Evidence for spatial navigational impairments in hydrocephalus patients without spina bifida

The cognitive sequelae of hydrocephalus have mostly been explored with standardised clinical tasks. The aim of the present research was determine whether impairments on these abstract tasks extend to everyday spatial and navigational behaviour. Patients with hydrocephalus, but without spina bifida, were compared to a control group on tests of searching behaviour, landmark memory, route learning, and path integration. Participants with hydrocephalus displayed reduced sensitivity to spatial cueing, less accurate route-learning, and significantly less accurate spatial updating. These data represent an important empirical demonstration of spatial navigational impairments due to hydrocephalus outside of the context of spina bifida. We discuss some of the cognitive, neural, and individual differences factors that might contribute to this particular pattern of impairments.     

Spatial and object working memory impairments in schizophrenia patients: a Bayesian item-response theory analysis

This study reports evidence that schizophrenia patients are significantly impaired in both spatial and object (shape) working memory. A 3-s delay between exposure and recall of targets was used and Bayesian item-response theory was applied to compensate for the tasks' differential difficulty while simultaneously taking account of missing data from participant attrition. Weaker evidence was found that in schizophrenia both domains are equally impaired on average, that spatial and object working memory appear to be more highly correlated with each other in the schizophrenia population than in the normal population, and that schizophrenia patients show greater variability in spatial than object working memory performance.     

Developmental coordination impairments in adulthood

The aim of this study was to extend the understanding of Developmental Coordination Disorder (DCD) into adulthood. We recruited 19 adults aged between 18 and 65 who had received diagnoses of DCD or dyspraxia or who self-reported as having motor impairments consistent with a history of DCD, together with age- and gender-matched controls. Participants were given tests of manual dexterity, handwriting, construction, obstacle avoidance, dynamic balance, static balance, dual task performance, ball skills, reaction time, movement time and sequencing. As a group, adults with DCD performed more poorly than controls across all tasks. Slowness and variability of movement was a pervasive feature of their performance and many individuals had considerable problems with sequencing and with dual task performance. A discriminant function analysis conducted using six performance measures correctly classified participants as car drivers or non-drivers. Adults do retain motor difficulties and these can exclude them from important activities of daily living.     

Visual field dependence as a navigational strategy

Visual perception is an important component of environmental navigation. Previous research has revealed large individual differences in navigational strategies (i.e., the body’s kinesthetic and embodied approach to movement) and the perception of environmental surfaces (via distance estimations), but little research has investigated the potential relationship between these sources of individual variation. An important navigational strategy is the interaction between reliance on visual cues and vestibular or proprioceptive cues. We investigated the role of this navigational strategy in the perception of environmental surfaces. The results supported three embodied evolutionary predictions: Individuals who were most reliant on visual context (1) overestimated vertical surfaces significantly more, and (2) feared falling significantly more, than did those who were least reliant on visual context; and (3) all individuals had roughly accurate horizontal distance estimates, regardless of their navigational strategy. These are among the first data to suggest that individual differences in perception are closely related to the individual differences in navigation that derive from navigational risks. Variable navigational strategies may reflect variable capacities to perceive and navigate the environment.     

Ideational action impairments in Alzheimer's disease

We report data from a group of patients with mild Alzheimer's disease on a range of tasks requiring either stored semantic knowledge about objects (e.g., naming object use) or the execution of action to objects (e.g., miming and using objects). We found that the patients were impaired at miming in response to objects, even when they could describe the object's function. On the other hand, copying gestures was not impaired relative to naming gestures, indicating that an ideomotor deficit in action execution, per se, was unlikely to explain the impairments in object use. We suggest instead that the patients had an impairment in stored motor programmes for action, over and above their deficits in semantic knowledge. Despite this, the patients were better at using than at miming to objects, consistent with the view that proprioceptive input (when using objects) can directly constrain selection of the appropriate motor programme for action.     

