These results also fit well with recent local field potential (LFP) recordings in human STN that show activity changes on successful stop trials preceding SSRT [30]. However, for a number of reasons, these single unit recordings in the basal ganglia need to be replicated in non-human primates. First, lesion studies in primates have not in all Selleck ERK inhibitor cases conclusively supported the gating hypothesis [31•]. Second, the STN activity pattern found in the rat is different than activity pattern in primate STN in a
related impulse control task, in which an automatic response had to be overridden to generate a voluntary response 32 and 33]. In particular, the primate STN neurons responded selectively when the automatic response was successfully suppressed and this activity difference predicted behavior. This is hard to reconcile with the unspecific response in the rodent STN neurons. Third, the head movement that has to be controlled by the rat is a very complex movement, involving multiple body parts and a number of different muscles. In contrast, most other stop signal experiments in monkeys have used simpler movements involving just one effector. Because of this, it is not entirely clear at what level of
motor representation the basal ganglia neurons operate that were recorded in the rat. They could either represent the entire movement on a more abstract level or they could represent the control of specific muscles. Lastly, given the mixed results in motor cortex, it is very important Meloxicam to understand the mechanistic relationship and timing between the gating INCB018424 in vitro in the basal ganglia and changes in motor cortex. A final potential
locus of inhibitory control in the skeletomotor system is the spinal cord [34]. Recording in the spinal interneurons of behaving monkeys showed evidence for inhibitory suppression of motor activity during an instructed delay preceding a wrist response [35]. These neurons might be the closest functional equivalent to omnipause cells that has been found so far in the skeletomotor system. It will be very important to understand the input controlling these inhibitory interneurons and to better understand their role in the suppression of motor responses. Cognitive control operates via two distinct operating modes: proactive control and reactive control 36 and 37]. Proactive control relies upon the anticipation and prevention of interference before it occurs, whereas reactive control relies upon the detection and resolution of interference after its onset. Reactive control is recruited as a late correction mechanism and has been the focus of most of the stop signal research. In contrast, proactive control adjusts the response selection and preparation process in anticipation of known task demands. In the context of the stop signal task, proactive control is mostly related to a regulation of the level of excitability of the motor system.