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The appearance of a salient stimulus evokes a series of orienting responses including saccades and pupil size to prepare the body for appropriate action. The midbrain superior colliculus (SC) that receives critical control signals from the frontal eye field (FEF) is hypothesized to coordinate all components of orienting. It has shown recently that the FEF, together with the SC, is also importantly involved in the control of pupil size, in addition to its well-documented role in eye movements. Although the role of the FEF in pupil size is demonstrated in monkeys, its role in human pupil responses and the coordination between pupil size and saccades remains to be established. Through applying continuous theta-burst stimulation over the right FEF and vertex, we investigated the role of the FEF in human pupil and saccade responses evoked by a salient stimulus, and the coordination between pupil size and saccades. Our results showed that neither saccade reaction times (SRT) nor pupil responses evoked by salient stimuli were modulated by FEF stimulation. In contrast, the correlation between pupil size and SRTs in the contralateral stimulus condition was diminished with FEF stimulation, but intact with vertex stimulation. Moreover, FEF stimulation effects between saccade and pupil responses associated with salient stimuli correlated across participants. This is the first transcranial magnetic stimulation (TMS) study on the pupil orienting response, and our findings suggest that human FEF was involved in coordinating pupil size and saccades, but not involved in the control of pupil orienting responses.

The executive control of voluntary action involves not only choosing from a range of possible actions but also the inhibition of responses as circumstances demand. Recent studies have demonstrated that many clinical populations, such as people with attention-deficit hyperactivity disorder, exhibit difficulties in inhibitory control. One prefrontal area that has been particularly associated with inhibitory control is the pre-supplementary motor area (Pre-SMA). Here we applied non-invasive transcranial direct current stimulation (tDCS) over Pre-SMA to test its role in this behavior. tDCS allows for current to be applied in two directions to selectively excite or suppress the neural activity of Pre-SMA. Our results showed that anodal tDCS improved efficiency of inhibitory control. Conversely, cathodal tDCS showed a tendency towards impaired inhibitory control. To our knowledge, this is the first demonstration of non-invasive intervention tDCS altering subjects' inhibitory control. These results further our understanding of the neural bases of inhibitory control and suggest a possible therapeutic intervention method for clinical populations.

Predictability in the visual environment provides a powerful cue for efficient processing of scenes and objects. Recently, studies have suggested that the directionality and magnitude of saccade curvature can be informative as to how the visual system processes predictive information. The present study investigated the role of the right posterior parietal cortex (rPPC) in shaping saccade curvatures in the context of predictive and non‐predictive visual cues. We used an orienting paradigm that incorporated manipulation of target location predictability and delivered transcranial magnetic stimulation (TMS) over rPPC. Participants were presented with either an informative or uninformative cue to upcoming target locations. Our results showed that rPPC TMS generally increased saccade latency and saccade error rates. Intriguingly, rPPC TMS increased curvatures away from the distractor only when the target location was unpredictable and decreased saccadic errors towards the distractor. These effects on curvature and accuracy were not present when the target location was predictable. These results dissociate the strong contingency between saccade latency and saccade curvature and also indicate that rPPC plays an important role in allocating and suppressing attention to distractors when the target demands visual disambiguation. Furthermore, the present study suggests that, like the frontal eye fields, rPPC is critically involved in determining saccade curvature and the generation of saccadic behaviors under conditions of differing target predictability. Hum Brain Mapp, 2011. © 2011 Wiley‐Liss, Inc.

Although both the presupplementary motor area (pre-SMA) and the right inferior frontal gyrus (rIFG) have been demonstrated to be critical for response inhibition, there is still considerable disagreement over the roles they play in the process. In the present study, we investigated the causal relations of the pre-SMA and the rIFG in a conditional stop-signal task by applying offline theta-burst transcranial magnetic stimulation. The task introduced a continue condition, which requires the same motor response as in a go trial but captures attention as in a stop trial. We found great individual differences in the amount of slowing on continue trials. Temporary suppression of pre-SMA activity prolonged the continue RT in participants who slowed little in response to continue trials, whereas disruption of the rIFG did not lead to significant changes in performance irrespective of the degree of slowing. Our results contribute to the understanding of the role of the pre-SMA by providing causal evidence that it is involved in response slowing on continue trials during conditional stopping, and it is likely that its efficiency in updating motor planning and reinitiating an inhibited response was associated with the amount of slowing.

The dorsal attentional network is known for its role in directing top-down visual attention towards task-relevant stimuli. This goal-directed nature of the dorsal network makes it a suitable candidate for processing and extracting predictive information from the visual environment. In this mini review we briefly summarize some of the findings that delineate the neural substrates that contribute to predictive learning at both levels within the dorsal attentional system: including the frontal eye field and posterior parietal cortex. We also discuss the similarities and differences between these two regions when it comes to learning predictive information. The current findings from the literature suggest that the frontal eye fields may be more involved in top-down spatial attention, whereas the parietal cortex is involved in processing task-relevant attentional influences driven by stimulus salience, both contribute to the processing of predictive cues at different time points.

The interaction between goal‐directed and stimulus‐driven attentional control allows humans to rapidly reorient to relevant objects outside the focus of attention—a phenomenon termed contingent reorienting. Neuroimaging studies have observed activation of the ventral and dorsal attentional networks, but specific involvement of each network remains unclear. The present study aimed to determine whether both networks are critical to the processes of top‐down contingent reorienting. To this end, we combined the contingent attentional capture paradigm with the use of transcranial magnetic stimulation (TMS) to interfere with temporoparietal junction (TPJ; ventral network) and frontal eye field (dorsal network) activity. The results showed that only right TPJ (rTPJ) TMS modulated contingent orienting. Furthermore, this modulation was highly dependent on visual fields: rTPJ TMS increased contingent capture in the left visual field and decreased the effect in the right visual field. These results demonstrate a critical involvement of the ventral network in attentional reorienting and reveal the spatial selectivity within such network. Hum Brain Mapp, 2013. © 2012 Wiley Periodicals, Inc.

It is commonly accepted that right posterior parietal cortex (PPC) plays an important role in updating spatial representations, directing visuospatial attention, and planning actions. However, recent studies suggest that right PPC may also be involved in processes that are more closely associated with our visual awareness as its activation level positively correlates with successful conscious change detection (Beck, D.M., Rees, G., Frith, C.D., & Lavie, N. (2001). Neural correlates of change detection and change blindness. Nature Neuroscience, 4, 645–650.). Furthermore, disruption of its activity increases the occurrences of change blindness, thus suggesting a causal role for right PPC in change detection (Beck, D.M., Muggleton, N., Walsh, V., & Lavie, N. (2006). Right parietal cortex plays a critical role in change blindness. Cerebral Cortex, 16, 712–717.). In the context of a 1-shot change detection paradigm, we applied transcranial magnetic stimulation (TMS) during different time intervals to elucidate the temporally precise involvement of PPC in change detection. While subjects attempted to detect changes between two image sets separated by a brief time interval, TMS was applied either during the presentation of picture 1 when subjects were encoding and maintaining information into visual short-term memory, or picture 2 when subjects were retrieving information relating to picture 1 and comparing it to picture 2. Our results show that change blindness occurred more often when TMS was applied during the viewing of picture 1, which implies that right PPC plays a crucial role in the processes of encoding and maintaining information in visual short-term memory. In addition, since our stimuli did not involve changes in spatial locations, our findings also support previous studies suggesting that PPC may be involved in the processes of encoding non-spatial visual information (Todd, J.J. & Marois, R. (2004). Capacity limit of visual short-term memory in human posterior parietal cortex. Nature, 428, 751–754.).