Marieke van Asselen

How the brain remembers and forgets where things are: The neurocognition of object location memory

Remembering where things are - object-location memory - is essential for daily-life functioning. Functionally, it can be decomposed into at least three distinct processing mechanisms: (a) object processing, (b) spatial-location processing and (c) object to location binding. A neurocognitive model is sketched, which posits a mostly bilateral ventral cortical network supporting object-identity memory, a left fronto-parietal circuit for categorical position processing and working memory aspects, and a right fronto-parietal circuit for coordinate position processing and working memory. Medial temporal lobes and in particular the hippocampus appear essential for object-location binding. It is speculated that categorical object-location binding and episodic memory binding in general depend more on the left-sided areas, whereas coordinate object-location processing and navigation in large scale space involve the right-sided counterparts. The various object-location memory components differ in the extent to which they are automatized or require central effort. While automatic routines protect against brain damage, neural deficits might potentially also lead to a shift upon the automatic-effortful continuum.

Spatial Working Memory and Contextual Cueing in Patients with Korsakoff Amnesia

The current study investigated the effect of Korsakoff syndrome on memory for spatial information and, in particular, the effect of contextual cueing on spatial memory retention. Twenty Korsakoff patients and a comparison group of 22 age- and education- matched participants were tested with a newly developed spatial search task (the Box task). Participants were asked to search through a number of boxes shown at different locations on a touch-sensitive computer screen to find a target object. In subsequent trials, new objects were hidden in boxes that were previously empty. Two conditions were used: the boxes were either completely identical or had different colors serving as a cue. Within-search errors were made if a participant returned to an already searched box; between-search errors occurred if a participant returned to a box that already contained a target item. Moreover, the use of a strategy to remember the locations of the target objects was calculated. The results show that Korsakoff patients make more within and between-search errors than the comparison group, and although they were able to apply a search strategy, it did not help them to remember the locations of the targets. Interestingly, whereas the comparison group benefited from color cues that were given to the boxes, Korsakoff patients failed to do so. The authors would like to thank Olga Keuper for her help with collection and Rob Broekmans for programming the Box Task. This research was supported by a grant (# 440-20-00) from the Netherlands Organization for Scientific Research (NWO). Roy Kessels was supported by a VENI grant from NWO (# 451-02-037).

A Direct Comparison of Local-Global Integration in Autism and other Developmental Disorders: Implications for the Central Coherence Hypothesis

The weak central coherence hypothesis represents one of the current explanatory models in Autism Spectrum Disorders (ASD). Several experimental paradigms based on hierarchical figures have been used to test this controversial account. We addressed this hypothesis by testing central coherence in ASD (n = 19 with intellectual disability and n = 20 without intellectual disability), Williams syndrome (WS, n = 18), matched controls with intellectual disability (n = 20) and chronological age-matched controls (n = 20). We predicted that central coherence should be most impaired in ASD for the weak central coherence account to hold true. An alternative account includes dorsal stream dysfunction which dominates in WS. Central coherence was first measured by requiring subjects to perform local/global preference judgments using hierarchical figures under 6 different experimental settings (memory and perception tasks with 3 distinct geometries with and without local/global manipulations). We replicated these experiments under 4 additional conditions (memory/perception*local/global) in which subjects reported the correct local or global configurations. Finally, we used a visuoconstructive task to measure local/global perceptual interference. WS participants were the most impaired in central coherence whereas ASD participants showed a pattern of coherence loss found in other studies only in four task conditions favoring local analysis but it tended to disappear when matching for intellectual disability. We conclude that abnormal central coherence does not provide a comprehensive explanation of ASD deficits and is more prominent in populations, namely WS, characterized by strongly impaired dorsal stream functioning and other phenotypic traits that contrast with the autistic phenotype. Taken together these findings suggest that other mechanisms such as dorsal stream deficits (largest in WS) may underlie impaired central coherence.

Neural correlates of human wayfinding in stroke patients.

Wayfinding is a complex cognitive function involving different types of information, such as knowledge about landmarks and direction information. This variety of processes suggest that multiple neural mechanisms are involved, e.g., the hippocampal system, the posterior parietal and temporal cortical areas. Although patient studies and imaging studies have given important insights in the exact neural circuitry underlying wayfinding, many controversies remain. Therefore, the current study sets out to further examine the neuroanatomical correlates of wayfinding in a sample of 31 stroke patients with unilateral lesions, tested with a series of different wayfinding tasks, including landmark recognition, landmark ordering, route reversal and route drawing. For all patients, the exact location of their lesion was determined using CT or MRI scans. Based on existing literature, a number of relevant brain areas were demarcated, after which the extent of damage to these areas was determined for each patient separately. Performance on the landmark recognition task was impaired by damage to the right hippocampal formation, whereas a weak correlation was found between damage to the dorsolateral prefrontal cortex and processing the order of the landmarks. Several brain areas were found to be involved in retracing a route from the end to the beginning, including the right hippocampal formation, the right posterior parietal cortex, the right dorsolateral prefrontal cortex and the right temporal lobe. Finally, damage to the right temporal lobe impaired the ability to draw the route.

