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PubMed1989

Effect of starting position on reproduction of movement: further evidence of interference between location and distance information.

Two experiments done with a short-term memory paradigm examined the influence of shifts in the starting position on the reproduction of kinesthetic location (Exp. 1) and on distance cues (Exp. 2). We assessed possible causes of the systematic pattern of undershooting and overshooting as related to the shift in the starting position. In each experiment, two groups of 10 students were given 25 trials, and each had criterion and reproduction tasks involving linear-positioning movements with a 10-sec. retention interval. Each experiment had two independent variables, the group of subjects and the shift in the starting position. The two groups differed in the possible sources of information, the distance moved (Exp. 1) or the end-location (Exp. 2), which were assumed to cause undershooting and overshooting during reproduction. Analysis showed that the information about the distance moved may produce undershooting and overshooting in reproduction of the end-location (Exp. 2). Also, the information about the end-location may produce undershooting and overshooting in reproduction of the distance moved (Exp. 2). The findings were further evidence of interference between location and distance cues in motor short-term memory.

Cues↗

PubMed1991

Attentional focussing and spatial stimulus-response compatibility.

The relative functional significance of attention shifts and attentional zooming for the coding of stimulus position in spatial compatibility tasks is demonstrated by proposing and testing experimentally a tentative explanation of the absence of a Simon effect in Experiment 3 of Umiltà and Liotti (1987). It is assumed that the neutral point of the spatial frame of reference for coding spatial position is at the position where attention is focussed immediately before exposition of the stimulus pattern. If a stimulus pattern is exposed to the right or the left of this position a spatial compatibility effect can be observed when the stimulus-response pairing is incompatible. Generalizing from this, one can say that a spatial compatibility effect will be observed if the last step in attentional focussing of the stimulus attribute specifying the response is a horizontal or a vertical attention shift. If the last step in focussing is attentional zooming (change in the representational level attended to), the stimulus pattern is localized at the horizontal and the vertical positions where the last attention shift had positioned the focus. In this case the spatial code is neutral on these dimensions and so no spatial compatibility effect should result. To test this model we conducted two experiments. Experiment 1 replicated the finding of Umiltà and Liotti that there is no Simon effect in the condition with no delay between a positional cue (two small boxes on the left or right of a fixation cross) and the imperative stimulus, whereas in the condition with a delay of 500 ms a Simon effect was observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMedDate not supplied

Peripheral shift reduces visual sensitivity in cat geniculate neurones.

The sudden displacement of the retinal image during a saccade raises the visual threshold of human observers to foveal stimuli. The fall in visual sensitivity observed during this phenomenon, known as saccadic suppression, seems to occur very early in the visual processing chain. The lateral geniculate nucleus (LGN) is a likely locus for the multiple retinal and extraretinal interactions occurring during saccadic eye movements, therefore we used the responses of relay cells of adult cats to simulate a psychophysical experiment. We first measured the responses of X and Y relay cells (27 X and 13 Y) to central spots of optimal size and different contrasts. The spots were presented either alone or time locked with the rapid movement of a large, high-contrast peripheral pattern, referred to as shift. We measured the percentage of trials on which the relay cell fired more spikes when the spot (contrast: 0.03-1.0) was present than when it was absent. In experiments with human observers the task was to indicate, by a keypress, which of two otherwise identical temporal intervals contained the spot. The shift reduces the sensitivity (raises the contrast threshold) of neurones in the cat relay cells to brief, stationary targets presented to the receptive-field center. The suppression of visual sensitivity is significantly greater in Y cells than in X cells (average sensitivity ratios 5.6 +/- 5.4 in Y cells, 1.59 +/- 0.9 in X cells: P < 0.001, U test). The shift also reduces the sensitivity of human observers to the same target. This suggests that the LGN is a potential locus for the modulation of visual responses that leads to saccadic suppression.

Animals↗

PubMed1994

P300 asymmetries in schizophrenia revisited with reference-independent methods.

