Table 2.

Characteristics of crossed and uncrossed nigrotectal neurons in cat SNr (Jiang et al. 2003)

Nigrotectal neurons:	Uncrossed	Crossed
Antidromically activated	Only from ipsilateral SC	Only from contralateral SC
Spontaneous activity	Relatively high: 36.8 ± 18 Hz	Relatively low: 12.5 ± 10 Hz
RF size	Relatively small	Relatively large
Response to visual stimulation	Phasic inhibition	Phasic excitation
Receptive field (RF) location	Congruent with RF in target (ipsilateral) SC	Incongruent with RF in target (contralateral) SC
Topographic distribution of nigrotectal terminals	Relatively focal	Relatively broad

These properties suggest contrasting but complementary roles for the crossed and uncrossed nigrotectal projections; the former to achieve blanket suppression of saccades to any location in the hemifield ipsilateral to the recorded SNr, and the latter to facilitate a saccade to a specific location in the contralateral hemifield. If crossed nigrotectal neurons are indeed modulated by dSPNs via the GPe, they can be considered to implement a ‘crossed direct’ pathway