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PubMed1994

Tonic accommodation: a review. II. Accommodative adaptation and clinical aspects.

Part I of this review considered basic aspects of tonic accommodation (TA), i.e. the accommodative response observed under degraded stimulus conditions. Part II considers accommodative adaptation, i.e. the apparent change in TA following periods of sustained fixation, and clinical aspects of both baseline TA and accommodative adaptation. It is suggested that the apparent post-task shift in TA reflects the slow rate of decay of the stimulus-mediated adaptive accommodative response, while the actual level of tonic innervation to the ciliary muscle remains relatively constant. The clinical implications of both TA and accommodative adaptation are discussed with regard to night, space and instrument myopia and refractive error development, notably nearwork-induced myopia. It is concluded that the evidence for any association between this form of myopia and either TA or accommodative adaptation is equivocal, and furthermore it seems likely that TA plays only a minor role in influencing the closed-loop steady-state accommodative response.

Accommodation, Ocular↗
PubMed2005

Change in sensory functioning predicts change in cognitive functioning: results from a 6-year follow-up in the maastricht aging study.

OBJECTIVES: To examine the longitudinal relationship between sensory functioning and a broad range of cognitive functions after 6 years follow-up and whether cataract surgery or first-time hearing aid use affected cognition. DESIGN: Hierarchical regression procedures were employed to determine whether sensory functioning was predictive of cognitive performance. SETTING: Maastricht University and the University Hospital Maastricht, the Netherlands. PARTICIPANTS: Older Dutch adults (>/=55) enrolled in the Maastricht Aging Study (N=418). MEASUREMENTS: Visual and auditory acuity, the Visual Verbal Learning Test (VVLT), the Stroop Color Word Test (SCWT), the Concept Shifting Task (CST), the Verbal Fluency Test, and the Letter-Digit Substitution Test (LDST). RESULTS: A change in visual acuity was associated with change in most cognitive measures, including the total and recall scores of the VVLT, the mean score of the first two SCWT cards, the mean score of the first two CST cards and the LDST. In addition, a change in auditory acuity predicted change in memory performance (VVLT total and recall scores), and auditory acuity measured at baseline predicted change in the mean score of the first two SCWT cards and the LDST. CONCLUSION: The findings support the notion of a strong connection between sensory acuity in auditory and visual domains and cognitive performance measures, both from a cross-sectional and a longitudinal perspective. They also suggest that it is essential to screen older individuals in a clinical context for sensory functioning so that changes in visual or auditory acuity are not interpreted as changes in cognitive performance.

Adult↗
PubMed1978

A feminist approach to family therapy.

Although family therapy recognizes the importance of the social context as a determiner of behavior, family therapists have not examined the consequences of traditional socialization practices that primarily disadvantage women. The unquestioned reinforcement of stereotyped sex roles takes place in much of family therapy. A feminist therapy orientation that considers the consequences of stereotyped sex roles and the statuses prescribed by society for females and males should be part of family therapy practice. This paper describes the ways in which family therapists who are aware of their own biases and those of the family can change sexist patterns through applying feminist principles to such areas as the contract, shifting tasks in the family, communication, generational boundaries, relabeling deviance, modeling, and therapeutic alliances.

Communication↗
PubMed2004

Relationship between balance and gait stability in healthy older adults.

Age-related adaptations during walking create a more stable walking pattern, which is less effective for forward progression and might be related to balance deficiencies. This study determined the relationship between walking stability and measures of balance in older adults. Seventeen older and 20 young adults performed the Berg Balance Test (BBT) and walked 10 m. Walking velocity (WV) and cadence were measured, and a gait-stability ratio (GSR) was calculated. Higher GSR indicated that a greater portion of the gait cycle was spent in double-limb support. Age-group comparisons established declines in BBT scores and WV and increases in GSR with age. Significant relationships were identified for BBT Item 12 (alternate stepping on a stool) with WV (r =.58, r(2) =.34) and GSR (r = -.74, r(2) =.54). The correlation of BBT Item 12 with GSR was stronger than with WV (p <.05). Results indicated a strong relationship between increased gait stability and decreased balance for a dynamic weight-shifting task. Therefore, GSR is a better indicator of balance deficits during walking than is WV alone.