Evidence of hemispheric asymmetries in schizophrenia has been reported from different research areas. Asymmetries in evoked potential P300 topography are still controversial because of inconsistent findings. In the present study, previous results of abnormal lateralization of P300 were replicated in stabilized residual schizophrenic patients. Auditory P300 was recorded during an oddball task in which subjects detected rare target stimuli. Schizophrenic patients had the P300 peak shifted to the right hemisphere and differed significantly from age- and sex-matched normal control subjects who had left-lateralized P300 peaks. A comparison of different methods of assessment and analysis of the topographical features of the P300 electric fields showed that the extraction of reference-independent descriptors of P300 topography is a reliable and sensitive method for statistical handling of the maps. The results suggest left hemispheric dysfunction during cognitive tasks in a subgroup of schizophrenic patients. Inconsistencies between previous studies are likely to be due to heterogeneous patient groups, which may have included patients in an acute schizophrenic episode or patients in clinical remission. Investigation of the clinical meaning of P300 alterations requires careful psychopathological definition of the patient groups.

Adult↗

PubMed1980

Control of choice in conditional discriminations by sample-specific behaviors.

When sample-specific responding is occasioned by sample stimuli in matching and oddity tasks with pigeons, such responding controls the choices between comparison stimuli. This control was investigated in four experiments. In Experiments 1 and 2, differential responding to the samples in line-line matching and line-line oddity was reversed following acquisition of these problems. The reversal interfered with reacquisition of the same conditional discrimination but facilitated acquisition of the opposite discrimination. In Experiment 3, pigeons initially trained on line-line matching were shifted to hue-line matching. Positive transfer occurred when correct choices in both tasks were paired with the same sample-response patterns. Conversely, negative transfer occurred when correct choices were paired with opposite patterns. In Experiment 4, two concurrent conditional discriminations were designed so that sample-response patterns were paired with specific sample stimuli, but not with correct choices. Faster acquisition occurred when response patterns differed within rather than between sample dimensions. Furthermore, sample-specific responding controlled choices when the dimensional stimuli were difficult to discriminate but not when they were easy to discriminate. The combined results are interpreted in terms of overshadowing. Visual stimuli that control choice can be overshadowed by sample-specific responding if the latter facilitates conditional discrimination acquisition.

Animals↗

PubMed2004

Characteristic neurocognitive profile associated with adult attention-deficit/hyperactivity disorder.

BACKGROUND: It is now accepted that attention-deficit/hyperactivity disorder (ADHD) often persists into adulthood. However, relative to the considerable literature concerning the profile of neurocognitive deficits associated with this disorder in childhood, equivalent investigations in adult populations have been less common. The current study examined cognitive function in adults diagnosed with ADHD employing well-validated neuropsychological tasks. METHOD: Nineteen adult patients who satisfied DSM-IV criteria for ADHD and 19 matched (gender, age and verbal IQ), non-clinical control subjects were recruited. Patients were either unmedicated or had abstained from a psychostimulant medication regime for at least 24 h prior to neurocognitive assessment. A functionally wide-ranging test battery was administered. RESULTS: Relative to controls, ADHD adults performed significantly worse on spatial working memory, planning, and attentional-set shifting tests and were significantly slower to respond to target stimuli on the go/no-go task. In contrast, the two subject groups performed equivalently on decision-making and pattern/spatial recognition memory assessments. CONCLUSIONS: The demonstration of neuropsychological dysfunction in the adult ADHD cohort provides some support for the validity of this diagnosis in adulthood. In particular, there is broad consistency between the cognitive profile revealed in the current investigation and that previously demonstrated in a study of medication-naïve ADHD children. There is evidence that frontostriatal function is especially disrupted.

Adult↗

PubMed2005

Motor cortex neural correlates of output kinematics and kinetics during isometric-force and arm-reaching tasks.

We recorded the activity of 132 proximal-arm-related neurons in caudal primary motor cortex (M1) of two monkeys while they generated either isometric forces against a rigid handle or arm movements with a heavy movable handle, in the same eight directions in a horizontal plane. The isometric forces increased in monotonic fashion in the direction of the force target. The forces exerted against the handle in the movement task were more complex, including an initial accelerating force in the direction of movement followed by a transient decelerating force opposite to the direction of movement as the hand approached the target. EMG activity of proximal-arm muscles reflected the difference in task dynamics, showing directional ramplike activity changes in the isometric task and reciprocally tuned "triphasic" patterns in the movement task. The apparent instantaneous directionality of muscle activity, when expressed in hand-centered spatial coordinates, remained relatively stable during the isometric ramps but often showed a large transient shift during deceleration of the arm movements. Single-neuron and population-level activity in M1 showed similar task-dependent changes in temporal pattern and instantaneous directionality. The momentary dissociation of the directionality of neuronal discharge and movement kinematics during deceleration indicated that the activity of many arm-related M1 neurons is not coupled only to the direction and speed of hand motion. These results also demonstrate that population-level signals reflecting the dynamics of motor tasks and of interactions with objects in the environment are available in caudal M1. This task-dynamics signal could greatly enhance the performance capabilities of neuroprosthetic controllers.

