Neuronal responses to target onset in oculomotor and somatomotor parietal circuits differ markedly in a choice task

Abstract

Kubanek J, Wang C, Snyder LH. Neuronal responses to target onset in oculomotor and somatomotor parietal circuits differ markedly in a choice task. J Neurophysiol 110: 2247-2256, 2013. First published August 21, 2013 doi:10.1152/jn.00968.2012We often look at and sometimes reach for visible targets. Looking at a target is fast and relatively easy. By comparison, reaching for an object is slower and is associated with a larger cost. We hypothesized that, as a result of these differences, abrupt visual onsets may drive the circuits involved in saccade planning more directly and with less intermediate regulation than the circuits involved in reach planning. To test this hypothesis, we recorded discharge activity of neurons in the parietal oculomotor system (area LIP) and in the parietal somatomotor system (area PRR) while monkeys performed a visually guided movement task and a choice task. We found that in the visually guided movement task LIP neurons show a prominent transient response to target onset. PRR neurons also show a transient response, although this response is reduced in amplitude, is delayed, and has a slower rise time compared with LIP. A more striking difference is observed in the choice task. The transient response of PRR neurons is almost completely abolished and replaced with a slow buildup of activity, while the LIP response is merely delayed and reduced in amplitude. Our findings suggest that the oculomotor system is more closely and obligatorily coupled to the visual system, whereas the somatomotor system operates in a more discriminating manner.LIP; decision; parietal reach region; reward; transient BEHAVIOR IS OFTEN GUIDED OR influenced by objects appearing on the visual scene. The appearance or movement of an object often elicits a rapid eye movement, or saccade, to that object. The benefit of this behavior is to bring the object onto the fovea to acquire more detailed visual information about it. Saccades can be deployed quickly and therefore are relatively inexpensive. In comparison, the appearance or movement of an object rarely elicits an immediate reach, although a subject may choose to reach after a delay. Reaching is slower and requires a greater commitment of resources and more involved planning, including the trajectory to follow and what the hand will do when it arrives. In general, we are much more likely to immediately look at a new visual target than we are to immediately reach for it.Targets of visually guided saccades and reaches are encoded by many neurons in posterior parietal cortex. Specifically, neurons in the lateral intraparietal area (LIP) and the parietal reach region (PRR) respond to the appearance of a taskrelevant visual target in their response field (RF) with a transient increase in activity (Goldberg and Bruce 1985;Blatt et al. 1990;Colby et al. 1996;Gottlieb et al. 1998;Colby and Goldberg 1999;Snyder et al. 1997Snyder et al. , 2000Calton et al. 2002;Scherberger and Andersen 2007; Andersen 2007, 2011;Pesaran et al. 2008). The parietal regions LIP and PRR might th...

Single-unit activity in marmoset posterior parietal cortex in a gap saccade task

“…Previous studies have identified visual neurons (Andersen et al, 1985), e.g. those responding to the onset (Gottlieb et al, 1998;Kubanek et al, 2013) or offset (Ben Hamed and Duhamel, 2002) of salient or relevant targets; as well as neurons responsive to both visual target and saccadic onset (Colby et al, 1996;Gottlieb et al, 2005), with differential distribution along the dorsal-ventral extent of the macaque LIP (Chen et al, 2016). Similarly, in the marmoset PPC, we observed visual neurons responsive to fixation offset and those responsive to target onset and saccadic onset.…”

Single unit activity in marmoset posterior parietal cortex in a gap saccade task

“…Previous studies have identified visual neurons (Andersen et al, 1985), e.g. those responding to the onset (Gottlieb et al, 1998;Kubanek et al, 2013) or offset (Ben Hamed and Duhamel, 2002) of salient or relevant targets; as well as neurons responsive to both visual target and saccadic onset (Colby et al, 1996;Gottlieb et al, 2005), with differential distribution along the dorsal-ventral extent of the macaque LIP (Chen et al, 2016). Similarly, in the marmoset PPC, we observed visual neurons responsive to fixation offset and those responsive to target onset and saccadic onset.…”

LIP activity in the interstimulus interval of a change detection task biases the behavioral response

“…The activity can be thought of as representing priority (Bisley and Goldberg 2010), salience (Gottlieb 2007), or a form of value (Kubanek and Snyder 2015;Louie et al 2011;Louie and Glimcher 2010;Sugrue et al 2004), but in all cases it is used to decide where to place covert (Bisley and Goldberg 2003; Herrington and Assad 2010) and overt (Ipata et al 2006;Kubanek et al 2013;Mazzoni et al 1996) attention. We do not wish to use the present data to reopen the debate and claim that LIP activity represents motor planning and not attention; instead we suggest that the guidance of visuospatial attention is part of the process of deciding where to look.…”