]] of the substantia nigra is an important processing center in the basal ganglia. The GABAergic neurons in the pars reticulata convey the final processed signals of the [[basal ganglia]] to the [[thalamus]] and [[superior colliculus]]. In addition, the pars reticulata also inhibits dopaminergic activity in the [[pars compacta]] via axon collaterals, although the functional organization of these connections remains unclear.

The GABAergic neurons of the pars reticulata spontaneously fire [[action potential]]s. In rats, the frequency of action potentials is roughly 25&nbsp;Hz.<ref>{{cite journal | vauthors = Gernert M, Fedrowitz M, Wlaz P, Löscher W | title = Subregional changes in discharge rate, pattern, and drug sensitivity of putative GABAergic nigral neurons in the kindling model of epilepsy | journal = The European Journal of Neuroscience | volume = 20 | issue = 9 | pages = 2377–86 | date = November 2004 | pmid = 15525279 | doi = 10.1111/j.1460-9568.2004.03699.x | s2cid = 24485657 | doi-access = free }}</ref> The purpose of these spontaneous action potentials is to inhibit targets of the basal ganglia, and decreases in inhibition are associated with movement.<ref>{{cite journal | vauthors = Sato M, Hikosaka O | title = Role of primate substantia nigra pars reticulata in reward-oriented saccadic eye movement | journal = The Journal of Neuroscience | volume = 22 | issue = 6 | pages = 2363–73 | date = March 2002 | pmid = 11896175 | pmc = 6758246 | doi = 10.1523/JNEUROSCI.22-06-02363.2002 }}</ref> The subthalamic nucleus gives excitatory input that modulates the rate of firing of these spontaneous action potentials. However, lesion of the subthalamic nucleus leads to only a 20% decrease in pars reticulata firing rate, suggesting that the generation of action potentials in the pars reticulata is largely autonomous,<ref>{{cite journal | vauthors = Zahr NM, Martin LP, Waszczak BL | title = Subthalamic nucleus lesions alter basal and dopamine agonist stimulated electrophysiological output from the rat basal ganglia | journal = Synapse | volume = 54 | issue = 2 | pages = 119–28 | date = November 2004 | pmid = 15352137 | doi = 10.1002/syn.20064 | s2cid = 10239473 }}</ref> as exemplified by the pars reticulata's role in [[saccade|saccadic eye movement]]. A group of GABAergic neurons from the pars reticulata projects to the superior colliculus, exhibiting a high level of sustained inhibitory activity.<ref>{{cite journal | vauthors = Hikosaka O, Wurtz RH | title = Visual and oculomotor functions of monkey substantia nigra pars reticulata. III. Memory-contingent visual and saccade responses | journal = Journal of Neurophysiology | volume = 49 | issue = 5 | pages = 1268–84 | date = May 1983 | pmid = 6864250 | doi = 10.1152/jn.1983.49.5.1268 }}</ref> Projections from the [[caudate nucleus]] to the superior colliculus also modulate saccadic eye movement.
Altered patterns of pars reticulata firing such as single-spike or burst firing are found in [[Parkinson's disease]]<ref>{{cite journal | vauthors = Tseng KY, Riquelme LA, Belforte JE, Pazo JH, Murer MG | title = Substantia nigra pars reticulata units in 6-hydroxydopamine-lesioned rats: responses to striatal D2 dopamine receptor stimulation and subthalamic lesions | journal = The European Journal of Neuroscience | volume = 12 | issue = 1 | pages = 247–56 | date = January 2000 | pmid = 10651879 | doi = 10.1046/j.1460-9568.2000.00910.x | s2cid = 22886675 | hdl = 11336/39220 | hdl-access = free }}</ref> and [[epilepsy]].<ref>{{cite journal | vauthors = Deransart C, Hellwig B, Heupel-Reuter M, Léger JF, Heck D, Lücking CH | title = Single-unit analysis of substantia nigra pars reticulata neurons in freely behaving rats with genetic absence epilepsy | journal = Epilepsia | volume = 44 | issue = 12 | pages = 1513–20 | date = December 2003 | pmid = 14636321 | doi = 10.1111/j.0013-9580.2003.26603.x | s2cid = 6661257 }}</ref>