Animals↗

PubMedDate not supplied

[Sleep disorders and day sleepiness in a population of shift workers of the State Police].

UNLABELLED: Policemen are workers exposed to risk from both shiftwork and delicate tasks. This study aims to investigate sleep habits, prevalence of sleep disturbance, sleepiness and hypnotic drug intake in the whole population of Italian State Policemen working in the Genoa district. Italian literature is completely lacking of such data. The study has been carried out by means self administered and assisted questionnaires. Eighty-five percent of the population accepted and answered the questionnaire. Here we focus on the differences between 540 not-shiftworkers, NS, (413 males, 127 females), and 575 shiftworkers, S, (483 males, 92 females). A higher prevalence of difficulties in falling asleep, sleep-latency longer than 20 min. and early awakenings was found in S. No significative differences in daytime sleepiness and drug intake were found between the two groups. Concerning the self-evaluation of the numbers of hours slept during the night and during the 24 hours a higher quantity of sleep was reported by S. CONCLUSIONS: Data seem to indicate a low quality of sleep in S without any evidence of increased daytime sleepiness or increased hypnotic drugs assumption. Shiftworkers seem to compensate their poor quality of sleep with a greater amount of time spent sleeping in the 24 hour period. Such a condition could be the expression of a prolonged recovery from the shift effects.

Adult↗

PubMed2004

Searching for stimulus-driven shifts of attention.

Several types of dynamic cues (e.g., abrupt onsets, motion) draw attention in visual search tasks even when they are irrelevant. Although these stimuli appear to capture attention in a stimulus-driven fashion, typical visual search tasks might induce an intentional strategy to focus on dynamic events. Because observers can only begin their search when the search display suddenly appears, they might orient to any dynamic display change (Folk, Remington, & Johnston, 1992; Gibson & Kelsey, 1998). If so, the appearance of capture might result from task-induced biases rather than from the properties of the stimulus. In fact, such biases can even create the appearance of stimulus-driven capture by stimuli that typically do not capture attention (Gibson & Kelsey, 1998). The possibility of task-induced, top-down biases plagues the interpretation of all previous studies claiming stimulus-driven attention capture by dynamic stimuli. In two experiments, we attempt to eliminate potential task-induced biases by removing any need to monitor for display changes. In the first experiment, search displays did not change on most trials. In the second experiment, although new search displays appeared on each trial, we ensured that observers never saw the changes, by making them during large saccades. In both cases, dynamic events still received search priority, suggesting that some dynamic stimuli capture attention in a stimulus-driven fashion.

Attention↗

PubMed1999

Short-term total sleep deprivations does not selectively impair higher cortical functioning.

Previous research has shown that total sleep deprivation produces impairment in sustained attention and vigilance especially if the deprivation period is greater than 48 hours. However little is known about the effects of sleep deprivation on performance of tasks considered to be measures of higher cortical functioning such as tests of cognitive flexibility and the capacity to shift from one response set to another. One current hypothesis is that sleep deprivation of a shorter duration (34-36 hours) adversely affects higher cortical function while effects on attention and vigilance tasks are relatively mild. Performance on an intelligence test, a test of sustained attention and tests designed to measure higher cortical function were compared in a group of 29 subjects who underwent 34-36 hours of continuous sleep deprivation and 32 normal sleeping control subjects. No significant group performance differences in the hypothesized direction were noted on any measure. One night of total sleep deprivation does not appear to impair performance on tasks that are designed to assess higher cortical functioning.

Adult↗

PubMedDate not supplied

A G.R.E.A.T. (guest relations emphasis all the time) idea. Guest relations program emphasizes a patient-based mission.

Healthcare, in spite of its tremendous clinical, technological, and financial pressures, is patient based. Guest relations programs seek to remind clinicians, technicians, and financial officers of that fact. St. Joseph Medical Center, Fort Wayne, IN, is striving to combine its mission-driven philosophy of healthcare with responsible competitive strategies, and guest relations is a natural and integral part of the plan. St. Joseph appointed 10 persons to a task force to develop its guest relations project. The task force assigned teams of two members each to concentrate on specific objectives: implementation, policy development, medical staff involvement, existing areas that overlapped with the new guest relations efforts, and evaluation. The task force chose 10 persons outside the education department to train 1,400 associates in 65 sessions over three shifts in three months. An outside consultant trained the trainers on the same day she addressed the management team on the importance of their ownership and involvement in the program. While the task force worked on operational details, the advisory group on policy development began laying the groundwork for what may be the most valuable part of any guest relations program: administration-approved policy and procedures, which address communication, standards of excellence, human relations skills, and positive personal attitudes.