Accidental Falls↗
PubMed2004

Analysis and design of behavioral experiments to characterize population learning.

In population learning studies, between-subject response differences are an important source of variance that must be characterized to identify accurately the features of the learning process common to the population. Although learning is a dynamic process, current population analyses do not use dynamic estimation methods, do not compute both population and individual learning curves, and use learning criteria that are less than optimal. We develop a state-space random effects (SSRE) model to estimate population and individual learning curves, ideal observer curves, and learning trials, and to make dynamic assessments of learning between two populations and within the same population that avoid multiple hypothesis tests. In an 80-trial study of an NMDA antagonist's effect on the ability of rats to execute a set-shift task, our dynamic assessments of learning demonstrated that both the treatment and control groups learned, yet, by trial 35, the treatment group learning was significantly impaired relative to control. We used our SSRE model in a theoretical study to evaluate the design efficiency of learning experiments in terms of the number of animals per group and number of trials per animal required to characterize learning differences between two populations. Our results demonstrated that a maximum difference in the probability of a correct response between the treatment and control group learning curves of 0.07 (0.20) would require 15 to 20 (5 to 7) animals per group in an 80 (60)-trial experiment. The SSRE model offers a practical approach to dynamic analysis of population learning and a theoretical framework for optimal design of learning experiments.

Algorithms↗
PubMed2006

Multiple cognitive deficits in amnestic mild cognitive impairment.

OBJECTIVE: To determine if more widespread cognitive deficits are present in a narrowly defined group of patients with the amnestic form of mild cognitive impairment (MCI). METHODS: From a larger sample of patients clinically diagnosed as meeting the criteria of Petersen et al. for amnestic MCI, we selected 22 subjects who had Clinical Dementia Rating scores of zero on all domains besides memory and orientation. These MCI subjects with presumably isolated memory impairments were compared to 35 age-matched normal controls and 33 very mild Alzheimer's disease (AD) patients on a battery of neuropsychological tests. RESULT: In addition to the expected deficits in episodic memory, the amnestic MCI group performed less well than the controls but better than the AD group on design fluency, category fluency, a set shifting task and the Stroop interference condition. Over half the amnestic MCI group (vs. none of the normal controls) scored at least 1 standard deviation below control means on 4 or more of the nonmemory cognitive tasks. CONCLUSIONS: Isolated memory impairment may be fairly uncommon in clinically diagnosed amnestic MCI patients, even when the criteria for amnestic MCI are fairly narrow. Additional cognitive impairments are likely to include fluency and executive functioning. These more diffuse deficits argue for comprehensive cognitive assessments, even when the patient and family are reporting only memory decline, and are consistent with the increase in attention paid to the heterogeneity of MCI.

Aged↗
PubMed1989

Bradykinesia in Parkinson's disease: disorders of onset and execution of fast movement.

Simple reaction time lengthens in parkinsonian patients as the severity of motor disorder progresses. Shortening of reaction time was obtained by giving a warning signal to a greater extent in cases with severer motor disability. The results suggest that inattention, one of several symptoms common to lesions in the frontal lobe and Parkinson's disease, may be a factor in bradykinesia in purposive movements in the disease. The Wisconsin card sorting test and criterion shift task which we devised to deal with a single patients have difficulty in dealing with multiple sets simultaneously, which may be caused also by inattention. In execution of ballistic movement in parkinsonian patients, only a small torque constant in amount and in time can be produced in the beginning, irrespective of the size of force required, and subsequently enough force is built up to reach the target. This was more marked in cases with severe motor disability and in cases with decrease in power. Rigidity, mechanical properties of the limb or disorders in ocular movement were not responsible for the production of the initial small torque. Oculo-manual incoordination in visuomotor tracking tasks is also discussed.

Adult↗
PubMed2000

West London first-episode study of schizophrenia. Clinical correlates of duration of untreated psychosis.