Persistent and stable biases in spatial learning mechanisms predict navigational style

A wealth of evidence in rodents and humans supports the central roles of two learning systems—hippocampal place learning and striatal response learning—in the formation of spatial representations to support navigation. Individual differences in the ways that these mechanisms are engaged during initial encoding and subsequent navigation may provide a powerful framework for explaining the wide range of variability found in the strategies and solutions that make up human navigational styles. Previous work has revealed that activation in the hippocampal and striatal networks during learning could predict navigational style. Here, we used functional magnetic resonance imaging to investigate the relative activations in these systems during both initial encoding and the act of dynamic navigation in a learned environment. Participants learned a virtual environment and were tested on subsequent navigation to targets within the environment. We observed that a given individual had a consistent balance of memory system engagement across both initial encoding and subsequent navigation, a balance that successfully predicted the participants’ tendencies to use novel shortcuts versus familiar paths during dynamic navigation. This was further supported by the observation that the activation during subsequent retrieval was not dependent on the type of solution used on a given trial. Taken together, our results suggest a model in which the place- and response-learning systems are present in parallel to support a variety of navigational behaviors, but stable biases in the engagement of these systems influence what solutions might be available for any given individual.     

Decision-making impairments in patients with Parkinson's disease

A high percentage of Parkinson's disease (PD) patients show cognitive impairments in addition to the cardinal motor symptoms. These deficits primarily concern executive functions most probably linked to dysfunctions in prefrontal regions due to decreased dopaminergic transmission in fronto-striatal loops. To investigate possible associations between decision-making and executive functions in PD, we examined 20 non-demented PD patients and 20 healthy control subjects with a neuropsychological test battery and the Game of Dice Task. In this computerised decision-making task, the rules for gains and losses and the winning probabilities are obvious and stable. Thus, strategic components besides feedback processing might influence decision-making in this task. We found that PD patients were impaired in the Game of Dice task performance and that the frequency of disadvantageous choices correlated with both executive functions and feedback processing. We suggest that decision-making deficits of PD patients in explicit gambling situations might be associated with dysfunctions in two different fronto-striatal loops: the limbic-orbitofrontal-striatal loop, involved in feedback processing, and the dorsolateral prefrontal-striatal loop, involved in executive functions.     

Emotion-induced impairments in speeded word recognition tasks

Recent studies show that emotional stimuli impair the identification of subsequently presented, briefly flashed stimuli. In the present study, we investigated whether emotional distractors (primes) impaired target processing when presentation of the target stimulus was not impoverished. In lexical decision, animacy decision, rhyme decision, and nonword naming, targets were presented in such a manner that they were clearly visible (i.e., targets were not masked and presented until participants responded). In all tasks taboo-sexual distractors caused a slowdown in responding to the subsequent neutral target. Our results indicate that the detrimental effects of emotional distractors are not confined to paradigms in which visibility of the target is limited. Moreover, impairments were obtained even when semantic processing of stimuli was not required.     

Inferences about age impairments in inferential reasoning

Two experiments are reported in which specially constructed series completion tests were administered to samples of young and older adults to determine why increased age is associated with poorer performance on measures of inductive reasoning. The results indicated that young and older adults did not differ significantly in the effectiveness of processes concerned with determining simple relations, but that older adults were impaired when the relations are complex or when different problems involve alternative organizational patterns. We conclude that the poorer performance of older adults relative to young adults on tasks of this type may be due to inadequate (e.g., overly simplistic or temporally instable) relational structures for the integration of problem elements.     

Pharmacotherapy of posttraumatic cognitive impairments

Pharmacotherapy may contribute to the rehabilitation of persons with posttraumatic cognitive impairments. This article reviews first the neurobiological consequences of traumatic brain injury with a particular emphasis on acute and long-term posttraumatic neurochemical disturbances. Studies of pharmacotherapies for posttraumatic cognitive impairments are reviewed next, and are organized according to medication class and the neurotransmitter system they affect most. Based on the evidence provided by that review, augmentation of posttraumatic cerebral catecholaminergic and cholinergic function are suggested as potentially useful neurochemical targets for pharmacologic intervention in this population. More specifically, it is suggested that persons with posttraumatic impairments in arousal, speed of processing, and possibly attention may benefit most from treatment with an agent that augments cerebral catecholaminergic function, and that persons whose predominant posttraumatic impairment is in the domain of memory may benefit most from treatment with cholinesterase inhibitors. Practical considerations regarding the use of pharmacotherapies for posttraumatic cognitive impairments are offered, and the need for additional research in this area is highlighted.     