The role of the basal ganglia in implicit contextual learning: A study of Parkinson's disease

Implicit contextual learning refers to the ability to memorize contextual information from our environment. This contextual information can then be used to guide our attention to a specific location. Although the medial temporal lobe is important for this type of learning, the basal ganglia might also be involved considering its role in many implicit learning processes. In order to understand the role of the basal ganglia in this top-down process, a group of non-demented early-stage Parkinsons patients were tested with a contextual cueing task. In this visual search task, subjects have to quickly locate a target among a number of distractors. To test implicit contextual learning, some of the configurations are repeated during the experiment, resulting in faster responses. A significant interaction effect was found between Group and Configuration, indicating that the control subjects responded faster when the spatial context was repeated, whereas Parkinsons patients failed to do so. These results, showing that the contextual cueing effect was significantly different for the patients than for the controls, suggest an important role for the basal ganglia in implicit contextual learning, thus extending previous findings of medial temporal lobe involvement. The basal ganglia are therefore not only involved in implicit motor learning, but may also have a role in purely visual implicit learning.

Are space and time automatically integrated in episodic memory

The aim of the present study was to determine to what extent spatial and temporal features are automatically integrated during encoding in episodic memory. Both nameable and non-nameable stimuli were presented sequentially at different locations on a computer screen. Mixed and pure blocks of trials were used. In the mixed blocks participants were instructed to focus either on the spatial or the temporal order of the objects, as on the majority of the trials recall of this feature was tested (expected trials). However, on a few trials participants had to reproduce the other feature (unexpected trials). In the pure blocks either the spatial or the temporal order of the objects was tested on all trials. More errors were made on unexpected than on expected trials of the mixed blocks. Moreover, no primacy or recency effects were found when performance on the spatial task was plotted as a function of the temporal position. These results suggest that spatial information and temporal order information rely on separate encoding processes.

The role of peripheral vision in implicit contextual cuing

Implicit contextual cuing refers to the ability to learn the association between contextual information of our environment and a specific target, which can be used to guide attention during visual search. It was recently suggested that the storage of a snapshot image of the local context of a target underlies implicit contextual cuing. To make such a snapshot, it is necessary to use peripheral vision. In order to test whether peripheral vision can underlie implicit contextual cuing, we used a covert visual search task, in which participants were required to indicate the orientation of a target stimulus while foveating a fixation cross. The response times were shorter when the configuration of the stimuli was repeated than when the configuration was new. Importantly, this effect was still found after 10 days, indicating that peripherally perceived spatial context information can be stored in memory for long periods of time. These results indicate that peripheral vision can be used to make a snapshot of the local context of a target.

Scanning Patterns of Faces do not Explain Impaired Emotion Recognition in Huntington Disease: Evidence for a High Level Mechanism

In the current study, we aimed to investigate the emotion recognition impairment in Huntington’s disease (HD) patients and define whether this deficit is caused by impaired scanning patterns of the face. To achieve this goal, we recorded eye movements during a two-alternative forced-choice emotion recognition task. HD patients in pre-symptomatic (n = 16) and symptomatic (n = 9) disease stages were tested and their performance was compared to a control group (n = 22). In our emotion recognition task, participants had to indicate whether a face reflected one of six basic emotions. In addition, and in order to define whether emotion recognition was altered when the participants were forced to look at a specific component of the face, we used a second task where only limited facial information was provided (eyes/mouth in partially masked faces). Behavioral results showed no differences in the ability to recognize emotions between pre-symptomatic gene carriers and controls. However, an emotion recognition deficit was found for all six basic emotion categories in early stage HD. Analysis of eye movement patterns showed that patient and controls used similar scanning strategies. Patterns of deficits were similar regardless of whether parts of the faces were masked or not, thereby confirming that selective attention to particular face parts is not underlying the deficits. These results suggest that the emotion recognition deficits in symptomatic HD patients cannot be explained by impaired scanning patterns of faces. Furthermore, no selective deficit for recognition of disgust was found in pre-symptomatic HD patients.

Object-Location Memory: A Lesion-Behavior Mapping Study in Stroke Patients.

Object-location memory is an important form of spatial memory, comprising different subcomponents that each process specific types of information within memory, i.e. remembering objects, remembering positions and binding these features in memory. In the current study we investigated the neural correlates of binding categorical (relative) or coordinate (exact) position information with objects in memory. Therefore, an object-location memory battery was used, including different task conditions assessing object-location memory, i.e. memory for position information per se, and binding object information with coordinate and categorical position information. Sixty-one stroke patients with focal brain lesions were examined and compared with 77 healthy matched controls. The lesion subtraction method was used to define the area of overlap. Results indicate an important role of the left posterior parietal cortex in the binding of both categorical and coordinate positions with object information. Additionally, the hippocampus seems important for categorical object-location memory. This suggests that categorical and coordinate object-location memory depend on similar cognitive and neural systems.

Object based implicit contextual learning: a study of eye movements

Implicit contextual cueing refers to a top-down mechanism in which visual search is facilitated by learned contextual features. In the current study we aimed to investigate the mechanism underlying implicit contextual learning using object information as a contextual cue. Therefore, we measured eye movements during an object-based contextual cueing task. We demonstrated that visual search is facilitated by repeated object information and that this reduction in response times is associated with shorter fixation durations. This indicates that by memorizing associations between objects in our environment we can recognize objects faster, thereby facilitating visual search.