BACKGROUND: Studies in schizophrenia suggest that a longer initial period of untreated illness is associated with a poorer clinical outcome. AIMS: To determine whether, in first-episode schizophrenia, a longer duration of untreated psychosis (DUP) or of untreated illness (DUI) (DUP plus any prodrome) is associated with clinical variables that could mediate a poor prognosis. METHOD: Clinical, social, neuropsychological and oculomotor function data on 53 patients with first-episode schizophrenia were related to the DUP and DUI. RESULTS: Comparing short and long DUP groups split around the median showed no statistically significant differences (except age); patients in the latter group tended to perform worse on an executive attentional set-shifting task, and were more likely to be unemployed, and living alone or homeless. CONCLUSIONS: There was little evidence of any association between either DUP or DUI and progressive deterioration in the schizophrenic illness or the development of resistance to initial drug treatment. Social variables that augur a poor prognosis may be associated with delayed presentation of schizophrenia to psychiatric services.

Adult↗
PubMed2001

Cognitive deficits in depression: possible implications for functional neuropathology.

BACKGROUND: While depression is known to involve a disturbance of mood, movement and cognition, its associated cognitive deficits are frequently viewed as simple epiphenomena of the disorder. AIMS: To review the status of cognitive deficits in depression and their putative neurobiological underpinnings. METHOD: Selective computerised review of the literature examining cognitive deficits in depression and their brain correlates. RESULTS: Recent studies report both mnemonic deficits and the presence of executive impairment--possibly selective for set-shifting tasks--in depression. Many studies suggest that these occur independent of age, depression severity and subtype, task 'difficulty', motivation and response bias: some persist upon clinical 'recovery'. CONCLUSIONS: Mnemonic and executive deficits do no appear to be epiphenomena of depressive disorder. A focus on the interactions between motivation, affect and cognitive function may allow greater understanding of the interplay between key aspects of the dorsal and ventral aspects of the prefrontal cortex in depression.

Aging↗
PubMed2004

Adolescent development of forebrain stimulant responsiveness: insights from animal studies.

Although initiation of drug abuse occurs primarily during adolescence, little is known about the central effects of nicotine and other abused drugs during this developmental period. Here evidence, derived from studies in rodents, is presented that suggests that tobacco use initiation during early adolescence results from a higher reward value of nicotine. The developmental profiles of the rewarding effects of other abused drugs, such as cocaine, differ from that of nicotine. Using in situ hybridization to quantify mRNA levels of the immediate early gene, cfos, the neuronal activating effects of nicotine in limbic and sensory cortices at different developmental stages are evaluated. Significant age changes in basal levels of cfos mRNA expression in cortical regions are observed, with a peak of responding of limbic cortices during early adolescence. A changing pattern of nicotine-induced neuronal activation is seen across the developmental spectrum, with unique differences in both limbic and sensory cortex responding during adolescence. An attentional set-shifting task was also used to evaluate whether the observed differences during adolescence reflect early functional immaturity of prefrontal cortices that regulate motivated behavior and psychostimulant responding. The finding of significantly better responding during adolescence suggests apparent functional maturity of prefrontal circuits and greater cognitive flexibility at younger ages. These findings in rodent models suggest that adolescence is a period of altered sensitivity to environmental stimuli, including abused drugs. Further efforts are required to overcome technical challenges in order to evaluate drug effects systematically in this age group.

Adolescent↗
PubMed1999

Insulin-like growth factor-I and cognitive function in healthy older men.

The GH/insulin-like growth factor-I (GH/IGF-I) axis is known to be involved in aging of physiological functions. Recent studies indicate that the GH/IGF-I axis may be associated with cognitive functioning. The aim of the present study was to determine whether the age-related decline in circulating levels of IGF-I, as an index of anabolic status, is associated with cognitive functions that are known to decline with aging, but not with cognitive functions not sensitive to aging. Twenty five healthy older men with well-preserved functional ability participated in the study. We also administered neuropsychological tests of general knowledge, vocabulary, basic visual perception, reading ability, visuoconstructive ability, perceptual-motor speed, mental tracking, and verbal long-term memory. Performance on the last four tests decline with aging, whereas the first four of these tests have been shown not to be sensitive to cognitive aging. Mean age of the subjects was 69.1 +/- 3.4 (SD) yr (range 65-76 yr), their mean body mass index was 27.0 +/- 2.4 kg/m2, and their mean IGF-I level was 122 ng/mL (range: 50-220). We found IGF-I levels to be significantly associated with the performances (controlled for education) on the Digit Symbol Substitution test (r = 0.52, P = 0.009) and the Concept Shifting Task (r = -0.55, P = 0.005), which measure perceptual-motor and mental processing speed. Subjects with higher IGF-I levels performed better on these tests, performance on which is known to decline with aging. In conclusion, the results of this study support the hypothesis that circulating IGF-I may play a role in the age-related reduction of certain cognitive functions, specifically speed of information processing.

