428 crucial for storing information in the neocortex that has been integrated by the hippocampus. Mayes (1988) suggested that patients with KorsakoV’s syndrome especially have prob- lems with memory for contextual information, such as spatial relations between stimuli, and indeed many studies have reported spatial memory deWcits in these patients (Postma et al. 2006; Van Asselen et al. 2005). These studies involved explicit memory; however, evidence concerning implicit spatial memory deWcits is less conclusive. While implicit spatial memory in patients with KorsakoV’s syndrome was reported to be spared in an object-location memory task (Postma et al. 2008), Chun and Phelps (1999) reported it to be impaired in a group of amnesic patients that also included KorsakoV’s patients. Because of these contradictory Wndings, we investigated spatial and nonspatial implicit motor learn- ing in patients with KorsakoV’s syndrome and in healthy controls, using two implicit motor learning tasks. Motor learning refers to the increasing spatial and temporal accu- racy of movements with practice (Willingham 1999). It involves more than merely gaining new movement patterns, such as in sports, and is generally deWned as a process of acquiring the capability for producing skilled actions as a result of practice and which leads to relatively permanent changes in this capability (Schmidt and Wrisberg 2000). We focused on implicit sequence learning, i.e., learning the order of the submovements of an action. To this end, we used two paradigms: a standard Serial Reaction Time task (SRTT) and a newly developed, more spatially demanding, Pattern Learning task (PLT). The latter is based on the SRTT para- digm but requires the manipulation of a hand-held stylus (Van Tilborg and Hulstijn 2010). The SRTT developed by Nissen and Bullemer (1987) is one of the most widely used tasks to study the implicit sequence learning in experimental research. In this task, participants are presented with successive visual stimuli that appear at diVerent screen locations, to which they are asked to respond by pressing spatially corresponding keys. Initially, the stimuli are presented in a random order, but at some point in time, and unknown to the participants, they are presented in a Wxed sequence. After several Wxed- sequence blocks, the Wxed sequence switches to a random stimulus order, to test whether sequence learning has occurred in the preceding trial blocks. An increase in reac- tion time after this switch reXects sequence-speciWc learn- ing. Two studies in which the SRTT was administered to patients with KorsakoV’s syndrome showed that implicit learning was intact in these patients (Nissen and Bullemer 1987; Nissen et al. 1989). In contrast, a study using a diVer- ent implicit motor learning task, a maze task, found implicit learning to be impaired in patients with KorsakoV’s syn- drome (Nissen et al. 1989). This suggests that implicit learning may be task dependent. The SRTT is an implicit learning task in which sequences of four diVerent Wnger 123 Exp Brain Res (2011) 214:427–435 responses are learned, resembling learning to type fre- quently used words. In this task, actions vary little and responses are diVerentiated by only four spatial locations. The SRTT shows little spatial variation regarding the nature of the response (pushing a button with one Wnger); the responses are four diVerent Wnger movements. Spatial aspects are suggested to be important in motor learning (Witt and Willingham 2006). Witt and Willingham stated that most types of motor skills require learning a sequence of diVerent actions. For example, maze learning involves learning to correctly manipulate an object via a series of movements into diVerent directions, which is com- parable to learning to serve in tennis. Thus, spatial aspects play a dominant role in maze learning. Also in the PLT, where a pen is moved toward diVerent targets, spatial aspects are more involved because the pen can be moved in three possible directions toward the target, dependent on the previous target location. In particular, the planning and execution of the motor response in the PLT have a strong spatial character. Chun and Phelps (1999) earlier reported that amnesic patients had normal implicit skills learning on nonspatial tasks, but demonstrated deWcits in implicit spa- tial learning, which suggests that it is crucial to take the spatial aspects of tasks into account. We investigated spatial and nonspatial implicit motor learning in patients with KorsakoV’s syndrome and in healthy controls, using two implicit learning tasks that require diVerent types of sequential motor actions: the clas- sic SRTT and the PLT. We expected that the patients with KorsakoV’s syndrome would show intact implicit learning on the SRTT, but compromised implicit spatial memory performance on the PLT. Methods Participants Twenty patients with KorsakoV’s syndrome (16 men), inpa- tients of the KorsakoV Clinic of the Vincent van Gogh Institute for Psychiatry, Venray, the Netherlands, partici- pated in this study. All met the criteria for DSM-IV Alco- hol-Induced Persisting Amnestic Disorder (American Psychiatric Association 1994) and the criteria for Kor- sakoV’s syndrome described by Kopelman (2002). All patients had severe amnesia, measured with the Dutch ver- sion of the Rivermead Behavioral Memory Test (Wilson et al. 1985) (see Table 1), and an extensive history of alco- holism and nutritional depletion, veriWed by medical charts or family reports. The Mini-Mental State Examination (MMSE; Folstein et al. 1975) was administered to assess the overall cognitive functioning. Patients with a MMSE score below 17 were excluded because they might have