Importantly, therefore, any behavioural deficit observed in this patient cannot be attributed to direct damage to ACC or SMA as the boundaries of the lesion do not encroach on the surrounding brain areas. A group of 10 healthy volunteers (7 males) were recruited to act as a control group, mean age = 30.9, SE = .63). All participants were right-handed (mean score = 90, SE = 2.6); Edinburgh Handedness

test (Oldfield, 1971). All reported normal or corrected-to-normal colour-vision SRT1720 purchase and no subject was taking any medication. Participants were reimbursed £8/h to cover travel expenses. A clinical neuropsychological assessment of KP was conducted before and after surgery (Table 1). The assessment included measures of intellectual function (Verbal IQ, Performance IQ), memory (recognition memory test for words and faces) and focal cognitive abilities (Naming skills, VOSP silhouettes and Cube Analysis, Stroop colour-word, Trails B, Symbol learn more Digit Modalities test). In the STOP task

(Fig. 2A) participants are instructed to respond as quickly as possible to the direction of an imperative GO stimulus. In this version of the task, which is a variant of a CHANGE task we have presented previously (Roberts, Anderson, & Husain, 2010), the GO signal was a green arrow pointing left or right, and participants were required to press either a left or right response key using the corresponding index finger (Logan, Cowan, & Davis, 1984). On 50% of trials the GO signal was the only stimulus presented. On the remaining trials the GO signal would be followed, after a variable delay, by a STOP signal: a vertical red bar. In the event of a STOP signal, participants were instructed to attempt

to withhold their response. They were also instructed to avoid waiting for a STOP signal. Throughout the course of the experiment the stimulus onset asynchrony between the GO and STOP signals was varied parametrically Org 27569 using a staircase algorithm in response to the performance of the participant (Levitt, 1971). This was in order to determine the delay at which each participant was able to correctly respond to a STOP signal on 50% of trials; the STOP-signal reaction time (SSRT). In order to account for drift in reaction times, a cubic spline was fitted to the CHANGE-signal reaction time (CSRT) data, guided by the shape of Go responses. This method uses the local variation of the Go distribution to interpolate across STOP trial data points. The resulting distribution provides an approximation of the local Go RT for each Stop trial, which is then used to calculate the SSRT. The CHANGE task (Fig. 2B) employed a similar design to the STOP task. However, instead of a STOP signal, participants were presented with a CHANGE signal – a red arrow pointing in the opposite direction to the GO signal (Roberts et al., 2010).