Hospital Bed Capacity, 300 to 499↗

PubMed2006

Cortical activity in Parkinson's disease during executive processing depends on striatal involvement.

Patients with idiopathic Parkinson's disease exhibit impairments in executive processes, including planning and set-shifting, even at the early stages of the disease. We have recently developed a new card-sorting task to study the specific role of the caudate nucleus in such executive processes and have shown, using functional magnetic resonance imaging (fMRI) in young healthy adults, that the caudate nucleus is specifically required when a set-shift must be planned. Here the same fMRI protocol was used to compare the patterns of activation in a group of early-stage Parkinson's disease patients (seven right-handed patients at Hoehn and Yahr stages 1 and 2; mean age 62 years, range 56-70) and matched control subjects. Increased cortical activation was observed in the patients compared with the control group in the condition not specifically requiring the caudate nucleus. On the other hand, decreased cortical activation was observed in the patient group in the condition significantly involving the caudate nucleus. This event-related fMRI study showed a pattern of cortical activation in Parkinson's disease characterized by either reduced or increased activation depending on whether the caudate nucleus was involved or not in the task. This activation pattern included not only the prefrontal regions but also posterior cortical areas in the parietal and prestriate cortex. These findings are not in agreement with the traditional model, which proposes that the nigrostriatal dopamine depletion results in decreased cortical activity. These observations provide further evidence in favour of the hypothesis that not only the nigrostriatal and but also the mesocortical dopaminergic substrate may play a significant role in the cognitive deficits observed in Parkinson's disease.

Aged↗

PubMed2005

Functional neuroanatomy of anticipatory behavior: dissociation between sensory-driven and memory-driven systems.

The ability to anticipate predictable stimuli allows faster responses. The predictive saccade (PRED) task has been shown to quickly induce such anticipatory behavior in humans. In a PRED task subjects track a visual target jumping back and forth between fixed positions at a fixed time interval. During this task, saccade latencies drop from approximately 200 ms to <80 ms as subjects anticipate target appearance. This change in saccade latency indicates that subjects' behavior shifts from being sensory driven to being memory driven. We conducted functional magnetic resonance imaging studies with 10 healthy adults performing the PRED task using a standard block design. We compared the PRED task with a visually guided saccade (VGS) task using unpredictable targets matched for number, direction and amplitude of required saccades. Our results show greater activation during the PRED task in the prefrontal, pre-supplementary motor and anterior cingulate cortices, hippocampus, mediodorsal thalamus, striatum and cerebellum. The VGS task elicited greater activation in the cortical eye fields and occipital cortex. These results demonstrate the important dissociation between sensory and predictive neural control of similar saccadic eye movements. Anticipatory behavior induced by the PRED task required less sensory-related processing activity and was subserved by a distributed cortico-subcortical memory system including prefronto-striatal circuitry.

Adult↗

PubMed1997

An artificial life approach to language.

The aim of the paper is to show that an Artificial Life approach to language tends to change the research agenda on language which has been shared by both the symbolic paradigm and classical connectionism. Artificial Life Neural Networks (ALNNs) are different from classical connectionist networks because they interact with an independent physical environment; are subject to evolutionary, developmental, and cultural change, and not only to learning; and are part of organisms that have a physical body, have a life (are born, develop, and die), and are members of genetic and sometimes, cultural populations. Using ALNNs to study language shifts the emphasis from research on linguistic forms and laboratory-like tasks to the investigation of the emergence and transmission of language, the use of language, its role in cognition, and language as a populational rather than as an individual phenomenon.

Animal Communication↗

PubMedDate not supplied

Reflections on the U.S. Preventive Services Task Force recommendations for screening for hypertension and hypercholesterolemia.

