Exp Brain Res (2011) 214:427–435 diYculty understanding task instructions and the computer tasks. All included patients had MMSE scores higher than 20; their scores reXected the orientation and memory prob- lems associated with their diagnosis. None of the patients fulWlled the criteria for alcohol dementia (Oslin et al. 1998). All patients underwent a comprehensive neuropsychologi- cal evaluation (see Table 1), which revealed some execu- tive disorders, in addition to amnesic problems, but most had intact visuospatial abilities, as measured with the com- plex Wgure of Rey. The patients were matched for age and estimated general intelligence, measured with the Dutch version of the National Adult Reading Test (NART; Nelson and O'Connell 1978), with 14 healthy controls (seven men) who were either recruited from the hospital’s staV or volun- teers; none had a history of neurological or psychiatric dis- ease or subjective memory complaints. Their demographic details are given in Table 1. There were no signiWcant diVerences between the control and patient groups in age (t(32) = ¡1.16, P = 0.255) and estimated intelligence (t(32) = 1.56, P = 0.128). All participants gave their written informed consent. Table 1 Demographic variables for the KorsakoV patients and the controls, as well as the performance of the KorsakoV patients on stan- dard neuropsychological evaluation (mean, SD between brackets, % impaired patients between squared brackets, based on 1.5 SD below normative mean or established cutoV scores) Age Sex distribution (m:f) NART-IQ MMSE RBMTa TMT—Ab TMT—Interferenceb Stroop Color Word Test—Interferenceb Tower of Londonb Rey-Osterrieth Complex Figure—Copyc KorsakoV patients (n = 20) 52.90 (7.8) 16:4 98.85 (12.8) 25.70 (2.1) [5%]d 2.78 (2.24) [95%]e 2.08 (1.70) [60%] 0.53 (1.46) [27%] ¡0.72 (0.96) [25%] ¡1.78 (1.87) [55%] 43.75 (14.38) [11%] – – Healthy controls (n = 14) 49.3 (10.4) 7:7 105.8 (12.8) 29.1 (2.1) – – – – NART-IQ Dutch version of the National Adult Reading Task—Intelli- gence Quotient, MMSE Mini-Mental State Examination, RBMT River- mead Behavioral Memory Test, TMT Trail Making Test a Standard screening score (0–12) b Standardized z scores c Percentile scores d One patient performed below the established cutoV of 24, but this pa- tient did not fulWll the clinical criteria for dementia e One patient just failed to reach the established cutoV on the RBMT, but this patient had a severe memory impairment on the California Ver- bal Learning Test, had a lack of insight into his impairments and was spontaneously confabulating, thus fulWlling all criteria for KorsakoV’s syndrome 429 Tasks and procedure For the SRTT, the participants were seated in front of a computer monitor with a four-key response box placed directly below it. Four horizontally aligned squares, reXect- ing the alignment of the response keys, were always visu- ally displayed at the bottom of the screen. In each trial, a stimulus (an asterisk) would appear in one of the four posi- tions, but never in the same position twice in succession. The participants were instructed to press the key that corre- sponded to the square in which the asterisk appeared as rap- idly, but also as accurately, as possible. The asterisk remained on the screen until the correct button had been pressed, after which it disappeared. The next stimulus appeared after 500 ms. The actual test comprised six trial blocks, each consisting of 100 trials. In the Wrst block (R1), the stimuli were presented in a pseudo-random order. In the next four blocks (L1-L4), a Wxed ten-trial sequence (D–B– C–A–C–B–D–C–B–A) was repeated ten times, and in the sixth block (R2), the stimuli were again presented in a pseudo-random order. The participants were not informed about the repeated sequence. The participants sat in front of the computer to perform the Pattern Learning Task on a sheet of paper that was Wxed to a digitizer (WACOM) using a normal-looking, nonink pen to control the cursor on the screen. Four circles (2.6 cm in diameter) were always visible on the screen. In each trial, one circle turned red (see Fig. 1). Participants were instructed to move the cursor (a blue dot of 0.9-cm diameter) toward the red target by means of the pen as quickly as possible. After the cursor had been inside the tar- get for 200 ms, a beep lasting 200 ms sounded, which indi- cated that the next trial would start, with another circle turning red. The target remained red until the cursor had been moved inside the target. The actual test comprised six blocks of 100 trials each, with a short break (several min- utes) in between the blocks. A Wrst pseudo-random trial block (R1) was followed by four blocks (L1-L4) with a Wxed sequence that was repeated ten times, after which in the sixth block (R2) another pseudo-random sequence of stimuli was presented. Again, the participants were not informed about the repeated sequence. For more methodo- logical details on the used SRTT and the PLT, see Van Til- borg and Hulstijn (2010). All participants were examined individually. They always performed the MMSE as the second and the Dutch version of the NART as the fourth component of the test session. Half of the participants started with the SRTT, the other half with the PLT. After the test session, all partici- pants were asked whether they had noticed anything about the tasks, to establish whether they had become aware of the tasks’ Wxed sequences. They could not be asked after completion of individual tests because our experimental 123