Aged↗
PubMed2003

"Spatial memory in Long Evans and Rattus Norvegicus rats".

Rodents in search of food use visual environmental signals and complex spatial strategies and do not return to previously-visited locations, known as the win-shift strategy. The solution to the Olton Octagonal Maze (OOM) involves Working Memory (WM). A modified OOM was used that allows for measuring WM and Long Term Memory (LTM). The delayed spatial win-shift task consisted of a Training and Test phase separated by a delay. Prior to the Training phase, four arms were chosen at random and blocked, and food pellets were placed in the food cups of the four remaining open arms. Each rat was allowed to retrieve the pellets from the four open arms and then return to its home cage for the delay period (either 5 or 20 min). In the Test phase all 8 lanes were open, and the bait was placed in those blocked in the previous phase. Two experimental groups of rats, Long Evans and Norvegicus, and their corresponding control groups were trained. The experimental subjects performed Training-Delay-Test. The controls were only trained in the Test phase. Revisiting an arm previously explored in the 1st Phase was considered a LTM error. Revisiting an arm in the same trial constituted a WM error. It was concluded that the experimental groups do in fact possess LTM, with differences in favor of Norvegicus. There was no difference with respect to WM errors. The Norvegicus control group changes its strategy from allocentric to egocentric, which did not occur in the Long Evans control group.

Animals↗
PubMed1995

A spatial oculomotor memory-task performance produces a task-related slow shift in human electroencephalography.

Electroencephalographic (EEG) deflections in humans related to the performance of memory-guided saccades were studied in this work. The EEG deflections were recorded during 2 spatial oculomotor delayed response tasks in which the subject was instructed to make a saccade either to the right or to the left depending on the spatial location of the cue which had been shown in the beginning of the delay period. The EEG deflections were compared to those recorded during a control task in which the subject also made a saccade to the right or to the left after a delay but the requirement to keep spatial information actively in mind was minimized. A slow delay-related shift was recorded during all task conditions. The slow shift was positive in the most frontal and negative in the more posterior recording sites. The negative slow shift in the more posterior recording sites was larger in the memory tasks than in the control task. Since the memory and the control tasks differed mainly in their requirement to hold spatial information in mind it is suggested that the difference in the magnitude of slow shifts between the memory and the control tasks reflects neural activity related to spatial working memory. But although the oculomotor responses in all tasks were similar, the preparatory activities for the impending eye movements may not have been similar and in addition to working memory may have contributed to the observed differences in the slow shifts.

Adult↗
PubMed2001

Using segmented linear regression models with unknown change points to analyze strategy shifts in cognitive tasks.

Some years ago, Beem (1993, 1995) described a program for fitting two regression lines with an unknown change point (Segcurve). He suggested that such models are useful for the analysis of a variety of phenomena and gave an example of an application to the study of strategy shifts in a mental rotation task. This technique has also proven to be very fruitful for investigating strategy use and strategy shifts in other cognitive tasks. Recently, Beem (1999) developed SegcurvN, which fits n regression lines with (n - 1) unknown change points. In the present article we present this new technique and demonstrate the usefulness of a three-phase segmented linear regression model for the identification of strategies and strategy shifts in cognitive tasks by applying it to data from a numerosity judgment experiment. The advantages and shortcomings of this technique are evaluated.

Attention↗
PubMed2004

Effects of changing reward on performance of the delayed spatial win-shift radial maze task in pedunculopontine tegmental nucleus lesioned rats.