The relation between horizontality and rod-and-frame and vestibular navigational performance

Sex differences on Piaget's water-level (horizontality) test are well established but poorly understood. In this article, correlates of female horizontality performance are systematically explored. Across the five experiments reported, it was found that female subjects who failed the water-level test (poor-horizontality female subjects) were selectively impaired on tasks that required processing information from the otolith organs. In Experiment 1, poor-horizontality female subjects were found to be impaired relative to good-horizontality subjects on the rod-and-frame test. In Experiment 2, a relation was found between female horizontality performance and the ability to process vestibular information in a passive transport task. Experiment 3 ruled out poor spatial updating as a mediating factor in this relation. The results of Experiments 4 and 5 indicated that poor-horizontality female subjects perform randomly on vestibular navigation because they cannot judge linear displacement under conditions of passive transport. The linear transport task is similar to the rod-and-frame task in that both require the central processing of otolith signals. It is proposed that one way to solve the water-level test is to imagine, on the basis of prior perceptual experiences, what the water level looks like inside tilted containers. Because of complex visual-otolith interactions, poor-horizontality female subjects may experience these events differently than good-horizontality subjects.     

Route selection by rats and humans in a navigational traveling salesman problem

Spatial cognition is typically examined in non-human animals from the perspective of learning and memory. For this reason, spatial tasks are often constrained by the time necessary for training or the capacity of the animal’s short-term memory. A spatial task with limited learning and memory demands could allow for more efficient study of some aspects of spatial cognition. The traveling salesman problem (TSP), used to study human visuospatial problem solving, is a simple task with modifiable learning and memory requirements. In the current study, humans and rats were characterized in a navigational version of the TSP. Subjects visited each of 10 baited targets in any sequence from a set starting location. Unlike similar experiments, the roles of learning and memory were purposely minimized; all targets were perceptually available, no distracters were used, and each configuration was tested only once. The task yielded a variety of behavioral measures, including target revisits and omissions, route length, and frequency of transitions between each pair of targets. Both humans and rats consistently chose routes that were more efficient than chance, but less efficient than optimal, and generally less efficient than routes produced by the nearest-neighbor strategy. We conclude that the TSP is a useful and flexible task for the study of spatial cognition in human and non-human animals.     

Specific phonological impairments in dyslexia revealed by eyetracking

Phonological deficits in dyslexia are typically assessed using metalinguistic tasks vulnerable to extraneous factors such as attention and memory. The present work takes the novel approach of measuring phonology using eyetracking. Eye movements of dyslexic children were monitored during an auditory word recognition task in which target items in a display (e.g., candle) were accompanied by distractors sharing a cohort (candy) or rhyme (sandal). Like controls, dyslexics showed slower recognition times when a cohort distractor was present than in a baseline condition with only phonologically unrelated distractors. However, unlike controls, dyslexic children did not show slowed recognition of targets with a rhyme distractor, suggesting they had not encoded rhyme relationships. This was further explored in an overt phonological awareness test of cohort and rhyme. Surprisingly, dyslexics showed normal rhyme performance but poorer judgment of initial sounds on these overt tests. The results implicate impaired knowledge of rhyme information in dyslexia; however they also indicate that testing methodology plays a critical role in how such problems are identified.     

Working memory impairments in schizophrenia: a meta-analysis

Working memory (WM) deficit is a cardinal cognitive symptom of schizophrenia, but the differences among the tasks and measures used to assess WM make it difficult to compare across studies. The authors conducted a meta-analytic review to address 3 major questions: (a) Do patients with schizophrenia show WM deficits across diverse methodology; (b) Is WM deficit supramodal; and (c) Does the WM deficit worsen with longer delays? The results indicate that significant WM deficit was present in schizophrenia patients in all modalities examined. Increasing delay beyond 1 s did not influence the performance difference between schizophrenia patients and healthy control participants in WM. These results suggest that WM deficit in schizophrenia is modality independent and that encoding and/or early part of maintenance may be problematic.     

Linguistic humor comprehension in children with articulation impairments

This study investigated the ability of children with articulation disorders to comprehend linguistic humor. It was hypothesized that children with articulation disorders would have more difficulty understanding humor based on phonological differences than humor based on lexical differences. A second hypothesis predicted that children with articulation disorders would have more difficulty understanding riddles in which the phoneme they misarticulated, either /s/ or /r/, was the source of ambiguity than riddles in which the source of ambiguity did not involve the phoneme they misarticulated. Results did not confirm the first hypothesis as there were no statistically significant differences between groups with regard to the children's ability to understand phonological vs lexical humor. The second hypothesis was supported. Children had significantly more difficulty understanding riddles in which the source of ambiguity related to the phoneme they misarticulated, either /s/ or /r/ than they did understanding phonological humor involving nonerror phonemes.