The U.S. Preventive Services Task Force recommendations for screening for hypertension and high blood cholesterol are generally consistent with preexisting national guidelines promulgated by the Joint National Committee for Detection, Evaluation, and Treatment of High Blood Pressure and the National Cholesterol Education Program Expert Panel on Detection, Evaluation, and Treatment of High Cholesterol in Adults. While a welcome addition to the armamentarium of the clinician, the Task Force recommendations represent only a partial solution to our current epidemic of blood-pressure- and cholesterol-related cardiovascular disease. A meaningful reduction in society's burden of cardiovascular disease can be achieved only by complementing the Task Force recommendations with community-based mass treatment strategies aimed at shifting the distribution of blood pressure and cholesterol toward a biologically more normal pattern.

Blood Pressure Determination↗

PubMed1992

Saccade programming during short duration fixations: an examination of copy typing, letter detection, and reading.

Three experiments examined saccade programming during short duration fixations between 50 ms and 150 ms. In experiment 1, subjects copy typed text, in experiment 2, subjects read and executed a letter detection task, and in experiment 3, subjects read for comprehension only. Fixation duration had no effect on the size of the departing saccade in the copy typing task; however, saccades leaving short duration fixations were larger than saccades leaving all other fixation durations in the letter detection task and smaller than saccades leaving long fixation durations in the standard reading task. Within Morrison's (1984) model, these results imply, first, that consecutive shifts of attention during a fixation can take different directions and, second, that successive shifts of attention during a fixation support different purposes. Within Fischer's (1986, in press) model, the results imply that the engagement/disengagement of attention and saccade programming do not constitute independent events.

Adult↗

PubMed1985

Lateralized rewarding brain stimulation affects forepaw preference in rats.

Rats trained to reach for food pellets into a narrow tubular feeder consistently prefer to perform this stereotype instrumental movement with either the left or right forepaw. In 16 rats with established handedness electrodes were implanted into both lateral hypothalami. The animals were rewarded by intracranial self stimulation (ICSS, 300 msec, 50 Hz, 20-60 microA) for reaching into a modified feeder for a plastic ball operandum, the movement of which between the bottom and entrance of the feeder was monitored by mechanical contacts. The rats readily continued to reach when ICSS was delivered immediately after the photoelectrically detected reach or after the displacement of the operandum. Most rats learned in a single session to modify the movement when ICSS delivery was made contingent upon holding the operandum between the bottom and entrance of the feeder for 256 or 512 msec. The efficiency of reaching (ratio of successful reaches to all reaches) decreased with increasing holding time; only a few animals were able to master a 1024 msec delay. Reaching was supported by ICSS of either lateral hypothalamus. Whereas in 8 rats the strongly expressed forepaw preference was not changed by lateralized ICSS, in 8 latently ambidextrous animals stimulation of the lateral hypothalamus ipsilateral to the preferred forepaw increased reaching with the normally non-preferred forepaw from 15% to 60%. Stimulation of the lateral hypothalamus contralateral to the preferred forepaw did not change the preference. The preference shift was equally well expressed in simple and difficult versions of the task. It is concluded that lateralization of motivational influences can be reflected in the asymmetry of the neural mechanisms processing the lateralized sensory signals and/or elaborating the lateralized motor output.

Animals↗

PubMed1993

Different effects of nucleus accumbens and ventrolateral striatal dopamine depletions on instrumental response selection in the rat.

This experiment was undertaken to investigate dopaminergic involvement in food-related instrumental behavior. Rats were tested in an operant chamber in which there was a choice between pressing a lever to receive a preferred food (Bioserve pellets) or feeding upon a less preferred food (lab chow). The lever-pressing schedule was a fixed ratio 5 (FR5). Rats usually pressed the lever at high rates to obtain the preferred food, and typically ate little of the lab chow even though it was freely available in the chamber concurrently with the lever-pressing schedule. The neurotoxic agent 6-hydroxydopamine was injected directly into the nucleus accumbens, medial striatum, or ventrolateral striatum to determine the effects of dopamine depletion on the performance of this task. Depletion of dopamine in the nucleus accumbens led to a dramatic shift in behavior in which there was a significant decrease in lever pressing but a significant increase in consumption of lab chow. The shift away from lever pressing and towards chow consumption in rats with accumbens DA depletions was significantly correlated with a decrease in spontaneous locomotor activity. Dopamine depletions in the medial striatum did not significantly affect lever pressing or chow consumption. Ventrolateral striatal dopamine depletions decreased lever pressing but also tended to reduce consumption of lab chow. Rats with ventrolateral striatal dopamine depletions also showed profound deficits in home-cage feeding, and these rats had to receive wet mash or tube feeding to maintain body weight.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