Because it was designed to assess working memory, the delayed spatial win-shift (DSWS) radial maze task has been used to investigate the involvement of corticostriatal structures in executive processing. Excitotoxic lesions of the pedunculopontine tegmental nucleus (PPTg) produce profound deficits in performance of this task that are not accounted for by motor impairment. Thus, PPTg DSWS deficits are hypothesized to support a role for PPTg in complex cognitive processing. However, other studies indicate that the behaviour of PPTg lesioned rats varies depending on level of motivational excitement, assessed by the presence or absence of deprivation, or by manipulations of reward value. Since DSWS performance may also be affected by motivational dysfunction, the present experiment was conducted to examine the effects of post-surgical presentation of a more positive food reward (chocolate drops) on the DSWS retention performance of PPTg lesioned rats. Results confirmed a PPTg lesion deficit: lesioned rats made significantly more errors in both training and test phases, and made errors significantly earlier in their choice sequence in the test phase. Main effects of phase on number of errors indicated that the PPTg test phase deficit was not simply the result of a carry-over impairment from the training phase. PPTg rats receiving chocolate made significantly fewer errors than PPTg rats receiving food pellets. Results suggest that PPTg DSWS deficits are not the result of altered motivation or hedonic appreciation of reward value (or reward change) and therefore support the hypothesis of executive cognitive deficits in PPTg lesioned rats.

Animals↗
PubMed2006

Neural networks of response shifting: influence of task speed and stimulus material.

Functional magnetic resonance imaging (fMRI) was used in 14 healthy subjects to measure brain activation, while response shifting was performed. In the activation phase, subjects were asked to shift their attention between two different types of visually presented stimuli. In the baseline phase, subjects were required to attend to one stimulus type only. Subjects responded by pressing a left or right key according to the side of presentation of the target stimuli. In a verbal task, subjects were required to switch between letters and numbers. In a figural task, subjects reacted to round and square shapes. Stimuli were presented for 750 or 1500 ms. Response shifting revealed significantly increased activation compared to non-switching in the bilateral superior parietal cortex, right occipital cortex, left inferior frontal cortex, left and right striatum, and bilateral dorsolateral prefrontal cortex (DLPFC). Superior parietal and occipital cortex activation may be due to spatial analysis during response shifting. Subvocal rehearsal of the task instructions may have led to activation in the left inferior frontal cortex. Activation in the striatum was related to prefrontal activation and may represent the association between basal ganglia and prefrontal activation during executive control. However, the most important brain region involved in the execution of response shifting was the bilateral DLPFC. Higher task speed increased executive top-down attentional control and, therefore, significantly increased activity in the bilateral DLPFC. Brain activation did not differ significantly between verbal and figural stimulus material. This result suggests that brain activation in the present study illustrates the brain regions involved in the basic cognitive mechanisms of response shifting.

Adult↗
PubMed1980

Evolution of negative and positive SP shifts in cats learning RT tasks.

Cortical slow potential (SP) shifts were recorded in freely moving cats while they learned reaction time tasks differing in the duration of the inter-stimulus interval (ISI). ISI durations were either 6 or 4 sec in experiment I; in experiment II, a reaction time paradigm with a 1 sec ISI was compared to a time estimation task. SP shifts of opposite polarity development throughout the experiments. It seems that: (1) positive SP shifts reflect motor processes and mechanisms of proprioceptive feedback related to the cat's preparatory movements for pressing the lever; (2) negative-going shifts peaking at the end of the ISI reflect temporal information processing related to ISI duration. Analogies with potentials found in man and animals in similar paradigms are discussed.

Animals↗
PubMed2004

Preparation for a forthcoming task is sufficient to produce subsequent shift costs.

Shifting from one task to another is associated with significant costs. Recently, it has been questioned whether the mere preparation for a forthcoming task, without the task's actually being executed, is sufficient to establish a new task set that results in shift costs when the execution of a task other than the prepared task is required. In a go/no-go study, it is shown that the mere preparation for a task is sufficient to produce shift costs, but only under conditions that encourage participants to engage in advance preparation for a precued task despite the possibility that the execution of this task will not always be required, because of occasional no-go trials. In addition, considerable reductions of shift costs after go trials could be observed under these conditions. When such a motivating context was not provided, only negligible shift costs were observed after a no-go trial, indicating that no task-set configuration had taken place without the need to perform the task. Furthermore, under these conditions, prolonging the preparation interval resulted in reaction time benefits that were similar for task shifts and repetitions, again indicating that no active task-set configuration took place.

Adult↗